A phosphorus-doped-coated high-nickel single-crystal lithium-ion battery cathode material and its preparation method

Abstract

This invention belongs to the field of lithium-ion batteries and discloses a phosphorus-doped-coated high-nickel single-crystal lithium-ion battery cathode material, comprising a high-nickel single-crystal cathode material matrix LiNi. x Co y Mn z P a O2, wherein the substrate surface is coated with a Li3PO4-Al2O3 composite coating layer or a Li3PO4-ZrO2 composite coating layer. Its preparation method: a nickel-cobalt-manganese salt mixed solution is prepared by mixing nickel salt, cobalt salt, and manganese salt; a phosphorus source, a precipitant, and a metal salt (M) are added to the mixed solution for a co-precipitation reaction to obtain a precursor; wherein the metal salt (M) includes one or more of aluminum nitrate and zirconium oxynitrate; the precursor is mixed with a lithium source and then sintered to obtain the phosphorus-doped-coated high-nickel single-crystal lithium-ion battery cathode material. The phosphorus-doped-coated high-nickel single-crystal lithium-ion battery cathode material of the present invention not only optimizes lithium-ion diffusion kinetics through bulk-interface synergy but also improves cycle stability by inhibiting particle cracking and transition metal dissolution.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of lithium ion battery materials, and particularly relates to a phosphorus-doped-coated high-nickel single-crystal lithium ion battery positive electrode material and a preparation method thereof. BACKGROUND

[0002] Traditional modification methods of lithium ion battery materials mostly adopt a step-by-step process, such as stabilizing the bulk phase structure by element doping (such as Al, Mg) first, and then inhibiting the interface side reaction by surface coating (such as oxide, phosphate), but the step-by-step processing is easy to cause problems such as complex process, poor combination of the coating layer and the substrate, and uneven doping. In addition, phosphorus elements can theoretically optimize the stability of the bulk phase structure and the interface electrochemical activity of the material due to their strong electronegativity and stable P-O bond characteristics, but the synergistic effect of phosphorus doping and coating in the prior art has not been fully explored.

[0003] Patent document CN111916725 A discloses a phosphorus-doped lithium battery high-nickel positive electrode material and a preparation process thereof, which is to perform electrostatic spinning on a spinning solution containing a lithium source, a nickel source, a manganese source and an organic carbon source, or a spinning solution containing a lithium source, a nickel source, a cobalt source, a manganese source and an organic carbon source; then perform pre-oxidation treatment, contact with a phosphorus source, and stage calcination. Although the high-nickel positive electrode material developed by this method has high specific capacity, excellent cycle stability and simple preparation process, the method has high cost and low single yield, and is difficult to meet the mass production demand of the battery industry for positive electrode materials, and the electrostatic spinning needs to accurately control the voltage, flow rate, temperature and humidity and other parameters, which is easy to affect the consistency of the material in the experimental process.

[0004] Patent document CN117174865 A discloses a phosphorus-doped carbon-coated sodium ion positive electrode material and a preparation method thereof, which is to place sodium electric layered oxide positive electrode material powder on a substrate in the cavity of a PECVD device, adjust the substrate height; perform vacuum pumping and heating; pass carbon source gas and mixed gas of carrier gas and phosphine into the PECVD device cavity, heat, ignite the microwave plasma, adjust the microwave power, react for a certain time; stop aeration and heating, wait for the substrate temperature to reduce to 100℃, pass nitrogen into the cavity to reach normal pressure, take out the powder material, and obtain the phosphorus-doped carbon-coated sodium ion positive electrode material. Although the material obtained by this method can increase the interlayer spacing of carbon and is beneficial to the transmission of sodium ions, this method is limited by the uniformity of powder processing, equipment adaptability and safety, and has low potential for industrial amplification.

[0005] Therefore, it is urgent to develop an efficient and low-cost integrated preparation process to realize the precise doping of phosphorus elements in the crystal lattice and the synchronous construction of the surface functional coating layer in a single-step reaction, so as to break through the performance bottleneck of single-crystal high-nickel positive electrode materials and promote their large-scale application in high-specific-energy power batteries. SUMMARY

[0006] The technical problem solved by the present application is to overcome the deficiencies and shortcomings mentioned in the above background art, and to provide a phosphorus-doped-coated high-nickel single-crystal lithium-ion battery cathode material and a preparation method thereof.

[0007] To solve the above technical problems, the technical solution provided by the present application is:

[0008] A phosphorus-doped-coated high-nickel single-crystal lithium-ion battery cathode material, comprising a high-nickel single-crystal cathode material matrix LiNi x Co y Mn z P a O2, the surface of the matrix is coated with a Li3PO4-Al2O3 composite coating layer or a Li3PO4-ZrO2 composite coating layer, wherein 90≤x≤0.95, 0≤y≤0.10, 0≤z≤0.10, 0.001≤a≤0.05.

[0009] The phosphorus-doped-coated high-nickel single-crystal lithium-ion battery cathode material described above, preferably, the thickness of the coating layer is 10-50 nm, the phosphorus element exists in the form of coating and doping, the surface concentration is 1.5-3 at%, and the matrix concentration is 0.8-1.2 at%.

[0010] The phosphorus-doped-coated high-nickel single-crystal lithium-ion battery cathode material described above, preferably, the grain size of the phosphorus-doped-coated high-nickel single-crystal lithium-ion battery cathode material is 2-5 μm, the Li / Ni misarrangement degree is ≤2.5%, and the specific surface area is 0.5-2.0 m 2 / g.

[0011] The phosphorus-doped-coated high-nickel single-crystal lithium-ion battery cathode material described above, preferably, the mass ratio of Li3PO4 to Al2O3 in the composite coating layer is 1:4-10:1; or, the mass ratio of Li3PO4 to ZrO2 is 1:4-10:1.

[0012] Based on one overall inventive concept, the present application also provides a preparation method of a phosphorus-doped-coated high-nickel single-crystal lithium-ion battery cathode material, comprising the following steps:

[0013] (1) Prepare a nickel-cobalt-manganese salt mixed solution by mixing nickel salt, cobalt salt and manganese salt; add a phosphorus source, a precipitating agent and an M metal salt to the mixed solution to perform a co-precipitation reaction, to obtain a nickel-cobalt-manganese hydroxide precursor; wherein the M metal salt includes one or more of aluminum nitrate and zirconium oxy nitrate; in this process, the phosphorus exists in the form of an anion (PO4 3-The presence of ions allows them to co-precipitate with transition metal hydroxides and enter the crystal lattice. Meanwhile, the cations of metal salts form hydroxide precipitates. During subsequent high-temperature processing, the hydroxides are converted into oxides and cannot enter the crystal lattice of transition metal oxides. Instead, they remain on the surface to form a coating layer covering the particle surface.

[0014] (2) The nickel cobalt manganese hydroxide precursor is mixed with a lithium source and then sintered to obtain the phosphorus-doped-coated high-nickel single crystal lithium-ion battery cathode material. The sintering is carried out in an oxygen atmosphere, including first heating to 400-600°C at a heating rate of 5-10°C / min and holding for 2-5 h; then heating to 750-950°C at a heating rate of 2-10°C / min and holding for 8-15 h.

[0015] In the above preparation method, preferably, in step (1), the amount of M metal salt added is 0.1% to 3.0% of the total mass of nickel salt, cobalt salt and manganese salt.

[0016] In the above preparation method, preferably, in step (1), the phosphorus source is one or more of ammonium phosphate, diammonium hydrogen phosphate or diammonium dihydrogen phosphate, and its addition amount is 0.5% to 5.0% of the total mass of nickel salt, cobalt salt and manganese salt.

[0017] In the above preparation method, preferably, in step (1), the pH value of the reaction system is controlled to be 10-12 during the coprecipitation reaction, and the reaction is stirred at 40-80℃ for 4-12 h.

[0018] In the above preparation method, preferably, in step (1), the amount of nickel salt, cobalt salt and manganese salt added is calculated according to the molar ratio of Ni:Co:Mn as 90-95:0-10:0-10;

[0019] In step (2), the amount of lithium source and cobalt manganese hydroxide precursor added is calculated based on a Li:(Ni+Co+Mn) molar ratio of 1.05-1.15:1.

[0020] In the above preparation method, preferably, in step (1), the precipitant is one or more of sodium hydroxide, sodium carbonate or ammonia water; a complexing agent is also added during the co-precipitation reaction, the complexing agent is ammonia water or polyethylene glycol, and the molar ratio of the complexing agent to the total molar of nickel salt, cobalt salt and manganese salt is 1:1-3:1.

[0021] In the above preparation method, preferably, in step (2), the oxygen atmosphere flow rate is 50-200 sccm during the sintering process.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] (1) The phosphorus-doped-coated high-nickel single-crystal lithium-ion battery cathode material of the present invention forms stable "anchoring points" by occupying interstitial spaces or replacing some transition metal sites in the bulk phase of the matrix, thereby suppressing Li / Ni mixing (≤2.5%) and reducing lattice oxygen release. At the same time, the surface coating layer forms a continuous interface with the phosphorus-doped region through chemical bonding, constructing a "fast lithium-ion channel", reducing interfacial impedance and blocking electrolyte corrosion. This bulk-interface synergy not only optimizes lithium-ion diffusion kinetics, but also improves cycle stability by suppressing particle cracking and transition metal dissolution. In summary, the phosphorus-doped-coated single-crystal high-nickel cathode material of the present invention has low cation mixing, few interfacial side reactions, and high structural stability. The batteries assembled from the electrode sheets made of this material exhibit excellent high-rate performance and cycle performance.

[0024] (2) The present invention coats the surface of the substrate material with a Li3PO4-Al2O3 composite coating layer or a Li3PO4-ZrO2 composite coating layer, which not only ensures the lithium ion transport efficiency but also enhances the surface stability, achieving synergistic optimization of ion conduction and physical barrier. In addition, the Al2O3 / ZrO2 coating layer removes acidic substances (such as HF) in the electrolyte, while Li3PO4 inhibits oxygen loss. The synergistic effect of the two can significantly improve the cycle stability.

[0025] (3) This invention addresses the problem of poor cycle performance of high-nickel single-crystal cathode materials due to Li / Ni mixing, lattice oxygen release, and interfacial side reactions. It proposes a one-step process for phosphorus doping and coating. First, phosphorus is embedded into the precursor lattice through a co-precipitation reaction to stabilize the bulk structure and suppress cation mixing. Then, a dense surface protective layer is formed during sintering to reduce electrolyte corrosion. At the same time, staged temperature-controlled sintering (low-temperature solid-phase reaction combined with high-temperature single-crystal densification) is used to achieve bulk-interface synergistic optimization. While simplifying the process, it significantly improves the cycle stability of the material, providing an efficient and industrializable solution for high-energy-density lithium-ion batteries.

[0026] (4) In the co-precipitation process, the solution is mixed and the pH value is precisely controlled to 10~12 to ensure that phosphorus and metal hydroxide are precipitated simultaneously. At the same time, with the help of complexing agents, the phase separation during precipitation can be reduced, the segregation phenomenon can be suppressed, and the doping uniformity can be further improved, thereby achieving atomic-level uniform doping. Then, the phosphorus element is uniformly embedded into the precursor lattice through co-precipitation, suppressing Li / Ni mixing (≤2.5%), reducing lattice oxygen release, and improving structural stability. During the sintering process, a nanoscale coating layer (such as a composite phase of Li3PO4-Al2O3 or Li3PO4-ZrO2) is formed simultaneously to block electrolyte corrosion, reduce transition metal dissolution, delay the growth of interfacial impedance, and achieve synergistic optimization of the matrix phase and interface of the material.

[0027] (5) The preparation method of the present invention realizes the doping and coating of the cathode material in one step. The doping and coating are carried out simultaneously, avoiding lattice defects caused by multiple heat treatments, improving the stability of the material structure, and the process is simple, green and environmentally friendly, energy-saving and cost-effective, and suitable for industrial production. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a TEM image of the phosphorus-doped-coated single-crystal high-nickel cathode material prepared in Example 1 of this invention;

[0030] Figure 2 This is a comparison chart of the cycle performance of batteries assembled from phosphorus-doped-coated single-crystal high-nickel cathode materials prepared in Example 1 and Comparative Example 1 of this invention. Detailed Implementation

[0031] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0032] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0033] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0034] Material testing in the following embodiments: The obtained material was subjected to surface scanning of the particle cross-section using transmission electron microscopy-energy dispersive spectroscopy (TEM-EDS), and the concentration gradient of phosphorus from the surface to the interior of multiple particles was statistically analyzed. The Li / Ni mixing degree was calculated using X-ray diffraction (XRD) combined with Rietveld refinement. The specific surface area of ​​the material particles was measured using a specific surface area analyzer (BET).

[0035] Example 1:

[0036] A phosphorus-doped-coated high-nickel single-crystal lithium-ion battery cathode material of the present invention comprises a high-nickel single-crystal cathode material matrix LiNi. 0.9 Co 0.05 Mn0.05 P 0.02 O2, the substrate surface is coated with a Li3PO4-Al2O3 composite coating layer; the coating layer thickness is 30nm, phosphorus exists in the form of coating and doping, the surface concentration is 2.0 at%, the substrate concentration is 1.0 at%; the phosphorus-doped-coated high-nickel single crystal lithium-ion battery cathode material has a particle size of 2-5 μm, Li / Ni mixing degree ≤1.8%, and specific surface area of ​​0.8m². 2 / g.

[0037] The preparation method of the phosphorus-doped-coated high-nickel single-crystal lithium-ion battery cathode material in this embodiment includes the following steps:

[0038] (1) Prepare a 1M solution by mixing nickel sulfate, cobalt sulfate and manganese sulfate in a molar ratio of Ni:Co:Mn=90:5:5, add 2wt% ammonium dihydrogen phosphate as phosphorus source and 1.5wt% aluminum nitrate, adjust the pH to 11 by adding ammonia water, and then react at 60℃ for 8 h. After centrifugation and drying, obtain nickel cobalt manganese hydroxide precursor;

[0039] (2) The nickel-cobalt-manganese hydroxide precursor and LiOH·H2O were mixed and ball-milled at a ratio of Li:(Ni+Co+Mn)=1.05:1 for 4 h. Then, the mixture was placed in a calcining furnace and heated to 500℃ at an oxygen flow rate of 100 sccm. The temperature was first increased to 500℃ at 10℃ / min and held for 3 h, and then increased to 850℃ at 5℃ / min and held for 12 h. After cooling, the mixture was ground to obtain LiNi. 0.9 Co 0.05 Mn 0.05 P 0.02 The mass ratio of Li3PO4 to Al2O3 in the O2@ Li3PO4-Al2O3 composite coating layer is approximately 10:1.

[0040] like Figure 1 As shown, the phosphorus-doped-coated high-nickel cathode material obtained in this embodiment is micron-sized bulk particles.

[0041] The positive electrode sheet made of the phosphorus-doped-coated high-nickel positive electrode material prepared in this embodiment is used to assemble a coin-type lithium-ion battery. The specific process includes:

[0042] Positive electrode preparation method: In a dew point room, 0.8 g of the phosphorus-doped-coated high-nickel positive electrode material prepared in this example was ground with 0.1 g of conductive carbon black and 0.1 g of polyvinylidene fluoride until no obvious particles were visible. Then, 2 mL of N-methylpyrrolidone solution was added to the above mixture, and grinding was continued until a homogeneous slurry was formed. The slurry was then coated onto the current collector aluminum foil to ensure uniform adhesion of the slurry to the current collector surface. Finally, the mixture was dried at 120 °C for 6 h and punched to form an SC-NCM positive electrode with a diameter of 12 mm.

[0043] Assemble a button lithium-ion battery: Place the obtained SC-NCM positive electrode sheet into the positive electrode shell and add an appropriate amount of electrolyte to wet the electrode; then cover with a separator, place the lithium sheet and stack the gasket and spring sheet; finally align the negative electrode shell and press and seal it with a sealing machine; after assembly, it needs to stand for 24 hours to allow the electrolyte to fully wet it before charging and discharging tests are performed.

[0044] Battery testing: The coin cell lithium-ion battery assembled in this embodiment was tested for its initial charge-discharge specific capacity at 0.1 C under the conditions of a discharge cutoff voltage of 2.75 V and a charge cutoff voltage of 4.3 V. After 3 cycles of activation at 0.1 C, its cycle performance was tested by charging at 0.5 C and discharging at 0.5 C for 200 cycles. The test results are shown in Table 1. Figure 2 As shown.

[0045] As shown in Table 1, the coin-type lithium-ion battery assembled in this embodiment has a first charge-discharge specific capacity of 234.91 mAh / g and 208.34 mAh / g at 0.1C, respectively, and a coulombic efficiency of 88.69%.

[0046] Depend on Figure 2 It can be seen that the coin cell lithium-ion battery assembled in this embodiment retains 87.43% of its discharge capacity after 200 cycles at a 0.5 C rate.

[0047] Example 2:

[0048] A phosphorus-doped-coated high-nickel single-crystal lithium-ion battery cathode material of the present invention comprises a high-nickel single-crystal cathode material matrix LiNi. 0.92 Co 0.06 Mn 0.02 P 0.005 O2, the substrate surface is coated with a Li3PO4-ZrO2 composite coating layer; the coating layer thickness is 25 nm, phosphorus exists in the form of coating and doping, the surface concentration is 1.5 at%, the substrate concentration is 0.8 at%; the phosphorus-doped-coated high-nickel single crystal lithium-ion battery cathode material has a particle size of 2-5 μm, Li / Ni mixing degree ≤2.0%, and specific surface area of ​​1.0 m². 2 / g.

[0049] The preparation method of the phosphorus-doped-coated high-nickel single-crystal lithium-ion battery cathode material in this embodiment includes the following steps:

[0050] (1) Prepare a 1M solution by mixing nickel sulfate, cobalt sulfate and manganese sulfate in a molar ratio of Ni:Co:Mn=92:6:2, add 0.5wt% ammonium dihydrogen phosphate as phosphorus source and 1.0wt% zirconium oxynitrate, add sodium carbonate and ammonia water to adjust pH=10, react at 50℃ for 10h, centrifuge and dry to obtain nickel cobalt manganese hydroxide precursor;

[0051] (2) The nickel-cobalt-manganese hydroxide precursor was mixed with LiOH·H2O at a ratio of Li:(Ni+Co+Mn)=1.10:1 and ball-milled for 6 h. Then, it was placed in a calcining furnace and heated to 600℃ at an oxygen flow rate of 80 sccm. The temperature was first increased to 600℃ at 5℃ / min and held for 2 h, and then increased to 800℃ at 6℃ / min and held for 8 h. After cooling, it was ground to obtain LiNi. 0.92 Co 0.06 Mn 0.02 P 0.005 The mass ratio of Li3PO4 to ZrO2 in the O2@ Li3PO4-ZrO2 composite coating layer is approximately 1:4.

[0052] The coin-type lithium-ion batteries were assembled using the same method as in Example 1, and their performance was tested. The results are shown in Table 1 and... Figure 2 As shown.

[0053] Example 3:

[0054] A phosphorus-doped-coated high-nickel single-crystal lithium-ion battery cathode material of the present invention comprises a high-nickel single-crystal cathode material matrix LiNi. 0.93 Co 0.03 Mn 0.04 P 0.01 The substrate is coated with a Li3PO4-Al2O3 composite coating layer; the coating layer thickness is 20 nm; phosphorus exists in the form of coating and doping, with a surface concentration of 2.0 at% and a substrate concentration of 0.9 at%; the phosphorus-doped-coated high-nickel single-crystal lithium-ion battery cathode material has a particle size of 2-5 μm, a Li / Ni mixing degree ≤1.8%, and a specific surface area of ​​0.8 m². 2 / g.

[0055] The preparation method of the phosphorus-doped-coated high-nickel single-crystal lithium-ion battery cathode material in this embodiment includes the following steps:

[0056] (1) Prepare a 1M solution by mixing nickel sulfate, cobalt sulfate and manganese sulfate in a molar ratio of Ni:Co:Mn=93:3:4, add 1.0 wt% ammonium phosphate as phosphorus source and 0.5 wt% aluminum nitrate, add sodium hydroxide and polyethylene glycol to adjust pH=10, react at 70℃ for 6h, centrifuge and dry to obtain nickel cobalt manganese hydroxide precursor;

[0057] (2) The nickel-cobalt-manganese hydroxide precursor was mixed with LiOH·H2O at a ratio of Li:(Ni+Co+Mn)=1.15:1 and ball-milled for 8 h. Then, it was placed in a calcining furnace and heated to 550℃ at an oxygen flow rate of 120 sccm. The temperature was first increased to 550℃ at 8℃ / min and held for 5 h, and then increased to 750℃ at 2℃ / min and held for 15 h. After cooling, it was ground to obtain LiNi. 0.93 Co 0.03 Mn 0.04 P 0.01 O2@ Li3PO4-Al2O3, the mass ratio of Li3PO4 to Al2O3 in the composite coating layer is approximately 6:1.

[0058] The coin-type lithium-ion batteries were assembled using the same method as in Example 1 and their performance was tested. The results are shown in Table 1.

[0059] Example 4:

[0060] A phosphorus-doped-coated high-nickel single-crystal lithium-ion battery cathode material of the present invention comprises a high-nickel single-crystal cathode material matrix LiNi. 0.94 Co 0.01 Mn 0.05 P 0.03 The substrate is coated with a Li3PO4-Al2O3 composite coating layer; the coating layer thickness is 40 nm; phosphorus exists in the form of coating and doping, with a surface concentration of 2.5 at% and a substrate concentration of 1.2 at%; the phosphorus-doped-coated high-nickel single-crystal lithium-ion battery cathode material has a particle size of 2-5 μm, a Li / Ni mixing degree ≤2.5%, and a specific surface area of ​​1.2 m². 2 / g.

[0061] The preparation method of the phosphorus-doped-coated high-nickel single-crystal lithium-ion battery cathode material in this embodiment includes the following steps:

[0062] (1) Prepare a 1M solution by mixing nickel sulfate, cobalt sulfate and manganese sulfate in a molar ratio of Ni:Co:Mn=94:1:5, add 3.0 wt% diammonium hydrogen phosphate as phosphorus source and 3.0 wt% aluminum nitrate, add ammonia water and polyethylene glycol to adjust pH=11, react at 40℃ for 12 h, centrifuge and dry to obtain nickel cobalt manganese hydroxide precursor;

[0063] (2) The nickel-cobalt-manganese hydroxide precursor was mixed with LiOH·H2O at a ratio of Li:(Ni+Co+Mn)=1.10:1 and ball-milled for 12 h. Then, it was placed in a calcining furnace and heated to 450℃ at an oxygen flow rate of 150 sccm. The temperature was first increased to 450℃ at 5℃ / min and held for 2 h, and then increased to 950℃ at 4℃ / min and held for 8 h. After cooling, it was ground to obtain LiNi. 0.93 Co 0.03 Mn 0.04 P 0.01 The mass ratio of Li3PO4 to Al2O3 in the O2@ Li3PO4-Al2O3 composite coating layer is approximately 4:1.

[0064] The coin-type lithium-ion batteries were assembled using the same method as in Example 1 and their performance was tested. The results are shown in Table 1.

[0065] Example 5:

[0066] A phosphorus-doped-coated high-nickel single-crystal lithium-ion battery cathode material of the present invention comprises a high-nickel single-crystal cathode material matrix LiNi. 0.95 Co 0.02 Mn 0.03 P 0.04 The substrate is coated with a Li3PO4-ZrO2 composite coating layer; the coating layer thickness is 35 nm; phosphorus exists in the form of coating and doping, with a surface concentration of 3 at% and a substrate concentration of 1.2 at%; the phosphorus-doped-coated high-nickel single-crystal lithium-ion battery cathode material has a particle size of 2-5 μm, a Li / Ni mixing degree ≤2.0%, and a specific surface area of ​​0.6 m². 2 / g.

[0067] The preparation method of the phosphorus-doped-coated high-nickel single-crystal lithium-ion battery cathode material in this embodiment includes the following steps:

[0068] (1) Prepare a 1M solution by mixing nickel sulfate, cobalt sulfate and manganese sulfate in a molar ratio of Ni:Co:Mn=95:2:3, add 4.0 wt% diammonium hydrogen phosphate as phosphorus source and 1.5 wt% zirconium nitrate, add sodium carbonate and polyethylene glycol to adjust pH=12, react at 70℃ for 6 h, centrifuge and dry to obtain nickel cobalt manganese hydroxide precursor;

[0069] (2) The nickel-cobalt-manganese hydroxide precursor was mixed with LiOH·H2O at a ratio of Li:(Ni+Co+Mn)=1.05:1 and ball-milled for 16 h. Then, it was placed in a calcining furnace and heated to 400℃ at an oxygen flow rate of 200 sccm and held for 5 h at a rate of 6℃ / min. Then, it was heated to 900℃ at a rate of 6℃ / min and held for 10 h. After cooling, it was ground to obtain LiNi. 0.95 Co 0.02 Mn0.03 P 0.04 The mass ratio of Li3PO4 to ZrO2 in the O2@ Li3PO4-ZrO2 composite coating layer is approximately 5:1.

[0070] The coin-type lithium-ion batteries were assembled using the same method as in Example 1 and their performance was tested. The results are shown in Table 1.

[0071] Comparative Example 1:

[0072] The only difference between the preparation method of the cathode material in this comparative example and that in Example 1 is that no phosphorus source is added in step (1). The rest is the same as in Example 1.

[0073] The coin-type lithium-ion batteries were assembled using the same method as in Example 1, and their performance was tested. The results are shown in Table 1 and... Figure 2 As shown.

[0074] As shown in Table 1, the coin-type lithium-ion battery assembled in this comparative example has a first charge-discharge specific capacity of 253.59 mAh / g and 210.71 mAh / g at 0.1C, respectively, and a coulombic efficiency of 83.09%.

[0075] like Figure 2 As shown, the coin cell lithium-ion battery assembled in this comparative example retains only 73.74% of its discharge capacity after 200 cycles at a 0.5 C rate.

[0076] Comparative Example 2:

[0077] The difference between the preparation method of the positive electrode material in this comparative example and that in Example 1 is that 1.5 wt% aluminum nitrate is not added in step (1), otherwise it is the same as in Example 1.

[0078] The coin-type lithium-ion batteries were assembled using the same method as in Example 1 and their performance was tested. The results are shown in Table 1.

[0079] Comparative Example 3:

[0080] The difference between the preparation method of the positive electrode material in this comparative example and that in Example 1 is only that the sintering procedure in step (2) is different: this comparative example only performs one sintering step, with the temperature of aluminum plating increased from room temperature to 850°C at a rate of 10°C / min, and the temperature is held for 12 hours. The rest is the same as in Example 1.

[0081] Comparative Example 4:

[0082] The preparation method of the cathode material in this comparative example specifically includes the following steps:

[0083] (1) Prepare a 1M solution by mixing nickel sulfate, cobalt sulfate and manganese sulfate in a molar ratio of Ni:Co:Mn=90:5:5, adjust the pH to 11 by adding ammonia dropwise, react at 60℃ for 8 h, centrifuge and dry to obtain nickel cobalt manganese hydroxide precursor;

[0084] (2) The nickel-cobalt-manganese hydroxide precursor was mixed with LiOH·H2O at a ratio of Li:(Ni+Co+Mn)=1.05:1, and ammonium dihydrogen phosphate (2.0 wt% of the total mass of nickel sulfate, cobalt sulfate, and manganese sulfate) and aluminum nitrate (1.5 wt%) were added. The mixture was ball-milled for 4 h, and then placed in a calcining furnace. Under an oxygen flow rate of 100 sccm, the temperature was first increased to 500℃ at 10℃ / min and held for 3 h, and then increased to 850℃ at 5℃ / min and held for 12 h. After cooling, the mixture was ground to obtain LiNi. 0.9 Co 0.05 Mn 0.05 O2@Li3PO4-Al2O3.

[0085] Comparative Example 5:

[0086] The preparation method of the cathode material in this comparative example specifically includes the following steps:

[0087] (1) Prepare a 1M solution by mixing nickel sulfate, cobalt sulfate and manganese sulfate in a molar ratio of Ni:Co:Mn=90:5:5. Add ammonium dihydrogen phosphate (2wt% of the total mass of nickel sulfate, cobalt sulfate and manganese sulfate) as a phosphorus source and add ammonia water to adjust the pH=11. Then react at 60℃ for 8 h, centrifuge and dry to obtain nickel cobalt manganese hydroxide precursor.

[0088] (2) The nickel-cobalt-manganese hydroxide precursor was mixed with LiOH·H2O at a ratio of Li:(Ni+Co+Mn)=1.05:1, and aluminum nitrate accounting for 1.5wt% of the total mass of nickel sulfate, cobalt sulfate, and manganese sulfate was added. The mixture was ball-milled for 4 h, and then placed in a calcining furnace. Under an oxygen flow rate of 100 sccm, the temperature was first raised to 500℃ at 10℃ / min and held for 3 h, and then raised to 850℃ at 5℃ / min and held for 12 h. After cooling, the mixture was ground to obtain LiNi. 0.9 Co 0.05 Mn 0.05 P 0.02 O2@Al2O3.

[0089] Table 1. Electrochemical performance of batteries assembled from the electrode sheets prepared in Examples 1-5 and Comparative Examples 1-5.

[0090]

[0091] As shown in Table 1, the reversible discharge specific capacity of the batteries assembled with the electrode sheets prepared in Examples 1-5 of the present invention can reach up to 218.37 mAh / g, the initial coulombic efficiency can reach up to 88.69%, and the cycle stability is better than that of the batteries assembled with the electrode sheets prepared in Comparative Examples 1-3 of the present invention.

[0092] From Table 1, Figure 2 It can be seen that the battery assembled with the electrode sheet prepared in Example 1 of the present invention can still maintain a discharge capacity of 87.43% after 200 cycles at 0.5C. This indicates that phosphorus doping-coating can suppress cation mixing, reduce surface side reactions, and optimize structural stability. At the same time, the appropriate sintering temperature and coating / phosphorus doping synergistically improve the cycle performance. Comparative Example 1, without phosphorus doping, showed a slight increase in capacity, but increased surface side reactions, decreased structural stability, and exacerbated lattice distortion during cycling. Comparative Example 2 showed surface side reactions leading to loss of active material, a slight decrease in capacity, accelerated surface layer damage, and increased particle pulverization / microcracks. Comparative Example 3 showed uneven crystallinity in single-stage sintering, worsened lithium diffusion kinetics, and crystal defects hindered lithium insertion / extraction, resulting in stress accumulation within the particles and accelerated structural collapse during cycling. In Comparative Example 4, phosphorus existed only on the particle surface as Li3PO4, with no effective bulk doping. The Al2O3 coating layer was unevenly distributed and loosely bonded to Li3PO4, easily detaching during cycling, triggering interfacial side reactions, exacerbating structural stress, and causing performance degradation. In Comparative Example 5, phosphorus existed only in the particle interior as bulk doping, with no effective surface composite coating. This exacerbated surface side reactions, making microcracks and phase transitions more likely, leading to loss of active lithium and accelerated capacity decay. In summary, the method of this invention, through phosphorus doping-coating and co-precipitation combined with two-stage sintering, produces a single-crystal high-nickel cathode material that can suppress lattice distortion and enhance structural stability, significantly improving cycle stability, and providing an innovative path for high-energy-density power batteries.

Claims

1. A method for preparing a phosphorus-doped-coated high-nickel single-crystal lithium-ion battery cathode material, characterized in that, The phosphorus-doped-coated high-nickel single-crystal lithium-ion battery cathode material comprises a high-nickel single-crystal cathode material matrix LiNi x Co y Mn z P a O2, the surface of the matrix is coated with a Li3PO4-Al2O3 composite coating layer or a Li3PO4-ZrO2 composite coating layer, wherein 0.90≤x≤0.95, 0≤y≤0.10, 0≤z≤0.10, 0.001≤a≤0.05, and the preparation method comprises the following steps: (1) prepare a mixed solution of nickel salt, cobalt salt and manganese salt; add a phosphorus source, a precipitant and a M metal salt to the mixed solution to perform a co-precipitation reaction, thereby obtaining a precursor; wherein the M metal salt comprises one or more of aluminum nitrate and zirconium oxy nitrate; the M metal salt is added in an amount of 0.1%-3.0% of the total mass of the nickel salt, the cobalt salt and the manganese salt; the phosphorus source is one or more of ammonium phosphate, diammonium hydrogen phosphate or ammonium dihydrogen phosphate, and is added in an amount of 0.5%-5.0% of the total mass of the nickel salt, the cobalt salt and the manganese salt; and the pH value of the reaction system is controlled to be 10-12 during the co-precipitation reaction; (2) mix the precursor with a lithium source, and then perform sintering, thereby obtaining the phosphorus-doped and coated high-nickel single-crystal lithium ion battery positive electrode material; wherein the sintering is performed in an oxygen atmosphere, including first heating at a heating rate of 5-10 ℃ / min to 400-600 ℃, maintaining for 2-5 h, and then heating at a heating rate of 2-10 ℃ / min to 750-950 ℃, maintaining for 8-15 h.

2. The production method according to claim 1, wherein In step (1), the co-precipitation reaction is stirred at 40-80 ℃ for 4-12 h.

3. The production method according to claim 1, wherein In step (1), the nickel salt, the cobalt salt and the manganese salt are added in an amount calculated according to a molar ratio of Ni:Co:Mn of 90-95:0-10:0-10. In step (2), the lithium source and the precursor are added in an amount calculated according to a molar ratio of Li:(Ni+Co+Mn) of 1.05-1.15:

1.

4. The production method according to claim 1, wherein In step (1), the precipitant is one or more of sodium hydroxide, sodium carbonate or ammonia water; and a complexing agent is further added during the co-precipitation reaction, wherein the complexing agent is ammonia water or polyethylene glycol, and the molar ratio of the complexing agent to the total moles of the nickel salt, the cobalt salt and the manganese salt is 1:1-3:

1.

5. The production method according to claim 1, characterized by, In step (2), the flow rate of the oxygen atmosphere during the sintering is 50-200 sccm.

6. The production method according to claim 1, wherein The coating layer has a thickness of 10-50 nm, and the phosphorus element exists in the form of coating and doping, with a surface atomic percentage concentration of 1.5-3 at% and a matrix atomic percentage concentration of 0.8-1.2 at%.

7. The production method according to claim 1, wherein The particle size of the phosphorus-doped-coated high-nickel single-crystal lithium ion battery positive electrode material is 2-5 mu m, the Li / Ni mixed arrangement degree is less than or equal to 2.5%, and the specific surface area is 0.5-2.0 m 2 / g.

8. The production method according to claim 1, wherein The mass ratio of Li3PO4 to Al2O3 in the composite coating layer is 1:4-10:1; or the mass ratio of Li3PO4 to ZrO2 is 1:4-10:1.

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