Positive electrode material precursor for solid-state battery, preparation method thereof and positive electrode material

Abstract

This invention discloses a precursor for a cathode material used in solid-state batteries, its preparation method, and the cathode material itself. The precursor has the chemical formula aNi. x Co y Mn z M k (OH)2@bLi3PO4·cTiO(OH)2·dAl(OH)3, satisfying specific component ratios and physicochemical parameters; preparation employs a stepwise co-precipitation method, sequentially and quantitatively coating Li3PO4, TiO(OH)2, and Al(OH)3 to achieve atomically uniform doping and coating. The cathode material is prepared by a two-step sintering of the precursor and lithium source, with the chemical formula aLiNi. x Co y Mn z M k O2@b / 3Li 1.3 Al 0.3 Ti 1.7 (PO4)3 exhibits a specific peak intensity ratio across its crystal planes. This invention can prevent the formation of impurity phases, mitigate aluminum loss, suppress structural collapse, construct efficient lithium-ion transport channels, improve interface compatibility, reduce impedance, enhance the cycle stability of solid-state batteries, and adapt to large-scale production.

Description

Technical Field

[0001] This invention relates to the field of positive electrode materials for batteries, specifically to precursors for positive electrode materials used in solid-state batteries, their preparation methods, and the positive electrode materials themselves. Background Technology

[0002] Unlike liquid electrolytes, which can freely permeate into the electrode and form a good ion conduction network, solid electrolytes, due to their non-rheological state, cannot spontaneously permeate into the gaps in the electrode material. The contact between two rigid / brittle solids in a solid system is a "static hard contact." This "static hard contact" results in a small contact area between the electrode and the electrolyte, insufficient ion transport paths, and a decline in electrochemical performance. In addition, the rough surfaces of the electrode and electrolyte contain numerous protrusions and pores, and the numerous interfacial gaps become "empty road barriers" for ion transport, further reducing the effectiveness of the interfacial contact.

[0003] Surface modification of electrode materials is one of the effective means to alleviate the interface problem between the electrode and the electrolyte. Conventional solid-phase coating methods suffer from uneven coating layers, resulting in limited improvement on the interface problem. Liquid-phase coating methods offer more uniform coating, significantly improve the interface problem, and are suitable for large-scale production. Patent CN114057235A discloses a method for coating LATP (lithium aluminum titanium phosphate) onto a nickel-cobalt-manganese ternary precursor. By coating the surface of the ternary precursor with a layer of LATP (a solid electrolyte with stable and rapid lithium-ion transport channels), the cycle performance of high-nickel ternary cathode materials is significantly improved. The above-described scheme uses a mixed solution of lithium and aluminum as the base solution (pH: 4-5), adds a nickel-cobalt-manganese ternary precursor, then adds ammonium bicarbonate solution and mixes thoroughly. Finally, ammonium dihydrogen phosphate solution and titanium salt solution are added separately to react and obtain a nickel-cobalt-manganese ternary precursor coated with LATP. This scheme has some drawbacks. For example, the nickel-cobalt-manganese ternary precursor is prone to partial dissolution of nickel, cobalt, and manganese elements in the base solution at pH 4-5. During the subsequent addition of ammonium bicarbonate solution, nickel, cobalt, manganese, and aluminum elements are re-co-precipitated, and lithium carbonate precipitate is formed, causing the loss of aluminum and lithium elements, thus affecting the elemental ratio in LATP. In addition, due to the low Ksp of lithium phosphate (25℃, 9.84×10⁻⁶), the reaction can be difficult. -21 The small size of the LATP makes it prone to forming lithium phosphate precipitate during the reaction, which further impures the coated LATP, resulting in a coating of multiple components and reducing the improvement of electrical performance.

[0004] Therefore, how to prepare a LATP uniformly coated ternary cathode material precursor for solid-state batteries has become the problem to be solved by this invention. Summary of the Invention

[0005] The purpose of this invention is to provide a cathode material precursor for solid-state batteries, its preparation method, and the cathode material itself.

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

[0007] A precursor for the cathode material in solid-state batteries, with the chemical formula aNi. x Co y Mn z M k (OH)2@bLi3PO4·cTiO(OH)2·dAl(OH)3, where M is one or more of La and Zr, 0.9≤x<1, 0<y<0.1, 0<z<0.1, 0≤k<0.003, and x+y+z+k=1, b / (3a+b)=3c / (10a+3c)=17d / (10a+17d)=0.0004~0.0008, b:c:d=3:1.7:0.3;

[0008] D50 is 2.0~4.0µm, and tap density is 1.8~2.2g / cm³. 3 Particle size distribution: 0.5 < (D90 - D10) / D50 < 0.8; specific surface area: 2~8 m². 2 / g.

[0009] Furthermore, the present invention also discloses a method for preparing a cathode material precursor for solid-state batteries, the method comprising:

[0010] Step 1: Dissolve the soluble salts of Ni, Co, Mn, and M in deionized water to prepare a first metal solution with a total molar concentration of 1.8~2.4 mol / L. The molar concentration is denoted as c0, and M is La and / or Zr.

[0011] Lithium hydroxide was dissolved in deionized water to prepare a second metal solution with a molar concentration of 0.1~0.5 mol / L, and the molar concentration was denoted as c1.

[0012] Prepare a phosphoric acid solution with a molar concentration of 0.03~0.15 mol / L, and denot the molar concentration as c2;

[0013] Titanium oxysulfate was dissolved in dilute sulfuric acid to prepare a third metal solution with a molar concentration of 0.01~0.08 mol / L, denoted as c3.

[0014] Sodium aluminate and sodium hydroxide were dissolved in deionized water to prepare a fourth metal solution with a molar concentration of 0.05~0.15 mol / L, denoted as c4.

[0015] Prepare a sodium hydroxide or potassium hydroxide solution with a molar concentration of 8-10 mol / L as a precipitant solution;

[0016] Prepare an ammonia solution with a molar concentration of 2-4 mol / L as a complexing agent solution;

[0017] Prepare a dilute sulfuric acid solution with a molar concentration of 0.05~0.25 mol / L;

[0018] Step 2: Add the precipitant solution and the complexing agent solution to the sealed reaction vessel to prepare the base solution; control the pH value of the base solution to 12.30~12.70, maintain the temperature at 50~70℃, and the ammonia concentration in the base solution to 0.2~0.4mol / L using the precipitant solution.

[0019] Step 3: Keep the reactor stirring and introduce protective gas. Continuously add the first metal solution, the precipitant solution, and the complexing agent solution to the reactor at a flow rate of 300~800 mL / min to carry out the co-precipitation reaction. Stop adding liquid when the particles grow to the target particle size. Record the flow rate of the first metal solution as v1 and the reaction time as t1.

[0020] The pH was maintained at 12.00~12.40, the reaction temperature at 50~70℃, the rotation speed of the reactor at 500~700 r / min, the concentration of complexing agent in the slurry in the reactor at 0.2~0.4 mol / L, and the solid content in the reactor at 20%~25%.

[0021] Step 4: Continuously add the second metal solution and the phosphoric acid solution to the reaction vessel after stopping the liquid addition in Step 3 to continue the reaction. Record the flow rate of the second metal solution as v2 and the flow rate of the phosphoric acid solution as v3. Stop adding liquid when the reaction time reaches t2.

[0022] Step 5: Continue to add the third metal solution to the reaction vessel after stopping the liquid feeding in Step 4 to continue the reaction. Record the flow rate of the third metal solution as v4. Stop the liquid feeding when the reaction time reaches t3.

[0023] Step 6: Continuously add the fourth metal solution and the dilute sulfuric acid solution to the reaction vessel after stopping the liquid addition in Step 5 to continue the reaction. Record the flow rate of the fourth metal solution as v5. Stop adding liquid when the reaction time reaches t4.

[0024] Step 7: The slurry obtained from co-precipitation is centrifuged, washed, and dried to obtain a precursor for the cathode material of solid-state batteries, with the chemical formula aNi. x Co y Mn z M k (OH)2@bLi3PO4·cTiO(OH)2·dAl(OH)3.

[0025] In a further technical solution, in step one, the Ni salt is selected from one or more of nickel sulfate, nickel chloride, and nickel acetate. The Co salt is selected from one or more of cobalt sulfate, cobalt chloride, and cobalt acetate. The Mn salt is selected from one or more of manganese sulfate, manganese chloride, and manganese acetate. The La salt is selected from one or more of lanthanum sulfate, lanthanum chloride, and lanthanum acetate. The Zr salt is selected from one or more of zirconium oxysulfate and zirconium oxychloride.

[0026] In a further technical solution, in step one, the pH of the third metal liquid is 2.5~5.5, and the temperature is 40~60℃. Titanium oxysulfate is easily hydrolyzed in water to form an insoluble TiO(OH)2 precipitate. Adding an appropriate amount of dilute sulfuric acid can effectively prevent its hydrolysis, while maintaining the temperature at 40~60℃ is to increase its solubility in water.

[0027] A further technical solution involves a ratio in step four of (c1×v2) / 3(c2×v3) of 1.05~1.15, which represents the molar ratio. By controlling the amount of lithium hydroxide added, the amount of added PO4 is ensured. 3- Complete precipitation ensures that the LATP obtained in subsequent preparations is free of impurities.

[0028] A further technical solution involves maintaining the pH at 12.00–12.40, the reaction temperature at 5–25°C, the reactor rotation speed at 500–700 r / min, and the solid content in the reactor at 25%–30%. Since Li3PO4 has lower solubility in cold water, controlling the reaction temperature at 5–25°C is more conducive to uniformly coating the precursor surface with a layer of Li3PO4. Furthermore, controlling the solid content at 25%–30% facilitates the adhesion of Li3PO4 to the precursor surface and prevents it from detaching.

[0029] A further technical solution involves maintaining the pH at 11.00–11.40, the reaction temperature at 40–60°C, the reactor rotation speed at 500–700 r / min, and the solid content in the reactor at 25%–30%. Titanium oxysulfate readily precipitates in high-pH environments; therefore, pH control is crucial. Too low a pH results in slow precipitation and reduced efficiency, while too high a pH leads to rapid precipitation, potentially causing localized nucleation and preventing coating of the precursor surface. Maintaining the reaction temperature at 40–60°C enhances reactivity and improves coating efficiency.

[0030] In a further technical solution, in steps four, five, and six, (c2×v3×t2):(c3×v4×t3):(c4×v5×t4)=3:1.7:0.3, where the ratio is the molar ratio.

[0031] In a further technical solution, in step six, the pH during the reaction process is maintained at 11.75~12.15, the reaction temperature is maintained at 40~60℃, the rotation speed of the reactor is 500~700r / min, and the solid content in the reactor is 25%~30%.

[0032] A further technical solution involves steps three, four, five, and six, where c2×v3×t2 / (3c0×v1×t1+c2×v3×t2)=3c3×v4×t3 / (10c0×v1×t1+3c3×v4×t3)=17c4×v5×t4 / (10c0×v1×t1+17c4×v5×t4), and this ratio ranges from 0.0004 to 0.0008, representing the molar ratio. This design allows for the determination of Li... 1.3 Al 0.3 Ti 1.7 The coating amount of (PO4)3 is precisely controlled.

[0033] Furthermore, this invention also discloses a cathode material, obtained by high-temperature sintering of the aforementioned cathode material precursor for solid-state batteries with a lithium source; the sintering process includes:

[0034] Under oxygen-fluxed conditions, the material is heated to 450-550°C at a heating rate of 1-3°C / min and reacted for 4-6 hours. Then, it is heated to 700-900°C at a heating rate of 5-8°C / min and reacted for 20-30 hours. Finally, it is allowed to cool naturally to room temperature to obtain the positive electrode material for solid-state batteries, with the chemical formula aLiNi. x Co y Mn z M k O2@b / 3Li 1.3 Al 0.3 Ti 1.7 (PO4)3, tap density is 1.9~2.3 g / cm³. 3 Its specific surface area is 0.3~0.9 m². 2 / g, the peak intensity ratio of the (003) crystal plane to the (004) crystal plane satisfies 1.5 < I(003) / I(104) < 1.7.

[0035] In a further technical solution, the lithium source is selected from one or more of lithium hydroxide, lithium citrate, and lithium acetate.

[0036] In the above scheme, "heating to 450-550℃ at a heating rate of 1-3℃ / min and reacting for 4-6 hours" is to ensure that the hydroxide is slowly dehydrated, and to prevent the material volume from shrinking due to excessive dehydration, which would cause separation between the precursor and the coated material and form an interface problem.

[0037] "Then, the temperature is increased to 700-900℃ at a rate of 5-8℃ / min, and the reaction is carried out for 20-30 hours." Under the influence of high temperature, lithium ions fuse with the coating and precursor, and the cathode material LiNi is generated simultaneously. x Co y Mn z M k O2 and Li 1.3 Al 0.3 Ti 1.7 (PO4)3 further promotes the fusion between the cathode material and the coating material interface, alleviating interface problems.

[0038] The terms “include,” “including,” and “have” used in this article are all open-ended, meaning they include but are not limited to.

[0039] Unless otherwise specified, the terms used herein generally have their ordinary meaning in the context of the art, the subject matter, and the specific context. Certain terms used to describe this case will be discussed below or elsewhere in this specification to provide additional guidance to those skilled in the art in describing this case.

[0040] The working principle and advantages of this invention are as follows:

[0041] 1. This invention employs a stepwise co-precipitation method to sequentially and quantitatively coat the surface of a ternary precursor with Li3PO4, TiO(OH)2, and Al(OH)3; after calcination of this precursor with a lithium source, LiNi, a cathode material for solid-state batteries, is generated. x Co y Mn z M k O2, on the other hand, simultaneously forms a coating layer of Li on its surface. 1.3 Al 0.3 Ti 1.7 (PO4)3 (this coating layer has a fast lithium-ion transport channel and can be used as an interface modification layer for solid-state batteries) effectively alleviates the interfacial incompatibility problem between the electrode and the solid electrolyte. In addition, the stepwise quantitative coating method can solve the problem that Li3PO4, TiO(OH)2, and Al(OH)3 are prone to generating impurity phases due to their different precipitation coefficients, while ensuring the uniformity of the coating layer and improving the interface stability.

[0042] 2. The coating process of this invention strictly follows the sequence Li3PO4→TiO(OH)2→Al(OH)3. Li3PO4, as a fast ion conductor, provides a channel for lithium ions to diffuse into the precursor during subsequent calcination, establishing a dedicated path for lithium ion transport between the cathode material and the coating layer. The outermost coating of Al(OH)3 prevents aluminum from diffusing into the ternary precursor during calcination, avoiding aluminum loss and thus ensuring the final coating layer's Li3PO4 content. 1.3 Al 0.3 Ti 1.7 The purity of (PO4)3. Furthermore, Li3PO4 can be used as a lithium supplement in Li... 1.3 Al 0.3 Ti 1.7 During the formation of (PO4)3, excess lithium preferentially reacts with the ternary precursor, while simultaneously promoting the tight bonding between the cathode material and the coating layer, and strengthening the interfacial adhesion.

[0043] 3. This invention introduces element M (M is one or more of La and Zr) into the first metal solution to achieve atomic-level uniform doping of element M in the ternary precursor; element M is a high-valence element, which can effectively suppress the valence abrupt change of elements Ni and Co during charging and discharging, alleviate the collapse of the crystal structure of the cathode material, and significantly improve the cycle stability of solid-state batteries.

[0044] 4. This invention simultaneously completes the calcination of the positive electrode material LiNi. x Co y Mn z M k O2 preparation and Li coating 1.3 Al 0.3 Ti 1.7 The formation of (PO4)3 avoids the problem of poor interface contact caused by stepwise preparation, promotes the close bonding between the two and builds an efficient lithium-ion transport channel, and further alleviates the core problems of high electrode-electrolyte interface impedance and poor compatibility in solid-state batteries. Attached Figure Description

[0045] Appendix Figure 1 The image shows a SEM image of the precursor prepared in an embodiment of the present invention.

[0046] Appendix Figure 2 This is a SEM image of the precursor prepared in Comparative Example 1 of the present invention. Detailed Implementation

[0047] The present invention will be clearly described below with illustrations and detailed description. Any person skilled in the art who understands the embodiments of the present invention can make changes and modifications based on the technology taught in the present invention without departing from the spirit and scope of the present invention.

[0048] The terminology used herein is for the purpose of describing specific embodiments only and is not intended to limit the scope of this work. Singular forms such as “a,” “this,” “this,” “the,” and “the” as used herein also include plural forms. Example:

[0049] The preparation method of the cathode material precursor for solid-state batteries includes:

[0050] Step 1: Prepare a first metal solution of Ni (nickel sulfate), Co (cobalt sulfate), Mn (manganese sulfate), and Zr (zirconium oxysulfate), wherein the molar ratio of Ni, Co, Mn, and Zr is 96:2.8:1:0.2, the total molar concentration is 2.0 mol / L, and its molar concentration is denoted as c0;

[0051] Prepare a lithium hydroxide solution with a molar concentration of 0.21 mol / L as the second metal solution, and denot its molar concentration as c1;

[0052] Prepare a phosphoric acid solution with a molar concentration of 0.07 mol / L, and denot its molar concentration as c2;

[0053] A mixed solution of titanium oxysulfate and dilute sulfuric acid with a molar concentration of 0.05 mol / L was prepared as the third metal solution, with a molar concentration denoted as c3, a pH of 4.5, and a temperature of 50℃.

[0054] A mixed solution of sodium aluminate and sodium hydroxide with a molar concentration of 0.09 mol / L was prepared as the fourth metal solution, and its molar concentration was denoted as c4.

[0055] Prepare a sodium hydroxide solution with a molar concentration of 10 mol / L as a precipitant solution;

[0056] Prepare an ammonia solution with a molar concentration of 2.5 mol / L as the complexing agent solution;

[0057] Prepare a dilute sulfuric acid solution with a molar concentration of 0.15 mol / L;

[0058] Step 2: Add the precipitant and the complexing agent to the sealed reaction vessel to prepare a base solution. Control the pH of the base solution to 12.30~12.70 using the precipitant, maintain the temperature at 60℃, and the ammonia concentration in the base solution is 0.3mol / L.

[0059] Step 3: Keep the reactor stirred and introduce a protective gas. Continuously add the first metal solution, the precipitant, and the complexing agent to the reactor at a flow rate of 300-800 mL / min to carry out a co-precipitation reaction. Stop adding liquid when the particles grow to the target particle size. Record the flow rate of the first metal solution as 500 mL / min, denoted as v1, and the reaction time as 50 h, denoted as t1.

[0060] The pH during the reaction process was maintained at 12.00~12.40, the reaction temperature was maintained at 60℃, the rotation speed of the reactor was 650 r / min, the concentration of complexing agent in the slurry in the reactor was 0.3 mol / L, and the solid content in the reactor was 20%~25%.

[0061] Step 4: The second metal solution and the phosphoric acid solution are continuously added to the reaction vessel after the liquid addition was stopped in Step 3 to continue the reaction. The flow rate of the second metal solution is recorded as 650 mL / min, denoted as v2, and the flow rate of the phosphoric acid solution is recorded as 200 mL / min, denoted as v3. The liquid addition is stopped when the reaction time reaches 5 hours, and the reaction time is recorded as t2. The ratio of (c1×v2) / 3(c2×v3) is 1.08.

[0062] The pH during the reaction process is maintained at 12.00~12.40, the reaction temperature is maintained at 15℃, the rotation speed of the reactor is 650r / min, and the solid content in the reactor is 25%~30%.

[0063] Step 5: Continue to add the third metal solution to the reaction vessel after stopping the liquid feeding in Step 4 to continue the reaction. Record the flow rate of the third metal solution as 200 mL / min, and denote it as v4. Stop the liquid feeding when the reaction time reaches 3.97 h, and denote the reaction time as t3.

[0064] The pH during the reaction process is maintained at 11.00~11.40, the reaction temperature is maintained at 50℃, the rotation speed of the reactor is 650r / min, and the solid content in the reactor is 25%~30%.

[0065] Step 6: Continuously add the fourth metal solution and the dilute sulfuric acid solution to the reaction vessel after stopping the liquid addition in Step 5 to continue the reaction. Record the flow rate of the fourth metal solution as 50 mL / min, denoted as v5. Stop adding liquid when the reaction time reaches 1.56 h, and record the reaction time as t3.

[0066] The pH during the reaction process is maintained at 11.75~12.15, the reaction temperature is maintained at 50℃, the rotation speed of the reactor is 650r / min, and the solid content in the reactor is 25%~30%.

[0067] Step 7: The slurry obtained from co-precipitation in Step 6 is centrifuged, washed, and dried to obtain a precursor for the cathode material of solid-state batteries, with the chemical formula Ni. 0.96 Co 0.028 Mn 0.01 Zr 0.002(OH)2@0.18%Li3PO4·0.102%TiO(OH)2·0.018%Al(OH)3, D50 is 3.65um, tap density is 1.91g / cm³. 3 The particle size distribution is 0.72 mm, and the specific surface area is 5.16 m². 2 The relevant data for / g is shown in Table 1.

[0068] In steps four, five, and six, (c2×v3×t2):(c3×v4×t3):(c4×v5×t4)=3:1.7:0.3.

[0069] In steps three, four, five, and six, c2×v3×t2 / (3c0×v1×t1+c2×v3×t2)=3c3×v4×t3 / (10c0×v1×t1+3c3×v4×t3)=17c4×v5×t4 / (10c0×v1×t1+17c4×v5×t4)=0.0006.

[0070] The cathode material for solid-state batteries is obtained by mixing the cathode material precursor for solid-state batteries described in step seven with lithium hydroxide and sintering at high temperature. Specifically, under oxygen-flushing conditions, the mixture is heated to 500°C at a heating rate of 2°C / min and reacted for 5 hours, then heated to 750°C at a heating rate of 7°C / min and reacted for 25 hours. Finally, it is naturally cooled to room temperature to obtain the cathode material for solid-state batteries, with the chemical formula LiNi. 0.96 Co 0.028 Mn 0.01 Zr 0.002 O2@0.06%Li 1.3 Al 0.3 Ti 1.7 (PO4)3, tap density is 2.12 g / cm³. 3 Its specific surface area is 0.41 m². 2 / g, the peak intensity ratio of the (003) crystal plane to the (004) crystal plane is 1.6.

[0071] Comparative Example 1:

[0072] The difference from the examples is that the order of coating Li3PO4, TiO(OH)2, and Al(OH)3 is different. In this comparative example 1, lithium salt, phosphate, titanium salt, and aluminum salt solutions were added simultaneously for precipitation and coating. Otherwise, it is exactly the same as the examples. The precursor obtained after washing and drying is shown in Table 1.

[0073] Comparative Example 2:

[0074] The difference from the embodiment is that the molar ratio of Ni, Co, Mn, and Zr in the first metal solution in step one is different. In this comparative example 2, the molar ratio of Ni, Co, Mn, and Zr in the first metal solution is 96:2.5:1:0.5, and the rest is exactly the same as in the embodiment. The precursor obtained after washing and drying is shown in Table 1.

[0075] Comparative Example 3:

[0076] The difference from the embodiments is that the molar ratio of Ni, Co, Mn, and Zr in the first metal solution in step one is different. Zr element was not added to the first metal solution in Comparative Example 1, but everything else is exactly the same as in the embodiments. The precursor obtained after washing and drying is shown in Table 1.

[0077] Comparative Example 4:

[0078] The difference from the embodiment is that the order of steps four and five is different. In this comparative example 4, step five of the embodiment is performed first, and then step four is performed. The rest is exactly the same as the embodiment. The precursor obtained by washing and drying is shown in Table 1.

[0079] Comparative Example 5:

[0080] The difference from the embodiment is that the order of steps four and six is ​​different. In this comparative example 4, step six of the embodiment is performed first, and then step four is performed. The rest is exactly the same as the embodiment. The precursor obtained by washing and drying is shown in Table 1.

[0081] Table 1. Relevant test data of products obtained from each example.

[0082]

[0083] Comparing the data of each example in Table 1, it can be seen that in Comparative Example 1, the simultaneous addition of lithium salt, phosphate, titanium salt, and aluminum salt solutions for precipitation coating resulted in uneven precipitation, insufficient purity of the prepared coating layer, and exacerbated Li / Ni mixing in the cathode material (I (003) / I (004) The low Zr doping value failed to effectively improve the interface problem, resulting in high resistivity and low initial discharge capacity. As the Zr doping amount increased (Comparative Example 2), the initial discharge capacity of the corresponding cathode material decreased. Therefore, it is necessary to reasonably control the doping element content; too low a content (Comparative Example 3) will aggravate Li / Ni mixing (Ii). (003) / I (004)The low resistivity (too small value) leads to a decrease in the initial discharge capacity. In Comparative Example 4, the coating order of Li3PO4 and TiO(OH)2 was reversed, hindering lithium-ion diffusion (increasing resistivity) and resulting in a decrease in the initial discharge capacity. In Comparative Example 5, the coating order of Li3PO4 and Al(OH)3 was reversed, causing some aluminum elements to diffuse into the cathode material, resulting in an impure coating layer, unresolved interface problems, and correspondingly higher resistivity and decreased capacity.

[0084] Figure 1 , Figure 2 The images shown are electron microscope (EM) images of the products prepared in Example 1 and Comparative Example 1, respectively. Figure 1 As can be seen, the solid-state battery cathode material prepared in the examples has good sphericity and a smooth surface, allowing for close contact with the solid electrolyte and helping to reduce interfacial resistance. In contrast, the cathode material prepared in Comparative Example 1 has a small amount of fine powder on its surface, indicating that simultaneous precipitation of multiple elements easily leads to segregation and resulting in an impure interface. Furthermore, the presence of fine powder increases interfacial contact voids, affecting lithium-ion diffusion efficiency and further increasing resistivity.

[0085] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A cathode material precursor for solid-state batteries, characterized in that: The chemical formula is aNi x Co y Mn z M k (OH)2@bLi3PO4·cTiO(OH)2·dAl(OH)3, where M is one or more of La and Zr, 0.9≤x<1, 0<y<0.1, 0<z<0.1, 0≤k<0.003, and x+y+z+k=1, b / (3a+b)=3c / (10a+3c)=17d / (10a+17d)=0.0004~0.0008, b:c:d=3:1.7:0.3; D50 is 2.0~4.0µm, and tap density is 1.8~2.2g / cm³. 3 Particle size distribution: 0.5 < (D90 - D10) / D50 < 0.8; specific surface area: 2~8 m². 2 / g.

2. A method for preparing a cathode material precursor for solid-state batteries, characterized in that: A method for preparing the cathode material precursor for solid-state batteries as described in claim 1; the preparation method includes: Step 1: Dissolve the soluble salts of Ni, Co, Mn, and M in deionized water to prepare a first metal solution with a total molar concentration of 1.8~2.4 mol / L. The molar concentration is denoted as c0, and M is La and / or Zr. Lithium hydroxide was dissolved in deionized water to prepare a second metal solution with a molar concentration of 0.1~0.5 mol / L, and the molar concentration was denoted as c1. Prepare a phosphoric acid solution with a molar concentration of 0.03~0.15 mol / L, and denot the molar concentration as c2; Titanium oxysulfate was dissolved in dilute sulfuric acid to prepare a third metal solution with a molar concentration of 0.01~0.08 mol / L, denoted as c3. Sodium aluminate and sodium hydroxide were dissolved in deionized water to prepare a fourth metal solution with a molar concentration of 0.05~0.15 mol / L, denoted as c4. Prepare a sodium hydroxide or potassium hydroxide solution with a molar concentration of 8-10 mol / L as a precipitant solution; Prepare an ammonia solution with a molar concentration of 2-4 mol / L as a complexing agent solution; Prepare a dilute sulfuric acid solution with a molar concentration of 0.05~0.25 mol / L; Step 2: Add the precipitant solution and the complexing agent solution to the sealed reaction vessel to prepare the base solution; control the pH value of the base solution to 12.30~12.70, maintain the temperature at 50~70℃, and the ammonia concentration in the base solution to 0.2~0.4mol / L using the precipitant solution. Step 3: Keep the reactor stirring and introduce protective gas. Continuously add the first metal solution, the precipitant solution, and the complexing agent solution to the reactor at a flow rate of 300~800 mL / min to carry out the co-precipitation reaction. Stop adding liquid when the particles grow to the target particle size. Record the flow rate of the first metal solution as v1 and the reaction time as t1. The pH was maintained at 12.00~12.40, the reaction temperature at 50~70℃, the rotation speed of the reactor at 500~700 r / min, the concentration of complexing agent in the slurry in the reactor at 0.2~0.4 mol / L, and the solid content in the reactor at 20%~25%. Step 4: Continuously add the second metal solution and the phosphoric acid solution to the reaction vessel after stopping the liquid addition in Step 3 to continue the reaction. Record the flow rate of the second metal solution as v2 and the flow rate of the phosphoric acid solution as v3. Stop adding liquid when the reaction time reaches t2. Step 5: Continue to add the third metal solution to the reaction vessel after stopping the liquid feeding in Step 4 to continue the reaction. Record the flow rate of the third metal solution as v4. Stop the liquid feeding when the reaction time reaches t3. Step 6: Continuously add the fourth metal solution and the dilute sulfuric acid solution to the reaction vessel after stopping the liquid addition in Step 5 to continue the reaction. Record the flow rate of the fourth metal solution as v5. Stop adding liquid when the reaction time reaches t4. Step 7: The slurry obtained from co-precipitation is centrifuged, washed, and dried to obtain a precursor for the cathode material of solid-state batteries, with the chemical formula aNi. x Co y Mn z M k (OH)2@bLi3PO4·cTiO(OH)2·dAl(OH)3.

3. The method for preparing the cathode material precursor for solid-state batteries according to claim 2, characterized in that: In step one, the pH of the third metal liquid is 2.5~5.5 and the temperature is 40~60℃.

4. The method for preparing the cathode material precursor for solid-state batteries according to claim 3, characterized in that: In step four, the ratio of (c1×v2) / 3(c2×v3) is 1.05~1.

15.

5. The method for preparing a cathode material precursor for solid-state batteries according to claim 3, characterized in that: In step four, the pH of the reaction process is maintained at 12.00~12.40, the reaction temperature is maintained at 5~25℃, the rotation speed of the reactor is 500~700 r / min, and the solid content in the reactor is 25%~30%.

6. The method for preparing a cathode material precursor for solid-state batteries according to claim 3, characterized in that: In step five, the pH during the reaction process is maintained at 11.00~11.40, the reaction temperature is maintained at 40~60℃, the rotation speed of the reactor is 500~700 r / min, and the solid content in the reactor is 25%~30%.

7. The method for preparing a cathode material precursor for solid-state batteries according to claim 3, characterized in that: In steps four, five, and six, (c2×v3×t2):(c3×v4×t3):(c4×v5×t4)=3:1.7:0.

3.

8. The method for preparing a cathode material precursor for solid-state batteries according to claim 3, characterized in that: In step six, the pH during the reaction process is maintained at 11.75~12.15, the reaction temperature is maintained at 40~60℃, the rotation speed of the reactor is 500~700 r / min, and the solid content in the reactor is 25%~30%.

9. The method for preparing a cathode material precursor for solid-state batteries according to claim 3, characterized in that: In steps three, four, five, and six, c2×v3×t2 / (3c0×v1×t1+c2×v3×t2)=3c3×v4×t3 / (10c0×v1×t1+3c3×v4×t3)=17c4×v5×t4 / (10c0×v1×t1+17c4×v5×t4), and the value of this ratio ranges from 0.0004 to 0.0008.

10. A positive electrode material, characterized in that: The solid-state battery cathode material precursor as described in claim 1 is obtained by high-temperature sintering a mixture of lithium source and a lithium source; the sintering process includes: Under oxygen-fluxed conditions, the material is heated to 450-550°C at a heating rate of 1-3°C / min and reacted for 4-6 hours. Then, it is heated to 700-900°C at a heating rate of 5-8°C / min and reacted for 20-30 hours. Finally, it is allowed to cool naturally to room temperature to obtain the positive electrode material for solid-state batteries, with the chemical formula aLiNi. x Co y Mn z M k O2@b / 3Li 1.3 Al 0.3 Ti 1.7 (PO4)3, tap density is 1.9~2.3 g / cm³. 3 Its specific surface area is 0.3~0.9 m². 2 / g, the peak intensity ratio of the (003) crystal plane to the (004) crystal plane satisfies 1.5 < I(003) / I(104) < 1.7.

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