CN114709389B

CN114709389B - Pre-lithiation negative electrode material and preparation method and application thereof

Info

Publication number: CN114709389B
Application number: CN202210325534.6A
Authority: CN
Inventors: 杜宁; 闫允涛; 刘聪; 王振; 程康
Original assignee: Zhejiang Lichen New Material Technology Co ltd
Current assignee: Zhejiang Lichen New Material Technology Co ltd
Priority date: 2022-03-30
Filing date: 2022-03-30
Publication date: 2023-04-18
Anticipated expiration: 2042-03-30
Also published as: CN114709389A

Abstract

The invention discloses a pre-lithiation cathode material and a preparation method and application thereof. The method adopts a synchronous pre-lithium and carbon coating mode, effectively reduces the pH value of the pre-lithiated silica-oxygen composite material, solves the problem of poor cycle performance caused by mismatching of an alkaline material and a binder in the traditional pre-lithium product, simultaneously forms a conductive substance and an SEI substance layer on the surface layer of the material, relieves volume expansion of the material in the using process, and avoids continuous generation and decomposition of an SEI film of a battery material in the using process. The lithium ion battery cathode has the advantages of high first cycle efficiency, good cycle performance, high battery capacity and the like when being applied as a lithium battery cathode.

Description

Pre-lithiation negative electrode material and preparation method and application thereof

Technical Field

The invention relates to the technical field of lithium ion battery cathode materials, in particular to a pre-lithiation cathode material and a preparation method and application thereof.

Background

The lithium ion battery has a wide application prospect in the industries of energy storage, communication, new energy and the like, however, with the continuous expansion of market demands, the performance requirements of the battery are also improved, and the silicon-based negative electrode material, including simple substance silicon, silica material and the like, has the advantages of high energy density, proper discharge platform and the like, is one of the next generation negative electrode materials with potential, and attracts the wide attention of a plurality of enterprises. However, in the application process, the problems that the volume expansion rate of the silicon-based negative electrode material is high, the material particles are easy to break and fall off and the like are found, and the service life of the battery is seriously influenced. In addition, in the first charge and discharge process of the silicon-oxygen material, lithium in the positive electrode is consumed, irreversible lithium silicate is formed, and an SEI film is continuously formed on the surface of the material, so that the first efficiency of the material is reduced, and the capacity is quickly attenuated. The above problems with elemental silicon, silicon oxygen materials limit their wide application.

Based on the first problem, numerous material research personnel continuously try to provide a thought of pre-supplementing lithium, and the first coulombic efficiency of the silicon-oxygen material can be remarkably improved through a pre-lithiation mode. However, the pre-lithiated silica material generally has a high pH value, which results in poor processability of the material, severe gas generation of slurry, low viscosity, and easy occurrence of air holes in the electrode sheet.

Disclosure of Invention

Aiming at the problems in the prior art, the invention discloses a preparation method of a pre-lithiated negative electrode material, which solves the problem of high basicity of the traditional pre-lithiated silica material. Meanwhile, an SEI (solid electrolyte interphase) and conductive substance composite layer is formed on the surface of the material, so that the structural stability of the material is greatly improved. Meanwhile, the method has the advantages of high initial efficiency, good circulation stability, high capacity and the like. The method has the characteristics of good uniformity of the prepared material, low equipment requirement, easy operation and the like. The specific technical scheme is as follows:

a method of preparing a prelithiated anode material, comprising the steps of:

(1) Obtaining lithium-containing powder, silicon oxide powder and a binder;

(2) Mixing the lithium-containing powder, the silicon oxide powder and the binder in the step (1) and then carrying out ball milling to obtain an intermediate product A;

(3) Roasting the intermediate product A under a protective atmosphere or vacuum condition, naturally cooling, crushing and screening to obtain an intermediate product B;

(4) And (3) soaking the intermediate product B in an organic solvent B, and then carrying out solid-liquid separation and vacuum drying to obtain the high-performance pre-lithiation negative electrode material.

Preferably, the preparation process of the lithium-containing powder material is to mix metallic lithium or a lithium-containing compound with a lithium salt in an organic solution, and then dry and dehydrate the mixed product to obtain the lithium-containing powder material; the method specifically comprises the following steps:

1.1 Metallic lithium or a lithium-containing compound is put into the organic solvent A, the solid matter is completely dispersed into the organic solvent A by magnetic stirring,

1.2 Adding a lithium salt solution into the product obtained in the step 1.1, and performing magnetic stirring to uniformly mix the solution components to obtain an intermediate solution A, wherein the volume of the lithium salt solution in the intermediate solution A accounts for 0.5-10%, and the mass of the lithium or lithium-containing compound accounts for 10-70%;

1.3 ) spray drying the product obtained in step 1.3 to obtain lithium-containing powder.

Preferably, the lithium-containing compound is a non-oxidative lithium compound and is one or more of lithium hydride, lithium borohydride, metallic lithium, lithium aluminum hydride, lithium-containing alloy, lithium amide and lithium alkyl; the lithium salt solution is one or more of lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium perchlorate, lithium trifluoromethanesulfonate and lithium hexafluorophosphate; the organic solvent A is any one or combination of more of aromatic hydrocarbon solvents, alcohol solvents and ether solvents; the aromatic hydrocarbon solvent is any one or combination of more of triphenylmethane, diphenylethene, biphenyl, terphenyl and multi-phenyl aliphatic hydrocarbon; the alcohol solvent is any one or combination of methanol, ethanol and glycol; the ether solvent is any one or combination of methyl ether and diethyl ether.

Preferably, the silicon oxide has a chemical formula of SiOx, where 0 </x </1.5; the binder is any one or combination of asphalt, resins, alkanes and saccharides.

Preferably, the mass ratio of the lithium-containing powder, the silicon oxide powder and the binder in the step 2 is (5-78%): (20-80%): (2-15%).

Preferably, the protective atmosphere is selected from one or more of hydrogen, nitrogen, helium, neon and argon; the roasting temperature is 500 to 1000 ℃, and the time is 2 to 15h.

Preferably, the particle size of the intermediate product B obtained after sieving in step 3 is less than 50 μm.

Preferably, the organic solvent B in the step 4 comprises any one or more of alcohols and ether solvents; the alcohol solvent is any one or combination of methanol, ethanol and glycol; the ether solvent is any one or combination of more of methyl ether and ethyl ether; the solid-liquid separation mode comprises one or more of suction filtration, filter pressing, centrifugation and spray drying.

The pre-lithiated negative electrode material is prepared by the preparation method; the pH value of the high-performance battery negative electrode material is 7 to 10; the high-performance battery negative electrode material comprises 30-70% by mass of lithium silicate, 20-60% by mass of silicon, 2-20% by mass of a conductive composite layer and 5-35% by mass of lithium.

An application of a pre-lithiated negative electrode material in the preparation of a lithium ion battery.

Compared with the prior art, the invention has the following beneficial effects: the invention discloses a prelithiation cathode material, which adopts a synchronous prelithiation and carbon coating mode to avoid the traditional two-step prelithiation and carbon coating, improves the treatment efficiency, reduces the energy consumption, simultaneously enables the lithium and carbon coating layers in a silica cathode material to be distributed more uniformly, and can effectively remove residual alkaline substances through cleaning an intermediate product B by an organic solvent, thereby solving the problem of poor cycle performance caused by the mismatching of the alkaline material and a binder in the traditional prelithiation product, simultaneously effectively reducing the pH value of the prelithiation silica composite material and improving the processing performance of the prelithiation silica composite material.

In addition, in the processes of lithium pre-preparation and carbon coating, an SEI substance layer is formed on the surface layer of the material, so that the continuous generation and decomposition of an SEI film in the use process of the battery material are avoided; the consumption of the electrolyte is reduced. The preparation method comprises the steps of pre-lithiation and SEI film formation, wherein metal lithium or a lithium-containing compound is mixed with lithium salt in an organic solution in the preparation process, a layer of SEI film is formed on the surface of lithium in advance, a lithium source is not occupied or is rarely occupied, the influence on subsequent pre-lithiation is small, and the formed films are uniform.

The lithium ion battery assembled by the high-performance pre-lithiation cathode material has excellent first coulombic efficiency, first reversible capacity and high cycle stability. Meanwhile, the method has the advantages of simple preparation process, low equipment requirement, low cost, high operability, high safety and the like.

Drawings

In order to better illustrate the technical solutions of the embodiments of the present invention, the following technical descriptions of the embodiments and comparative examples are illustrated in the accompanying drawings.

FIG. 1 is a charge-discharge curve of the material in example 1 of the present invention.

Fig. 2 is an SEM image of the pre-lithiated silica composite prepared in example 2.

Detailed Description

The present invention will be described in further detail below with reference to examples and comparative examples, but the embodiments of the present invention are not limited thereto.

Example 1

1) Adding lithium powder into a triphenylmethane solution with the concentration of 1mol/L in a dry environment, and uniformly mixing by using a magnetic stirrer, wherein the mass ratio of the lithium powder to the mixed solution is 1:5; and adding lithium tetrafluoroborate into the solution, and fully and uniformly mixing, wherein the lithium tetrafluoroborate accounts for 2% of the mixed solution by mass. And carrying out spray drying on the mixed solution to obtain lithium-containing powder serving as a pre-lithium reagent.

2) And (2) putting the powder, the silicon oxide powder and the binder phenolic resin into a ball mill according to the mass ratio of 25.

3) And 3kg of the mixed powder material is taken and placed in a vacuum furnace to be roasted under the argon atmosphere, the roasting temperature is 750 ℃, the temperature is kept for 5 hours, then the temperature is naturally reduced to the room temperature, the material is taken out, and the material is crushed and screened, so that the pre-lithiation negative electrode material is obtained.

4) And (3) soaking the pre-lithiation negative electrode material into an ether solution for 2 hours, performing solid-liquid separation in a filter pressing mode, and performing vacuum drying on solid particles to obtain the high-performance pre-lithiation negative electrode material.

And (3) performance testing:

pre-lithiating the negative electrode material at high performance: conductive agent sp: dispersant cmc: binder aone =70:15:5:10, mixing materials, stirring uniformly, coating, putting into an oven for drying, taking a pole piece for rolling, punching and weighing the pole piece, putting into a vacuum oven for drying, taking the pole piece into a glove box for making a buckle. And sequentially placing the high-performance pre-lithiation negative electrode material, the diaphragm, the electrolyte and the lithium positive plate to assemble the battery. The cell was discharged from 0.01V to 0.005V at 0.05C-rate and charged at 0.1C-rate. The charging and discharging curve is shown in figure 1.

Example 2

The difference between this example and example 1 is that step 1) of triphenylmethane in this example is replaced by triphenylmethane, and the rest of the preparation method and parameters are the same as those in example 1.

The assembly of the cell and the testing of the electrochemical performance were exactly the same as in example 1.

Scanning electron microscope analysis was performed on the pre-lithiated silica composite material prepared in example 2 to obtain an SEM image thereof shown in fig. 2.

Example 3

The difference between this example and example 1 is that step 1) of the lithium powder in this example is replaced by lithium amide, and the remaining preparation methods and parameters are the same as those in example 1.

Example 4

The difference between the present embodiment and embodiment 1 is that, in the present embodiment, the mass ratio of the lithium powder in step 1) to the mixed solution is 1: the remaining preparation methods and parameters were in accordance with example 1.

Example 5

This example differs from example 1 in that step 1) of the process is replaced by lithium hexafluorophosphate, the remaining preparation and parameters remaining in accordance with example 1.

Example 6

The difference between the present embodiment and embodiment 1 is that in the present embodiment, step 2) is replaced by 50. The remaining preparation methods and parameters were in accordance with example 1.

Example 7

The difference between the present embodiment and embodiment 1 is that in the present embodiment, step 2) is replaced by 20. The remaining preparation methods and parameters were in accordance with example 1.

Example 8

This example differs from example 1 in that the phenolic resin of step 2) is replaced with pitch. The remaining preparation methods and parameters were in accordance with example 1.

Example 9

The difference between this example and example 1 is that step 3) was replaced with 500 ℃ at 750 ℃ and the remaining preparation methods and parameters were the same as those in example 1.

Example 10

This example differs from example 1 in that step 4) of the ethereal solution is replaced by propanol. The remaining preparation methods and parameters were in accordance with example 1.

Comparative example 1

The difference between the present embodiment and embodiment 1 is that, in the present embodiment, the mass ratio of the lithium powder in step 1) to the mixed solution is 5:1, the remaining preparation methods and parameters were in accordance with example 1.

Comparative example 2

The difference between this example and example 1 is that the calcination temperature in step 3) was replaced by 150 ℃ in this example, and the remaining preparation method and parameters were the same as those in example 1.

Comparative example 3

This example is different from example 1 in that step 4) is not performed in this example.

The assembly of the cell and the testing of the electrochemical performance were exactly the same as in example 1. The performance test results of the lithium ion batteries assembled by the above examples and comparative examples are shown in table 1 below.

Comparative example 4

This example differs from example 1 in that in step 1) no lithium tetrafluoroborate is added and the remaining preparation process and parameters remain the same as in example 1.

The assembly of the cell and the testing of the electrochemical performance were exactly the same as in example 1. The performance test results of the lithium ion batteries assembled in the above examples and comparative examples are shown in table 1 below.

Watch (A)

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The present invention can be preferably realized according to the above-described embodiments. It should be noted that, based on the above design, in order to solve the same technical problem, even if some insubstantial changes or modifications are made in the present invention, the spirit of the adopted technical solution is the same as the present invention, and therefore, the technical solution should be within the scope of the present invention.

Claims

1. A method for preparing a prelithiated anode material, comprising: the method comprises the following steps:

(1) Obtaining lithium-containing powder, silicon oxide powder and a binder;

(2) Mixing the lithium-containing powder, the silicon oxide powder and the binder in the step (1) and then carrying out ball milling to obtain an intermediate product A; the mass ratio of the lithium-containing powder material to the silicon oxide powder to the binder is (5-78%): (20-80%): (2-15%);

(3) Roasting the intermediate product A under a protective atmosphere or vacuum condition, naturally cooling, crushing and screening to obtain an intermediate product B; the roasting temperature is 500 to 1000 ℃, and the time is 2 to 15h;

(4) Immersing the intermediate product B in an organic solvent B, and then carrying out solid-liquid separation and vacuum drying to obtain a high-performance pre-lithiation negative electrode material;

the preparation process of the lithium-containing powder comprises the steps of mixing metal lithium and lithium salt in an organic solution, and then drying and dehydrating the mixed product to obtain the lithium-containing powder; the method specifically comprises the following steps:

1.1 Metal lithium is put into the organic solvent A, the solid matter is completely dispersed into the organic solvent A by magnetic stirring,

1.2 Adding a lithium salt solution into the product obtained in the step 1.1, and performing magnetic stirring to uniformly mix the solution components to obtain an intermediate solution A, wherein the volume of the lithium salt solution in the intermediate solution A accounts for 0.5-10%, and the mass of the metal lithium accounts for 10-70%;

1.3 ) spray drying the product obtained in step 1.2 to obtain lithium-containing powder.

2. The method of making a prelithiated anode material of claim 1, wherein: the lithium salt in the lithium salt solution is one or more of lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium perchlorate, lithium trifluoromethanesulfonate and lithium hexafluorophosphate;

the organic solvent A is any one or combination of aromatic hydrocarbon, alcohol and ether solvents; the aromatic hydrocarbon solvent is any one or combination of more of triphenylmethane, diphenylethene, biphenyl, terphenyl and multi-phenyl aliphatic hydrocarbon; the alcohol solvent is any one or combination of methanol, ethanol and glycol; the ether solvent is any one or combination of methyl ether and diethyl ether.

3. The method of preparing a prelithiated anode material according to claim 1, wherein: the silicon oxide has a chemical formula of SiOx, wherein 0-x-1.5; the binder is any one or combination of asphalt, resins, alkanes and saccharides.

4. The method of preparing a prelithiated anode material according to claim 1, wherein:

the protective atmosphere is selected from one or more of hydrogen, nitrogen, helium, neon and argon.

5. The method of making a prelithiated anode material of claim 1, wherein:

the granularity of the intermediate product B obtained after screening in the step 3 is less than 50 mu m.

6. The method of preparing a prelithiated anode material according to claim 1, wherein:

the organic solvent B in the step 4 comprises any one or a combination of more of alcohols and ether solvents; the alcohol solvent is any one or combination of methanol, ethanol and glycol; the ether solvent is any one or combination of more of methyl ether and ethyl ether;

the solid-liquid separation mode comprises one or more of suction filtration, filter pressing, centrifugation and spray drying.

7. A prelithiated anode material, characterized in that: the prelithiated negative electrode material is prepared by the preparation method of any one of claims 1 to 6.

8. Use of the prelithiated anode material of claim 7 in the preparation of a lithium ion battery.