阅读说明：本技术 一种用于固态锂电池的补锂功能电解质膜的制备方法 (Preparation method of electrolyte membrane with lithium supplementing function for solid lithium battery ) 是由 林久 许晓雄 杨杰 楼凯 崔言明 张永龙 戈志敏 于 2021-08-12 设计创作，主要内容包括：本发明公开了一种用于固态锂电池的补锂功能电解质膜的制备方法,步骤如下：S1、将含锂化合物和无机固态电解质分别分散在NMP中,制备含锂化合物分散液和无机固态电解质分散液；将粘结剂搅拌溶解于NMP中,制备粘结剂溶液；S2、将含锂化合物分散液和无机固态电解质分散液按质量比混合,并向其中加入导电剂,制备得到混合分散液；S3、向步骤S2中得到的混合分散液中加入步骤S1中得到的粘结剂溶液,球磨混合后得到均匀浆料；S4、将均匀浆料通过双放卷的模式同时涂覆在增强层和骨架层相对的一侧表面,并在涂布机的烘箱中进行烘干,进而于增强层和骨架层之间形成补锂电解质层,从而得到用于固态锂电池的补锂功能电解质膜。制备得到的电解质膜1C循环性能提升50％以上。(The invention discloses a preparation method of an electrolyte membrane with a lithium supplementing function for a solid-state lithium battery, which comprises the following steps: s1, respectively dispersing the lithium-containing compound and the inorganic solid electrolyte in NMP to prepare a lithium-containing compound dispersion liquid and an inorganic solid electrolyte dispersion liquid; stirring and dissolving a binder in NMP to prepare a binder solution; s2, mixing the lithium-containing compound dispersion liquid and the inorganic solid electrolyte dispersion liquid according to the mass ratio, and adding a conductive agent into the mixture to prepare a mixed dispersion liquid; s3, adding the binder solution obtained in the step S1 into the mixed dispersion liquid obtained in the step S2, and performing ball milling and mixing to obtain uniform slurry; and S4, simultaneously coating the uniform slurry on the surface of one side, opposite to the reinforcing layer and the framework layer, of the reinforcing layer in a double-unwinding mode, drying the uniform slurry in a drying oven of a coating machine, and further forming a lithium supplement electrolyte layer between the reinforcing layer and the framework layer, so that the lithium supplement functional electrolyte membrane for the solid lithium battery is obtained. The 1C cycle performance of the prepared electrolyte membrane is improved by more than 50%.)

1. A preparation method of an electrolyte membrane with a lithium supplementing function for a solid lithium battery is characterized by comprising the following steps: the method comprises the following specific steps:

s1, respectively weighing a lithium-containing compound, an inorganic solid electrolyte, a binder and a conductive agent, respectively dispersing the weighed lithium-containing compound and the weighed inorganic solid electrolyte in NMP, and respectively preparing a lithium-containing compound dispersion liquid and an inorganic solid electrolyte dispersion liquid by ball milling; simultaneously stirring and dissolving the weighed binder in NMP to prepare a binder solution;

s2, mixing the lithium-containing compound dispersion liquid and the inorganic solid electrolyte dispersion liquid according to the mass ratio, adding a conductive agent into the mixture, and continuously performing ball milling dispersion and mixing to prepare a mixed dispersion liquid;

s3, adding the binder solution obtained in the step S1 into the mixed dispersion liquid obtained in the step S2, and performing ball milling and mixing to obtain uniform slurry;

and S4, simultaneously coating the uniform slurry obtained in the step S3 on the surface of one side, opposite to the reinforcing layer and the framework layer, of the reinforcing layer through a double-unwinding mode, drying the uniform slurry in an oven of a coating machine, and further forming a lithium-supplement electrolyte layer between the reinforcing layer and the framework layer, so that the lithium-supplement functional electrolyte membrane for the solid lithium battery is obtained.

2. The method for producing a lithium replenishing function electrolyte membrane for a solid lithium battery as claimed in claim 1, characterized in that: the content of the lithium-containing compound in the lithium-supplement electrolyte layer obtained in the step S4 is 10% to 45%, the content of the inorganic solid electrolyte particles is 50% to 80%, the content of the binder is 3.5% to 10%, and the content of the conductive agent is 0.5% to 2%.

3. The method for producing a lithium replenishing function electrolyte membrane for a solid lithium battery as claimed in claim 1, characterized in that: in the step S1, the binder was dissolved in NMP with stirring at a solid content of 10%, to prepare a binder solution.

4. The method for producing a lithium replenishing function electrolyte membrane for a solid lithium battery as claimed in claim 1, characterized in that: after ball milling in the step S1, the particle size of the lithium-containing compound is 0.1 μm to 2 μm.

5. The method for producing a lithium replenishing function electrolyte membrane for a solid lithium battery as claimed in claim 1, characterized in that: after ball milling in the step S1, the particle size of the inorganic solid electrolyte is 0.1-2 μm.

6. The method for producing a lithium replenishing functional electrolyte membrane for a solid lithium battery as claimed in any one of claims 1 to 5, wherein: the lithium-containing compound in step S1 includes at least one of lithium iron oxide, lithium nickel oxide, lithium cobalt oxide, organic lithium salt, lithium oxide, lithium sulfide, lithium phosphide, and lithium nitride.

7. According to claimThe method for producing an electrolyte membrane having a lithium replenishing function for a solid lithium battery according to claim 6, characterized by comprising: the lithium-containing compound in step S1 is Li₅FeO₄、Li₅Fe₅O₈、Li₆CoO₄、Li₂NiO₂、Li₂O、Li₂S、Li₃P、Li₃N、Li₂O₂、Li₂C₂O₄、Li₂At least one of DHBN.

8. The method for producing a lithium replenishing functional electrolyte membrane for a solid lithium battery as claimed in any one of claims 1 to 5, wherein:

the inorganic solid electrolyte particles in step S1 have a NASICON type structure and a chemical formula of LiM₂(PO₄)₃、Li_1+xAl_xTi_2-x(PO₄)₃And Li_1+xAl_xGe_2-x(PO₄)₃Wherein M is one of Ti, Ge and Hf, and 0 < x < 2;

or the inorganic solid electrolyte particles are in a perovskite structure, and the chemical formula of the inorganic solid electrolyte particles is Li_0.34La_0.56TiO₃And/or Li_0.5La_0.5TiO₃；

Or the inorganic solid electrolyte particles are of a LISICON type structure, and the chemical formula of the inorganic solid electrolyte particles is Li₁₄Zn(GeO₄)₄；

Or the inorganic solid electrolyte particles have a garnet structure and have a chemical formula of Li₅La₃R₂O₁₂、Li₆ALa₂R₂O₁₂、Li_5.5La₃R_1.75D_0.25O₁₂、Li₇La₃Zr₂O₁₂And Li_7.06E₃Y_0.06Zr_1.94O₁₂Wherein R isNb or Ta, A is one of Ca, Sr and Ba, D is In or Zr, and E is one of La, Nb and Ta;

or the inorganic solid electrolyte particles are of an anti-perovskite structure, and the chemical formula of the inorganic solid electrolyte particles is Li₃OX, wherein X is F, Cl or Br;

or the inorganic solid electrolyte particles are in a glass state or a glass ceramic state, and the inorganic solid electrolyte particles are sulfide Li₁₀GeP₂S₁₂、Li₂S-SiS₂、Li₂S-P₂S₅、70Li₂S-30P₂S₅One or more of (a).

9. The method for producing a lithium replenishing functional electrolyte membrane for a solid lithium battery as claimed in any one of claims 1 to 5, wherein: the binder in the step S1 is at least one of PVDF, PVDF-HFP, PVP, PEO, PAN, EVA and PMMA;

the conductive agent in the step S2 is one or more of Super-P, Ketjen black, CNTs and graphene;

the skeleton layer in the step S4 is a three-dimensional porous nonwoven film, and the skeleton layer includes a first polymer base material, and the first polymer base material is one of cellulose, PET, PI, PVDF, PA, and PVC;

the reinforcing layer in step S4 includes a second polymer substrate, and the second polymer substrate is one of PE, PP, and PE/PP/PE.

10. The method for producing a lithium replenishing function electrolyte membrane for a solid lithium battery as claimed in claim 1, characterized in that: the temperature of the oven in the step S4 is 60-80 ℃.

Technical Field

The invention belongs to the technical field of lithium batteries, and particularly relates to a preparation method of an electrolyte membrane with a lithium supplementing function for a solid-state lithium battery.

Background

The lithium ion battery has the advantages of high energy density, long cycle life and the like, and is widely applied to the fields of portable electronic products, electric automobiles and the like. In the first charging process of the lithium ion battery, an SEI film is formed on the surface of a negative electrode, active lithium in a positive electrode is consumed, irreversible capacity loss is caused, the irreversible capacity loss of the graphite negative electrode which is most widely used at present can reach 10%, and the irreversible capacity loss of silicon-based and tin-based negative electrodes with high specific capacity can even reach more than 30%, so that the energy density of the lithium ion battery is greatly reduced. For this problem, it is currently acknowledged in academia and industry that the irreversible loss of lithium ions is compensated by a lithium supplementing method, so that the capacity of the positive electrode can be recovered, and the energy density of the lithium ion battery is greatly improved.

From the technical path, the currently mainstream lithium supplement schemes can be divided into three main categories: 1) the negative pole is supplemented with lithium, mainly inert metal lithium powder and metal lithium foil, and the lithium is supplemented by vacuum winding and evaporation; 2) the positive electrode being lithium-supplemented, primarily by some lithium-containing oxides, e.g. Li₅FeO₄Etc.; 3) and (3) lithium is supplemented by the third electrode, and the purpose of lithium supplementation is achieved by charging and discharging between the negative electrode and the third electrode (such as a metal lithium electrode and a high-capacity lithium-containing oxide electrode).

The lithium is supplemented by the metal lithium in the negative electrode, so that the lithium supplementing efficiency is high, no residue is left after reaction, but the activity of the metal lithium is very high, the requirement on environmental control is high, large-scale equipment is required, the cost investment is large, and the influence on the existing production process is large. Meanwhile, the adoption of the lithium metal also has a great safety risk, and particularly, the lithium metal powder is suspended in the air and can cause the risks of dust explosion and the like. Meanwhile, if the lithium supplement is insufficient, the energy density is not obviously improved; if lithium is excessively supplied, a lithium metal plating layer is formed on the surface of the negative electrode, and the battery performance is impaired.

The lithium supplement of the positive electrode has the advantages of simple process, low price, high safety and the like, and has attracted wide attention in recent years. Patent CN110120493A provides a positive electrode lithium-supplementing method for preparing a smear by pulping a lithium-supplementing material, a positive electrode material, a conductive agent and a binder together, but in this method, a lithium-supplementing sacrificial agent has a certain influence on the mass transfer inside the whole pole piece after the lithium-removing decomposition of the positive electrode side. Patent CN109755448A will contain Li₅FeO₄The lithium supplementing coating containing the lithium compound, the nano inert inorganic filler and the binder is coated on the diaphragm substrate to prepare the lithium battery diaphragm with the lithium supplementing coating, the heat shrinkage of the diaphragm is reduced while the lithium is supplemented, but the bonding between the lithium supplementing layer and the diaphragm substrate can be influenced after the lithium supplementing agent is removed, and the lithium supplementing efficiency is reduced after the lithium supplementing agent is removed into the electrolyte.

Therefore, it is important to develop lithium batteries to provide an electrolyte membrane with lithium supplementing function for solid lithium batteries, which has high-efficiency and controllable lithium supplementing effect, prolongs the battery cycle life, and has better temperature resistance.

Disclosure of Invention

The invention aims to provide a preparation method of an electrolyte membrane with a lithium supplementing function for a solid lithium battery, which can effectively solve the problems that a lithium supplementing diaphragm in the prior art is poor in temperature resistance and a lithium supplementing layer can fall off into an electrolyte.

The technical scheme adopted by the invention for solving the technical problems is as follows:

a preparation method of an electrolyte membrane with a lithium supplementing function for a solid lithium battery comprises the following specific steps:

s1, respectively weighing a lithium-containing compound, an inorganic solid electrolyte, a binder and a conductive agent, respectively dispersing the weighed lithium-containing compound and the weighed inorganic solid electrolyte in NMP, and respectively preparing a lithium-containing compound dispersion liquid and an inorganic solid electrolyte dispersion liquid by ball milling; simultaneously, stirring and dissolving the weighed adhesive in NMP to prepare an adhesive solution;

s2, mixing the lithium-containing compound dispersion liquid and the inorganic solid electrolyte dispersion liquid according to the mass ratio, adding a conductive agent into the mixture, and continuously performing ball milling dispersion and mixing to prepare a mixed dispersion liquid;

s3, adding the binder solution obtained in the step S1 into the mixed dispersion liquid obtained in the step S2, and performing ball milling and mixing to obtain uniform slurry;

and S4, simultaneously coating the uniform slurry obtained in the step S3 on the surface of one side of the reinforcing layer opposite to the framework layer through a double-unwinding mode, drying the uniform slurry in an oven of a coating machine, and further forming a lithium-supplement electrolyte layer between the reinforcing layer and the framework layer, so that the lithium-supplement functional electrolyte membrane for the solid lithium battery is obtained.

Preferably, the content of the lithium-containing compound in the lithium-supplement electrolyte layer obtained in step S4 is 10% to 45%, the content of the inorganic solid electrolyte particles is 50% to 80%, the content of the binder is 3.5% to 10%, and the content of the conductive agent is 0.5% to 2%.

Preferably, the binder is dissolved in NMP with stirring at 10% solid content in the step S1 to prepare a binder solution.

Preferably, the lithium-containing compound has a particle size of 0.1 to 2 μm after ball milling in step S1.

Preferably, the particle size of the inorganic solid electrolyte after ball milling in step S1 is 0.1 to 2 μm.

Preferably, the lithium-containing compound in step S1 includes at least one of lithium iron oxide, lithium nickel oxide, lithium cobalt oxide, organic lithium salt, lithium oxide, lithium sulfide, lithium phosphide, and lithium nitride.

Preferably, the lithium-containing compound in step S1 is Li₅FeO₄、Li₅Fe₅O₈、Li₆CoO₄、 Li₂NiO₂、Li₂O、Li₂S、Li₃P、Li₃N、Li₂O₂、Li₂C₂O₄、Li₂At least one of DHBN

Preferably, the inorganic solid electrolyte particles in step S1 have a NASICON-type structure, and the chemical formula of the inorganic solid electrolyte particles is LiM₂(PO₄)₃、Li_1+xAl_xTi_2-x(PO₄)₃And Li_1+xAl_xGe_2-x(PO₄)₃Wherein M is one of Ti, Ge and Hf, and 0 < x < 2;

or the inorganic solid electrolyte particles are in a perovskite structure, and the chemical formula of the inorganic solid electrolyte particles is Li_0.34La_0.56TiO₃And/or Li_0.5La_0.5TiO₃；

Or the inorganic solid electrolyte particles are of a LISICON type structure, and the chemical formula of the inorganic solid electrolyte particles is Li₁₄Zn(GeO₄)₄；

Or the inorganic solid electrolyte particles have a garnet structure and have a chemical formula of Li₅La₃R₂O₁₂、Li₆ALa₂R₂O₁₂、Li_5.5La₃R_1.75D_0.25O₁₂、Li₇La₃Zr₂O₁₂And Li_7.06E₃Y_0.06Zr_1.94O₁₂Wherein, R is Nb or Ta, A is one of Ca, Sr and Ba, D is In or Zr, and E is one of La, Nb and Ta;

or the inorganic solid electrolyte particles are of an anti-perovskite structure, and the chemical formula of the inorganic solid electrolyte particles is Li₃OX, wherein X is F, Cl or Br;

or the inorganic solid electrolyte particles are in a glassy stateOr a glass-ceramic state, the inorganic solid electrolyte particles being sulfide Li₁₀GeP₂S₁₂、Li₂S-SiS₂、Li₂S-P₂S₅、 70Li₂S-30P₂S₅One or more of (a).

Preferably, the binder in step S1 is at least one of PVDF, PVDF-HFP, PVP, PEO, PAN, EVA, and PMMA;

the conductive agent in the step S2 is one or more of Super-P, Ketjen black, CNTs and graphene;

the skeleton layer in the step S4 is a three-dimensional porous nonwoven film, and the skeleton layer includes a first polymer base material, and the first polymer base material is one of cellulose, PET, PI, PVDF, PA, and PVC;

the reinforcing layer in step S4 includes a second polymer substrate, and the second polymer substrate is one of PE, PP, and PE/PP/PE.

Preferably, the temperature of the oven in the step S4 is 60 to 80 ℃.

Compared with the prior art, the preparation method of the electrolyte membrane with the lithium supplementing function for the solid lithium battery can prepare the electrolyte membrane with the lithium supplementing function for the solid lithium battery, and the lithium-containing compound in the electrolyte membrane can be used for extracting more lithium ions in the battery charging process and participating in forming an SEI layer, so that the loss of the lithium ions in the positive active material is reduced, more lithium ions can be ensured to be inserted and extracted, the discharge capacity of the lithium battery is improved, and the charge-discharge cycle life of the lithium battery can be prolonged; the electrolyte membrane prepared by the method has obviously improved safety performance and can pass a needling test.

Drawings

FIG. 1 is an electron micrograph of a surface of a lithium-doped electrolyte layer according to the present example;

fig. 2 is a cycle life curve in the 1C (1C ═ 5A) charge-discharge mode in this example;

FIG. 3 is a photograph of the present example (example 1, comparative example 1 and comparative example 2, respectively, from top to bottom) before heat treatment at 180 ℃;

FIG. 4 is a photograph showing the heat treatment at 180 ℃ for 1 hour in this example (example 1, comparative example 1 and comparative example 2, respectively, from the top).

Detailed Description

The invention is described in further detail below with reference to the accompanying examples.

The electrolyte membrane consists of a framework layer, a reinforcing layer and a lithium-supplementing electrolyte layer positioned between the framework layer and the reinforcing layer, wherein the framework layer has a three-dimensional porous structure, and part of the lithium-supplementing electrolyte layer is filled in the porous structure of the framework layer.

Lithium ions are extracted in the battery charging and discharging process through the lithium supplementing electrolyte layer, the lithium ions participate in forming the SEI layer, the loss of the lithium ions in the positive active material is reduced, the lithium supplementing electrolyte layer is located between the framework layer and the enhancement layer, even if the structure of the lithium supplementing electrolyte layer is changed due to lithium removal in the lithium supplementing process, the lithium supplementing electrolyte layer cannot fall into electrolyte due to falling, and the lithium supplementing effect is guaranteed.

And the arrangement of the reinforced layer enables the overall mechanical strength of the membrane to be higher. Experiments show that the inorganic electrolyte layer is arranged on one side of the framework layer, the mechanical strength of the lithium-supplement electrolyte membrane obtained by arranging the composite electrolyte layer on the other side is only 50Mpa at most, the lithium-supplement electrolyte layer of the lithium-supplement function electrolyte membrane for the solid lithium battery in the embodiment is filled in the framework layer and between the framework layer and the reinforcing layer, the framework layer and the reinforcing layer are tightly bonded through the lithium-supplement electrolyte layer, and the integral mechanical strength of the membrane is greater than 100Mpa, so that the whole membrane can meet the strength specification of equipment pulling in the manufacturing process of the battery cell, and meanwhile, the tests of the safety performances of the follow-up battery cell, such as heavy object impact resistance and the like, can be met.

Specifically, the lithium-supplement electrolyte layer includes a lithium-containing compound, inorganic solid electrolyte particles, a binder, and a conductive agent.

The lithium-containing compound in the lithium supplement functional electrolyte membrane for the solid lithium battery can be used for releasing and inserting more lithium ions in the battery charging process to participate in the formation of an SEI layer, so that the loss of the lithium ions in the positive active material is reduced, more lithium ions can be ensured to participate in the insertion and release, the discharge capacity of the lithium battery is improved, and the charge-discharge cycle life of the lithium battery can be prolonged.

The content of the lithium-containing compound is 10-45%, the content of the inorganic solid electrolyte particles is 50-80%, the content of the binder is 3.5-10%, and the content of the conductive agent is 0.5-2%.

The lithium-containing compound is a lithium-containing compound having a high irreversible capacity in a certain voltage range, and includes at least one of lithium iron oxide, lithium nickel oxide, lithium cobalt oxide, organic lithium salt, lithium oxide, lithium sulfide, lithium phosphide, and lithium nitride.

Specifically, the lithium-containing compound is Li₅FeO₄、Li₅Fe₅O₈、Li₆CoO₄、Li₂NiO₂、Li₂O、 Li₂S、Li₃P、Li₃N、Li₂O₂、Li₂C₂O₄、Li₂At least one of DHBN.

The activity of the lithium-containing compound increases with the decrease of the particle size, and the lithium-containing compound is more likely to react with moisture, a binder and a solution in the environment, so that the slurry gel is accelerated. The large-particle lithium-containing compound has poor dynamics, so that the lithium supplementing efficiency is reduced, the particle size of the lithium-containing compound is moderate, and the particle size of the lithium-containing compound is preferably 0.1-2 mu m, so that the stability of the slurry can be improved, the exertion of the lithium supplementing efficiency can be facilitated, and the energy density and the electrochemical performance of the battery can be further improved.

The inorganic solid electrolyte particles have NASICON type structure, and the chemical formula of the inorganic solid electrolyte particles is LiM₂(PO₄)₃、Li_1+xAl_xTi_2-x(PO₄)₃(LATP) and Li_1+xAl_xGe_2-x(PO₄)₃(LAGP), wherein M is one of Ti, Ge and Hf, and 0 < x < 2;

or the inorganic solid electrolyte particles are calciumTitanium ore type structure, inorganic solid electrolyte particle with chemical formula of Li_0.34La_0.56TiO₃And/or Li_0.5La_0.5TiO₃；

Or the inorganic solid electrolyte particles are of a LISICON type structure and have a chemical formula of Li₁₄Zn(GeO₄)₄；

Or the inorganic solid electrolyte particles have a garnet structure and have a chemical formula of Li₅La₃R₂O₁₂、Li₆ALa₂R₂O₁₂、Li_5.5La₃R_1.75D_0.25O₁₂、Li₇La₃Zr₂O₁₂And Li_7.06E₃Y_0.06Zr_1.94O₁₂Wherein, R is Nb or Ta, A is one of Ca, Sr and Ba, D is In or Zr, and E is one of La, Nb and Ta;

or the inorganic solid electrolyte particles are of an anti-perovskite structure, and the chemical formula of the inorganic solid electrolyte particles is Li₃OX, X is F, Cl or Br;

or the inorganic solid electrolyte particles are in a glass state or a glass ceramic state, and the inorganic solid electrolyte particles are sulfide Li₁₀GeP₂S₁₂、Li₂S-SiS₂、Li₂S-P₂S₅、70Li₂S-30P₂S₅One or more of (a).

The particle size of the inorganic solid electrolyte particles is 0.1 to 2 μm so as to match the particle size of the lithium-containing compound and facilitate coating.

The binder is at least one of PVDF, PVDF-HFP, PVP, PEO, PAN, EVA and PMMA.

The conductive agent is one or more of Super-P, Ketjen black, CNTs and graphene.

The framework layer is a three-dimensional porous non-woven membrane and comprises a first polymer base material, and the first polymer base material is one of cellulose, PET, PI, PVDF, PA and PVC.

The reinforced layer comprises a second polymer substrate, and the second polymer substrate is one of PE, PP and PE/PP/PE.

Compared with the prior art, the lithium-containing compound in the lithium-supplementing functional electrolyte membrane for the solid lithium battery can be used for extracting more lithium ions in the battery charging process and participating in forming an SEI layer, so that the loss of the lithium ions in the positive active material is reduced, more lithium ions can be ensured to be extracted and inserted, the discharge capacity of the lithium battery is improved, and the charge-discharge cycle life of the lithium battery can be prolonged.

The lithium supplement electrolyte layer is filled in the framework layer and between the framework layer and the enhancement layer, and the framework layer and the enhancement layer are tightly bonded through the lithium supplement electrolyte layer, so that good lithium supplement can be realized, and the problem that the lithium supplement effect is influenced because a lithium supplement agent is separated in the lithium supplement process to cause the electrolyte layer to fall into the electrolyte can be avoided; the setting of enhancement layer makes the whole mechanical strength of membrane be far more than only having the skeleton layer and set up the membrane structure of benefit lithium electrolyte layer in skeleton layer one side to guarantee at electric core manufacture in-process, whole membrane can satisfy the intensity specification of equipment pulling, satisfy the test of security performance such as anti heavy object impact of follow-up electric core simultaneously.

The heat resistance of the electrolyte membrane is improved through the synergistic effect of the framework layer, the enhancement layer and the lithium-supplement electrolyte layer, the thermal shrinkage and the thermal puncture are reduced, and the safety problem caused by puncture or thermal runaway is prevented. And because the inorganic solid electrolyte has higher ionic conductivity, the rate capability of the battery can be greatly improved.

A preparation method of an electrolyte membrane with a lithium supplementing function for a solid lithium battery comprises the following specific steps:

s1, respectively weighing a lithium-containing compound, an inorganic solid electrolyte, a binder and a conductive agent, respectively dispersing the weighed lithium-containing compound and the weighed inorganic solid electrolyte in NMP, and respectively preparing a lithium-containing compound dispersion liquid and an inorganic solid electrolyte dispersion liquid by ball milling; simultaneously, stirring and dissolving the weighed adhesive in NMP to prepare an adhesive solution;

s2, mixing the lithium-containing compound dispersion liquid and the inorganic solid electrolyte dispersion liquid according to the mass ratio, adding a conductive agent into the mixture, and continuously performing ball milling dispersion and mixing to prepare a mixed dispersion liquid;

s3, adding the binder solution obtained in the step S1 into the mixed dispersion liquid obtained in the step S2, and performing ball milling and mixing to obtain uniform slurry;

and S4, simultaneously coating the uniform slurry obtained in the step S3 on the surface of one side of the reinforcing layer opposite to the framework layer through a double-unwinding mode, drying the uniform slurry in an oven of a coating machine, and further forming a lithium-supplement electrolyte layer between the reinforcing layer and the framework layer, so that the lithium-supplement functional electrolyte membrane for the solid lithium battery is obtained.

Specifically, in step S1, the binder was dissolved in NMP with stirring at a solid content of 10%, to prepare a binder solution. The particle size of the lithium-containing compound after ball milling in step S1 is 0.1 to 2 μm, and the particle size of the inorganic solid electrolyte particles after ball milling in step S1 is 0.1 to 2 μm.

The temperature of the oven in the step S4 is 60 to 80 ℃, the content of the lithium-containing compound in the lithium-supplement electrolyte layer obtained in the step S4 is 10 to 45%, the content of the inorganic solid electrolyte particles is 50 to 80%, the content of the binder is 3.5 to 10%, and the content of the conductive agent is 0.5 to 2%.

The dispersing and ball milling equipment in the steps S1, S2 and S3 comprises a double-planet dispersing machine, a planet ball mill and a horizontal ball mill.

Examples 1,

A preparation method of an electrolyte membrane with a lithium supplementing function for a solid lithium battery comprises the following specific steps:

s1, respectively weighing Li₂NiO₂LATP, PVP and Super-P, weighing Li₂NiO₂And LATP is respectively dispersed in NMP according to the solid content of 45 percent and is respectively ball-milled to prepare a lithium-containing compound dispersion liquid and an inorganic solid electrolyte dispersion liquid, the ball-milling rotating speed is 300rpm, so that Li in the lithium-containing compound dispersion liquid₂NiO₂Particle size in the range of 0.8 μm to obtain an inorganic solid electrolyte dispersionThe particle size of the LATP is 0.3 μm; simultaneously stirring and dissolving the weighed binder in NMP to prepare a binder solution;

s2, mixing the lithium-containing compound dispersion liquid and the inorganic solid electrolyte dispersion liquid according to the mass ratio, adding a conductive agent, continuing ball milling dispersion, and mixing to prepare a mixed dispersion liquid, wherein the ball milling rotation speed is 300rpm, and the ball milling time is 1 h;

s3, adding the binder solution obtained in the step S1 into the mixed dispersion liquid obtained in the step S2, and performing ball milling and mixing to obtain uniform slurry, wherein the ball milling speed is 300 rpm;

and S4, simultaneously coating the uniform slurry obtained in the step S3 on the surface of one side of the reinforcing layer opposite to the framework layer through a double-unwinding mode, drying the uniform slurry in an oven of a coating machine at the temperature of 60-80 ℃, and further forming a lithium-supplement electrolyte layer between the reinforcing layer and the framework layer, so that the lithium-supplement functional electrolyte membrane for the solid lithium battery is obtained. Wherein the first polymer base material of the framework layer is PET, the second polymer base material of the enhancement layer is PE, and Li in the prepared lithium-supplement electrolyte layer₂NiO₂The contents of LATP, PVP and Super-P were 30%, 64.5%, 4% and 1.5%, respectively.

Examples 2,

A preparation method of an electrolyte membrane with a lithium supplementing function for a solid lithium battery comprises the following specific steps:

s1, respectively weighing Li₅FeO₄LLZTO, PVDF and Super-P/CNTs, weighing Li₅FeO₄And respectively dispersing LLZTO in NMP according to 45% of solid content, and respectively preparing lithium-containing compound dispersion liquid and inorganic solid electrolyte dispersion liquid by ball milling, wherein the ball milling rotating speed is 300rpm, so that Li in the lithium-containing compound dispersion liquid₅FeO₄The particle size range was 0.1 μm, and the particle size of LLZTO in the inorganic solid electrolyte dispersion was 0.3 μm; simultaneously stirring and dissolving the weighed binder in NMP to prepare a binder solution;

s2, mixing the lithium-containing compound dispersion liquid and the inorganic solid electrolyte dispersion liquid according to the mass ratio, adding a conductive agent, continuing ball milling dispersion, and mixing to prepare a mixed dispersion liquid, wherein the ball milling rotation speed is 300rpm, and the ball milling time is 1 h;

s3, adding the binder solution obtained in the step S1 into the mixed dispersion liquid obtained in the step S2, and performing ball milling and mixing to obtain uniform slurry, wherein the ball milling speed is 300 rpm;

and S4, simultaneously coating the uniform slurry obtained in the step S3 on the surface of one side of the reinforcing layer opposite to the framework layer through a double-unwinding mode, drying the uniform slurry in an oven of a coating machine at the temperature of 60-80 ℃, and further forming a lithium-supplement electrolyte layer between the reinforcing layer and the framework layer, so that the lithium-supplement functional electrolyte membrane for the solid lithium battery is obtained. Wherein the first polymer base material of the framework layer is PI, the second polymer base material of the enhancement layer is PE, and Li in the prepared lithium-supplement electrolyte layer₅FeO₄The contents of LLZTO, PVDF and Super-P/CNTs were 20%, 73.5%, 5% and 1.5%, respectively.

Examples 3,

A preparation method of an electrolyte membrane with a lithium supplementing function for a solid lithium battery comprises the following specific steps:

s1, respectively weighing Li₂DHBN, LLZNO, PVDF-HFP and graphene/CNTs, namely the weighed Li₂Respectively dispersing DHBN and LLZNO in NMP according to the solid content of 45 percent, respectively preparing a lithium-containing compound dispersion liquid and an inorganic solid electrolyte dispersion liquid by ball milling, wherein the ball milling rotating speed is 300rpm, so that Li in the lithium-containing compound dispersion liquid₂The particle size range of DHBN is 0.3 mu m, so that the particle size of LLZNO in the inorganic solid electrolyte dispersion liquid is 0.8 mu m; simultaneously stirring and dissolving the weighed binder in NMP to prepare a binder solution;

s2, mixing the lithium-containing compound dispersion liquid and the inorganic solid electrolyte dispersion liquid according to the mass ratio, adding a conductive agent, continuing ball milling dispersion, and mixing to prepare a mixed dispersion liquid, wherein the ball milling rotation speed is 300rpm, and the ball milling time is 1 h;

s3, adding the binder solution obtained in the step S1 into the mixed dispersion liquid obtained in the step S2, and performing ball milling and mixing to obtain uniform slurry, wherein the ball milling speed is 300 rpm;

s4, passing the uniform slurry obtained in the step S3 through a double-layerAnd (3) simultaneously coating the surface of one side of the reinforcing layer, which is opposite to the framework layer, in an unreeling mode, drying in a drying oven of a coating machine at the temperature of 60-80 ℃, and further forming a lithium supplement electrolyte layer between the reinforcing layer and the framework layer, so as to obtain the lithium supplement functional electrolyte membrane for the solid lithium battery. Wherein the first polymer base material of the framework layer is cellulose, the second polymer base material of the enhancement layer is PE, and Li in the prepared lithium-supplement electrolyte layer₂The contents of DHBN, LLZNO, PVDF-HFP and graphene/CNTs are 40%, 52.2%, 7% and 0.8% respectively.

Examples 4,

A preparation method of an electrolyte membrane with a lithium supplementing function for a solid lithium battery comprises the following specific steps:

s1, respectively weighing Li₆CoO₄LAGP, EAV and CNTs, weighing Li₆CoO₄And respectively dispersing LAGP in NMP according to the solid content of 45 percent, and respectively preparing a lithium-containing compound dispersion liquid and an inorganic solid electrolyte dispersion liquid by ball milling, wherein the ball milling rotating speed is 300rpm, so that Li in the lithium-containing compound dispersion liquid₆CoO₄The particle size range was 1.5 μm, and the particle size of LAGP in the inorganic solid electrolyte dispersion was 0.6 μm; simultaneously stirring and dissolving the weighed binder in NMP to prepare a binder solution;

s2, mixing the lithium-containing compound dispersion liquid and the inorganic solid electrolyte dispersion liquid according to the mass ratio, adding a conductive agent, continuing ball milling dispersion, and mixing to prepare a mixed dispersion liquid, wherein the ball milling rotation speed is 300rpm, and the ball milling time is 1 h;

s3, adding the binder solution obtained in the step S1 into the mixed dispersion liquid obtained in the step S2, and performing ball milling and mixing to obtain uniform slurry, wherein the ball milling speed is 300 rpm;

and S4, simultaneously coating the uniform slurry obtained in the step S3 on the surface of one side of the reinforcing layer opposite to the framework layer through a double-unwinding mode, drying the uniform slurry in an oven of a coating machine at the temperature of 60-80 ℃, and further forming a lithium-supplement electrolyte layer between the reinforcing layer and the framework layer, so that the lithium-supplement functional electrolyte membrane for the solid lithium battery is obtained. Wherein the first polymer substrate of the framework layer isPA, the second polymer substrate of the enhancement layer is PP, and Li in the prepared lithium-supplement electrolyte layer₆CoO₄LAGP, EAV and CNTs were 15%, 78%, 6% and 1%, respectively.

Examples 5,

A preparation method of an electrolyte membrane with a lithium supplementing function for a solid lithium battery comprises the following specific steps:

s1, respectively weighing Li₂C₂O₄LLTO, PAN and graphene/CNTs, weighing Li₂C₂O₄And respectively dispersing LLTO in NMP according to the solid content of 45 percent, and respectively preparing a lithium-containing compound dispersion liquid and an inorganic solid electrolyte dispersion liquid by ball milling, wherein the ball milling rotating speed is 300rpm, so that Li in the lithium-containing compound dispersion liquid₂C₂O₄Particle size range of 1.5 μm, particle size of LLTO in inorganic solid electrolyte dispersion is 0.6 μm; simultaneously stirring and dissolving the weighed binder in NMP to prepare a binder solution;

s2, mixing the lithium-containing compound dispersion liquid and the inorganic solid electrolyte dispersion liquid according to the mass ratio, adding a conductive agent, continuing ball milling dispersion, and mixing to prepare a mixed dispersion liquid, wherein the ball milling rotation speed is 300rpm, and the ball milling time is 1 h;

s3, adding the binder solution obtained in the step S1 into the mixed dispersion liquid obtained in the step S2, and performing ball milling and mixing to obtain uniform slurry, wherein the ball milling speed is 300 rpm;

and S4, simultaneously coating the uniform slurry obtained in the step S3 on the surface of one side of the reinforcing layer opposite to the framework layer through a double-unwinding mode, drying the uniform slurry in an oven of a coating machine at the temperature of 60-80 ℃, and further forming a lithium-supplement electrolyte layer between the reinforcing layer and the framework layer, so that the lithium-supplement functional electrolyte membrane for the solid lithium battery is obtained. Wherein the first polymer base material of the framework layer is PET, the second polymer base material of the enhancement layer is PP, and Li in the prepared lithium-supplement electrolyte layer₂C₂O₄LLTO, PAN and graphene/CNTs contents were 40%, 54.2%, 5% and 0.8%, respectively.

Lithium batteries were prepared by using the lithium-supplement functional electrolyte membranes and ceramic coating membranes for solid-state lithium batteries obtained in examples 1 to 5, respectively, and the specific steps were as follows:

step 1, preparing a positive plate, namely mixing nickel cobalt lithium manganate, carbon black and a binder (PVDF) according to a mass ratio of 95:2:3 to prepare slurry, uniformly coating the slurry on a carbon-coated aluminum foil current collector, drying the carbon-coated aluminum foil current collector in an air-blowing oven at 80 ℃, and then drying the carbon-coated aluminum foil current collector in vacuum at 80 ℃ for 8 hours to prepare the positive plate;

step 2, preparing a negative plate, namely mixing SiOx/graphite (SiOx: graphite is 3:7, x is more than 0 and less than or equal to 2), carbon black and a butylbenzene emulsion binder in a mass ratio of 94:1.8:4.2, taking water as a solvent, pulping, uniformly coating the slurry on a copper foil current collector, drying the copper foil current collector in a blast oven at the temperature of 55 ℃, and then performing vacuum drying at the temperature of 60 ℃ for 12 hours to prepare the negative plate;

step 3, respectively adopting the lithium-supplement functional electrolyte membrane and the proportional ceramic coating membrane for the solid-state lithium battery prepared in the embodiments 1-5 to laminate the positive electrode and the negative electrode according to the condition that n/p is 1.05, preparing a 5Ah soft package battery cell, welding a tab, performing side sealing and performing top sealing on one side of a framework layer, wherein the tab is opposite to the positive electrode;

step 4, in a glove box under the protection of argon, an interfacial wetting agent (1M LiPF6 dissolved in an organic solvent with a volume ratio of EC: DEC: DMC ═ 1:1: 1) is added, and the mixture is sealed.

And 5, forming, secondary sealing and capacity grading to prepare the lithium battery.

The lithium-supplement functional electrolyte membrane for a solid lithium battery and the common ceramic coating membrane prepared in the above manner were subjected to heat shrinkage and hot puncture tests.

Heat shrinkage Performance test with reference to ISO 14616-1997 test for film shrinkage stress in heat-shrinkable of polyethylene, ethylene copolymers and mixtures thereof, cutting the test specimens into 120mm x 120mm square test specimens using an image measuring apparatus, drawing 10cm lines in the MD and TD directions on the test specimens, and testing the heat shrinkage of the films in the MD and TD directions after heat treatment at 180 ℃ for 60 min.

The hot puncture performance test is that a steel needle heated to 300 ℃ penetrates through the membrane surface on a tensile machine at a speed of 100mm/min, and the aperture of the membrane surface is measured by an image measuring instrument.

TABLE 1,

	300 ℃ hot puncture test, pore size of membrane surface (mm)
		Example 1	2.69
Comparative example 1(PE ceramic coating film)	4.99
		Comparative example 2(PP ceramic coating film)	5.284

As can be seen from fig. 3 and 4, the comparison between the electrolyte membrane of example 1 and the electrolyte membrane before and after heat treatment at 180 ℃ for 1 hour shows that the electrolyte membrane of example 1 has a temperature resistance significantly superior to that of the conventional ceramic coating membrane, particularly, the PE ceramic coating membrane, and the membrane is completely broken and not formed after baking at 180 ℃.

According to the hot puncture performance test, the pore size of the membrane surface of the lithium-supplement functional electrolyte membrane is obviously smaller than that of a comparative example after the lithium-supplement functional electrolyte membrane is subjected to hot puncture at 300 ℃, and the puncture performance of the battery can be further improved.

In a cycle stability test, a cycle life curve in a 1C (1C ═ 5A) charge-discharge mode is shown in fig. 2, and it can be seen from the cycle performance of the example 1 and the comparative example battery that, by supplementing redundant lithium ions provided by the first circle of the lithium compound in the lithium-supplementing electrolyte membrane, the lithium ion battery can realize more stable cycle, and the example 1 can still have 100% capacity retention rate after 360 circles of 1C cycle; in contrast, in the comparative example, since the utilization efficiency of lithium ions was low, the cycle performance was poor, and the retention rate was only 77.41% after 243 cycles.

Compared with the prior art, the lithium supplement function electrolyte membrane for the solid lithium battery replaces the traditional lithium ion battery diaphragm, the first circle of lithium ion supplement can be realized after the battery is assembled, the cycle performance of the battery is improved, and the performance of the battery cannot be damaged after the first circle of charging. The lithium supplement electrolyte layer is filled in the framework layer and between the enhancement layers, so that good lithium supplement can be realized, and the lithium supplement agent can be prevented from falling into the electrolyte, so that the lithium supplement efficiency is reduced. Meanwhile, the lithium supplement electrolyte layer has controllable thickness, and the lithium supplement amount can be easily adjusted according to a positive and negative electrode system. The inorganic solid electrolyte particles in the lithium-supplementing electrolyte layer can not only increase lithium ion conduction, but also enhance the heat resistance of the diaphragm and reduce the thermal shrinkage and thermal puncture of the diaphragm.

Although preferred embodiments of the present invention have been described in detail hereinabove, it should be clearly understood that modifications and variations of the present invention are possible to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.