Composite positive electrode active material and preparation method thereof, positive electrode plate and battery

Abstract

The invention discloses a composite positive active material and a preparation method thereof, a positive pole piece and a battery, and belongs to the technical field of lithium ion battery materials. High-voltage lithium nickel manganese oxide, a carbon material additive, a fast ion conductor additive and a process lithium supplement additive are compounded and then are subjected to heat treatment, so that the lithium ion battery has good ion and electron conductivity, and meanwhile, the process lithium supplement additive supplements active lithium continuously consumed by a negative electrode, so that transition metal corrosion and dissolution are inhibited; the electron conductivity and the ion conductivity are obviously improved, so that the rate capability, the first-time and cyclic coulombic efficiency, the capacity and the cyclic retention rate are improved. The preparation process is simple, large-scale preparation is facilitated, and a good application way is provided for application of the high-voltage lithium nickel manganese oxide positive electrode.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion battery materials and relates to a composite positive electrode active material and a preparation method thereof, a positive electrode sheet, and a battery. Background Art

[0002] High-voltage lithium nickel manganese oxide (LMNO) is a novel cathode material for lithium-ion batteries, offering advantages such as high energy density, a high voltage platform, and excellent cycling stability. With the increasing performance requirements for lithium-ion batteries in sectors such as consumer electronics and new energy vehicles, the research and development of high-voltage LMNO has garnered widespread attention. While traditional lithium-ion battery cathode materials, such as lithium cobalt oxide and ternary materials, offer high energy density, they are relatively expensive and have limited resources. In contrast, LMNO, with its advantages of low cost and abundant resources, has become a research hotspot.

[0003] However, high-voltage lithium nickel manganese oxide still faces some challenges in practical applications. First, due to the relatively poor interfacial stability of lithium nickel manganese oxide, interfacial reactions and capacity decay are prone to occur at high voltages, thus affecting the cycle life and safety of the battery. Secondly, the conductivity of lithium nickel manganese oxide is relatively low, which also limits the improvement of its rate performance. Finally, due to the dissolution of transition metals, the negative electrode SEI of lithium nickel manganese oxide is continuously destroyed and consumed, and the battery capacity and stability will also deteriorate. Summary of the Invention

[0004] The present invention provides a composite positive electrode active material, a preparation method thereof, a positive electrode plate, and a battery. The composite material is prepared by combining high-voltage lithium nickel manganese oxide, a carbon material additive, a fast ion conductor additive, and a process lithium replenisher additive, followed by heat treatment. The composite material exhibits excellent ionic and electronic conductivity. The process lithium replenisher additive replenishes the active lithium continuously consumed by the negative electrode, inhibiting transition metal corrosion and dissolution, significantly improving electronic and ionic conductance, and thereby enhancing rate capability, initial and cycle coulombic efficiencies, capacity, and cycle retention.

[0005] The first technical solution adopted by the present invention is a composite positive electrode active material, which includes the following components by mass: 10-990 parts of high-voltage lithium nickel manganese oxide, 3-30 parts of carbon material additives, 2-20 parts of fast ion conductor additives, and 5-50 parts of process lithium supplement additives, and is formed by compounding and heat treatment.

[0006] The characteristics of this technical solution are:

[0007] High voltage lithium nickel manganese oxide is a LiNi with spinel structure 0.5-a Mn 1.5-b M c O 4-d, wherein M is selected from one or more elements of Na, Sr, Cu, Co, Fe, Ce, Al, Zr, Ti, Sb, Rb, Te, Y, W, Mo, Nb, Ta, S, P, B, F and Si, -0.1≤a≤0.1, -0.2≤b≤0.2, 0≤c≤0.1, and -0.3≤d≤0.3.

[0008] The carbon material additive is at least one of super P, porous carbon, hard carbon, carbon nanotubes and carbon nanospheres.

[0009] The fast ion conductor additive is at least one of LATP, LLZO, LLZTO, lithium phosphate, and lithium metaaluminate, and the particle size D50 of the fast ion conductor additive does not exceed 1 μm.

[0010] The lithium supplement additive in the process is a lithium-rich manganese-based material with the chemical formula Li o Ni m Mn n M l O 2-p ; Wherein, 0.85≤o≤1.05, 0.75≤m+n+l≤0.80, 0≤c≤0.05, M is at least one element selected from Na, K, Ta, Zr, Nb, W, Ti, Sr, Fe, Sb, Sn, Ce, Al, Si, Co, Zn, and Mg; the morphology of the process lithium supplement additive is single crystal, and the particle size D50 is 0.5um-4um.

[0011] The second technical solution adopted by the present invention is a method for preparing a composite positive electrode active material, which is specifically implemented according to the following steps:

[0012] Step 1: Add high voltage lithium nickel manganese oxide, carbon material additive, fast ion conductor additive and process lithium supplement additive into a mixing device for mixing;

[0013] Step 2: The obtained mixture is sintered in an air atmosphere and sieved to obtain a composite positive electrode active material.

[0014] The characteristics of this technical solution are:

[0015] The specific mixing process is: first pre-mix high voltage lithium nickel manganese oxide and process lithium supplement additive for 10 minutes to 30 minutes, then add carbon material additive and fast ion conductor additive and mix for 30 minutes to 60 minutes.

[0016] In step 2, the heating and cooling rate of sintering is 1°C / min to 10°C / min, and the mixture is mixed and sintered at 100°C-300°C for 2h-8h.

[0017] The third technical solution adopted by the present invention is a positive electrode plate, comprising a current collector coated with the above-mentioned composite positive electrode active material.

[0018] The fourth technical solution adopted by the present invention is a battery, comprising a separator, an electrolyte, a negative electrode and the above-mentioned positive electrode plate.

[0019] The present invention provides a composite positive electrode active material and a preparation method thereof, which has a simple preparation process and is convenient for large-scale preparation. By introducing a carbon material additive, a fast ion conductor additive, and a process lithium replenishment additive to form a composite lithium nickel manganese oxide positive electrode material, the material has good electronic conductivity and ionic conductivity. The carbon material increases electronic conductivity, the fast ion conductor material increases ionic conductivity, and the process lithium replenishment additive increases capacity. The three can produce a synergistic effect, resulting in a significant improvement in the capacity and rate performance of the positive electrode material compared to their individual applications. At the same time, the stability of the positive electrode active material is also significantly improved, providing a good application path for the application of high-voltage lithium nickel manganese oxide positive electrodes. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a schematic diagram of a method for preparing a composite positive electrode active material of the present invention;

[0021] Figure 2 This is a SEM image of the positive electrode material after Ketjen Black compounding in Example 1 of the present invention;

[0022] Figure 3 This is the SEM of the positive electrode material after carbon nanotube composite in Example 2 of the present invention;

[0023] Figure 4 This is a SEM image of the positive electrode material after the composite of Ketjen black and carbon nanotubes in Example 3 of the present invention. DETAILED DESCRIPTION

[0024] High-voltage lithium nickel manganese oxide (LMNAO) is considered the most promising next-generation cathode material due to its excellent performance and extremely high cost-performance ratio. However, this cathode material exhibits poor electronic conductivity, high battery membrane resistance, and high initial impedance. The DCR (distributed charge / discharge ratio) increases continuously during cycling, leading to cycle degradation. Furthermore, at operating voltages exceeding 4.7V, the electrolyte is susceptible to oxidative decomposition, which corrodes the cathode material and dissolves transition metals. This leads to continuous damage to the negative electrode SEI, continuous consumption of active lithium, and a significant deterioration in battery cycling and storage performance.

[0025] The present invention provides a composite positive electrode material comprising high-voltage lithium nickel manganese oxide, a carbon material additive, a fast ion conductor additive, and a process lithium replenisher additive. The carbon material additive functions as follows: first, a good carbon conductive network can significantly improve the electronic conductivity of high-voltage lithium nickel manganese oxide and reduce the material impedance; second, the carbon material can effectively isolate and adsorb transition metals, inhibiting their damage to the negative electrode SEI; third, the introduction of the carbon material can improve the activity of the process lithium replenisher additive, promote the continuous release of active lithium from the process lithium replenisher, and reduce overpotential. The main function of the fast ion conductor additive is to improve the lithium ion diffusion rate at the interface of the positive electrode material, form a composite ion-electron conductive layer with the carbon material, and reduce the internal resistance of the material. At the same time, the nanoscale additive effectively isolates the positive electrode material from the electrolyte, preventing the decomposition of the electrolyte.

[0026] The role of process lithium replenishment additives: First, the electrochemical window of lithium-rich manganese-based materials matches high-voltage lithium nickel manganese oxide, and the material structure is relatively stable under high voltage; at the same time, the use of lithium-rich manganese-based materials as lithium replenishers is different from conventional lithium replenishers. Conventional lithium replenishers generally replenish lithium once, but lithium-rich manganese-based materials can be used for process lithium replenishment. By utilizing their relatively low coulombic efficiency, they continuously replenish the lost active lithium during the battery cycle, giving the battery a lower initial DCR and a smaller increase in the DCR during the cycle, which is conducive to rapid charging and discharging. At the same time, its initial capacity and capacity retention rate during the cycle are also significantly improved, making it suitable for fast charging and long-cycle application scenarios.

[0027] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] The present invention provides a composite positive electrode active material formed by combining high-voltage lithium nickel manganese oxide, a carbon material additive, a fast ion conductor additive, and a process lithium replenishment additive, followed by heat treatment. This composite material exhibits excellent ionic and electronic conductivity. The process lithium replenishment additive replenishes the active lithium continuously consumed by the negative electrode, inhibiting transition metal corrosion and dissolution. This significantly enhances electronic and ionic conductivity, thereby improving rate capability, initial and cycle coulombic efficiencies, capacity, and cycle retention.

[0029] In order to verify the carbon material additive, fast ion conductor additive and process lithium supplement additive in the present invention, the following comparative examples are provided:

[0030] Comparative Example 1

[0031] Weigh 100g of nickel manganese hydroxide precursor and 21.25g of lithium carbonate, put them into a small mixer and stir for 30 minutes; then, place the mixed powder in a box furnace and calcine at 920°C for 10 hours. By crushing and passing through a 325-mesh sieve, a lithium nickel manganese oxide primary sintered material is obtained.

[0032] 100 g of the prepared lithium nickel manganese oxide primary sintered material and 0.85 g of zirconium phosphate were weighed, placed in a small mixer, and stirred for 30 minutes; then, the mixed powder was placed in a box furnace and calcined at 750°C for 10 hours. The lithium nickel manganese oxide secondary sintered material was obtained by crushing and passing through a 325-mesh sieve.

[0033] Comparative Example 2

[0034] Weigh 100g of nickel manganese hydroxide precursor and 21.25g of lithium carbonate, put them into a small mixer and stir for 30 minutes; then, place the mixed powder in a box furnace and calcine at 920°C for 10 hours. By crushing and passing through a 325-mesh sieve, a lithium nickel manganese oxide primary sintered material is obtained.

[0035] 100 g of the prepared lithium nickel manganese oxide primary sintered material and 0.85 g of zirconium phosphate were weighed, placed in a small mixer, and stirred for 30 min. Then, the mixed powder was placed in a box furnace and calcined at 750°C for 10 h. The lithium nickel manganese oxide secondary sintered material was obtained by crushing and passing through a 325-mesh sieve.

[0036] Weigh 98 g of lithium nickel manganese oxide secondary sintered material and 2 g of single crystal lithium-rich manganese-based positive electrode, put them into a small mixer, stir for 30 minutes, then place the above mixed powder in a box furnace, calcine at 250 ° C for 4 hours, and pass through a 325 mesh sieve to obtain a composite lithium nickel manganese oxide positive electrode material.

[0037] Comparative Example 3

[0038] Weigh 100g of nickel manganese hydroxide precursor and 21.25g of lithium carbonate, put them into a small mixer and stir for 30 minutes; then, place the mixed powder in a box furnace and calcine at 920°C for 10 hours. By crushing and passing through a 325-mesh sieve, a lithium nickel manganese oxide primary sintered material is obtained.

[0039] 100 g of the prepared lithium nickel manganese oxide primary sintered material and 0.85 g of zirconium phosphate were weighed, placed in a small mixer, and stirred for 30 min. Then, the mixed powder was placed in a box furnace and calcined at 750°C for 10 h. The lithium nickel manganese oxide secondary sintered material was obtained by crushing and passing through a 325-mesh sieve.

[0040] Weigh 1g of Ketjen black and 0.5g of nano-LATP, put them into a small mixer and stir for 10 minutes, take 98.5g of lithium nickel manganese oxide secondary sintered material and add it to the mixed material, put it into a small mixer and stir for 30 minutes, place the above mixed powder in a box furnace, calcine at 250°C for 4 hours, and pass through a 325 mesh sieve to obtain a composite lithium nickel manganese oxide positive electrode material.

[0041] The composite lithium nickel manganese oxide cathodes from Comparative Examples 1, 2, and 3 were subjected to physical, chemical, and battery testing. The results are shown in Table 1. Particle size, specific surface area, and pH were measured according to industry standard methods. Cycling tests were conducted at 0.1C gram capacity and 100 cycles at 1C at 45°C. The active material loading was 95%, the areal density was approximately 8 mg / cm², and the electrochemical window was 3.5-4.95V.

[0042] Table 1 Physical and chemical data of the composite nickel manganese oxide positive electrode and battery test data prepared in the comparative example

[0043] Comparative Example D50 / um BET / m2 / g pH 0.1C gram capacity First effect / % 100 times retention rate 1 4.85 0.4429 9.81 133.46 91.26 94.03 2 4.07 0.6884 10.23 134.88 87.19 96.71 3 3.66 1.4672 9.96 132.13 92.29 96.83

[0044] Table 1 shows that the introduction of a process lithium supplement enhances the composite cathode's gram capacity and cycle retention. The introduction of carbon material additives and fast ion conductor additives increases the composite cathode's BET. Due to the smaller particle size of the nanocarbon spheres and nano-LATP, the BET is larger. While the gram capacity decreases slightly, the high-temperature cycling stability is significantly improved.

[0045] Example 1:

[0046] Weigh 100g of nickel manganese hydroxide precursor and 21.25g of lithium carbonate, put them into a small mixer, and stir for 30 minutes. Then place the mixed powder in a box furnace and calcine at 920°C for 10 hours. By crushing and passing through a 325-mesh sieve, a lithium nickel manganese oxide primary sintered material is obtained.

[0047] Weigh 100 g of the prepared lithium nickel manganese oxide primary sintered material and 0.85 g of zirconium phosphate, put them into a small mixer, and stir for 30 minutes. Then, place the mixed powder in a box furnace and calcine at 750°C for 10 hours. The lithium nickel manganese oxide secondary sintered material is obtained by crushing and passing through a 325-mesh sieve.

[0048] Weigh 1g of Ketjen black and 0.5g of nano-Li3PO4, put them into a small mixer and stir for 10min, take 96.5g of lithium nickel manganese oxide secondary sintered material and 1.5g of single crystal lithium-rich manganese-based material and add them to the mixed material, put them into a small mixer and stir for 30min, place the mixed powder in a box furnace, calcine at 250℃ for 4h, and pass through a 325 mesh sieve to obtain a composite lithium nickel manganese oxide positive electrode material. The electron microscope shows Figure 2 .

[0049] Example 2:

[0050] Weigh 100g of nickel manganese hydroxide precursor and 21.25g of lithium carbonate, put them into a small mixer, and stir for 30 minutes. Then place the mixed powder in a box furnace and calcine at 920°C for 10 hours. By crushing and passing through a 325-mesh sieve, a lithium nickel manganese oxide primary sintered material is obtained.

[0051] Weigh 100 g of the prepared lithium nickel manganese oxide primary sintered material and 0.85 g of zirconium phosphate, put them into a small mixer, and stir for 30 minutes. Then, place the mixed powder in a box furnace and calcine at 750°C for 10 hours. The lithium nickel manganese oxide secondary sintered material is obtained by crushing and passing through a 325-mesh sieve.

[0052] Weigh 1g of carbon nanotubes and 1g of nano-Li3PO4, put them into a small mixer and stir for 10min, take 96.5g of lithium nickel manganese oxide secondary sintered material and 1.5g of single crystal lithium-rich manganese-based material and add them to the mixture, put it into a small mixer and stir for 30min, place the above mixed powder in a box furnace, calcine at 250℃ for 4h, pass through a 325 mesh sieve, and obtain a composite lithium nickel manganese oxide positive electrode material. The electron microscope shows Figure 3 .

[0053] Example 3:

[0054] Weigh 100g of nickel manganese hydroxide precursor and 21.25g of lithium carbonate, put them into a small mixer, and stir for 30 minutes. Then place the mixed powder in a box furnace and calcine at 920°C for 10 hours. By crushing and passing through a 325-mesh sieve, a lithium nickel manganese oxide primary sintered material is obtained.

[0055] Weigh 100 g of the prepared lithium nickel manganese oxide primary sinter and 0.85 g of zirconium phosphate, put them into a small mixer, and stir for 30 minutes. Then, place the mixed powder in a box furnace and calcine at 750°C for 10 hours. The lithium nickel manganese oxide secondary sintered material is obtained by crushing and passing through a 325-mesh sieve.

[0056] Weigh 0.5g of Ketjen black, 0.5g of carbon nanotubes and 1g of nano-Li3PO4, put them into a small mixer and stir for 10min, take 96.5g of lithium nickel manganese oxide secondary sintered material and 1.5g of single crystal lithium-rich manganese-based material and add them to the mixture, put it into a small mixer and stir for 30min, place the above mixed powder in a box furnace, calcine at 250℃ for 4h, and pass through a 325 mesh sieve to obtain a composite lithium nickel manganese oxide positive electrode material. The electron microscope shows that Figure 3 .

[0057] In this embodiment, the mass proportions of the components are as follows: 10-990 parts of high voltage lithium nickel manganese oxide, 3-30 parts of carbon material additive, 2-20 parts of fast ion conductor additive, and 5-50 parts of process lithium supplement additive.

[0058] Example 4

[0059] Weigh 100g of nickel manganese hydroxide precursor and 21.25g of lithium carbonate, put them into a small mixer, and stir for 30 minutes. Then place the mixed powder in a box furnace and calcine at 920°C for 10 hours. By crushing and passing through a 325-mesh sieve, a lithium nickel manganese oxide primary sintered material is obtained.

[0060] Weigh 100 g of the prepared lithium nickel manganese oxide primary sinter and 0.85 g of aluminum fluoride, put them into a small mixer, and stir for 30 minutes. Then, place the mixed powder in a box furnace and calcine at 750°C for 10 hours. The lithium nickel manganese oxide secondary sintered material is obtained by crushing and passing through a 325-mesh sieve.

[0061] Weigh 0.5g super P, 0.5g carbon nanotubes and 1g nano Li3PO4, put them into a small mixer and stir for 10 minutes, take 96.5g lithium nickel manganese oxide secondary sintered material and 1.5g single crystal lithium-rich manganese-based material and add them to the mixture, put it into a small mixer and stir for 30 minutes, place the above mixed powder in a box furnace, calcine at 250°C for 4h, and pass through a 325 mesh sieve to obtain a composite lithium nickel manganese oxide positive electrode material.

[0062] Example 5

[0063] Weigh 100g of nickel manganese hydroxide precursor and 21.25g of lithium carbonate, put them into a small mixer, and stir for 30 minutes. Then place the mixed powder in a box furnace and calcine at 920°C for 10 hours. By crushing and passing through a 325-mesh sieve, a lithium nickel manganese oxide primary sintered material is obtained.

[0064] Weigh 100 g of the prepared lithium nickel manganese oxide primary sinter and 0.85 g of aluminum fluoride, put them into a small mixer, and stir for 30 minutes. Then, place the mixed powder in a box furnace and calcine at 750°C for 10 hours. The lithium nickel manganese oxide secondary sintered material is obtained by crushing and passing through a 325-mesh sieve.

[0065] Weigh 0.5g of porous carbon, 0.5g of carbon nanotubes and 1g of nano-Li3PO4, put them into a small mixer and stir for 10 minutes, take 96.5g of lithium nickel manganese oxide secondary sintered material and 1.5g of single crystal lithium-rich manganese-based material and add them to the mixed material, put them into a small mixer and stir for 30 minutes, place the above mixed powder in a box furnace, calcine at 250°C for 4h, and pass through a 325 mesh sieve to obtain a composite lithium nickel manganese oxide positive electrode material.

[0066] Example 6

[0067] Weigh 100g of nickel manganese hydroxide precursor and 21.25g of lithium carbonate, put them into a small mixer, and stir for 30 minutes. Then place the mixed powder in a box furnace and calcine at 920°C for 10 hours. By crushing and passing through a 325-mesh sieve, a lithium nickel manganese oxide primary sintered material is obtained.

[0068] Weigh 100 g of the prepared lithium nickel manganese oxide primary sinter and 0.85 g of aluminum fluoride, put them into a small mixer, and stir for 30 minutes. Then, place the mixed powder in a box furnace and calcine at 750°C for 10 hours. The lithium nickel manganese oxide secondary sintered material is obtained by crushing and passing through a 325-mesh sieve.

[0069] Weigh 0.5g of hard carbon, 0.5g of carbon nanotubes and 1g of nano-Li3PO4, put them into a small mixer and stir for 10 minutes, take 96.5g of lithium nickel manganese oxide secondary sintered material and 1.5g of single crystal lithium-rich manganese-based material and add them to the mixed material, put them into a small mixer and stir for 30 minutes, place the above mixed powder in a box furnace, calcine at 250°C for 4 hours, and pass through a 325-mesh sieve to obtain a composite lithium nickel manganese oxide positive electrode material.

[0070] Example 7

[0071] Weigh 100g of nickel manganese hydroxide precursor and 21.25g of lithium carbonate, put them into a small mixer, and stir for 30 minutes. Then place the mixed powder in a box furnace and calcine at 920°C for 10 hours. By crushing and passing through a 325-mesh sieve, a lithium nickel manganese oxide primary sintered material is obtained.

[0072] Weigh 100 g of the prepared lithium nickel manganese oxide primary sinter and 0.85 g of aluminum fluoride, put them into a small mixer, and stir for 30 minutes. Then, place the mixed powder in a box furnace and calcine at 750°C for 10 hours. The lithium nickel manganese oxide secondary sintered material is obtained by crushing and passing through a 325-mesh sieve.

[0073] Weigh 0.5g of Ketjen black, 0.5g of carbon nanotubes and 1g of nano-LATP, put them into a small mixer and stir for 10 minutes, take 96.5g of lithium nickel manganese oxide secondary sintered material and 1.5g of single crystal lithium-rich manganese-based material and add them to the mixture, put it into a small mixer and stir for 30 minutes, place the above mixed powder in a box furnace, calcine at 250°C for 4 hours, and pass through a 325 mesh sieve to obtain a composite lithium nickel manganese oxide positive electrode material.

[0074] Example 8

[0075] Weigh 100g of nickel manganese hydroxide precursor and 21.25g of lithium carbonate, put them into a small mixer, and stir for 30 minutes. Then place the mixed powder in a box furnace and calcine at 920°C for 10 hours. By crushing and passing through a 325-mesh sieve, a lithium nickel manganese oxide primary sintered material is obtained.

[0076] Weigh 100 g of the prepared lithium nickel manganese oxide primary sinter and 0.85 g of aluminum fluoride, put them into a small mixer, and stir for 30 minutes. Then, place the mixed powder in a box furnace and calcine at 750°C for 10 hours. The lithium nickel manganese oxide secondary sintered material is obtained by crushing and passing through a 325-mesh sieve.

[0077] Weigh 0.5g of Ketjen black, 0.5g of carbon nanotubes and 1g of nano-LLZO, put them into a small mixer and stir for 10 minutes, take 96.5g of lithium nickel manganese oxide secondary sintered material and 1.5g of single crystal lithium-rich manganese-based material and add them to the mixture, put it into a small mixer and stir for 30 minutes, place the above mixed powder in a box furnace, calcine at 250°C for 4h, and pass through a 325 mesh sieve to obtain a composite lithium nickel manganese oxide positive electrode material.

[0078] Example 9

[0079] Weigh 100g of nickel manganese hydroxide precursor and 21.25g of lithium carbonate, put them into a small mixer, and stir for 30 minutes. Then place the mixed powder in a box furnace and calcine at 920°C for 10 hours. By crushing and passing through a 325-mesh sieve, a lithium nickel manganese oxide primary sintered material is obtained.

[0080] Weigh 100 g of the prepared lithium nickel manganese oxide primary sinter and 0.85 g of aluminum fluoride, put them into a small mixer, and stir for 30 minutes. Then, place the mixed powder in a box furnace and calcine at 750°C for 10 hours. The lithium nickel manganese oxide secondary sintered material is obtained by crushing and passing through a 325-mesh sieve.

[0081] Weigh 0.5g of Ketjen black, 0.5g of carbon nanotubes and 1g of nano-LLZTO, put them into a small mixer and stir for 10 minutes, take 96.5g of lithium nickel manganese oxide secondary sintered material and 1.5g of single crystal lithium-rich manganese-based material and add them to the mixture, put it into a small mixer and stir for 30 minutes, place the above mixed powder in a box furnace, calcine at 250°C for 4 hours, and pass through a 325 mesh sieve to obtain a composite lithium nickel manganese oxide positive electrode material.

[0082] Example 10

[0083] Weigh 100g of nickel manganese hydroxide precursor and 21.25g of lithium carbonate, put them into a small mixer, and stir for 30 minutes. Then place the mixed powder in a box furnace and calcine at 920°C for 10 hours. By crushing and passing through a 325-mesh sieve, a lithium nickel manganese oxide primary sintered material is obtained.

[0084] Weigh 100 g of the prepared lithium nickel manganese oxide primary sinter and 0.85 g of aluminum fluoride, put them into a small mixer, and stir for 30 minutes. Then, place the mixed powder in a box furnace and calcine at 750°C for 10 hours. The lithium nickel manganese oxide secondary sintered material is obtained by crushing and passing through a 325-mesh sieve.

[0085] Weigh 0.5g of Ketjen black, 0.5g of carbon nanotubes and 1g of nano-LiAlO2, put them into a small mixer and stir for 10 minutes, take 96.5g of lithium nickel manganese oxide secondary sintered material and 1.5g of single crystal lithium-rich manganese-based material and add them to the mixed material, put them into a small mixer and stir for 30 minutes, place the above mixed powder in a box furnace, calcine at 250°C for 4h, and pass through a 325 mesh sieve to obtain a composite lithium nickel manganese oxide positive electrode material.

[0086] like Figure 2-4 As shown, the SEM corresponds to the positive electrode materials of Ketjen black, carbon nanotubes, and Ketjen black and carbon nanotubes mixed with nano-Li3PO4. Figure 2-3 It can be seen that nano-carbon balls, carbon nanotubes and nano-Li3PO4 are evenly attached to the surface of the positive electrode material, which provides good ionic and electronic conductivity for the positive electrode material, making the battery have a lower initial DCR and cycle retention rate. Figure 4 It can be seen that the carbon nanotubes and carbon balls form a conductive network combined with points and lines, and form a fast ion-electron conductive layer with nano-Li3PO4, which further reduces the sheet resistance of the positive electrode material, making the battery have a lower initial DCR and better cycle life.

[0087] The primary sintered material from the above example was subjected to physical, chemical, and battery testing, as shown in Table 2. Particle size, specific surface area, and pH were measured according to industry standard methods. The battery was subjected to 0.1C gram capacity and 100 cycles of 1C at 45°C. The active material loading was 95%, the areal density was controlled between 8-10 mg / cm², and the electrochemical window was 3.5-4.95V.

[0088] Table 2 Physical and chemical data of composite nickel manganese oxide positive electrode and battery test data prepared in Example

[0089]

[0090]

[0091] As can be seen from Table 2, the overall capacity of samples with different carbon composites (super P, porous carbon, hard carbon, Ketjen black and carbon nanotubes) has slightly decreased, but the capacity of the lithium nickel manganese oxide positive electrode composited with nanospheres and nanotubes remains basically unchanged, and its first efficiency is around 88%. The high-temperature cycle capacity retention rate is significantly improved, especially the lithium nickel manganese oxide positive electrode composited with nanospheres and nanotubes, with a capacity retention rate of more than 97% after 100 cycles. This is because Ketjen black and carbon nanotubes form a composite conductive network of point-line combination, which can effectively reduce the internal resistance of the material, while inhibiting and adsorbing transition metals and improving its high-temperature cycle stability. The capacity of samples with different fast ion conductor additives remains basically unchanged, all around 133mAh / g, with a high capacity retention rate, among which LATP, LLZTO and Li3PO4 are better.

[0092] At the same time, the present invention also relates to a lithium ion secondary battery positive electrode, which includes a current collector, on which the above-mentioned composite nickel manganese oxide positive electrode active material is loaded. In addition, the present application also relates to a lithium ion secondary battery, which includes a diaphragm, an electrolyte, a negative electrode and the above-mentioned lithium ion secondary battery positive electrode. The fast ion-electron conductive layer can effectively improve the electronic and ionic conductivity of the material and reduce the membrane resistance of the battery. At the same time, the carbon material therein can effectively reduce the dissolution of transition metals and improve the high-temperature cycle performance of the battery. After adding the lithium supplement additive, the loss of active lithium in the battery formation and cycle process is effectively compensated, further improving the capacity and high-temperature cycle performance of the battery.

[0093] According to the disclosure and teachings of the above description, those skilled in the art to which the present invention belongs may also change and modify the above-mentioned embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the scope of protection of the claims of the present invention. In addition, although some specific terms are used in this specification, these terms are only for convenience of description and do not constitute any limitation to the present invention. As described in the above-mentioned embodiments of the present invention, other materials, preparation methods, and applications obtained by the same or similar methods and components are all within the scope of protection of the present invention.

Claims

1. A composite positive electrode active material, characterized in that The invention comprises the following components in parts by mass: 10-990 parts of high-voltage lithium nickel manganese oxide, 3-30 parts of carbon material additive, 2-20 parts of fast ion conductor additive and 5-50 parts of process lithium supplement additive, and is prepared by compounding and heat treatment.

2. A composite positive electrode active material according to claim 1, characterized in that: The high voltage lithium nickel manganese oxide is a LiNi having a spinel structure. 0.5-a Mn 1.5-b M c O 4-d , wherein M is selected from one or more elements of Na, Sr, Cu, Co, Fe, Ce, Al, Zr, Ti, Sb, Rb, Te, Y, W, Mo, Nb, Ta, S, P, B, F and Si, -0.1≤a≤0.1, -0.2≤b≤0.2, 0≤c≤0.1, and -0.3≤d≤0.

3.

3. The composite positive electrode active material according to claim 1, characterized in that: The carbon material additive is at least one of super P, porous carbon, hard carbon, carbon nanotubes and carbon nanospheres.

4. The composite positive electrode active material according to claim 1, characterized in that: The fast ion conductor additive is at least one of LATP, LLZO, LLZTO, lithium phosphate, and lithium metaaluminate, and the particle size D50 of the fast ion conductor additive does not exceed 1 μm.

5. The composite positive electrode active material according to claim 1, characterized in that: The lithium supplement additive in the process is a lithium-rich manganese-based material with a chemical formula of Li o Ni m Mn n M l O 2-p ; Wherein, 0.85≤o≤1.05, 0.75≤m+n+l≤0.80, 0≤p≤0.03, M is at least one element selected from Na, K, Ta, Zr, Nb, W, Ti, Sr, Fe, Sb, Sn, Ce, Al, Si, Co, Zn, and Mg; the morphology of the process lithium supplement additive is single crystal, and the particle size D50 is 0.5um-4um.

6. A method for preparing a composite positive electrode active material, characterized in that: The method for preparing the composite positive electrode active material according to any one of claims 1 to 5 is specifically implemented according to the following steps: Step 1: Add high voltage lithium nickel manganese oxide, carbon material additive, fast ion conductor additive and process lithium supplement additive into a mixing device for mixing; Step 2: The obtained mixture is sintered in an air atmosphere and sieved to obtain a composite positive electrode active material.

7. The method for preparing a composite positive electrode active material according to claim 6, characterized in that: The specific mixing process is: first pre-mix high voltage lithium nickel manganese oxide and process lithium supplement additive for 10 minutes to 30 minutes, then add carbon material additive and fast ion conductor additive and mix for 30 minutes to 60 minutes.

8. The method for preparing a composite positive electrode active material according to claim 6, characterized in that: In the step 2, the heating and cooling rate of sintering is 1° C. / min to 10° C. / min, and the mixing and sintering are carried out at 100° C.-300° C. for 2 h to 8 h.

9. A positive electrode plate, characterized in that: The present invention comprises a current collector coated with a composite positive electrode active material according to any one of claims 1 to 5.

10. A battery, characterized in that: The invention comprises a separator, an electrolyte, a negative electrode and a positive electrode sheet as claimed in claim 9.

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