阅读说明：本技术 金属硼氧酸盐修饰锂离子电池电极复合材料及其制备方法 (Metal borate modified lithium ion battery electrode composite material and preparation method thereof ) 是由 黄富强 董武杰 赵延涛 于 2019-11-27 设计创作，主要内容包括：本发明公开金属硼氧酸盐修饰锂离子电池电极复合材料及其制备方法。所述金属硼氧酸盐修饰的锂离子电池电极复合材料,包括金属硼氧酸盐和锂离子电池电极材料,所述锂离子电池电极材料为锂离子电池正极材料或锂离子电池负极材料；所述电极复合材料中金属硼氧酸盐的质量比例为0.1%-30%；所述金属硼氧酸盐通式为A-xB-yOz,其中A为金属元素Li、Na、K、Mg、Ca、Al、Sr、La、Ti、Zr、Nb、Fe中的一种或多种,0<x<10,0<y<10,0<z<10。(The invention discloses a metal borate modified lithium ion battery electrode composite material and a preparation method thereof. The lithium ion battery electrode composite material modified by the metal borate comprises the metal borate and a lithium ion battery electrode material, wherein the lithium ion battery electrode material is a lithium ion battery anode material or a lithium ion battery cathode material; the mass ratio of the metal borate in the electrode composite material is 0.1-30%; the general formula of the metal borate is A x B y Oz, wherein A is a metal element Li, Na, K, Mg, Ca, Al, Sr, La, Ti, Zr,One or more of Nb and Fe, 0<x<10，0<y<10，0<z<10。)

1. The lithium ion battery electrode composite material modified by the metal borate is characterized by comprising the metal borate and a lithium ion battery electrode material, wherein the lithium ion battery electrode material is a lithium ion battery anode material or a lithium ion battery cathode material; the mass ratio of the metal borate in the electrode composite material is 0.1-30%, preferably 5-20%; the general formula of the metal borate is A_xB_yOz, wherein A is one or more of metal elements Li, Na, K, Mg, Ca, Al, Sr, La, Ti, Zr, Nb and Fe, and 0<x<10, preferably 1. ltoreq. x<4，0<y<10, preferably 1. ltoreq. y. ltoreq.3, 0<z<10, preferably 2. ltoreq. z.ltoreq.6; more preferably, A is one or more of alkali metal elements Li, Na and K.

2. The electrode composite of claim 1, wherein the lithium ion battery positive electrode material comprises at least one of lithium cobaltate, lithium iron phosphate, a ternary positive electrode material, lithium manganate, and a lithium rich manganese based material, preferably lithium cobaltate.

3. The electrode composite of claim 1, wherein the lithium ion battery negative electrode material comprises at least one of a carbon material, metallic lithium, a silicon carbon material, a silica-carbon material, a metal oxide, an alloy material; the carbon material comprises at least one of natural graphite, hard carbon, soft carbon and heteroatom-doped carbon; the metal oxide comprises at least one of ferric oxide, ferroferric oxide, zinc oxide, antimony oxide, copper oxide, tin dioxide and nickel oxide; the alloy material comprises at least two of Si, Sn and Ge; preferably, the lithium ion battery negative electrode material is ferric oxide.

4. The method of preparing a metal borate modified lithium ion battery electrode composite of any of claims 1-3, wherein the method of preparation comprises a co-precipitation method, an impregnation method, a mechanical mixing method, a hydrothermal method, a ball milling method, and a solid phase method, preferably a co-precipitation method.

5. The preparation method of claim 4, wherein the method for preparing the metal borate modified lithium ion battery cathode composite material by using a coprecipitation method comprises the following steps:

(1) dispersing the lithium ion battery anode material in water to prepare an anode material dispersion liquid with the molar concentration of 10-100 g/L;

(2) dissolving metal borate in water to prepare a metal borate aqueous solution with the molar concentration of 0.1-2 mol/L;

(3) adding a metal borate aqueous solution into the dispersion liquid of the positive electrode material, adsorbing the borate ions with negative charges to the surface of the positive electrode material with positive charges by virtue of electrostatic adsorption, filtering and drying to form the metal borate modified lithium ion battery positive electrode composite material.

6. The preparation method of claim 4, wherein the method for preparing the metal borate modified lithium ion battery anode composite material by using the coprecipitation method comprises the following steps:

(1) dissolving precursor salt of the metal oxide negative electrode material in water to prepare precursor salt dispersion liquid with the molar concentration of 0.1-2 mol/L;

(2) adding the precursor salt dispersion liquid into boiling water, or adding alkali liquor into the precursor salt dispersion liquid, and then stirring and aging to form dispersion liquid containing metal hydroxide colloid;

(3) dissolving metal borate in water to prepare a metal borate aqueous solution with the molar concentration of 0.1-2 mol/L;

(4) adding a metal borate aqueous solution into a dispersion liquid containing a metal hydroxide colloid, adsorbing borate on the surface of the metal hydroxide colloid by virtue of electrostatic adsorption, filtering and drying to form the metal borate modified lithium ion battery cathode composite material.

7. The preparation method according to claim 6, wherein the precursor salt of the metal oxide negative electrode material comprises at least one of ferric chloride, nickel chloride, tin chloride, zinc chloride, copper chloride and antimony chloride.

8. The method of claim 5 or 6, wherein the metal borate is an alkali metal borate comprising LiBO₂、Li₃BO₃、Li₂B₄O₇、Li₆B₄O₉、NaBO₂、KBO₂At least one of them.

9. The preparation method according to any one of claims 4 to 8, wherein the preparation method of the composite material further comprises a step of heat treatment, wherein the heat treatment temperature is in a range of 300 ℃ to 800 ℃, the heat treatment atmosphere is one or more of air, nitrogen, argon and oxygen, and the heat treatment time is 0.5 hours to 8 hours; preferably, the heat treatment is performed for 4 hours at 500 ℃ in an argon atmosphere.

Technical Field

The invention relates to a metal borate modified lithium ion battery electrode composite material and a preparation method and application thereof, in particular to a composite material which is compounded with metal borate and some lithium ion battery anode and cathode materials so that the performance of the composite material serving as the lithium ion battery anode and cathode materials is obviously improved in certain aspects, and belongs to the field of materials.

Background

Compared with other energy storage devices, such as a super capacitor, a lead-acid battery, a Ni-Cd battery, a nickel-hydrogen battery and the like, the lithium ion battery has obvious advantages in the aspects of energy density, power density and the like as the most widely applied energy storage technology at present. And the working voltage of the lithium ion battery is higher (>3.6V), light weight, good cycling stability, high energy efficiency, wide working temperature range (-30 ℃ to +45 ℃), small self-discharge, no memory effect and the like. Since the Sony corporation commercialized the first time in 1991, most other energy storage devices are rapidly replaced by the lithium ion battery to be integrated into the aspects of production and life of people, and the lithium ion battery is used as a power supply in various mobile electronic equipment mobile phones, notebook computers and electric automobiles, and also can be used as a large-scale energy storage device to realize power grid peak shaving, so that the lithium ion battery becomes an indispensible necessity. Lithium ion batteries rely on the movement of lithium ions between a positive electrode and a negative electrode to store energy. In the charge and discharge process of a typical lithium ion battery, lithium ions are continuously inserted and extracted between a positive electrode and a negative electrode to complete the conversion between electric energy and chemical energy. In addition to optimizing and improving the battery technology and the battery management system, the most essential way to improve the performance of the lithium battery is to realize the breakthrough of the performance of the lithium battery by improving the performance of the positive and negative electrode materials. The key core materials of the lithium ion battery are the anode material and the cathode material of the lithium ion battery, and the movement of lithium ions between the anode material and the cathode material forms the basic working principle of the lithium ion battery for storing and releasing electric energy. Increasingly severe energy crisis puts higher requirements on energy storage devices, high-performance lithium ion battery cathode materials are research hotspots in the research field of energy storage materials, however, application bottlenecks such as short service life, low capacity, low multiplying power difference and low tap density are urgent to develop and are suitable for large-scale production and applicationNovel high-performance long-life lithium battery anode and cathode materials. The currently commercially available positive electrode material mainly has laminated-structure LiCoO₂、LiMnO₂、Li₂MnO₃Ternary material Li (NixCoyMn1-x-y) O₂And olivine-structured LiFePO₄And the like. LiCoO₂The theoretical capacity is high, but the structural breakdown cycle performance is poor under high voltage; ternary positive electrode materials, particularly high nickel materials, have high capacity, but are easy to generate thermal runaway and poor in safety; the lithium iron phosphate has high stability but lower capacity and voltage platform, and the improvement of the energy density of the lithium ion battery is influenced. Commercial cathode materials such as the traditional graphite cathode have low theoretical capacity, high-capacity metallic lithium has serious potential safety hazard, the alloy type simple substance silicon cathode has extremely high theoretical capacity, but the rapid capacity attenuation is caused by the huge volume change in the lithium insertion and extraction process, the problems of capacity, tap density, multiplying power, cycle life and the like of the Si/C composite material obtained by large-scale production still exist, the energy density of the embedded lithium battery cathode is lower although the embedded lithium battery cathode has the advantages of high power, long service life and the like, the conversion type (such as iron oxide) and conversion-alloy composite type (such as tin dioxide) metal oxide negative electrode materials have the advantages of high theoretical specific capacity, rich reserves, low price and the like, so that the conversion type (such as iron oxide) and conversion-alloy composite type (such as tin dioxide) metal oxide negative electrode materials are widely concerned and researched by people, but the problems of poor cycle performance, rate capability and the like of the conversion type and the conversion-alloy composite type are not solved all the time. Therefore, by deeply researching the internal mechanism of the performance influence of the anode and cathode materials of the lithium ion battery, guidance can be provided for rational design of the materials, and the development of the anode and cathode materials of the lithium ion battery with high performance and long service life has important significance. On the basis, the development of a simple, mild and low-cost synthetic method suitable for large-scale production has important value for practical application. Through similar research ideas and strategies, the development of novel high-performance lithium ion battery anode and cathode composite materials through the old inertial thinking is broken through, and the novel high-performance lithium ion battery anode and cathode composite materials have important reference and guidance significance for the further development of future lithium ion battery anode materials.

The problems of insufficient cycle stability, poor rate performance, poor safety and the like faced by the conventional lithium ion battery anode and cathode materials are fundamentally in the characteristics of the electrode materials and the electrode structure, for example, the crystal structure of the anode material is easy to collapse during deep charging and discharging; the volume change of the cathode material is huge in the electrochemical reaction process, and the generated stress causes the breakage of the electrode; the problems of poor electronic and ionic conductivity of the anode and cathode materials and the like cause the electrochemical reaction of the anode and cathode materials to be insufficient in the rapid charge and discharge process, and the capacity cannot be fully exerted, so that the rate performance is poor; the electrolyte is not fully infiltrated due to the accumulation of particles in the electrode, and the rapid migration and diffusion of lithium ions cannot be realized; and the safety risk of the lithium ion battery is obviously improved due to the problems of battery short circuit, thermal runaway and the like caused by contact reaction of the cathode lithium dendrite and the anode material with the electrolyte.

Disclosure of Invention

Aiming at the problems, the invention aims to provide a lithium ion battery electrode composite material modified by metal borate and a preparation method thereof.

In a first aspect, the invention provides a lithium ion battery electrode composite material modified by metal borate, which comprises metal borate and a lithium ion battery electrode material, wherein the lithium ion battery electrode material is a lithium ion battery anode material or a lithium ion battery cathode material; the mass ratio of the metal borate in the electrode composite material is 0.1-30%, preferably 5-20%; the general formula of the metal borate is A_xB_yOz, wherein A is one or more of metal elements Li, Na, K, Mg, Ca, Al, Sr, La, Ti, Zr, Nb and Fe, and 0<x<10, preferably 1. ltoreq. x<4，0<y<10, preferably 1. ltoreq. y. ltoreq.3, 0<z<10, preferably 2. ltoreq. z.ltoreq.6; more preferably, A is one or more of alkali metal elements Li, Na and K.

Preferably, the lithium ion battery positive electrode material comprises at least one of lithium cobaltate, lithium iron phosphate, a ternary positive electrode material, lithium manganate and a lithium-rich manganese-based material, and is preferably lithium cobaltate.

Preferably, the lithium ion battery negative electrode material comprises at least one of a carbon material, metallic lithium, a silicon carbon material, a silicon oxide-carbon material, a metal oxide and an alloy material; the carbon material comprises at least one of natural graphite, hard carbon, soft carbon and heteroatom-doped carbon; the metal oxide comprises at least one of ferric oxide, ferroferric oxide, zinc oxide, antimony oxide, copper oxide, tin dioxide and nickel oxide; the alloy material comprises at least two of Si, Sn and Ge; preferably, the lithium ion battery negative electrode material is ferric oxide.

In a second aspect, the invention also provides a preparation method of the lithium ion battery electrode composite material modified by the metal borate. The preparation method comprises a coprecipitation method, an impregnation method, a mechanical mixing method, a hydrothermal method, a ball milling method and a solid phase method, and the coprecipitation method is preferred.

Preferably, the method for preparing the metal borate modified lithium ion battery anode composite material by using a coprecipitation method comprises the following steps:

(1) dispersing the lithium ion battery anode material in water to prepare an anode material dispersion liquid with the molar concentration of 10-100 g/L;

(2) dissolving metal borate in water to prepare a metal borate aqueous solution with the molar concentration of 0.1-2 mol/L;

(3) adding a metal borate aqueous solution into the dispersion liquid of the positive electrode material, adsorbing the borate ions with negative charges to the surface of the positive electrode material with positive charges by virtue of electrostatic adsorption, filtering and drying to form the metal borate modified lithium ion battery positive electrode composite material.

Preferably, the method for preparing the metal borate modified lithium ion battery cathode composite material by using a coprecipitation method comprises the following steps:

(1) dissolving precursor salt of the metal oxide negative electrode material in water to prepare precursor salt dispersion liquid with the molar concentration of 0.1-2 mol/L;

(2) adding the precursor salt dispersion liquid into boiling water, or adding alkali liquor into the precursor salt dispersion liquid, and then stirring and aging to form dispersion liquid containing metal hydroxide colloid;

(3) dissolving metal borate in water to prepare a metal borate aqueous solution with the molar concentration of 0.1-2 mol/L;

(4) adding a metal borate aqueous solution into a dispersion liquid containing a metal hydroxide colloid, adsorbing borate on the surface of the metal hydroxide colloid by virtue of electrostatic adsorption, filtering and drying to form the metal borate modified lithium ion battery cathode composite material.

Preferably, the precursor salt of the metal oxide negative electrode material comprises at least one of ferric chloride, nickel chloride, stannic chloride, zinc chloride, copper chloride and antimony chloride.

Preferably, the metal borate is an alkali metal borate, including LiBO₂、Li₃BO₃、Li₂B₄O₇、Li₆B₄O₉、NaBO₂、KBO₂At least one of them.

Preferably, the preparation method of the composite material further comprises a heat treatment step, wherein the heat treatment temperature ranges from 300 ℃ to 800 ℃, the heat treatment atmosphere is one or more of air, nitrogen, argon and oxygen, and the heat treatment time is 0.5 hours to 8 hours; preferably, the heat treatment is performed for 4 hours at 500 ℃ in an argon atmosphere.

In a third aspect, the invention also provides a method for improving the performance of the lithium ion battery electrode material, which comprises coating the surface of the lithium ion battery electrode material with metal borate by adopting a coprecipitation method, a dipping method, a mechanical mixing method, a hydrothermal method, a ball milling method or a solid phase method; the performance includes one or more of cycle life, rate capability, coulombic efficiency and material specific mass capacity.

Drawings

FIG. 1 shows amorphous lithium metaborate (LiBO) prepared according to example 1 of the present invention₂) And (3) a transmission electron microscope photo of the modified iron oxide cathode, wherein a picture A is a transmission electron microscope and a selected area electron diffraction photo of the iron oxide cathode, and a picture B is a high-resolution transmission electron microscope photo of the iron oxide cathode.

Fig. 2 shows a transmission electron micrograph of an iron oxide anode without modification with a metal borate prepared according to comparative example 1 of the present invention, in which fig. a is a transmission electron micrograph of an iron oxide anode without modification with a metal borate, and fig. B is a high-resolution transmission electron micrograph of an iron oxide anode without modification with a metal borate.

Fig. 3 shows a scanning electron micrograph of a metal borate-modified iron oxide negative electrode prepared according to example 1 of the present invention, in which fig. a is a scanning electron micrograph at a scale of 80 μm and fig. B is a scanning electron micrograph at a scale of 10 μm.

FIG. 4 shows amorphous lithium metaborate (LiBO) prepared according to example 1 of the present invention₂) Powder X-ray diffraction patterns of the modified iron oxide and the iron oxide prepared in comparative example 1 without modification with metal borate.

Fig. 5 shows nitrogen adsorption desorption isotherms for metal borate modified iron oxide prepared according to example 1 of the present invention and iron oxide without metal borate modification prepared according to comparative example 1.

Fig. 6 shows a test ac impedance spectrum of the metal borate-modified iron oxide prepared according to example 1 of the present invention.

Fig. 7 shows a graph of cycling performance data for the metal borate modified iron oxide prepared according to example 1 of the present invention and the iron oxide without the metal borate modification prepared in comparative example 1 as a negative electrode of a lithium battery.

Fig. 8 shows a graph of rate performance data for metal borate modified iron oxide prepared according to example 1 of the present invention and for iron oxide without metal borate modification prepared according to comparative example 1 as negative electrodes of lithium batteries.

FIG. 9 shows amorphous lithium metaborate (LiBO) prepared according to example 14 of the present invention₂) The transmission electron microscope photo of the modified lithium cobaltate anode is shown in the figure A, wherein the transmission electron microscope photo of the lithium cobaltate anode ruler modified by the metal borate is 50nm, and the transmission electron microscope photo of the lithium cobaltate anode ruler modified by the metal borate is 10 nm.

Fig. 10 shows a transmission electron micrograph of a lithium cobaltate positive electrode without modification with a metal borate according to comparative example 2 of the present invention, in which fig. a is a transmission electron micrograph of a lithium cobaltate positive electrode without modification with a metal borate at a scale of 50nm, and fig. B is a transmission electron micrograph of a lithium cobaltate positive electrode without modification with a metal borate at a scale of 20 nm.

FIG. 11 shows embodiment 14 according to the present inventionPrepared amorphous lithium metaborate (LiBO)₂) Powder X-ray diffraction patterns of the modified iron oxide and the lithium cobaltate prepared in comparative example 2 without modification with metal borate.

Fig. 12 shows a test ac impedance spectrum of a lithium cobaltate modified with a metal borate prepared according to example 14 of the present invention.

Fig. 13 shows cycling performance data for lithium cobaltate modified with a metal borate prepared according to example 14 of the present invention and without a metal borate modification prepared according to comparative example 2 as a lithium battery positive electrode over a voltage range of 3V to 4.6V.

Fig. 14 shows rate performance data for lithium cobaltate modified with a metal borate prepared according to example 14 of the present invention and without a metal borate modification prepared according to comparative example 2 as a lithium battery positive electrode in a voltage range of 3V to 4.6V.

FIG. 15 is a flow chart illustrating the preparation of an exemplary embodiment of the present invention.

Detailed Description

The present invention will be described in further detail with reference to examples. It should be noted that the present invention is not limited to these specific embodiments. Equivalent alterations and modifications may be effected by those skilled in the art without departing from the background and spirit of the invention, and the content thereof is also intended to be covered by the appended claims. In the case where the present invention is not specifically described, "metal hydroxide colloid" may also be referred to as "metal hydroxide precipitate" and "borate" may also be referred to as "metal borate".

The present disclosure provides a lithium ion battery electrode composite material modified by metal borate, which includes metal borate and a lithium ion battery electrode material. The metal borate AxByOz is a common stable compound, and part of substances in the metal borate have high lithium ion conductivity. Wherein, the metal borate A_xB_yIn the general formula of Oz, A is one or more of metal elements Li, Na, K, Mg, Ca, Al, Sr, La, Ti, Zr, Nb and Fe, and 0<x<10, preferably 1. ltoreq. x<4，0<y<10, preferably 1. ltoreq. y. ltoreq.3, 0<z<10, preferably 2. ltoreq. z.ltoreq.6.Further preferably, A is one or more of alkali metals Li, Na and K. The alkali metal borate includes, but is not limited to, LiBO₂、Li₃BO₃、Li₂B₄O₇、Li₆B₄O₉、NaBO₂、KBO₂At least one of them.

According to the invention, by controlling the mass ratio of the metal borate in the composite material to be 0.1-30% and regulating and controlling experimental conditions, the performance of the composite material as the positive and negative electrode materials of the lithium ion battery, such as one or more of cycle life, coulombic efficiency, rate capability and material mass specific capacity, can be improved, and the method is a brand new effective method for improving the performance of the positive and negative electrode materials of the lithium ion battery. In some embodiments, the mass ratio of the metal borate in the composite material is 5-20%, preferably 15%.

The metal borate A_xB_yOz may be a commercially available product directly purchased or may be prepared by mixing a compound of the metal element a with a boron oxide.

The above-mentioned metal borate A_xB_yOz can be crystalline or amorphous. Preferably, A is_xB_yOz is amorphous. Because amorphous materials are isotropic, stress is better relieved and ion transport is faster therein.

The invention uses metal borate A_xB_yOz is compounded with the positive and negative electrode materials of the lithium ion battery by methods such as a coprecipitation method, an impregnation method, a mechanical mixing method, a hydrothermal method, a ball milling method, a solid phase method and the like, so that the high-performance positive electrode composite material of the lithium ion battery with controllable proportion of the metal borate is obtained. Specific attempts to use lithium ion battery positive electrode materials include lithium cobaltate (LiCoO)₂) Lithium iron phosphate (LiFePO)₄) Ternary positive electrode materials (NCM and NCA), and lithium manganate (LiMn)₂O₄) And lithium-rich manganese-based material (Li)₂MnO₃) Etc.; lithium ion battery cathode material the lithium ion battery cathode material comprises carbon materials (including natural graphite, hard carbon, soft carbon, heteroatom-doped carbon and the like), metal lithium, silicon carbon materials and silicon monoxide-carbon materialsMetal oxides (including iron sesquioxide, iron tetroxide, zinc oxide, antimony oxide, copper oxide, tin dioxide, nickel oxide, etc.), alloy materials (including Si, Sn, Ge, etc.). The invention is characterized in that the invention discloses that the metal borate modified lithium ion battery electrode composite material is prepared by a coprecipitation method, wherein the metal borate modified lithium ion battery electrode composite material is simultaneously suitable for the anode and cathode materials of the lithium battery for the first time.

When the same positive and negative electrode materials and the same metal boron oxide are used, compared with other methods such as a ball milling method and a mechanical mixing method, the composite material prepared by the coprecipitation method has higher initial capacity and capacity retention rate (namely, cycling stability) after the lithium battery is cycled for multiple times. The reason is that the metal borate is dispersed in atomic level during the preparation process by the coprecipitation method, the uniformity and consistency of the subsequent surface modification coating are good, and the metal borate prepared by other methods such as the ball milling method, the mechanical mixing method and the like is not uniformly distributed on the surfaces of the anode and cathode materials, so that the performance difference is caused.

In some embodiments, the method for preparing the metal borate modified lithium ion battery cathode composite material by using the coprecipitation method comprises the following steps:

(1) dispersing the lithium ion battery anode material in water to prepare an anode material dispersion liquid with the molar concentration of 10-100 g/L; lithium ion battery positive electrode materials include, but are not limited to, lithium cobaltate (LiCoO)₂) Lithium iron phosphate (LiFePO)₄) Ternary positive electrode materials (NCM and NCA), and lithium manganate (LiMn)₂O₄) And lithium-rich manganese-based material (Li)₂MnO₃) Etc., preferably lithium cobaltate;

(2) dissolving metal borate in water to prepare a metal borate aqueous solution with the molar concentration of 0.1-2 mol/L;

(3) adding a metal borate aqueous solution into the dispersion liquid of the positive electrode material, adsorbing the borate ions with negative charges to the surface of the positive electrode material with positive charges by virtue of electrostatic adsorption, filtering and drying to form the metal borate modified lithium ion battery positive electrode composite material.

In some embodiments, the method for preparing the metal borate modified lithium ion battery anode composite material by using the coprecipitation method comprises the following steps:

(1) dissolving precursor salt of the metal oxide negative electrode material in water to prepare precursor salt dispersion liquid with the molar concentration of 0.1-2 mol/L; the precursor salt of the metal oxide negative electrode material comprises at least one of ferric chloride, nickel chloride, stannic chloride, zinc chloride, copper chloride and antimony chloride;

(2) adding the precursor salt dispersion liquid into boiling water, or adding alkali liquor into the precursor salt dispersion liquid, stirring and aging to form dispersion liquid containing metal hydroxide colloid, preferably, the alkali liquor is concentrated ammonia water with the mass fraction of 20-30%, and the volume ratio of the precursor salt dispersion liquid to the concentrated ammonia water is 100: 1-100: 10;

(3) dissolving metal borate in water to prepare a metal borate aqueous solution with the molar concentration of 0.1-2 mol/L;

(4) adding a metal borate aqueous solution into a dispersion liquid containing a metal hydroxide colloid, adsorbing borate on the surface of the metal hydroxide colloid by virtue of electrostatic adsorption, filtering and drying to form the metal borate modified lithium ion battery cathode composite material.

In experiments, the effect of the coprecipitation method on the cathode material is found to be better than that of the anode material. The coprecipitation method used in the invention needs an electrostatic adsorption principle on one hand, and the action mechanism is obvious in the metal oxide cathode and is easy to realize. The effect is not significant in the positive electrode material, and thus the effect is poor. On the other hand, the fundamental reasons for the poor performance of the metal oxide anode material are the electrochemical reaction non-uniformity due to its low electron/ion conductivity and the volume expansion problem during the electrochemical reaction. The metal borate modified coating can reduce the interface impedance among metal oxide cathode material particles and enhance ion transmission, and the coating layer can be used as a buffer layer to relieve the internal stress of the electrode caused by volume expansion, so that the improvement on the cathode, especially the metal oxide cathode is very obvious. The failure of the anode material mainly comprises material breakage caused by internal stress in particles and collapse of a crystal structure of the material, the coating of the metal borate can only relieve the side reaction of the anode material and electrolyte, and the effects of material structure collapse and particle internal stress breakage are not obvious. Thus, the effect of the coprecipitation method on the anode material is better than that of the cathode material.

In the above production method, the borate is preferably an alkali metal borate. The borate includes, but is not limited to LiBO₂、Li₃BO₃、Li₂B₄O₇、Li₆B₄O₉、NaBO₂、KBO₂At least one of them. The borate is most preferably LiBO₂. This is due to LiBO₂The water solubility is good, the lithium content is moderate, and the generated boric oxide radical is stable.

The most preferable positive electrode material for the composite material is lithium cobaltate (LiCoO)₂) (ii) a The anode material is most preferably iron trioxide. The lithium cobaltate has large theoretical capacity and wide practical application, and the performance is improved most obviously after the lithium cobaltate is modified by the metal borate; the iron oxide has large theoretical capacity, is cheap and easy to obtain, has small volume expansion in the electrochemical reaction process, and has the most obvious performance improvement after being modified by the metal borate.

In addition, the preparation method of the composite material also comprises a heat treatment step (namely, the heat treatment is continued after the composite material is prepared). The heat treatment temperature is in the range of 60 ℃ to 1000 ℃, preferably 300 ℃ to 800 ℃. The heat treatment atmosphere is one or more of air, nitrogen, argon and oxygen. The heat treatment time is 10 minutes to 24 hours, preferably 0.5 hours to 8 hours. Further preferably, the heat treatment is a heat treatment at 500 ℃ for 4 hours in an argon atmosphere.

Compared with the prior art, the invention has the following beneficial effects: the metal borate is rich in variety, wherein A is one or more of metal elements such as Li, Na, K, Mg, Ca, Al, Sr, La, Ti, Zr, Nb and Fe, x is more than or equal to 0 and less than 10, y is more than 0 and less than 10, z is more than 0 and less than 10, positive beneficial effects can be generated by controlling the type of the metal borate and experimental conditions, the key point of the method lies in that a metal borate high lithium ion conductivity is utilized to construct a 'highway' for fast response and conduction of lithium ions in an electrode, and structural phase change and volume expansion of an electrode material are inhibited, new mechanisms and new models such as generation of lithium dendrites and direct contact of an anode material and an electrolyte are avoided, finally, the performance improvement of the anode material and the cathode material of the lithium ion battery, including the improvement of one or more of safety, cycle life, coulombic efficiency, rate performance and material mass specific capacity, and the metal borate can be directly obtained or simply synthesized by raw materials, the anode and cathode material can be purchased or prepared by self, so that the cost is low, the mass preparation can be realized, the reaction condition is mild, the lithium ion battery anode and cathode material with obviously improved performance can be obtained under the conditions of inapplicable organic solvent and lower temperature (500 ℃), the energy is saved, the environment is protected, the lithium ion battery anode and cathode material is suitable for industrial mass production, and the lithium ion battery anode and cathode material has the advantages of novel mechanism, good product performance, mild reaction condition, suitability for mass production and the like.

The principle of the coprecipitation method is that positive charges on the surface of electrode material particles and boron oxygen radical ions with negative charges generated by ionization and hydrolysis of metal borate are quickly and uniformly adsorbed through classical interaction. In the prior art, the preparation method of the common positive electrode composite material is to dissolve and coat boric acid, on one hand, the used raw materials are different, and on the other hand, the coating modification process only involves physical mixing and is unrelated to electrostatic interaction and poor in uniformity and consistency. The coating layer of the metal borate prepared by the method is more uniform. In addition, the metal borate in the composite material is in an amorphous structure and has higher ionic conductivity. The key point of the method is to utilize the borate high lithium ion conductivity to construct a 'highway' for the rapid response and conduction of lithium ions in the electrode, inhibit the structural phase change and the volume expansion of the electrode material, and avoid the generation of lithium dendrite and the direct contact between the anode material and electrolyte and other new mechanisms and new models.

In addition, the principle of the coprecipitation method is that positive charges on the surfaces of electrode material particles and boron oxygen radical ions with negative charges generated by ionization and hydrolysis of the metal borate are rapidly and uniformly adsorbed through classical interaction, so that the prepared metal borate coating layer is more uniform and consistent, the coating layer is a high-ion conductivity amorphous layer and has an important effect of buffering volume expansion, and the method is different from the nonuniform coating of mechanical mixing, granulation and sintering in the comparison document 201810893735. X. Moreover, the composite material also has the appearance of a core-shell structure, wherein the core is a crystalline electrode material, and the shell layer is amorphous metal borate. In some embodiments, the core layer is a core of a crystalline metal oxide and the shell layer is an amorphous lithium metaborate modifying layer. In some embodiments, the core layer is a core of crystalline lithium cobaltate and the shell layer is an amorphous lithium metaborate modifying layer. The core-shell structure has an obvious effect of improving the cycling stability of the positive and negative electrode composite materials, and the specific mechanism is that the metal borate shell layer on the outer surface can avoid the direct contact of the positive and negative electrode materials and the electrolyte, and reduce the surface potential, so that a plurality of side reactions in the electrochemical reaction process are avoided.

The method comprises the steps of collecting morphology and ultrastructural information of a sample by using a transmission electron microscope and a scanning electron microscope, collecting sample structure information by using an X-ray diffractometer, collecting sample hole structure information by using a specific surface area tester, analyzing element composition information of a composite material by using an inductively coupled plasma atomic emission spectrometry (ICP-AES), analyzing information such as chemical composition, element valence state and content of the material by using an X-ray photoelectron spectrometer, and analyzing electrochemical characteristic information of a positive electrode material (a positive electrode such as lithium cobaltate voltage range is 3-4.6V, a negative electrode is 0.01-3V, and charge-discharge current density is 0.1A/g) of a lithium ion battery obtained by using an electrochemical workstation (Shanghai Chenghua 760E) and a battery testing system (Wuhan blue electricity LAND CT 2001A).

Materials, reagents and the like used in the following examples are commercially available unless otherwise specified.

Example 1

2.70g FeCl was weighed₃·6H₂O (0.01mol) was dissolved in 100mL of deionized water, and 6mL of concentrated aqueous ammonia (28%) was added dropwise and stirred overnight. Weighing 2.50g LiBO₂(0.05mol) in 45mL of water, e.g., the incomplete dissolution at room temperature is low and the dissolution can be carried out at about 60 ℃. Mixing LiBO₂The solution is added to the aged Fe (OH) solution₃In the dispersion of (2), since Fe (OH)₃Fe in the solution is easily absorbed in the precipitation process³⁺The ions make the surface thereof positively charged, and LiBO is added₂The borate ions in the solution after the solution are negatively charged, so that part of the borate ions in the solution are adsorbed to Fe (OH) due to the principle of electrostatic adsorption₃The precipitated surface, and then lithium ions are also partially attached to the precipitated surface due to electrostatic adsorption with borate ions, forming an amorphous Li-B-O layer coating Fe (OH)₃The structure of (1) is not washed after the solution is filtered, otherwise most of Li-B-O may be washed out to cause deterioration of the effect. The precipitate was lyophilized for 24 hours and then dried under argon at 500 deg.C (300mL min)^-1) Annealing for 4 hours, wherein in the annealing process, Fe (OH)₃Dehydrated to form FeOx and grow, and an amorphous Li-B-O layer is coated on the outer surface of the FeOx and is possibly partially melted due to the lower melting point of the amorphous Li-B-O layer, so that different FeOx particles are bonded together to form larger secondary particles, and the specific surface area of the product is 8.42m² g^-1Wherein the content of amorphous borate is 18.4 percent measured by ICP-AES, and the initial capacity of the amorphous borate as the negative electrode material of the lithium battery is 800mA h g^-1Has good cycling stability and rate capability, and cycles more than 1000 times, 10A g^-1The capacity of the product under the current density is kept above 90%, and the transmission electron microscope picture, the scanning electron microscope picture, the X-ray powder diffraction, the nitrogen adsorption and desorption isotherm and the electrochemical performance of the product as the negative electrode of the lithium ion battery are shown in figures 1-2 and 7-8.

As can be seen from the transmission electron microscope picture of FIG. 1, the prepared composite material is a mutually agglomerated core with crystalline iron oxide and amorphous lithium metaborate (LiBO)₂) The decorative layer of (2). It can be seen from the scanning electron microscope picture of fig. 3 that the prepared material is iron oxide particles with surface coated and modified metal borate. It can be seen from fig. 4 that both have distinct diffraction peaks for iron oxide, but no associated diffraction peaks for the metal borate, indicating that the metal borate is amorphous. As can be seen from the curve shape of FIG. 5, the polyboronate modified material has fewer voidsSpecific surface area of 8.4m² g^-1. From FIG. 6, it can be calculated that the ionic conductivity of the material can reach 1.4mS cm^-1. It can be seen from the data in fig. 7 that the capacity and cycling stability of the metal borate modified iron oxide negative electrode is greatly enhanced. From the data in fig. 8, it can be seen that the rate capability of the iron oxide negative electrode modified by the metal borate is good.

Example 2

2.70g FeCl was weighed₃·6H₂O (0.01mol) was dissolved in 10mL of deionized water, and 2.50g of LiBO was weighed₂(0.05mol) in 45mL of water, e.g., the incomplete dissolution at room temperature is low and the dissolution can be carried out at about 60 ℃. 100mL of deionized water was measured and heated to boiling on a heating and stirring table, and the concentrated ferric chloride solution was added dropwise to boiling water with a dropper to form Fe (OH)₃Colloid, heating and stirring for 10min, and mixing with LiBO₂The solution is added to the aged Fe (OH) solution₃In the colloid of (2), due to Fe (OH)₃Fe in the solution is easily absorbed in the precipitation process³⁺The ions make the surface thereof positively charged, and LiBO is added₂The borate ions in the solution after the solution are negatively charged, so that part of the borate ions in the solution are adsorbed to Fe (OH) due to the principle of electrostatic adsorption₃The precipitated surface, and then lithium ions are also partially attached to the precipitated surface due to electrostatic adsorption with borate ions, forming an amorphous Li-B-O layer coating Fe (OH)₃The structure of (1) is not washed after the solution is filtered, otherwise most of Li-B-O may be washed out to cause deterioration of the effect. The precipitate was lyophilized for 24 hours and then dried under argon at 500 deg.C (300mL min)^-1) Annealing for 4 hours, wherein in the annealing process, Fe (OH)₃Dehydrated to form FeOx and grow, and an amorphous Li-B-O layer is coated on the outer surface of the FeOx and is possibly partially melted due to the lower melting point of the amorphous Li-B-O layer, so that different FeOx particles are bonded together to form larger secondary particles, and the specific surface area of the product is 7.45m² g^-1The initial capacity of the lithium battery anode material is 900mA h g^-1Has good cycling stability and rate capability, and cycles more than 1000 times, 10A g^-1The capacity is kept above 90% under the current density.

Example 3

Weighing 2.70g NiCl₂·6H₂O was dissolved in 100mL of deionized water, 6mL of concentrated ammonia (28%) was added dropwise and stirred overnight. Weighing 2.50g LiBO₂(0.05mol) in 45mL of water, e.g., the incomplete dissolution at room temperature is low and the dissolution can be carried out at about 60 ℃. Mixing LiBO₂The solution is added to the above aged Ni (OH)₂In the dispersion of (2), due to Ni (OH)₂Ni in the solution is easily absorbed in the precipitation process²⁺The ions make the surface thereof positively charged, and LiBO is added₂The boroxonate ions in the post-solution are negatively charged, so that due to the principle of electrostatic adsorption, part of the boroxonate ions in the solution are adsorbed to Ni (OH)₂The precipitated surface, and then lithium ions are also partially attached to the precipitated surface by electrostatic adsorption with borate ions to form an amorphous Li-B-O layer coated with Ni (OH)₂The structure of (1) is not washed after the solution is filtered, otherwise most of Li-B-O may be washed out to cause deterioration of the effect. The precipitate was lyophilized for 24 hours and then dried under argon at 500 deg.C (300mL min)^-1) Middle annealing for 4 hours, Ni (OH) in the annealing process₂Dehydrated to form NiOx and grow, an amorphous Li-B-O layer coated on the outer surface of NiOx and possibly partially melted due to its lower melting point, binding different NiOx particles together to form larger secondary particles, and the product specific surface area is 10.42m² g^-1The initial capacity of the lithium battery anode material is 920mA h g^-1Has good circulation stability and rate capability, circulates more than 1000 times, 10Ag^-1The capacity is kept above 85% under the current density.

Example 4

2.70g SnCl are weighed out₄·5H₂O was dissolved in 100mL of deionized water, 6mL of concentrated ammonia (28%) was added dropwise and stirred overnight. Weighing 2.50g LiBO₂(0.05mol) in 45mL of water, e.g., the incomplete dissolution at room temperature is low and the dissolution can be carried out at about 60 ℃. Mixing LiBO₂The solution was added to the above aged Sn (OH)₄In the dispersion of (2), due to Sn (OH)₄Sn in the solution is easily adsorbed in the precipitation process⁴⁺The ions make the surface thereof positively charged, and LiBO is added₂The borate ions in the solution after the solution are negatively charged, so that part of the borate ions in the solution are adsorbed to Sn (OH) due to the principle of electrostatic adsorption₄The precipitated surface, and then lithium ions are also partially attached to the precipitated surface due to electrostatic adsorption with borate ions, forming an amorphous Li-B-O layer covering Sn (OH)₄The structure of (1) is not washed after the solution is filtered, otherwise most of Li-B-O may be washed out to cause deterioration of the effect. The precipitate was lyophilized for 24 hours and then dried under argon at 500 deg.C (300mL min)^-1) And medium annealing for 4 hours, wherein the SnOx surface is dehydrated and formed during annealing, an amorphous Li-B-O layer coats the outer surface of the SnOx and is likely to be partially melted due to the lower melting point of the amorphous Li-B-O layer, different SnOx particles are bonded together to form larger secondary particles, and the specific surface area of the product is 7.42m² g^-1The initial capacity of the lithium battery anode material is 1300mA h g^-1Has good cycling stability and rate capability, and 10A g times of cycling for more than 500 times^-1The capacity is kept above 80% under the current density.

Example 5

3g of commercially available Fe was weighed₂O₃Medicine, 0.45g LiBO is added₂Mixing and grinding the mixture in an agate mortar for 30min to obtain crystalline LiBO₂The modified iron oxide composite was dried for 24 hours and then placed under argon atmosphere (300mL min) at 500 deg.C^-1) The specific surface area of the product is 3.49m after the medium annealing for 4 hours² g^-1The initial capacity of the lithium battery anode material is 900mA h g^-1Has good cycling stability and rate capability, and 10A g times of cycling for more than 500 times^-1The capacity is kept above 70% under the current density.

Example 6

3g of the NiO drug purchased was weighed out and 0.45g LiBO was added₂Mixing and grinding the mixture in an agate mortar for 30min to obtain crystalline LiBO₂The modified nickel oxide composite material was dried for 24 hours and then placed under argon atmosphere (300mL min) at 500 deg.C^-1) The specific surface area of the product is 3.49m after the medium annealing for 4 hours² g^-1The initial capacity of the material as a negative electrode material of the lithium battery is 800mA h g^-1Has good circulation stabilitySex and rate capability, cycling more than 600 times, 10A g^-1The capacity is kept above 70% under the current density.

Example 7

3g of the commercially available Si/C negative electrode material was weighed, and 0.45g of LiBO was added₂Mixing and grinding the mixture in an agate mortar for 30min to obtain crystalline LiBO₂The modified silicon-carbon negative electrode composite material is dried for 24 hours and then is put in an argon atmosphere (300mL min) at 500 DEG C^-1) The specific surface area of the product is 20.49m after the annealing for 4 hours² g^-1The initial capacity of the material as a negative electrode material of the lithium battery is 1200mA h g^-1, has good cycling stability and rate capability, and is cycled for more than 1200 times, 10A g^-1The capacity is kept above 70% under the current density.

Example 8

3g of the commercially available Si/C negative electrode material was weighed, and 0.45g of LiBO was added₂Obtaining crystalline LiBO after high-energy ball milling mixed grinding for 30min₂The modified silicon-carbon negative electrode composite material is dried for 24 hours and then is put in an argon atmosphere (300mL min) at 500 DEG C^-1) The specific surface area of the product is 20.49m after the annealing for 4 hours² g^-1The initial capacity of the material as a negative electrode material of the lithium battery is 1200mA h g^-1Has good cycling stability and rate capability, and is cycled for more than 1200 times, 10A g^-1The capacity is kept above 70% under the current density.

Example 9

2.70g FeCl was weighed₃·6H₂O (0.01mol) was dissolved in 100mL of deionized water, and 6mL of concentrated aqueous ammonia (28%) was added dropwise and stirred overnight. 2.50g of Li were weighed₃BO₃Dissolved in 45mL of water, if the solution is too low at room temperature to be completely dissolved, the solution can be heated to about 60 ℃. Mixing Li₃BO₃The solution is added to the aged Fe (OH) solution₃In the dispersion of (2), since Fe (OH)₃Fe in the solution is easily absorbed in the precipitation process³⁺The ions make the surface thereof positively charged, and Li is added₃BO₃The borate ions in the solution after the solution are negatively charged, so that part of the borate ions in the solution are adsorbed to Fe (OH) due to the principle of electrostatic adsorption₃Surface of the precipitateThe post-lithium ions are also partially attached to the precipitation surface by electrostatic adsorption with the borate ions to form an amorphous Li-B-O layer covering Fe (OH)₃The structure of (1) is not washed after the solution is filtered, otherwise most of Li-B-O may be washed out to cause deterioration of the effect. The precipitate was lyophilized for 24 hours and then dried under argon at 500 deg.C (300mL min)^-1) Annealing for 4 hours, wherein in the annealing process, Fe (OH)₃Dehydrated to form FeOx and grow, and an amorphous Li-B-O layer is coated on the outer surface of the FeOx and is possibly partially melted due to the lower melting point of the amorphous Li-B-O layer, so that different FeOx particles are bonded together to form larger secondary particles, and the specific surface area of the product is 8.84m² g^-1Wherein the content of amorphous borate is 19.6 percent measured by ICP-AES, and the initial capacity of the amorphous borate as the negative electrode material of the lithium battery is 780mA h g^-1Has good cycling stability and rate capability, and cycles more than 1000 times, 10A g^-1The capacity is kept above 85% under the current density.

Example 10

2.70g FeCl was weighed₃·6H₂O (0.01mol) was dissolved in 100mL of deionized water, and 6mL of concentrated aqueous ammonia (28%) was added dropwise and stirred overnight. 2.50g of Li were weighed₂B₄O₇Dissolved in 45mL of water, if the solution is too low at room temperature to be completely dissolved, the solution can be heated to about 60 ℃. Mixing Li₂B₄O₇The solution is added to the aged Fe (OH) solution₃In the dispersion of (2), since Fe (OH)₃Fe in the solution is easily absorbed in the precipitation process³⁺The ions make the surface thereof positively charged, and Li is added₂B₄O₇The borate ions in the solution after the solution are negatively charged, so that part of the borate ions in the solution are adsorbed to Fe (OH) due to the principle of electrostatic adsorption₃The precipitated surface, and then lithium ions are also partially attached to the precipitated surface due to electrostatic adsorption with borate ions, forming an amorphous Li-B-O layer coating Fe (OH)₃The structure of (1) is not washed after the solution is filtered, otherwise most of Li-B-O may be washed out to cause deterioration of the effect. The precipitate was lyophilized for 24 hours and then dried under argon at 500 deg.C (300mL min)^-1) Annealing for 4 hours, wherein in the annealing process, Fe (OH)₃Dehydrated to form FeOx and grow, an amorphous Li-B-O layer coats the outer surface of the FeOx and is likely to be partially melted due to the lower melting point of the amorphous Li-B-O layer, different FeOx particles are bonded together to form larger secondary particles, and the specific surface area of the product is 8.98m² g^-1Wherein the content of amorphous borate is 19.8 percent measured by ICP-AES, and the initial capacity of the amorphous borate as the negative electrode material of the lithium battery is 770mA h g^-1Has good cycling stability and rate capability, and cycles more than 1000 times, 10A g^-1The capacity is kept above 86% under the current density.

Example 11

2.70g FeCl was weighed₃·6H₂O (0.01mol) was dissolved in 100mL of deionized water, and 6mL of concentrated aqueous ammonia (28%) was added dropwise and stirred overnight. 2.50g of Li were weighed₆B₄O₉Dissolved in 45mL of water, if the solution is too low at room temperature to be completely dissolved, the solution can be heated to about 60 ℃. Mixing Li₆B₄O₉The solution is added to the aged Fe (OH) solution₃In the dispersion of (2), since Fe (OH)₃Fe in the solution is easily absorbed in the precipitation process³⁺The ions make the surface thereof positively charged, and LiBO is added₂The boroxonate ions in the solution after the solution are negatively charged, so that due to the principle of electrostatic adsorption, part of the boroxonate ions in the solution are adsorbed to Li₆B₄O₉The precipitated surface, and then lithium ions are also partially attached to the precipitated surface due to electrostatic adsorption with borate ions, forming an amorphous Li-B-O layer coating Fe (OH)₃The structure of (1) is not washed after the solution is filtered, otherwise most of Li-B-O may be washed out to cause deterioration of the effect. The precipitate was lyophilized for 24 hours and then dried under argon at 500 deg.C (300mL min)^-1) Annealing for 4 hours, wherein in the annealing process, Fe (OH)₃Dehydrated to form FeOx and grow, and an amorphous Li-B-O layer is coated on the outer surface of the FeOx and is possibly partially melted due to the lower melting point of the amorphous Li-B-O layer, so that different FeOx particles are bonded together to form larger secondary particles, and the specific surface area of the product is 8.42m² g^-1Wherein the content of amorphous borate is 20.3% measured by ICP-AES, and the initial capacity of the amorphous borate as the lithium battery cathode material is 760mAh g^-1Has good circulation stability and rate capability, circulates more than 1000 times, 10Ag^-1The capacity is kept above 87% under the current density. The reasons for the initial capacity drop are: the larger the borate, the more the charge, the more it is coated on the surface of the material by electrostatic adsorption, resulting in an increase in the content and a decrease in the initial capacity.

Example 12

2.70g FeCl was weighed₃·6H₂O (0.01mol) was dissolved in 100mL of deionized water, and 6mL of concentrated aqueous ammonia (28%) was added dropwise and stirred overnight. 2.50g NaBO are weighed out₂Dissolved in 45mL of water, if the solution is too low at room temperature to be completely dissolved, the solution can be heated to about 60 ℃. Mixing NaBO₂The solution is added to the aged Fe (OH) solution₃In the dispersion of (2), since Fe (OH)₃Fe in the solution is easily absorbed in the precipitation process³⁺The ions make the surface of the material positively charged, and NaBO is added₂The borate ions in the solution after the solution are negatively charged, so that part of the borate ions in the solution are adsorbed to Fe (OH) due to the principle of electrostatic adsorption₃The precipitated surface, and then lithium ions are also partially attached to the precipitated surface due to electrostatic adsorption with the borate ions, forming an amorphous Na-B-O layer coating Fe (OH)₃The structure of (1) is not washed after the solution is filtered, otherwise most of Na-B-O may be washed off, resulting in poor effect. The precipitate was lyophilized for 24 hours and then dried under argon at 500 deg.C (300mL min)^-1) Annealing for 4 hours, wherein in the annealing process, Fe (OH)₃Dehydrated to form FeOx and grow, and an amorphous Na-B-O layer is coated on the outer surface of the FeOx and is possibly partially melted due to the lower melting point of the amorphous Na-B-O layer, so that different FeOx particles are bonded together to form larger secondary particles, and the specific surface area of the product is 8.67m² g^-1Wherein the content of amorphous borate is 17.4% measured by ICP-AES, and the initial capacity of the amorphous borate as the negative electrode material of the lithium battery is 750mAh g^-1Has good circulation stability and rate capability, circulates more than 1000 times, 10Ag^-1The capacity is kept above 90% under the current density. The reason for the above properties is that NaBO₂Water solubility ratio of LiBO₂Strong, less prone to coating the particle surface during co-precipitation, resulting inThe content is reduced; NaBO on the other hand₂The lithium ion conducting capacity in the initial process is weak, and the exertion of the electrode capacity is influenced.

Example 13

2.70g FeCl was weighed₃·6H₂O (0.01mol) was dissolved in 100mL of deionized water, and 6mL of concentrated aqueous ammonia (28%) was added dropwise and stirred overnight. Weighing 2.50g KBO₂Dissolved in 45mL of water, if the solution is too low at room temperature to be completely dissolved, the solution can be heated to about 60 ℃. Will KBO₂The solution is added to the aged Fe (OH) solution₃In the dispersion of (2), since Fe (OH)₃Fe in the solution is easily absorbed in the precipitation process³⁺Ions make its surface positively charged, and KBO is added₂The borate ions in the solution after the solution are negatively charged, so that part of the borate ions in the solution are adsorbed to Fe (OH) due to the principle of electrostatic adsorption₃The precipitated surface, and then lithium ions are also partially attached to the precipitated surface due to electrostatic adsorption with the borate ions to form an amorphous K-B-O layer coating Fe (OH)₃The structure of (1) is not washed after the solution is filtered, otherwise most of K-B-O may be washed away, resulting in poor effect. The precipitate was lyophilized for 24 hours and then dried under argon at 500 deg.C (300mL min)^-1) Annealing for 4 hours, wherein in the annealing process, Fe (OH)₃Dehydrated to form FeOx and grow, and an amorphous K-B-O layer is coated on the outer surface of the FeOx and is possibly partially melted due to the lower melting point of the amorphous K-B-O layer to bond different FeOx particles together to form larger secondary particles, and the specific surface area of the product is 8.42m² g^-1Wherein the content of amorphous borate is 19.4% measured by ICP-AES, and the initial capacity of the amorphous borate as the negative electrode material of the lithium battery is 700mA h g^-1Has good cycling stability and rate capability, and 10A g times of cycling for more than 500 times^-1The capacity is kept above 90% under the current density.

Example 14

3g of commercial lithium cobaltate material was weighed out and dispersed in 100mL of deionized water and stirred for 2 hours. Weighing 2.50g LiBO₂(0.05mol) in 45mL of water, e.g., the incomplete dissolution at room temperature is low and the dissolution can be carried out at about 60 ℃. Mixing LiBO₂The solution was added to the dispersion of the above lithium cobaltateIn the liquid, LiBO is added because the surface of lithium cobaltate is positively charged₂The borate ions in the solution after the solution is dissolved are negatively charged, so due to the electrostatic adsorption principle, part of the borate ions in the solution are adsorbed to the surface of the lithium cobaltate, and then part of the lithium ions are also attached to the surface of the precipitate due to the electrostatic adsorption with the borate ions, so that an amorphous Li-B-O layer covering the lithium cobaltate structure is formed, the solution is not washed after being filtered, otherwise, most of the Li-B-O can be washed away, and the effect is deteriorated. The precipitate was lyophilized for 24 hours and then dried under argon at 500 deg.C (300mL min)^-1) The intermediate annealing is carried out for 4 hours to obtain an amorphous Li-B-O layer which is coated on the outer surface of the lithium cobaltate and is possible to be partially melted due to the lower melting point of the amorphous Li-B-O layer, different lithium cobaltate particles are bonded together to form larger secondary particles, and the specific surface area of the product is 2.42m² g^-1Wherein the content of amorphous borate is 12.4% measured by ICP-AES, and the initial capacity of the amorphous borate as the lithium battery anode material is 200mA h g^-1Has good cycling stability and rate capability, and is cycled for more than 1200 times, 10A g^-1The capacity of the product is kept above 80% under the current density, and the transmission electron microscope picture, the scanning electron microscope picture, the X-ray powder diffraction, the nitrogen adsorption and desorption isotherm and the electrochemical performance of the product as the negative electrode of the lithium ion battery are shown in figures 9 and 10-14.

As can be seen from the transmission electron microscope picture of FIG. 9, the prepared composite material was an agglomerated core with crystalline lithium cobaltate and amorphous lithium metaborate (LiBO)₂) The decorative layer of (2). It can be seen from fig. 11 that both have distinct diffraction peaks for iron oxide, but no associated diffraction peaks for the borate, indicating that the borate is amorphous. From FIG. 12, it can be calculated that the ionic conductivity of the material can reach 2.6mS cm^-1. It can be seen from fig. 13 that the capacity and cycling stability of the borate modified lithium cobaltate positive electrode is greatly enhanced. It can be seen from the data in fig. 14 that the rate of the borate modified lithium cobaltate positive electrode is good.

Example 15

3g of the commercially available lithium cobaltate positive electrode material was weighed out, and 0.45g of LiBO was added₂Mixing and grinding in agate mortar for 30minObtaining crystalline LiBO₂The modified lithium cobaltate composite material is dried for 24 hours and then is put under the argon atmosphere (300mL min) at 500 DEG C^-1) The specific surface area of the product is 2.49m after the medium annealing for 4 hours² g^-1The initial capacity of the lithium battery anode material is 200mA h g^-1Has good cycling stability and rate capability, and is cycled for more than 1200 times, 10A g^-1The capacity is kept above 70% under the current density.

Example 16

3g of the commercial 811 type ternary positive electrode material obtained by purchase was weighed, and 0.45g of LiBO was added₂Mixing and grinding the mixture in an agate mortar for 30min to obtain crystalline LiBO₂The modified 811 type ternary positive electrode composite material is dried for 24 hours and then is put in an argon atmosphere (300mL min) at 500 DEG C^-1) The specific surface area of the product is 2.49m after the medium annealing for 4 hours² g^-1The initial capacity of the lithium battery anode material is 220mA h g^-1Has good cycling stability and rate capability, and is cycled for more than 1200 times, 10A g^-1The capacity is kept above 70% under the current density.

Example 17

3g of a commercial 811 type ternary cathode material was weighed out and dispersed in 100mL of deionized water. Weighing 2.50g LiBO₂(0.05mol) in 45mL of water, e.g., the incomplete dissolution at room temperature is low and the dissolution can be carried out at about 60 ℃. Mixing LiBO₂The solution is added into the dispersion liquid of the 811 type ternary cathode material, and LiBO is added because the surface of the 811 type ternary cathode material is positively charged₂The boroxine ions in the solution after the solution is dissolved are negatively charged, so due to the electrostatic adsorption principle, part of the boroxine ions in the solution are adsorbed to the surface of the 811 type ternary cathode material, and then part of lithium ions are also attached to the precipitation surface due to the electrostatic adsorption with the boroxine ions, so that a structure that an amorphous Li-B-O layer covers the 811 type ternary cathode material is formed, the solution is not washed after being filtered, otherwise most of the Li-B-O can be washed away, and the effect is poor. The precipitate was lyophilized for 24 hours and then dried under argon at 500 deg.C (300mL min)^-1) The intermediate annealing is carried out for 4 hours to obtain an amorphous Li-B-O layer which is coated on the outer surface of the 811 type ternary cathode material and has a lower melting pointAnd may be partially melted to bond different 811 type ternary cathode material particles together to form larger secondary particles, and the specific surface area of the product is 2.42m² g^-1Wherein the content of amorphous borate is 12.4% measured by ICP-AES, and the initial capacity of the amorphous borate as the lithium battery anode material is 220mA h g^-1Has good cycling stability and rate capability, and cycles more than 1000 times, 10A g^-1The capacity is kept above 80% under the current density. The composite material of example 17 has a slightly inferior performance compared with example 14, because lithium cobaltate itself does not generate side reaction when meeting water, and has a stable structure, but the ternary material generates some side reaction when meeting water, and the surface structure changes, and the effect is slightly inferior.

Comparative example 1

2.70g FeCl was weighed₃·6H₂O (0.01mol) was dissolved in 100mL of deionized water, and 6mL of concentrated aqueous ammonia (28%) was added dropwise and stirred overnight. The solution was filtered and washed free, and the precipitate was dried by freeze-drying for 24 hours and then treated with argon atmosphere at 500 deg.C (300mL min)^-1) Annealing for 4 hours, wherein in the annealing process, Fe (OH)₃Dehydrated to form FeOx and grow up to form larger monodisperse FeOx particles with the specific surface area of 15.36m² g^-1The initial capacity of the lithium battery anode material is 1000mA h g^-1But capacity decays very quickly and rate performance is poor.

It can be seen from the transmission electron microscope picture of fig. 2 that the prepared material is dispersed iron oxide particles with no coating and modification on the surface.

Comparative example 2

3g of commercial lithium cobaltate material was weighed out and dispersed in 100mL of deionized water and stirred for 2 hours. The solution was filtered and washed free, and the precipitate was dried by freeze-drying for 24 hours and then treated with argon atmosphere at 500 deg.C (300mL min)^-1) The medium annealing is carried out for 4 hours to obtain a comparative sample lithium cobaltate, and the specific surface area of a product is 3.42m² g^-1The initial capacity of the lithium battery anode material is 200mA h g^-1But decays rapidly and rate performance is poor. As can be seen from the transmission electron microscope picture of FIG. 10, the prepared material is the dispersed cobaltic acid without coating and modification on the surfaceLithium positive electrode particles.