A ternary material, preparation method and application

Abstract

The present invention discloses a ternary material, a preparation method and an application. The ternary material has a core-shell structure, wherein the core is a ternary material and the shell comprises three coating layers, which are a mixture layer, a LATP layer and a thermal insulation material layer from the inside to the outside. The mixture layer is a mixture of spinel phase M3O4, rock salt phase MO and fast ion conductor Li3PO4 generated by partial reaction of LATP after high temperature treatment. The thermal insulation material is Bi x O y ACl z The spinel phase M3O4 and rock salt phase MO and fast ion conductor Li3PO4 generated by the high-temperature "lithium-eating" reaction of LATP have stable structures. They are coated on the surface of the ternary material, reducing the contact between the ternary material and the electrolyte, thereby improving the thermal stability of the ternary material. The unreacted LATP and the Li3PO4 generated by the reaction will exist in the form of fast ion conductors, improving the rate and power performance of the ternary material. The coating of nano-insulation materials helps the ternary material to be heated to too high a temperature, further improving the thermal stability of the ternary material.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium ion battery positive electrode material preparation, and specifically relates to a ternary material, a preparation method and an application thereof. Background Art

[0002] Lithium-ion batteries, due to their high energy density, safety, environmental friendliness, and long life, have been widely used in electric vehicles, power tools, and energy storage. Ternary materials (referred to as ternary materials)—lithium iron phosphate and lithium nickel cobalt manganese (or aluminum) oxide—are currently the primary cathode materials for lithium-ion batteries. High energy density is one of the primary advantages of ternary materials, due to their high capacity and voltage. As market demands for battery energy density continue to rise, high-energy-density ternary materials are attracting significant attention and becoming a current research focus.

[0003] Although ternary materials have higher energy density, their thermal stability is poorer than that of lithium iron phosphate. The main methods to improve the thermal stability of ternary materials include single crystallization, bulk element doping and surface coating modification. Among them, surface coating is an effective modification strategy that can protect the surface of ternary materials from electrolyte corrosion and inhibit the highly active Ni 4+ The article "An In Situ Formed Surface Coating Layer Enabling LiCoO2with Stable4.6V High-Voltage Cycle Performances" reports that LiCoO2 coated with LATP can significantly increase the starting decomposition temperature of LiCoO2 material and improve its thermal stability, but the initial capacity decreases significantly. 1.4 Al 0.4 Ti 1.6 (PO4)3Solid Electrolyte with Various CathodeMaterials for Solid-State Batteries》The literature reports that LATP coated ternary materials are heat treated at high temperature, and the lattice Li + Will diffuse into the LATP bulk phase, along with Li + The increased amount of escape causes the surface reaction of the ternary material to form phases such as M3O4, MO, Li3PO4, and TiO2 (M = Ni, Co, Mn). Therefore, how to ensure that the solid electrolyte LATP coating does not reduce the capacity of the finished product while improving the thermal stability of the finished product is an urgent problem to be solved. Summary of the Invention

[0004] In view of the deficiencies in the prior art, the present invention aims to provide a ternary material with high thermal stability, a preparation method and an application thereof.

[0005] The ternary material provided by the present invention has a core-shell structure, wherein the core is the ternary material and the shell comprises three coating layers, which are, from the inside to the outside, a mixture layer, a LATP layer and a thermal insulation material layer;

[0006] The molecular formula of the ternary material is LiNi x Co y M 1-x-y O2, wherein M is at least one of Mn, Al, W, Zr, Mg, B, Nb, Ta, Mo, La and Ti, x ≥ 0.50, 0 ≤ y ≤ 0.50;

[0007] The mixture layer is a mixture of spinel phase M'3O4 and rock salt phase M'O and fast ion conductor Li3PO4 generated by partial reaction of LATP after high temperature treatment, wherein M'=at least one of Ni, Co, Mn, Al, W, Zr, Mg, B, Nb, Ta, Mo, La and Ti;

[0008] The thermal insulation material is Bi x O y ACl z , wherein A is Se and / or Te, x=2~4, y=3~4, z=2~3.

[0009] The ternary material provided by the present invention is prepared by a method comprising the following steps:

[0010] 1) dispersing nano-LATP solid electrolyte in a solvent, then adding a soluble lithium salt, ultrasonicating, and stirring to obtain a mixed slurry;

[0011] 2) adding the ternary material to the mixed slurry prepared in step 1), ultrasonically stirring, stirring evenly, and then drying to obtain a dry material;

[0012] 3) The obtained dried material is uniformly heated to a sintering temperature of 1 in a compressed air or oxygen atmosphere, and kept warm, and then naturally cooled to room temperature to obtain an intermediate material;

[0013] 4) The obtained intermediate material is mixed with the nano thermal insulation material, and then placed in a compressed air or oxygen atmosphere, uniformly heated to a sintering temperature of 2, and kept warm, and then naturally cooled to room temperature to obtain the final product.

[0014] In step 1) of the above method, the primary particle size of the nano-LATP solid electrolyte is ≤20nm, the secondary particle size is ≤100nm, and the ion conductivity is ≥5×10 -4 S / cm;

[0015] The solvent is one or more of deionized water, methanol, ethanol, propanol, and acetone, and the liquid-to-solid ratio of the solvent to the nano-LATP solid electrolyte is 10-1000g:1g;

[0016] The soluble lithium salt is one or more of lithium ethoxide, lithium acetate, lithium citrate, lithium formate, and lithium oxalate;

[0017] The mass ratio of the soluble lithium salt to the nano-LATP solid electrolyte is 0.005-0.05:1, specifically 0.01:1;

[0018] In step 2) of the above method, the molecular formula of the ternary material is LiNi x Co y M 1-x-y O2, wherein M is at least one of Mn, Al, W, Zr, Mg, B, Nb, Ta, Mo, La and Ti, x ≥ 0.50, 0 ≤ y ≤ 0.50, and the solid-liquid ratio of the ternary material to the mixed slurry is 1g:0.3-5g;

[0019] The mass ratio of the ternary material to the nano-LATP solid electrolyte is 1:0.002 to 0.02, specifically 1:0.01 or 1:0.02;

[0020] In step 3) of the above method, the uniform heating rate may be 1-10°C / min, specifically 2°C / min, the sintering temperature 1 may be 300-700°C, specifically 700°C, and the holding time may be 3-10 hours, specifically 5 hours;

[0021] In step 4) of the above method, the nano thermal insulation material is Bi x O y ACl z , where A is Se and / or Te, x=2~4, y=3~4, z=2~3, and the particle size of the nano thermal insulation material is D 50 The nano thermal insulation material is 30 to 200 nm, and the amount of the nano thermal insulation material added accounts for 0.1% to 2% of the mass of the intermediate material, specifically 0.2% or 1%;

[0022] The uniform heating rate may be 1-10°C / min, specifically 2°C / min, the sintering temperature 2 may be 200-500°C, specifically 400°C, and the heat preservation time may be 3-10h, specifically 5h.

[0023] The ternary material prepared by the above method and the application of the ternary material in lithium-ion batteries also fall within the scope of protection of the present invention.

[0024] In the application, the ternary material is used as a positive electrode active material for a lithium ion battery or is used to prepare a positive electrode material for a lithium ion battery.

[0025] The present invention also provides a lithium ion battery, wherein the positive electrode material of the lithium ion battery contains the above-mentioned ternary material.

[0026] The present invention has the following beneficial effects:

[0027] (1) Taking advantage of the high-temperature "lithium-eating" property of LATP, the solid electrolyte and lithium salt are evenly mixed before coating the ternary material, and the supplementary lithium salt is used as sacrificial lithium to avoid excessive lithium ion loss in the ternary material, which leads to material capacity loss. After high-temperature treatment, LATP partially reacts to generate spinel phase M'3O4 and rock salt phase M'O and fast ion conductor Li3PO4 ( Figure 5 In addition, the nano thermal insulation material is coated on the surface of the ternary material by low-temperature calcination to form a three-layer coated ternary material;

[0028] (2) The spinel phase M'3O4 and rock salt phase M'O and fast ion conductor Li3PO4 generated by the high-temperature "lithium consumption" reaction of LATP are structurally stable and are coated on the surface of the ternary material, reducing the contact between the ternary material and the electrolyte, thereby improving the thermal stability of the ternary material. The unreacted LATP and the Li3PO4 generated by the reaction will exist in the form of fast ion conductors, improving the rate and power performance of the ternary material. The coating of nano-insulation materials helps the ternary material to withstand high temperatures, further improving the thermal stability of the ternary material. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 TEM image of nano-LATP in Example 1;

[0030] Figure 2 This is a further enlarged TEM image of the nano-LATP in Example 1;

[0031] Figure 3 For LiNi in Example 1 0.88 Co 0.07 Mn 0.05 SEM image of the sample after high-temperature sintering of O2 ternary material coated nano-LATP;

[0032] Figure 4 For LiNi in Example 1 0.88 Co 0.07 Mn 0.05 TEM image of the sample after high-temperature sintering of O2 ternary material coated nano-LATP;

[0033] Figure 5 For LiNi in Example 1 0.88 Co 0.07 Mn 0.05 XRD pattern of the sample after high temperature sintering of O2 ternary material coated nano-LATP;

[0034] Figure 6 The LiNi with high thermal stability in Example 1 0.88 Co 0.07 Mn 0.05 SEM image of O2 ternary material;

[0035] Figure 7 The LiNi with high thermal stability in Example 1 0.88 Co 0.07 Mn 0.05 TEM image of O2 ternary material;

[0036] Figure 8 LiNi in Comparative Example 1 0.88 Co 0.07 Mn 0.05 SEM image of O2 ternary material;

[0037] Figure 9 LiNi in Comparative Example 1 0.88 Co 0.07 Mn 0.05 XRD patterns of O2 ternary materials;

[0038] Figure 10 For LiNi in Comparative Example 12 0.88 Co 0.07 Mn 0.05 SEM image of the sample of O2 ternary material after high-temperature sintering. DETAILED DESCRIPTION

[0039] The present invention will be further described in detail below in conjunction with specific embodiments. The examples provided are only for illustrating the present invention and are not intended to limit the scope of the present invention. The examples provided below can serve as a guide for further improvements by those skilled in the art and are not intended to limit the present invention in any way.

[0040] Unless otherwise specified, the experimental methods in the following examples are conventional methods and were performed according to the techniques or conditions described in the literature in the field or according to the product instructions. The materials and reagents used in the following examples, unless otherwise specified, were all commercially available.

[0041] The first aspect of the present invention discloses a ternary material with high thermal stability, which has a core-shell structure. The core is the ternary material, and the shell comprises three coating layers, which are, from the inside to the outside, a mixture layer, a LATP layer, and a thermal insulation material layer.

[0042] The molecular formula of the ternary material is LiNi x Co y M 1-x-yO2, wherein M is at least one of Mn, Al, W, Zr, Mg, B, Nb, Ta, Mo, La and Ti, x ≥ 0.50, 0 ≤ y ≤ 0.50;

[0043] The mixture layer is a mixture of spinel phase M'3O4, rock salt phase M'O and fast ion conductor Li3PO4 generated by partial reaction of LATP after high temperature treatment; wherein M'=at least one of Ni, Co, Mn, Al, W, Zr, Mg, B, Nb, Ta, Mo, La and Ti;

[0044] The thermal insulation material is Bi x O y ACl z , wherein A is Se and / or Te, x=2~4, y=3~4, z=2~3.

[0045] The second aspect of the present invention discloses a method for preparing a ternary material with high thermal stability, which specifically comprises the following steps:

[0046] S1. Nano solid LATP (Li 1.4 Al 0.4 Ti 1.6 (PO4)3) is dispersed in a solvent, and then a soluble lithium salt is added, ultrasonicated, and stirred to obtain a mixed slurry;

[0047] S2. The ternary material was added to the mixed slurry prepared in S1, ultrasonically stirred, and then dried in a vacuum oven to obtain a dry material;

[0048] S3. The dried material obtained in S2 is placed in a compressed air or oxygen atmosphere, uniformly heated to a sintering temperature of 1, and kept warm, and then naturally cooled to room temperature to obtain an intermediate material;

[0049] S4. The intermediate material obtained in S3 is uniformly mixed with the nano thermal insulation material, and then placed in a compressed air or oxygen atmosphere, uniformly heated to a sintering temperature of 2, and kept warm, and then naturally cooled to room temperature to obtain the final product.

[0050] The present invention first mixes nano-LATP with a sacrificial lithium source evenly, and then coats it on the surface of the ternary material, so that the LATP "eats lithium" at high temperature and reacts with the sacrificial lithium source, thereby preventing excessive lithium ions in the ternary material from diffusing into the LATP, resulting in a decrease in the material capacity. The LATP "eats lithium" reaction generates spinel phase M'3O4 and rock salt phase M'O and fast ion conductor Li3PO4, which have a stable structure and are coated on the surface of the ternary material, reducing the contact between the ternary material and the electrolyte and improving the thermal stability of the ternary material. The unreacted LATP and the Li3PO4 generated by the reaction will exist in the form of fast ion conductors, improving the rate and power performance of the ternary material. The nano-insulation material coating blocks external heat from radiating to the ternary material, apparently increasing the heat resistance temperature of the ternary material, thereby improving its thermal stability.

[0051] Furthermore, in step S1, the primary particle size of the nano-LATP is ≤20 nm, the secondary particle size is ≤100 nm, and the ionic conductivity is ≥5×10 -4 S / cm;

[0052] In step S1, the solvent is one or more of deionized water, methanol, ethanol, propanol, and acetone, and the liquid-to-solid ratio of the solvent to the nano solid electrolyte is 10-100 g:1 g;

[0053] In step S1, the soluble lithium salt is one or more of lithium ethoxide, lithium acetate, lithium citrate, lithium formate, and lithium oxalate, and the mass ratio of the soluble lithium salt to the nano solid electrolyte is 0.005 to 0.05:1;

[0054] In step S2, the molecular formula of the ternary material is LiNi x Co y M 1-x-y O2, wherein M is at least one of Mn, Al, W, Zr, Mg, B, Nb, Ta, Mo, La and Ti, x ≥ 0.50, 0 ≤ y ≤ 0.50, the solid-liquid ratio of the ternary material to the mixed slurry is 1g:0.3-5g, and the mass ratio of the ternary material to the solid electrolyte is 1:0.002-0.02;

[0055] In step S3, the uniform heating rate is 1-10°C / min, the sintering temperature 1 is 300-700°C, and the holding time is 3-10h;

[0056] The nano thermal insulation material in step S4 is Bi x O y ACl z , A=one or two of Se and Te, x=2~4, y=3~4, z=2~3, particle size D of nano thermal insulation material 50 The size is controlled to be 30-200nm, and the amount of nano thermal insulation material added accounts for 0.1%-2% of the mass of the intermediate material;

[0057] In step S4, the uniform heating rate is 1-10°C / min, the sintering temperature 2 is 200-500°C, and the holding time is 3-10 hours.

[0058] The invention also discloses the application of the high-nickel ternary material with high thermal stability prepared according to the method in lithium-ion batteries.

[0059] The technical solution of the present invention will be described more clearly and completely below with reference to specific embodiments.

[0060] Example 1

[0061] Weigh 1g of nano LATP (Li 1.4 Al 0.4 Ti 1.6 (PO4)3) The material was placed in 50g of ethanol, and the secondary particle size of nano-LATP was 50nm. Figure 1 As shown, the primary particle size is 10 nm, as Figure 1 and Figure 2 As shown, 0.01 g of lithium ethoxide was then added to the ethanol, ultrasonicated, and stirred until the lithium ethoxide was completely dissolved and the nano-LATP was evenly dispersed in the ethanol to obtain LATP ethanol slurry.

[0062] Then 100g of LiNi 0.88 Co 0.07 Mn 0.05 The O2 ternary material was added to the above-mentioned LATP ethanol slurry, stirred and slurried uniformly at a speed of 300 r / min, and then placed in a vacuum oven at 100° C. and dried for 5 h to obtain a dry material.

[0063] The dried material was then placed in a tube furnace, oxygen was introduced, and the temperature was raised from room temperature to 700°C at a heating rate of 2°C / min, kept warm for 5 hours, and then naturally cooled to room temperature to obtain an intermediate material.

[0064] Figure 3 LiNi 0.88 Co 0.07 Mn 0.05 SEM image of the sample after high-temperature sintering of O2 ternary material coated nano-LATP;

[0065] Figure 4 LiNi 0.88 Co 0.07 Mn 0.05 TEM image of the sample after high-temperature sintering of O2 ternary material coated nano-LATP;

[0066] Figure 5 LiNi 0.88 Co 0.07 Mn 0.05XRD pattern of the sample after high temperature sintering of O2 ternary material coated nano-LATP;

[0067] Depend on Figure 5 It can be seen that nano-LATP is coated on LiNi 0.88 Co 0.07 Mn 0.05 The surface of the O2 ternary material, after high-temperature sintering treatment, generates Li3PO4, spinel phase M'3O4 and rock salt phase M'O.

[0068] Mix 100g of the intermediate material with 0.2g of nano Bi4O4TeCl2. 50 The particle size is 50nm. The mixed material is then placed in a tube furnace and heated from room temperature to 400℃ at a vacuum rate of 2℃ / min, kept warm for 5h, and then cooled naturally to room temperature to obtain LiNi with high thermal stability. 0.88 Co 0.07 Mn 0.05 O2 elemental materials.

[0069] Figure 6 To obtain high thermal stability LiNi 0.88 Co 0.07 Mn 0.05 Surface SEM image of O2 ternary material.

[0070] Figure 7 The obtained LiNi with high thermal stability 0.88 Co 0.07 Mn 0.05 TEM image of O2 ternary material.

[0071] Depend on Figure 6 and Figure 7 It can be seen that the thermal insulation material Bi4O4TeCl2 is successfully coated on LiNi 0.88 Co 0.07 Mn 0.05 O2 ternary material surface.

[0072] Comparative Example 1

[0073] Directly take 100g LiNi 0.88 Co 0.07 Mn 0.05 The O2 ternary single crystal material is not coated with LATP and thermal insulation materials, and its SEM image is as follows Figure 8 shown.

[0074] Figure 9 LiNi 0.88 Co 0.07 Mn 0.05 XRD pattern of O2 ternary material.

[0075] Comparative Example 2

[0076] Compared with Example 1, 100g LiNi 0.88 Co 0.07 Mn 0.05 O2 ternary single crystal material was added to LATP ethanol slurry (weighing 1g nano LATP (Li 1.4 Al 0.4 Ti 1.6 (PO4)3) The material was placed in 50g of ethanol, ultrasonicated, and nano-LATP was evenly dispersed in the ethanol to obtain LATP ethanol slurry), ultrasonicated, stirred, and then placed in a vacuum oven at 100°C for 5 hours to obtain a dry material. The dry material was then placed in a tube furnace, oxygen was introduced, and the temperature was increased from room temperature to 700°C at a rate of 2°C / min, kept at this temperature for 5 hours, and then naturally cooled to room temperature to obtain nano-LATP-coated LiNi 0.88 Co 0.07 Mn 0.05 O2 ternary single crystal material.

[0077] Comparative Example 3

[0078] Compared with Example 1, LiNi 0.88 Co 0.07 Mn 0.05 The O2 ternary single crystal material was added to the LATP ethanol slurry in which lithium ethanol was dissolved, stirred and slurried evenly at a speed of 300 r / min, and then placed in a vacuum oven at 100 ° C and dried for 5 hours to obtain a dry material. The dry material was then placed in a tube furnace, oxygen was introduced, and the temperature was raised from room temperature to 700 ° C at a rate of 2 ° C / min, kept at this temperature for 5 hours, and then naturally cooled to room temperature to obtain nano-LATP-coated LiNi 0.88 Co 0.07 Mn 0.05 O2 ternary single crystal material.

[0079] Comparative Example 4

[0080] Compared with Example 1, 100g LiNi 0.88 Co 0.07 Mn 0.05 O2 ternary single crystal material is mixed evenly with 0.2g nano Bi4O4TeCl2, and the D 50 The particle size is 50nm. Then the mixed material is placed in a tube furnace, and the temperature is raised from room temperature to 400℃ at a vacuum rate of 2℃ / min, kept at this temperature for 5h, and then naturally cooled to room temperature to obtain Bi4O4TeCl2 coated LiNi 0.88 Co 0.07 Mn 0.05 O2 ternary material.

[0081] Example 2

[0082] Compared with Example 1, the secondary particle size of nano-LATP is controlled to be 80 nm, the primary particle size is controlled to be 20 nm, and the other steps are the same as Example 1.

[0083] Comparative Example 5

[0084] Compared with Example 1, the secondary particle size of nano-LATP is controlled to be 200 nm, and the other steps are the same as Example 1.

[0085] Example 3

[0086] Compared with Example 1, the coating amount of nano-LATP was increased from 1 g to 2 g, the addition amount of lithium ethoxide was increased from 0.01 g to 0.03 g, and the other steps were the same as Example 1.

[0087] Comparative Example 6

[0088] Compared with Example 1, the coating amount of nano-LATP was reduced from 1 g to 0.1 g, and the addition amount of lithium ethoxide was reduced from 0.01 g to 0.005 g. Other steps were the same as in Example 1.

[0089] Comparative Example 7

[0090] Compared with Example 1, the coating amount of nano-LATP was increased from 1 g to 3 g, the addition amount of lithium ethoxide was increased from 0.01 g to 0.06 g, and the other steps were the same as Example 1.

[0091] Example 4

[0092] Compared with Example 1, the amount of lithium ethoxide added was increased from 0.01 g to 0.04 g, and the other steps were the same as Example 1.

[0093] Comparative Example 8

[0094] Compared with Example 1, the amount of lithium ethoxide added was increased from 0.01 g to 0.1 g, and the other steps were the same as Example 1.

[0095] Comparative Example 9

[0096] Compared with Example 1, the amount of lithium ethoxide added was reduced from 0.01 g to 0.0005 g, and the other steps were the same as Example 1.

[0097] Example 5

[0098] Compared with Example 1, the coating amount of the nano thermal insulation material Bi4O4TeCl2 was increased to 1 g, and the other steps were the same as Example 1.

[0099] Comparative Example 10

[0100] Compared with Example 1, the coating amount of the nano thermal insulation material Bi4O4TeCl2 was increased to 2.5 g, and the other steps were the same as Example 1.

[0101] Comparative Example 11

[0102] Compared with Example 1, the coating amount of the nano thermal insulation material Bi4O4TeCl2 was reduced to 0.05 g, and the other steps were the same as Example 1.

[0103] Comparative Example 12

[0104] Take 100g LiNi 0.88 Co 0.07 Mn 0.05 The O2 ternary single crystal material is directly placed in a tube furnace, oxygen is introduced, and the temperature is increased from room temperature to 700°C at a rate of 2°C / min, kept at this temperature for 5 hours, and then naturally cooled to room temperature after the end of the heat preservation. Then, after it is crushed, it is placed in a tube furnace again, oxygen is introduced, and the temperature is increased from room temperature to 400°C at a rate of 2°C / min, kept at this temperature for 5 hours, and then naturally cooled to room temperature after the end of the heat preservation to obtain the final product.

[0105] Figure 10 LiNi 0.88 Co 0.07 Mn 0.05 SEM image of the sample of O2 ternary material after high-temperature sintering.

[0106] Test Case

[0107] 1. From Figure 6 and Figure 8 It can be seen that the high thermal stability LiNi prepared by coating with nano-LATP and thermal insulation material Bi4O4TeCl2 in Example 1 0.88 Co 0.07 Mn 0.05 There are a lot of nanoparticles on the surface of O2 ternary material, which is different from LiNi without any treatment. 0.88 Co 0.07 Mn 0.05 O2 ternary materials are in sharp contrast; Figure 5 and Figure 9 It can be seen that compared with the comparative example 1, the XRD diffraction peaks of Example 1 contain characteristic peaks of non-ternary materials, which correspond to Li3PO4, M'O, M'3O4 and LATP, respectively, indicating that the nano-LATP coated LiNi 0.88 Co 0.07 Mn 0.05 O2 ternary material reacts partially to generate Li3PO4, M'O, M'3O4 after high temperature sintering. Figure 3 and Figure 4 It can be seen that nano-LATP coated LiNi 0.88Co 0.07 Mn 0.05 The O2 ternary material forms two coating layers on its surface, which are Li3PO4, M'O and M'3O4 coating layers and LATP coating layers from the inside to the outside; Figure 7 It can be seen that the thermal insulation material Bi4O4TeCl2 is non-uniformly coated with LiNi 0.88 Co 0.07 Mn 0.05 On the surface of O2 ternary material, some areas are agglomerated; Figure 10 It can be seen that LiNi 0.88 Co 0.07 Mn 0.05 The O2 ternary material is not coated with nano-LATP and thermal insulation material Bi4O4TeCl2. The surface of the sample is slightly smooth and the edges and corners are slightly rounded when it is only sintered at high temperature.

[0108] 2. The ternary materials in Examples 1-5 and Comparative Examples 1-12, the conductive agent SP, and the binder PVDF were respectively prepared in a mass ratio of 97.5:1:1.5 using NMP as a solvent to prepare a pole piece, which was coated on a carbon-coated aluminum foil, dried at 100°C for 5h, and compacted on a roller press to obtain a positive electrode sheet.

[0109] Using metallic lithium sheets as negative electrodes, 1M LiPF6 solution as electrolyte, and cell gard 2300 as separator, they were assembled into button cells with the above-mentioned positive electrodes. They were charged and discharged at a rate of 0.2C within the cut-off voltage range of 2.8 to 4.35V, and then charged at a rate of 0.33C to 4.35V. The positive electrodes were disassembled for DSC testing.

[0110] 3. The ternary materials in Examples 1 to 5 and Comparative Examples 1 to 12, the conductive agent CNTs, and the binder PVDF were mixed in a mass ratio of 98:1:1 using NMP as solvent, and the solid content was controlled to 70%. The slurry was then coated on the current collector aluminum foil, and the single surface density was controlled to 215 g / m 2 After roller pressing, the electrode sheet had a compaction density of 3.60 g / cm³. A 3Ah soft-pack battery was assembled with a graphite negative electrode sheet using a NP ratio of 1.13, a 1M LiPF₆ solution as the electrolyte, and Cellgard 2300 as the separator. After formation, two cycles of 0.33C charge and discharge were performed, achieving a 0.33C gram capacity. The electrochemical properties of the product are shown in Table 1.

[0111] Table 1

[0112]

[0113] As can be seen from the description in Table 1, compared with Comparative Example 1, the residual alkali content in Example 1 is slightly reduced. This is because under high-temperature sintering conditions, Li in the residual alkali diffuses into the LATP lattice; compared with Comparative Example 1, the DSC peak decomposition temperature in Example 1 is significantly increased, mainly because LATP coats the ternary material to generate spinel phase M'3O4 and rock salt phase M'O and fast ion conductor Li3PO4, all of which have high thermal stability. In addition, the thermal insulation material Bi4O4TeCl2 can block the diffusion of external heat for the ternary material, thereby significantly improving the thermal stability of the ternary material; in addition, compared with Comparative Example 1, the full electric capacity in Example 1 is significantly increased, and the cycle performance is improved. This is because the use of LATP and soluble lithium salt to co-coat the ternary material can prevent LATP from "eating up" excessive lithium in the ternary material matrix, thereby ensuring the capacity of the ternary material. The unreacted LATP itself is a fast ion conductor, which can improve the rate performance of the material and increase the capacity of the material. The LATP and Bi4O4TeCl2 coating layers can further block the side reactions between the ternary material and the electrolyte, thereby improving the cycling performance of the material.

[0114] Compared with Comparative Example 2, the DSC peak decomposition temperature of the material in Example 1 is significantly increased. This is mainly because the thermal insulation material Bi4O4TeCl2 is a ternary material that blocks the diffusion of external heat, thereby significantly improving the thermal stability of the ternary material.

[0115] Compared with Comparative Example 3, Example 1 shows a significant increase in the DSC peak decomposition temperature, primarily due to the effect of the thermal insulation material Bi4O4TeCl2. Furthermore, the all-electric specific capacity of the material in Comparative Example 3 is significantly higher than that in Comparative Example 2. This is primarily because LATP "eats" the lithium in the ternary material matrix at high temperatures, resulting in a decrease in the ternary material's capacity. By co-coating the ternary material with a soluble lithium salt, LATP can obtain lithium from the lithium salt at high temperatures, reducing the amount of lithium obtained from the ternary material. Furthermore, the unreacted LATP itself is a fast ion conductor, which improves the material's rate performance, increasing its capacity rather than decreasing it.

[0116] Compared with Comparative Example 4, Example 1 shows significant improvements in thermal stability, capacity, and cycling performance. Because the thermal insulation material Bi4O4TeCl2 has weak ionic and electronic conductivity, coating it alone would reduce capacity. Furthermore, the synergistic effect of LATP and the Bi4O4TeCl2 double-layer coating gives the ternary material excellent thermal stability and cycling performance.

[0117] The thermal stability of Examples 1-2 is significantly better than that of Comparative Example 5. This is because the LATP particles are too large, resulting in uneven coating and little improvement in the thermal stability of the ternary material.

[0118] Compared with Comparative Example 6, Examples 1 and 3 have too little LATP coating, and the thermal stability of the ternary material is not significantly improved. Compared with Comparative Example 7, the LATP coating amount is too much, and the thermal stability of the ternary material is significantly improved, but the capacity is significantly reduced.

[0119] Compared with Comparative Example 9, in Examples 1 and 4, the coating amount of soluble lithium salt is too small, and LATP "eats up" the lithium in the ternary material matrix, resulting in a decrease in the capacity of the ternary material; compared with Comparative Example 8, the coating amount of soluble lithium salt is too much, resulting in an increase in residual alkali and a decrease in capacity.

[0120] In Examples 1 and 5 and Comparative Example 10, the thermal insulation material Bi4O4TeCl2 coating amount is too much, and although the thermal stability of the material is significantly improved, the capacity is also significantly reduced; compared with Comparative Example 11, the thermal insulation material Bi4O4TeCl2 coating amount is too little, and the thermal stability of the material is not significantly improved.

[0121] Compared with Comparative Examples 1 and 12, Examples 1-5 can effectively improve the thermal stability of the ternary material, increase the capacity of the material, and improve the rate performance by coating with LATP and the thermal insulation material Bi4O4TeCl2 and performing heat treatment.

[0122] The present invention has been described in detail above. For those skilled in the art, without departing from the purpose and scope of the present invention, and without the need to carry out unnecessary experimental conditions, the present invention can be implemented in a wide range under equivalent parameters, concentrations and conditions. Although the present invention provides specific embodiments, it should be understood that further improvements can be made to the present invention. In short, according to the principles of the present invention, this application is intended to include any changes, uses or improvements to the present invention, including changes that depart from the disclosed scope in this application and are made using conventional techniques known in the art.

Claims

1. A ternary material, characterized in that: The ternary material has a core-shell structure, the core is the ternary material, and the shell comprises three coating layers, which are a mixture layer, a LATP layer and a thermal insulation material layer from the inside to the outside. The molecular formula of the ternary material is LiNi x Co y M 1-x-y O2, wherein M is at least one of Mn, Al, W, Zr, Mg, B, Nb, Ta, Mo, La and Ti, x ≥ 0.50, 0 ≤ y ≤ 0.50; The mixture layer is a mixture of spinel phase M'3O4 and rock salt phase M'O and fast ion conductor Li3PO4 generated by partial reaction of LATP after high temperature treatment, wherein M'=at least one of Ni, Co, Mn, Al, W, Zr, Mg, B, Nb, Ta, Mo, La and Ti; The thermal insulation material is Bi x O y ACl z , wherein A is Se and / or Te, x=2-4, y=3-4, z=2-3; The method for preparing the ternary material is characterized in that the method comprises the following steps: 1) dispersing nano-LATP solid electrolyte in a solvent, then adding a soluble lithium salt, ultrasonicating, and stirring to obtain a mixed slurry; 2) adding the ternary material to the mixed slurry prepared in step 1), ultrasonically stirring, stirring evenly, and then drying to obtain a dry material; 3) The obtained dried material is uniformly heated to a sintering temperature of 1 in a compressed air or oxygen atmosphere, and kept warm, and then naturally cooled to room temperature to obtain an intermediate material; 4) mixing the obtained intermediate material with the nano thermal insulation material, then placing it in a compressed air or oxygen atmosphere, uniformly heating it to a sintering temperature of 2, keeping it warm, and then naturally cooling it to room temperature to obtain the final product; In step 1), the secondary particle size of the nano-LATP solid electrolyte is ≤100 nm; The mass ratio of soluble lithium salt to nano-LATP solid electrolyte is 0.005-0.05:1; The mass ratio of ternary material to nano-LATP solid electrolyte is 1:0.002~0.02; The added amount of nano thermal insulation material accounts for 0.1% to 2% of the mass of the intermediate material.

2. The ternary material according to claim 1, characterized in that In step 1), the primary particle size of the nano-LATP solid electrolyte is ≤20 nm, and the ionic conductivity is ≥5×10 -4 S / cm.

3. The ternary material according to claim 1, characterized in that In step 1), the solvent is one or more of deionized water, methanol, ethanol, propanol, and acetone; The liquid-to-solid ratio of the solvent to the nano-LATP solid electrolyte is 10-1000 g:1 g; The soluble lithium salt is one or more of lithium ethoxide, lithium acetate, lithium citrate, lithium formate, and lithium oxalate.

4. The ternary material according to claim 1, characterized in that In step 2), the molecular formula of the ternary material is LiNi x Co y M 1-x-y O2, wherein M is at least one of Mn, Al, W, Zr, Mg, B, Nb, Ta, Mo, La and Ti, x≥0.50, 0≤y≤0.50, and the solid-liquid ratio of the ternary material to the mixed slurry is 1g:0.3~5g.

5. The ternary material according to claim 1, characterized in that In step 3), the uniform heating rate is 1-10° C. / min, the sintering temperature 1 is 300-700° C., and the holding time is 3-10 h.

6. The ternary material according to claim 1, characterized in that In step 4), the nano thermal insulation material is Bi x O y ACl z , where A is Se and / or Te, x=2~4, y=3~4, z=2~3, and the particle size of the nano thermal insulation material is D 50 30~200nm; The uniform heating rate is 1-10°C / min, the sintering temperature 2 is 200-500°C, and the heat preservation time is 3-10h.

7. The ternary material according to any one of claims 1 to 6 is used as a positive electrode active material for a lithium ion battery or is used for preparing a positive electrode material for a lithium ion battery.

8. A positive electrode, characterized in that The positive electrode uses the ternary material according to any one of claims 1 to 6 as the positive electrode active material.

9. A lithium-ion battery, characterized in that: The lithium-ion battery comprises the positive electrode according to claim 8.

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