A composite LiCoO2 cathode material with lithium supplementation function, its preparation method and application

Abstract

This invention provides a composite LiCoO2 cathode material with lithium replenishment function, its preparation method, and its application. An in-situ synthesis method is used to generate a lithium replenishing material Li6CoO4 on the surface of the LiCoO2 cathode material to achieve the purpose of lithium replenishment in lithium-ion batteries. Its expression is (1-x)LiCoO2@xLi6CoO4. A carbothermal reduction method is used to remove Co from the surface layer of the original LiCoO2 cathode material. 3+ Restored to Co 2+ A Li6CoO4 lithium replenishment layer is generated in situ on the surface of LiCoO2 cathode material through lithium addition and high-temperature calcination. The prepared composite cathode material has advantages such as uniform particle distribution, high discharge specific capacity, good cycle stability, and high consistency of material performance after lithium replenishment. In-situ lithium replenishment of lithium-ion batteries using this method has advantages such as low cost, precise lithium replenishment amount, and high safety. Furthermore, this synthesis method is simple, reproducible, and compatible with existing lithium-ion battery production processes, requiring no additional lithium replenishment step, making it suitable for widespread application.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery cathode lithium replenishment materials, specifically a composite LiCoO2 cathode material with lithium replenishment function. Background Technology

[0002] With the development of the times, the development of new energy sources has become a trend. Among them, lithium-ion battery technology has become the most widely used and mature power source for portable electronic devices. As people's living standards improve, the demand for electrode materials with higher energy density, higher performance, and higher capacity is increasing daily. Currently, high-capacity anode materials are widely used, but during their use, due to the significant volume effect, side reactions inevitably occur at the electrode material / electrolyte interface, consuming a large amount of lithium ions in the battery, resulting in a decrease in the actual capacity and performance loss. In view of this, researchers have used positive electrode lithium replenishment additives to provide more active lithium to lithium-ion batteries, thereby compensating for the active lithium ions consumed by side reactions and SEI film formation, and thus achieving a significant increase in the actual usable reversible capacity, energy density, and capacity retention of the lithium-ion battery itself. Summary of the Invention

[0003] This invention provides a composite LiCoO2 cathode material with lithium replenishment function and its preparation method, aiming to replenish lithium in lithium-ion batteries using LiCoO2 cathodes, thereby improving the performance of lithium-ion batteries. The preparation method has advantages such as ease of operation, low cost, and compatibility of the lithium replenishment process with existing lithium-ion battery production processes. After performing the lithium replenishment function, it does not affect the performance of the original cathode material. Therefore, under the same active material mass conditions, the composite LiCoO2 cathode material with lithium replenishment function described in this invention can achieve a higher capacity than ordinary LiCoO2 cathodes.

[0004] In this invention, the composite cathode material can be represented as: (1-x)LiCoO2@xLi6CoO4, where the mass fraction of Li6CoO4 in the composite material is 0 < x ≤ 0.15. The Li6CoO4 material is located on the surface of the LiCoO2 particles, forming a relatively complete and uniform coating on the LiCoO2 particles.

[0005] According to another aspect of the present invention, a method for preparing the above-described material is provided, wherein a lithium-supplementing material of Li6CoO4 is generated in situ on the surface of LiCoO2 particles under strictly controlled temperature conditions through in-situ synthesis; the specific steps are as follows:

[0006] 1) Mix the lithium source, carbon source, and LiCoO2 in a specific ratio to form a mixture. The lithium source is one or more of LiOH, CH3COOLi, and Li2CO3. The carbon source is one or more of carbon black, graphite, glucose, sucrose, or starch.

[0007] 2) Place the above mixture in a tube furnace and heat it to 600-900℃ under an atmosphere of N2, Ar, or H2 / Ar mixture, and hold it at that temperature for 10-30 hours, so that the Co on the surface of the LiCoO2 particles... 3+ The element reacts with the lithium source under the reduction of the carbon source to form a lithium-replenishing coating layer of Li6CoO4.

[0008] 3) After natural cooling, the composite LiCoO2 cathode material with lithium replenishment function described in this invention can be obtained.

[0009] Furthermore, the application of the composite LiCoO2 cathode material with lithium replenishment function described in this invention allows the composite LiCoO2 cathode material described in this invention to replace the ordinary LiCoO2 cathode in the preparation of lithium-ion batteries. Attached Figure Description

[0010] Figure 1 This is a schematic diagram comparing the cycle performance of the in-situ lithium-supplemented cathode material prepared in Example 1 of this patent with that of ordinary LiCoO2 material.

[0011] Figure 2 This is a schematic diagram comparing the cycle performance of the in-situ lithium-supplemented cathode material prepared in Example 2 of this patent with that of ordinary LiCoO2 material.

[0012] Figure 3 This is a schematic diagram comparing the first charge-discharge cycle of the in-situ lithium-added cathode material prepared in Example 3 of this patent with that of ordinary LiCoO2 material.

[0013] Figure 4 The image shows the XRD pattern of the in-situ lithium-added cathode material prepared in Example 4 of this patent.

[0014] Figure 5 This is a comparison chart of the cycle performance of the in-situ lithium-supplemented cathode material prepared in Example 4 of this patent. Detailed Implementation Example 1

[0015] (1) Mix LiCoO2:LiOH:carbon black in a molar ratio of 400:5:1 and grind for 15 minutes to obtain a uniform mixture.

[0016] (2) The mixture was placed in a tube furnace and heated to 900 degrees Celsius in an H2 / Ar atmosphere for 30 hours. After natural cooling, the product 0.99LiCoO2@0.01Li6CoO4 was obtained.

[0017] (3) The product 0.99LiCoO2@0.01Li6CoO4 was used as the positive electrode active material. The prepared 0.99LiCoO2@0.01Li6CoO4 material:Super-P:PVDF=8:1:1 was stirred and mixed evenly to form a slurry. The slurry was coated on aluminum foil using a coating machine to form an electrode sheet. The electrode sheet was placed in a 60℃ oven and baked for 8 hours, and then placed in a 120℃ vacuum oven and baked for 4 hours.

[0018] (4) Under the same conditions, the 0.99LiCoO2@0.01Li6CoO4 material prepared in this example and ordinary LiCoO2 material were matched with graphite anodes and assembled into lithium-ion batteries for electrochemical performance comparison tests. The results are shown in the appendix. Figure 1 As shown, the material prepared in this example exhibits significantly higher discharge capacity and excellent cycle performance. Example 2

[0019] (1) Mix LiCoO2:CH3COOLi:graphite in a molar ratio of 400:15:3 and grind for 15 minutes to obtain a homogeneous mixture.

[0020] (2) The mixture was placed in a tube furnace and heated to 800 degrees Celsius in a N2 atmosphere for 20 hours. After natural cooling, the product 0.97LiCoO2@0.03Li6CoO4 was obtained.

[0021] (3) The product 0.97LiCoO2@0.03Li6CoO4 was used as the positive electrode active material. The prepared 0.97LiCoO2@0.03Li6CoO4 material:Super-P:PVDF=8:1:1 was homogenized and coated. After coating, the electrode was first placed in a 60℃ oven to dry for 8 hours and then placed in a 120℃ vacuum oven to stand for 4 hours.

[0022] (4) Under the same conditions, the 0.97LiCoO2@0.03Li6CoO4 material prepared in this example and ordinary LiCoO2 material were matched with graphite anodes and assembled into lithium-ion batteries for electrochemical performance comparison tests. The results are shown in the appendix. Figure 2 As shown, the material prepared in this example exhibits significantly superior discharge capacity and cycle performance. Example 3

[0023] (1) Mix LiCoO2:CH3COOLi:glucose and starch in a molar ratio of 80:5:1 and grind for 15 minutes to obtain a homogeneous mixture.

[0024] (2) The mixture was placed in a tube furnace and heated to 700 degrees Celsius in an Ar atmosphere for 15 hours. After natural cooling, the product 0.95LiCoO2@0.05Li6CoO4 was obtained.

[0025] (3) The product 0.95LiCoO2@0.05Li6CoO4 was used as the positive electrode active material. The prepared 0.95LiCoO2@0.05Li6CoO4 material:Super-P:PVDF=8:1:1 was homogenized and coated. After coating, the electrode was first placed in a 60℃ oven to dry for 8 hours and then placed in a 120℃ vacuum oven to stand for 4 hours.

[0026] (4) Under the same conditions, the 0.97LiCoO2@0.03Li6CoO4 material prepared in this example and ordinary LiCoO2 material were matched with graphite anodes and assembled into lithium-ion batteries for electrochemical performance comparison tests. The results are shown in the appendix. Figure 3 As shown, the material prepared in this example exhibits a significantly higher discharge capacity. Example 4

[0027] (1) Mix LiCoO2:Li2CO3:glucose and sucrose in a molar ratio of 80:5:2 and grind for 15 minutes to obtain a homogeneous mixture.

[0028] (2) The mixture was placed in a tube furnace and heated to 600 degrees Celsius in an H2 / Ar atmosphere for 10 hours. After natural cooling, the product 0.9LiCoO2@0.1Li6CoO4 was obtained. The obtained product was subjected to XRD analysis, and the results are shown in the attached figure. Figure 4 As shown in the figure, it can be seen that a composite material of LiCoO2 and Li6CoO4 was successfully prepared in this example.

[0029] (3) The product 0.9LiCoO2@0.1Li6CoO4 was used as the positive electrode active material. The prepared 0.9LiCoO2@0.1Li6CoO4 material:Super-P:PVDF=8:1:1 was homogenized and coated. After coating, the electrode was first placed in a 60℃ oven to dry for 8 hours and then placed in a 120℃ vacuum oven to stand for 4 hours.

[0030] (4) Under the same conditions, the 0.9LiCoO2@0.1Li6CoO4 material prepared in this example and ordinary LiCoO2 material were matched with graphite anodes and assembled into lithium-ion batteries for electrochemical performance comparison tests. The results are attached. Figure 5 As shown, the material prepared in this example exhibits significantly higher discharge capacity and superior cycle performance.

Claims

1. A method for preparing a composite LiCoO2 cathode material with lithium supplementation function, wherein the composite LiCoO2 cathode material is expressed as (1-x)LiCoO2@xLi6CoO4, 0 < x ≤ 0.15; characterized in that: 1) Mix the lithium source, carbon source, and LiCoO2 in a specific ratio to form a mixture; 2) The mixture is placed in a tube furnace and heated to 600-900°C under inert or reducing atmosphere for 10-30 hours, so that the Co in the surface layer of the LiCoO2 particles is reduced 3+ The element reacts with the lithium source under the reduction of the carbon source to form a Li6CoO4 lithium supplement coating layer; 3) After natural cooling, the composite LiCoO2 cathode material with lithium replenishment function is obtained.

2. The method of claim 1, wherein: The lithium source is one or more of LiOH, CH3COOLi and Li2CO3.

3. The method as described in claim 1 or 2, characterized in that: The carbon source is one or more of carbon black, graphite, glucose, sucrose, or starch.

4. The method as described in claim 3, characterized in that: The inert or reducing atmosphere is N2, Ar, or a mixture of H2 / Ar.

Images