Double-coated nickel ternary positive electrode material and preparation method thereof

Abstract

The application provides a double-coated nickel ternary positive electrode material and a preparation method thereof. The preparation raw material comprises a nickel ternary material; and a coating layer coated on the surface of the nickel ternary material; the coating layer comprises a fast ion conductor of boride and an alloy boride; the fast ion conductor of boride is selected from one or more of LiBO2, Li2B4O7, Li3BO3 and H3BO3; the content of the fast ion conductor of boride in the nickel ternary material is greater than 0 and less than or equal to 1%; and the content of the alloy boride in the nickel ternary material is greater than 0 and less than or equal to 0.5%. The fast ion conductor of boride exists in a glass state on the surface of the positive electrode material after heating, and bonds the primary particles together, so as to effectively improve the ion and electron conductance; in the cycle process, the two jointly act, have better capacity release, capacity retention rate, lower DCR growth rate, and have better gas production performance in the storage process.

Description

Technical Field

[0001] This invention belongs to the field of cathode material technology, and particularly relates to a double-coated nickel ternary cathode material and its preparation method. Background Technology

[0002] Currently, high-nickel ternary lithium-ion batteries are receiving increasing attention as green batteries with high energy density, no memory effect, high operating voltage platform, and excellent performance. However, the interface of high-nickel ternary lithium-ion batteries is easily corroded by the electrolyte, leading to failure, and the ternary surface is prone to passivation, resulting in reduced capacity and cycle life. Therefore, surface modification of high-nickel ternary materials is particularly important. However, during high-temperature storage or cycling, the Mn in the coating material undergoes a disproportionation reaction, causing dissolution and altering the positive electrode structure. Simultaneously, the dissolved Mn can penetrate the CEI and SEI films, damaging the stability of the negative electrode and leading to gas generation and capacity decay. For example, Chinese patent CN110085814 B provides a positive electrode material for lithium batteries, its preparation method, and its application; the positive electrode material for lithium batteries includes a lithium metal composite oxide with a layered structure and a boron coating layer formed on the surface of the lithium metal composite oxide, wherein the boron coating layer includes boron and / or borides, and the borides are lithium borate and / or boron oxide. The aforementioned patent utilizes the construction of lithium borate fast ion conductors on the ternary surface to effectively improve the material capacity. However, although the coating layer can improve the interface stability to some extent by bonding primary particles and isolating the positive electrode material and electrolyte from direct contact, the fast ion conductor does not have excellent corrosion resistance. With the increase of cycle number, the manganese in the positive electrode will undergo a disproportionation reaction, which will damage the interface between the positive and negative electrodes, leading to cycle decay and capacity reduction.

[0003] Therefore, it is urgent to explore a stable coating material to improve the cycle stability of batteries. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a double-coated nickel ternary cathode material and its preparation method, wherein the battery prepared by the ternary cathode material has excellent cycle stability.

[0005] This invention provides a double-coated nickel ternary cathode material, the raw materials for which include nickel ternary materials;

[0006] and the coating layer covering the surface of the nickel ternary material;

[0007] The coating layer includes boride fast ion conductors and alloy borides;

[0008] The fast ion conductor of the boride is selected from one or more of LiBO2, Li2B4O7, Li3BO3 and H3BO3;

[0009] The fast ion conductor of the boride accounts for a greater than 0 and less than or equal to 1% of the nickel ternary material;

[0010] The content of the alloy boride in the nickel ternary material is greater than 0 and less than or equal to 0.5%.

[0011] The raw materials for preparing the double-coated nickel ternary cathode material provided by this invention include a nickel ternary material, which preferably has the general formula shown in Formula I:

[0012] Li z Ni x Co y A 1-x-y O2 type I;

[0013] 0.6≤x≤1, 0≤y≤0.4, 0.9≤z≤1.1; x+y<1;

[0014] The A is selected from one or more of Mn, Al, Ta, Ti, Nb, Ge, Y, Nb, W, Zr, B, Ce, Ca, V, Si, Sr, Mg, and Mo;

[0015] In this invention, the value of x is preferably 0.7–0.9, more preferably 0.8–0.85; the value of y is preferably 0.05–0.3, more preferably 0.1–0.2; and the value of z is preferably 0.95–1.07, more preferably 0.98–1.03. In a specific embodiment, the nickel ternary material is Li. 1.03 Ni 0.83 Co 0.12 Mn 0.05 O2.

[0016] In this invention, the nickel ternary material has a nickel molar content of 60–94 mol%, preferably 70–90%, and more preferably 80–85%. In a specific embodiment, the nickel ternary material is preferably prepared by a continuous method. The nickel ternary material is spherical; the radius extending outward from the center is defined as the interior, and the remaining 1 / 3 of the radius is defined as the outer layer.

[0017] The raw materials for preparing the double-coated nickel ternary cathode material provided by the present invention include a coating layer covering the surface of the nickel ternary material; the coating layer includes a fast ion conductor of boride and an alloy boride.

[0018] In this invention, the fast ion conductor of the boride is selected from one or more of LiBO2, Li2B4O7, Li3BO3, and H3BO3. The fast ion conductor of the boride is coated on the surface of the nickel ternary cathode material in a glassy state.

[0019] In this invention, the alloy boride exhibits strong oxidation resistance and stable chemical properties. Its introduction stabilizes the interface of the nickel ternary material and improves its interface performance. The alloy boride is selected from one or more of ZrB2, MgB, CaB6, TiB2, NiB2, SiB6, AlB2, MnB2, NbB2, VB2, MoB, WB, TaB2, and CoB, more preferably from one or more of ZrB2, MgB, TiB2, and WB. The mass ratio of the alloy boride located on the surface of the nickel ternary material to the alloy boride penetrating into the interior of the nickel ternary material is greater than or equal to 2, preferably 2 to 13. The alloy boride is mainly located on the particle surface, playing a role in stabilizing the surface interface, and the alloy compound is relatively stable.

[0020] In this invention, the fast ion conductor of the boride accounts for a content greater than 0 and less than or equal to 1% of the nickel ternary material, preferably 0.2-0.8%, more preferably 0.3-0.7%; the alloy boride accounts for a content greater than 0 and less than or equal to 0.5% of the nickel ternary material, preferably 0.1-0.4%, more preferably 0.15-0.3%; the mass ratio of the fast ion conductor of the boride to the alloy boride is greater than 2. In a specific embodiment of this invention, the fast ion conductor of the boride accounts for 0.5% of the nickel ternary material; the alloy boride accounts for 0.2% of the nickel ternary material.

[0021] This invention provides a method for preparing the double-coated nickel ternary cathode material described above, comprising the following steps:

[0022] The fast ion conductors of nickel ternary material, alloy borides and borides are ball-milled to obtain abrasive material;

[0023] The ball milling material was sintered in an oxygen atmosphere to obtain a double-coated nickel ternary cathode material.

[0024] In this invention, the nickel ternary material is the material to be coated, specifically a nickel ternary material produced by a continuous method. The nickel ternary material has the general formula shown in Formula I of the above calculation scheme, which will not be repeated here. In a specific embodiment, the nickel ternary material is specifically Li... 1.03 Ni 0.83 Co 0.12 Mn 0.05 O2, with a nickel molar content of 83%.

[0025] The present invention uses zirconia ball milling beads for ball milling; the ball-to-material ratio is 1:3. Preferably, the present invention first mixes the nickel ternary cathode material and zirconia, then adds alloy borides and fast ion conductors of the borides before ball milling; the ball milling rate is 280–350 rpm, and the ball milling time is 110–130 min; in a specific embodiment, the ball milling rate is 300 rpm, and the ball milling time is 120 min.

[0026] After ball milling, the milling beads and the milled material are separated. The present invention sintersulates the milled material in an oxygen atmosphere to obtain a double-coated nickel ternary cathode material. Preferably, the milled material is sintered in a tube furnace; oxygen is introduced during sintering. Preferably, the temperature is increased from room temperature to the required sintering temperature at a heating rate of 1.8–2.3 °C / min, more preferably at a heating rate of 1.9–2.1 °C / min; the sintering temperature is 280–350 °C, and the sintering holding time is 9–12 h. In a specific embodiment, the heating rate is 2 °C / min, the sintering temperature is 320 °C or 300 °C, and the sintering holding time is 10 h.

[0027] The present invention preferably involves sieving the sintered material to remove large particles such as slag, thereby obtaining a double-coated high-nickel ternary cathode material; the D50 particle size of the double-coated nickel ternary cathode material is preferably 8-14 μm.

[0028] This invention provides a button cell battery, comprising a positive electrode, a negative electrode, and an electrolyte;

[0029] The positive electrode sheet includes a positive current collector and a positive electrode slurry coated on the surface of the positive current collector; the positive electrode slurry includes the double-coated nickel ternary positive electrode material described in the above technical solution or the double-coated nickel ternary positive electrode material prepared by the preparation method described in the above technical solution.

[0030] In this invention, the positive electrode slurry further includes acetylene black and polyvinylidene fluoride (PVDF); the mass ratio of the double-coated nickel ternary positive electrode material, acetylene black, and PVDF is 94:3:3; this invention uses pure lithium sheet as the negative electrode. The electrolyte is a 1 mol / L LiPF6 + DEC / EC mixed solution, wherein the volume ratio of DEC to EC is 1:1.

[0031] This invention coats the surface of a nickel ternary cathode material with a highly antioxidant and chemically stable alloy boride, forming an excellent passivation film that reduces corrosion of the particle surface by acidic substances in the electrolyte, mitigates degradation of the nickel ternary cathode material, inhibits LiF formation, and stabilizes the material surface, thus improving interface stability. Simultaneously, a boron-containing fast-ion conductor compound is introduced, which, upon heating, exists in a glassy state on the cathode material surface, binding primary particles together and effectively improving ionic and electronic conductivity. During cycling, it exhibits better capacity utilization, capacity retention, and a lower DCR growth rate. During storage, it demonstrates better gas generation performance. The combined effect of these two coatings effectively stabilizes the cathode material surface, and the method is easy to prepare, facilitating industrial production. Experimental results show that the battery prepared by the double-coated nickel ternary cathode material provided by this invention has an initial discharge capacity of 206.4–207.3 mAh / g; a gas production rate of 9.8–12.6% after 7 days at 70℃; a capacity retention rate of 93.2–94.2% after 300 cycles at 45℃; and a DCR growth rate of 23.9–25.6% after 300 cycles at 45℃. Attached Figure Description

[0032] Figure 1 This is an EDS data graph of the double-coated nickel cathode material prepared in Example 3 of the present invention;

[0033] Figure 2 The images are SEM images (50x magnification) of the double-coated nickel cathode materials prepared in Examples 1-6 and Comparative Examples 1-4 of this invention.

[0034] Figure 3 The figures show the gas generation diagrams of the double-coated nickel cathode materials prepared in Examples 1-6 and Comparative Examples 1-4 of this invention after 7 days / 70°C. Specifically, 1-1 to 1-6 are gas generation diagrams of Examples 1, 2, 3, 4, 5 and 6, respectively, and 1-7 to 1-10 are gas generation diagrams of Comparative Examples 1, 2, 3 and 4, respectively. Detailed Implementation

[0035] To further illustrate the present invention, the following detailed description, in conjunction with embodiments, of a double-coated nickel ternary cathode material and its preparation method provided by the present invention, should not be construed as limiting the scope of protection of the present invention.

[0036] Example 1

[0037] Including the nickel ternary cathode material Li to be coated 1.03 Ni 0.83 Co 0.12 Mn 0.05O2 (1000g; nickel molar content 83%), ZrB2, H3BO3; the raw materials contain 0.2% ZrB2 and 0.5% H3BO3 by mass. The high-nickel ternary cathode material is added to a planetary ball mill using zirconium oxide grinding beads, with a ball-to-material ratio controlled at 1:3. Then, ZrB2 and H3BO3 are added, and the mixture is ball-milled at 300 rpm for 2 hours. The grinding beads and grinding media are then separated. The material is placed in a tube furnace, oxygen is introduced, and the temperature is raised to 320℃ at 2℃ / min, and sintered for 10 hours. The sintered cathode material is then sieved to remove large particles such as slag, yielding the lithium-ion battery cathode material.

[0038] Example 2

[0039] The raw materials include the continuous-process nickel ternary cathode material Li to be coated. 1.03 Ni 0.83 Co 0.12 Mn 0.05 O2 (1000g; nickel molar content 83%), MgB, LiBO2; the raw materials contain 0.2% MgB and 0.5% LiBO2 by mass. The high-nickel ternary cathode material is added to a planetary ball mill using zirconia grinding beads at a ball-to-material ratio of 1:3. Then, MgB and LiBO2 are added, and the mixture is ball-milled at 300 rpm for 2 hours. The grinding beads and grinding media are then separated. The material is placed in a tube furnace, oxygen is introduced, and the temperature is raised to 320°C at 2°C / min, and sintered for 10 hours. The sintered cathode material is then sieved to remove large particles such as slag, yielding the lithium-ion battery cathode material.

[0040] Example 3

[0041] The raw materials include the continuous-process nickel ternary cathode material Li to be coated. 1.03 Ni 0.83 Co 0.12 Mn 0.05 O2 (1000g; nickel molar content 83%), TiB2, Li3BO3; the raw materials contain 0.2% TiB2 and 0.5% Li3BO3 by mass. The high-nickel ternary cathode material is added to a planetary ball mill using zirconia grinding beads at a ball-to-material ratio of 1:3. Then, TiB2 and Li3BO3 are added, and the mixture is ball-milled at 300 rpm for 2 hours. The grinding beads and grinding media are then separated. The material is placed in a tube furnace, oxygen is introduced, and the temperature is raised to 320°C at 2°C / min, and sintered for 10 hours. The sintered cathode material is then sieved to remove large particles such as slag, yielding the lithium-ion battery cathode material.

[0042] Figure 1 This is an EDS data image of the double-coated nickel cathode material prepared in Example 1 of this invention; from Figure 1EDS analysis showed that the Ti element in the alloy boride had a surface proportion of 0.16wt% to 0.25wt% (the proportion of Ti element in the double-coated cathode material) and an internal proportion of 0.02wt% to 0.08wt%, with the alloy boride having a surface and internal proportion of ≥2%.

[0043] Example 4

[0044] The raw materials include the continuous-process nickel ternary cathode material Li to be coated. 1.03 Ni 0.83 Co 0.12 Mn 0.05 O2 (1000g; nickel molar content 83%), WB, Li2B4O7; the raw materials contain 0.2% WB and 0.5% Li2B4O7 by mass. The high-nickel ternary cathode material is added to a planetary ball mill using zirconia grinding beads, with a ball-to-material ratio controlled at 1:3. Then, WB and Li2B4O7 are added, and the mixture is ball-milled at 300 rpm for 2 hours. The grinding beads and grinding media are then separated. The material is placed in a tube furnace, oxygen is introduced, and the temperature is raised to 320℃ at 2℃ / min, and sintered for 10 hours. The sintered cathode material is sieved to remove large particles such as slag, yielding the lithium-ion battery cathode material.

[0045] Example 5

[0046] The raw materials include the continuous-process nickel ternary cathode material Li to be coated. 1.03 Ni 0.83 Co 0.12 Mn 0.05 O2 (1000g; nickel molar content 83%), ZrB2, H3BO3; the raw materials contain 0.2% ZrB2 and 0.5% H3BO3 by mass. The high-nickel ternary cathode material is added to a planetary ball mill using zirconium oxide grinding beads, with a ball-to-material ratio controlled at 1:3. Then, ZrB2 and H3BO3 are added, and the mixture is ball-milled at 300 rpm for 2 hours. The grinding beads and grinding media are then separated. The material is placed in a tube furnace, oxygen is introduced, and the temperature is increased to 300℃ at 2℃ / min, and sintered for 10 hours. The sintered cathode material is sieved to remove large particles such as slag, yielding the lithium-ion battery cathode material.

[0047] Example 6

[0048] The raw materials include the continuous-process nickel ternary cathode material Li to be coated. 1.03 Ni 0.83 Co 0.12 Mn 0.05O2 (1000g; nickel molar content 83%), ZrB2, H3BO3; the raw materials contain 0.3% ZrB2 and 0.6% H3BO3 by mass. The high-nickel ternary cathode material is added to a planetary ball mill using zirconium oxide grinding beads, with a ball-to-material ratio controlled at 1:3. Then, ZrB2 and H3BO3 are added, and the mixture is ball-milled at 300 rpm for 2 hours. The grinding beads and grinding media are then separated. The material is placed in a tube furnace, oxygen is introduced, and the temperature is increased to 320℃ at 2℃ / min, and sintered for 10 hours. The sintered cathode material is then sieved to remove large particles such as slag, yielding the lithium-ion battery cathode material.

[0049] Comparative Example 1

[0050] The raw materials include the continuous-process nickel ternary cathode material Li to be coated. 1.03 Ni 0.83 Co 0.12 Mn 0.05 O2 (1000g; nickel molar content 83%). The material was placed in a tube furnace, oxygen was introduced, and the temperature was increased to 320℃ at 2℃ / min, and sintered for 10 hours. The sintered cathode material was sieved to remove large particles such as slag, thus obtaining the lithium-ion battery cathode material.

[0051] Comparative Example 2

[0052] The raw materials include the continuous-process nickel ternary cathode material Li to be coated. 1.03 Ni 0.83 Co 0.12 Mn 0.05 O2 (1000g; nickel molar content 83%), ZrB2; the ZrB2 content in the raw material is 0.2% by mass; the high-nickel ternary cathode material is added to a planetary ball mill using zirconium oxide grinding beads, with a ball-to-material ratio controlled at 1:3. Then, ZrB2 is added, and the mixture is ball-milled at 300 rpm for 2 hours, after which the grinding beads and grinding media are separated. The material is placed in a tube furnace, oxygen is introduced, and the temperature is raised to 320℃ at 2℃ / min, and sintered for 10 hours. The sintered cathode material is sieved to remove large particles such as slag, yielding the lithium-ion battery cathode material.

[0053] Comparative Example 3

[0054] The raw materials include the continuous-process nickel ternary cathode material Li to be coated. 1.03 Ni 0.83 Co 0.12 Mn 0.05O2 (1000g; nickel molar content 83%), H3BO3; the raw material contains 0.5% H3BO3 by mass. The high-nickel ternary cathode material is added to a planetary ball mill using zirconium oxide grinding beads, with a ball-to-material ratio controlled at 1:3. Then, H3BO3 is added, and the mixture is ball-milled at 300 rpm for 2 hours. The grinding beads and the ground material are then separated. The material is placed in a tube furnace, oxygen is introduced, and the temperature is raised to 320°C at 2°C / min, and sintered for 10 hours. The sintered cathode material is then sieved to remove large particles such as slag, yielding the lithium-ion battery cathode material.

[0055] Comparative Example 4

[0056] The raw materials include the continuous-process nickel ternary cathode material Li to be coated. 1.03 Ni 0.83 Co 0.12 Mn 0.05 O2 (1000g; nickel molar content 83%), Li2B4O7; the mass content of Li2B4O7 in the raw material is 0.5%; the high-nickel ternary cathode material is added to a planetary ball mill using zirconia grinding beads, with a ball-to-material ratio controlled at 1:3. Then, WB and Li2B4O7 are added, and the mixture is ball-milled at 300 rpm for 2 hours, after which the grinding beads and grinding media are separated. The material is placed in a tube furnace, oxygen is introduced, and the temperature is raised to 320℃ at 2℃ / min, and sintered for 10 hours. The sintered cathode material is sieved to remove large particles such as slag, yielding the lithium-ion battery cathode material.

[0057] This invention assembles the nickel cathode materials prepared in the examples and comparative examples into coin cells. The specific method is as follows: Nickel cathode material enriched at grain boundaries with additives, acetylene black, and polyvinylidene fluoride (PVDF) are weighed at a mass ratio of 94:3:3, mixed evenly, and NMP is added and stirred for 2 hours to form a viscous slurry. This slurry is then evenly coated onto aluminum foil, vacuum baked at 80°C, pressed into sheets, and cut into cathode sheets with a diameter of 14 mm. A 16 mm diameter pure lithium sheet is used as the anode sheet, a 1 mol / L LiPF6 + DEC / EC (DEC and EC volume ratio 1:1) mixed solution is used as the electrolyte, and a polyCelgard propylene microporous membrane is used as the separator. The coin cells are assembled in an argon-filled glove box.

[0058] This invention uses the aforementioned button cell to test its initial discharge capacity and initial efficiency.

[0059] A positive electrode slurry was prepared by mixing high-nickel positive electrode material, conductive carbon black SP, conductive graphite KS-6, and binder PVDF in a mass ratio of 94.5%:2%:1%:2.5% with NMP. The positive electrode slurry was then coated and rolled to form a positive electrode sheet, which was then assembled with a negative electrode (graphite), a separator (polyCelgard propylene microporous membrane), and an electrolyte (1 mol / L LiPF6 + DEC / EC (volume ratio 1:1)) to form a 503048 full cell with a capacity of approximately 800 mAh.

[0060] This invention uses the above-mentioned full cell to conduct tests on gas production at 70°C for 7 days, capacity retention rate after 300 cycles at 45°C, and DCR growth rate after 300 cycles at 45°C.

[0061] The test method for the capacity retention rate after 300 cycles at 45℃ is as follows: using the Xinwei test cabinet (CT3008-5V3A-A1), at 45℃, the cycle voltage is 4.25~3V, the constant voltage cutoff current is 20mA, and 300 cycles are performed.

[0062] The method for calculating the DCR growth rate after 300 cycles at 45°C is as follows: Using a full battery with a Xinwei CT3008-5V3A-A1, at 45°C, the cycle voltage is 4.25~3V, the constant voltage cutoff current is 20mA, and 300 cycles are performed. At 100% SOC in each cycle, the voltage V1 is recorded. The discharge current I is set according to 1C, and after discharging for 30 seconds, the voltage V2 is recorded. The DCR per cycle can be obtained by calculating (V1-V2) / I.

[0063] The test method for gas production performance at 70°C for 7 days is as follows: First, the battery is fully charged and its volume is measured. Then, the fully charged battery is stored at 70°C for 7 days, and its volume is measured again. The difference between the two measurements is calculated. The volume measurement device is an electronic solid density meter TW-120E.

[0064] Table 1 shows the test results of the first discharge capacity, first effect, 7-day 70°C thermal gas production, 300 cycles at 45°C capacity retention, and 300 cycles at 45°C DCR growth rate for the examples and comparative examples:

[0065] Table 1. Performance test results of the products from the examples and comparative examples.

[0066]

[0067] As can be seen from the above embodiments, the nickel cathode material provided by the present invention improves the interfacial performance of the cathode material by introducing alloy compounds of boron and fast ion conductor compounds of boron. Specifically, the alloy compounds of boron have strong oxidation resistance and stable chemical properties, resulting in the formation of an excellent passivation film on the material surface, effectively improving the surface stability of the ternary material and reducing the side reactions between the ternary material and the electrolyte. On the other hand, the introduction of boron-containing fast ion conductor compounds improves the surface conductivity, comprehensively improving the capacity of the cathode material and reducing the deterioration of cycling, DCR, and gas generation performance caused by the surface damage of ternary material particles during storage and cycling. Experimental results show that the coin cell prepared with the nickel ternary cathode material has a 0.2C capacity ≥195mAh / g; using the above testing method, the full cell prepared with the nickel ternary cathode material retains more than 90% of its capacity after 300 cycles at 45℃.

[0068] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A double-coated nickel ternary cathode material, wherein the raw materials for preparation include nickel ternary materials; and the coating layer covering the surface of the nickel ternary material; The coating layer includes boride fast ion conductors and alloy borides; The boride fast ion conductor is selected from one or more of LiBO2, Li2B4O7, Li3BO3 and H3BO3; the boride fast ion conductor is coated on the surface of the nickel ternary cathode material in a glassy state; The fast ion conductor of the boride accounts for more than or equal to 0.2% and less than or equal to 0.8% of the nickel ternary material; the alloy boride accounts for more than or equal to 0.1% and less than or equal to 0.4% of the nickel ternary material. The nickel ternary material has the general formula shown in Formula I: Li z Ni x Co y A 1-x-y O2 type I; 0.7≤x≤0.9, 0.05≤y≤0.3, 0.95≤z≤1.07; x+y<1; The A is selected from one or more of Mn, Al, Ta, Ti, Nb, Ge, Y, Nb, W, Zr, B, Ce, Ca, V, Si, Sr, Mg, and Mo.

2. The double-coated nickel ternary cathode material according to claim 1, characterized in that, The mass ratio of the alloy boride located on the surface of the nickel ternary material to the alloy boride that penetrates into the interior of the nickel ternary material is greater than or equal to 2.

3. The double-coated nickel ternary cathode material according to claim 1, characterized in that, The mass ratio of the fast ion conductor of the boride to the alloy boride is greater than 2.

4. The double-coated nickel ternary cathode material according to claim 1 or 2, characterized in that, The alloy boride is selected from one or more of ZrB2, MgB, CaB6, TiB2, NiB2, SiB6, AlB2, MnB2, NbB2, VB2, MoB, WB, TaB2, and CoB.

5. The double-coated nickel ternary cathode material according to claim 1, characterized in that, The nickel ternary material has a nickel molar content of 60-94%.

6. A method for preparing the double-coated nickel ternary cathode material according to any one of claims 1 to 5, comprising the following steps: The nickel ternary material, the alloy boride, and the fast ion conductor of the boride are ball-milled to obtain abrasive material; The ball milling material was sintered in an oxygen atmosphere to obtain the double-coated nickel ternary cathode material.

7. The preparation method according to claim 6, characterized in that, The temperature is increased from room temperature to the required sintering temperature at a heating rate of 1.8~2.3℃ / min. The sintering temperature is 280~350℃, and the sintering holding time is 9~12h.

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