Solid-state electrolyte material, preparation method therefor, and use thereof

Abstract

This invention relates to the field of lithium battery technology, and discloses a solid electrolyte material, its preparation method, and its application. The solid electrolyte material includes lithium titanium aluminum phosphate and rare earth oxides supported on the lithium titanium aluminum phosphate; wherein the chemical formula of the lithium titanium aluminum phosphate is Li. 1+x Al x Ti 2‑x (PO4)3, 0 < x < 1. Solid electrolyte materials obtained by modifying lithium titanium aluminum phosphate with rare earth oxides exhibit excellent ionic conductivity, meeting the ion-electron migration rate requirements of lithium-ion batteries. They also possess good high-temperature resistance and excellent chemical structural stability, improving the safety performance of lithium-ion batteries.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, specifically to a solid electrolyte material, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries, with their advantages of high output voltage, high energy density, long cycle life, good safety performance, and no memory effect, have been successfully applied as the main energy storage device in the field of mobile power supplies. To further meet the demands of grid energy storage, electric vehicles, and consumer electronics for energy storage devices, electrode materials with longer cycle life, better safety, and higher energy density, as well as lithium battery systems, have become research hotspots.

[0003] Lithium-ion batteries mainly consist of four parts: the positive electrode, the negative electrode, the separator, and the electrolyte. During operation, lithium ions shuttle between the positive and negative electrodes through the electrolyte. However, in currently commercially available lithium batteries, the electrolyte contains a flammable liquid organic electrolyte. When the liquid lithium-ion battery is subjected to severe impact or excessively high temperature, the electrolyte is highly flammable, causing battery fires and even more serious safety accidents. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems of poor safety performance, low energy density and poor cycle performance of lithium-ion batteries in the prior art, and to provide a solid electrolyte material, its preparation method and application.

[0005] To achieve the above objectives, a first aspect of the present invention provides a solid electrolyte material, the solid electrolyte material comprising lithium titanium aluminum phosphate and rare earth oxides supported on the lithium titanium aluminum phosphate;

[0006] The chemical formula of the lithium titanium aluminum phosphate is Li. 1+x Al x Ti 2-x (PO4)3, 0 < x < 1.

[0007] Preferably, the rare earth oxide is selected from one or more oxides of Sc, Ce, Y, Lu, Yb, Tm, Er, Ho, Tb, Gd, Sm, Pm, Nd and La.

[0008] Preferably, the content of the rare earth oxide is 0.5-7.5 parts by weight relative to 100 parts by weight of the lithium titanium aluminum phosphate.

[0009] A second aspect of the present invention provides a method for preparing the solid electrolyte material described above, the method comprising: mixing lithium aluminum titanium phosphate and a rare earth compound, ball milling the mixture, and then calcining it;

[0010] The chemical formula of the lithium titanium aluminum phosphate is Li. 1+x Al x Ti 2-x (PO4)3, 0 < x < 1.

[0011] Preferably, the weight ratio of lithium titanium aluminum phosphate to rare earth compound is 100:0.5-7.5;

[0012] Preferably, the ball-to-material ratio in the ball mill is 10-40:1;

[0013] Preferably, the calcination conditions include: a temperature of 300-1000℃ and a time of 5-12h.

[0014] A third aspect of the present invention provides a composite positive electrode sheet, the composite positive electrode sheet comprising a positive current collector, a positive electrode powder, and a solid electrolyte material;

[0015] The positive electrode powder contains a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder; the solid electrolyte material is the solid electrolyte material described above.

[0016] Preferably, the content of the solid electrolyte material is 2-8 parts by weight relative to 100 parts by weight of the positive electrode powder.

[0017] The fourth aspect of the present invention provides a method for preparing the composite positive electrode sheet described above, the method comprising: mixing positive electrode powder, solid electrolyte material and solvent to obtain a positive electrode slurry, coating the positive electrode slurry onto a positive electrode current collector, and then drying it.

[0018] A fifth aspect of the present invention provides a composite membrane comprising a composite layer, a ceramic layer, and a base film located between the composite layer and the ceramic layer;

[0019] The composite layer contains lithium fluoride and a solid electrolyte material, wherein the solid electrolyte material is the solid electrolyte material described above.

[0020] Preferably, the weight ratio of lithium fluoride to solid electrolyte material is 2-33:100.

[0021] The sixth aspect of the present invention provides a lithium-ion battery, the lithium-ion battery comprising a composite positive electrode, a negative electrode, a separator, and an electrolyte;

[0022] The composite positive electrode sheet is the composite positive electrode sheet described above.

[0023] Preferably, the diaphragm is the composite diaphragm described above.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. The solid electrolyte material of this invention includes lithium titanium aluminum phosphate and rare earth oxides supported on the lithium titanium aluminum phosphate. The solid electrolyte material obtained by modifying lithium titanium aluminum phosphate with rare earth oxides has excellent ionic conductivity, which can meet the ion electron migration rate of lithium-ion batteries. It also has good high-temperature resistance and excellent chemical structural stability, which can improve the safety performance of lithium-ion batteries.

[0026] 2. In traditional lithium-ion batteries, ion electron migration relies on the electrolyte. However, the electrolyte is highly susceptible to side reactions with the positive and negative electrode materials. During cycling, the electrolyte depletes rapidly with each cycle, leading to battery cycle failure. The solid-state electrolyte provided by this invention possesses excellent chemical structural stability. When applied to lithium-ion batteries, it continuously provides ion migration channels, improving battery cycle performance. Simultaneously, it reduces the amount of electrolyte required, mitigating the safety hazards posed by the electrolyte's flammability.

[0027] 3. This invention provides a lithium-ion battery, the positive electrode of which includes the solid electrolyte material described in this invention. The addition of the solid electrolyte material can replace part of the electrolyte, significantly reducing the weight of the lithium-ion battery while greatly improving its energy density. Preferably, combining the positive electrode with the solid electrolyte material with a composite separator also containing a solid electrolyte material can improve the compactness between the electrodes, greatly enhancing the cycle performance of the lithium-ion battery. Detailed Implementation

[0028] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0029] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0030] The first aspect of the present invention provides a solid electrolyte material, the solid electrolyte material comprising lithium titanium aluminum phosphate (LATP) and rare earth oxides supported on the lithium titanium aluminum phosphate;

[0031] The chemical formula of the lithium titanium aluminum phosphate is Li. 1+x Al x Ti 2-x (PO4)3, 0 < x < 1.

[0032] In this invention, lithium titanium aluminum phosphate material is modified by rare earth element oxides. The oxygen element in the rare earth oxides can inhibit the growth of lithium dendrites, solving the problems of poor compatibility with lithium metal and poor air stability. The rare earth elements in the rare earth oxides have unique electronic structures and functional properties, which can improve the ionic conductivity of LATP and reduce grain boundary impedance.

[0033] In the preferred case, 0.3 ≤ x ≤ 0.6; specifically, the value of x can be 0.3, 0.4, 0.5 or 0.6.

[0034] In a preferred embodiment, the rare earth oxide is selected from one or more oxides of Sc, Ce, Y, Lu, Yb, Tm, Er, Ho, Tb, Gd, Sm, Pm, Nd, and La.

[0035] In a preferred embodiment of the present invention, the content of the rare earth oxide is 0.5-7.5 parts by weight relative to 100 parts by weight of the lithium aluminum titanium phosphate. Following this preferred embodiment, the ionic conductivity and structural stability of the solid electrolyte material can be further improved.

[0036] A second aspect of the present invention provides a method for preparing the solid electrolyte material described above, the method comprising: mixing lithium aluminum titanium phosphate and a rare earth compound, ball milling the mixture, and then calcining it;

[0037] The chemical formula of the lithium titanium aluminum phosphate is Li. 1+x Al x Ti 2-x (PO4)3, 0 < x < 1.

[0038] In the preferred case, 0.3 ≤ x ≤ 0.6; specifically, the value of x can be 0.3, 0.4, 0.5 or 0.6.

[0039] In this invention, the rare earth compound can be a rare earth salt, rare earth sulfide, or rare earth oxide commonly found in the art, preferably a rare earth oxide. For example, it can be Sc2O3, Ce2O3, or Y2O3.

[0040] More preferably, the weight ratio of lithium titanium aluminum phosphate to rare earth compound is 100:0.5-7.5; specifically, it can be 100:0.5, 100:1, 100:2, 100:3, 100:4, 100:5, 100:6, 100:7 or 100:7.5.

[0041] In a preferred embodiment, the rare earth compound is selected from one or more compounds of Sc, Ce, Y, Lu, Yb, Tm, Er, Ho, Tb, Gd, Sm, Pm, Nd, and La.

[0042] In this invention, the ball milling can be carried out in a zirconia ball mill jar. Preferably, the ball-to-material ratio during ball milling, i.e., the weight ratio of zirconia to material, can be 10-40:1; specifically, it can be 10:1, 15:1, 20:1, 25:1, 30:1, 35:1, or 40:1.

[0043] In a preferred embodiment, the ball milling conditions include: a rotation speed of 300-700 r / min and a time of 10-30 h; specifically, the ball milling speed can be 300 r / min, 400 r / min, 500 r / min, 600 r / min or 700 r / min; and the ball milling time can be 10 h, 12 h, 14 h, 15 h, 17 h, 18 h, 20 h, 25 h or 30 h.

[0044] In this invention, the calcination can be carried out in conventional heat treatment equipment in the art, such as in a muffle furnace.

[0045] Preferably, the calcination conditions include: a temperature of 300-1000℃ and a time of 5-12 hours; specifically, the calcination temperature can be 300℃, 400℃, 500℃, 600℃, 700℃, 800℃, 900℃, or 1000℃, and the calcination time can be 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, or 12 hours. The heating rate during the calcination process can be 0.5-5℃ / min.

[0046] According to some preferred embodiments of the present invention, the method for preparing solid electrolyte materials includes the following steps:

[0047] (1) Add lithium titanium aluminum phosphate and rare earth oxides into a zirconia ball mill jar, and then fix the sealed zirconia ball mill jar on a high-energy planetary ball mill for ball milling to obtain a mixture;

[0048] (2) The mixture is pressed into tablets and then transferred to a muffle furnace for roasting. The roasted material is then ground.

[0049] A third aspect of this invention provides a composite positive electrode sheet, comprising a positive current collector, positive electrode powder, and a solid electrolyte material; wherein the positive electrode powder contains a positive active material, a positive conductive agent, and a positive binder; and the solid electrolyte material is the solid electrolyte material described above. Using this composite positive electrode sheet, the electrolyte injection volume of lithium-ion batteries can be reduced. By assembling it with a negative electrode sheet into a cylindrical battery, a high-safety, long-cycle, high-energy-density semi-solid-state lithium-ion cylindrical battery can be manufactured.

[0050] Preferably, the positive electrode powder and solid electrolyte material are loaded on the surface of the positive electrode current collector.

[0051] In this invention, the positive electrode powder is a material loaded on the positive electrode current collector in a conventional positive electrode sheet. Typically, the positive electrode powder contains at least a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder. Preferably, the positive electrode powder may also contain positive electrode additives.

[0052] In a preferred embodiment, the content of the solid electrolyte material is 2-8 parts by weight relative to 100 parts by weight of the positive electrode powder. According to this preferred method, applying the solid electrolyte material to a lithium-ion battery can further improve the energy density and cycle performance of the lithium-ion battery, while reducing the amount of electrolyte injected, thereby improving the safety performance of the lithium-ion battery.

[0053] According to some preferred embodiments of the present invention, the thickness of the positive current collector is 12-20 μm.

[0054] In this invention, the positive electrode active material can be any of the various positive electrode materials conventionally used in the art. According to some specific embodiments of the invention, the positive electrode material can be selected from one or more of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, and lithium nickel cobalt manganese oxide. The positive electrode conductive agent can be any of the various positive electrode conductive agents conventionally used in the art. According to some specific embodiments of the invention, the positive electrode conductive agent can be selected from one or more of conductive carbon black, carbon fiber, acetylene black, Ketjen black, graphene, and carbon nanotubes. The positive electrode binder can be any of the various positive electrode binders conventionally used in the art. According to some specific embodiments of the invention, the positive electrode binder can be selected from one or more of polypropylene, polyethylene, polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene, polytetrafluoroethylene, and polyhexafluoropropylene. The positive electrode additive can be selected from lithium carbonate and / or oxalic acid. Furthermore, the content of each component in the positive electrode powder can be set according to conventional methods in the art.

[0055] The fourth aspect of the present invention provides a method for preparing the composite positive electrode sheet described above, the method comprising: mixing positive electrode powder, solid electrolyte material and solvent to obtain a positive electrode slurry, coating the positive electrode slurry onto a positive electrode current collector, and then drying it.

[0056] In this invention, the solvent used in preparing the composite positive electrode sheet can be any solvent conventionally used in the art, such as N-methylpyrrolidone. There are no special requirements for the drying conditions during the preparation of the composite positive electrode sheet; drying can be carried out according to conventional conditions in the art.

[0057] A fifth aspect of the present invention provides a composite membrane comprising a composite layer, a ceramic layer, and a base film located between the composite layer and the ceramic layer;

[0058] The composite layer contains lithium fluoride and a solid electrolyte material, wherein the solid electrolyte material is the solid electrolyte material described above.

[0059] In this invention, based on the excellent compatibility between lithium fluoride and LATP, after modifying the solid electrolyte material and lithium fluoride onto the surface of the base film, lithium ions can be transported through grain boundaries formed by lithium fluoride and LATP, giving the lithium battery excellent ion transport performance. Traditional separators tend to shrink or close pores above 150°C, leading to internal short circuits or failures in lithium batteries. However, the composite separator containing the solid electrolyte material described in this invention has high-temperature resistance, avoiding the risks of shrinkage, pore closing, or even fire during overcharging or short circuits, greatly improving the safety performance of lithium batteries. Simultaneously, the presence of the solid electrolyte promotes the formation of a high-quality positive electrode / electrolyte film, stabilizing the interface between the positive electrode and the composite separator, maintaining structural stability during long-term cycling, and ultimately improving the cycle performance of lithium batteries.

[0060] In a preferred embodiment, the weight ratio of lithium fluoride to solid electrolyte material in the composite layer can be 2-33:100; specifically, it can be 2:100, 3:100, 5:100, 10:100, 15:100, 20:100, 25:100, 30:100 or 33:100.

[0061] In a preferred embodiment, the thickness of the composite layer can be 2-5 μm.

[0062] In this invention, the base film can be a separator conventionally used in lithium-ion batteries. In a specific embodiment, the base film can be a polypropylene (PP) / polyethylene (PE) / polypropylene three-layer composite film.

[0063] In a preferred embodiment, the ceramic layer may be an alumina ceramic layer.

[0064] In this invention, the composite membrane can be prepared according to the following steps: a solid electrolyte material, lithium fluoride, and solvent A are mixed to obtain slurry A; ceramic powder is mixed with solvent B to obtain slurry B; slurry A and slurry B are coated onto both sides of a base membrane using a double-sided coating method; then, the coating is evaporated and dried at room temperature (20-30°C), followed by drying in a vacuum drying oven at 50-70°C. Solvent A and solvent B are both conventionally used solvents in the art; for example, solvent A can be N,N-dimethylformamide and / or acetone, and solvent B can be acetone and / or N-methylpyrrolidone.

[0065] The sixth aspect of the present invention provides a lithium-ion battery, the lithium-ion battery comprising a composite positive electrode, a negative electrode, a separator, and an electrolyte;

[0066] The composite positive electrode sheet is the composite positive electrode sheet described above.

[0067] In this invention, the negative electrode sheet can be a negative electrode sheet conventionally used in the art. According to some specific embodiments of the present invention, the negative electrode sheet includes a negative electrode current collector and a negative electrode powder loaded on the surface of the negative electrode current collector, wherein the negative electrode powder contains a negative electrode active material, a negative electrode conductive agent, and a negative electrode binder.

[0068] In this invention, the electrolyte can be any electrolyte conventionally used in the art. According to some specific embodiments of the invention, the electrolyte is obtained by mixing a lithium salt, an electrolyte solvent, and additives.

[0069] In this invention, the lithium-ion battery can be a cylindrical battery. Cylindrical batteries can be manufactured in accordance with conventional methods in the art. For example, the process of manufacturing a lithium-ion cylindrical battery includes the following steps: winding, assembling, and injecting an electrolyte into a composite positive electrode, a negative electrode, and a separator.

[0070] In a preferred embodiment, the separator is the composite separator described above. By combining the composite separator with the composite positive electrode, the amount of electrolyte injected can be significantly reduced, the weight of the lithium-ion battery can be lightened, and the specific energy of the lithium-ion battery can be increased. Simultaneously, the energy density, cycle performance, and safety performance of the lithium-ion battery can be improved. Specifically, when the separator is the composite separator described in this invention, during battery assembly, the composite layer in the composite separator is positioned facing the negative electrode.

[0071] The present invention will be described in detail below through embodiments, but the scope of protection of the present invention is not limited thereto.

[0072] Unless otherwise specified, all reagents used in the following examples and comparative examples are commercially available products.

[0073] Example 1

[0074] The components of a lithium-ion battery include: a composite positive electrode, a negative electrode, an electrolyte, and a composite separator M1.

[0075] Composite positive electrode sheet: composed of positive current collector (15um thick), positive electrode powder and solid electrolyte material L1;

[0076] The positive electrode powder is composed of positive electrode active material (lithium nickel cobalt aluminum oxide), positive electrode conductive agent (single-walled CNTs and carbon black Super-P), positive electrode binder (PVDF binder), and positive electrode additive (lithium carbonate); with a total weight of 100 wt% of the positive electrode powder, the content of the positive electrode active material is 97.3 wt%, the content of the positive electrode conductive agent is 1.5 wt% (of which, the content of single-walled CNTs is 1 wt% and the content of carbon black Super-P is 0.5 wt%), the content of the positive electrode binder is 1 wt%, and the content of the positive electrode additive is 0.2 wt%; relative to 100 parts by weight of the positive electrode powder, the content of the solid electrolyte material is 3 parts by weight.

[0077] The preparation process of the composite positive electrode sheet is as follows: positive electrode powder, solid electrolyte material L1 and solvent (N-methylpyrrolidone) are mixed to obtain positive electrode slurry, the positive electrode slurry is coated on the positive electrode current collector and then dried.

[0078] The solid electrolyte material L1 includes lithium titanium aluminum phosphate (Li1). 1.3 Al 0.3 Ti 1.7 (PO4)3 and rare earth oxide (Sc2O3) supported on the lithium titanium aluminum phosphate, wherein the content of the rare earth oxide is 1.5 parts by weight relative to 100 parts by weight of the lithium titanium aluminum phosphate.

[0079] The preparation process of the solid electrolyte material L1 is as follows:

[0080] (1) Lithium aluminum titanium phosphate (chemical formula Li) 1.3 Al 0.3 Ti 1.7 (PO4)3) and rare earth compound (Sc2O3) were added to a zirconia ball mill jar with a ball-to-material ratio of 30:1. The sealed zirconia ball mill jar was then fixed on a high-energy planetary ball mill for ball milling at a speed of 550 r / min for 17 h to obtain a mixture. The weight ratio of lithium titanium aluminum phosphate to rare earth compound was 100:1.5.

[0081] (2) Compress the mixture into tablets and then transfer it to a muffle furnace. Then heat the muffle furnace to 550°C at a rate of 0.5°C / min and calcine it at 550°C for 7 hours. After cooling to room temperature, grind the calcined material for 15 minutes.

[0082] Negative electrode sheet: composed of negative electrode current collector and negative electrode powder; wherein, the negative electrode powder is composed of negative electrode active material (graphite), negative electrode conductive agent (carbon black Super-P) and negative electrode binder (purchased from Shenzhen Yanyi New Material Technology Co., Ltd., model is Sone-P44S);

[0083] The total weight of the negative electrode powder is 100wt%, the content of the negative electrode active material is 96wt%, the content of the negative electrode conductive agent is 1.5wt%, and the content of the negative electrode binder is 2.5wt%.

[0084] Composite membrane M1: It consists of a composite layer (thickness of 3 μm), an alumina ceramic layer, and a base film located between the composite layer and the alumina ceramic layer;

[0085] The composite layer contains lithium fluoride and solid electrolyte material L1 in a weight ratio of 11:100; the base film is a three-layer composite film of polypropylene (PP) / polyethylene (PE) / polypropylene (PP).

[0086] The composite membrane M1 is prepared according to the following steps: solid electrolyte material L1, lithium fluoride and solvent A are mixed to obtain slurry A, alumina ceramic powder is mixed with solvent B to obtain slurry B, slurry A and slurry B are coated onto both sides of the base membrane by double-sided coating, then evaporated and dried at room temperature (25°C), and then placed in a vacuum drying oven at 60°C for drying.

[0087] Electrolyte: A composite electrolyte consisting of lithium salt, solvent, and additives, with a dosage of 3g.

[0088] Example 2

[0089] The method described in Example 1 is implemented, except that in the composite positive electrode sheet, the content of the solid electrolyte material is 1.3 parts by weight relative to 100 parts by weight of positive electrode powder, and the liquid injection amount is changed to 4g.

[0090] Example 3

[0091] The method described in Example 1 is implemented, except that in the composite positive electrode sheet, the content of the solid electrolyte material is 10 parts by weight relative to 100 parts by weight of positive electrode powder.

[0092] Example 4

[0093] The method described in Example 1 is implemented, except that in the composite positive electrode sheet, the content of the solid electrolyte material is 4.5 parts by weight relative to 100 parts by weight of positive electrode powder.

[0094] Example 5

[0095] The method described in Example 1 is implemented, except that the composite diaphragm is replaced with a diaphragm coated with alumina ceramic on both sides. That is, the diaphragm is formed by coating alumina ceramic on both sides of a base film, and the base film is a three-layer composite film of polypropylene (PP) / polyethylene (PE) / polypropylene (PP).

[0096] Example 6

[0097] The method described in Example 1 is implemented, except that in the composite positive electrode and the composite separator, the same amount of solid electrolyte material L2 is used instead of solid electrolyte material L1.

[0098] The solid electrolyte material L2 includes lithium titanium aluminum phosphate Li. 1.3 Al 0.3 Ti 1.7 (PO4)3 and rare earth oxide (Ce2O3) supported on the lithium titanium aluminum phosphate, wherein the content of the rare earth oxide is 1 part by weight relative to 100 parts by weight of the lithium titanium aluminum phosphate.

[0099] The preparation process of the solid electrolyte material L2 is as follows:

[0100] (1) Lithium aluminum titanium phosphate (chemical formula Li) 1.3 Al 0.3 Ti 1.7 (PO4)3) and rare earth compound (Ce2O3) were added to a zirconia ball mill jar with a ball-to-material ratio of 30:1. The sealed zirconia ball mill jar was then fixed on a high-energy planetary ball mill for ball milling at a speed of 550 r / min for 17 h to obtain a mixture. The weight ratio of lithium titanium aluminum phosphate to rare earth compound (calculated as rare earth element) was 100:1.

[0101] (2) Compress the mixture into tablets and then transfer it to a muffle furnace. Then heat the muffle furnace to 550°C at a rate of 0.5°C / min and calcine it at 550°C for 7 hours. After cooling to room temperature, grind the calcined material for 15 minutes.

[0102] Example 7

[0103] The method described in Example 4 is implemented, except that in the composite positive electrode and the composite separator, the same amount of solid electrolyte material L3 is used instead of solid electrolyte material L1.

[0104] The solid electrolyte material L3 includes lithium titanium aluminum phosphate (Li3). 1.3 Al 0.3 Ti 1.7 (PO4)3 and rare earth oxide (Y2O3) supported on the lithium titanium aluminum phosphate, wherein the content of the rare earth oxide is 2 parts by weight relative to 100 parts by weight of the lithium titanium aluminum phosphate.

[0105] The preparation process of the solid electrolyte material L3 is as follows:

[0106] (1) Lithium aluminum titanium phosphate (chemical formula Li)1.3 Al 0.3 Ti 1.7 (PO4)3) and rare earth compound (Y2O3) were added to a zirconia ball mill jar with a ball-to-material ratio of 30:1. The sealed zirconia ball mill jar was then fixed on a high-energy planetary ball mill for ball milling at a speed of 550 r / min for 17 h to obtain a mixture. The weight ratio of lithium titanium aluminum phosphate to rare earth compound (calculated as rare earth element) was 100:2.

[0107] (2) Compress the mixture into tablets and then transfer it to a muffle furnace. Then heat the muffle furnace to 550°C at a rate of 0.5°C / min and calcine it at 550°C for 7 hours. After cooling to room temperature, grind the calcined material for 15 minutes.

[0108] Comparative Example 1

[0109] The method described in Example 1 was implemented, except that the solid electrolyte material L1 was not used in the composite positive electrode, the composite separator was replaced with a separator coated with alumina ceramic on both sides, and the liquid injection volume was adjusted to 5.6g.

[0110] Comparative Example 2

[0111] The method described in Example 1 is implemented, except that the solid electrolyte material L1 in the composite positive electrode is replaced with the same amount of lithium titanium aluminum phosphate, and the separator is replaced with a separator coated with alumina ceramic on both sides.

[0112] Test Example 1

[0113] The energy density, cycle performance, and safety performance (overcharge, short circuit, heavy object impact) of the lithium-ion batteries in the examples and comparative examples were tested.

[0114] The energy density test method is as follows: the battery is discharged at a constant current of 0.2C to 2.5V and left to stand for 30 minutes; then charged at a constant current and constant voltage of 0.2C to 4.2V, with a cutoff current of 0.02C; left to stand for 30 minutes; and finally discharged at a constant current of 0.2C to 2.5V to obtain the capacity C. Energy density = C * V / M, where V is the battery discharge plateau voltage and M is the battery mass.

[0115] Safety performance is conducted in accordance with Part 5 of the UL1642 lithium battery safety standard, Parts 6, 7, and 8 of GB 31241-2014 Safety Requirements for Lithium-ion Batteries and Battery Packs for Portable Electronic Products, and the methods described in Section 38.3 of UN38.3:Rev.6, "Handling Specifications for Rechargeable Lithium Batteries," Part 3.

[0116] The test results are shown in Table 1.

[0117] Table 1

[0118]

[0119]

[0120] As shown in Table 1, applying the solid electrolyte material described in this invention to lithium-ion batteries can improve the energy density, cycle performance, and safety performance of lithium-ion batteries.

[0121] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A lithium-ion battery, characterized in that, The lithium-ion battery includes a composite positive electrode, a negative electrode, a separator, and an electrolyte; The composite positive electrode sheet includes a positive current collector, positive electrode powder, and solid electrolyte material; wherein, the positive electrode powder contains a positive active material, a positive conductive agent, and a positive binder; relative to 100 parts by weight of the positive electrode powder, the content of the solid electrolyte material is 2-8 parts by weight. The separator includes a composite layer, a ceramic layer, and a base film located between the composite layer and the ceramic layer; the composite layer contains lithium fluoride and a solid electrolyte material, with a weight ratio of lithium fluoride to solid electrolyte material of 11-33:100; the composite layer in the composite separator is disposed towards the negative electrode plate; The solid electrolyte material includes lithium titanium aluminum phosphate and rare earth oxides supported on the lithium titanium aluminum phosphate; wherein the chemical formula of the lithium titanium aluminum phosphate is Li. 1+x Al x Ti 2-x (PO4)3, 0.3≤x≤0.6, wherein the rare earth oxide is selected from oxides of Sc; the content of the rare earth oxide is 0.5-7.5 parts by weight relative to 100 parts by weight of the lithium titanium aluminum phosphate; The method for preparing the solid electrolyte material includes: mixing lithium titanium aluminum phosphate and rare earth compounds, then ball milling them, and then calcining them; the ball-to-material ratio for ball milling is 10-40:

1.

2. The lithium-ion battery according to claim 1, characterized in that, The roasting conditions include a temperature of 300-1000℃ and a time of 5-12 hours.

3. The lithium-ion battery according to claim 1, characterized in that, The method for preparing the composite positive electrode sheet includes: mixing positive electrode powder, solid electrolyte material and solvent to obtain positive electrode slurry, coating the positive electrode slurry onto a positive electrode current collector, and then drying it.

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