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

Abstract

This invention belongs to the field of lithium-ion battery technology, specifically relating to a composite cathode material for lithium-ion batteries and its preparation method. The composite cathode material consists of three parts: a cathode matrix material, a lithium replenishment material, and a catalyst material. The preparation method is as follows: (1) preparing a composite material of the cathode matrix material and the lithium replenishment material in situ; (2) dispersing the catalyst material on the surface of the composite material and forming a stable interface layer between the catalyst material and the lithium replenishment material. Through the method of this invention: the lithium replenishment material has both surface modification of the cathode matrix material and lithium replenishment of the negative electrode, simultaneously improving the battery's initial efficiency and cycle stability; introducing the catalyst material onto the surface of the lithium replenishment material in situ fixes the free O generated by the Li release from the lithium replenishment material, alleviating the battery swelling phenomenon and further improving the battery's cycle stability and safety; moreover, the preparation process is simple, the raw materials are cheap and readily available, the production cost is low, and it is easy to promote industrial production.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to a 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. To improve battery energy density, high-specific-capacity cathode and anode materials are commonly used. However, during cycling, high-specific-capacity cathode materials often undergo crystal structure changes and the precipitation of transition metal ions, causing particle breakage, decomposition, and shedding, leading to rapid capacity decay. Surface modification of the cathode material is typically used to suppress irreversible changes and improve structural stability, thereby enhancing battery cycle life and safety. Currently, high-energy-density lithium-ion batteries mostly use silicon-based anode materials. However, during charging and discharging, due to the formation of the SEI film, the initial irreversible capacity of silicon-based anodes exceeds 20%, severely reducing the battery's energy density. Therefore, researchers are using lithium replenishment technology to compensate for lithium loss during the initial charging process, thereby improving the energy density and cycle life of lithium-ion batteries.

[0003] Surface modification of cathode materials is typically achieved through ion doping and surface coating. Lithium replenishment technology is divided into negative electrode lithium replenishment and positive electrode lithium replenishment. Negative electrode lithium replenishment materials are extremely unstable in air, and the technology is complex, has stringent environmental requirements, and necessitates significant modifications to existing production lines, making widespread application difficult in the short term. Positive electrode lithium replenishment materials are mostly lithium-rich compounds, which are relatively stable, and the technology is simpler, requiring minimal changes to existing battery manufacturing processes, making it easier to implement. Commonly used positive electrode lithium replenishing agents are mostly lithium-rich materials, in Li... + As the battery detaches, free oxygen is released, causing the battery to swell, leading to a decrease in battery capacity and a series of safety issues.

[0004] Therefore, it is necessary to develop a composite cathode material for lithium-ion batteries to overcome the above-mentioned technical problems. Summary of the Invention

[0005] The purpose of this invention is to solve the cycle stability and safety problems of high-energy-density lithium-ion batteries, and to provide a composite cathode material for lithium-ion batteries and its preparation method. On the one hand, a composite material of lithium-ion battery cathode matrix material and lithium replenishment material is prepared in situ. The lithium replenishment material has the dual functions of surface modification of cathode matrix material and lithium replenishment of negative electrode, which not only stabilizes the structure of cathode material, but also improves battery first efficiency and cycle stability. On the other hand, a catalytic material is introduced on the surface of the lithium replenishment material to fix the free O generated by the desorption of Li from the lithium replenishment material in situ, alleviate the battery swelling phenomenon, and further improve the cycle stability and safety of the 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 composite cathode material for lithium-ion batteries, the composite cathode material comprising a cathode matrix material, a lithium supplementation material, and a catalyst material;

[0008] The positive electrode substrate material includes at least one of the following materials: lithium iron phosphate, lithium iron manganese phosphate, lithium cobalt phosphate, 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 lithium replenishment material includes at least one of the following: lithium silicate-rich material, lithium iron ferrite-rich material, lithium niobate-rich material, lithium zirconate-rich material, and lithium nickelate-rich material.

[0010] The catalytic material comprises at least one material selected from iron oxide, manganese oxide, cobalt oxide, nickel oxide, iron sulfide, manganese sulfide, cobalt sulfide, nickel sulfide, iron phosphide, manganese phosphide, cobalt phosphide, nickel phosphide, elemental sulfur, elemental phosphorus, graphene, and carbon nanotubes.

[0011] In the composite cathode material, the molar proportions of the cathode matrix material, the lithium supplementation material, and the catalyst material are 80–98 parts, 0.01–19 parts, and 0.001–1 parts, respectively.

[0012] The cathode substrate material is located inside the composite cathode material, while the lithium replenishment material and catalytic material are coated on the outside of the cathode substrate material.

[0013] Preferably, the particle size of the composite cathode material is 1-20 μm, and the coating thickness of the lithium replenishment material and the catalyst material is 1-30 nm.

[0014] Preferably, the positive electrode substrate material is lithium nickel cobalt manganese oxide, the lithium replenishment material is lithium silicate rich material, and the catalyst material is a mixture of iron sulfide and iron oxide.

[0015] Preferably, the positive electrode substrate material is lithium cobalt oxide, the lithium supplement material is lithium iron phosphate, and the catalyst material is a mixture of phosphorus and cobalt phosphide.

[0016] Secondly, the present invention provides a method for preparing the composite cathode material for lithium-ion batteries as described in the first aspect, the specific steps of which are as follows:

[0017] Preparation of S1 cathode matrix material and lithium supplementation material composite material

[0018] The positive electrode matrix material precursor and the lithium supplement material precursor are mixed evenly in a certain proportion, so that the lithium supplement material precursor coats the surface of the positive electrode matrix material precursor; a lithium source is added, and after heat treatment at 500-1000℃, a composite material M1 of positive electrode matrix material and lithium supplement material is obtained.

[0019] The precursor for the positive electrode substrate is at least one of the following: iron phosphate, manganese iron phosphate, cobalt phosphate, manganese oxide, nickel manganese oxide, cobalt oxide, nickel cobalt manganese oxide, nickel cobalt aluminum oxide, and lithium-rich oxide; the precursor for the lithium supplement material is at least one of the following: silicon dioxide, iron oxide, niobium oxide, zirconium oxide, and nickel oxide; and the lithium source is at least one of the following: lithium hydroxide, lithium carbonate, lithium acetate, and lithium nitrate.

[0020] The molar ratio of the cathode substrate precursor to the lithium supplement precursor is 160:1 to 4:1; the molar ratio of the sum of the molar amounts of the cathode substrate precursor and the lithium supplement precursor to the molar amount of the lithium source is 1:1.05 to 1.5.

[0021] S2 is used in the preparation of composite cathode materials for lithium-ion batteries.

[0022] The prepared composite material M1 is mixed with the catalyst material in a certain proportion and then heat-treated at 100-500℃ to disperse the catalyst material on the surface of the composite material M1 and form a stable interface layer with the lithium supplement material, thus obtaining a composite cathode material for lithium-ion batteries.

[0023] The molar ratio of composite material M1 to catalytic material is 1:0.001 to 1:1.

[0024] Preferably, the particle size of the positive electrode matrix material precursor is 1-20 μm, the particle size of the lithium supplementation material precursor is 0.01-0.2 μm, and the particle size of the catalyst material is 0.01-0.2 μm.

[0025] Preferably, the heat treatment time in step 1 is 1 to 10 hours, and the heat treatment time in step 2 is 1 to 20 hours.

[0026] Thirdly, the present invention provides an application of the composite cathode material described in the first aspect in the preparation of lithium-ion batteries.

[0027] Preferably, the composite cathode material is used to prepare the cathode of a lithium-ion battery.

[0028] Fourthly, the present invention provides a lithium battery, wherein the positive electrode of the lithium-ion battery is the composite positive electrode material described in the first aspect, and the negative electrode is a carbon-silicon material.

[0029] The beneficial effects of this invention: This method prepares a composite cathode material for lithium-ion batteries, which has the following advantages:

[0030] (1) A composite material of positive electrode matrix material and lithium replenishment material for lithium-ion battery was prepared in situ. The lithium replenishment material has the dual functions of surface modification of positive electrode matrix material and lithium replenishment of negative electrode. It not only stabilizes the structure of positive electrode material, but also improves the first efficiency and cycle stability of battery.

[0031] (2) Catalytic materials are introduced on the surface of the lithium replenishment material to fix the free O generated by the Li release from the lithium replenishment material in situ, alleviate the battery swelling phenomenon, and further improve the cycle stability and safety of the battery.

[0032] (3) The composite cathode material prepared for lithium-ion batteries has a simple preparation process, low production cost, and is easy to industrialize and promote.

[0033] (4) The composite cathode material prepared for lithium-ion batteries is well adapted to the existing lithium-ion battery preparation process, requires no major modifications, and is easy to promote. Attached Figure Description

[0034] Figure 1 Schematic diagram of composite cathode material

[0035] Wherein, 1 represents the positive electrode substrate material, 2 represents the interface layer between the positive electrode substrate material and the lithium replenishment material, 3 represents the lithium replenishment material coating layer, and 4 represents the surface catalyst material;

[0036] Figure 2 SEM image of the prepared composite cathode material

[0037] Figure 3 The composite cathode material and silicon-carbon material were used to assemble a battery, and the battery cycle curve at 0.2C was shown in the figure.

[0038] In the figure: the vertical axis represents the discharge capacity in Ah; the horizontal axis represents the number of cycles in cycles. Detailed Implementation

[0039] The present invention will be further described below with reference to the accompanying drawings and examples.

[0040] Example 1

[0041] The steps for preparing composite cathode materials for lithium-ion batteries are as follows:

[0042] Step 1: Preparation of composite materials of positive electrode matrix material and lithium supplementation material

[0043] 0.2 mol of nickel cobalt manganese oxide (10 μm) and 0.01 mol of silicon dioxide (0.05 μm) were mixed evenly to allow the silicon dioxide to adhere to the surface of the nickel cobalt manganese oxide.

[0044] Add 0.3 mol of lithium hydroxide, mix well, and heat treat at 750℃ for 7 h to obtain a composite material of lithium nickel cobalt manganese oxide and lithium silicate.

[0045] Step 2: Preparation of composite cathode materials for lithium-ion batteries

[0046] 0.1 mol of lithium nickel cobalt manganese oxide and lithium silicate composite material were mixed with 0.0005 mol of iron sulfide and 0.0005 mol of iron oxide. The mixture was then heat-treated at 300°C for 3 hours to disperse the catalytic material on the surface of the lithium nickel cobalt manganese oxide and lithium silicate composite material and to form an interface layer between the catalytic material and the lithium silicate composite material, thus obtaining a composite cathode material for lithium-ion batteries.

[0047] A schematic diagram of the prepared material structure is shown below. Figure 1 As shown in the figure, reference numeral 1 represents the positive electrode substrate material, reference numeral 2 represents the interface layer between the positive electrode substrate material and the lithium replenishment material, reference numeral 3 represents the lithium replenishment material coating layer covering the outside of the positive electrode substrate material, and reference numeral 4 represents the surface catalyst material coating the outside of the lithium replenishment material coating layer.

[0048] SEM images of the prepared composite cathode material are shown below. Figure 2 As shown, the composite material has a particle size of 10 μm and is uniformly distributed.

[0049] Example 2

[0050] The steps for preparing composite cathode materials for lithium-ion batteries are as follows:

[0051] Step 1: Preparation of composite materials of positive electrode matrix material and lithium supplementation material

[0052] Mix 0.2 mol cobalt oxide (2 μm) and 0.01 mol iron oxide (0.05 μm) evenly to allow the iron oxide to adhere to the surface of the cobalt oxide;

[0053] Add 0.3 mol of lithium nitrate, mix well, and heat treat at 780℃ for 6 h to obtain a composite material of lithium cobalt oxide and lithium iron ore.

[0054] Step 2: Preparation of composite cathode materials for lithium-ion batteries

[0055] 0.1 mol of the lithium cobalt oxide and lithium iron ferrite composite material was mixed with 0.0006 mol of phosphorus and 0.0004 mol of cobalt phosphide. The mixture was then heat-treated at 120°C for 15 h to disperse the catalytic material on the surface of the lithium cobalt oxide and lithium iron ferrite composite material and to form an interface layer between the two materials, thus obtaining the composite cathode material for lithium-ion batteries.

[0056] The composite cathode material prepared in this embodiment was assembled with silicon-carbon material (BTR, capacity 600mAh / g) into a 2.5Ah pouch battery. Constant current charge-discharge cycle tests were conducted within a voltage range of 2.5–4.6V at a current density of 0.2C. The cycle curves for 200 cycles are shown below. Figure 3 As shown, it exhibits excellent cycle stability.

Claims

1. A composite cathode material for lithium-ion batteries, characterized in that, The composite cathode material includes a cathode matrix material, a lithium supplementation material, and a catalytic material; The positive electrode substrate material includes at least one of the following materials: lithium iron phosphate, lithium iron manganese phosphate, lithium cobalt phosphate, 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 lithium replenishment material includes at least one of the following: lithium silicate-rich material, lithium iron ferrite-rich material, lithium niobate-rich material, lithium zirconate-rich material, and lithium nickelate-rich material. The catalytic material comprises at least one material selected from iron oxide, manganese oxide, cobalt oxide, nickel oxide, iron sulfide, manganese sulfide, cobalt sulfide, nickel sulfide, iron phosphide, manganese phosphide, cobalt phosphide, nickel phosphide, elemental sulfur, elemental phosphorus, graphene, and carbon nanotubes. In the composite cathode material, the molar proportions of the cathode matrix material, the lithium supplementation material, and the catalyst material are 80-98 parts, 0.01-19 parts, and 0.001-1 parts, respectively. The cathode matrix material is located inside the composite cathode material, while the lithium replenishment material and catalytic material are coated on the outside of the cathode matrix material; The preparation method of the composite cathode material includes the following steps: Preparation of S1 cathode matrix material and lithium supplementation material composite material The positive electrode matrix material precursor and the lithium supplement material precursor are mixed evenly so that the lithium supplement material precursor coats the surface of the positive electrode matrix material precursor; a lithium source is added and the mixture is heat-treated at 500~1000℃ to obtain the composite material M1 of the positive electrode matrix material and the lithium supplement material. The precursor for the positive electrode substrate is at least one of the following: iron phosphate, manganese iron phosphate, cobalt phosphate, manganese oxide, nickel manganese oxide, cobalt oxide, nickel cobalt manganese oxide, nickel cobalt aluminum oxide, and lithium-rich oxide; the precursor for the lithium supplement material is at least one of the following: silicon dioxide, iron oxide, niobium oxide, zirconium oxide, and nickel oxide; and the lithium source is at least one of the following: lithium hydroxide, lithium carbonate, lithium acetate, and lithium nitrate. S2 is used in the preparation of composite cathode materials for lithium-ion batteries. The prepared composite material M1 was mixed evenly with the catalyst material and then heat-treated at 100~500℃ to obtain a composite cathode material for lithium-ion batteries.

2. The composite cathode material for lithium-ion batteries according to claim 1, characterized in that, The composite cathode material has a particle size of 1~20 μm, and the coating thickness of the lithium replenishment material and the catalyst material is 1~30 nm.

3. The composite cathode material for lithium-ion batteries according to claim 1, characterized in that, The positive electrode substrate material is lithium nickel cobalt manganese oxide, the lithium replenishment material is lithium silicate rich material, and the catalyst material is a mixture of iron sulfide and iron oxide.

4. The composite cathode material for lithium-ion batteries according to claim 1, characterized in that, The positive electrode substrate material is lithium cobalt oxide, the lithium supplement material is lithium iron phosphate, and the catalyst material is a mixture of phosphorus and cobalt phosphide.

5. A method for preparing a composite cathode material for lithium-ion batteries according to any one of claims 1 to 4, characterized in that, The specific steps are as follows: Preparation of S1 cathode matrix material and lithium supplementation material composite material The positive electrode matrix material precursor and the lithium supplement material precursor are mixed evenly in a certain proportion, so that the lithium supplement material precursor coats the surface of the positive electrode matrix material precursor; a lithium source is added, and after heat treatment at 500~1000℃, a composite material M1 of positive electrode matrix material and lithium supplement material is obtained. The precursor for the positive electrode substrate is at least one of the following: iron phosphate, manganese iron phosphate, cobalt phosphate, manganese oxide, nickel manganese oxide, cobalt oxide, nickel cobalt manganese oxide, nickel cobalt aluminum oxide, and lithium-rich oxide; the precursor for the lithium supplement material is at least one of the following: silicon dioxide, iron oxide, niobium oxide, zirconium oxide, and nickel oxide; and the lithium source is at least one of the following: lithium hydroxide, lithium carbonate, lithium acetate, and lithium nitrate. The molar ratio of the cathode substrate precursor to the lithium supplement precursor is 160:1 to 4:1; the ratio of the sum of the molar amounts of the cathode substrate precursor and the lithium supplement precursor to the molar amount of the lithium source is 1:1.05 to 1:1.

5. S2 is used in the preparation of composite cathode materials for lithium-ion batteries. The prepared composite material M1 was mixed with the catalyst material in a certain proportion and then heat-treated at 100~500℃ to obtain a composite cathode material for lithium-ion batteries. The molar ratio of composite material M1 to catalytic material is 1:0.001 to 1:

1.

6. The method for preparing the composite cathode material for lithium-ion batteries according to claim 5, characterized in that, The particle size of the positive electrode matrix material precursor is 1~20 μm, the particle size of the lithium supplementation material precursor is 0.01~0.2 μm, and the particle size of the catalyst material is 0.01~0.2 μm.

7. The method for preparing the composite cathode material for lithium-ion batteries according to claim 5, characterized in that, The heat treatment time in step S1 is 1~10 h, and the heat treatment time in step 2 is 1~20 h.

8. The use of the composite cathode material according to any one of claims 1 to 4 in the preparation of lithium-ion batteries.

9. The use of the composite cathode material according to claim 8 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.

10. A lithium-ion battery, characterized in that, The positive electrode of the lithium-ion battery is the composite positive electrode material according to any one of claims 1 to 4, and the negative electrode is a carbon-silicon material.

Images