CN109004265B

CN109004265B - Solid electrolyte positive electrode and solid battery comprising same

Info

Publication number: CN109004265B
Application number: CN201810843938.8A
Authority: CN
Inventors: 周素霞; 王晓明; 杨浩田; 钟燕琼
Original assignee: Jiangsu Zhuogao New Material Technology Co Ltd
Current assignee: Jiangsu Zhuogao New Material Technology Co Ltd
Priority date: 2018-07-27
Filing date: 2018-07-27
Publication date: 2020-10-27
Anticipated expiration: 2038-07-27
Also published as: CN109004265A

Abstract

The present invention relates to a composite positive electrode for a lithium ion battery, and a solid-state battery including the positive electrode. The solid electrolyte positive electrode includes: a positive electrode sheet having a positive electrode active material layer formed thereon, and a composite solid electrolyte layer formed on an outer surface of the positive electrode active material layer, wherein the composite solid electrolyte layer has a thickness of 1 to 50 μm; the composite solid electrolyte layer comprises an organic polymer, a lithium salt, a nano inorganic solid electrolyte, a binder and a wetting agent, wherein based on the total weight of the composite solid electrolyte layer, the content of the organic polymer is 5-80 wt%, the content of the lithium salt is 5-50 wt%, the content of the nano inorganic solid electrolyte is 10-85 wt%, the content of the binder is 1-12 wt%, and the content of the wetting agent is 0.1-0.5 wt%.

Description

Solid electrolyte positive electrode and solid battery comprising same

Technical Field

The disclosure relates to the field of battery anodes, and particularly relates to a solid electrolyte anode and a solid battery comprising the same.

Background

In recent years, in the field of new energy automobiles, the demand for lithium ion batteries has increased year by year. At present, the lithium ion battery generally adopts liquid organic electrolyte to conduct ions, but the organic electrolyte is easy to have accidents of liquid leakage, electrode corrosion, combustion explosion and the like, and has larger potential safety hazard.

Solid electrolyte batteries are gradually coming into the public view because of their organic liquid battery characteristics and high safety. The solid electrolyte comprises polymer electrolyte, inorganic electrolyte and composite electrolyte, the conductivity of the polymer electrolyte is lower at normal temperature, the cost of the inorganic solid electrolyte is higher, and the existing composite electrolyte has poorer mechanical property and larger resistance with the interface between the positive plate and the negative plate.

Disclosure of Invention

The inventor of the present application has found through intensive research that the interface stability and electrochemical working window of a separator and a positive electrode material can be improved and lithium ion cycle performance can be improved by preparing a solid electrolyte positive electrode by coating a composite solid electrolyte layer having a specific composition on the surface of a conventional positive electrode of a solid electrolyte battery, and the prepared solid battery has excellent thermal stability and mechanical strength performance, and has high ionic conductivity and lithium ion transport number at normal temperature.

An aspect of the present disclosure provides a solid electrolyte positive electrode, including:

a positive electrode sheet having a positive electrode active material layer formed thereon, and

a composite solid electrolyte layer formed on an outer surface of the positive electrode active material layer,

the composite electrolyte layer comprises an organic polymer, a lithium salt, a nano inorganic solid electrolyte, a binder and a wetting agent, wherein based on the total weight of the composite electrolyte layer, the content of the organic polymer is 5-80 wt%, the content of the lithium salt is 5-50 wt%, the content of the nano inorganic solid electrolyte is 10-85 wt%, the content of the binder is 1-12 wt%, and the content of the wetting agent is 0.1-0.5 wt%.

Another aspect of the present disclosure relates to a method of preparing the above solid electrolyte positive electrode, comprising:

(1) mixing a nano inorganic solid electrolyte, an organic polymer, a binder, a wetting agent and a solvent to obtain composite electrolyte slurry;

(2) and coating the composite electrolyte slurry on the outer surface of the positive electrode active material layer of the positive plate with the positive electrode active material layer, and drying to obtain the composite solid electrolyte layer.

Yet another aspect of the present disclosure relates to a solid-state battery including the above solid-state electrolyte positive electrode.

Advantageous effects

In the solid electrolyte positive electrode according to the present disclosure, the composite solid electrolyte layer is formed by mixing an organic polymer, a lithium salt, and a nano inorganic solid electrolyte and coating at one time, and the process is simple and easy to operate. The nano inorganic solid electrolyte is added into the organic polymer solid electrolyte, so that a smooth path is provided for lithium ion conduction, and the high-rate charge and discharge performance is good. In addition, the composite solid electrolyte layer enables lithium ions to be transferred and distributed uniformly, reduces lithium ion loss caused by formation of lithium dendrites, can improve interface stability and an electrochemical working window of the diaphragm and the anode material, and improves the lithium ion cycle performance. The adopted nano inorganic solid electrolyte has large specific surface area and high conductivity, increases the lithium ion transfer capacity and improves the ionic conductivity. The solid electrolyte anode has high ionic conductivity, high thermal stability, high mechanical property and high safety.

The solid-state battery according to the present disclosure has excellent thermal stability and mechanical strength properties, high ionic conductivity and lithium ion transport number at normal temperature.

Detailed Description

The present disclosure will be described in more detail below.

One aspect of the present disclosure provides a solid electrolyte positive electrode, including:

the composite solid electrolyte layer comprises an organic polymer, a lithium salt, a nano inorganic solid electrolyte, a binder and a wetting agent, wherein based on the total weight of the composite solid electrolyte layer, the content of the organic polymer is 5-80 wt%, the content of the lithium salt is 5-50%, the content of the nano inorganic solid electrolyte is 10-85 wt%, the content of the binder is 1-12 wt%, and the content of the wetting agent is 0.1-0.5 wt%.

The positive electrode active material layer may be formed on one or both surfaces of the positive electrode sheet. The thickness of each positive electrode active material layer may be 0.5 to 50 μm independently.

In the case where the positive electrode active material layers are formed on both sides of the positive electrode sheet, the composite electrolyte slurry may be applied to only the outer surface of one positive electrode active material layer, or the composite solid electrolyte layer may be formed by applying the composite electrolyte slurry to both the outer surfaces of the positive electrode active material layers.

The composite solid electrolyte layer independently has a thickness of 1 to 100 μm, for example 5 to 60 μm, preferably 10 to 50 μm.

In the present disclosure, there is no particular limitation on the material of the positive electrode sheet as long as it is a material that can be generally used for the positive electrode sheet in the art. For example, the positive electrode sheet may be an aluminum foil, and the thickness may be 8 to 15 μm.

The positive electrode active material layer comprises a positive electrode active material, a conductive agent and a binder, and preferably consists essentially of the positive electrode active material, the conductive agent and the binder, wherein the content of the positive electrode active material can be 50-95%, and preferably 60-85%, based on the total weight of the positive electrode active material layer; the content of the conductive agent can be 1-20%, preferably 5-15%; the content of the binder may be 2 to 30%, preferably 10 to 25%.

In the present disclosure, the positive electrode active material is not particularly limited as long as it is a positive electrode active material generally used for a lithium battery. For example, the positive electrode active material may be one or more selected from lithium manganate, lithium cobaltate, lithium iron phosphate, and ternary positive electrode materials.

In the present disclosure, the conductive agent is not particularly limited as long as it is a conductive agent generally used for a positive electrode. For example, the conductive agent may be one or more selected from acetylene black, conductive carbon black, carbon fiber, and graphene.

In the present disclosure, the binder is not particularly limited as long as it is a binder generally used for a positive electrode. For example, the binder may be at least one selected from polyvinylidene fluoride, styrene-butadiene rubber, styrene-acrylic emulsion, acrylic resin, polyacrylonitrile, and sodium carboxymethylcellulose.

The positive electrode active material layer may further include a thickener, for example, one or more selected from the group consisting of carboxymethyl cellulose (CMC), carboxyethyl cellulose, polyacrylamide, and polyurethane, wherein the content of the thickener may be 1 to 10 wt% based on the total weight of the positive electrode active material layer.

In the solid electrolyte positive electrode according to the present disclosure, the composite solid electrolyte layer may include an organic polymer, a lithium salt, a nano inorganic solid electrolyte, a binder, and a wetting agent. In some embodiments, the composite solid electrolyte layer consists essentially of an organic polymer, a lithium salt, a nano-inorganic solid electrolyte, a binder, and a wetting agent. By "consisting essentially of an organic polymer, a lithium salt, a nano-inorganic solid electrolyte, a binder, and a wetting agent" is meant that the organic polymer, lithium salt, nano-inorganic solid electrolyte, binder, and wetting agent comprise greater than 95 wt%, greater than 97 wt%, or, in some aspects, greater than 99 wt% of the composite solid electrolyte layer.

In the composite solid electrolyte layer, the organic polymer is used for forming a matrix of an organic polymer electrolyte, so that the problems of electrolyte leakage, poor safety, short circuit and the like easily occurring in a liquid lithium ion battery are solved. The organic polymer may be at least one selected from the group consisting of polyoxyethylene (also referred to as polyethylene oxide (PEO) or polyethylene glycol (PEG)), polyvinylidene fluoride-hexafluoropropylene, and polyethylene carbonate.

The content of the organic polymer may be 5 to 80 wt%, preferably 15 to 45 wt%, more preferably 20 to 35 wt%, based on the total weight of the composite solid electrolyte layer. Within the above quantity range, the organic polymer can play a role in improving the safety and flexibility of the battery, and the obtained composite solid electrolyte layer finally improves the safety of the solid electrolyte battery. In the case where the content of the organic polymer is less than 5% by weight, no polymer advantage is exerted. In the case where the content of the organic polymer is more than 80 wt%, the inorganic solid electrolyte accounts for a small amount, which may cause a decrease in ion conductivity, an increase in high-temperature shrinkage, and the like.

In the composite solid electrolyte layer, the lithium salt can generate a certain degree of dissociation of positive and negative ions in a polymer medium through interaction with a polymer and form a complex through complexation with a polar group of the polymer. In the creeping process of the polymer chain segment, positive and negative ions are continuously dissociated from the original groups and are complexed with the adjacent groups, and the ions can be directionally moved under the action of an external electric field, so that the conduction of the positive and negative ions is realized.

The lithium salt is not particularly limited, and a lithium salt suitable for preparing a lithium ion battery may be used without limitation. For example, the lithium salt may be at least one selected from the group consisting of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium biethanate borate, and lithium oxalyldifluoroborate.

The content of the lithium salt may be 5 to 50 wt%, preferably 10 to 40 wt%, and more preferably 15 to 35 wt%, based on the total weight of the composite solid electrolyte layer. Within the above amount range, the lithium salt may mainly function to conduct ions.

In one embodiment, the weight ratio of lithium salt to organic polymer in the composite solid electrolyte layer is 0.05 to 10:1, preferably 0.3 to 3: 1.

In the composite solid electrolyte layer, the nano inorganic solid electrolyte has the advantages of large specific surface area and high conductivity, can increase the lithium ion transfer capacity, has good high-temperature resistance and processability, and has good application prospect in large-scale power lithium ion batteries with high specific energy.

The nano inorganic solid electrolyte may be at least one selected from Lithium Lanthanum Zirconium Oxide (LLZO), titanium aluminum lithium phosphate (LATP), aluminum lithium germanium phosphorus (LAGP).

The content of the nano inorganic solid electrolyte may be 10 to 85 wt%, preferably 30 to 60 wt%, and more preferably 35 to 45 wt%, based on the total weight of the composite solid electrolyte layer. Within the above quantity range, the nano inorganic solid electrolyte can play a role in conducting lithium ions, the internal resistance of the obtained composite solid electrolyte layer is low, lithium ion loss caused by formation of interface lithium dendrites is reduced, and finally the cycle performance of the solid electrolyte battery is improved. In the case where the nano inorganic solid electrolyte content is less than 10 wt%, the conductivity may be caused to be low. In the case where the nano inorganic solid electrolyte content is more than 85 wt%, it may result in poor mechanical strength of the composite separator, large interfacial resistance upon contact with an electrode active material, and an insufficiently wide electrochemical window.

The particle size of the nano inorganic solid electrolyte, expressed as D50, can be 80-500 nm, preferably 150-250 nm. Within the above quantity range, the nano inorganic solid electrolyte has the advantages of large specific surface area and high conductivity, can increase lithium ion transfer capacity, improve ion conductivity, reduce internal resistance of the obtained composite solid electrolyte layer, reduce lithium ion loss caused by formation of interface lithium dendrite, and finally improve stability and cycle performance of the solid electrolyte battery. When the particle size is less than 80nm, the pore blocking phenomenon of inorganic solid electrolyte particles can be caused, and the particle size is small, the specific surface area is large, the deposition is easy, and the formation of a diaphragm is not facilitated. Under the condition that the particle size is larger than 500nm, the structure stability and the density of the material are possibly caused, and lithium ion migration is not facilitated.

There is no particular limitation on the method for preparing the nano inorganic solid electrolyte as long as it can have the above particle diameter. For example, the submicron inorganic electrolyte can be pulverized by planetary ball milling and/or high-energy ball milling to obtain the nano inorganic solid electrolyte meeting the requirement of particle size.

In the present disclosure, D50 refers to the particle size corresponding to a cumulative distribution of 50% in the particle size distribution curve, and can be measured using a laser particle size tester, such as BetterSize2000 by dandong baite instruments ltd.

In the composite solid electrolyte layer, the wetting agent is used for reducing the surface energy of the slurry, improving the wettability of the slurry and the porous membrane and avoiding the bad phenomena of missing coating and the like. The wetting agent is not particularly limited, and a wetting agent suitable for preparing a coating layer of a positive electrode of a lithium battery may be used without limitation. For example, the wetting agent may be one or more selected from the group consisting of a fluorinated alkyl methoxy alcohol ether, a polyoxyethylene alkylamine, sodium butylnaphthalene sulfonate, sodium arylnaphthalene sulfonate, sodium dodecylbenzene sulfonate, or sodium alkyl sulfate. The content of the wetting agent may be 0.1 to 0.5 wt%, preferably 0.1 to 0.4 wt%, and more preferably 0.15 to 0.3 wt%, based on the total weight of the composite solid electrolyte layer. Within the above quantity range, the wetting agent can play a role in reducing the surface energy of the slurry, and the obtained composite solid electrolyte layer is uniform and has good consistency, so that the solid electrolyte battery has good cycle performance and good adhesion between the coating and the pole piece. When the content of the wetting agent is less than 0.1 wt%, the slurry may explode during the coating process, and the defects such as spot-like or large-area missing coating may occur. In the case of a wetting agent content of more than 0.5 wt%, it may result in a greater increase in the permeability of the coating, which is detrimental to lithium ion cycling.

In the composite solid electrolyte layer, the binder is used for binding the coating material and the porous base membrane, so that the coating is prevented from falling off when the battery is impacted by the outside, and the safety performance of the battery is prevented from being influenced. The binder is not particularly limited, and a binder suitable for preparing a coating layer of a positive electrode of a lithium battery may be used without limitation. For example, the binder may be at least one selected from styrene-butadiene rubber (including styrene-butadiene latex), styrene-acrylic emulsion, polyethylacrylate, polyvinyl alcohol, ethylene-vinyl acetate copolymer, polyvinyl acetate, and polyurethane. The content of the binder may be 1 to 12 wt%, preferably 4 to 10 wt%, more preferably 6 to 9 wt%, based on the total weight of the composite solid electrolyte layer. Within the above quantity range, the binder mainly can play a role in binding the coating and the porous membrane, and the obtained composite solid electrolyte layer has a stable structure, so that the safety performance of the solid electrolyte battery is improved finally. In the case where the binder content is less than 1 wt%, poor adhesion, i.e., "dusting", may result. In the case where the binder content is more than 12 wt%, it may result in a high permeability value of the coating, which is disadvantageous for lithium ion transfer.

Further, the composite solid electrolyte layer may further include additives such as a dispersant (e.g., polyacrylamide, sodium polyacrylate, polyoxyethylene dioleate, etc.), a thickener (e.g., carboxyethyl cellulose, carboxymethyl cellulose (CMC), etc.), and the like, as necessary. The amount of the additive to be used may be determined as needed by those skilled in the art, and is, for example, 0 to 0.3 wt% based on the total weight of the composite solid electrolyte layer.

The solid electrolyte positive electrode according to the present disclosure may further include other layers, for example, an electrospun layer, a thermal closure layer, a nano flame retardant layer.

(1) mixing a nano inorganic solid electrolyte with an organic polymer, a lithium salt, a binder, a wetting agent and a solvent to obtain a composite electrolyte slurry;

(2) and coating the composite electrolyte slurry on the outer surface of the positive active material layer of the positive plate coated with the positive active material layer, and drying to obtain the composite solid electrolyte layer.

In the above step (1), the description of the nano inorganic solid electrolyte, the organic polymer, the lithium salt, the binder and the wetting agent is the same as the foregoing description, and will not be repeated here.

The solvent is not particularly limited as long as the solvent can uniformly disperse the lithium salt, the organic polymer, the inorganic solid electrolyte, the binder and the wetting agent. For example, the solvent may be one or more selected from deionized or distilled water, tetrahydrofuran, cyclohexane, petroleum ether, acetone, Dimethylacetamide (DMAC), N-Dimethylformamide (DMF).

The amount of the solvent used is not particularly limited as long as it enables the resulting composite solid electrolyte layer slurry to be suitable for coating on a positive electrode sheet. In one embodiment, the solvent is used in an amount such that the solids content of the slurry is from 10 to 60 wt%, for example from 15 to 50 wt%, preferably from 20 to 45 wt%.

In the above step (1), there is no particular limitation on the method of mixing the components to prepare the composite electrolyte slurry, as long as the components can be uniformly mixed. For example, stirring may be performed by a planetary stirrer, a homogenizer, or the like.

In the above step (2), there is no particular limitation on the method of applying the composite electrolyte slurry to the outer surface of the positive electrode active material layer as long as a uniform coating layer can be obtained. For example, the coating may be performed by a micro-gravure coating method. After coating, there is no particular limitation on the method of drying the coating layer, as long as the solvent can be removed without adversely affecting the coating layer. For example, drying, vacuum drying, or the like may be employed.

In one embodiment, the step (2) is performed by coating the composite electrolyte slurry on one side or both sides of the positive electrode sheet on which the positive electrode active material layer is formed at a coating speed of 20 to 80m/min, and then drying the positive electrode sheet in an oven at 30 to 60 ℃ to obtain the composite electrolyte coating.

The thickness of the composite solid electrolyte layers is 1 to 100 μm, for example 5 to 60 μm, preferably 10 to 50 μm.

In the above step (2), the description about the positive electrode sheet on which the positive electrode active material layer is formed is the same as the foregoing, and is not repeated here. The method for producing the positive electrode sheet having the positive electrode active material layer formed thereon is not particularly limited, and may be produced by a method known in the art.

In one embodiment, the positive electrode sheet having the positive electrode active material layer formed thereon may be prepared as follows:

1) uniformly mixing a positive active substance, N-methylpyrrolidone (NMP), a binder and a conductive agent to obtain positive active substance slurry,

2) the positive electrode sheet having the positive electrode active material layer formed thereon is obtained by applying the positive electrode active material slurry to one side or both sides of the positive electrode sheet to form the positive electrode active material layer and drying the positive electrode active material layer.

In one embodiment, in the step 1), for example, the positive electrode active material and NMP may be mixed and stirred at a temperature of 25 to 40 ℃, a rotation speed of 500 to 2500rpm/min, and a time of 1 to 3 hours; and then adding a binder and a conductive agent, keeping the temperature at 25-40 ℃, and stirring at 1000-2000 rpm/min for 0.5-2 h to obtain the anode active material slurry.

In the above step 2), there is no particular limitation on the method of applying the positive electrode active material slurry to the positive electrode sheet as long as a uniform coating layer can be obtained. For example, the coating may be performed by a micro-gravure coating method. After coating, there is no particular limitation on the method of drying the coating layer, as long as the solvent can be removed without adversely affecting the coating layer. For example, drying, vacuum drying, or the like may be employed.

The method for preparing a solid electrolyte positive electrode according to the present disclosure may further include operations of preparing an electrostatic spinning layer, a thermal closure layer, a nano flame retardant layer, etc., as necessary. The above-described operations for preparing the electrospun layer, the thermal closure layer, the nano flame-retardant layer, and the like may be performed using conventional operations in the art for preparing such layers.

According to the bookThe disclosed method for preparing the solid electrolyte anode can also carry out operations such as pole piece compression roller, slitting, sheet making and the like according to needs. The operations of pressing, slitting, flaking and the like of the pole piece can be carried out by the conventional operations in the field for preparing the positive electrode, for example, the operations can be carried out according to the compaction density of 3.85g/cm³And carrying out pole piece compression roller.

Yet another aspect of the present disclosure provides a solid-state battery including the above solid-state electrolyte positive electrode.

The solid-state battery may have a structure and components conventional in solid-state batteries in the art, for example, a negative electrode, an aluminum plastic film, and the like, in addition to the above-described solid-state electrolyte positive electrode.

The negative electrode and the aluminum plastic film are not particularly limited, and any negative electrode and aluminum plastic film known in the art to be used for a solid-state battery may be used.

In one embodiment, the negative electrode may include a negative electrode sheet and a negative electrode active material layer formed on the negative electrode sheet.

In one embodiment, the negative electrode sheet is a copper foil and has a thickness of 5 to 20 μm.

The anode active material is not particularly limited as long as it is an active material for an anode commonly used in the art. For example, the negative active material may be one or more selected from artificial graphite and natural graphite.

In one embodiment, the solid-state battery is a solid-state lithium battery.

Further, there is no particular limitation in the structure and assembly method of the solid-state battery, and any structure and assembly method known in the art that can be used for a lithium battery may be employed. For example, the solid-state battery may be assembled into a button battery, a square battery, or the like.

The present disclosure has been described in detail hereinabove, but the above embodiments are merely exemplary in nature and are not intended to limit the present disclosure. Furthermore, there is no intention to be bound by any theory presented in the preceding prior art or the summary or the following examples.

Unless expressly stated otherwise, a numerical range throughout this specification includes any sub-range therein and any numerical value incremented by the smallest sub-unit within a given value. Unless expressly stated otherwise, numerical values throughout this specification represent approximate measures or limitations to the extent that such deviations from the given values, as well as embodiments having approximately the stated values and having the exact values stated, are included. Other than in the operating examples provided at the end of the detailed description, all numbers expressing quantities or conditions of parameters (e.g., quantities or conditions) used in the specification (including the appended claims) are to be understood as being modified in all instances by the term "about" whether or not "about" actually appears before the number. "about" means that the numerical value so stated is allowed to be somewhat imprecise (with some approach to exactness in that value; about or reasonably close to that value; approximately). As used herein, "about" refers to at least variations that can be produced by ordinary methods of measuring and using such parameters, provided that the imprecision provided by "about" is not otherwise understood in the art with this ordinary meaning. For example, "about" can include less than or equal to 10%, less than or equal to 5%, less than or equal to 4%, less than or equal to 3%, less than or equal to 2%, less than or equal to 1%, or less than or equal to 0.5% variation, and in some aspects, less than or equal to 0.1% variation.

Unless otherwise expressly stated, the terms "comprising," "including," "having," "containing," or any other similar term in this specification are intended to be open-ended terms that indicate that a composition or article may include other elements not expressly listed or inherent to such composition or article. Furthermore, in this document, the terms "comprising," including, "" having, "" containing, "and" containing "are to be construed as specifically disclosed and to cover both closed and semi-closed conjunctions, such as" consisting of … "and" consisting essentially of …. By "consisting essentially of …," it is meant that the elements listed herein constitute greater than 95%, greater than 97%, or in some aspects, greater than 99% of the composition or article.

Examples

The technical solution of the present disclosure is further illustrated by the following examples. It should be understood by those skilled in the art that the examples are only for the understanding of the present disclosure and should not be construed as the specific limitations of the present disclosure.

Reagent and apparatus

Unless otherwise indicated, all reagents used are commercially available reagents suitable for use in lithium batteries. Unless otherwise indicated, like terms refer to like materials. Polyvinylidene fluoride was obtained from Dongguan, Heng Plastic materials Ltd. Lithium iron phosphate and lithium manganate were purchased from Guizhou Anda scientific and technological energy resources Co. The ternary cathode material is purchased from Hu nan fir new material Co. The particle size D50 was measured using a laser particle sizer (BetterSize 2000, Inc., Dandong Baite instruments Co., Ltd.).

Preparation of example 1

Preparation of the negative electrode

1) Mixing 32g of natural graphite, 6g of polyvinylidene fluoride and 60g of deionized water, and carrying out planetary stirring at the temperature of 35 ℃ and the rotating speed of 1500rpm/min for 2 h; then 2g of acetylene black is added, the temperature is kept at 35 ℃, and stirring is carried out at 1000rpm/min for 1h, so as to obtain aqueous graphite slurry;

2) and (3) passing the aqueous graphite slurry through a 300-mesh screen, coating the aqueous graphite slurry on one side or two sides of a copper foil to form a graphite coating, and drying the graphite coating, wherein the coating thickness is 20 microns. And rolling, slitting and flaking to obtain the cathode.

Preparation of example 2

Preparation of alumina ceramic diaphragm

Adding 30g of alumina with the particle size of 1 mu m into 200g of deionized water, uniformly stirring, then adding 20g of styrene-butadiene latex with the solid content of 50 wt% as a binder and 1g of polyoxyethylene alkylamine as a wetting agent, and uniformly dispersing by stirring for 2.5h to obtain the ceramic slurry.

Coating the ceramic slurry on a PE (polyethylene) base film with the thickness of 12 mu m, drying in a 50 ℃ oven to obtain an alumina ceramic diaphragm, wherein the thickness of the single ceramic coating is 4 mu m, and the coating weight is 5g/m²。

Example 1

Preparation of lithium iron phosphate-containing positive plate

1) Mixing and stirring 50g of lithium iron phosphate and 130g N-methyl pyrrolidone (NMP) at the temperature of 30 ℃ and the rotation speed of 1500rpm/min for 3 h; then adding 20g of styrene-acrylic emulsion with the solid content of 50 wt% and 6g of carbon fiber, keeping the temperature at 30 ℃, and stirring at 1000rpm/min for 1.5h to obtain composite anode slurry;

2) and coating the composite anode slurry on one side or two sides of an aluminum foil with the thickness of 10 mu m, and then drying to obtain a single-coating with the thickness of 42 mu m, thereby obtaining the anode plate containing the lithium iron phosphate.

Preparing a nano inorganic solid electrolyte:

and the submicron-sized LLZO is crushed by planetary ball milling and high-energy ball milling to obtain the nano-sized LLZO with the particle size D50 of 210 nm.

Preparing a solid electrolyte anode:

20g of polyoxyethylene as an organic polymer and 6.85g of polyvinyl acetate as a binder were uniformly dispersed in 150ml of DMAC, and then lithium hexafluorophosphate (30g) and nano-LLZO (35g) prepared as described above were further added, and finally 0.15g of polyoxyethylene alkylamine as a wetting agent was added to the mixture and mixed in a 1L reactor for 3 hours to obtain a composite electrolyte slurry.

Coating the composite electrolyte slurry on one side or two sides of the prepared lithium iron phosphate-containing positive plate, and performing vacuum drying at 120 ℃ for 48 hours to obtain a composite solid electrolyte layer, wherein the thickness of the final coating is 40 mu m; then the pressed solid density is 3.85g/cm³And rolling, slitting and flaking to obtain the solid electrolyte anode.

Preparation of solid-state batteries:

the solid electrolyte anode, the prepared alumina ceramic diaphragm and the prepared cathode are sequentially wound by 10 layers to form a lithium ion square solid battery cell, and the lithium ion square solid battery cell is placed into a shell and injected with liquid (containing 1mol/L LiPF)₆The organic electrolytic solution of (1), wherein the solvent is dimethyl carbonate: diethyl carbonate: propylene carbonate 1:1:1), sealing, and forming to obtain the solid battery.

Example 2

Preparation of positive plate containing lithium manganese oxide

1) Mixing and stirring 50g of lithium manganate and 130g N-methyl pyrrolidone (NMP), wherein the temperature is 30 ℃, the rotating speed is 1500rpm/min, and the time is 3 h; then adding 20g of styrene-acrylic emulsion with the solid content of 50 wt% and 6g of carbon fiber, keeping the temperature at 30 ℃, and stirring at 1000rpm/min for 1.5h to obtain composite anode slurry;

2) and coating the composite anode slurry on one side or two sides of an aluminum foil with the thickness of 10 mu m, drying, and coating the single coating with the thickness of 42 mu m to obtain the lithium manganese oxide-containing anode sheet.

Preparing a nano inorganic solid electrolyte:

and the submicron-level LLZO is subjected to planetary ball milling and high-energy ball milling to obtain the nano-level LLZO with the particle size D50 of 240 nm.

Preparing a solid electrolyte anode:

20g of polyvinylidene fluoride as an organic polymer and 6.85g of polyvinyl acetate as a binder were uniformly dispersed in 150ml of N, N-dimethylformamide, and then lithium hexafluorophosphate (30g) and nano-LLZO (35g) were continuously added, followed by adding 0.2g of polyoxyethylene alkylamine as a wetting agent and mixing and stirring for 3 hours in a 1L reaction vessel to obtain a composite electrolyte slurry.

Coating the composite electrolyte slurry on one side or two sides of a positive plate containing lithium manganese oxide, and performing vacuum drying at 120 ℃ for 48 hours to obtain a composite solid electrolyte layer, wherein the thickness of the final single coating is 35 mu m; then the pressed solid density is 3.85g/cm³And rolling, slitting and flaking to obtain the solid electrolyte anode.

Preparation of solid-state batteries:

the solid electrolyte anode, the prepared alumina ceramic diaphragm and the prepared cathode are sequentially wound by 10 layers to prepare a lithium ion square solid battery cell, and the lithium ion square solid battery cell is placed into a shell and injected with liquid (containing 1mol/L LiPF)₆The organic electrolytic solution of (1), wherein the solvent is dimethyl carbonate: diethyl carbonate: propylene carbonate 1:1:1), sealing, and forming to obtain the solid battery.

Example 3

Preparation of positive plate containing ternary positive material

1) Mixing and stirring 50g of ternary cathode material and 130g N-methyl pyrrolidone (NMP), wherein the temperature is 30 ℃, the rotating speed is 1500rpm/min, and the time is 3 h; then adding 20g of styrene-acrylic emulsion with the solid content of 50 wt% and 6g of carbon fiber, keeping the temperature at 30 ℃, and stirring at 1000rpm/min for 1.5h to obtain composite anode slurry;

2) and coating the composite anode slurry on one side or two sides of an aluminum foil with the thickness of 10 mu m, and then drying to obtain a single-coating thickness of 42 mu m, thereby obtaining the anode plate containing the ternary anode material.

Preparing a nano inorganic solid electrolyte:

the submicron LATP is pulverized by planetary ball milling and high-energy ball milling to obtain the nanometer LATP, and the particle size D50 is 200 nm.

Preparing a solid electrolyte anode:

20g of polyethylene carbonate as an organic polymer and 6.85g of polyvinyl acetate as a binder were uniformly dispersed in 150ml of N, N-dimethylformamide, and then lithium hexafluorophosphate (30g) and nano-LLZO (35g) were further added, followed by adding 0.2g of polyoxyethylenealkylamine as a wetting agent and mixing and stirring for 3 hours in a 1L reaction vessel to obtain a composite electrolyte slurry.

Coating the composite electrolyte slurry on one side or two sides of a positive plate containing the ternary positive material, and performing vacuum drying at 150 ℃ for 24 hours to obtain a composite solid electrolyte layer, wherein the thickness of the final single coating is 35 mu m; then the pressed solid density is 3.85g/cm³And rolling, slitting and flaking to obtain the solid electrolyte anode.

Preparation of solid-state batteries:

Comparative example 1

Preparation of the Battery

The lithium iron phosphate-containing positive electrode sheet of example 1, the alumina ceramic separator, and the negative electrode prepared as described above were wound in this order into 10 layers to form a prismatic aluminum-can battery.

Then the battery is dried in vacuum and vacuumized to remove water, and electrolyte (containing 1mol/L LiPF) is injected into the shell₆Wherein the solvent is carbonic acidDimethyl ester: diethyl carbonate: 1:1:1) and sealing. And obtaining the organic solution lithium ion battery.

Examples of the experiments

The batteries of examples 1-3 and comparative example 1 (including 5 cells) were extracted and subjected to cycle performance testing after full charge. The lithium ion battery is charged at normal temperature by adopting 1C multiplying power, discharged at 1C multiplying power, and sequentially circulated for 500 times, and the battery capacity before and after each circulation is recorded (5 battery data average values are taken in each group).

The capacity retention ratio after n cycles is (battery capacity after n cycles/battery capacity before cycles) × 100%.

The results of capacity retention after 500 cycles are shown in table 1:

TABLE 1500 Capacity Retention (% after cycles)

Item	Example 1	Example 2	Example 3	Comparative example 1
					Capacity retention ratio%	94.32％	93.86％	94.66％	89.79％

The results in table 1 show that the batteries of examples 1 to 3 have high capacity retention rate, and may reduce the irreversible loss of lithium ions during the cycle process, have high ionic conductivity, reduce the influence of shuttle effect, and avoid the formation of lithium dendrites. The capacity retention rate of the battery in the comparative example 1 is low, probably because the ion conduction rate of the compact ceramic coating is poor, lithium ions are easily enriched in the current charging and discharging process, the conductivity of the anode material is relatively poor, the whole ion conduction internal resistance is high, and the ion loss caused by the formation of lithium ion dendrites is easily caused. Is not favorable for the cycle performance of the lithium ion battery.

Claims

1. A solid electrolyte cathode, comprising:

a composite solid electrolyte layer formed on the outer surface of the positive electrode active material layer and having a thickness of 1 to 100 μm,

the composite solid electrolyte layer comprises an organic polymer, a lithium salt, a nano inorganic solid electrolyte, a binder and a wetting agent, wherein based on the total weight of the composite solid electrolyte layer, the content of the organic polymer is 5-80 wt%, the content of the lithium salt is 5-50%, the content of the nano inorganic solid electrolyte is 10-85 wt%, the content of the binder is 1-12 wt%, and the content of the wetting agent is 0.1-0.5 wt%,

the organic polymer is at least one selected from polyoxyethylene, polyvinylidene fluoride-hexafluoropropylene and polyethylene carbonate;

the lithium salt is at least one selected from lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis (oxalato) borate and lithium oxalato difluoro borate;

the nano inorganic solid electrolyte is at least one selected from lithium lanthanum zirconium oxide, titanium aluminum lithium phosphate and aluminum lithium germanium phosphorus;

the wetting agent is one or more selected from fluoroalkyl methoxy alcohol ether, polyoxyethylene alkylamine, sodium butylnaphthalene sulfonate, sodium aryl naphthalene sulfonate, sodium dodecyl benzene sulfonate or sodium alkyl sulfate;

the binder is at least one selected from styrene butadiene rubber, styrene-acrylic emulsion, polyethylacrylate, polyvinyl alcohol, ethylene-vinyl acetate copolymer, polyvinyl acetate and polyurethane,

wherein the particle size of the nano inorganic solid electrolyte is 80-500 nm as represented by D50.

2. The solid electrolyte cathode according to claim 1, wherein the composite solid electrolyte layer has a thickness of 5 to 60 μm.

3. The solid electrolyte positive electrode according to claim 1, wherein the composite solid electrolyte layer has a thickness of 10 to 50 μm.

4. The solid electrolyte positive electrode according to claim 1, wherein the nano inorganic solid electrolyte has a particle size, expressed as D50, of 150 to 250 nm.

5. The solid electrolyte cathode according to claim 1, wherein the electrolyte layer comprises, based on the total weight of the composite solid electrolyte layer,

the content of the organic polymer is 15-45 wt%; and/or

The content of the lithium salt is 10-40 wt%; and/or

The content of the nano inorganic solid electrolyte is 30-60 wt%; and/or

The content of the wetting agent is 0.1-0.4 wt%; and/or

The content of the binder is 4-10 wt%.

6. The solid electrolyte cathode according to claim 1, wherein the electrolyte layer comprises, based on the total weight of the composite solid electrolyte layer,

the content of the organic polymer is 20-35 wt%; and/or

The content of the lithium salt is 15-35 wt%; and/or

The content of the nano inorganic solid electrolyte is 35-45 wt%; and/or

The content of the wetting agent is 0.15-0.3 wt%.

7. The solid electrolyte positive electrode according to claim 1, wherein a weight ratio of the lithium salt to the organic polymer in the composite solid electrolyte layer is 0.05 to 10: 1.

8. The solid-state electrolyte positive electrode according to claim 1,

the positive electrode active material layer is formed on one surface or two surfaces of the positive electrode sheet, and the thickness of each positive electrode active material layer is 0.5-50 mu m independently; and/or

The positive plate is an aluminum foil, and the thickness of the positive plate is 8-15 mu m; and/or

The positive electrode active material layer comprises a positive electrode active material, a conductive agent and a binder, wherein the content of the positive electrode active material is 50-95% based on the total weight of the positive electrode active material layer; the content of the conductive agent is 1-20%; the content of the binder is 2-30%.

9. The solid electrolyte positive electrode according to claim 8, wherein the content of the positive electrode active material is 60 to 85% based on the total weight of the positive electrode active material layer; the content of the conductive agent is 5-15%; the content of the binder is 10-25%.

10. The solid-state electrolyte positive electrode according to claim 8 or 9,

the positive active material is one or more selected from lithium manganate, lithium cobaltate, lithium iron phosphate and ternary positive materials; and/or

The conductive agent is one or more selected from acetylene black, conductive carbon black, carbon fiber and graphene; and/or

The binder is at least one selected from polyvinylidene fluoride, styrene butadiene rubber, styrene-acrylic emulsion, acrylic resin, polyacrylonitrile and sodium carboxymethylcellulose.

11. A method of making a solid state electrolyte cathode of any one of claims 1-10, comprising:

12. The method of claim 11, wherein,

the solvent is one or more selected from deionized water or distilled water, tetrahydrofuran, cyclohexane, petroleum ether, acetone, dimethylacetamide and N, N-dimethylformamide;

the solvent is used in an amount such that the solid content of the composite electrolyte slurry is 10 to 60 wt%.

13. The method according to claim 12, wherein the solvent is used in an amount such that the solid content of the composite electrolyte slurry is 15 to 50 wt%.

14. The method according to claim 12, wherein the solvent is used in an amount such that the solid content of the composite electrolyte slurry is 20 to 45 wt%.

15. A solid-state battery comprising the solid-state electrolyte positive electrode of any one of claims 1 to 10.

16. The solid-state battery according to claim 15, which is a solid-state lithium battery.