Positive electrode material of modified lithium manganate power battery and preparation method thereof
阅读说明：本技术 一种改性锰酸锂动力电池的正极材料及其制备方法 (Positive electrode material of modified lithium manganate power battery and preparation method thereof ) 是由 皮远建 张福建 彭吕红 许赫奕 于 2019-09-12 设计创作，主要内容包括：本发明属于电学领域,具体涉及一种改性锰酸锂动力电池的正极材料及其制备方法。本发明提供的改性锰酸锂动力电池的正极材料,采用锰酸锂和锂快离子导体多孔锂钛氧镧表层组成核壳状复合结构,将表面修饰与微纳结构设计相结合。本发明提供的锂钛氧镧包覆改性锰酸锂动力电池,不仅加大了锂离子迁移速率、进一步提高了材料倍率性能,而且有效地防止了表面锰的溶解以及与电解液之间发生的化学性变化,进而改善材料的循环性能。(The invention belongs to the field of electricity, and particularly relates to a modified lithium manganate power battery positive electrode material and a preparation method thereof. The invention provides a modified lithium manganate power battery anode material, which adopts a core-shell composite structure formed by lithium manganate and a lithium fast ion conductor porous lithium titanium oxide lanthanum surface layer, and combines surface modification and micro-nano structure design. The lithium titanium oxide lanthanum-coated modified lithium manganate power battery provided by the invention not only increases the lithium ion migration rate and further improves the rate capability of the material, but also effectively prevents the dissolution of surface manganese and the chemical change between the surface manganese and an electrolyte, thereby improving the cycle performance of the material.)
1. The positive electrode material of the modified lithium manganate power battery is characterized in that the positive electrode material is (La)2/3-XLi3X)TiO3·LiMn2O4Wherein X may be 0, 1/18, 1/9, 1/6.
2. The preparation method of the positive electrode material of the modified lithium manganate power battery as defined in claim 1, characterized by comprising the following steps:
s1, weighing 2.5g of lanthanum nitrate, 3.2g of lithium carbonate and 2.8g of titanium dioxide, coating the lanthanum nitrate, the lithium carbonate and the titanium dioxide with a fast ion conductor lithium titanium oxide, dissolving the lanthanum nitrate, the lithium carbonate and the titanium dioxide in deionized water respectively, adding the fast ion conductor lithium titanium oxide into each solution, and treating the solution for 2 to 3 hours under a vacuum condition to obtain a mixed lanthanum solution A, a mixed lithium solution B and a mixed titanium solution C;
s2, maintaining a vacuum environment, adding sodium hydroxide serving as a precipitator into the mixed lanthanum solution A obtained in the step S1, adding a sodium sulfate solution serving as a precipitator into the mixed lithium solution B obtained in the step S1, adding a sodium phosphate solution serving as a precipitator into the mixed titanium solution C obtained in the step S1, adjusting the pH value of each solution to 8-9, then respectively placing the three solutions into a reaction kettle, and cooling, filtering, washing and drying to obtain a lanthanum salt precursor, a lithium salt precursor and a titanium salt precursor;
s3, mixing the lanthanum salt precursor, the lithium salt precursor and the titanium salt material precursor obtained in the step S2 to obtain a composite fast ion conductor lithium titanium oxide lanthanum embedded precursor;
s4, calcining the composite fast ion conductor lithium titanium lanthanum embedded precursor obtained in the step S3 at a high temperature for 5-7 h to obtain a lithium titanium lanthanum/lithium manganate positive electrode material;
and S5, analyzing the composition, phase, morphology and granularity of the lithium titanium lanthanum oxide/lithium manganate positive electrode material obtained in the step S4 by using methods such as an ICP spectrometer, an X-ray diffractometer, an SEM (scanning electron microscope), an X-ray energy spectrometer, a granularity distributor and the like, and obtaining the lithium titanium lanthanum oxide/lithium manganate positive electrode material.
3. The method for preparing the modified lithium manganate anode material of a power battery as in claim 2, wherein said vacuum condition in step S1 is 200-400W power and 45-55 KHz frequency.
4. The method for preparing the positive electrode material of the modified lithium manganate power battery as described in claim 2, wherein the reaction conditions of the step S2 in the reaction kettle are 400-600 ℃ and the reaction time is 16-22 h.
5. The method for preparing the modified lithium manganate anode material for power battery as claimed in claim 2, wherein the stoichiometric ratio of the lanthanum salt precursor, lithium salt precursor and titanium salt precursor in said step S3 is: 6-9: 6: 3-4.
6. The method for preparing the modified lithium manganate anode material of a power battery as claimed in claim 5, wherein the stoichiometric ratios of the lanthanum salt precursor, lithium salt precursor and titanium salt precursor in step S3 are respectively: 8: 6: 3.5.
7. the method for preparing the positive electrode material of the modified lithium manganate power battery as described in claim 2, wherein the specific conditions of the high temperature calcination process in step S4 are 400-800 ℃.
Technical Field
The invention belongs to the field of electricity, and particularly relates to a modified lithium manganate power battery positive electrode material and a preparation method thereof.
Background
The positive electrode material is an important component of the lithium ion battery, and the performance of the positive electrode material is directly related to the performance of the lithium ion battery. Currently, the anode materials of lithium ion batteries are mainly divided into four types: LiCoO with a layered structure2And LiNi1/3Co1/3Mn1/3O2Spinel-structured LiMn2O4And olivine-structured LiFePO4。LiCoO2(theoretical specific capacity 274mAh g-1The actual specific capacity is about 140mAh g-1) The lithium ion battery anode material has the advantages of high working voltage (3.6V), stable discharge, good cycle performance, simple preparation process and the like, and is a main anode material of a commercialized low-power battery at present. Because of the lack of cobalt resource, the safety is not very good, the price is expensive, the environment is polluted, especially the current cobalt price continuously rises, and great pressure is brought to the survival of lithium ion battery production enterprises. With LiCoO2In contrast, LiNi which is also of a layered structure1/3Co1/3Mn1/3O2(theoretical specific capacity is 278mAh g-1The actual specific capacity is about 150mAh g-1) The cost is higher, the safety is better, but the first discharge efficiency and the discharge voltage platform are lower. Olivine structured LiFePO4(theoretical specific capacity 170 mAh. g)-1The actual specific capacity is about 145mAh g-1) Has excellent normal-temperature cycle performance and environmental friendliness. However, its harsh synthesis conditions, high preparation cost, low energy density and poor low-temperature cycle performance limit its further industrialization.
Among the numerous lithium ion battery positive electrode materials, spinel LiMn2O4(theoretical specific capacity of 148mAh g-1The actual specific capacity is about 120mAh g-1) Compared with LiCoO2、LiNiO2And layered LiMnO2The cathode material has the advantages of abundant resources, low price, good stability, high working voltage, high-power charge and discharge, no pollution and the like, and is three-dimensionalCompared with a layered compound, the tunnel structure is more beneficial to the insertion and extraction of lithium ions, has great potential in the competition of the lithium ion battery cathode material, particularly shows very good application prospect on Electric Vehicles (EV) and Hybrid Electric Vehicles (HEV), becomes an object which is paid attention to by researchers, and is one of the cathode materials which are considered to have the greatest application prospect, are researched the most and have the greatest development force at present.
However, the spinel LiMn2O4The cycle performance, particularly the high-temperature cycle performance, needs to be improved, and the capacity attenuation in the cycle process is fast, so that the further application of the lithium manganate is hindered. It is currently believed that the Jahn-Teller effect, manganese dissolution, and electrolyte oxidative decomposition, among others, are responsible for the spinel LiMn2O4The main cause of capacity fade. Although the use of polymer electrolytes alleviates this problem to some extent, it is not fundamentally solved. Surface coating and bulk phase doping modification are considered to be the simplest methods which can effectively improve the electrochemical performance of the spinel, and the surface coating can prevent the dissolution of manganese on the surface of the spinel and the chemical change between the spinel and an electrolyte. However, the surface coatings employed by most researchers and businesses suffer from the following problems: (1) coating with materials having good electronic conductivity, e.g. Ni, Ag, Al2O3And SiO2The contact between the lithium manganate and the electrolyte can be prevented, the conductivity between lithium manganate particles is good, but the further migration of lithium ions is also hindered, the ionic conductivity of the lithium manganate particles is poor, and the electrochemical performance of the lithium manganate material is deteriorated; (2) coating materials with good ionic conductivity, e.g. CoO1+x/ZrO2The lithium ion migration becomes good, but the electron conductivity between the coated lithium manganate particles becomes poor, and the electrochemical performance becomes poor. The cladding layer should ideally be a material that is both ionically and electronically conductive.
Chinese patent application CN108365215A discloses a method for preparing a positive electrode of a lithium nickel manganese oxide battery, wherein the positive electrode material of the battery is prepared by mixing lithium oxalate, manganese chloride and nickel citrate according to a certain proportion, the production process is simple, the operation is easy, the energy consumption is low, the cost is low, the large-scale industrial production is easy to realize, and the production efficiency is high.
In conclusion, the prior art generally has the defects that the conductivity of an electrode material is poor, the electrochemical performance of the material is easily deteriorated, the capacity of a battery is quickly attenuated, and the application range of a lithium manganate battery is limited.
Disclosure of Invention
Aiming at the defects generally existing in the prior art, the invention combines the inherent electrochemical performance characteristics of a lithium fast ion conductor and the application prospect of spinel lithium manganate as a lithium ion power battery, provides the combination of surface modification and micro-nano structure design, adopts a coprecipitation method to prepare the lithium titanium lanthanum-coated lithium manganate composite anode material for the power lithium ion battery, and adopts a core-shell composite structure consisting of the lithium manganate and a porous lithium titanium lanthanum oxide surface layer of the lithium fast ion conductor, thereby not only increasing the lithium ion migration rate and further improving the rate performance of the material, but also effectively preventing the dissolution of surface manganese and the chemical change between the surface manganese and electrolyte, and further improving the cycle performance of the material.
In order to achieve the purpose, the invention adopts the technical scheme that:
the positive electrode material of the modified lithium manganate power battery is (La2/3-Xli3X) TiO 3. LiMn2O4, wherein X can be 0, 1/18, 1/9 or 1/6.
The preparation method of the modified lithium manganate power battery positive electrode material comprises the following steps:
s1, weighing 2.5g of lanthanum nitrate, 3.2g of lithium carbonate and 2.8g of titanium dioxide, coating the lanthanum nitrate, the lithium carbonate and the titanium dioxide with a fast ion conductor lithium titanium oxide, dissolving the lanthanum nitrate, the lithium carbonate and the titanium dioxide in deionized water respectively, adding the fast ion conductor lithium titanium oxide into each solution, and treating the solution for 2 to 3 hours under a vacuum condition to obtain a mixed lanthanum solution A, a mixed lithium solution B and a mixed titanium solution C;
s2, maintaining a vacuum environment, adding sodium hydroxide serving as a precipitator into the mixed lanthanum solution A obtained in the step S1, adding a sodium sulfate solution serving as a precipitator into the mixed lithium solution B obtained in the step S1, adding a sodium phosphate solution serving as a precipitator into the mixed titanium solution C obtained in the step S1, adjusting the pH value of each solution to 8-9, then respectively placing the three solutions into a reaction kettle, and cooling, filtering, washing and drying to obtain a lanthanum salt precursor, a lithium salt precursor and a titanium salt precursor;
s3, mixing the lanthanum salt precursor, the lithium salt precursor and the titanium salt material precursor obtained in the step S2 to obtain a composite fast ion conductor lithium titanium oxide lanthanum embedded precursor;
s4, calcining the composite fast ion conductor lithium titanium lanthanum embedded precursor obtained in the step S3 at a high temperature for 5-7 h to obtain a lithium titanium lanthanum/lithium manganate positive electrode material;
and S5, analyzing the composition, phase, morphology and granularity of the lithium titanium lanthanum oxide/lithium manganate positive electrode material obtained in the step S4 by using methods such as an ICP spectrometer, an X-ray diffractometer, an SEM (scanning electron microscope), an X-ray energy spectrometer, a granularity distributor and the like, and obtaining the lithium titanium lanthanum oxide/lithium manganate positive electrode material.
Preferably, the vacuum condition in the step S1 is 200-400W of power and 45-55 KHz of frequency.
Preferably, the reaction condition of the step S2 in the reaction kettle is 400-600 ℃ and the reaction time is 16-22 h.
Preferably, in the step S3, the stoichiometric ratio of the lanthanum salt precursor to the lithium salt precursor to the titanium salt precursor is: 6-9: 6: 3-4.
Preferably, the stoichiometric ratios of the lanthanum salt precursor, the lithium salt precursor and the titanium salt precursor in step S3 are respectively: 8: 6: 3.5.
preferably, the specific conditions of the high-temperature calcination process in the step S4 are 400-800 ℃.
Compared with the prior art, the modified lithium manganate power battery positive electrode material provided by the invention has the following advantages:
(1) according to the modified lithium manganate power battery positive electrode material, the lithium ion power battery positive electrode material is coated by the fast ion conductor lithium titanium lanthanum oxide, so that the good electronic conductivity is ensured, the ion mobility of lithium manganate is effectively improved, and the electrochemical performance of the material is further improved;
(2) the positive electrode material of the modified lithium manganate power battery provided by the invention is based on the advantages of national resources, and the resources of China are efficiently utilized while the cost is reduced;
(3) the modified lithium manganate power battery positive electrode material provided by the invention greatly improves the cycle life and shelf performance of the original lithium manganate battery.
Drawings
FIG. 1 is a TEM image of a porous lithium titanium oxide-coated lithium manganate positive electrode material.
Detailed Description
The present invention is further explained with reference to the following specific examples, but it should be noted that the following examples are only illustrative of the present invention and should not be construed as limiting the present invention, and all technical solutions similar or equivalent to the present invention are within the scope of the present invention. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art, and the raw materials used are commercially available products.
The ICP spectrometer is available from Photonic technologies (Hangzhou) Inc.; the X-ray diffractometer can be purchased from Beijing times Quhe technology Co., Ltd; the SEM scanning electron microscope can be purchased from Kyowa Korea traceability detection technology, Inc.; the X-ray energy spectrometer is available from seimer heishel technologies (china) ltd; the particle size distribution instrument is available from friedel (shanghai) instruments equipment ltd; the tap density tester can be purchased from Wancheng science and technology Limited of Beijing Zhongjie; the lithium battery capacity tester can be purchased from three pencil science and technology limited companies in Shenzhen city.