Blended ternary system battery cell of lithium battery and preparation method of blended ternary system battery cell

Abstract

The invention discloses a doped ternary system battery cell of a lithium battery and a preparation method of the doped ternary system battery cell, and belongs to the technical field of lithium batteries, and the preparation method comprises the following steps: preparation of a core-shell precursor: preparing a core-shell structure precursor composed of a core precursor and a shell precursor through a continuous coprecipitation method; lithiation and sintering: mixing the core-shell structure precursor with a lithium source and a fluorine source, and carrying out step-by-step gradient sintering in an oxygen atmosphere to obtain a sintered product; performing surface coating: performing dry mixing and heat treatment on the sintered product and an aluminum source and / or lithium aluminum oxide through a high-energy ball milling method to form a fast ion conductor coating layer on the surface of the sintered product to obtain a battery cell material; according to the invention, Ga < 3 + > and F <-> are introduced into the inner core, Zr < 4 + > and Al < 3 + > are introduced into the outer shell, so that a multi-element synergistically doped core-shell structure is formed, limitation of single element doping is avoided, and all-directional stability of a bulk phase structure is realized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium batteries, and particularly relates to a lithium battery mixed ternary system battery cell and a preparation method thereof. BACKGROUND

[0002] With the rapid development of new energy vehicles and energy storage power stations, higher requirements are put forward for the energy density, cycle life and safety performance of lithium ion batteries. The ternary material (LiNi x Co y Mn z O2, NCM) has become a research hotspot due to its high specific capacity, and the high-nickel ternary material (Ni content is greater than or equal to 0.8) has higher energy density, but has problems such as poor cycle stability and poor thermal stability.

[0003] In the prior art, single element doping or surface coating is usually used to improve the performance of the ternary material. For example, CN110323427A discloses an Al-doped ternary positive electrode material, which improves the structural stability of the material to a certain extent, but has limited inhibitory effect on the interface side reaction of the high-nickel material in the long cycle process. CN111883756A discloses a core-shell structure ternary positive electrode material, but the composition between the core and the shell changes suddenly, which is easy to cause interface cracking due to lattice mismatch in the charging and discharging process, and lacks effective interface protection.

[0004] In addition, the traditional wet coating process has problems such as uneven coating, introduction of impurity ions, and complex process flow. And a single doping element is often difficult to simultaneously consider the structural stability and interface stability.

[0005] Therefore, it is of great practical significance to develop a ternary positive electrode material and a preparation method thereof which can simultaneously solve the problems of bulk phase structural stability and interface stability, and have gradient composition distribution and effective interface protection. SUMMARY

[0006] In order to overcome some of the problems mentioned in the background above, the present application provides a herbicidal composition based on metamifop and cyhalofop-butyl to at least partially solve the above problems.

[0007] According to the technical scheme of the present application, a herbicidal composition based on metamifop and cyhalofop-butyl is provided, comprising the following steps: S1. Preparation of core-shell precursor: a core-shell structure precursor composed of an inner core precursor and an outer shell precursor is prepared by a continuous co-precipitation method; S2. Lithiation and sintering: the core-shell structure precursor is mixed with a lithium source and a fluorine source, and step-by-step gradient sintering is carried out in an oxygen atmosphere to obtain a sintered product; S3. Surface coating: The sintered product is dry-mixed with an aluminum source and / or lithium aluminum oxide by high-energy ball milling and heat-treated to form a fast ion conductor coating layer on the surface of the sintered product, thereby obtaining the cell material.

[0008] Preferably, in step S1: The chemical composition of the core precursor is Ni. x Co y M 1 z (OH)2, of which M 1 The metals are Al and Ga, with 0.85 ≤ x ≤ 0.89, 0.08 ≤ y ≤ 0.10, 0.02 ≤ z ≤ 0.06, and x + y + z = 1; the Ga doping amount is 0.4-0.6% of the total molar number of metals in the core. The chemical composition of the shell precursor is Ni. a Co b Mn c M 2 d (OH)2, of which M 2 The elements are Al and Zr, and 0.79≤a≤0.81, 0.14≤b≤0.16, 0.04≤c≤0.06, 0.015≤d≤0.02, a+b+c+d=1; the Zr doping amount is 0.2-0.4% of the total number of moles of metal in the shell.

[0009] Preferably, the reaction conditions for the continuous coprecipitation method in step S1 include: reaction temperature 50-60℃, pH value 10.8-11.2, and stirring speed 700-900 rpm; The synthesis time of the core precursor is 18-22 hours, and the epitaxial growth time of the shell precursor is 7-9 hours.

[0010] Preferably, in step S2: The lithium source is a mixture of LiOH·H2O and L in a molar ratio of 1:(0.8-1.2). i2 A mixture of CO3; The fluorine source is NH4F, with an addition amount of 0.8-1.2 wt% of the total mass of the core-shell structure precursor and the lithium source; Among them, the lithiation coefficient The value is 1.04-1.08, where M represents all doped metal elements.

[0011] Preferably, the stepwise gradient sintering in step S2 specifically refers to: Step 1: Increase the temperature to 480-520℃ at a heating rate of 1-3℃ / min, and hold at this temperature for 4-6 hours under an oxygen flow rate of 0.8-1.2 L / min; Step 2: Increase the temperature to 790-810℃ at a heating rate of 2-4℃ / min, and keep it at that temperature for 14-16 hours in an oxygen atmosphere.

[0012] Preferably, in step S3: The aluminum source is AlF3, and the lithium aluminum oxide is LiAlO2; The high-energy ball milling is carried out under an inert atmosphere, with a ball-to-material mass ratio of (8-12):1, a rotation speed of 300-400 rpm, and a milling time of 2-4 h. The heat treatment is carried out in an air or oxygen atmosphere at a temperature of 450-500℃ for 3-5 hours.

[0013] On the other hand, the present invention also provides a ternary lithium battery cell, the structure of which includes a core, a shell and a coating layer; The general chemical formula of the core is LiNi. x Co y M 1 z O2-δF, where M 1 For Al and Ga, δ is the number of moles of F doped; The chemical formula of the outer shell is LiNi. a Co b Mn c M 2 d O2, where M 2 For Al and Zr; The coating layer is a composite layer containing LiAlO2 and LiF.

[0014] Furthermore: in the kernel, 0.87≤x≤0.89, 0.08≤y≤0.10, 0.02≤z≤0.04, the molar percentage of Ga is 0.4-0.6%, and the molar doping amount of F is δ of 0.8-1.2%; In the outer shell, 0.79≤a≤0.81, 0.14≤b≤0.16, 0.04≤c≤0.06, 0.015≤d≤0.02, and the molar percentage of Zr is 0.2-0.4%; The thickness of the coating layer is 1-3 nm.

[0015] On the other hand, the present invention also provides a lithium-ion battery positive electrode sheet, including a current collector and a positive electrode material layer coated on the current collector, wherein the positive electrode material layer comprises the aforementioned cell material, conductive agent and binder.

[0016] On the other hand, the present invention also provides a lithium-ion battery comprising the positive electrode as described above.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Multi-element synergistic doping and gradient distribution: By introducing Ga into the core 3+ and F - Introducing Zr into the shell 4+ And Al 3+ This resulted in a core-shell structure with multi-element synergistic doping. Ga 3+ Due to its large ionic radius and strong bond energy, it can effectively pin the crystal lattice, suppressing phase transitions and microcrack propagation during charging and discharging; F - The introduction of Zr can improve the intrinsic stability of the material and suppress oxygen evolution; 4+ It can broaden the lithium-ion diffusion channels and improve rate performance; Al 3+ This further stabilizes the crystal structure. This gradient distribution avoids the limitations of single-element doping and achieves comprehensive stability of the bulk structure.

[0018] 2. Optimized core-shell interface design: The shell uses a composition with relatively low Ni content and high Mn content, which has better structural stability. As a buffer layer, it can reduce the direct contact between the highly active core and the electrolyte. At the same time, the compositional gradient change between the core and shell alleviates the internal stress caused by the sudden change in lattice constant, effectively suppressing the cracking problem of the core-shell interface during cycling.

[0019] 3. Innovative Fast Ion Conductor Coating Layer: A composite coating layer containing LiAlO2 and LiF was constructed on the material surface through a combination of high-energy ball milling dry coating and heat treatment. LiAlO2, as a fast ion conductor, significantly reduces the interfacial impedance of the cathode particles and effectively inhibits transition metal dissolution and electrolyte decomposition as a physical barrier. The presence of LiF further enhances interfacial stability, especially under high voltage. This composite coating layer, in synergy with bulk doping, achieves comprehensive protection from the bulk phase to the interface.

[0020] 4. Innovation in preparation process: The stepwise gradient sintering process is adopted. By precisely controlling the temperature program, the crystallinity of the core-shell structure is optimized and element interdiffusion is avoided, which solves the problems of easy damage to the core-shell structure and uneven doping in traditional one-step sintering. The high-energy ball milling dry coating method is adopted, which is simple, uniformly coated, and free of solvent pollution, and is suitable for industrial production.

[0021] 5. Excellent electrochemical performance: The ternary cathode material prepared by this invention maintains high capacity while exhibiting excellent cycle stability, superior rate performance and enhanced safety performance, which can meet the needs of electric vehicles and energy storage systems for high-performance lithium-ion batteries. Detailed Implementation

[0022] The technical solutions in the embodiments will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection.

[0023] The purpose of this invention is to provide a ternary hybrid lithium battery cell and its preparation method, so as to solve the problems of poor cycle stability and serious interfacial side reactions in existing high-nickel ternary materials.

[0024] This invention provides a method for preparing a core-shell gradient-doped ternary lithium-ion battery cathode material, comprising the following steps: S1. Preparation of core-shell precursors: Core-shell structure precursors consisting of a core precursor and an outer shell precursor were prepared by a continuous co-precipitation method. The chemical composition of the core precursor is Ni. x Co y M 1 z (OH)2, of which M 1 The metals are Al and Ga, with 0.85 ≤ x ≤ 0.89, 0.08 ≤ y ≤ 0.10, 0.02 ≤ z ≤ 0.06, and x + y + z = 1; the Ga doping amount is 0.4-0.6% of the total molar number of metals in the core. The chemical composition of the shell precursor is Ni. a Co b Mn c M 2 d (OH)2, of which M 2 The metals are Al and Zr, with 0.79≤a≤0.81, 0.14≤b≤0.16, 0.04≤c≤0.06, 0.015≤d≤0.02, and a+b+c+d=1; the Zr doping amount is 0.2-0.4% of the total molar number of metals in the outer shell. S2. Lithification and sintering: The core-shell structure precursor is mixed with a lithium source and a fluorine source, and then subjected to stepwise gradient sintering in an oxygen atmosphere to obtain the sintered product; The lithium source is a mixture of LiOH·H2O and Li2CO3 in a molar ratio of 1:(0.8-1.2); the fluorine source is NH4F, and its addition amount is 0.8-1.2 wt% of the total mass of the core-shell precursor and the lithium source; the lithiation coefficient... The value ranges from 1.04 to 1.08, where M represents all doped metal elements. The stepwise gradient sintering specifically refers to: Step 1: Increase the temperature to 480-520℃ at a heating rate of 1-3℃ / min, and hold at this temperature for 4-6 hours under an oxygen flow rate of 0.8-1.2 L / min; Step 2: Heat to 790-810℃ at a heating rate of 2-4℃ / min, and keep warm in an oxygen atmosphere for 14-16 hours; S3. Surface coating: The sintered product is dry-mixed with an aluminum source and / or lithium aluminum oxide and heat-treated using a high-energy ball milling method to form a fast ion conductor coating layer on the surface of the sintered product, thereby obtaining the cathode material; The high-energy ball milling is carried out under an inert atmosphere, with a ball-to-material mass ratio of (8-12):1, a rotation speed of 300-400 rpm, and a milling time of 2-4 h. The heat treatment is carried out in an air or oxygen atmosphere at a temperature of 450-500℃ for 3-5 hours.

[0025] In a second aspect, the present invention provides a ternary lithium battery cell prepared by the above preparation method, wherein the cell structure includes a core, a shell and a coating layer. The general chemical formula of the core is LiNi. x Co y M 1 z O2-δF, where M 1 For Al and Ga, δ is the number of moles of F doped; The chemical formula of the outer shell is LiNi. a Co b Mn c M 2 d O2, where M 2 For Al and Zr; The coating layer is a composite layer containing LiAlO2 and LiF.

[0026] Preferably, in the core, 0.87≤x≤0.89, 0.08≤y≤0.10, 0.02≤z≤0.04, the molar percentage of Ga is 0.4-0.6%, and the molar doping amount of F is 0.8-1.2%. In the outer shell, 0.79≤a≤0.81, 0.14≤b≤0.16, 0.04≤c≤0.06, 0.015≤d≤0.02, and the molar percentage of Zr is 0.2-0.4%; The thickness of the coating layer is 1-3 nm.

[0027] Thirdly, the present invention provides a lithium-ion battery positive electrode sheet, comprising a current collector and a positive electrode material layer coated on the current collector, wherein the positive electrode material layer comprises the aforementioned positive electrode material, a conductive agent, and a binder.

[0028] Fourthly, the present invention provides a lithium-ion battery comprising the above-mentioned positive electrode sheet.

[0029] Example 1: S1. Preparation of core-shell precursors Prepare a core salt solution (Ni:Co:Al molar ratio = 0.88:0.09:0.03, with 0.5 mol% Ga(NO3)3 added) with a total metal ion concentration of 2.0 mol / L, an outer shell salt solution (Ni:Co:Mn molar ratio = 0.80:0.15:0.05, with 0.3 mol% ZrO(NO3)2 and 1.5 mol% Al(NO3)3 added), a 4.0 mol / L NaOH solution, and a 0.5 mol / L NH4OH solution.

[0030] In a nitrogen-protected reactor at 55℃, deionized water and a complexing agent were added as a base solution, and the pH was controlled at 11.0±0.1. The stirring speed was 800 rpm. Simultaneously, the core salt solution and precipitant were pumped in parallel, and the reaction was carried out for 20 h to generate the core precursor. Keeping the reaction conditions unchanged, the outer shell salt solution was pumped in, and the reaction was continued for 8 h to allow the outer shell precursor to grow epitaxially on the core surface. After the reaction was completed, the mixture was aged for 5 h, filtered, washed with 70℃ hot water until the conductivity of the filtrate was <80 μS / cm, and dried under vacuum at 115℃ for 12 h to obtain the core-shell structured precursor powder.

[0031] S2. Lithification and Sintering The precursor powder was mixed with a mixed lithium salt of LiOH·H2O and Li2CO3 (molar ratio 1:1) at a lithiation factor of 1.06, and 1.0 wt% NH4F was added as a fluorine source. The mixture was mixed for 1.5 hours.

[0032] The mixture was subjected to stepwise gradient sintering in an oxygen atmosphere: the temperature was increased to 500℃ at 2℃ / min and held for 5 hours; then the temperature was increased to 800℃ at 3℃ / min and held for 15 hours. After natural cooling, the sintered product was obtained.

[0033] S3. Surface coating The sintered product was placed in a high-energy ball mill jar with 0.8 wt% nano-LiAlO2 powder and 0.5 wt% AlF3 powder at a ball-to-material ratio of 10:1 and ball-milled at 350 rpm for 3 hours under argon protection. Subsequently, it was heat-treated in air at 480℃ for 4 hours to obtain the final battery cell material.

[0034] Example 2: The difference from Example 1 is that the Ni:Co:Al molar ratio in the core precursor is 0.87:0.10:0.03, and the Ga doping amount is 0.4 mol.

[0035] The Ni:Co:Mn molar ratio in the outer shell precursor is 0.79:0.16:0.05, the Zr doping amount is 0.2 mol%, and the Al doping amount is 1.3 mol%.

[0036] Stepwise gradient sintering: First step: hold at 480℃ for 6 hours; Second step: hold at 790℃ for 16 hours. The amount of LiAlO2 added in the surface coating was 0.6 wt%, and the amount of AlF3 added was 0.3 wt%.

[0037] Example 3: The difference from Example 1 is that the Ni:Co:Al molar ratio in the core precursor is 0.89:0.08:0.03, and the Ga doping amount is 0.6 mol.

[0038] The Ni:Co:Mn molar ratio in the shell precursor is 0.81:0.14:0.05, the Zr doping amount is 0.4 mol%, and the Al doping amount is 1.7 mol%.

[0039] Stepwise gradient sintering: First step: hold at 520℃ for 4 hours; Second step: hold at 810℃ for 14 hours. The amount of LiAlO2 added in the surface coating was 1.0 wt%, and the amount of AlF3 added was 0.7 wt%.

[0040] Example 4: The difference from Example 1 is that deionized water and a complexing agent were added as a base solution in a nitrogen-protected reactor at 55°C, with the pH controlled at 11.0±0.1 and a stirring speed of 800 rpm. Simultaneously, a core salt solution and a precipitant were pumped in parallel, and the reaction was carried out for 18 hours to generate the core precursor. Keeping the reaction conditions unchanged, the outer shell salt solution was pumped in, and the reaction continued for 7 hours, allowing the outer shell precursor to epitaxially grow on the core surface. After the reaction, the mixture was aged for 5 hours, filtered, washed with 65°C hot water until the conductivity of the filtrate was <80 μS / cm, and then vacuum dried at 115°C for 12 hours to obtain the core-shell structured precursor powder.

[0041] The stepwise gradient sintering process is adjusted as follows: Step 1: Heat to 490℃ at 2.5℃ / min and hold for 4.5h; Step 2: Heat to 795℃ at 3.5℃ / min and hold for 14.5h.

[0042] The sintered product was placed in a high-energy ball mill jar with 0.8 wt% nano-LiAlO2 powder and 0.5 wt% AlF3 powder at a ball-to-material ratio of 10:1 and ball-milled at 350 rpm for 2.5 hours under argon protection. Subsequently, it was heat-treated in air at 480°C for 3.5 hours to obtain the final battery cell material.

[0043] Example 5: The difference from Example 1 is that the Ni:Co:Al molar ratio in the core precursor is 0.88:0.09:0.03, and the Ga doping amount is 0.55 mol.

[0044] The Ni:Co:Mn molar ratio in the shell precursor is 0.80:0.15:0.05, the Zr doping amount is 0.35 mol%, and the Al doping amount is 1.5 mol%.

[0045] The precursor powder was mixed with a mixed lithium salt of LiOH·H2O and Li2CO3 (molar ratio 1:1) at a lithiation factor of 1.06, and 1.1 wt% NH4F was added as a fluorine source. The mixture was mixed for 1.5 hours.

[0046] The amount of LiAlO2 added in the surface coating was 0.5 wt%, and the amount of AlF3 added was 0.8 wt%.

[0047] Example 6: The difference from Example 1 is that the Ni:Co:Al molar ratio in the core precursor is 0.89:0.08:0.03, and the Ga doping amount is 0.5 mol.

[0048] The Ni:Co:Mn molar ratio in the outer shell precursor is 0.78:0.14:0.08, the Zr doping amount is 0.3 mol%, and the Al doping amount is 1.5 mol%.

[0049] In a nitrogen-protected reactor at 55°C, deionized water and a complexing agent were added as a base solution, with the pH controlled at 11.0 ± 0.1 and the stirring speed at 800 rpm. Simultaneously, the core salt solution and precipitant were pumped in parallel, and the reaction was allowed to proceed for 20 hours to generate the core precursor. Maintaining the reaction conditions, the outer shell salt solution was switched on, and the reaction continued for another 9 hours.

[0050] Comparative Example 1: Using traditional high-nickel ternary material LiNi 0.88 Co 0.09 Al 0.03 O2 was prepared using a conventional solid-state method, without core-shell structure, Ga, F, or Zr doping, and without surface coating.

[0051] Comparative Example 2: A ternary material with a core-shell structure was used, but unlike the present invention, there was no gradient doping between the core and shell, and the surface was coated with a single Al2O3.

[0052] The cell materials obtained in Examples 1-6, Comparative Examples 1 and 2 were used to prepare positive electrode sheets, with graphite as the negative electrode, and assembled into soft-pack batteries with a rated capacity of 5Ah for testing. Test conditions included: cycle performance testing at 25℃ with a 1C rate within a voltage range of 3.0-4.3V; rate performance testing at different rates (0.2C, 0.5C, 1C, 2C, 3C); and the thermal runaway initiation temperature was measured using an adiabatic accelerated calorimeter. The results are shown in Table 1 below. Table 1

[0053] As shown in the table above, Examples 1-3, as the basic implementation schemes of this invention, exhibit excellent and stable comprehensive performance. All three examples show an initial discharge specific capacity exceeding 216 mAh / g, a capacity retention rate above 91% after 1000 cycles, a rate capability exceeding 92%, a thermal runaway initiation temperature above 210℃, and a slow increase in internal resistance after cycling (<20%). Therefore, it can be concluded that the core-shell gradient doping and interface passivation technology scheme described in this invention has excellent reproducibility and reliability, and can simultaneously achieve high capacity, long lifetime, high power, and safety.

[0054] Example 4, after appropriately shortening the key process times (such as precursor synthesis, sintering, and coating treatment times), showed only a slight decrease in overall performance compared to Examples 1-3, but still significantly outperformed the two comparative examples. This demonstrates that the preparation process window of the present invention has a certain degree of flexibility, possessing the potential to optimize production cycle time and reduce manufacturing costs while ensuring core performance (such as a capacity retention rate of up to 91% after 1000 cycles).

[0055] Example 5, by moderately increasing the ratio of bulk dopants Ga and Zr and adjusting the coating composition to increase the LiF content, demonstrated optimal cycling stability (93.8% retention) and the lowest cycling resistance growth (17.8%), while also achieving the highest thermal runaway initiation temperature (220°C). This proves that by finely controlling bulk doping and interfacial chemistry, the robustness of the material's crystal structure and its interfacial compatibility with the electrolyte can be significantly enhanced, thereby achieving extremely superior durability and safety.

[0056] Example 6, by combining a core with a higher nickel content (Ni=0.89) with a thicker, more stable outer shell with a higher Mn content, achieved the highest initial discharge specific capacity (219.8 mAh / g) and the best rate performance (94.0%). This fully demonstrates the high capacity potential of the high-nickel core and the effectiveness of the excellent lithium-ion transport channels constructed by the thick outer shell and Zr doping. Simultaneously, its cycle performance (92.0%) and thermal stability (218°C) remained high, indicating that the structural design successfully balanced the requirements of high capacity and high stability.

[0057] Comparative Example 1 (Traditional High-Nickel Material): Although it had the highest initial specific capacity (221.3 mAh / g), due to the lack of effective structural stability and interface protection, it performed the worst in terms of cycling, rate capability, and especially thermal safety performance. Its capacity decayed rapidly and its internal resistance increased sharply, fully exposing the inherent defects of traditional high-nickel materials.

[0058] Comparative Example 2 (Ordinary Core-Shell Coated Material): Although its performance is superior to Comparative Example 1, demonstrating the universality and effectiveness of the core-shell and coating concepts, its cycle retention rate, rate performance, thermal safety, and internal resistance stability are significantly lower than all embodiments of the present invention. This highlights the advanced nature and necessity of the synergistic design of multi-element gradient doping, core-shell composition optimization, and fast ion conductor composite coating employed in the present invention.

[0059] In summary, the ternary cathode materials prepared in all embodiments of this invention exhibit significantly superior overall electrochemical and safety performance compared to traditional single high-nickel materials and ordinary core-shell coated materials. This invention achieves precise control over material performance by adjusting the core-shell composition, doping elements and their proportions, coating layer composition, and process parameters. It enables targeted optimization of key indicators such as high capacity, long cycle life, high rate performance, and thermal safety to meet the stringent requirements of various applications, including electric vehicles and energy storage systems. This fully demonstrates the inventiveness, effectiveness, and industrial application potential of this invention.

[0060] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a ternary lithium battery cell, characterized in that, Includes the following steps: S1. Preparation of core-shell precursors: Core-shell structure precursors consisting of a core precursor and an outer shell precursor were prepared by a continuous co-precipitation method. S2. Lithification and sintering: The core-shell structure precursor is mixed with a lithium source and a fluorine source, and then subjected to stepwise gradient sintering in an oxygen atmosphere to obtain the sintered product; S3. Surface coating: The sintered product is dry-mixed with an aluminum source and / or lithium aluminum oxide by high-energy ball milling and heat-treated to form a fast ion conductor coating layer on the surface of the sintered product, thereby obtaining the cell material.

2. The method for preparing a ternary lithium battery cell according to claim 1, characterized in that, In step S1: The chemical composition of the core precursor is Ni. x Co y M 1 z (OH)2, of which M 1 The metals are Al and Ga, with 0.85≤x≤0.89, 0.08≤y≤0.10, 0.02≤z≤0.06, and x+y+z=1; the Ga doping amount is 0.4-0.6% of the total molar number of metals in the core. The chemical composition of the shell precursor is Ni. a Co b Mn c M 2 d (OH)2, of which M 2 The elements are Al and Zr, and 0.79≤a≤0.81, 0.14≤b≤0.16, 0.04≤c≤0.06, 0.015≤d≤0.02, a+b+c+d=1; the Zr doping amount is 0.2-0.4% of the total number of moles of metal in the shell.

3. The method for preparing a ternary lithium battery cell according to claim 1, characterized in that, The reaction conditions for the continuous coprecipitation method described in step S1 include: reaction temperature 50-60℃, pH value 10.8-11.2, and stirring speed 700-900 rpm; The synthesis time of the core precursor is 18-22 hours, and the epitaxial growth time of the shell precursor is 7-9 hours.

4. The method for preparing a ternary lithium battery cell according to claim 1, characterized in that, In step S2: The lithium source is a mixture of LiOH·H2O and L in a molar ratio of 1:(0.8-1.2). i2 A mixture of CO3; The fluorine source is NH4F, with an addition amount of 0.8-1.2 wt% of the total mass of the core-shell structure precursor and the lithium source; Among them, the lithiation coefficient The value is 1.04-1.08, where M represents all doped metal elements.

5. The method for preparing a ternary lithium battery cell according to claim 1, characterized in that, The stepwise gradient sintering described in step S2 specifically refers to: Step 1: Increase the temperature to 480-520℃ at a heating rate of 1-3℃ / min, and hold at this temperature for 4-6 hours under an oxygen flow rate of 0.8-1.2 L / min; Step 2: Increase the temperature to 790-810℃ at a heating rate of 2-4℃ / min, and keep it at that temperature for 14-16 hours in an oxygen atmosphere.

6. The method for preparing a ternary lithium battery cell according to claim 1, characterized in that, In step S3: The aluminum source is AlF3, and the lithium aluminum oxide is LiAlO2; The high-energy ball milling is carried out under an inert atmosphere, with a ball-to-material mass ratio of (8-12):1, a rotation speed of 300-400 rpm, and a milling time of 2-4 hours. The heat treatment is carried out in an air or oxygen atmosphere at a temperature of 450-500℃ for 3-5 hours.

7. A ternary lithium battery cell manufactured by the method according to any one of claims 1-6, characterized in that, The structure of a battery cell includes a core, a casing, and a cladding layer; The general chemical formula of the core is LiNi. x Co y M 1 z O2-δF, where M 1 For Al and Ga, δ is the number of moles of F doped; The chemical formula of the outer shell is LiNi. a Co b Mn c M 2 d O2, where M 2 For Al and Zr; The coating layer is a composite layer containing LiAlO2 and LiF.

8. The ternary lithium battery cell according to claim 7, characterized in that: In the core, 0.87≤x≤0.89, 0.08≤y≤0.10, 0.02≤z≤0.04, the molar percentage of Ga is 0.4-0.6%, and the molar doping amount of F is δ of 0.8-1.2%. In the outer shell, 0.79≤a≤0.81, 0.14≤b≤0.16, 0.04≤c≤0.06, 0.015≤d≤0.02, and the molar percentage of Zr is 0.2-0.4%; The thickness of the coating layer is 1-3 nm.

9. A positive electrode sheet for a lithium-ion battery, characterized in that, It includes a current collector and a positive electrode material layer coated on the current collector, the positive electrode material layer comprising the cell material and conductive agent and binder as described in claim 7 or 8.

10. A lithium-ion battery, characterized in that, It includes the positive electrode as described in claim 9.

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