A composite solid electrolyte coated modified positive electrode material and its preparation method and application

Abstract

The present invention belongs to the field of positive electrode materials for lithium batteries, and discloses a positive electrode material coated and modified with a composite solid electrolyte, wherein the single-layer coating is composed of a composite of an organic polymer and an inorganic chloride. The organic polymer can improve the elasticity of the coating, alleviate the volume strain of the positive electrode material, and avoid rupture of the coating; the inorganic chloride has high ionic conductivity and can improve the transmission of lithium ions at the electrode interface. The present invention also discloses a method for preparing the positive electrode material. LiCl, the synthetic raw material for the inorganic chloride, serves as an initiator for the synthesis of the organic polymer. At the same time, the product water of the polymerization reaction participates in the formation of the inorganic chloride intermediate, ultimately achieving in-situ synthesis and uniform coating of the organic polymer and the inorganic chloride on the surface of the positive electrode material. The preparation method is simple and the raw material conversion rate is high. The application of the positive electrode material in lithium-ion batteries is also disclosed. The positive electrode material of the present invention can effectively improve battery cycle stability, rate performance, and other performance.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery positive electrode materials, and in particular to a composite solid electrolyte coated modified positive electrode material, a preparation method and applications thereof. Background Art

[0002] For nickel-based ternary materials, increasing nickel content is the main means to increase material specific capacity and improve battery energy density, but research has found that increasing the nickel content of the material will cause a series of problems. As the nickel content increases, the Li / Ni mixing becomes more severe, which will hinder the Li + transport; at the same time, the high nickel content will also aggravate the side reactions of the material with water and oxygen during storage, generating residual lithium compounds such as LiOH and Li2CO3, which will cause the slurry to condense during mixing and gas production during the cycle. In addition, during the charge and discharge process, the initial potential of oxygen evolution will decrease with the increase of nickel content, which will cause the phase transition between the layered phase-spinel phase-rock salt phase of the material to be more intense, resulting in cracks inside the particles during the cycle, and the cracking of the intergranular and grain boundaries causes the new surface to be exposed to the electrolyte for side reactions, triggering gas production, causing the capacity to decay rapidly during the cycle and leading to serious safety hazards. In summary, the development of high-nickel ternary positive electrode materials is an inevitable development trend. In order to solve the series of problems brought about by this, the modification research of traditional ternary positive electrode materials is particularly important.

[0003] Surface coating of cathode materials is a common modification method. By coating the surface of the material with a layer of electrochemically active or inert material, direct contact between the electrode and the electrolyte can be isolated, improving the cycling stability of the cathode material. However, the coating layer often has low lithium ion conductivity, resulting in poor rate performance of the cathode material. Solid-state electrolytes, with their high lithium ion conductivity and electrochemical stability, are ideal coating materials.

[0004] Among them, the organic polymer electrolyte coating has a certain elasticity, which can release the internal stress caused by the volume change of the positive electrode material during the charge and discharge process, alleviate the generation of microcracks, and at the same time, its excellent flexibility can prevent the coating from breaking. However, its low room temperature ionic conductivity has limited improvement on ion transport at the interface. In comparison, the inorganic solid electrolyte coating has higher ionic conductivity, but it is not elastic and has difficulty adapting to the volume change of the positive electrode material. It is easy to break and fall off during the cycle. Therefore, a single coating layer is difficult to meet the requirements of comprehensively improving the performance of the positive electrode material. In addition, common solid electrolytes often have complex preparation processes. After a long preparation process, the synthesized solid electrolyte is mixed and sintered with the positive electrode material. The solid electrolyte synthesis and positive electrode material coating are not achieved simultaneously. Therefore, the process is cumbersome, and it is difficult to achieve a better coating effect through non-in situ synthesis, and the improvement of material performance is minimal.

[0005] CN 117558886 A discloses a surface coating strategy and method for a high-nickel layered oxide cathode of a solid-state lithium-ion battery, which proposes to first perform nano-inorganic fast ion conductor dot coating on the surface of high-nickel layered oxide cathode particles, and then perform ultrathin organic conductive polymer coating.

[0006] CN 117691058 A discloses a double-coated sodium-ion battery composite cathode material and its preparation method. The double-coated layer includes an electrolyte layer and a glass layer, which respectively improve ion transport and high-voltage stability at the interface.

[0007] Although the above method obtains a composite coating layer, the coating layer is a double-layer structure, and the uniform distribution of multiple components is not achieved, making it difficult to achieve multi-effect synergistic effects. There are still problems such as poor mechanical strength of the inorganic layer and low ionic conductivity of the organic layer. Moreover, the coating process is cumbersome and the raw material utilization rate is low, resulting in a large amount of resource consumption.

[0008] Therefore, synchronously realizing the synthesis and coating of composite solid electrolytes on the surface of the cathode material can not only greatly reduce resource consumption and production costs, effectively improve the coating effect, but also maximize the electrochemical performance of the cathode material through the synergistic effect of organic and inorganic electrolytes. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the above background technology, and provide a cathode material modified by composite solid electrolyte coating, its preparation method and application. Design a simple preparation process to synchronously realize the in-situ synthesis and coating of organic and inorganic solid electrolytes on the surface of the cathode material, and improve the cycle stability and rate performance of the cathode material.

[0010] To solve the above technical problems, the technical solution proposed by the present invention is:

[0011] A cathode material modified by composite solid electrolyte coating, including a cathode material matrix and a layer of composite solid electrolyte coated on its surface;

[0012] The composite solid electrolyte includes an organic polymer and an inorganic chloride;

[0013] The structural general formula of the organic polymer is: where 100 < n <1000000>0, and R1 and R2 are alkyl groups with a carbon chain length greater than or equal to 0 and less than 5;

[0014] Preferably, the inorganic chloride is Li3InCl6;

[0015] Preferably, the organic polymer and the inorganic chloride are synchronously synthesized on the surface of the cathode material matrix and uniformly distributed to form a single-layer composite solid electrolyte coating layer.

[0016] Preferably, the positive electrode material matrix includes any one of lithium iron phosphate, lithium cobaltate, lithium manganate, lithium nickelate, lithium nickel cobaltate, lithium nickel manganate, lithium nickel cobalt manganate, and lithium nickel cobalt aluminum oxide.

[0017] Preferably, the general structural formula of the organic monomer is: Wherein R1 and R2 are alkyl groups with carbon chain lengths greater than or equal to 0 and less than 5.

[0018] Based on a general inventive concept, the present invention also provides a method for preparing the above-mentioned composite solid electrolyte coated modified positive electrode material, comprising the following steps:

[0019] (1) Weighing a certain mass of positive electrode material matrix, organic monomer, LiCl, InCl3, and pyridine and mixing them to obtain a mixture;

[0020] (2) pouring the above mixture into a ball mill and subjecting it to mechanical ball milling;

[0021] (3) The ball-milled mixture is heat-treated in an inert atmosphere until the pyridine is completely volatilized, thereby obtaining a composite solid electrolyte-coated modified positive electrode material.

[0022] In the above-mentioned preparation method, preferably, in step (1), the mass ratio of the organic monomer to the positive electrode material matrix is ​​0.1-10:100, the mass ratio of LiCl to the positive electrode material matrix is ​​0.1-10:100, the mass ratio of InCl3 to the positive electrode material matrix is ​​0.1-10:100, the molar ratio of LiCl to InCl3 is 3:1, and the mass ratio of pyridine to the positive electrode material matrix is ​​0.5-5:1.

[0023] In the above preparation method, preferably, in step (2), the ball milling process has a rotation speed of 100-500 r / min and a duration of 2-10 h.

[0024] In the above preparation method, preferably, in step (2), the following chemical reaction occurs to obtain the organic polymer and Li3InCl6·xH2O;

[0025] The synthesis route of the organic polymer is to use LiCl as an initiator to initiate a cationic polymerization reaction of the organic monomer in a pyridine solution. The specific reaction equation is as follows:

[0026]

[0027] The synthesis route of Li3InCl6·xH2O is to use LiCl and InCl3 as reactants and the water released from the above monomer polymerization reaction as an intermediate reactant to synthesize the inorganic chloride precursor Li3InCl6·xH2O. The specific reaction equation is as follows:

[0028]

[0029] In the above preparation method, preferably, in step (3), the inorganic chloride precursor Li3InCl6·xH2O prepared in step (2) is heated and dehydrated to obtain the inorganic chloride Li3InCl6. The specific reaction equation is as follows:

[0030]

[0031] In the above preparation method, preferably, in step (3), the heat treatment temperature is 120-500° C. and the duration is 2-5 h.

[0032] The present invention also provides a lithium-ion battery, which comprises the above-mentioned composite solid electrolyte coated modified positive electrode material or the composite solid electrolyte coated modified positive electrode material obtained by the above-mentioned preparation method.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] (1) The present invention proposes a composite solid electrolyte coated modified positive electrode material, wherein the composite electrolyte is composed of an organic polymer and an inorganic chloride. The organic polymer electrolyte coating layer has a certain elasticity, which can release the internal stress caused by the volume change of the positive electrode material during the charge and discharge process, alleviate the generation of microcracks, and at the same time, its excellent flexibility can avoid the coating layer rupture phenomenon that often occurs in traditional inorganic coated positive electrode materials. The inorganic chloride solid electrolyte coating layer has higher ionic conductivity than the organic polymer, which can effectively improve the ion transport at the interface and enhance the rate performance. Compared with a single solid electrolyte coating layer, the organic and inorganic composite solid electrolyte coating layer has both excellent mechanical strength and high ionic conductivity.

[0035] (2) The present invention proposes a method for preparing a composite solid electrolyte coated modified positive electrode material, which utilizes a carefully designed series of chemical reactions to achieve in-situ synthesis of the coating layer on the positive electrode surface. The method includes the following stages: ① Using LiCl as an initiator, in-situ polymerization of organic monomers on the surface of the positive electrode material is initiated, generating a uniform and compact polymer coating layer; ② LiCl as an initiator does not directly participate in the polymerization reaction, but the water produced by the polymerization reaction induces a reaction between LiCl and InCl3, synthesizing Li3InCl6·xH2O; ③ In the subsequent heat treatment process, Li3InCl6·xH2O is dehydrated, and an inorganic chloride coating layer is synthesized in situ on the positive electrode surface. This series of carefully designed chemical reactions achieves efficient conversion of raw materials. LiCl, the raw material for the synthesis of inorganic chloride, serves as an initiator for the synthesis of organic polymers. At the same time, the water produced by the polymerization reaction participates in the formation of inorganic chloride intermediates, ultimately achieving in-situ synthesis of the composite solid electrolyte coating layer on the surface of the positive electrode material. Compared to traditional multi-step synthesis of multi-layer composite coatings, this method synthesizes a single composite coating layer in a single step. This method is highly innovative and can effectively improve the composite coating effect, resulting in a uniformly distributed and tightly contacted composite coating layer. Furthermore, this method achieves in-situ synthesis of multi-effect coatings through a simple industrial process, which holds great commercial potential.

[0036] (3) Compared with the uncoated positive electrode material, the positive electrode material coated with the organic-inorganic composite solid electrolyte prepared by the method of the present invention has greatly improved the battery performance such as battery cycle stability and rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0038] Figure 1 This is the first charge and discharge curve of the lithium-ion button battery assembled with the positive electrode materials prepared in Example 1 and Comparative Example 1 of the present invention at 25°C and 0.1C;

[0039] Figure 2 This is the 100 cycle performance curve of lithium ion button batteries assembled with the positive electrode materials prepared in Example 1 and Comparative Example 1 of the present invention at 25°C and 1C. DETAILED DESCRIPTION

[0040] In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0041] Unless otherwise defined, all technical terms used hereinafter have the same meanings as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the scope of protection of the present invention.

[0042] Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment, etc. used in the present invention can be obtained through market purchases or can be prepared by existing methods.

[0043] In view of the existing problems, the present invention provides a cathode material modified by coating with a composite solid electrolyte, which includes a cathode material matrix and a layer of composite solid electrolyte coated on its surface;

[0044] The composite solid electrolyte includes an organic polymer and an inorganic chloride;

[0045] The structural general formula of the organic polymer is: where 100 < n <1000000>0, and R1 and R2 are alkyl groups with a carbon chain length greater than or equal to 0 and less than 5;

[0046] Preferably, the inorganic chloride is Li3InCl6;

[0047] Preferably, the organic polymer and the inorganic chloride are synchronously synthesized on the surface of the cathode material matrix and are uniformly distributed to form a single-layer composite solid electrolyte coating layer.

[0048] Preferably, the cathode material matrix includes any one of lithium iron phosphate, lithium cobaltate, lithium manganate, lithium nickelate, lithium nickel cobaltate, lithium nickel manganate, lithium nickel cobalt manganate, and lithium nickel cobalt aluminate.

[0049] Preferably, the structural general formula of the organic monomer is: where R1 and R2 are alkyl groups with a carbon chain length greater than or equal to 0 and less than 5.

[0050] Based on a general inventive concept, the present invention also provides a preparation method for the above-mentioned cathode material modified by coating with a composite solid electrolyte, including the following steps:

[0051] (1) Weigh a certain mass of the cathode material matrix, organic monomer, LiCl, InCl3, and pyridine, and mix them to obtain a mixture;

[0052] (2) Pour the above mixture into a ball mill jar and perform mechanical ball milling;

[0053] (3) Heat-treat the ball-milled mixture material under an inert atmosphere until pyridine completely volatilizes, and then obtain the cathode material modified by coating with a composite solid electrolyte.

[0054] In the above-mentioned preparation method, preferably, in step (1), the mass ratio of the organic monomer to the positive electrode material matrix is ​​0.1-10:100, the mass ratio of LiCl to the positive electrode material matrix is ​​0.1-10:100, the mass ratio of InCl3 to the positive electrode material matrix is ​​0.1-10:100, the molar ratio of LiCl to InCl3 is 3:1, and the mass ratio of pyridine to the positive electrode material matrix is ​​0.5-5:1.

[0055] In the above preparation method, preferably, in step (2), the ball milling process has a rotation speed of 100-500 r / min and a duration of 2-10 h.

[0056] In the above preparation method, preferably, in step (2), the following chemical reaction occurs to obtain the organic polymer and Li3InCl6·xH2O;

[0057] The synthesis route of the organic polymer is to use LiCl as an initiator to initiate a cationic polymerization reaction of the organic monomer in a pyridine solution. The specific reaction equation is as follows:

[0058]

[0059] The synthesis route of Li3InCl6·xH2O is to use LiCl and InCl3 as reactants and the water released from the above monomer polymerization reaction as an intermediate reactant to synthesize the inorganic chloride precursor Li3InCl6·xH2O. The specific reaction equation is as follows:

[0060]

[0061] In the above preparation method, preferably, in step (3), the inorganic chloride precursor Li3InCl6·xH2O prepared in step (2) is heated and dehydrated to obtain the inorganic chloride Li3InCl6. The specific reaction equation is as follows:

[0062]

[0063] In the above preparation method, preferably, in step (3), the heat treatment temperature is 120-500° C. and the duration is 2-5 h.

[0064] The present invention also provides a lithium-ion battery, which comprises the above-mentioned composite solid electrolyte coated modified positive electrode material or the composite solid electrolyte coated modified positive electrode material obtained by the above-mentioned preparation method.

[0065] The following describes the invention through specific embodiments.

[0066] Example 1:

[0067] A composite solid electrolyte coated modified positive electrode material, the preparation method of which is as follows:

[0068] (1) Weigh 100g LiNi 0.9 Co 0.05 Mn 0.05 O2, 1g p-hydroxybenzoic acid, 0.365g LiCl, 0.635g InCl3, 50g pyridine;

[0069] (2) Pour the above mixture into a ball mill, mill at 200 r / min for 5 h, and then take it out;

[0070] (3) The ball-milled material is heat-treated in an inert atmosphere at 200° C. for 3 h, and then taken out after cooling to obtain a composite solid electrolyte-coated modified positive electrode material.

[0071] Example 2:

[0072] A composite solid electrolyte coated modified positive electrode material, the preparation method of which is as follows:

[0073] (1) Weigh 200g LiNi 0.9 Co 0.05 Mn 0.05 O2, 1g p-hydroxybenzoic acid, 0.365g LiCl, 0.635g InCl3, 50g pyridine;

[0074] (2) Pour the above mixture into a ball mill, mill at 200 r / min for 5 h, and then take it out;

[0075] (3) The ball-milled material is heat-treated in an inert atmosphere at 200° C. for 3 h, and then taken out after cooling to obtain a composite solid electrolyte-coated modified positive electrode material.

[0076] Example 3:

[0077] A composite solid electrolyte coated modified positive electrode material, the preparation method of which is as follows:

[0078] (1) Weigh 50g LiNi 0.9 Co 0.05 Mn 0.05 O2, 1g p-hydroxybenzoic acid, 0.365g LiCl, 0.635g InCl3, 50g pyridine;

[0079] (2) Pour the above mixture into a ball mill, mill at 200 r / min for 5 h, and then take it out;

[0080] (3) The ball-milled material is heat-treated in an inert atmosphere at 200° C. for 3 h, and then taken out after cooling to obtain a composite solid electrolyte-coated modified positive electrode material.

[0081] Example 4:

[0082] A composite solid electrolyte coated modified positive electrode material, the preparation method of which is as follows:

[0083] (1) Weigh 100g LiNi 0.9 Co 0.05 Mn 0.05 O2, 0.5g p-hydroxybenzoic acid, 0.365g LiCl, 0.635g InCl3, 50g pyridine;

[0084] (2) Pour the above mixture into a ball mill, mill at 200 r / min for 5 h, and then take it out;

[0085] (3) The ball-milled material is heat-treated in an inert atmosphere at 200° C. for 3 h, and then taken out after cooling to obtain a composite solid electrolyte-coated modified positive electrode material.

[0086] Example 5:

[0087] A composite solid electrolyte coated modified positive electrode material, the preparation method of which is as follows:

[0088] (1) Weigh 100g LiNi 0.9 Co 0.05 Mn 0.05 O2, 1g p-hydroxyphenylacetic acid, 0.365g LiCl, 0.635g InCl3, 50g pyridine;

[0089] (2) Pour the above mixture into a ball mill, mill at 200 r / min for 5 h, and then take it out;

[0090] (3) The ball-milled material is heat-treated in an inert atmosphere at 200° C. for 3 h, and then taken out after cooling to obtain a composite solid electrolyte-coated modified positive electrode material.

[0091] Example 6:

[0092] A composite solid electrolyte coated modified positive electrode material, the preparation method of which is as follows:

[0093] (1) Weigh 100g LiNi 0.9 Co 0.05 Mn 0.05 O2, 1g p-hydroxyphenylpropionic acid, 0.365g LiCl, 0.635g InCl3, 50g pyridine;

[0094] (2) Pour the above mixture into a ball mill, mill at 200 r / min for 5 h, and then take it out;

[0095] (3) The ball-milled material is heat-treated in an inert atmosphere at 200° C. for 3 h, and then taken out after cooling to obtain a composite solid electrolyte-coated modified positive electrode material.

[0096] Example 7:

[0097] A composite solid electrolyte coated modified positive electrode material, the preparation method of which is as follows:

[0098] (1) Weigh 100g LiNi 0.9 Co 0.05 Mn 0.05 O2, 1g p-carboxybenzyl alcohol, 0.365g LiCl, 0.635g InCl3, 50g pyridine;

[0099] (2) Pour the above mixture into a ball mill, mill at 200 r / min for 5 h, and then take it out;

[0100] (3) The ball-milled material is heat-treated in an inert atmosphere at 200° C. for 3 h, and then taken out after cooling to obtain a composite solid electrolyte-coated modified positive electrode material.

[0101] Comparative Example 1:

[0102] An uncoated modified positive electrode material, not a positive electrode material LiNi 0.9 Co 0.05 Mn 0.05 O2 does not undergo any processing.

[0103] Comparative Example 2:

[0104] An organic polymer electrolyte-coated modified positive electrode material, the preparation method of which is as follows:

[0105] (1) Weigh 100g LiNi 0.9 Co 0.05 Mn 0.05 O2, 1g p-hydroxybenzoic acid, 0.365g LiCl, 50g pyridine;

[0106] (2) Pour the above mixture into a ball mill, mill at 200 r / min for 5 h, and then take it out;

[0107] (3) The sample was washed and filtered three times with deionized water to remove LiCl;

[0108] (4) The filtered material is heat-treated under an inert atmosphere at 200° C. for 3 h, and then taken out after cooling to obtain a positive electrode material coated with an organic polymer electrolyte.

[0109] Comparative Example 3:

[0110] An inorganic chloride electrolyte-coated modified positive electrode material, the preparation method of which is as follows:

[0111] (1) Weigh 100g LiNi 0.9 Co 0.05 Mn 0.05 O2, 0.365g LiCl, 0.635g InCl3, 50g deionized water;

[0112] (2) Pour the above mixture into a ball mill, mill at 200 r / min for 5 h, and then take it out;

[0113] (3) The ball-milled material is heat-treated in an inert atmosphere at 200° C. for 3 h, and then taken out after cooling to obtain a positive electrode material coated with an inorganic chloride electrolyte.

[0114] Comparative Example 4:

[0115] A double-layer composite solid electrolyte coated modified positive electrode material, the preparation method of which is as follows:

[0116] (1) Weigh 100g LiNi 0.9 Co 0.05 Mn 0.05 O2, 0.365g LiCl, 0.635g InCl3, 50g deionized water;

[0117] (2) Pour the above mixture into a ball mill, mill at 200 r / min for 5 h, and then take it out;

[0118] (3) The ball-milled material is heat-treated under an inert atmosphere at 200° C. for 3 h, and then taken out after cooling to obtain an inorganic chloride-coated modified positive electrode material;

[0119] (4) Weigh 100 g of Li3InCl6-coated modified cathode material, 1 g of p-hydroxybenzoic acid, 0.1 g of LiCl, and 50 g of pyridine;

[0120] (5) Pour the above mixture into a ball mill, ball mill at 200 r / min for 5 h, and then take it out;

[0121] (6) The ball-milled material was vacuum-dried at 80° C. for 12 h and taken out after the pyridine was completely volatilized to obtain a positive electrode material with an inner layer coated with inorganic chloride and an outer layer coated with an organic polymer electrolyte.

[0122] Performance Testing

[0123] The positive electrode materials prepared in Examples 1 to 7 and Comparative Examples 1 to 4 were assembled into 2025 pairs of lithium half-cells for electrochemical performance testing. A 14 mm lithium sheet was used as the negative electrode; polyethylene was used as the separator; and a 1 M LiPF6 / EC:DMC:EMC (1:1:1) solution was used as the electrolyte. A battery test cabinet was used to conduct DC internal resistance, rate performance, and cycle performance tests at 25°C. The test voltage range was 2.8-4.3 V, the test rate was 0.1C-10C, and the nominal capacity was 200 mAh g. -1 ;The test results are shown in Table 1 below.

[0124] Table 1 Test results of Examples 1-7 and Comparative Examples 1-4

[0125]

[0126]

[0127] From the test results of Examples 1-7 and Comparative Examples 1-4 in Table 1 and the attached Figure 1-2 It can be seen that the present invention can significantly reduce the DC impedance of the battery, increase the first coulombic efficiency, and improve the rate performance by simultaneously in-situ synthesizing a single layer of organic and inorganic composite solid electrolytes on the surface of the positive electrode material matrix, compared with uncoated samples, single organic or inorganic electrolyte coatings, and double-layer composite electrolyte samples. Figure 1 As shown, the first coulombic efficiency of Example 1 is as high as 90.9%, which is significantly higher than that of Comparative Example 1 (79.3%). After 100 cycles at 1C, the capacity retention rate of Example 1 coated with the composite electrolyte is as high as 96.4%, while that of Comparative Example 1 is only 72.9%.

[0128] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A composite solid electrolyte coated modified positive electrode material, characterized in that: It includes a positive electrode material matrix and a layer of composite solid electrolyte coated on the surface of the positive electrode material matrix; The composite solid electrolyte comprises an organic polymer and an inorganic chloride; The structural general formula of the organic polymer is as follows: where 100 < n <1000000>0, and R1 and R2 are alkyl groups with a carbon chain length greater than or equal to 0 and less than 5. The inorganic chloride is Li3InCl6; The organic polymer and the inorganic chloride are synthesized synchronously on the surface of the positive electrode material matrix and are evenly distributed to form a single-layer composite solid electrolyte coating layer.

2. The composite solid electrolyte coated modified positive electrode material according to claim 1, characterized in that: The positive electrode material matrix includes any one of lithium iron phosphate, lithium cobaltate, lithium manganate, lithium nickelate, lithium nickel cobaltate, lithium nickel manganate, lithium nickel cobalt manganate, and lithium nickel cobalt aluminum oxide.

3. The composite solid electrolyte coated modified positive electrode material according to claim 1, characterized in that: The general structural formula of the organic polymer monomer is: Wherein R1 and R2 are alkyl groups with carbon chain lengths greater than or equal to 0 and less than 5.

4. A method for preparing a positive electrode material coated and modified with a composite solid electrolyte according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) Weighing a certain mass of positive electrode material matrix, organic monomer, LiCl, InCl3, and pyridine and mixing them to obtain a mixture; (2) pouring the above mixture into a ball mill and subjecting it to mechanical ball milling; (3) The ball-milled mixture is heat-treated in an inert atmosphere until the pyridine is completely volatilized, thereby obtaining a composite solid electrolyte-coated modified positive electrode material.

5. The preparation method according to claim 4, characterized in that In step (1), the mass ratio of the organic monomer to the positive electrode material matrix is ​​0.1-10:100, the mass ratio of LiCl to the positive electrode material matrix is ​​0.1-10:100, the mass ratio of InCl3 to the positive electrode material matrix is ​​0.1-10:100, the molar ratio of LiCl to InCl3 is 3:1, and the mass ratio of pyridine to the positive electrode material matrix is ​​0.5-5:

1.

6. The preparation method according to claim 4, characterized in that In step (2), the ball milling process has a rotation speed of 100-500 r / min and a duration of 2-10 h.

7. The preparation method according to claim 4, characterized in that In step (2), the following chemical reaction occurs to obtain an organic polymer and Li3InCl6·xH2O; The synthesis route of the organic polymer is to use LiCl as an initiator to initiate a cationic polymerization reaction of the organic monomer in a pyridine solution. The specific reaction equation is as follows: The synthesis route of Li3InCl6·xH2O is to use LiCl and InCl3 as reactants and the water released from the polymerization reaction of the above organic monomers as an intermediate reactant to synthesize the inorganic chloride precursor Li3InCl6·xH2O. The specific reaction equation is as follows:

8. The preparation method according to claim 7, characterized in that In step (3), the inorganic chloride precursor Li3InCl6·xH2O prepared in step (2) is heated and dehydrated to obtain inorganic chloride Li3InCl6. The specific reaction equation is as follows:

9. The preparation method according to claim 4, characterized in that In step (3), the heat treatment temperature is 120-500° C. and the duration is 2-5 hours.

10. A lithium ion battery, characterized in that: The invention comprises the composite solid electrolyte coated modified positive electrode material according to any one of claims 1 to 3 or the composite solid electrolyte coated modified positive electrode material obtained by the preparation method according to any one of claims 4 to 9.

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