Interface-stable multi-element positive electrode material, preparation method thereof and lithium ion battery

Abstract

The application relates to the field of lithium ion batteries and discloses an interface-stable multi-element positive electrode material, a preparation method thereof and a lithium ion battery. The multi-element positive electrode material comprises a matrix and a coating layer coated on the surface of the matrix; the matrix is a nickel-based multi-element positive electrode material; the coating layer has a composition shown in formula I: Li 3+θ‑j L j La 1‑k Q k (PO4)2 formula I; wherein L is selected from Na and / or K, Q is selected from at least one element in Sc, Y, In, Fe, Ce, Pr, Nd, Pm, Sm, Eu, Gd and Tb, 0<=theta<0.5, 0<j<1 and 0<=k<0.8. The coating layer in the multi-element positive electrode material is a good lithium ion conductor, is beneficial to the transmission of lithium ions, can reduce the transfer impedance of lithium ions at the positive electrode / electrolyte interface, improves the rate performance of the multi-element positive electrode material, and when the multi-element positive electrode material is used in a lithium ion battery, the electrochemical performance of the lithium ion battery is significantly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of lithium ion batteries, in particular to an interface-stable multi-element positive electrode material, a preparation method thereof and a lithium ion battery. BACKGROUND

[0002] High-nickel LiNi 1-x-y Co x Mn y O2 positive electrode material (referred to as high-nickel multi-element material) is considered to be the most promising next-generation lithium-ion power battery positive electrode material due to its high reversible capacity and low cost. However, the material still has problems such as poor interface stability and internal structure degradation of secondary particles. The main reason is that the high-nickel multi-element material is oxidized to +4 valence when it is highly delithiated, and Ni 4+ is unstable and prone to side reactions with electrolyte, leading to electrolyte consumption and gas production problems. Moreover, Ni 4+ is reduced to form NiO rock salt phase, and the layered structure on the surface of the multi-element material after multiple cycles is often replaced by the rock salt phase, resulting in loss of active material and increased impedance of the battery, which has a major impact on the cycle performance and safety performance of the battery.

[0003] Traditional coating modification methods can only solve the problem of single interface stability of the material, such as the conventional metal oxide coating acting as a physical barrier between the positive electrode material and the electrolyte to improve the cycle performance. However, since the metal oxide coating layer does not participate in the electrochemical reaction and has poor lithium ion conductivity, it often leads to a decrease in the rate performance of the coated positive electrode material. Therefore, fast ion conductor coating has attracted great attention. Fast ion conductor material coating can act as a physical barrier between the positive electrode material and the electrolyte and also transport lithium ions, which can improve the cycle life and rate performance of the positive electrode material at the same time. The LATP and LLTO fast ion conductors contain Ti elements that are easily reduced, and the LLZO fast ion conductor exhibits poor air stability. Therefore, it is necessary to improve the surface stability of the high-nickel multi-element material, maintain the lithium ion transport structure of the positive electrode-electrolyte interface, and reduce the interface side reactions between the positive electrode and the electrolyte to improve the specific capacity and stability of the material.

[0004] The related art discloses a preparation method of a low-melting-point glass phase coated positive electrode material, which utilizes the low melting point of the low-melting-point glass phase, the large thermal expansion coefficient, and the good fluidity of the coating substance in a molten state to form a relatively uniform covering effect on the surface of the positive electrode particles; the low-melting-point glass phase contains borate and phosphate (the phosphate system includes one or more of ZnO-B2O3-P2O5, B2O3-BaO-P2O5, ZnO-SnO-P2O5, Na2O-CuO-P2O5 and SnOP2O5), and reacts with residual lithium on the surface of the positive electrode material in a molten state to reduce the residual lithium on the surface of the positive electrode material; compared with a crystal phase, the structure of the glass phase has obvious isotropy, and there is no obvious grain boundary, which is more conducive to the migration and transportation of lithium ions; finally, the high-temperature gas production and cycle life are improved on the basis of ensuring the capacity and kinetics of the positive electrode material. However, the temperature for forming the glass phase of multiple oxides is inconsistent with the coating heat treatment temperature, that is, the optimal temperature for forming the glass phase is different from the coating heat treatment temperature, and the coating agent cannot fully play a role; P2O5 is a toxic and harmful substance, and has strong water absorption and dehydration, and is easily deliquescent in air, which is not suitable for coating; if the melting point is low and the thermal expansion coefficient is large, the coating agent will be bonded together in the actual production process, which is not conducive to the flow and is difficult to achieve uniform coating. SUMMARY

[0005] In view of the problems in the prior art, the present application provides an interface-stable multi-element positive electrode material, a preparation method thereof and a lithium ion battery. The multi-element positive electrode material comprises a substrate and a coating layer with a specific composition coated on the surface of the substrate. The coating layer is a good lithium ion conductor, which is conducive to the transportation of lithium ions, can reduce the transfer impedance of lithium ions at the positive electrode / electrolyte interface, and thus improves the rate performance of the multi-element positive electrode material. When the multi-element positive electrode material is used in a lithium ion battery, the electrochemical performance of the lithium ion battery is significantly improved.

[0006] To achieve the above-mentioned purpose, the first aspect of the present application provides an interface-stable multi-element positive electrode material, which comprises a substrate and a coating layer coated on the surface of the substrate; the substrate is a nickel-based multi-element positive electrode material.

[0007] The coating layer has a composition shown in Formula I:

[0008] Li 3+θ-j L j La 1-k Q k (PO4)2 Formula I;

[0009] wherein L is selected from Na and / or K, Q is selected from at least one element of Sc, Y, In, Fe, Ce, Pr, Nd, Pm, Sm, Eu, Gd and Tb, 0≤θ<0.5, 0<j<1, 0≤k<0.8.

[0010] The second aspect of the present application provides a preparation method of an interface-stable multi-element positive electrode material, comprising the following steps:

[0011] mixing the nickel-based multi-element positive electrode material with a coating layer, first sintering, crushing, and sieving to obtain the interface-stable multi-element positive electrode material;

[0012] The coating layer has a composition shown in Formula I:

[0013] Li 3+θ-j L j La 1-k Q k (PO4)2 Formula I;

[0014] wherein L is selected from Na and / or K, Q is selected from at least one element of Sc, Y, In, Fe, Ce, Pr, Nd, Pm, Sm, Eu, Gd, and Tb, 0≤θ<0.5, 0<j<1, and 0≤k<0.8.

[0015] The third aspect of the present application provides an interface-stable multi-element positive electrode material prepared by the above preparation method.

[0016] The fourth aspect of the present application provides a lithium ion battery comprising the above interface-stable multi-element positive electrode material.

[0017] Through the above technical solution, the interface-stable multi-element positive electrode material, the preparation method thereof, and the lithium ion battery provided by the present application have the following beneficial effects:

[0018] The interface-stable multi-element positive electrode material provided by the present application comprises a substrate and a coating layer with a specific composition coated on the surface of the substrate. The coating layer is a good lithium ion conductor, which is conducive to the transmission of lithium ions and can reduce the transfer impedance of lithium ions at the positive electrode / electrolyte interface, thereby improving the rate performance of the multi-element material.

[0019] Further, the coating layer of the multi-element positive electrode material provided by the present application has a stable crystal structure, which can inhibit the corrosion of the electrolyte on the multi-element material, relieve the interface structure failure of the multi-element positive electrode material / electrolyte, and improve the cycle life of the multi-element positive electrode material.

[0020] Further, the multi-element positive electrode material provided by the present application has a strong P-O chemical bond, which can inhibit the loss of oxygen on the surface layer of the multi-element material, especially reduce the oxygen loss caused by local overcharging, and is conducive to improving the safety of the multi-element material.

[0021] The preparation method of the multi-element positive electrode material provided by the present application is simple and feasible, has strong practicability and universality, and is suitable for large-scale production. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 XRD curve of the coating layer material C1 in Example 1;

[0023] Figure 2 First charge-discharge curves of the multi-element positive electrode materials in Comparative Example 1 and Example 1 in a liquid lithium battery;

[0024] Figure 3 Cycle retention rate curves of the multi-element positive electrode materials in Comparative Example 1 and Example 1 in a liquid lithium battery;

[0025] Figure 4 DSC curves of the multi-element positive electrode materials in Comparative Example 1 and Example 1;

[0026] Figure 5 Impedance diagrams of the multi-element positive electrode materials in Comparative Example 1 and Example 1 in a solid-state lithium battery before and after cycling. DETAILED DESCRIPTION

[0027] The endpoints of the ranges and any values disclosed herein are not limited to the precise values recited as the exact dimensions are not critical to the invention. Any numerical value, however, can include values up to and including the value of the lower limit, and values up to and including the value of the upper limit, of the range. The endpoints of the ranges and any values disclosed herein are not limited to the precise values recited as the exact dimensions are not critical to the invention. Any numerical value, however, can include values up to and including the value of the lower limit, and values up to and including the value of the upper limit, of the range. The ranges and / or numerical values included herein are approximations. As such, numerical values within the range are not excluded.

[0028] The first aspect of the present application provides an interfacially stable multi-element positive electrode material, characterized in that the multi-element positive electrode material comprises a substrate and a coating layer coated on the surface of the substrate; the substrate is a nickel-based multi-element positive electrode material;

[0029] The coating layer has a composition shown in Formula I:

[0030] Li 3+θ-j L j La 1-k Q k (PO4)2Formula I;

[0031] wherein L is selected from Na and / or K, Q is selected from at least one element of Sc, Y, In, Fe, Ce, Pr, Nd, Pm, Sm, Eu, Gd and Tb, 0≤θ<0.5, 0<j<1, 0≤k<0.8.

[0032] In the present application, the multi-element positive electrode material comprises a substrate and a coating layer with a specific composition coated on the surface of the substrate, which is a good lithium ion conductor, is conducive to the transmission of lithium ions, can reduce the transfer impedance of lithium ions at the positive electrode / electrolyte interface, and further improves the rate performance of the multi-element material.

[0033] Specifically, the specific element composition and ratio in the coating layer make the coating layer have a special crystal structure, wherein LaO8 in the coating layer is a polyhedron (eight oxygens form a dodecahedron around La), PO4 is a tetrahedron, both of which constitute a three-dimensional framework, L ions in the coating layer will be filled in the gap position with higher migration energy to stabilize the three-dimensional framework, and Li ions will be filled in the gap position with lower migration energy to form a three-dimensional channel. Therefore, the coating layer provided by the application not only has a stable crystal structure, but also is a good lithium ion conductor, which is very beneficial to the transmission of lithium ions. Therefore, the transfer impedance of lithium ions at the anode / electrolyte interface can be reduced, and the rate performance of the multi-element anode material is improved.

[0034] It is known that when phosphate is combined with different cations, its structure will be affected by the environment of the two, causing its performance to change, that is, the effect of P-O bond in different substances is not the same. In the present application, the inventors have found through a large number of creative experimental studies that when the coating layer has the composition defined in the present application, the phosphate will form a strong P-O chemical bond, which can inhibit the loss of oxygen on the surface of the multi-element anode material, especially the loss of oxygen caused by local overcharging, thereby improving the thermal stability and safety of the multi-element anode material under high pressure. When the molar ratio of phosphate to Li, L, La and Q ions meets the range of the present application, the lithium ion conductivity in the coating layer is high, which can reduce the transfer impedance of lithium ions at the anode / electrolyte interface, thereby improving the rate performance of the multi-element material.

[0035] Further, in the present application, when the value range of j meets the condition, the coating layer can form a stable Pca21 crystal structure, which has high ion conductivity and is stable to moisture and carbon dioxide in the air. Therefore, when the energy density of the lithium battery is improved by increasing the cutoff voltage, even if more lithium ions are removed from the lattice when the charging voltage is increased, based on the skeleton structure of the Pca21 crystal, the stability of the structure can be maintained, the corrosion of the electrolyte to the multi-element anode material can be better inhibited, the interface structure failure of the multi-element anode material / electrolyte can be relieved, and the cycle life of the multi-element anode material is improved.

[0036] In a preferred embodiment of the present application, in the formula I, L is Na, Q is at least one element selected from Y, In, Ce, Pr, Nd, Pm, Sm, Eu, Gd and Tb, 0 < θ ≤ 0.15, 0.24 < j < 0.66, 0 < k ≤ 0.5. When the values of j and k are within the above range, further limitation of the molar ratio of Li ion to L and the molar ratio of La ion to Q ion can be achieved, and when the molar ratio of Li ion to L and the molar ratio of La ion to Q ion are within the limited range, the crystal structure and ion conductivity of the coating layer are balanced, so that the comprehensive performance of the multi-element positive electrode material is improved.

[0037] In the present application, the nickel-based multi-element positive electrode material as the substrate is not particularly limited, and can be a conventional nickel-based multi-element positive electrode material in the art. Preferably, the substrate is a nickel-based multi-element positive electrode material having a composition shown in formula II:

[0038] Li a Ni 1-x-y Co x M' y M z O2formula II.

[0039] wherein M' is selected from Mn and / or Al; M is at least one element selected from Al, Ba, Zr, Ti, Nb, Ta, Ga, Y, W, Ca, Sr, Sc, Cr, Mo, Hf, Si, Sm, V, La, Ce, Mg and B; 0.9 ≤ a ≤ 1.3, 0.001 ≤ x ≤ 0.5, 0 ≤ y ≤ 0.5, 0 < z ≤ 0.1.

[0040] In the present application, when the nickel-based multi-element positive electrode material having the composition shown in formula II is used as the substrate material, the stability of the crystal structure of the positive electrode material can be synergistically increased, and when it is used in a lithium ion battery, the battery can have high energy density and long cycle life, and the performance-price ratio of the whole life cycle is significantly improved.

[0041] Further, in formula II, M' is Mn; M is at least one element selected from Al, Zr, Ti, Nb, Ta, Y, W, Sr, Cr, Mo, Hf, Si, Sm, La, Ce, Mg and B; 0.96 ≤ a ≤ 1.08, 0.05 ≤ x ≤ 0.2, 0.05 ≤ y ≤ 0.2, 0.001 < z ≤ 0.08.

[0042] According to the present application, the exothermic peak temperature and peak value of the interface-stable multi-element positive electrode material measured by DSC are H1 and P1, respectively; the exothermic peak temperature and peak value of the substrate measured by DSC are H2 and P2, respectively, wherein H1 > H2 and P1 < P2.

[0043] In the present application, when H1>H2, P1

[0044] Further, H1-H2≥5℃, P1≤0.8P2.

[0045] According to the present application, the content of the coating layer is 0.01wt%-3wt% based on the mass of the substrate.

[0046] In the present application, when the amount of the coating layer satisfies the above range, a stable coating layer can be formed on the surface of the multi-element positive electrode material, the corrosion of the electrolyte to the multi-element material is inhibited, and the interface structure failure of the multi-element material / electrolyte is relieved; the strong P-O chemical bond can inhibit the loss of surface oxygen, and improve the cycle life and safety of the multi-element material.

[0047] Further, the content of the coating layer is 0.1wt%-2wt% based on the mass of the substrate.

[0048] According to the present application, the thickness of the coating layer in the interface-stable multi-element positive electrode material is 2-20nm, preferably 5-10nm.

[0049] According to the present application, the median particle size D 50 of the substrate is 1-30μm.

[0050] In the present application, when the median particle size D 50 of the substrate satisfies the above range, it is easy to coat, and the multi-element positive electrode material obtained has high energy density and good stability; if the median particle size D 50 is less than 2μm, it is difficult to coat, and the multi-element positive electrode material obtained has poor interface stability and insufficient cycle stability; if the median particle size D 50 is greater than 30μm, the energy density of the multi-element positive electrode material obtained is insufficient.

[0051] Further, the median particle size D 50 of the substrate is preferably 2-20μm.

[0052] According to the present application, the characteristic peak intensity I (215) of the (215) crystal plane and the characteristic peak intensity I (014) of the (014) crystal plane of the coating layer measured by XRD satisfy the following relationship:

[0053] 0.3 (215) / I (014) <0.7.

[0054] And, according to the present invention, the characteristic peak area S of the (215) crystal plane of the coating layer as measured by XRD (215) The characteristic peak area S of the (014) crystal plane (014) The following relationship must be satisfied:

[0055] 0.003 < S (215) / S (014) <0.05.

[0056] In this invention, when the characteristic peak intensity and characteristic peak area of ​​the (215) and (014) crystal planes obtained by XRD of the coating layer satisfy the above relationship, the coating layer can form a stable Pca21 crystal structure. This crystal structure has high ionic conductivity and is stable against moisture and carbon dioxide in the air. Therefore, when the energy density of the lithium battery is increased by increasing the cutoff voltage, even if more lithium ions are extracted from the lattice due to the increased charging voltage, the framework structure based on the Pca21 crystal can maintain the stability of the structure, better suppress the corrosion of the multi-electrolyte by the electrolyte, alleviate the interface structure failure of the multi-electrolyte, and improve the cycle life of the multi-electrolyte. (215) / I (014) Less than 0.3 or S (215) / S (014) If I is less than 0.003, the stability of the skeletal structure is low. (215) / I (014) Greater than 0.7 or S (215) / S (014) If the value is greater than 0.05, the ionic conductivity is insufficient.

[0057] Furthermore, 0.32 < I (215) / I (014) <0.67; and, 0.005<S (215) / S (014) <0.03.

[0058] According to the present invention, the median particle size D of the coating layer 50 The surface area of ​​the coating layer is less than or equal to 200 nm, and / or the specific surface area of ​​the coating layer is greater than or equal to 10 m². 2 / g.

[0059] In this invention, the median particle size D of the coating layer is selected. 50 ≤200nm and / or specific surface area ≥10m² 2 When / g of material is used as a coating layer, it can make the coating layer and nickel-based multi-element cathode material matrix mix evenly, which is more conducive to the formation of a stable crystal structure on the surface of the multi-element material.

[0060] The median grain size D of the coating layer mentioned in this application 50D50 refers to D of the particles in the material used to form the coating layer 50 .

[0061] Further, the coating layer has a median particle size D 50 of 10-150 nm, and / or a specific surface area of 50-500 m 2 / g.

[0062] According to the present application, the coating layer has an ionic conductivity of greater than 0.1 mS / cm, preferably greater than 0.4 mS / cm.

[0063] The second aspect of the present application provides a preparation method of the interface-stable multi-element positive electrode material, comprising the following steps:

[0064] mixing the nickel-based multi-element positive electrode material with the coating layer, first sintering, crushing, removing iron, and sieving to obtain the interface-stable multi-element positive electrode material;

[0065] The coating layer has a composition shown in Formula I:

[0066] Li 3+θ-j L j La 1-k Q k (PO4)2 Formula I;

[0067] wherein L is selected from Na and / or K, Q is selected from at least one element of Sc, Y, In, Fe, Ce, Pr, Nd, Pm, Sm, Eu, Gd, and Tb, 0≤θ<0.5, 0<j<1, 0≤k<0.8.

[0068] In the present application, mixing and sintering the coating layer with a special composition with the nickel-based multi-element positive electrode material can prepare the interface-stable multi-element positive electrode material of the first aspect of the present application. The coating layer is a good lithium ion conductor, which is conducive to the transmission of lithium ions and can reduce the transfer impedance of lithium ions at the positive electrode / electrolyte interface, so that the prepared interface-stable multi-element positive electrode material has improved rate performance.

[0069] According to the present application, the substrate is a nickel-based multi-element positive electrode material having a composition shown in Formula II:

[0070] Li a Ni 1-x-y Co x M' y M z O2 Formula II;

[0071] Wherein, M' is selected from Mn and / or Al; M is selected from at least one element of Al, Ba, Zr, Ti, Nb, Ta, Ga, Y, W, Ca, Sr, Sc, Cr, Mo, Hf, Si, Sm, V, La, Ce, Mg and B; 0.9≤a≤1.3, 0.001≤x≤0.5, 0≤y≤0.5, 0<z≤0.1.

[0072] Further, in formula II, M' is Mn; M is selected from at least one element of Al, Zr, Ti, Nb, Ta, Y, W, Sr, Cr, Mo, Hf, Si, Sm, La, Ce, Mg and B; 0.96≤a≤1.08, 0.05≤x≤0.2, 0.05≤y≤0.2, 0.001<z≤0.08.

[0073] According to the application, the adding amount of the coating layer is 0.01wt%-3wt% based on the amount of the nickel-based multi-element positive electrode material.

[0074] In the application, when the adding amount of the coating layer meets the above range, a stable coating layer can be formed on the surface of the nickel-based multi-element positive electrode material, the corrosion of the electrolyte to the multi-element material can be inhibited, and the interface structure failure of the multi-element material / electrolyte can be relieved; the strong P-O chemical bond can inhibit the loss of surface oxygen, and improve the cycle life and safety of the multi-element material.

[0075] Further, the adding amount of the coating layer is 0.1wt%-2wt% based on the amount of the nickel-based multi-element positive electrode material.

[0076] According to the application, the conditions of the first sintering include: the sintering temperature is 250-800℃; and the sintering time is 4-48h.

[0077] In the application, when the conditions of the first sintering meet the above range, the coating effect of the coating layer can be fully played, and the multi-element positive electrode material after coating has excellent interface stability.

[0078] Further, the conditions of the first sintering include: the sintering temperature is 300-750℃; and the sintering time is 8-24h.

[0079] According to the application, the coating layer is obtained by high-temperature solid-phase treatment and ion exchange treatment in sequence.

[0080] In the application, the coating layer needs to be treated by high-temperature solid-phase method and then ion exchanged to obtain the coating layer with the specific composition and crystal structure according to the application. If the coating layer is directly prepared by the solid-phase method, the coating layer according to the application cannot be obtained.

[0081] According to the application, the coating layer is prepared according to the following steps:

[0082] (1) mixing L source, La source, optionally Q source and P source according to the molar ratio of n(L):n(La):n(Q):n(P)=3+θ:1-k:k:2 to obtain a mixture;

[0083] (2) performing second sintering, crushing and sieving on the mixture to obtain a coating layer precursor L 3+θ La 1-k Q k (PO4)2;

[0084] (3) mixing the coating layer precursor L 3+θ La 1-k Q k (PO4)2, lithium source and pure water, sand grinding, drying, iron removal and sieving to obtain the coating layer;

[0085] wherein 0≤θ<0.5, the amount of use of the coating layer precursor L 3+θ La 1-k Q k (PO4)2 and the lithium source makes n(Li):n(L)=3+θ-j:j.

[0086] In the present application, the coating layer with specific composition and crystal structure can be prepared by the above method, further, the amount of addition of L source in step (1) is excessive, and the excessive value is θ, for example, the mixture is mixed according to the molar ratio of n(L):n(La):n(Q):n(P)=3.09:1-k:k:2, θ=0.09, the excessive L source not only can improve the reaction kinetics, make up for the partial volatilization of L source in the high temperature sintering process, but also can improve the ionic conductivity of the prepared coating layer.

[0087] In the present application, in step (1), the mixing conditions include: mixing at a speed of 1000-2000 rpm for 1-3 h.

[0088] According to the present application, in step (2), the second sintering conditions include: sintering temperature of 600-1300℃, and sintering time of 9-36 h.

[0089] Further, in step (2), the second sintering conditions include: sintering temperature of 750-1300℃, and sintering time of 12-19 h.

[0090] In a preferred embodiment of the present application, the second sintering is two-stage sintering, specifically, the second sintering is performed according to the following steps: sintering the mixture at 600-900℃ for 1-5 h, and then sintering at 800-1300℃ for 8-24 h.

[0091] Further, the conditions of the second sintering include: sintering the mixture at 750-860℃ for 2-3h, and then sintering at 900-1200℃ for 10-16h.

[0092] In the present application, the method includes, after a period of sintering, crushing the product of the period of sintering, preferably to a D 100 30 microns or less, and then performing a second sintering.

[0093] In the present application, in step (3), the conditions of the sand milling include: sand milling at a rotation speed of 1500-2500rpm for 4-10h.

[0094] In the present application, in step (3), the conditions of the drying include: a drying temperature of 80-150℃, and a drying time of 7-24h.

[0095] In the present application, the amount of pure water is not particularly limited, as long as it can make the coating layer precursor L3La 1-k Q k The lithium source and the (PO4)2 can be in sufficient contact and uniformly dispersed.

[0096] In the present application, the preparation method of the nickel-based multi-element positive electrode material is not particularly limited, and can be prepared according to the conventional preparation method in the art. In one specific embodiment of the present application, the nickel-based multi-element positive electrode material is prepared according to the following steps:

[0097] S1, a mixed salt solution is prepared by mixing a cobalt salt, an M' salt, and a nickel salt according to a molar ratio of n(Ni):n(Co):n(M')=(1-x-y):x:y; a precipitating agent and a complexing agent are respectively prepared into a precipitating agent solution and a complexing agent solution;

[0098] S2, the mixed salt solution, the precipitating agent solution, and the complexing agent solution are added into a reaction kettle to perform a co-precipitation reaction in an inert atmosphere, to obtain a solid-liquid mixed slurry, which is filtered, washed, dried, iron-removed, and sieved to obtain a multi-element material precursor;

[0099] S3, the multi-element material precursor and a lithium source are mixed, thirdly sintered, crushed, iron-removed, and sieved to obtain a nickel-based multi-element positive electrode material;

[0100] The M source is added to step S2 and / or step S3.

[0101] In the present application, the types of the nickel salt, the cobalt salt, and the M' salt are not particularly limited, and can be the conventional types of nickel salt, cobalt salt, and M' salt in the art. For example, the nickel salt, the cobalt salt, and the M' salt are each independently selected from at least one of a sulfate, a nitrate, a chloride, an oxalate, an acetate, and a citrate.

[0102] Further, the nickel salt is selected from at least one of nickel sulfate, nickel nitrate, nickel chloride, nickel oxalate, nickel acetate and nickel citrate; the cobalt salt is selected from at least one of cobalt sulfate, cobalt nitrate, cobalt chloride, cobalt oxalate, cobalt acetate and cobalt citrate; and the M' salt is selected from at least one of a sulfate salt of M', a nitrate salt of M', a chloride salt of M', an oxalate salt of M', an acetate salt of M' and a citrate salt of M'.

[0103] In the present application, the M' salt is selected from Mn and / or Al.

[0104] In the present application, when the M source is added to step S2, the M source is added to step S2 in the form of a solution, and specifically, the M source is selected from soluble salts capable of providing at least one element from Al, Ba, Zr, Ti, Nb, Ta, Ga, Y, W, Ca, Sr, Sc, Cr, Mo, Hf, Si, Sm, V, La, Ce, Mg and B, such as at least one of a sulfate salt, a nitrate salt, a chloride salt, an oxalate salt, an acetate salt and a citrate salt.

[0105] In the present application, the kind of the precipitant and the complexing agent is not particularly limited, and a conventional kind of precipitant and complexing agent in the art can be used, for example, the precipitant is sodium hydroxide, and the complexing agent is ammonia.

[0106] In the present application, in step S1, the concentration of the mixed salt solution is 1-3 mol / L, the concentration of the precipitant solution is 1-15 mol / L, the concentration of the complexing agent solution is 1-15 mol / L, and the concentration of the M source solution is 0.1-2 mol / L.

[0107] The amount of the precipitant solution and the complexing agent solution is not particularly limited, and can be controlled according to the morphology and particle size of the obtained multi-element material precursor.

[0108] Further, the concentration of the mixed salt solution is 1.5-2.5 mol / L, the concentration of the precipitant solution is 2-10 mol / L, the concentration of the complexing agent solution is 5-10 mol / L, and the concentration of the M source solution is 0.2-1 mol / L.

[0109] In the present application, in step S2, the conditions of the co-precipitation reaction include that the pH value is 10-13, the reaction temperature is 40-80°C, and the reaction time is 5-50 h.

[0110] Further, the conditions of the co-precipitation reaction include that the pH value is 11-12, the reaction temperature is 50-70°C, and the reaction time is 8-32 h.

[0111] In the present application, in step S2, the drying condition comprises: the drying temperature is 100-150℃, and the drying time is 6-48h.

[0112] Further, the drying condition comprises: the drying temperature is 115-130℃, and the drying time is 12-36h.

[0113] In the present application, the median particle size D 50 of the nickel-based multi-element positive electrode material substrate is 1-30μm, preferably 2-20μm.

[0114] In the present application, the M source is selected from compounds of at least one element of Al, Ba, Zr, Ti, Nb, Ta, Ga, Y, W, Ca, Sr, Sc, Cr, Mo, Hf, Si, Sm, V, La, Ce, Mg and B.

[0115] Further, the compound of the M source is selected from at least one of oxides of the M source, hydroxides of the M source and carbonates of the M source.

[0116] In the present application, for step S2 and step S3, the solution of the M source or the respective amount of the M source added is not particularly limited, as long as the nickel-based multi-element positive electrode material prepared satisfies 0

[0117] According to the present application, in step S3, the lithium source is added in an amount of a molar ratio of 0.90≤n(Li) / [n(Ni)+n(Co)+n(M')]≤1.30.

[0118] In the present application, when the amount of the source satisfies the above range, a multi-element material with a good layered structure can be formed, and has a higher specific capacity.

[0119] Further, in step S3, the lithium source is added in an amount of a molar ratio of 0.96≤n(Li) / [n(Ni)+n(Co)+n(M')]≤1.08.

[0120] In the present application, the lithium source is selected from at least one of lithium carbonate, lithium hydroxide and lithium nitrate.

[0121] Preferably, the third sintering condition comprises: the sintering temperature is 650-1000℃, preferably 800-950℃; and the sintering time is 4-48h, preferably 8-24h.

[0122] In the present application, the specific operation of the filtering, washing, drying, mixing, grinding, crushing, screening, and iron removal is not particularly limited as long as the requirements are met. In the present application, the filtering can be achieved by suction filtration, pressure filtration, centrifugation, or the like; the drying can be achieved by hot air, infrared, microwave, or the like; the mixing can be achieved by using a high-speed mixer, a V-shaped mixer, a double-cone mixer, or a plowshare mixer; when vacuum mixing or electromagnetic field mixing is used, more uniform mixing can be achieved, thereby improving the uniformity of coating. The grinding can be achieved by using a stirring ball mill, a planetary ball mill, or a sand mill; the crushing can be achieved by using a roll crusher, a ball mill, an airflow mill, or a mechanical mill; the screening can be achieved by using an ultrasonic vibrating screen; and the iron removal can be achieved by using an electromagnetic iron remover.

[0123] The third aspect of the present application provides an interfacially stable multi-element material prepared by the above preparation method.

[0124] The fourth aspect of the present application provides a lithium ion battery comprising the above interfacially stable multi-element positive electrode material.

[0125] The present application will be described in detail below through examples. In the following examples,

[0126] The particle sizes of the nickel-based multi-element positive electrode material matrix, the coating layer, and the interfacially stable multi-element positive electrode material are measured by using a Mastersizer 2000 laser particle size instrument.

[0127] The cell parameters in the multi-element positive electrode material, the components of the nickel-based multi-element positive electrode material, and the components of the coating layer are measured by using a Rigaku X-ray diffractometer.

[0128] The thickness of the coating layer in the multi-element positive electrode material is measured by using a Hitachi HF5000 transmission electron microscope.

[0129] The thermal stability of the multi-element positive electrode material is measured by using a Mettler TGA-DSC3+.

[0130] The ionic conductivity σ of the coating layer is measured by assembling a blocking electrode for the composite solid-state electrolyte to measure the alternating current impedance, and is calculated by the formula σ=L / RS, where L is the thickness of the composite solid-state electrolyte, R is the impedance value, and S is the effective electrode area.

[0131] The specific surface area of the coating layer material is measured by using a Micromeritics 3020 specific surface area instrument.

[0132] The raw materials used in the examples and comparative examples are commercially available.

[0133] Preparation Example 1

[0134] (1) mixing L source, La source, optionally Q source and P source according to the molar ratio of n(L):n(La):n(Q):n(P) to obtain a mixture;

[0135] (2) performing second sintering, crushing and sieving on the mixture to obtain a coating layer precursor L 3+θ La 1-k Q k (PO4)2;

[0136] (3) mixing the coating layer precursor L 3+θ La 1-k Q k (PO4)2, lithium source and pure water, sand grinding, drying, iron removal and sieving to obtain a coating layer material C1.

[0137] The types and amounts of raw materials in the preparation process and the specific operation conditions are shown in Table 1. The median particle size D 50 , BET, crystal structure and ionic conductivity of the coating layer material C1 are tested, and the results are shown in Table 2. The coating XRD is shown in Figure 1 . It can be seen from Figure 1 that the coating layer material C1 has an orthorhombic Na3La(PO4)2 structure (PDF card number is 04-002-4644, orthorhombic system, space group is Pca21), and no obvious impurity peak appears, obtaining an orthorhombic structure which exists stably at room temperature, indicating that the partial exchange of lithium ions does not destroy the crystal structure of Na3La(PO4)2, but changes the concentration of lithium ions moving in the crystal lattice and the moving channel of ions.

[0138] Preparation Example 2-10

[0139] The coating layer is prepared according to the method of Preparation Example 1, except that the types and amounts of raw materials and the specific operation conditions are different from those of Preparation Example 1, and the specific conditions are shown in Table 1. The median particle size D 50 , BET, crystal structure and ionic conductivity of the coating layer materials C2-C10 are tested, and the results are shown in Table 2.

[0140] Table 1

[0141]

[0142] Table 1 (continued)

[0143]

[0144]

[0145] Table 2

[0146]

[0147] Example 1

[0148] Step one, prepare a mixed salt solution of nickel sulfate, cobalt sulfate and manganese sulfate with a molar ratio of n(Ni):n(Co):n(Mn) of 93:2:5 at 2 mol / L. Prepare a 0.1 mol / L aluminum sulfate solution, a 3 mol / L NaOH solution, and a 6 mol / L NH3·H2O complexing agent solution.

[0149] Step two, continuously add the mixed salt solution, the aluminum sulfate solution (M salt), the NaOH solution, and the NH3·H2O complexing agent solution into the stirred reactor in a parallel flow manner to carry out the reaction. Control the pH value in the reaction system to be 11.5, and control the temperature of the whole system at 60℃. When the median particle size D 50 of the multi-element material precursor slurry reaches 3.6 μm, stop the reaction. Wash, filter and dry the product to obtain an aluminum-doped multi-element material precursor, wherein the aluminum sulfate is added in an amount of n(Al) / [n(Ni)+n(Co)+n(Mn)] = 0.001.

[0150] Step three, uniformly mix the multi-element material precursor in step two, zirconium oxide (M source), and lithium hydroxide in a molar ratio of n(Li) / [n(Ni)+n(Co)+n(Mn)] = 1.03 and n(Zr) / [n(Ni)+n(Co)+n(Mn)] = 0.001, and then sinter the mixture at 830℃ for 10 hours. After crushing and sieving, a nickel-based multi-element positive electrode material matrix is obtained.

[0151] Step four, uniformly mix the nickel-based multi-element positive electrode material matrix and the coating layer material C1 in a mass ratio of 100:1, and then sinter the mixture at 510℃ for 10 hours. After crushing and sieving, a multi-element positive electrode material A1 is obtained, and the composition is shown in Table 3.

[0152] Example 2

[0153] Step one, step two, and step three are the same as in Example 1.

[0154] Step four, uniformly mix the nickel-based multi-element positive electrode material matrix and the coating layer material C2 in a mass ratio of 100:0.9, and then sinter the mixture at 510℃ for 10 hours. After crushing and sieving, a multi-element positive electrode material A2 is obtained, and the composition is shown in Table 3.

[0155] Example 3

[0156] Step one, step two, and step three are the same as in Example 1.

[0157] Step four, the nickel-based multi-element positive electrode material matrix and the coating material C3 are mixed uniformly according to a mass ratio of 100:0.6, and then the mixture is sintered at 510 DEG C for 10 hours, and after crushing and sieving, a multi-element positive electrode material A3 is obtained, and the composition is shown in Table 3.

[0158] Example 4

[0159] Steps one, two and three are the same as in Example 1.

[0160] Step four, the nickel-based multi-element positive electrode material matrix and the coating material C4 are mixed uniformly according to a mass ratio of 100:0.8, and then the mixture is sintered at 510 DEG C for 10 hours, and after crushing and sieving, a multi-element material A4 is obtained, and the composition is shown in Table 3.

[0161] Example 5

[0162] Steps one, two and three are the same as in Example 1.

[0163] Step four, the nickel-based multi-element positive electrode material matrix and the coating material C5 are mixed uniformly according to a mass ratio of 100:0.5, and then the mixture is sintered at 510 DEG C for 10 hours, and after crushing and sieving, a multi-element material A5 is obtained, and the composition is shown in Table 3.

[0164] Example 6

[0165] Steps one, two and three are the same as in Example 1.

[0166] Step four, the nickel-based multi-element positive electrode material matrix and the coating material C6 are mixed uniformly according to a mass ratio of 100:0.5, and then the mixture is sintered at 510 DEG C for 10 hours, and after crushing and sieving, a multi-element material A6 is obtained, and the composition is shown in Table 3.

[0167] Example 7

[0168] Steps one, two and three are the same as in Example 1.

[0169] Step four, the nickel-based multi-element positive electrode material matrix and the coating material C1 are mixed uniformly according to a mass ratio of 100:1.5, and then the mixture is sintered at 510 DEG C for 10 hours, and after crushing and sieving, a multi-element material A7 is obtained, and the composition is shown in Table 3.

[0170] Example 8

[0171] The difference from Example 1 is that:

[0172] Step one, a 2mol / L mixed salt solution is prepared by mixing nickel sulfate, cobalt sulfate and sodium aluminate according to a molar ratio of n(Ni):n(Co):n(Al) of 93:2:5. A 2mol / L NaOH solution and a 6mol / L NH3·H2O complexing agent solution are prepared.

[0173] Step two, aluminum sulfate (M source) was added in an amount of n(Al 2 ) / [n(Ni)+n(Co)+n(Al 1 )] = 0.001, wherein Al 1 represents Al element from sodium aluminate, and Al 2 represents Al element from aluminum sulfate (M source), to prepare the multi-element material precursor.

[0174] Step three, the multi-element material precursor in step two, zirconium oxide (M source), and lithium hydroxide were mixed uniformly in a molar ratio of n(Li) / [n(Ni)+n(Co)+n(Al 1 )] = 1.03, n(Zr) / [n(Ni)+n(Co)+n(Al 1 )] = 0.001, to prepare the nickel-based multi-element positive electrode material matrix.

[0175] Step four was the same as example 1. The interface-stable multi-element positive electrode material A8 was prepared.

[0176] Example 9

[0177] The difference from example 1 is that:

[0178] The mass ratio of the nickel-based multi-element positive electrode material matrix and the coating material C1 in step four was 100:5.

[0179] Step one, step two, and step three were the same as example 1. The interface-stable multi-element positive electrode material A9 was prepared.

[0180] Example 10

[0181] The difference from example 1 is that: the coating material C9 was used to replace the coating material C1 in step four.

[0182] Step one, step two, and step three were the same as example 1. The interface-stable multi-element positive electrode material A10 was prepared.

[0183] Example 11

[0184] The difference from example 1 is that: the molar ratio of nickel sulfate, cobalt sulfate, and manganese sulfate in step one was n(Ni):n(Co):n(Mn) = 7:1:3.

[0185] The remaining steps were the same as example 1. The interface-stable multi-element positive electrode material A11 was prepared.

[0186] Comparative example 1

[0187] Step one, prepare a mixed salt solution of nickel sulfate, cobalt sulfate and manganese sulfate with a molar ratio of n(Ni):n(Co):n(Mn) of 93:2:5 at 2 mol / L. Prepare a 2 mol / L NaOH solution and a 6 mol / L NH3·H2O complexing agent solution.

[0188] Step two, continuously add the mixed salt solution, NaOH solution and NH3·H2O complexing agent solution into the stirred reactor in a parallel flow manner for reaction. Control the pH value in the reaction system to be 11.2-11.8, and control the temperature of the whole system at 60°C. When the slurry D 50 stops at 3.6 μm. Wash, filter and dry the product to obtain a multi-element material precursor.

[0189] Step three, uniformly mix the multi-element material precursor in step two with lithium hydroxide at a molar ratio of n(Li) / [n(Ni)+n(Co)+n(Mn)] = 1.03, and then sinter the mixture at 830°C for 10 hours. After crushing and sieving, a multi-element material matrix is obtained, and the composition is shown in Table 3.

[0190] Comparative Example 2

[0191] Steps one, two and three are the same as in Example 1.

[0192] Step four, sinter the nickel-based multi-element positive electrode material matrix at 510°C for 10 hours, and then crush and sieve to obtain a multi-element material D2, and the composition is shown in Table 3.

[0193] Comparative Example 3

[0194] The difference from Example 1 is that in step four, the coating material C7 is used to replace the coating material C1. A multi-element positive electrode material D3 is prepared, and the composition is shown in Table 3.

[0195] Comparative Example 4

[0196] The difference from Example 1 is that in step four, the coating material C8 is used to replace the coating material C1. A multi-element positive electrode material D4 is prepared, and the composition is shown in Table 3.

[0197] Comparative Example 5

[0198] The difference from Example 1 is that in step four, the coating material C10 is used to replace the coating material C1.

[0199] Steps one, two and three are the same as in Example 1. An interface-stabilized multi-element positive electrode material D5 is prepared.

[0200] Table 3

[0201]

[0202] m 1 is the mass of the substrate, m 2 is the mass of the cladding layer.

[0203] DSC of the interface-stable multi-element positive electrode material and the nickel-based multi-element positive electrode material and the particle size of the interface-stable multi-element positive electrode material were tested, and the results are shown in Table 4.

[0204] Table 4

[0205] Particle size of the multi-element positive electrode material (pm) H1 (°C) [H2(°C)] [H1-H2 (°C)] [P1 (W / g)] [P2 (W / g)] D1 3.6 / 198 / / 45.7 D2 3.6 / 199 / / 43.5 D3 3.6 207 199 8 37.8 43.5 D4 3.6 206 199 7 39.1 43.5 D5 3.6 202 199 3 41.5 43.5 A1 3.6 215 199 16 6.9 43.5 A2 3.6 212 199 13 13.2 43.5 A3 3.6 218 199 19 5.8 43.5 A4 3.6 216 199 17 6.2 43.5 A5 3.6 214 199 15 7.0 43.5 A6 3.6 213 199 14 5.6 43.5 A7 3.6 212 199 13 15.3 43.5 A8 3.6 214 202 12 6.4 50.7 A9 3.6 208 199 9 29.8 43.5 A10 3.6 208 199 9 10.5 43.5 A11 3.6 257 221 36 10.1 38.7

[0206] Test Example 1

[0207] The positive electrode materials prepared in Examples 1-11 and Comparative Examples 1-5 were used to assemble liquid 2032 button cells. Specifically, the positive electrode material, carbon nanotubes, Super P, and polyvinylidene fluoride and LiTFSI were dispersed in an appropriate amount of NMP at a mass ratio of 85:1:4:7:3, coated on an aluminum foil and dried, and then cut into positive electrode sheets with a diameter of 11 mm. The positive electrode sheets were vacuum dried at 120°C for 12 h and then stored in a vacuum-sealed state. The negative electrode was a lithium metal with a diameter of 14 mm. The separator was a Celgard porous membrane with a diameter of 19 mm. The electrolyte was prepared using LiPF6 as the solute and equal volumes of ethylene carbonate, dimethyl carbonate, and diethyl carbonate as the solvent, and the concentration of LiPF6 was 1 mol / L.

[0208] The positive electrode, the separator, the negative electrode, and the electrolyte were assembled into a soft package battery in an argon-filled glove box with water content and oxygen content less than 5 ppm. The electrochemical performance of the liquid 2032 button cell was tested, and the charge and discharge voltage for 0.1C and 2C capacity testing was 2.8V-4.3V, the cycle testing charge and discharge voltage was 2.8V-4.4V, the rate was 1C, and the test temperature was 25°C. The test results are shown in Table 5.

[0209] The thermal stability of the positive electrode material was evaluated by DSC (differential scanning calorimetry) testing of the exothermic peak temperature of the delithiated positive electrode sheet. The charge current of the delithiated positive electrode sheet was 0.2C, the cutoff voltage was 4.3V, and the cutoff current was 0.01C.

[0210] Test Example 2

[0211] The difference between Test Example 1 and Test Example 2 is that the Celgard porous membrane (PP / PE / PP three-layer membrane) with a diameter of 19 mm was replaced by a polyethylene oxide (PEO) solid-state electrolyte membrane with a diameter of 19 mm, and no electrolyte was used, resulting in a liquid 2032 button solid-state battery.

[0212] The preparation steps of the PEO solid-state electrolyte film are as follows: polyethylene oxide (PEO) and lithium bis (trifluoromethanesulfonyl) imide (LiTFSI) are mixed in a mass ratio of 3:1, then hot-pressed to form a thin film with a thickness of 40 μm, and then vacuum dried at 60°C for 10 hours and stored in a vacuum sealed container. The charge and discharge voltage for capacity and cycle test is 2.8V-4.3V, and the cycle rate is 0.2C; the impedance of the solid-state battery is tested by electrochemical impedance spectroscopy under the conditions of 10mV perturbation voltage and 1MHz-0.01Hz, and the test temperature is 60°C. The test results are shown in Table 5.

[0213] Table 5

[0214]

[0215]

[0216] As can be seen from Table 2, with more lithium ion exchange, C4 has higher lithium ion conductivity than C3, and C4 has lower I (215) / I (014) , indicating that the C4 skeleton structure with more exchanged lithium has lower stability. Combined with the discharge specific capacity (0.1C capacity), rate (2C capacity) and first coulombic efficiency (first efficiency) of A4 in Table 5 being higher than A3, it indicates that the lithium ions of A4 can be quickly deintercalated at the multi-element material electrolyte interface; and the cycle retention rate of A3 is higher than that of A4, indicating that the NiO rock salt phase formed on the surface of A3 is less, i.e. A3 coated with relatively stable C3 can better inhibit the formation of rock salt phase on the surface of multi-element material in the cycle, maintain the positive electrode electrolyte interface structure, inhibit the impedance increase Figure 5 ) in the cycle process, and improve the cycle life. The difference between C3 and C4 is the different lithium content, as can be seen from Table 2, the different lithium content will lead to different crystal structure stability and ion conductivity, further, compared C3 with C1, the addition of Q will further improve the ion conductivity, and then improve the capacity and rate of the positive electrode.

[0217] As Figure 2 and shown in Table 5, the discharge capacity of A1 at 0.1C and 2C rate is higher than that of D1, indicating that the coating layer has good lithium ion transmission characteristics, which is beneficial to the deintercalation of lithium ions in the charging and discharging process, can reduce the transfer impedance of lithium ions at the positive electrode / electrolyte interface Figure 5 , and then improve the cycle retention rate of the lithium ion battery containing the multi-element positive electrode material Figure 3 ; and the exothermic peak of A1 and A4 is higher than that of D1 Figure 4 , which means that the strong P-O chemical bond on the surface of the coated multi-element positive electrode material can inhibit the loss of oxygen on the surface, especially reduce the oxygen loss caused by local overcharging, and significantly improve the thermal stability of the multi-element positive electrode material.

[0218] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Various simple modifications can be made to the technical solutions of the present application within the technical concept of the present application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the present application and fall within the protection scope of the present application.

Claims

1. An interface-stabilized multinary positive electrode material, characterized by, The multi-element positive electrode material comprises a substrate and a coating layer coated on the surface of the substrate; the substrate is a nickel-based multi-element positive electrode material; The coating layer has a composition shown in Formula I: Li 3+θ-j L j La 1-k Q k (PO4)2formula I; Wherein, L is selected from Na and / or K, Q is selected from at least one element selected from Sc, Y, In, Fe, Ce, Pr, Nd, Pm, Sm, Eu, Gd, and Tb, 0 ≤ θ < 0.5, 0 < j <1, 0≤ k <0.

8.

2. The multinary cathode material of claim 1, wherein, In formula I, L is Na, Q is at least one element selected from Y, In, Ce, Pr, Nd, Pm, Sm, Eu, Gd, and Tb, 0 < θ ≤ 0.15, 0.24 < φ ≤ 0.66, 0 < ψ ≤ 0.5 j < 0.66, 0 < ψ ≤ 0.5 k ≤ 0.5; And / or, the substrate is a nickel-based multi-element positive electrode material having a composition shown in Formula II: Li a Ni 1-x-y Co x M' y M z O2formula II; wherein M' is selected from Mn and / or Al; M is selected from at least one element among Al, Ba, Zr, Ti, Nb, Ta, Ga, Y, W, Ca, Sr, Sc, Cr, Mo, Hf, Si, Sm, V, La, Ce, Mg and B; 0.9 a ≤ 1.3, 0.001 ≤ x ≤ 0.5, 0 ≤ y ≤ 0.5, 0 < x < 0.5 z ≤ 0.

1.

3. The multinary cathode material of claim 2, wherein, In Formula II, M' is Mn; M is selected from at least one element among Al, Zr, Ti, Nb, Ta, Y, W, Sr, Cr, Mo, Hf, Si, Sm, La, Ce, Mg and B; 0.96≤ a ≤1.08，0.05≤ x ≤0.2，0.05≤ y ≤0.2，0.001＜ z ≤0.08。 4. The multinary cathode material of claim 1 or 2, wherein, The interface-stabilized multi-element positive electrode material has an exothermic peak temperature and a peak value of H1 and P1 respectively measured by DSC; the substrate has an exothermic peak temperature and a peak value of H2 and P2 respectively measured by DSC, wherein H1 > H2 and P1 < P2; And / or, the content of the coating layer is 0.01wt%-3wt% based on the mass of the substrate; And / or, the thickness of the coating layer in the multi-element positive electrode material is 2-20nm; and / or the median particle size D50 of the base body is 1-30 pm. 50 1-30 pm.

5. The multinary cathode material of claim 4, wherein, The interface-stabilized multi-element positive electrode material has an exothermic peak temperature and a peak value of H1 and P1 respectively measured by DSC; the substrate has an exothermic peak temperature and a peak value of H2 and P2 respectively measured by DSC, wherein H1-H2 is ≥5℃ and P1≤0.8P2; And / or, the content of the coating layer is 0.1wt%-2wt% based on the mass of the substrate; And / or, the thickness of the coating layer in the multi-element positive electrode material is 5-10nm; and / or the median particle size D50 of the base body is 2-20 pm. 50 2-20 pm.

6. The multinary cathode material of claim 1 or 2, wherein, The characteristic peak intensity I of the (215) crystal face measured by XRD of the cladding layer (215) and the characteristic peak intensity I of the (014) crystal face (014) satisfies the following relationship: 0.3 < I (215) / I (014) <0.7; and, the characteristic peak area S of the (215) crystal face measured by XRD of the cladding layer (215) and the characteristic peak area S of the (014) crystal face (014) satisfies the following relationship: 0.003 < S (215) / S (014) <0.05; and / or, the median particle size D50 of the coating layer is greater than or equal to 10 nm 50 less than or equal to 200 nm, and / or, the specific surface area of the coating layer is greater than or equal to 10 m 2 / g; And / or, the ionic conductivity of the coating layer is greater than 0.1mS / cm.

7. The multinary cathode material of claim 6, wherein, The coating layer has a characteristic peak intensity I(215) of (215) crystal face and a characteristic peak intensity I(014) of (014) crystal face measured by XRD, which satisfy the following relationship: 0.32 < I (215) / I (014) <0.67; and, the characteristic peak area S of the (215) crystal face measured by XRD of the cladding layer (215) and the characteristic peak area S of the (014) crystal face (014) satisfies the following relationship: 0.005 < S (215) / S (014) <0.03; And / or, the ionic conductivity of the coating layer is greater than 0.4mS / cm.

8. A method for preparing an interface-stable multi-element positive electrode material, characterized by, The preparation method comprises the following steps: mixing the nickel-based multi-element positive electrode material with the coating layer, first sintering, crushing, and sieving to obtain the interface-stabilized multi-element positive electrode material; The coating layer has a composition shown in Formula I: Li 3+θ-j L j La 1-k Q k (PO4)2formula I; wherein L is selected from Na and / or K, Q is selected from at least one element of Sc, Y, In, Fe, Ce, Pr, Nd, Pm, Sm, Eu, Gd and Tb, 0 < θ < 0.5, 0 < x < 0.5, 0 < y < 0.5, 0 < z < 0.5, and 0 < w < 0.

5. j <1, 0 ≤ k <0.

8.

9. The production method according to claim 8, wherein The nickel-based multi-element positive electrode material has a composition shown in Formula II: Li a Ni 1-x-y Co x M' y M z O2formula II; wherein M' is selected from Mn and / or Al; M is selected from at least one element among Al, Ba, Zr, Ti, Nb, Ta, Ga, Y, W, Ca, Sr, Sc, Cr, Mo, Hf, Si, Sm, V, La, Ce, Mg and B; 0.9 a ≤ 1.3, 0.001 ≤ x ≤ 1, 0 ≤ y ≤ 1, 0 < x < 1 z ≤ 0.1; And / or, the added amount of the coating layer is 0.01wt%-3wt% based on the amount of the nickel-based multi-element positive electrode material.

10. The production method according to claim 9, wherein The added amount of the coating layer is 0.1wt%-2wt% based on the amount of the nickel-based multi-element positive electrode material.

11. The production method according to claim 8 or 9, wherein The first sintering condition comprises: sintering temperature is 250-800℃; sintering time is 4-48h.

12. The method of making according to claim 11, wherein, The first sintering condition comprises: sintering temperature is 300-750℃; sintering time is 8-24h.

13. The production method according to claim 8 or 9, wherein The coating layer is obtained by high-temperature solid-phase treatment and ion exchange treatment in sequence.

14. The production method according to claim 13, wherein The coating layer is prepared according to the following steps: (1) The L source, lanthanum source, optional Q source and phosphorus source are arranged according to n(L):n(La):n(Q):n(P)=3+ θ :1- k : k A mixture is obtained by mixing materials in a molar ratio of 2:

1. (2) mixing, second sintering, crushing and screening the mixture to obtain the coating layer precursor L 3+θ La 1-k Q k (PO4)2; (3) mixing the coating layer precursor L 3+θ La 1-k Q k (PO4)2, a lithium source, and pure water are mixed, sand ground, dried, de-ironed, and sieved to obtain the coating layer. wherein 0≤θ<0.5, the coating layer precursor L 3+θ La 1-k Q k (PO4)2and the lithium source are used in amounts such that n(Li):n(L)=3+ θ-j : j .

15. The method of manufacturing according to claim 14, wherein, The second sintering condition comprises: sintering temperature is 600-1300℃, and sintering time is 9-36h.

16. The method of manufacturing according to claim 15, wherein, The second sintering is two-stage sintering, which is performed according to the following steps: sintering the mixture at 600-900℃ for 1-5h, and then sintering at 800-1300℃ for 8-24h.

17. The production method according to claim 8 or 9, wherein The nickel-based multi-element positive electrode material is prepared according to the following steps: S1, a mixed salt solution is prepared by mixing a cobalt salt, a M' salt, and a nickel salt in a molar ratio of n(Ni):n(Co):n(M') = (1- x-y : x : y : a precipitant and a complexing agent are separately prepared as a precipitant solution and a complexing agent solution, respectively; S2, the mixed salt solution, the precipitant solution and the complexing agent solution are added into a reaction kettle, and a co-precipitation reaction is carried out in an inert atmosphere to obtain a solid-liquid mixed slurry, which is filtered, washed, dried, iron-removed and sieved to obtain a multi-element material precursor; S3, the multi-element material precursor and a lithium source are mixed, thirdly sintered, crushed, iron-removed and sieved to obtain a nickel-based multi-element positive electrode material; The M source is added to step S2 and / or step S3.

18. The method of making according to claim 17, wherein, In step S3, the lithium source is added in an amount according to a molar ratio of 0.90≤n(Li) / [n(Ni)+n(Co)+n(M')]≤1.

30. And / or, the third sintering condition includes: a sintering temperature of 650-1000℃; and a sintering time of 4-48h.

19. The method of making according to claim 18, wherein, The third sintering condition includes: a sintering temperature of 800-950℃; and a sintering time of 8-24h.

20. An interface-stable multi-element positive electrode material prepared by the preparation method of any one of claims 8-19.

21. A lithium-ion battery, characterized by, The lithium ion battery comprises the interface-stable multi-element positive electrode material of any one of claims 1-7 and 20.

Images