阅读说明：本技术 预锂化负极活性材料及其制备方法、负极片和锂离子电池 (Pre-lithiated negative electrode active material, preparation method thereof, negative plate and lithium ion battery ) 是由 蔡挺威 赵晓宁 邵玲 段瑞杰 邓素祥 马忠龙 于 2019-12-27 设计创作，主要内容包括：本发明提供了预锂化负极活性材料及其制备方法、负极片和锂离子电池,该方法包括：将金属锂源加入到有机溶剂中,将得到的混合物加热至所述金属锂源熔融,并搅拌使得熔融的所述金属锂源分散为颗粒,得到金属锂源颗粒分散液；向所述金属锂源颗粒分散液中加入负极活性材料,并搅拌反应预定时间,得到预锂化负极活性材料。该方法利用在有机溶剂中分散的金属锂源分散液与负极活性材料反应,实现预锂化,可减少原料和产物的团聚,搅拌条件下可以加速负极活性材料与金属锂的接触反应,提高反应效率,且预锂化过程是在有机溶剂中进行,可有效隔绝外部气氛对原料及产物的影响,提高可操作性和安全性,易规模化应用。(The invention provides a prelithiation negative electrode active material and a preparation method thereof, a negative electrode sheet and a lithium ion battery, wherein the method comprises the following steps: adding a lithium metal source into an organic solvent, heating the obtained mixture until the lithium metal source is molten, and stirring to disperse the molten lithium metal source into particles to obtain a lithium metal source particle dispersion liquid; and adding a negative electrode active material into the metal lithium source particle dispersion liquid, and stirring and reacting for a preset time to obtain the pre-lithiated negative electrode active material. The method utilizes the metal lithium source dispersion liquid dispersed in the organic solvent to react with the negative active material, realizes the pre-lithiation, can reduce the agglomeration of the raw material and the product, can accelerate the contact reaction of the negative active material and the metal lithium under the stirring condition, improves the reaction efficiency, and the pre-lithiation process is carried out in the organic solvent, can effectively isolate the influence of the external atmosphere on the raw material and the product, improves the operability and the safety, and is easy for large-scale application.)

1. A method of preparing a prelithiated negative active material, comprising:

adding a lithium metal source into an organic solvent, heating the obtained mixture until the lithium metal source is molten, and stirring to disperse the molten lithium metal source into particles to obtain a lithium metal source particle dispersion liquid;

and adding a negative electrode active material into the metal lithium source particle dispersion liquid, and stirring and reacting for a preset time to obtain the pre-lithiated negative electrode active material.

2. The method according to claim 1, wherein the organic solvent satisfies at least one of the following conditions:

the boiling point of the organic solvent is more than 200 ℃;

the viscosity of the organic solvent is 100-2000 CS;

the organic solvent comprises one or more of silicone oil, undecane, dodecane, white oil and paraffin.

3. The method of claim 1, wherein the lithium metal source comprises at least one of a lithium block, a lithium sheet, a lithium rod, a lithium foil, and a lithium powder;

optionally, the lithium metal source has a purity of not less than 95%.

4. The method of claim 1, wherein at least one of the following conditions is satisfied:

in the mixture of the metal lithium source and the organic solvent, the content of the metal lithium source is 1-30 g/L;

the temperature for heating the mixture of the lithium metal source and the organic solvent is 200-350 ℃;

the stirring speed of the mixture of the lithium metal source and the organic solvent is 2000-20000 rpm;

the stirring speed of the stirring reaction is 100-1000 rpm;

the preset time is 1h-24 h.

5. The method of claim 1, wherein the negative active material comprises a silicon-based material;

preferably, the silicon-based material includes at least one of elemental silicon and silica.

6. The method according to claim 1, wherein the charging mass ratio of the negative electrode active material to the lithium metal source is 1:20 to 1: 1; preferably 1:10 to 1: 5.

7. A pre-lithiated negative electrode active material characterized by being produced by the method according to any one of claims 1 to 6.

8. The prelithiated anode active material according to claim 7, wherein at least one of the following conditions is satisfied:

the chemical composition of the prelithiated negative active material is L i_xSiO_y，0<x is less than or equal to 4.4, y is more than or equal to 0 and less than or equal to 1; preferably 0.4<x<0.8；

The ratio of the particle size of the pre-lithiated anode active material to the particle size of the anode active material is greater than 1 and less than 1.5.

9. A negative electrode sheet comprising the prelithiated negative electrode active material of claim 7 or 8.

10. A lithium ion battery comprising the prelithiated negative electrode active material of claim 7 or 8 or the negative electrode sheet of claim 9.

Technical Field

The invention relates to the technical field of lithium ion batteries, in particular to a prelithiation negative electrode active material, a preparation method thereof, a negative electrode sheet and a lithium ion battery.

Background

With the rapid development of new energy vehicles, the requirements on the energy density and the safety performance of the power battery for vehicles are continuously improved. The silicon negative electrode becomes the first choice of the negative electrode for the high-energy-density battery at the present stage due to the excellent performance of the silicon negative electrode, but one of the problems still existing in the silicon negative electrode is that the first coulombic efficiency is low, and the improvement of the energy density of the battery is hindered. Common methods for solving the first coulombic inefficiency include: the lithium salt pre-lithium method is mainly used for pre-lithiation of the silica material, and the lithium salt reacts with the silica component in the silica material at a high temperature to form stable products such as lithium silicate and the like, so that the irreversible capacity loss in the charge and discharge processes of the silica material is reduced, and the purpose of improving the first effect is achieved. However, the pre-lithiation degree of the method is limited by the composition of the silicon-oxygen material, the pre-lithiation degree is limited, and the silicon material is easy to agglomerate in the high-temperature sintering process; a melting method, namely adding a silicon-based material into molten lithium metal, or mixing the silicon-based material with lithium metal powder and then heating until the lithium is molten, and stirring and mixing to enable the lithium and the silicon to react with each other to form products such as lithium-silicon alloy and the like; the preparation method needs strict control of anhydrous and oxygen-free environment, and the product is easy to agglomerate.

Thus, currently, a pre-lithiation process of an anode active material still remains to be improved.

Disclosure of Invention

The present invention is directed to solving, at least to some extent, one of the technical problems in the related art. Therefore, one objective of the present invention is to provide a method for preparing a prelithiation negative electrode active material, which can reduce agglomeration of product materials, effectively isolate the influence of external atmosphere on raw materials and products, improve operability and safety, facilitate large-scale application, or realize regulation and control of prelithiation degree, and meet the prelithiation requirements of different negative electrode active materials.

In one aspect of the invention, a method of making a prelithiated negative active material is provided. According to an embodiment of the invention, the method comprises: adding a lithium metal source into an organic solvent, heating the obtained mixture until the lithium metal source is molten, and stirring to disperse the molten lithium metal source into particles to obtain a lithium metal source particle dispersion liquid; and adding a negative electrode active material into the metal lithium source particle dispersion liquid, and stirring and reacting for a preset time to obtain the pre-lithiated negative electrode active material. The method utilizes the metal lithium source dispersion liquid dispersed in the organic solvent to react with the negative active material, realizes the pre-lithiation, can reduce the agglomeration of the raw material and the product, can accelerate the contact reaction of the negative active material and the metal lithium under the stirring condition, improves the reaction efficiency, and the pre-lithiation process is carried out in the organic solvent, can effectively isolate the influence of the external atmosphere on the raw material and the product, improves the operability and the safety, and is easy for large-scale application.

According to an embodiment of the present invention, the organic solvent satisfies at least one of the following conditions: the boiling point of the organic solvent is more than 200 ℃; the viscosity of the organic solvent is 100-2000 CS; the organic solvent comprises one or more of silicone oil, undecane, dodecane, white oil and paraffin.

According to an embodiment of the present invention, the lithium metal source includes at least one of a lithium block, a lithium sheet, a lithium rod, a lithium foil, and a lithium powder.

According to an embodiment of the present invention, the purity of the lithium metal source is not less than 95%.

According to the embodiment of the invention, the method meets at least one of the following conditions that the content of the metal lithium source in the mixture of the metal lithium source and the organic solvent is 1-30 g/L, the heating temperature of the metal lithium source dispersion liquid is 200-350 ℃, the stirring speed of the metal lithium source dispersion liquid is 2000-20000rpm, the stirring speed of the stirring reaction is 100-1000rpm, and the predetermined time is 1-24 h.

According to an embodiment of the present invention, the negative active material includes a silicon-based material.

According to an embodiment of the present invention, the silicon-based material includes at least one of elemental silicon and silica.

According to the embodiment of the invention, the feeding mass ratio of the negative electrode active material to the metal lithium source is 1: 20-1: 1; preferably 1:10 to 1: 5.

In another aspect of the invention, the invention provides a prelithiated negative active material. According to embodiments of the present invention, the prelithiated anode active material is prepared by the method described above. The pre-lithiation cathode active material has good electrochemical performance, and the first coulombic efficiency is obviously improved.

According to an embodiment of the present invention, at least one of the following conditions is satisfied, the chemical composition of the prelithiated anode active material being L i_xSiO_y，0<x is less than or equal to 4.4, y is more than or equal to 0 and less than or equal to 1; preferably 0.4<x<0.8; the ratio of the particle size of the pre-lithiated anode active material to the particle size of the anode active material is greater than 1 and less than 1.5.

In still another aspect of the present invention, the present invention provides a negative electrode sheet. According to an embodiment of the present invention, the negative electrode sheet includes the previously described pre-lithiated negative electrode active material. The negative plate has good electrochemical performance, and the first coulombic efficiency is obviously improved.

In yet another aspect of the present invention, a lithium ion battery is provided. According to an embodiment of the present invention, the lithium ion battery comprises the pre-lithiated negative active material or the negative electrode sheet described above. The lithium ion battery has better electrochemical performance, and the first coulombic efficiency is obviously improved.

Drawings

Fig. 1 is a schematic flow diagram of a method of preparing a prelithiated anode active material according to one embodiment of the present invention.

Fig. 2 is a charge and discharge curve of a battery cell assembled by the negative electrode active materials of example 1 of the present invention and comparative example 1.

Fig. 3 is a result of a first coulombic efficiency test of battery cells assembled from the negative active materials of example 1 of the present invention and comparative example 1.

Detailed Description

The following describes embodiments of the present invention in detail. The following examples are illustrative only and are not to be construed as limiting the invention. The examples, where specific techniques or conditions are not indicated, are to be construed according to the techniques or conditions described in the literature in the art or according to the product specifications. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products commercially available.

In one aspect of the invention, a method of making a prelithiated negative active material is provided. According to an embodiment of the invention, referring to fig. 1, the method comprises the steps of:

s100: adding a lithium metal source into an organic solvent, heating the obtained mixture until the lithium metal source is molten, and stirring to disperse the molten lithium metal source into particles to obtain a lithium metal source particle dispersion liquid.

According to an embodiment of the present invention, the metallic lithium source may include at least one of a lithium block, a lithium sheet, a lithium rod, a lithium foil, and a lithium powder. Therefore, the source of the metal lithium source is wide and easy to obtain, and the pre-lithiation effect is good. Specifically, the purity of the lithium metal source is not less than 95% (specifically, 95%, 96%, 97%, 98%, 99%, etc.). Within the purity range, the impurity content is lower, the possibility of causing side reaction is lower, the pre-lithiation effect is better, and the electrochemical performance of the obtained pre-lithiation cathode active material is better.

According to embodiments of the present invention, the organic solvent that does not react with the lithium metal source and the negative electrode active material and does not dissolve the lithium metal source may be used, and specifically, in some embodiments, the boiling point of the organic solvent is greater than 200 ℃ (for example, 205 ℃, 210 ℃, 215 ℃, 220 ℃, 225 ℃, 230 ℃, 235 ℃, 240 ℃, 245 ℃, 250 ℃, etc.), so that the organic solvent has good stability when heated, and can obtain a dispersion liquid of lithium metal source particles with good stability, which is beneficial for subsequent steps. In some embodiments, the viscosity of the organic solvent can be 100-2000CS (e.g., 100CS, 500CS, 1000CS, 1500CS, 2000CS, etc.). In the viscosity range, the organic solvent has higher thermal stability, and stable metal lithium source particle dispersion liquid can be obtained; when the viscosity is too low, the thermal stability of the organic solvent is poor, which is not favorable for long-time stable dispersion of the metal lithium source; when the viscosity is too high, the metal lithium source is not easy to form small-sized metal lithium particles through stirring and dispersion, and is also not beneficial to uniform dispersion of the negative electrode active material, so that the pre-lithium effect of the product is influenced, and agglomeration is easy to occur. In some embodiments, the organic solvent may include one or more of silicone oil, undecane, dodecane, white oil, and paraffin. Therefore, the lithium ion battery has better thermal stability, can well disperse the metal lithium source, and has wide sources and lower cost.

It should be noted that the viscosities described herein are measured at 25 degrees celsius using a boehler flight DV1MRV viscometer.

According to the embodiment of the invention, after the metallic lithium source is added into the organic solvent, a mixture of the metallic lithium source and the organic solvent can be obtained, wherein the content of the metallic lithium source in the mixture of the metallic lithium source and the organic solvent is 1-30 g/L (specifically 1 g/L, 2.5 g/L0, 5 g/L1, 7.5 g/L2, 10 g/L3, 12.5 g/L, 15 g/L, 17.5 g/L, 20 g/L, 22.5 g/L, 25 g/L, 27.5 g/L, 30 g/L and the like) within the content range, the metallic lithium can be sufficiently and uniformly dispersed to form small-sized particles, and the particles are in contact reaction with the dispersed anode active material, so that the pre-lithium degree and the preparation efficiency of the product are ensured, if the content is too high, the metallic lithium is not easily dispersed uniformly, the agglomeration of the product is easily caused, and if the content is too low, the concentration of the metallic lithium dispersion liquid affects the preparation efficiency of the anode active material.

According to an embodiment of the present invention, after the metallic lithium source is added to the organic solvent, the mixture of the metallic lithium source and the organic solvent may be heated to 200-. In the temperature range, the metal lithium source can be completely melted, and the metal lithium source is suitable for reacting with the negative active material to carry out pre-lithiation treatment on the negative active material, if the temperature is too low, the metal lithium cannot be completely melted, and if the temperature is too high, the thermal stability of the organic solvent is reduced, so that potential safety hazards are easily caused.

According to the embodiment of the present invention, the metal lithium source dispersion liquid may be stirred while heating to melt the metal lithium source, and a specific stirring rate may be 2000-. Therefore, the stirring speed is high, the molten metal lithium source can be uniformly dispersed into fine particles, and the agglomeration of the raw materials and the products can be effectively avoided. If stirring speed is too small, the metal lithium cannot be fully dispersed, the particle size is too large, and if the stirring speed is too large, the stirring shearing force is too high, so that the stirring equipment is easily damaged.

S200: and adding a negative electrode active material into the metal lithium source particle dispersion liquid, and stirring and reacting for a preset time to obtain the pre-lithiated negative electrode active material.

According to an embodiment of the present invention, the negative active material may include a silicon-based material. In some embodiments, the silicon-based material may include at least one of elemental silicon and silica. Therefore, the pre-lithiation treatment can effectively solve the problem of low first coulombic efficiency of the silicon-based negative electrode active material, and greatly improves the using effect of the silicon-based negative electrode active material.

According to the embodiment of the invention, the pre-lithiation degree of the obtained pre-lithiation negative electrode active material can be flexibly adjusted by adjusting the feeding mass ratio of the negative electrode active material and the metal lithium source so as to meet the use requirements of different use environments. In some embodiments, the charging mass ratio of the negative electrode active material to the lithium metal source may be 1:20 to 1:1 (e.g., 1:20, 1:19, 1:18, 1:17, 1:16, 1:15, 1:14, 1:13, 1:12, 1:11, 1:10, 1:9, 1:8, 1:7, 1:6, 1:5, 1:4, 1:3, 1:2, 1:1, etc.), and may specifically be 1:10 to 1: 5. Within the above proportion range, the pre-lithium amount of the negative electrode active material is suitable, if the proportion is too small, namely the amount of the negative electrode active material is too small, the pre-lithium amount is too high, the lithium precipitation is easily caused when the product is applied to the battery, the cycle stability is influenced, if the proportion is too large, namely the amount of the metal lithium is too small, the pre-lithium amount of the negative electrode active material is too low, and the first effect of the product applied to the battery is not obviously improved.

According to the embodiment of the present invention, after the anode active material is added, the resultant mixture needs to be reacted for a predetermined time under stirring. In some embodiments, after the addition of the negative electrode active material, the temperature is maintained to be the same as the previous step, i.e., the temperature of the reaction process after the addition of the negative electrode active material and the temperature of the dispersion of the lithium metal source particles formed by heating are the same, and the stirring rate during the reaction process may be 100-1000rpm (specifically, 100rpm, 200rpm, 300rpm, 400rpm, 500rpm, 600rpm, 700rpm, 800rpm, 900rpm, 1000rpm, etc.); the reaction time may be 1h to 24h (specifically, 1h, 2h, 5h, 8h, 10h, 12h, 15h, 18h, 20h, 24h, etc.). Within the temperature, stirring speed and time ranges, the negative active material can fully react with the metal lithium source, and a good pre-lithiation effect is realized. If the temperature is too high, the thermal stability of the organic solvent is reduced, and if the temperature is too low, the metal lithium is incompletely melted and the size of dispersed particles is larger; too high stirring speed can cause too large load of stirring equipment and influence the stability of the equipment, too low stirring speed can cause the dispersion uniformity of the metal lithium and the negative electrode active material to be reduced, and reaction efficiency and reaction time influencing the metal lithium and the negative electrode active material to be too short can cause the reaction between the negative electrode active material and the metal lithium to be insufficient and the pre-lithium effect to be reduced; too long a reaction time may result in a decrease in production efficiency.

According to an embodiment of the present invention, the method comprises heating and melting a lithium metal source in an organic solvent, forming a small particle dispersion of the lithium metal source by high-speed stirring, then adding a negative electrode active material, and fully stirring to react to obtain a pre-lithiated negative electrode active material. The method adopts the in-situ reaction of highly dispersed small metal lithium particles and a negative active material, so that the agglomeration of the material is reduced; the contact reaction of the negative active material and lithium is accelerated by high-speed stirring, and the reaction efficiency is improved; and the reaction process is carried out in an organic solvent, so that the interference of the external environment can be isolated, the safety of the preparation process is improved, and the large-scale application is easy.

In another aspect of the invention, the invention provides a prelithiated negative active material. According to embodiments of the present invention, the prelithiated anode active material is prepared by the method described above. The pre-lithiation cathode active material has better electrical property, and the first coulombic efficiency is obviously improved.

According to an embodiment of the present invention, the chemical composition of the prelithiated anode active material is L i_xSiO_y，0<x is not more than 4.4(x is 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.4, etc.), and y is not less than 0 and not more than 1(y is 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, etc.). In some embodiments, 0.4<x<0.8(x may be specifically 0.4, 0.5, 0.6, 0.7, 0.8, etc.). The pre-lithiated negative active material with the chemical composition has high initial coulombic efficiency, and a lithium ion battery with the negative active material has better service performance.

According to an embodiment of the present invention, a ratio of the particle diameter of the pre-lithiated anode active material to the particle diameter of the anode active material is greater than 1 and less than 1.5 (specifically, may be 1.1, 1.2, 1.3, 1.4, 1.15, 1.49, etc.). Thus, after the prelithiation treatment, the particle size increase of the obtained prelithiation negative electrode active material is limited, which indicates that the agglomeration of the material is effectively avoided in the prelithiation process.

In still another aspect of the present invention, the present invention provides a negative electrode sheet. According to an embodiment of the present invention, the negative electrode sheet includes the previously described pre-lithiated negative electrode active material. The negative plate has good electrical properties, and the first coulombic efficiency is obviously improved.

It is understood that, in addition to the pre-lithiated negative electrode active material described above, the negative electrode sheet may further include structures and components of a conventional negative electrode sheet, for example, a current collector (such as a copper foil and the like) and a negative electrode material layer disposed on the current collector, where the negative electrode material layer may include the pre-lithiated negative electrode active material described above, and may further include one or more of a necessary conductive agent and an electrolyte, which may be performed according to a conventional process and are not described in detail herein.

In yet another aspect of the present invention, a lithium ion battery is provided. According to an embodiment of the present invention, the lithium ion battery comprises the pre-lithiated negative active material or the negative electrode sheet described above. The lithium ion battery has rational electrical property, and the first coulombic efficiency is obviously improved.

It is understood that the lithium ion battery may include necessary structures and components of a conventional lithium ion battery, such as a positive electrode sheet, an electrolyte solution or electrolyte, and a housing or packaging structure, etc., in addition to the pre-lithiated negative electrode active material or negative electrode sheet described above, and will not be described in detail herein.

The following describes embodiments of the present invention in detail.