WO2021254220A1 - Composite solid-state electrolyte material and preparation method therefor, lithium secondary battery, and terminal - Google Patents

Abstract

Embodiments of the present application provide a composite solid-state electrolyte material, comprising an inorganic solid-state electrolyte body and a coating layer that completely coats the outer surface of the inorganic solid-state electrolyte body. The material of the coating layer is an insulating polymer, and the thickness of the coating layer is less than or equal to 20 nm. The coating layer of the composite solid-state electrolyte material can block electrons from being transported from a negative electrode to the interior of the inorganic solid-state electrolyte body, thereby effectively inhibiting the growth and diffusion of a lithium dendrite, improving the short circuit of a battery caused by the lithium dendrite, and improving the safety of the battery. The embodiments of the present application further provide a preparation method for the composite solid-state electrolyte material, a lithium secondary battery, and a terminal.

Description

Composite solid electrolyte material and preparation method thereof, lithium secondary battery and terminal

This application claims the priority of the Chinese patent application filed with the Chinese Patent Office on June 16, 2020, the application number is 202010550904.7, and the application name is "composite solid electrolyte material and its preparation method, lithium secondary battery and terminal", all of which The content is incorporated in this application by reference.

Technical field

This application relates to the field of battery technology, in particular to a composite solid electrolyte material and a preparation method thereof, a lithium secondary battery and a terminal.

Background technique

Metal lithium is considered to be the ultimate negative electrode of lithium secondary batteries due to its extremely high theoretical specific capacity and extremely low electrochemical potential. At present, commercial lithium batteries generally use liquid electrolytes. Due to their active chemical properties, the metal lithium anode is prone to side reactions with the liquid electrolyte, and lithium dendrites are prone to grow at the interface, causing safety problems such as short circuit and thermal runaway of the battery, which hinder high The development process of energy density lithium metal batteries. The all-solid-state lithium battery made by replacing the liquid electrolyte with a non-flammable solid-state electrolyte (SE) with a higher elastic modulus is expected to fundamentally solve this safety problem and inhibit the growth of lithium dendrites.

Solid-state electrolyte is the core of all-solid-state lithium batteries. Common solid-state electrolytes include polymer and inorganic types. Among them, inorganic solid-state electrolytes have attracted wide attention due to their high ionic conductivity and lithium ion migration number close to 1mS/cm. . However, the non-ideal behavior of lithium ions at the interface of the inorganic electrolyte will still cause the growth of lithium dendrites. In severe cases, the lithium dendrites may even pass through the inorganic solid electrolyte, causing problems such as battery short circuits.

Summary of the invention

In view of this, the embodiments of the present application provide a composite solid electrolyte material. By coating the surface of the inorganic solid electrolyte body with a coating layer of insulating polymer, the coating layer can block electrons from being transferred from the negative electrode to the inside of the inorganic solid electrolyte body. , In order to solve the battery short circuit problem caused by the growth of lithium dendrites and entering the electrolyte in the prior art.

Specifically, the first aspect of the embodiments of the present application provides a composite solid electrolyte material, including an inorganic solid electrolyte body and a coating layer that completely covers the outer surface of the inorganic solid electrolyte body. The material of the coating layer is insulating. Polymer, the thickness of the coating layer is less than or equal to 20 nm.

In the embodiment of the present application, the thickness of the coating layer is 5 nm-20 nm. The coating layer with this thickness can not only effectively block electrons from entering the inside of the inorganic solid electrolyte body from the negative electrode end during the charging and discharging process of the lithium secondary battery, but also has little effect on the high ionic conductivity characteristics of the inorganic solid electrolyte body.

In the embodiment of the present application, the coating layer also completely covers the inner wall of the pore that communicates with the outside of the inorganic solid electrolyte body. At this time, the coating degree of the coating layer is extremely high, which can completely block the electrons from the negative electrode to the inside of the inorganic solid electrolyte body, and better avoid the growth of lithium dendrites.

In the embodiment of the present application, the electronic conductivity of the coating layer is less than or equal to 10 ^-12 S·cm ^-1 . The coating layer has higher insulation and can better block the transmission of electrons.

In the embodiment of the present application, the ionic conductivity of the composite solid electrolyte material at room temperature is above 10 ^-6 S·cm ^-1 . After the outer surface of the inorganic solid electrolyte body is covered by the coating layer, the ionic conductivity of the obtained composite solid electrolyte material is not affected.

In the embodiment of the present application, in the composite solid electrolyte material, the insulating polymer accounts for 0.1% to 2% by weight. This quality can ensure that the thickness of the coating layer is thinner and the coating integrity is high.

In the embodiment of the application, the insulating polymer is selected from polyolefin, polyacrylic acid, polyacrylate, polyimide, polyvinylpyrrolidone, polyethylene terephthalate, polyurethane, parylene, and At least one of derivatives and copolymers.

In the embodiment of the present application, the molecular weight of the insulating polymer is 5,000 to 500,000. The insulating polymer with a molecular weight in this range is more helpful for forming the above-mentioned coating layer with uniform film formation and high coating integrity.

In the embodiment of the present application, the parylene and its derivatives include at least one of Parylene N, Parylene C, Parylene D, Parylene F, and Parylene HT. The coating layer made of parylene or its derivatives has a high degree of adhesion to the body of the inorganic solid electrolyte body, and can be conformed to the surface of various shapes, and the formed coating layer has a uniform thickness, good continuity and compactness No pinholes.

In the embodiment of the present application, the degree of branching of the polyolefin is 40-150 branches/1000 main chain carbons, and the branched groups of the polyolefin include branches or branches with carbon atoms of 1-6. Alkyl. The above-mentioned branched polyolefin can ensure that the formed coating layer has a high degree of spreading and strong anchoring effect on the body of the inorganic electrolyte, and the above-mentioned branched chain group does not contain unsaturated bonds, so that the chemical properties of the polyolefin are stable , Resistance to oxidation.

In the embodiment of the present application, the inorganic solid electrolyte body is an inorganic solid electrolyte sheet or inorganic solid electrolyte particles.

In the embodiment of the present application, the material of the inorganic solid electrolyte body includes at least one of an oxide-type solid electrolyte and a sulfide-type solid electrolyte.

The composite solid electrolyte material provided by the first aspect of the embodiments of the present application has a coating layer that can completely cover the outer surface of the inorganic solid electrolyte body by providing a coating layer on the surface of the inorganic solid electrolyte body. The coating layer has a suitable thickness and can be used in lithium secondary batteries. In the process of charging and discharging, it prevents electrons from passing from the negative electrode to the inside of the inorganic solid electrolyte body with a certain electronic conductivity, without affecting the ionic conductivity characteristics of the inorganic solid electrolyte body, thereby effectively inhibiting the growth and diffusion of lithium dendrites and improving The battery short circuit caused by lithium dendrites improves battery safety.

Correspondingly, the second aspect of the embodiments of the present application provides a method for preparing a composite solid electrolyte material, including:

The inorganic solid electrolyte body is coated with an insulating polymer to form a coating layer that completely covers the outer surface of the inorganic solid electrolyte body to obtain a composite solid electrolyte material; wherein the thickness of the coating layer is less than or equal to 20 nm.

In one embodiment of the present application, the inorganic solid electrolyte body is an inorganic solid electrolyte sheet, and the inorganic solid electrolyte sheet is composed of a plurality of inorganic solid electrolyte particles through cold pressing, hot pressing, casting, or bonding. Calcination method of the agent.

In another embodiment of the present application, the inorganic solid electrolyte body is inorganic solid electrolyte particles.

In another embodiment of the present application, the preparation method further includes: pressing a plurality of inorganic solid electrolyte particles coated with the insulating polymer on the outer surface to form a sheet-shaped combination.

In the embodiment of the application, the insulating polymer is selected from polyolefin, polyacrylic acid, polyacrylate, polyimide, polyvinylpyrrolidone, polyethylene terephthalate, polyurethane, parylene, and At least one of derivatives and copolymers.

In the embodiment of the present application, the coating layer is formed by coating, chemical vapor deposition, vapor deposition or sputtering.

In the embodiment of the present application, the coating method includes at least one of drip coating, brush coating, spray coating, dipping, knife coating, and spin coating.

In the embodiment of the present application, the coating solution used for coating includes the insulating polymer and an organic solvent, wherein the mass ratio of the insulating polymer to the organic solvent is 1:5-100.

In the embodiment of the present application, the insulating polymer is parylene or its derivatives, and the coating layer is formed by chemical vapor deposition; during the deposition process, the deposition rate is less than or equal to

The deposition time is 250s-1000s.

The preparation method of the composite solid electrolyte material provided in the second aspect of the embodiments of the present application has a simple process, easy control, and large-scale production.

The third aspect of the embodiments of the present application provides a lithium secondary battery, including a positive electrode, a negative electrode, and a solid electrolyte located between the positive electrode and the negative electrode. The solid electrolyte includes On the one hand, the composite solid electrolyte material. The lithium secondary battery has better rate performance, cycle stability and safety.

In the embodiment of the present application, the negative electrode is a lithium negative electrode, the lithium negative electrode includes metallic lithium or a lithium alloy, and the lithium alloy includes at least one of a lithium silicon alloy, a lithium aluminum alloy, a lithium tin alloy, and a lithium indium alloy.

A third aspect of the embodiments of the present application provides a terminal, including a housing, and a motherboard and a battery located inside the housing. The battery includes the lithium secondary battery as described in the third aspect of the embodiments of the application, and the lithium secondary battery The secondary battery is used to power the terminal.

Description of the drawings

FIG. 1 is a schematic diagram of the structure of a composite solid electrolyte material provided by an embodiment of the application;

2 is a schematic structural diagram of a composite solid electrolyte material provided by another embodiment of the application;

FIG. 3 is a schematic structural diagram of a composite solid electrolyte material provided by another embodiment of this application;

4 is a schematic structural diagram of a lithium secondary battery provided by an embodiment of the application;

FIG. 5 is a schematic structural diagram of a terminal provided by an embodiment of this application.

detailed description

The embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application.

The embodiments of the present application provide a composite solid electrolyte material that can be used in a lithium secondary battery, effectively inhibiting the growth of lithium dendrites at the interface between the negative electrode and the electrolyte, and improving the battery short-circuit problem caused by the lithium dendrites. Specifically, the composite solid electrolyte material provided by the embodiments of the present application includes an inorganic solid electrolyte body and a coating layer that completely covers the outer surface of the inorganic solid electrolyte body. The material of the coating layer is an insulating polymer, and the thickness of the coating layer is Less than or equal to 20nm.

The insulating and high-coating coating layer can block the electrons from the negative electrode to the inside of the inorganic solid electrolyte body, thereby effectively inhibiting the growth and diffusion of lithium dendrites, improving battery short circuit caused by lithium dendrites, and improving battery safety; in addition; The thickness of the coating layer is appropriate, and lithium ions have a certain free path that can diffuse in the coating layer, and can migrate in a thinner coating layer without affecting the original performance of the inorganic solid electrolyte body.

In the embodiment of the present application, the electronic conductivity of the coating layer may be less than or equal to 10 ^-12 S·cm ^-1 . Further, the electronic conductivity of the coating layer may be 10 ^-12 -10 ^-22 S·cm ^-1 .

In the present application, after the outer surface of the inorganic solid electrolyte body is covered by the above-mentioned coating layer, the ionic conductivity of the obtained composite solid electrolyte material is not affected. In the embodiment of the present application, the ion conductivity of the composite solid electrolyte material at room temperature is above 10 ^-6 S·cm ^-1 , for example, 10 ^-6 S·cm ^-1 -10 ^-2 S·cm ^-1 .

In this application, the form of the inorganic solid electrolyte body is not limited, and it may be granular, flake, etc. 1 and 2, in some embodiments of the present application, the inorganic solid electrolyte body is specifically an inorganic solid electrolyte sheet.

As shown in FIG. 1, in a specific embodiment of the present application, the composite solid electrolyte material 10 includes an inorganic solid electrolyte sheet 11 and a coating layer 2 made of insulating polymer, wherein the coating layer 2 completely covers the inorganic solid electrolyte On the outer surface of the sheet 11, the inorganic solid electrolyte sheet 11 may be a sheet-shaped combination composed of a plurality of inorganic solid electrolyte particles.

Further, the thickness of the inorganic solid electrolyte sheet 11 may be 50 nm-500 μm. The thickness of the composite solid electrolyte material 10 may be 52 nm-501 μm, and further may be 55 nm-500 μm.

In the embodiment of the present application, the coating layer 2 completely covers all the outer surfaces of the inorganic solid electrolyte sheet 11 and the inner walls of the pores communicating with the outside (see FIG. 1), so as to ensure that the coating layer 2 can completely block electrons from the negative electrode. Into the inside of the inorganic solid electrolyte sheet 11 to avoid the growth of lithium dendrites. The "pores" here can include gaps, holes, and so on.

As shown in FIG. 2, in another specific embodiment of the present application, the composite solid electrolyte material 10 includes an inorganic solid electrolyte sheet and a coating layer 2 made of insulating polymer. The outer surface of the inorganic solid electrolyte sheet is coated with a coating layer. 2 Completely coated, where the inorganic solid electrolyte sheet is a sheet-shaped combination composed of a plurality of inorganic solid electrolyte particles 12, and the surface of each inorganic solid electrolyte particle 12 is coated with an insulating polymer.

The sheet-like composite solid electrolyte material 10 shown in FIG. 1 or FIG. 2 can be used directly as a solid electrolyte of a lithium secondary battery, and is arranged between the positive electrode and the negative electrode of the lithium secondary battery. Compared with FIG. 1, the insulating polymer in FIG. 2 has a higher degree of coating, and the insulating polymer also exists inside the inorganic solid electrolyte sheet, so that the insulating polymer has a stronger ability to block electrons.

In order to better inhibit the growth and diffusion of lithium dendrites, without affecting the effective transmission of lithium ions in the inorganic solid electrolyte body, and ensuring that the composite electrolyte material 10 has a higher lithium ion conductivity, the coating layer 2 in Figure 1 The thickness of the coating layer 2 on the outer surface of the composite solid electrolyte material 10 in FIG. 2 and the thickness of the insulating polymer on the outer surface of the inorganic solid electrolyte particles 12 in FIG. Scope. Further, in FIG. 2, the thickness of the composite solid electrolyte material 10 may be 0.1 μm-600 μm. For example, it is 0.1 μm-501 μm.

In the embodiment of the present application, in the composite solid electrolyte material 10, the mass of the insulating polymer accounts for 0.1% to 2% of the mass of the composite solid electrolyte material 10, which is relatively low, and can also ensure that a dense and suitable thickness package is formed. Cladding 2. For example, in FIG. 1, the mass proportion of the insulating polymer in the composite solid electrolyte material 10 may be 0.1%-0.5%. In FIG. 2, the mass proportion of the insulating polymer in the composite solid electrolyte material 10 may be 0.1%-2%, for example, 0.2%-2%.

The inorganic solid electrolyte sheet in FIG. 1 or FIG. 2 may be composed of a plurality of inorganic solid electrolyte particles 12 of the same material, or may be composed of a simple mixture of a plurality of inorganic solid electrolyte particles 12 of different materials, or It is composed of composite particles composed of a variety of inorganic solid electrolyte particles. Of course, in other embodiments of the present application, the above-mentioned inorganic solid electrolyte sheet may also be composed of inorganic solid electrolyte particles 12, a conductive agent, a binder, and the like.

Referring to FIG. 3, in another specific embodiment of the present application, the inorganic solid electrolyte body is specifically inorganic solid electrolyte particles. As shown in FIG. 3, the composite solid electrolyte material 10 includes inorganic solid electrolyte particles 12 and a coating layer 2 made of insulating polymer. The outer surface of the inorganic solid electrolyte particles 12 is completely covered by the coating layer 2. When the composite solid electrolyte material 10 shown in FIG. 3 is applied to a lithium secondary battery, a plurality of inorganic solid electrolyte particles 12 whose outer surfaces are covered with a coating layer 2 can be pressed and composited into a sheet-like combination (see FIG. 2) Then it is placed between the positive electrode and the negative electrode of the lithium secondary battery.

In FIG. 3, the thickness of the cladding layer 2 is less than or equal to 20 nm. Further, the thickness of the coating layer 2 may be in the range of 5nm-20nm. As described above, when the inorganic solid electrolyte particles 12 with the coating layer 2 of this thickness are made into the sheet-shaped combination shown in FIG. 2, the growth and diffusion of lithium dendrites can be effectively avoided, and the Li ⁺ The effective conduction therein enables the composite electrolyte 10 to still have a relatively high lithium ion conductivity. Further, in FIG. 3, the mass of the coating layer 2 is 0.1%-2% of the mass of the composite solid electrolyte material 10 to minimize the influence on the lithium ion conductivity of the inorganic solid electrolyte particles 12.

In the foregoing embodiments of the present application, the material of the coating layer 2 is an insulating polymer, and the material of the coating layer 2 is specifically packaging materials used in the fields of microelectronics, semiconductors, and the like. Among them, the insulating polymer can be selected from polyolefin, polyacrylic acid (PAA), polyacrylate, polyimide, polyvinylpyrrolidone (PVP), polyethylene terephthalate (PET), polyurethane, and polyester. At least one of xylene and its derivatives and copolymers.

Specifically, the insulating polymer may be, for example, polymethyl methacrylate (PMMA), polymethyl acrylate, polyethyl acrylate, polybutyl acrylate, polyoctyl acrylate and other polyacrylates, polyethylene (PE), polyacrylate, etc. Polyolefins such as propylene (PP) and polystyrene, as well as Parylene N (Parylene N), Parylene C (Parylene C), Parylene D (Parylene D), Parylene F (Parylene F), Parylene HT (Parylene HT) or its derivatives. Among them, the structural formula of Parylene N is shown in formula (I), the structural formula of Parylene C is shown in formula (II), the structural formula of Parylene D is shown in formula (Ⅲ), the structural formula of Parylene HT As shown in formula (IV), the structural formula of Parylene F is as shown in formula (Ⅴ):

In formula (I) to formula (V), n1 to n5 are independently selected from integers greater than 1.

In the embodiment of the present application, the molecular weight of the above-mentioned insulating polymer is 5,000 to 500,000. The insulating polymer with a molecular weight in this range is more helpful for forming the above-mentioned coating layer with uniform film formation and high coating integrity. Here, for polyolefins, the molecular weight specifically refers to the weight average molecular weight. In some embodiments of the present application, the molecular weight of the above-mentioned insulating polymer is 10,000 to 500,000, or 50,000 to 400,000.

In some embodiments of the present application, the degree of branching of polyolefin is 40-150 branches/1000 main chain carbons, and the branched groups of polyolefin include branched or branched alkyl groups with 1-6 carbon atoms. . Specifically, the branched chain group of the polyolefin may be at least one of methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, and the like. The above-mentioned branched polyolefin can ensure a high degree of spreading and strong anchoring effect of the formed coating layer on the body of the inorganic electrolyte. In addition, the alkyl group having 1 to 6 carbon atoms does not contain unsaturated bonds, so that the polyolefin has stable chemical properties and oxidation resistance.

In some other embodiments of the present application, the degree of branching of the polyolefin is 50-130 branches/1000 main chain carbons. For example, 80 branches/1000 main chain carbons, 90 branches/1000 main chain carbons, 100 branches/1000 main chain carbons, 110 branches/1000 main chain carbons or 120 branches /1000 main chain carbons. In some embodiments, the molecular weight distribution index of the polyolefin is 1-5. In other embodiments, the molecular weight distribution index of the polyolefin is 1.1-3. A lower molecular weight distribution index means that the molecular weight distribution of the polyolefin is more concentrated.

In this application, the coating layer made of parylene or its derivatives has a high degree of adhesion to the above-mentioned inorganic solid electrolyte body, and can be conformed to surfaces of various shapes (such as sharp edges, gaps and Hole surface, etc.), and the formed coating layer has uniform thickness, good continuity, compactness and no pinholes.

In some embodiments of the present application, the molecular weight of parylene and its derivatives is 50,000-500,000. Parylene and its derivatives with a molecular weight in this range are used as the coating layer, which has the advantages of more uniform film formation, complete coating, and extremely high density of the coating layer. In other embodiments of the present application, the molecular weight of parylene and its derivatives is 50,000 to 400,000. In some embodiments of the present application, the foregoing n1 to n5 are independently selected from an integer of 280-4800, such as 300, 500, 1000, 2000, or 3000. In other embodiments, n1 to n5 are independently selected from an integer of 500-3800.

In the foregoing embodiments of the present application, the material of the inorganic solid electrolyte particles includes at least one of an oxide-type solid electrolyte and a sulfide-type solid electrolyte. Among them, the oxide type solid electrolyte may include a lithium fast ion conductor (LISICON) type solid electrolyte, a garnet type solid electrolyte, a perovskite type solid electrolyte, and a sodium fast ion conductor (NASICON) type solid electrolyte. The sulfide-type solid electrolyte may include a thio-LISICON type solid electrolyte and a glassy sulfide solid electrolyte. Further, the particle size of the inorganic solid electrolyte particles may be 1 nm-5 μm.

Specifically, the garnet-type solid electrolyte may be Li _7+ab-3c Al _c La _3-a X _a Zr _2-b Y _b O ₁₂ ; where 0≤a≤1, 0≤b≤1, 0≤c≤ 1. X is one or more of La, Ca, Sr, Ba, and K, and Y is one or more of Ta, Nb, W, and Hf. The chemical formula of the perovskite solid electrolyte can be A ¹ _x1 B ¹ _y1 TiO ₃ , A ¹ _x2 B ² _y2 Ta ₂ O ₆ , A ³ _x3 B ³ _y3 Nb ₂ O ₆ , or A _h M _k D _n Ti _w O ₃ , where x1+3y1=2, 0<x1<2, 0<y1<2/3; x2+3y2=2, 0<x2<2, 0<y2<2/3; x3+3y3=2 , 0＜x3＜2, 0＜y3＜2/3; h+2k+5n+4w=6, h, k, n, and w are all greater than 0; A is at least one of Li and Na elements, and B is At least one of La, Ce, Pr, Y, Sc, Nd, Sm, Eu, and Gd elements, M is at least one of Sr, Ca, Ba, Ir, Pt elements, and D is one of Nb and Ta elements At least one. The NASICON solid electrolyte can be _{one or more of LiE 2} (PO ₄ ) ₃ and its dopants, where E is Ti, Zr, Ge, Sn or Pb, and the doping elements used in the dopants are selected From one or more of Mg, Ca, Sr, Ba, Sc, Al, Ga, In, Nb, Ta, and V. The sulfide-type solid electrolyte may include crystalline Li _d Q _e P _f S _g (Q is one or more of Si, Ge, and Sn, where d+4e+5f=2g, 0≤e≤1.5), Glassy Li ₂ SP ₂ S ₅ (including Li ₇ P ₃ S ₁₁ , 75Li ₂ S-25P ₂ S ₅ and other _{products composed of different Li 2} S and P ₂ S ₅ ), glass ceramic Li ₂ SP ₂ S ₅ and One or more of its dopants.

In a specific embodiment of the present application, the inorganic solid electrolyte particles may be a garnet-type solid electrolyte Li ₇ La ₃ Zr ₂ O ₁₂ (LLZO), a thio-lithium fast ion conductor structure of Li ₁₀ GeP ₂ S ₁₂ (LGPS) Particles.

The composite solid electrolyte material provided by the embodiments of this application can be used in the charging of lithium secondary batteries by providing an insulating coating layer on the surface of the inorganic solid electrolyte body that can completely cover its outer surface. In the process of discharging, it blocks electrons from the negative electrode to the inside of the inorganic solid electrolyte body with a certain electronic conductivity, without affecting the ionic conductivity characteristics of the inorganic solid electrolyte body, thereby effectively inhibiting the growth and diffusion of lithium dendrites and improving lithium dendrites The resulting short circuit of the battery improves battery safety.

Correspondingly, an embodiment of the present application also provides a method for preparing a composite solid electrolyte material, including:

The inorganic solid electrolyte body is covered with an insulating polymer to form a coating layer that completely covers the outer surface of the inorganic solid electrolyte body to obtain a composite solid electrolyte material; wherein the thickness of the coating layer is less than or equal to 20 nm.

In the embodiments of the present application, the materials and thicknesses of the insulating polymer and the inorganic solid electrolyte body are as described in any one of the foregoing embodiments herein, and will not be repeated here.

In one embodiment of the present application, the body of the inorganic solid electrolyte is an inorganic solid electrolyte sheet, and the inorganic solid electrolyte sheet is made of a plurality of inorganic solid electrolyte particles by cold pressing, hot pressing, casting, or calcination with a binder. have to. For example, a plurality of inorganic solid electrolyte particles may be hot-pressed under conditions of 240° C. and 200 MPa to form an inorganic solid electrolyte sheet. Among them, the particle size of the inorganic solid electrolyte particles may be 1 nm-5 μm.

In another embodiment of the present application, the inorganic solid electrolyte body is inorganic solid electrolyte particles. The particle size of the inorganic solid electrolyte particles can be 1nm-5μm.

In another embodiment of the present application, in the case where the inorganic solid electrolyte body is inorganic solid electrolyte particles, the above preparation method further includes: pressing a plurality of inorganic solid electrolyte particles coated with a coating layer on their outer surfaces into a sheet-like combination body. Specifically, the preparation method includes: providing a plurality of inorganic solid electrolyte particles, coating the body of each inorganic solid electrolyte particle with an insulating polymer to form a coating layer that completely covers the outer surface of the inorganic solid electrolyte particles; The inorganic solid electrolyte particles coated with a coating layer on the surface are compressed into a sheet-shaped combined body.

In the embodiments of the present application, the above-mentioned pressing may specifically include a cold pressing method or a hot pressing method, so that the structure of the coating layer may not be affected.

In the embodiments of the present application, the coating layer may be formed by coating, chemical vapor deposition, vapor deposition deposition or sputtering. Among them, evaporation deposition and sputtering methods belong to physical vapor deposition, and both of them and coating methods are suitable for preparing coating layers of various materials. In this application, evaporation deposition is heating the insulating polymer in a vacuum environment to evaporate or sublime, and then deposit it on the body of the inorganic electrolyte; the heating method can include resistance heating, electron beam heating, and high-frequency induction current Heating, laser beam heating, etc. In this application, using sputtering to form the coating layer includes: using argon glow discharge or radio frequency glow discharge or magnetron glow discharge to bombard the insulating polymer target, which is sputtered out and deposited on the inorganic On the electrolyte body.

The coating method may specifically include one or a combination of drip coating, brush coating, spray coating, dip coating, blade coating, and spin coating. The coating time and temperature can be set according to actual needs, and the specific coating time can be 1 min-2h, for example, 1-10 min. The coating temperature can be 20°C-120°C, for example 20-40°C. The coating operation can be carried out in a drying room or under a protective atmosphere.

In a specific embodiment of the present application, the coating is dip coating, specifically, the inorganic solid electrolyte sheet or inorganic solid electrolyte particles are immersed in the coating solution used for coating, fully contacted with the coating solution, and then taken out, dry. The dipping method can ensure that the outer surface of the inorganic solid electrolyte sheet or the inorganic solid electrolyte particles and even the inner walls of the pores communicating with the outside can be completely covered by the coating layer, and the coating solution can be used repeatedly.

In the embodiment of the present application, the coating solution used for coating includes an insulating polymer and an organic solvent. Among them, the organic solvent may include, but is not limited to, ethanol, acetone, methyl butanone, cyclohexane, toluene, xylene, nitrogen methyl pyrrolidone, acetone, acetonitrile, ethanol, dimethyl carbonate, ethyl methyl carbonate, dicarbonate Ethyl ester, tetrahydrofuran, dimethyl ether, dimethyl sulfide, 1,3-dioxolane, 1,4-dioxane, 1,2-dimethoxyethane, ethylene glycol dimethyl ether Ether, bis-trifluoroethyl ether, hexafluoroisopropyl methyl ether, hexafluoroisopropyl ethyl ether, perfluorobutyl methyl ether, perfluorobutyl ethyl ether, tetrafluoroethyltetrafluoropropyl ether, tetrafluoroethyl One or more of octafluoropentyl ether.

Further, in the coating solution of the embodiment of the present application, the mass ratio of the insulating polymer to the organic solvent is 1:5-100. The appropriate insulating polymer concentration in the coating solution can not only ensure that the coating solution is smoothly in contact with the surface of the inorganic solid electrolyte sheet or particle, or fully penetrated into the internal gaps or holes connected to the outer surface, but also can ensure The formed coating layer is better combined with the inorganic solid electrolyte sheet or inorganic solid electrolyte particles.

In the embodiments of the present application, when the material of the coating layer is parylene or its derivatives, it can be formed by chemical vapor deposition (Chemical Vapor Deposition, CVD), which may specifically include the following steps:

(i) Place the dry inorganic solid electrolyte particle powder or inorganic solid electrolyte sheet on the deposition sample stage in the deposition chamber of the CVD coating machine, and vacuumize to below 1×10 ^-2 Pa; wherein, the CVD coating machine includes Evaporation chamber, pyrolysis chamber and deposition chamber connected in sequence;

(ii) Place the powder of parylene or its derivatives in the evaporation chamber of the CVD coating machine, and when the vacuum in the evaporation chamber reaches 0.5Pa-2Pa, heat to 160-200°C to vaporize the powder;

(iii) Control the temperature of the cracking chamber of the CVD coating machine at 600-700°C, so that the vaporized parylene or its derivatives enter the cracking chamber to be cracked and generate active monomers;

(Iv) Control the temperature of the chamber wall of the deposition chamber to be 110-130°C, and the temperature of the deposition sample table to be 15-25°C, so that the active monomer enters the deposition chamber, and deposits on the deposition sample table to form a polymer material A coating layer of toluene or its derivatives; wherein, during the deposition process, the deposition rate is kept less than or equal to

The deposition time is 250s-1000s.

Using parylene as the precursor, it is vaporized to generate dimers, and then through high temperature cracking and breaking of molecular bonds to generate xylene active monomers. The active monomers are placed in inorganic solid electrolyte particles or electrolyte sheets in a vacuum chemical vapor deposition furnace In-situ polymerization and deposition on the surface of the film to form a Parylene film.

Parylene or its derivatives can be deposited in situ by the CVD method under vacuum, and the active monomers produced after gasification and cracking "grow" completely conformal coatings on the surface of various formed substrates The layer has uniform thickness, good continuity, compactness and no pinholes, and it can fully cover the inorganic solid electrolyte particles/sheets, effectively preventing electron conduction into the inorganic solid electrolyte and causing lithium deposition.

In a specific embodiment of the present application, in step (ii), when the vacuum degree in the evaporation chamber is 0.8 Pa-1.2 Pa, the evaporation chamber is heated to vaporize the above-mentioned powder.

In step (iv), the temperature of the deposition sample table is much lower than the temperature of the chamber wall of the deposition chamber, so that the parylene and its derivatives can be deposited on the deposition sample table to the greatest extent and waste of raw materials is avoided. Further, the temperature of the deposition sample stage may be 18-25°C.

In step (ⅳ), the deposition rate can be at

Further can be

The lower deposition rate can ensure that the surface of the inorganic solid electrolyte particles or the inorganic solid electrolyte sheet is slowly and uniformly deposited to form a dense and complete coating layer that can completely cover the surface. In step (iv), the deposition time can be 250s-900s.

Further, during the deposition process, the deposition sample table can be rotated 360°, so that the active monomer can fully contact the inorganic solid electrolyte particles or sheets, and the uniformity of the formed coating layer can be ensured.

The preparation method of the composite solid electrolyte material provided by the embodiments of the present application has a simple process, easy control, and large-scale production.

4, an embodiment of the present application also provides a lithium secondary battery 100, including a positive electrode 20, a negative electrode 30, and a solid electrolyte 10' between the positive electrode 20 and the negative electrode 30, the solid electrolyte 10' It includes the composite solid electrolyte material 10 described in the embodiment of the present application.

Specifically, the solid electrolyte 10' may be directly the composite solid electrolyte material 10 shown in FIG. 1 or FIG. 2, and may also include the composite solid electrolyte material shown in FIG. The inorganic solid electrolyte particles 12 coated with the coating layer 2 are compressed and combined into a sheet-shaped combined body as shown in FIG. 2.

Since the lithium secondary battery 100 adopts the composite solid electrolyte material 10 that can avoid the growth and diffusion of lithium dendrites, during the charging and discharging process of the lithium secondary battery 100, the coating layer in the composite solid electrolyte material 10 can be used. 2 Prevent electrons from passing into the inorganic solid electrolyte body from the negative electrode 30, thereby effectively inhibiting the growth and diffusion of lithium dendrites, and avoiding battery short circuit problems caused by lithium dendrites. The lithium secondary battery 100 has better cycle performance And safety performance.

In the embodiment of the present application, the negative electrode 30 is a lithium negative electrode, and the lithium negative electrode includes metallic lithium or a lithium alloy, where the lithium alloy includes at least one of a lithium silicon alloy, a lithium aluminum alloy, a lithium tin alloy, and a lithium indium alloy.

In an embodiment of the present application, the positive electrode 20 may include a positive electrode active material, a conductive agent, and a solid electrolyte material without a coating layer. Specifically, a positive electrode active material, a conductive agent, and a solid electrolyte material without a coating layer may be formed into a sheet-shaped positive electrode. The positive electrode active material is a commonly used material in the field of lithium batteries, such as lithium iron phosphate, lithium manganese phosphate, lithium vanadium phosphate, lithium cobalt phosphate, lithium titanium phosphate, lithium cobalt oxide (LiCoO ₂ ), lithium manganate, lithium manganese nickelate , At least one of lithium nickel manganese oxide, nickel cobalt manganese (NCM), nickel cobalt aluminum (NCA), and the like. In addition, the surface of the positive electrode active material may also be provided with a buffer coating layer commonly used for solid-state battery positive electrode materials, such as LiNbO ₃ , LiTaO ₃ , Li ₃ PO ₄ , Li ₄ Ti ₅ O ₁₂ and the like.

In another embodiment of the present application, the positive electrode 20 may include a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector, and the positive electrode active material layer faces and contacts the composite solid electrolyte 10'. The positive electrode active material layer may be coated or pressed on the positive electrode current collector. Among them, the positive electrode active material layer 22 may include a positive electrode active material, a conductive agent, and a solid electrolyte material without a coating layer. The thickness of the positive electrode active material layer may be 5 μm-150 μm, and further be 20-50 μm. Optionally, the positive electrode active material layer may further include a binder, such as polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl alcohol, carboxymethyl cellulose, and the like.

The positive electrode current collector includes but is not limited to metal foil or alloy foil, the metal foil includes copper, titanium, aluminum, platinum, iridium, ruthenium, nickel, tungsten, tantalum, gold or silver foil, and the alloy foil Including stainless steel, or an alloy containing at least one element of copper, titanium, aluminum, platinum, iridium, ruthenium, nickel, tungsten, tantalum, gold, and silver. Optionally, the alloy foil material uses the above-mentioned elements as main components. The metal foil may further include a doping element, the doping element including but not limited to one of platinum, ruthenium, iron, cobalt, gold, copper, zinc, aluminum, magnesium, palladium, rhodium, silver, and tungsten Or multiple. The positive electrode current collector can be etched or roughened to form a secondary structure to facilitate effective contact with the positive electrode active material layer.

As shown in FIG. 5, an embodiment of the present application also provides a terminal 200. The terminal 200 may be a mobile phone, a tablet computer, a notebook, a portable machine, a smart wearable product, and other electronic products. The terminal 200 includes a terminal 200 assembled on the outside of the terminal. The housing 201, and the circuit board and battery (not shown in the figure) located inside the housing 201, where the battery is the lithium secondary battery 100 provided in the above embodiment of the application, and the housing 201 may include a display screen assembled on the front side of the terminal And the back cover assembled on the back side, the battery can be fixed inside the back cover to supply power to the terminal 200.

The following is a further description of the embodiments of the present application in multiple embodiments.

Example 1

This embodiment provides a method for preparing a composite solid electrolyte sheet and an all-solid lithium secondary battery, which includes the following steps:

(1) Preparation of composite solid electrolyte sheet:

(a) Weigh 3.08g of lithium hydroxide monohydrate, 9.77g of lanthanum oxide and 2.46g of zirconia powder, put them into an agate ball mill tank, and add 3g of isopropanol as a solvent, and add the diameters of them respectively 10mm and 5mm agate balls are used as the ball milling medium, and are milled in a planetary high-energy ball mill at a speed of 500 rpm for 6 hours; after the ball milled mixture is fully dried, it is placed in a corundum crucible and calcined at 950°C for 10 hours to obtain Li ₇ La ₃ Zr ₂ O ₁₂ (LLZO) crude powder; then the obtained crude powder is subjected to secondary ball milling and drying, and then placed in an agate mortar to grind and sieved (200 mesh); take 500 mg of the sieved powder in After applying 40MPa pressure in the mold to compress into tablets, bury it in mother powder, put it in an alumina crucible, cover it, and place it in a furnace for calcination at 1200°C for 15 hours; finally, it is ground into powder to obtain a coating Li ₇ La ₃ Zr ₂ O ₁₂ (LLZO) granular powder;

(b) Dissolve 0.5g of polyethylene (PE) powder in toluene (20g) at 120°C and stir to obtain a uniform polyethylene coating solution; wherein the weight average molecular weight of PE is 156,000 and the molecular weight distribution index is 1.9 , The degree of branching is 80 branches/1000 main chain carbons (the content of methyl branches in the branches is 38.5 mol%, the content of ethyl branches is 17.9 mol%, the content of propyl branches is 6.2 mol%, carbon The content of branches with numbers 3-6 is 37.4mol%);

Weigh 1g of the above-mentioned LLZO powder and immerse it in the coating solution, keep in contact at 120°C for 2 minutes, and then filter and dry to obtain LLZO solid electrolyte particles whose outer surface is completely covered by PE. The thickness of the PE layer is 10nm;

Weigh 100 mg of the above-mentioned LLZO solid electrolyte particles completely covered by PE, and place them in a tableting mold with a diameter of 10 mm for cold pressing at room temperature. The pressure is set to 150 MPa, and the pressure is kept for 10 minutes to obtain a composite solid electrolyte sheet LLZO @ with a thickness of 400 μm. PE;

(2) Preparation of positive electrode powder: water and an oxygen content of less than 0.1ppm in an inert atmosphere glove box, having weighed 0.70g (LiNbO cladding mass of LiCoO ₂ LiNbO ₃ coated positive electrode active material of LiCoO ₂ and ₃ The ratio is 5:95), 0.28g of the above-mentioned uncoated Li ₇ La ₃ Zr ₂ O ₁₂ (LLZO) solid electrolyte powder and 0.02g of conductive carbon black. Place the three powders in an agate mortar for grinding and mixing. Obtain a uniformly mixed positive electrode powder;

(3) Lithium cobaltate/solid electrolyte (SE)/lithium (LiCoO ₂ /SE/Li) battery assembly: In an inert atmosphere glove box with a water and oxygen content of less than 0.1 ppm, weigh 10 mg of the above-mentioned positive electrode powder and pour it Put the pressed composite solid electrolyte sheet (LLZO@PE) into a mold, spread it evenly on one side of the composite solid electrolyte sheet, and then perform room temperature cold pressing, set the pressure to 100MPa, and hold the pressure for 10 minutes, and then place it on the composite electrolyte sheet. A metal lithium sheet with a diameter of 10 mm is added to the other side of the battery, and finally assembled into a mold battery, that is, a lithium cobaltate/composite solid electrolyte/lithium (LiCoO ₂ /SE/Li) battery is obtained.

Example 2

This embodiment provides a method for preparing a composite solid electrolyte sheet and an all-solid lithium secondary battery, which includes the following steps:

(1) Preparation of composite solid electrolyte sheet:

_{Prepare the Li 7} La ₃ Zr ₂ O ₁₂ (LLZO) particle powder to be coated according to the method described in Example 1;

Take 1g of LLZO granular powder and place it on a clean glass plate, and place them in the deposition chamber of the CVD coating machine together, and vacuum to 1×10 ^-2 Pa; then add 0.2g of Parylene N powder (molecular weight 99944) to the CVD When the evaporation chamber of the coating machine is evacuated until the vacuum reaches 1Pa, the evaporation chamber is heated to a temperature of 200°C to vaporize Parylene N; at the same time, the temperature of the cracking chamber of the CVD coating machine is controlled to 650°C, waiting for evaporation The Parylene N gasification product in the chamber enters and decomposes to generate active monomers; the temperature of the chamber wall and the deposition sample stage of the deposition chamber are controlled to 120 ℃ and 20 ℃ respectively, so that Parylene N is deposited in situ on the surface of the LLZO particles. Obtain the deposition amount with a balance, stop the deposition when the deposition thickness reaches 10nm, take out the sample, and obtain the LLZO composite solid electrolyte particles whose outer surface is completely covered by Parylene N;

Weigh 100 mg of the composite solid electrolyte particles and place them in a tableting mold with a diameter of 10 mm for cold pressing at room temperature, set the pressure to 150 MPa, and hold the pressure for 10 minutes to obtain composite solid electrolyte tablets LLZO@Parylene N with a thickness of 400 μm;

(2) Preparation of positive electrode powder: water and an oxygen content of less than 0.1ppm in an inert atmosphere glove box, having weighed 0.70g (LiNbO cladding mass of LiCoO ₂ LiNbO ₃ coated positive electrode active material of LiCoO ₂ and ₃ The ratio is 5:95), 0.28g of the above-mentioned uncoated Li ₇ La ₃ Zr ₂ O ₁₂ (LLZO) solid electrolyte powder and 0.02g of conductive carbon black. Place the three powders in an agate mortar for grinding and mixing. Obtain a uniformly mixed positive electrode powder;

(3) Lithium cobaltate/solid electrolyte/lithium (LiCoO ₂ /SE/Li) battery assembly: In an inert atmosphere glove box with water and oxygen content of less than 0.1 ppm, weigh 10 mg of the above-mentioned positive electrode powder and pour it into the press to finish In the mold of the composite solid electrolyte sheet (LLZO@Parylene N), spread it evenly on one side of the composite solid electrolyte sheet, and then perform cold pressing at room temperature. The pressure is set to 100 MPa, and the pressure is maintained for 10 minutes. A metal lithium sheet with a diameter of 10 mm is added on one side, and finally assembled into a mold battery, that is, a lithium cobaltate/composite solid electrolyte/lithium (LiCoO ₂ /SE/Li) battery is obtained.

Example 3

This embodiment provides a method for preparing a composite solid electrolyte sheet and an all-solid lithium secondary battery, which includes the following steps:

(1) Preparation of composite solid electrolyte sheet:

(a) Weigh 2.30g of anhydrous lithium sulfide powder, 1.37g of anhydrous germanium sulfide powder and 4.67g of anhydrous phosphorus sulfide powder in an inert atmosphere glove box with a water and oxygen content of less than 0.1ppm, and add high-energy In the ball mill tank of the ball mill, add zirconia grinding balls with diameters of 10 mm and 5 mm respectively as the ball milling medium. After the ball mill tank is pressurized and sealed with a special sealing cover, the ball mill is transferred to the ball mill to start ball milling, and the parameters of the ball mill are set. 650rpm ball milling for 10 hours; after the ball milling, the ball milling jar is transferred back to the glove box to disassemble, the powder after ball milling is separated, and compressed into tablets at room temperature, sealed in a vacuum quartz tube, and heated in a heating furnace Keep it at 650°C for 20h, grind the heated product into powder to obtain Li ₁₀ GeP ₂ S ₁₂ (LGPS) electrolyte powder;

(b) After placing 1g of LGPS granular powder on a clean glass plate, place them in the deposition chamber of the CVD coating machine together, and vacuum to 1×10 ^-2 Pa; then add 0.5g of Parylene C (molecular weight 9997) The powder is put into the evaporation chamber of the CVD coating machine, and vacuumed until the vacuum degree reaches 1Pa, the evaporation chamber is heated to a temperature of 200 ℃ to vaporize Parylene C; at the same time, the temperature of the cracking chamber of the CVD coating machine is controlled to 650 ℃ Wait for the Parylene C gasification product in the evaporation chamber to enter and crack to generate active monomers; respectively control the temperature of the chamber wall and deposition sample table of the deposition chamber to 120°C and 20°C, so that Parylene C is deposited in situ on the surface of the LGPS particles. Obtain the deposition amount through a quartz microbalance, stop the deposition when the deposition thickness reaches 10nm, take out the sample, and obtain the LGPS composite solid electrolyte particles LGPS@Parylene C whose outer surface is completely covered by Parylene C;

Weigh 120 mg of the composite solid electrolyte particles and place them in a tableting mold with a diameter of 10 mm for room temperature cold pressing, set the pressure to 150 MPa, and hold the pressure for 10 minutes to obtain composite solid electrolyte tablets LGPS@Parylene C with a thickness of 500 μm;

(2) Preparation of positive electrode powder: water and an oxygen content of less than 0.1ppm in an inert atmosphere glove box, having weighed 0.70g (LiNbO cladding mass of LiCoO ₂ LiNbO ₃ coated positive electrode active material of LiCoO ₂ and ₃ The ratio is 5:95), 0.28g of the above-mentioned uncoated Li ₁₀ GeP ₂ S ₁₂ (LGPS) electrolyte powder and 0.02g of conductive carbon black. Place the three powders in an agate mortar for grinding and mixing to obtain a uniform mixture的positive powder;

(3) Lithium cobaltate/solid electrolyte/lithium (LiCoO ₂ /SE/Li) battery assembly: In an inert atmosphere glove box with water and oxygen content of less than 0.1 ppm, weigh 10 mg of the above-mentioned positive electrode powder and pour it into the press to finish In the mold of the composite solid electrolyte sheet (LGPS@Parylene C), spread it evenly on one side of the composite solid electrolyte sheet, and then perform room temperature cold pressing. The pressure is set to 100 MPa, and the pressure is maintained for 10 minutes. A metal lithium sheet with a diameter of 10 mm is added on one side, and finally assembled into a mold battery, that is, a lithium cobaltate/composite solid electrolyte/lithium (LiCoO ₂ /SE/Li) battery is obtained.

Example 4

This implementation provides a method for preparing a composite solid electrolyte sheet and a solid lithium secondary battery, which includes the following steps:

(1) Preparation of composite solid electrolyte sheet:

_{(a) Prepare Li 10} GeP ₂ S ₁₂ (LGPS) electrolyte powder according to the method described in Example 2. Weigh 100 mg of LGPS granular powder and place it in a tableting mold with a diameter of 10 mm under the conditions of 240 ℃ and 200 MPa Hot press for 10 minutes to obtain an LPGS electrolyte sheet with a thickness of 400 μm;

(b) Put the obtained LGPS electrolyte sheet on a clean glass plate, and place them in the deposition chamber of the CVD coating machine together, and vacuum to 1×10 ^-2 Pa; then add 0.3g of Parylene C powder with a molecular weight of 9997 When the evaporation chamber of the CVD coating machine is evacuated until the vacuum reaches 1Pa, the evaporation chamber is heated to a temperature of 200°C to vaporize Parylene C; at the same time, the temperature of the cracking chamber of the CVD coating machine is controlled to 650°C, waiting The Parylene C gasification product in the evaporation chamber enters and decomposes to generate active monomers; the temperature of the chamber wall and the deposition sample table of the deposition chamber is controlled to 120 ℃ and 20 ℃ respectively, so that Parylene C is deposited in situ on the surface of the LGPS electrolyte sheet. The quartz microbalance obtains the deposition amount, stops the deposition when the deposition thickness reaches 10nm, takes out the sample, and obtains the LGPS composite electrolyte sheet LGPS@Parylene C whose outer surface is completely covered by Parylene C;

(2) Preparation of positive electrode powder: water and an oxygen content of less than 0.1ppm in an inert atmosphere glove box, having weighed 0.70g (LiNbO cladding mass of LiCoO ₂ LiNbO ₃ coated positive electrode active material of LiCoO ₂ and ₃ The ratio is 5:95), 0.28g of the above-mentioned uncoated Li ₁₀ GeP ₂ S ₁₂ (LGPS) electrolyte powder and 0.02g of conductive carbon black. Place the three powders in an agate mortar for grinding and mixing to obtain a uniform mixture的positive powder;

(3) Lithium cobaltate/solid electrolyte/lithium (LiCoO ₂ /SE/Li) battery assembly: In an inert atmosphere glove box with a water and oxygen content of less than 0.1 ppm, the composite solid electrolyte sheet LGPS obtained in step 1 above @Parylene C is placed in a tableting mold, weighed 10mg of the above-mentioned positive electrode powder and poured into the tableting mold to spread evenly on the composite solid electrolyte sheet LGPS@Parylene C, and then cold pressed at room temperature, The pressure is set to 100MPa, the pressure is maintained for 10 minutes, and then a metal lithium sheet with a diameter of 10mm is added to the other side of the composite solid electrolyte sheet, and finally assembled into a mold battery, that is, lithium cobalt oxide/composite solid electrolyte/lithium-indium (LiCoO ₂ /SE/Li-In) battery.

In order to highlight the beneficial effects of the embodiments of the present application, the following comparative examples 1-2 are provided:

Comparative Example 1 provides a LiCoO ₂ /SE/Li battery. The assembly process is as follows: LLZO powder without coating layer is made into a solid electrolyte sheet by cold pressing, and it is combined with a lithium metal negative electrode and containing a LiNbO ₃ coating The positive electrode powder of LiCoO ₂ positive active material is assembled into an all-solid-state lithium battery in the form of layered sheets.

Comparative Example 2 provides a LiCoO ₂ /SE/Li battery. The assembly process is as follows: the LGPS powder without coating layer is made into a solid electrolyte sheet by hot pressing, and it is combined with a lithium metal negative electrode and contains a LiNbO ₃ package The positive electrode powder coated with LiCoO ₂ positive electrode active material is assembled into an all-solid-state lithium battery in the form of layered sheets.

In order to strongly support the beneficial effects brought about by the technical solutions of the embodiments 1-4 of this application, the following tests are provided:

The battery assembled in Examples 1-4 of the present application and the battery assembled in Comparative Example 1-2 were ^{subjected to constant current charge and discharge tests at a current density of 0.1 mA/cm 2} , where the battery voltage range of the lithium-containing metal negative electrode At 2.5-4.2V, the test results are listed in Table 1 below.

Table 1 Performance test results of all-solid-state lithium batteries assembled with different solid-state electrolytes

It can be known from the test results in Table 1 that the capacity retention rate of the batteries in Examples 1-4 of the present application after 50 weeks of cycling is much higher than that of the batteries in Comparative Example 2, while the lithium cobalt oxide/LLZO cold-pressed of Comparative Example 1 The chip/lithium battery had a short circuit when it was cycled to 30 weeks, causing the battery to fail. This shows that the composite solid electrolyte material coated with electronically insulating polymer effectively isolates the electrons in the negative electrode from entering the solid electrolyte, thereby inhibiting the growth of lithium dendrites, improving battery short circuit caused by lithium dendrites, and improving The cycle stability of the battery is improved.

Claims (20)

1. A composite solid electrolyte material, characterized in that it comprises an inorganic solid electrolyte body and a coating layer that completely covers the outer surface of the inorganic solid electrolyte body, the material of the coating layer is an insulating polymer, and the coating layer The thickness is less than or equal to 20nm.
2. The composite solid electrolyte material of claim 1, wherein the thickness of the coating layer is 5 nm-20 nm.
3. 8. The composite solid electrolyte material of claim 1, wherein the coating layer also completely covers the inner wall of the pore that communicates with the outside of the inorganic solid electrolyte body.
4. The composite solid electrolyte material of claim 1, wherein the electronic conductivity of the coating layer is less than or equal to 10 ^-12 S·cm ^-1 .
5. The composite solid electrolyte material of claim 1, wherein the ionic conductivity of the composite solid electrolyte material at room temperature is 10 ^-6 S·cm ^-1 or more.
6. The composite solid electrolyte material of claim 1, wherein the insulating polymer in the composite solid electrolyte material accounts for 0.1% to 2% by weight.
7. The composite solid electrolyte material according to any one of claims 1 to 6, wherein the insulating polymer is selected from the group consisting of polyolefin, polyacrylic acid, polyacrylate, polyimide, polyvinylpyrrolidone, and poly(p-phenylene). At least one of ethylene glycol diformate, polyurethane, parylene and its derivatives and copolymers.
8. 8. The composite solid electrolyte material according to claim 7, wherein the molecular weight of the insulating polymer is 5,000 to 500,000.
9. The composite solid electrolyte material of claim 8, wherein the parylene and its derivatives include parylene N, parylene C, parylene D, parylene F, and parylene At least one of HT.
10. The composite solid electrolyte material of claim 8, wherein the degree of branching of the polyolefin is 40-150 branches/1000 main chain carbons, and the branched groups of the polyolefin include carbon atoms. A branched or branched alkyl group having a number of 1-6.
11. The composite solid electrolyte material according to any one of claims 1-10, wherein the inorganic solid electrolyte body is an inorganic solid electrolyte sheet or inorganic solid electrolyte particles.
12. The composite solid electrolyte material according to claim 1 or 11, wherein the material of the inorganic solid electrolyte body includes at least one of an oxide-type solid electrolyte and a sulfide-type solid electrolyte.
13. A method for preparing a composite solid electrolyte material, which is characterized in that it comprises:

    The inorganic solid electrolyte body is coated with an insulating polymer to form a coating layer that completely covers the outer surface of the inorganic solid electrolyte body to obtain a composite solid electrolyte material; wherein the thickness of the coating layer is less than or equal to 20 nm.
14. The preparation method according to claim 13, wherein the material of the insulating polymer is selected from polyolefin, polyacrylic acid, polyacrylate, polyimide, polyvinylpyrrolidone, polyethylene terephthalate At least one of ester, polyurethane, parylene and its derivatives and copolymers.
15. The preparation method according to claim 14, wherein the coating layer is formed by coating, chemical vapor deposition, vapor deposition deposition or sputtering.
16. The preparation method according to claim 15, wherein the coating solution used in the coating comprises the insulating polymer and an organic solvent, wherein the mass ratio of the insulating polymer to the organic solvent is 1 :5-100.
17. The preparation method according to claim 13, wherein the insulating polymer is parylene or its derivatives, and the coating layer is formed by chemical vapor deposition; in the chemical vapor deposition process, the deposition Speed is less than or equal to

    

    The deposition time is 250s-1000s.
18. A lithium secondary battery, characterized by comprising a positive electrode, a negative electrode, and a solid electrolyte located between the positive electrode and the negative electrode, wherein the solid electrolyte comprises any one of claims 1-12 The composite solid electrolyte material.
19. The lithium secondary battery according to claim 18, wherein the negative electrode is a lithium negative electrode, the lithium negative electrode includes metallic lithium or a lithium alloy, and the lithium alloy includes a lithium silicon alloy, a lithium aluminum alloy, and a lithium tin alloy. And at least one of lithium indium alloys.
20. A terminal, characterized by comprising a casing, a motherboard and a battery located inside the casing, the battery comprising the lithium secondary battery according to claim 18 or 19, the lithium secondary battery being used for The terminal is powered.

Images