A modified high-nickel ternary cathode material and its preparation method and application

Abstract

The present invention discloses a modified high-nickel ternary cathode material, its preparation method, and application. The preparation method comprises the following steps: preparing a modified precursor: depositing Al(H2PO4)3 on the surface of the high-nickel ternary cathode material precursor using a wet deposition method to obtain the modified precursor; and lithiation sintering: subjecting the modified precursor to a single sintering treatment with a lithium source to obtain the modified high-nickel ternary cathode material. During the lithiation sintering step, the amount of lithium source added includes the amount of lithium source required to convert the precursor into the cathode material, the amount of lithium source required for the reaction of Al(H2PO4)3 with LiOH·H2O at a molar ratio of 1:10, and the amount of lithium source required to compensate for lithium volatilization during the sintering process. The high-nickel ternary cathode material is obtained by treating the high-nickel ternary precursor with Al(H2PO4)3 and then lithiation sintering. The high-nickel ternary cathode material has excellent properties, including high specific capacity, good cycle stability, and slow impedance growth.

Description

Technical Field

[0001] The present invention relates to the technical field of battery materials, and in particular to a modified high-nickel ternary positive electrode material and a preparation method and application thereof. Background Art

[0002] Lithium-ion batteries (LIBs) have become the mainstream of new energy power batteries due to their combined advantages, including high operating voltage and high energy density. Currently, commercial power battery anode materials mostly use graphite or silicon-based materials as active materials, while cathode materials primarily use lithium iron phosphate (LIFP) and layered ternary materials as active materials. The positive electrode material is the most core and costly component of a lithium battery, accounting for approximately 30%-40%. Furthermore, the specific capacity of the anode material is higher than that of the cathode material, thus limiting battery capacity expansion. Among the various battery cathode materials, high-nickel ternary cathode materials can achieve an actual discharge specific capacity exceeding 200 mAh / g, significantly exceeding both LFP and conventional ternary materials. Furthermore, their lower Co content than medium- and low-nickel ternary materials contributes to their lower cost, making them highly promising cathode materials. However, high-nickel ternary cathode materials exhibit high surface activity, leading to severe electrode-electrolyte interface side reactions during charge-discharge cycling, which can lead to microcracks, rapid impedance growth, and transition metal dissolution. These interfacial side reactions severely impair the cycling stability of high-nickel ternary cathode materials, becoming a key factor limiting their commercialization.

[0003] In response to market demand, high nickel ternary cathode materials mainly use coating, doping and other methods to improve performance. Coating is an effective strategy to stabilize the interface and inhibit the decomposition of the electrolyte. Coating can reduce the direct contact between the active material and the electrolyte, thereby avoiding the corrosion of the electrolyte on the cathode material, ensuring the structural morphology of the cathode material is intact, slowing down the material capacity decay, and at the same time reducing Li when forming the SEI film. + Overconsumption. Fast ion conductors such as Li3PO4 or LiAlO2 offer unique advantages as coating materials. They act as a physical barrier separating the electrolyte and the cathode surface, scavenging HF. Due to their excellent ionic conductivity, a fast ion conductor coating of appropriate thickness does not cause a loss in rate performance.

[0004] At present, most coating and surface doping modification technologies are based on secondary sintering of ternary cathode materials, which greatly increases production costs. For example, CN110611093A discloses a method for preparing a surface-coated modified high-nickel ternary cathode material for lithium-ion batteries. The method first disperses the high-nickel ternary cathode material in anhydrous ethanol, then adds a saturated solution of Al(H2PO4)3 thereto, stirs, evaporates and dries, and then performs secondary sintering to obtain a coated sample. The purpose of this method is to utilize the chemical reaction of residual alkali on the surface of the high-nickel ternary cathode material with Al(H2PO4)3 to eliminate the residual alkali while forming a Li3PO4-AlPO4 coating layer to improve the electrochemical performance of the material. However, this method requires secondary sintering of the cathode material, which increases energy consumption.

[0005] There are also technologies for surface treatment of precursors. For example, CN116282218A discloses a method for preparing a nickel-zirconium-manganese ternary precursor in situ coated with Al(H2PO4)3. The precursor filter cake obtained by coprecipitation is wet-mixed with Al(H2PO4)3 in an aqueous system. The Al(H2PO4)3-coated nickel-zirconium-manganese ternary precursor is then pre-calcined at low temperature to produce the Al(H2PO4)3-coated nickel-zirconium-manganese ternary precursor. The precursor is then sintered with lithium in a normal manner, with the expectation that a Li3PO4-AlPO4 coating will form on the surface of the positive electrode material. Summary of the Invention

[0006] The present invention addresses the technical problem that prior art coating and modification of cathode materials typically requires a secondary sintering process. This invention addresses this problem by providing a modified high-nickel ternary cathode material, its preparation method, and its application. The material is obtained by treating a high-nickel ternary precursor with Al(H2PO4)3 and then performing lithiated sintering. This high-nickel ternary cathode material exhibits excellent properties, including high specific capacity, good cycle stability, and slow impedance growth.

[0007] The present invention is achieved through the following technical solutions:

[0008] A method for preparing a modified high-nickel ternary cathode material comprises the following steps:

[0009] Preparation of modified precursor: Al(H2PO4)3 is deposited on the surface of the precursor of high nickel ternary cathode material by wet deposition method to obtain modified precursor;

[0010] Lithiation sintering: The modified precursor and lithium source are sintered once to obtain a modified high-nickel ternary cathode material;

[0011] In the lithiation sintering process, the amount of lithium source added includes the amount of lithium source required to transform the precursor into the positive electrode material, the amount of lithium source required for the reaction of Al(H2PO4)3 and LiOH·H2O at a molar mass ratio of 1:10, and the amount of lithium volatilized during the sintering process. Regarding the amount of lithium source added: 1) The amount of lithium source required for the reaction of Al(H2PO4)3 and LiOH·H2O. It should be noted that the content of Al(H2PO4)3 is much less than that of the precursor and is located on the surface. Therefore, it will preferentially react with sufficient LiOH·H2O, that is, react according to the molar mass ratio of Al(H2PO4)3 to LiOH·H2O of 1:10. This part of lithium needs to be added additionally to prevent lithium deficiency in the material. 2) The amount of lithium source required to transform the precursor into the positive electrode material. 3) The amount of lithium volatilized during the sintering process is about 5wt% of the lithium in 2).

[0012] This preparation method utilizes Al(H2PO4)3 to modify the precursor of a high-nickel ternary cathode material. Al(H2PO4)3 serves as both an Al and P source. The chemical reaction between the lithium source and Al(H2PO4)3 during sintering allows for the coating of the ternary cathode material with the Li3PO4-LiAlO2 fast ion conductor. This modification stabilizes the cathode material's interface, resulting in excellent rate performance and cycling stability, overcoming the shortcomings of traditional coating methods.

[0013] The present invention first uses a wet deposition method to uniformly deposit Al(H2PO4)3 on the surface of the cathode material precursor, overcoming the disadvantage of the solid-phase mixing method that requires ball milling, which causes the precursor to break. Then, during the physical and chemical sintering stage, part of the lithium source is used to convert the precursor into the cathode material. Part of the lithium source reacts with Al(H2PO4)3 to form a composite coating on the surface of the cathode material. The specific principle is: in the subsequent lithiation sintering stage, lithium is accurately distributed, and Al(H2PO4)3 and a sufficient amount of LiOH·H2O are converted into Li3PO4 and LiAlO2 according to the chemical reaction equation (1) to form a coating.

[0014] (1).

[0015] The present invention deposits a layer of Al(H2PO4)3 on the surface of the ternary positive electrode precursor in an ethanol system, and when adding lithium, the lithium salt required to react with Al(H2PO4)3 to generate Li3PO4-LiAlO2 is accurately added (the molar ratio of Al(H2PO4)3 to lithium is 1:10), ensuring that the generated coating is Li3PO4-LiAlO2, rather than reacting with a small amount of residual lithium to generate a Li3PO4-AlPO4 coating layer, and the modification can be achieved by only one sintering.

[0016] Alternatively, the chemical formula of the precursor of the high nickel ternary cathode material is Nix Co y Mn z (OH)2 or Ni x Co y Al z (OH)2; wherein 0.5≤x<1.0, 0<y≤0.30, 0<z≤0.30 and x+y+z=1;

[0017] And / or, the lithium source includes at least one of LiOH·H2O or Li2CO3.

[0018] Further optionally, in the step of preparing the modified precursor, the amount of Al(H2PO4)3 used is 0.3wt%-2.0wt% of the amount of the precursor of the high-nickel ternary positive electrode material.

[0019] For Al(H2PO4)3, too little is not conducive to forming an effective coating. Excessive use, on the one hand, reduces the mass percentage of the electrode active material, resulting in a decrease in energy density; on the other hand, too thick a coating or large-scale agglomeration will hinder lithium ion transmission, which is not conducive to the material's rate performance.

[0020] Further optionally, the step of preparing the modified precursor specifically includes:

[0021] The high nickel ternary cathode material precursor and Al(H2PO4)3 are added to ethanol and evaporated by stirring to obtain a solid powder.

[0022] The obtained solid powder is dried to obtain an Al(H2PO4)3 modified high nickel ternary precursor.

[0023] Further optionally, during the evaporation process, the temperature is set to 30°C-70°C;

[0024] And / or, during the drying process, the drying temperature is set to 60°C-120°C.

[0025] Further optionally, the step of lithiation sintering specifically includes: performing a gradient temperature rising sintering process in a pure oxygen atmosphere.

[0026] Further optionally, in a pure oxygen atmosphere, the temperature is raised from room temperature to 480° C.-550° C. and sintered for 3 h-5 h, and then further raised to 750° C.-800° C. and sintered for 12 h-15 h.

[0027] A modified high-nickel ternary cathode material, the surface of which is coated with a Li3PO4 and LiAlO2 composite coating.

[0028] Further optionally, the material is prepared by the above-mentioned method for preparing the modified high-nickel ternary positive electrode material.

[0029] A positive electrode plate or a lithium battery includes a positive electrode material prepared from the above-mentioned modified high-nickel ternary positive electrode material, or includes the above-mentioned modified high-nickel ternary positive electrode material.

[0030] The present invention has the following advantages and beneficial effects:

[0031] The present invention provides a modified high-nickel ternary cathode material and a preparation method thereof, which uses a fast ion conductor for coating, stabilizes the material interface, and improves the cycle performance of the high-nickel ternary cathode.

[0032] The present invention addresses the problem that the coating modification based on the positive electrode material in the prior art requires an additional annealing step. The present invention first adopts a wet deposition method to uniformly deposit Al(H2PO4)3 on the surface of the positive electrode material precursor, overcoming the disadvantage that the solid phase mixing method requires ball milling, which causes the precursor to break. In the next lithiation sintering stage, the additional required lithium source is compensated, and the Al(H2PO4)3 deposited on the surface of the precursor preferentially reacts with LiOH·H2O or Li2CO3 to generate Li3PO4 and LiAlO2 to form a mixed coating on the surface of the positive electrode material. The fast ion surface coating stabilizes the interface of the positive electrode material, effectively suppresses the electrode-electrolyte interface side reactions, and improves the cycle stability of the positive electrode material. The wet deposition method based on the precursor can deposit more uniformly and only requires one sintering, which is lower in cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the drawings:

[0034] Figure 1 This is the SEM image of the positive electrode material prepared in Comparative Example 1.

[0035] Figure 2 This is the SEM image of the positive electrode material prepared in Example 1.

[0036] Figure 3 The graph shows the cycle performance of the positive electrode materials prepared in Example 1 and Comparative Example 1 after 100 cycles at 0.5C.

[0037] Figure 4 This is a rate performance diagram of the positive electrode materials prepared in Example 1 and Comparative Example 2. DETAILED DESCRIPTION

[0038] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with examples and drawings. The exemplary embodiments of the present invention and their descriptions are only used to explain the present invention and are not intended to limit the present invention. Example

[0039] This embodiment provides a modified high nickel ternary positive electrode material. In this embodiment, the chemical formula of the high nickel ternary positive electrode precursor selected is Ni 0.8 Co 0.1 Mn 0.1 The amount of (OH)2 and Al(H2PO4)3 used is 0.5wt% of the precursor amount, and the target material prepared is marked as 0.5wt%AlP-NCM811. The specific preparation process is as follows:

[0040] Step 1: Weigh 2g Ni 0.8 Co 0.1 Mn 0.1 (OH)2, 0.01g Al(H2PO4)3, add 10ml ethanol as a dispersant to obtain a suspension, and fully disperse it by stirring.

[0041] Step 2: The suspension in step 1 was stirred and evaporated in an oil bath at 70°C until only mixed solid powder remained, and then thoroughly dried in an oven and collected to obtain a modified precursor.

[0042] Step 3: Weigh 1 g of the modified precursor obtained in Step 2 and grind with 0.4778 g of LiOH·H₂O until uniformly mixed. The mixed powder was pre-sintered in a tube furnace under an O₂ atmosphere at a heating rate of 3°C / min to 480°C for 3 h. The temperature was then raised to 750°C and sintered for 12 h. The mixture was then cooled to room temperature to obtain the target material, 0.5 wt% AlP-NCM811. Example

[0043] This embodiment provides a modified high nickel ternary positive electrode material. In this embodiment, the chemical formula of the high nickel ternary positive electrode precursor selected is Ni 0.8 Co 0.1 The amount of Mn0.1(OH) and Al(H2PO4)3 used is 1.0wt% of the precursor amount, and the target material prepared is marked as 1.0wt%AlP-NCM811. The specific preparation process is as follows:

[0044] Step 1: Weigh 2g Ni 0.8 Co 0.1 Mn 0.1 (OH)2, 0.02g Al(H2PO4)3, add 10ml ethanol as a dispersant to obtain a suspension, and fully disperse it by stirring.

[0045] Step 2: Stir and evaporate the suspension in step 1 in an oil bath at 70°C until only mixed solid powder remains, and then dry it thoroughly in an oven.

[0046] Step 3: Weigh 1 g of the modified precursor obtained in Step 2 and grind with 0.4820 g of LiOH·H₂O until uniformly mixed. The mixed powder was pre-sintered in a tube furnace under an O₂ atmosphere at a rate of 3°C / min to 480°C for 3 h. The temperature was then raised to 750°C and sintered for 12 h. The mixture was then cooled to room temperature to obtain the target material, 1.0 wt% AlP-NCM811. Example

[0047] This embodiment provides a modified high nickel ternary positive electrode material. In this embodiment, the high nickel ternary positive electrode precursor chemical formula is Ni 0.8 Co 0.1 The amount of Mn0.1(OH)2 and Al(H2PO4)3 used is 2.0wt% of the precursor amount, and the target material prepared is marked as 2.0wt%AlP-NCM811. The specific preparation process is as follows:

[0048] Step 1: Weigh 2g Ni 0.8 Co 0.1 Mn 0.1 (OH)2, 0.04g Al(H2PO4)3, add 10ml ethanol as a dispersant to obtain a suspension, and fully disperse it by stirring.

[0049] Step 2: Stir and evaporate the suspension in step 1 in an oil bath at 70°C until only mixed solid powder remains, and then dry it thoroughly in an oven.

[0050] Step 3: Weigh 1 g of the modified precursor obtained in Step 2 and grind with 0.4904 g of LiOH·H₂O until uniformly mixed. The mixed powder was pre-sintered in a tube furnace at a rate of 3°C / min to 480°C under an O₂ atmosphere for 3 h. The temperature was then raised to 750°C and sintered for 12 h. The mixture was then cooled to room temperature to obtain the target material, 2.0 wt% AlP-NCM811.

[0051] Comparative Example 1

[0052] This case discloses the use of unmodified Ni 0.8 Co 0.1 A preparation method for ternary positive electrode materials using Mn0.1(OH)2 precursor by traditional solid phase method.

[0053] Weigh 1g Ni 0.8 Co 0.1 Mn 0.1 (OH)2 precursor and 0.4735g LiOH·H2O. 0.8 Co 0.1 Mn 0.1The (OH)2 precursor is mixed evenly with LiOH·H2O, and then heated to 480℃ at a heating rate of 3℃ / min in a tube furnace under O2 atmosphere and sintered for 3h, then continued to heat to 750℃ and sintered for 12h, and finally cooled to room temperature to obtain lithium-ion battery LiNi 0.8 Co 0.1 Mn 0.1 O2 positive electrode material, marked as NCM811.

[0054] Comparative Example 2

[0055] This case study describes a modified high-nickel ternary cathode material. Similar to Example 1, this case utilizes 0.5wt% Al(H2PO4)3 for modification. However, the lithium source required for the reaction of Al(H2PO4)3 with LiOH·H2O is not added. The target material is un-lithium-supplemented 0.5wt% AlP-NCM811. The specific preparation process is as follows:

[0056] Step 1: Weigh 2g Ni 0.8 Co 0.1 Mn 0.1 (OH)2, 0.01g Al(H2PO4)3, add 10ml ethanol as a dispersant to obtain a suspension, and fully disperse it by stirring.

[0057] Step 2: Stir and evaporate the suspension in step 1 in an oil bath at 70°C until only mixed solid powder remains, and then dry it thoroughly in an oven.

[0058] Step 3: Weigh 1 g of the modified precursor obtained in Step 2 and grind with 0.4735 g of LiOH·H₂O until uniformly mixed. The mixed powder was pre-sintered in a tube furnace at a rate of 3°C / min to 480°C under an O₂ atmosphere for 3 h. The temperature was then raised to 750°C and sintered for 12 h. The mixture was then cooled to room temperature to obtain the target material, AlP-NCM811 (0.5 wt% AlP without lithium supplementation).

[0059] 1. Characterization and Analysis

[0060] Figure 1 This is an SEM image of the positive electrode material prepared in Comparative Example 1. It can be seen that the surface of the unmodified ternary positive electrode material particles is clean and free of impurities, and the gaps between the primary particles are very clear.

[0061] Figure 2 This is an SEM image of the cathode material prepared in Example 1. The modified ternary cathode material particles have a smoother surface, as the coating material fills the gaps between the primary particles. The dark, dense phase is the result of enrichment of the coating material, demonstrating the successful coating of the Li₃PO₄-LiAlO₂ coating on the material surface.

[0062] 2. Performance Testing

[0063] 1. Test method

[0064] 1.1 Preparation of positive electrode

[0065] Weigh the positive electrode material, conductive carbon black (Super P), and binder (PVDF) in a mass ratio of 8:1:1 and place them in an agate mortar until thoroughly mixed. Use a dropper to add an appropriate amount of NMP (N-methylpyrrolidone) as a dispersant and mix thoroughly until the slurry reaches an appropriate viscosity. Use a coater to evenly coat the slurry on aluminum foil and dry it in a vacuum oven at 80°C for 12 hours. Use a coater to evenly coat the slurry on aluminum foil and dry it in a vacuum oven at 80°C for 12 hours.

[0066] 1.2 Assembling the button battery

[0067] The positive and negative battery cases, separators, nickel mesh, and positive electrode sheet were dried for 2 hours and then transferred to a glove box under a high-purity argon atmosphere. The battery case used was a CR2025 model. The positive electrode material was a thin sheet with a diameter of 14 mm. The counter electrode was a high-purity lithium sheet with a diameter of 14.5 mm and a diameter of 0.58 mm. The electrolyte consisted of a 1 mol / L solution of LiPF6 and a 1:1:1 volume ratio of ethylene carbonate and dimethyl carbonate. Two drops of electrolyte were added to the center of the positive electrode case. Then, the ternary positive electrode sheet was placed in the center of the positive electrode case with the coating facing up. Two more drops of electrolyte were added to ensure thorough soaking. A polypropylene microporous separator was placed on top of the positive electrode sheet, ensuring that no bubbles formed. Another drop of electrolyte was added. The lithium sheet, nickel foam, and negative electrode case were then placed in that order, aligning the positive and lithium sheets in the center of the button cell. The assembled button cell was removed and sealed using a sealing machine at a pressure of 50 kg / cm².

[0068] 1.3 Charge and discharge test

[0069] After assembling the button cell, the battery was left to stand at room temperature for 12 hours to allow the electrolyte to completely soak into the battery. The experiment used a LAND-BT2013A model device, and all tests were conducted at room temperature (30°C). The constant current charge and discharge tests in this article were conducted on a CT2001A channel of a LAND Electronic Co. battery test system. The test temperature was 30°C, and the voltage range was 2.8-4.3 V. The constant current charge step was followed by a constant voltage charge process. Five rate test intervals were set: 0.1C, 0.2C, 0.5C, 1C, and 2C. The cycle test began with activation at 0.1C, followed by charging at 0.2C and discharging at 0.5C.

[0070] 2. Test results

[0071] Figure 3 The figure shows the 100-cycle performance of the positive electrode materials prepared in Example 1 and Comparative Example 1 at 0.5C. It can be seen that the capacity retention rate of the modified material is significantly improved.

[0072] Figure 4 The figure shows the rate performance of the positive electrode materials prepared in Example 1 and Comparative Example 2. It can be seen that without the addition of the lithium source required for the reaction of Al(H2PO4)3 with LiOH·H2O, the material's capacity and rate performance deteriorate. Furthermore, it can be inferred that the greater the amount of Al(H2PO4)3 used, the more additional lithium source is required, and the greater the performance difference between the materials with and without lithium supplementation.

[0073] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a modified high-nickel ternary cathode material, characterized in that: The steps include: preparing a modified precursor: depositing a modified precursor on the surface of a precursor of a high nickel ternary cathode material by a wet deposition method; Al(H2PO4)3, to obtain a modified precursor; The steps of preparing the modified precursor specifically include: adding a high-nickel ternary positive electrode material precursor and Al(H2PO4)3 to ethanol, and obtaining a residual solid powder by stirring and evaporating, wherein the amount of Al(H2PO4)3 is 0.3wt%-2.0wt% of the amount of the high-nickel ternary positive electrode material precursor; drying the obtained solid powder to obtain an Al(H2PO4)3-modified high-nickel ternary precursor; during the evaporation process, setting the temperature to 30°C-70°C; and / or, during the drying process, setting the drying temperature to 60°C-120°C; Lithiation sintering: The modified precursor and the lithium source are subjected to a single sintering treatment to obtain a modified high-nickel ternary positive electrode material; in the lithiation sintering treatment step, the amount of lithium source added includes the amount of lithium source required for the precursor to be converted into the positive electrode material, the amount of lithium source required for the reaction of Al(H2PO4)3 and LiOH·H2O at a molar mass ratio of 1:10, and the amount of lithium volatilized during the sintering process; the lithiation sintering step specifically includes: performing a gradient temperature rise sintering treatment in a pure oxygen atmosphere, that is, in a pure oxygen atmosphere, heating from room temperature to 480℃-550℃ and sintering for 3h-5h, and then continuing to heat to 750℃-800℃ and sintering for 12h-15h, and the molar ratio of LiAlO2 and Li3PO4 in the formed coating is 1:

3.

2. The method for preparing a modified high-nickel ternary cathode material according to claim 1, characterized in that: The chemical formula of the precursor of high nickel ternary cathode material is Ni x Co y Mn z (OH)2 or Ni x Co y Al z (OH)2; wherein, 0.5≤x<1.0, 0<y≤0.30, 0<z≤0.30 and x+y+z=1; and / or, the lithium source comprises at least one of LiOH·H2O or Li2CO3.

3. A modified high nickel ternary cathode material, characterized in that: Obtained by the preparation method according to claim 2.

4. A positive electrode sheet comprising a positive electrode material obtained by the preparation method of a modified high-nickel ternary positive electrode material according to any one of claims 1 to 2.

5. A lithium battery comprising a positive electrode material obtained by the preparation method of a modified high-nickel ternary positive electrode material according to any one of claims 1 to 2, or comprising a positive electrode plate according to claim 4.

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