A high-voltage composite cathode material for lithium-ion batteries and its preparation method

Abstract

This invention belongs to the field of lithium-ion battery raw materials, specifically relating to a high-voltage composite cathode material for lithium-ion batteries and its preparation method. The composite cathode material consists of a high-voltage cathode material, a reducing agent, and a catalyst. The method includes the following steps: first, uniformly mixing the high-voltage cathode material and the catalyst, followed by heat treatment to obtain a composite material of the cathode material and the catalyst; then, adding the reducing agent and undergoing heat treatment to obtain the high-voltage composite cathode material for lithium-ion batteries. Through this method, the surface of the cathode material is modified with a catalyst, which improves the structural stability of the cathode material under high voltage; the reducing agent is composited on the surface of the catalyst, fixing the free oxygen generated by the cathode material in situ, alleviating battery swelling, and further improving the cycle stability and safety of the battery; moreover, the preparation process is simple, the raw materials are inexpensive and readily available, the production cost is low, and it is easy to industrialize and promote.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery raw materials, specifically relating to a high-voltage composite cathode material for lithium-ion batteries and its preparation method. Background Technology

[0002] With the rapid development of consumer electronics and electric vehicles, higher demands are being placed on lithium-ion batteries to achieve longer standby times and driving ranges: high energy density, long cycle life, and good safety. Using high-specific-capacity, high-voltage cathode materials is the most effective way to improve battery energy density. However, during cycling, high-specific-capacity, high-voltage cathode materials are often accompanied by changes in crystal structure, dissolution of transition metal ions, and oxygen evolution, causing material particle breakage, decomposition, and detachment, leading to rapid capacity decay and safety issues. Surface modification of cathode materials is typically performed to suppress irreversible changes, improve structural stability, and thus enhance battery cycle life and safety.

[0003] This invention improves the structural stability of high-voltage cathode materials by modifying the surface of the cathode material with catalytic materials. On the other hand, it utilizes the oxygen released by the adsorption of reducing materials to form a stable interface layer, further improving the stability of the material, alleviating the battery swelling phenomenon, and thus improving the cycle stability and safety of the battery. Summary of the Invention

[0004] The purpose of this invention is to solve the problems of cycle stability and safety of high-voltage lithium-ion batteries, and to provide a high-voltage composite cathode material for lithium-ion batteries and its preparation method.

[0005] The concept of this invention is as follows: on the one hand, catalytic material is modified on the surface of high-voltage cathode material to improve the structural stability of cathode material; on the other hand, reducing material is compounded on the surface of catalytic material to adsorb oxygen released from cathode material and form a stable interface layer, thereby further improving the stability of material, alleviating battery swelling phenomenon, and thus improving the cycle stability and safety of battery.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] In a first aspect, the present invention provides a method for preparing a high-voltage composite cathode material for lithium-ion batteries, wherein the composite cathode material is composed of a high-voltage cathode material, a reducing material, and a catalytic material.

[0008] The high-voltage cathode material includes at least one of the following: lithium iron pyrophosphate, lithium iron manganese pyrophosphate, lithium manganese pyrophosphate, lithium cobalt pyrophosphate, lithium manganese oxide, lithium nickel manganese oxide, lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and lithium-rich oxide.

[0009] The reducing materials include at least one material selected from elemental sulfur, lithium sulfide, sodium sulfide, potassium sulfide, zinc sulfide, magnesium sulfide, ferrous sulfide, manganese sulfide, cobalt sulfide, nickel sulfide, elemental phosphorus, zinc phosphide, magnesium phosphide, iron phosphide, manganese phosphide, cobalt phosphide, and nickel phosphide.

[0010] The catalytic material includes at least one material selected from ferrous oxide, manganese oxide, cobalt oxide, nickel oxide, carbon nanotubes, and graphene.

[0011] The molar proportions of the high-voltage cathode material, reducing material, and catalyst material are 95–99 parts, 0.01–5 parts, and 0.01–1 parts, respectively.

[0012] Specifically, the steps include the following:

[0013] Step 1: After mixing the high-voltage cathode material and the catalyst material evenly according to the specified ratio, the mixture is heat-treated at 300-600℃ under an inert gas atmosphere to obtain composite material S1;

[0014] Step 2: Add reducing material to composite material S1 according to the specified ratio, mix evenly, and heat-treat at 100-300℃ under an inert gas atmosphere to obtain a high-voltage composite cathode material for lithium-ion batteries.

[0015] Preferably, the inert gas is nitrogen or argon.

[0016] Preferably, the heat treatment time for steps one and two is 0.5 to 10 hours.

[0017] Preferably, the lithium nickel cobalt manganese oxide material includes LiNi 0.90 Co 0.05 Mn 0.05 O2.

[0018] Preferably, the lithium-rich oxide comprises a lithium-rich manganese-based material.

[0019] Furthermore, the lithium-rich manganese-based material includes Li 1.3 Ni 0.15 Co 0.2 Mn 0.65 O 2.3 .

[0020] In a second aspect, the present invention provides a high-voltage composite cathode material, which is prepared by the method described in the first aspect.

[0021] Preferably, the structure of the composite cathode material is as follows: the high-voltage cathode material is located inside the composite cathode material, and the reducing material and the catalytic material are coated and attached to the outside of the high-voltage cathode material.

[0022] Furthermore, the coating thickness of the raw materials and catalysts is 1–10 nm.

[0023] Thirdly, the present invention provides the use of the high-voltage composite cathode material described in the second aspect in the preparation of lithium-ion batteries, wherein the composite cathode material is used to prepare the cathode of lithium-ion batteries.

[0024] The beneficial effects of this invention are as follows: This method prepares a high-voltage composite cathode material for lithium-ion batteries, which has the following advantages:

[0025] (1) Modifying the surface of the cathode material with catalytic materials can improve the structural stability of the cathode material under high voltage;

[0026] (2) Introducing reducing materials on the surface of the catalyst material to fix the free oxygen generated by the positive electrode material under high pressure in situ, forming a stable interface layer, alleviating the battery swelling phenomenon, and further improving the cycle stability and safety of the battery.

[0027] (3) The high-voltage composite cathode material prepared for lithium-ion batteries has a simple preparation process, low production cost, and is easy to industrialize and promote.

[0028] (4) The high-voltage composite cathode material prepared for lithium-ion batteries has good adaptability to existing lithium-ion battery preparation processes, requires no major modifications, and is easy to promote. Attached Figure Description

[0029] Figure 1 SEM image of the prepared high-voltage composite cathode material Detailed Implementation

[0030] The present invention will be further described below with reference to the accompanying drawings and examples.

[0031] Example 1

[0032] The steps for preparing high-voltage composite cathode materials for lithium-ion batteries are as follows:

[0033] Step 1: Preparation of composite materials of high-voltage cathode material and catalytic material

[0034] 0.1 mol of lithium nickel cobalt manganese oxide (LiNi) 0.90 Co 0.05 Mn 0.05O2) and 0.01 mol of cobalt oxide are mixed evenly to allow cobalt oxide to adhere to the surface of lithium nickel cobalt manganese oxide. Under a nitrogen atmosphere, the mixture is heat-treated at 400℃ for 3 hours to obtain a composite material of lithium nickel cobalt manganese oxide and cobalt oxide.

[0035] Step 2: Preparation of high-voltage composite cathode materials for lithium-ion batteries

[0036] The prepared lithium nickel cobalt manganese oxide and cobalt oxide composite material was mixed with 0.03 mol of elemental phosphorus and heat-treated at 110℃ for 3 h to disperse elemental phosphorus on the surface of the lithium nickel cobalt manganese oxide and cobalt oxide composite material, thus obtaining a high-voltage composite cathode material for lithium-ion batteries.

[0037] SEM image of the prepared high-voltage composite cathode material is shown below. Figure 1 As shown, the catalyst and reducing material are attached to the surface of the high-voltage cathode material.

[0038] Example 2

[0039] The steps for preparing high-voltage composite cathode materials for lithium-ion batteries are as follows:

[0040] Step 1: Preparation of composite materials of high-voltage cathode material and catalytic material

[0041] 0.1 mol of lithium-rich manganese-based material (Li 1.3 Ni 0.15 Co 0.2 Mn 0.65 O 2.3 0.01 mol of ferrous oxide and 0.01 mol of graphene are mixed evenly to allow the ferrous oxide and graphene to adhere to the surface of the lithium-rich manganese-based material. The mixture is then heat-treated at 500°C for 1 hour under an argon atmosphere to obtain a composite material of lithium-rich manganese-based material, ferrous oxide, and graphene.

[0042] Step 2: Preparation of high-voltage composite cathode materials for lithium-ion batteries

[0043] The prepared lithium-rich manganese-based material, ferrous oxide, and graphene composite material were mixed with 0.03 mol of iron phosphide and heat-treated at 260℃ for 3 hours to disperse iron phosphide on the surface of the lithium-rich manganese-based material, ferrous oxide, and graphene composite material, thus obtaining a high-voltage composite cathode material for lithium-ion batteries.

[0044] The prepared high-voltage composite cathode material was used as the cathode to assemble a coin cell lithium-ion battery. In the constant current charge-discharge test at 0.1C within the voltage range of 2 to 4.8V, the initial discharge specific capacity reached 310mAh / g, and the capacity retention rate after 200 constant current charge-discharge cycles at 0.5C reached more than 92%, demonstrating excellent electrochemical performance.

Claims

1. A method for preparing a high-voltage composite cathode material for lithium-ion batteries, characterized in that, The composite cathode material is composed of a high-voltage cathode material, a reducing material, and a catalytic material; The high-voltage cathode material includes at least one of the following: lithium iron pyrophosphate, lithium iron manganese pyrophosphate, lithium manganese pyrophosphate, lithium cobalt pyrophosphate, lithium manganese oxide, lithium nickel manganese oxide, lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and lithium-rich oxide. The reducing materials include at least one material selected from elemental sulfur, lithium sulfide, sodium sulfide, potassium sulfide, zinc sulfide, magnesium sulfide, ferrous sulfide, manganese sulfide, cobalt sulfide, nickel sulfide, elemental phosphorus, zinc phosphide, magnesium phosphide, iron phosphide, manganese phosphide, cobalt phosphide, and nickel phosphide. The catalytic material includes at least one material selected from ferrous oxide, manganese oxide, cobalt oxide, nickel oxide, carbon nanotubes, and graphene. The molar proportions of the high-voltage cathode material, reducing material, and catalyst material are 95-99 parts, 0.01-5 parts, and 0.01-1 parts, respectively. Specifically, the steps include the following: Step 1: After mixing the high-voltage cathode material and the catalyst material evenly according to the specified ratio, the mixture is heat-treated at 300~600℃ under an inert gas atmosphere to obtain composite material S1; Step 2: Add reducing material to composite material S1 according to the specified ratio, mix evenly, and heat-treat at 100~300℃ under an inert gas atmosphere to obtain a high-voltage composite cathode material for lithium-ion batteries. The structure of the composite cathode material is as follows: the high-voltage cathode material is located inside the composite cathode material, and the reducing material and the catalytic material are coated and attached to the outside of the high-voltage cathode material.

2. The method for preparing high-voltage composite cathode material for lithium-ion batteries according to claim 1, characterized in that, The inert gas is nitrogen or argon.

3. The method for preparing a high-voltage composite cathode material for lithium-ion batteries according to claim 1, characterized in that, The heat treatment time for steps one and two is 0.5 to 10 hours.

4. The method for preparing the high-voltage composite cathode material for lithium-ion batteries according to claim 1, characterized in that, The lithium nickel cobalt manganese oxide material includes LiNi 0.90 Co 0.05 Mn 0.05 O2.

5. The method for preparing a high-voltage composite cathode material for lithium-ion batteries according to claim 1, characterized in that, The lithium-rich oxide includes lithium-rich manganese-based materials.

6. The method for preparing a high-voltage composite cathode material for lithium-ion batteries according to claim 5, characterized in that, The lithium-rich manganese-based material includes Li 1.3 Ni 0.15 Co 0.2 Mn 0.65 O 2.3 .

7. A high-voltage composite cathode material, prepared by the method described in any one of claims 1 to 6.

8. The high-voltage composite cathode material according to claim 7, characterized in that, The structure of the composite cathode material is as follows: the high-voltage cathode material is located inside the composite cathode material, and the reducing material and the catalytic material are coated and attached to the outside of the high-voltage cathode material.

9. The high-voltage composite cathode material according to claim 8, characterized in that, The coating thickness of the raw materials and catalysts is 1~10 nm.

10. The use of the high-voltage composite cathode material according to any one of claims 7 to 9 in the preparation of lithium-ion batteries, characterized in that, The composite cathode material is used to prepare the cathode of a lithium-ion battery.

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