CN113764667B - Lithium supplementing functional electrolyte membrane for solid lithium battery - Google Patents

Lithium supplementing functional electrolyte membrane for solid lithium battery Download PDF

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CN113764667B
CN113764667B CN202110922764.6A CN202110922764A CN113764667B CN 113764667 B CN113764667 B CN 113764667B CN 202110922764 A CN202110922764 A CN 202110922764A CN 113764667 B CN113764667 B CN 113764667B
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lithium
supplementing
layer
inorganic solid
solid electrolyte
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CN113764667A (en
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杨杰
林久
许晓雄
崔言明
张永龙
楼凯
戈志敏
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Zhejiang Funlithium New Energy Tech Co Ltd
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Zhejiang Funlithium New Energy Tech Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/70—Carriers or collectors characterised by shape or form
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The invention discloses a lithium supplementing functional electrolyte membrane for a solid-state lithium battery, which consists of a framework layer, a reinforcing layer and a lithium supplementing electrolyte layer, wherein the framework layer is provided with a three-dimensional porous structure, and part of the lithium supplementing electrolyte layer is filled in the porous structure of the framework layer. The lithium-supplementing functional electrolyte membrane for the solid-state lithium battery replaces the traditional lithium ion battery diaphragm, can realize first-circle charging to supplement lithium ions after the battery is assembled, improves the cycle performance of the battery, and does not damage the performance of the battery after the first-circle charging. The lithium supplementing electrolyte layer is filled in the framework layer and between the enhancement layers, so that good lithium supplementing can be realized, and lithium supplementing efficiency reduction caused by falling of a lithium supplementing agent into the electrolyte can be avoided. Meanwhile, the lithium supplementing electrolyte layer has controllable thickness, and the lithium supplementing amount is adjusted according to the 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.

Description

Lithium supplementing functional electrolyte membrane for solid lithium battery
Technical Field
The invention belongs to the technical field of lithium batteries, and particularly relates to a lithium supplementing functional electrolyte membrane for a solid-state lithium battery.
Background
The lithium ion battery has the advantages of higher 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 a lithium ion battery, an SEI film is formed on the surface of the negative electrode, which consumes active lithium in the positive electrode, resulting in irreversible capacity loss, the irreversible capacity loss of the graphite negative electrode which is most widely used at present can reach 10%, and for silicon-based and tin-based negative electrodes with high specific capacities, the irreversible capacity loss is even more than 30%, which greatly reduces the energy density of the lithium ion battery. For the problem, it is widely accepted 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 supplementing schemes can be divided into three main categories: 1) Lithium is supplemented to the cathode, mainly inert metal lithium powder, metal lithium foil and vacuum winding evaporation plating lithium supplementing; 2) Positive electrode lithium-supplementing, mainly of oxides containing lithium, e.g. Li 5 FeO 4 Etc.; 3) The third electrode supplements lithium by charging and discharging between the negative electrode and the third electrode (for example, a metal lithium electrode and a high-capacity lithium-containing oxide electrode).
The negative electrode adopts the metal lithium to supplement lithium, has the advantages of high lithium supplementing efficiency, no residue after reaction, high activity of the metal lithium, high requirement on environmental control, large equipment, large cost investment and large influence on the existing production process. Meanwhile, the adoption of the metal lithium also has a large safety risk, and particularly, the metal lithium powder can cause risks such as dust explosion and the like when suspended in the air. Meanwhile, if the lithium supplement is insufficient, the energy density is not obviously improved; excessive lithium supplementation can form a metal lithium coating on the surface of the negative electrode, and the battery performance is damaged.
The positive electrode lithium supplement has the advantages of simple process, low cost, high safety and the like, and has received a great deal of attention in recent years. Patent CN110120493a provides a positive electrode lithium supplementing method for pulping and smearing a lithium supplementing material, a positive electrode material, a conductive agent and a binder together, but in the method, the lithium supplementing sacrificial agent has a certain influence on mass transfer inside the whole pole piece after delithiation of the positive electrode side. Patent CN109755448A will contain Li 5 FeO 4 The lithium-supplementing coating containing lithium compound, nano inert inorganic filler and binder is coated on the diaphragm substrate to prepare the lithium battery diaphragm with the lithium-supplementing coating, and the heat shrinkage of the diaphragm is reduced while lithium is supplemented, but the lithium-supplementing agent can influence the adhesion between the lithium-supplementing layer and the diaphragm substrate after lithium removal, and the lithium-supplementing agent falls into electrolyte, so that the lithium-supplementing efficiency is reduced.
Therefore, the electrolyte membrane with the lithium supplementing function for the solid-state lithium battery, which has the high-efficiency controllable lithium supplementing effect, can prolong the cycle life of the battery and has better temperature resistance, is particularly important for the development of the lithium battery.
Disclosure of Invention
The invention aims to solve the technical problem of providing a lithium supplementing functional electrolyte membrane for a solid-state lithium battery, which solves the problems that a lithium supplementing diaphragm in the prior art is poor in temperature resistance and a lithium supplementing layer can fall into electrolyte.
The technical scheme adopted for solving the technical problems is as follows:
the electrolyte membrane is composed 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 is provided with a three-dimensional porous structure, and part of the lithium supplementing electrolyte layer is filled in the porous structure of the framework layer.
Preferably, the lithium-compensating electrolyte layer includes a lithium-containing compound, inorganic solid electrolyte particles, a binder, and a conductive agent.
Preferably, 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%.
Preferably, the lithium-containing compound 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 is Li 5 FeO 4 、Li 5 Fe 5 O 8 、Li 6 CoO 4 、Li 2 NiO 2 、Li 2 O、Li 2 S、Li 3 P、Li 3 N、Li 2 O 2 、Li 2 C 2 O 4 、Li 2 At least one of DHBN.
Preferably, the particle diameter of the lithium-containing compound is 0.1 μm to 2. Mu.m.
Preferably, the inorganic solid electrolyte particles are of a NASICON type structure, and the chemical formula of the inorganic solid electrolyte particles is LiM 2 (PO 4 ) 3 、Li 1+x Al x Ti 2-x (PO 4 ) 3 And Li (lithium) 1+x Al x Ge 2-x (PO 4 ) 3 Wherein M is one of Ti, ge and Hf, and x is more than 0 and less than 2;
or the inorganic solid electrolyte particles are of perovskite structure, and the chemical formula of the inorganic solid electrolyte particles is Li 0.34 La 0.56 TiO 3 And/or Li 0.5 La 0.5 TiO 3 ；
Or the inorganic solid electrolyte particles are LISICON structures, and the chemical formula of the inorganic solid electrolyte particles is Li 14 Zn(GeO 4 ) 4 ；
Or the inorganic solid electrolyte particles are garnet-type structures, and the chemical formula of the inorganic solid electrolyte particles is Li 5 La 3 R 2 O 12 、Li 6 ALa 2 R 2 O 12 、Li 5.5 La 3 R 1.75 D 0.25 O 12 、Li 7 La 3 Zr 2 O 12 And Li (lithium) 7.06 E 3 Y 0.06 Zr 1.94 O 12 Wherein 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 inverse perovskite structure, and the chemical formula of the inorganic solid electrolyte particles is Li 3 OX, wherein X is one of F, cl and 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 Li 10 GeP 2 S 12 、Li 2 S-SiS 2 、Li 2 S-P 2 S 5 、70Li 2 S-30P 2 S 5 One or more of the following.
Preferably, the particle diameter of the inorganic solid electrolyte particles is 0.1 μm to 2. Mu.m.
Preferably, the binder is at least one of PVDF and PVDF-HFP, PVP, PEO, PAN, EVA, PMMA;
the conductive agent is one or more of Super-P, ketjen black, CNTs and graphene;
the framework layer is a three-dimensional porous structure nonwoven film and comprises a first polymer base material, wherein the first polymer base material is one of cellulose and PET, PI, PVDF, PA, PVC.
Preferably, the reinforcing 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 electrolyte membrane with the lithium supplementing function for the solid-state lithium battery has the advantages that,
1) The lithium-containing compound in the lithium supplementing functional electrolyte membrane for the solid-state lithium battery can take off more lithium ions in the battery charging process to participate in forming an SEI layer, so that the loss of lithium ions in the positive electrode active material is reduced, more lithium ions can participate in the intercalation and the deintercalation, the discharge capacity of the lithium battery is improved, and the charge-discharge cycle life of the lithium battery is prolonged;
2) The inorganic solid electrolyte has higher ionic conductivity, so that the rate capability of the battery can be greatly improved;
3) The lithium supplementing electrolyte layer is filled in the framework layer and between the framework layer and the reinforcing layer, and the framework layer and the reinforcing layer are tightly adhered through the lithium supplementing electrolyte layer, so that good lithium supplementing can be realized, and the problem that the lithium supplementing effect is affected due to the fact that the electrolyte layer falls into the electrolyte due to the fact that the lithium supplementing agent is separated in the lithium supplementing process can be avoided;
4) The enhancement layer is arranged, so that the overall mechanical strength of the membrane is far greater than that of a membrane structure which is provided with a framework layer only and a lithium-supplementing electrolyte layer arranged on one side of the framework layer, and therefore, the whole membrane can meet the strength specification of equipment pulling in the process of manufacturing the battery cell, and simultaneously, the safety performance test such as heavy-load impact resistance of the subsequent battery cell is met;
5) The heat resistance of the electrolyte membrane is improved through the synergistic effect of the framework layer, the reinforcing layer and the lithium supplementing electrolyte layer, the thermal shrinkage and the thermal puncture are reduced, and the safety problem caused by puncture or thermal runaway is prevented.
Drawings
FIG. 1 is an electron micrograph of the surface of a lithium-compensating electrolyte layer in this example;
fig. 2 is a cycle life curve of the present embodiment in the 1C (1c=5a) charge/discharge mode;
FIG. 3 is a photograph before heat treatment at 180℃in this example (example 1, comparative example 1 and comparative example 2 from top to bottom, respectively);
FIG. 4 is a photograph (from top to bottom, example 1, comparative example 1 and comparative example 2, respectively) of the present example after heat treatment at 180℃for 1 hour.
Detailed Description
The invention is described in further detail below with reference to the embodiments of the drawings.
The electrolyte membrane is composed 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 is provided with 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 from the lithium supplementing electrolyte layer in the charging and discharging process of the battery, the lithium supplementing electrolyte layer participates in forming an SEI layer, the loss of lithium ions in an anode active substance is further reduced, and the lithium supplementing electrolyte layer is arranged between the framework layer and the reinforcing layer, so that the structure of the lithium supplementing electrolyte layer is changed even if the lithium supplementing electrolyte layer is subjected to lithium extraction in the lithium supplementing process, the lithium supplementing electrolyte layer cannot fall into electrolyte due to the falling of the lithium supplementing electrolyte layer, and the lithium supplementing effect is further guaranteed.
And the reinforcing layer is arranged, so that the overall mechanical strength of the film is higher. Experiments find that, an inorganic electrolyte layer is arranged on one side of a framework layer, a lithium supplementing electrolyte film obtained by arranging a composite electrolyte layer on the other side has the highest mechanical strength of only 50Mpa, and the lithium supplementing electrolyte layer of the lithium supplementing functional electrolyte film for the solid-state lithium battery in the embodiment is filled in the framework layer and between the framework layer and a reinforcing layer, and the framework layer and the reinforcing layer are tightly adhered through the lithium supplementing electrolyte layer, so that the integral mechanical strength of the film is more than 100Mpa, the integral film can meet the strength specification of equipment pulling in the manufacturing process of the battery core, and meanwhile, the test of the safety performance such as heavy-weight impact resistance of the subsequent battery core is met.
Specifically, the lithium-compensating electrolyte layer includes a lithium-containing compound, inorganic solid electrolyte particles, a binder, and a conductive agent.
The lithium-containing compound in the lithium supplementing functional electrolyte membrane for the solid-state lithium battery can take off more lithium ions in the battery charging process, participate in forming an SEI layer, further reduce the loss of lithium ions in the positive electrode active substance, further ensure that more lithium ions participate in the intercalation and the deintercalation, improve the discharge capacity of the lithium battery and prolong the charge-discharge cycle life of the lithium battery.
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 Li 5 FeO 4 、Li 5 Fe 5 O 8 、Li 6 CoO 4 、Li 2 NiO 2 、Li 2 O、Li 2 S、Li 3 P、Li 3 N、Li 2 O 2 、Li 2 C 2 O 4 、Li 2 At least one of DHBN.
The activity of the lithium-containing compound increases with decreasing particle size, and is more reactive with environmental moisture, binders and solutions, accelerating the slurry gel. The dynamics of the large-particle lithium-containing compound is poor, so that the lithium supplementing efficiency is reduced, the particle size of the lithium-containing compound is required to be 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 lithium supplementing efficiency can be improved, and the energy density and the electrochemical performance of the battery can be further improved.
The inorganic solid electrolyte particles are of a NASICON structure, and the chemical formula of the inorganic solid electrolyte particles is LiM 2 (PO 4 ) 3 、Li 1+x Al x Ti 2-x (PO 4 ) 3 (LATP) and Li 1+x Al x Ge 2-x (PO 4 ) 3 (LAGP) wherein M is one of Ti, ge and Hf, 0 < x < 2;
or the inorganic solid electrolyte particles are of perovskite structure, and the chemical formula of the inorganic solid electrolyte particles is Li 0.34 La 0.56 TiO 3 And/or Li 0.5 La 0.5 TiO 3 ；
Or the inorganic solid electrolyte particles are of LISICON structure, and the chemical formula of the inorganic solid electrolyte particles is Li 14 Zn(GeO 4 ) 4 ；
Or the inorganic solid electrolyte particles are of garnet structure, and the chemical formula of the inorganic solid electrolyte particles is Li 5 La 3 R 2 O 12 、Li 6 ALa 2 R 2 O 12 、Li 5.5 La 3 R 1.75 D 0.25 O 12 、Li 7 La 3 Zr 2 O 12 And Li (lithium) 7.06 E 3 Y 0.06 Zr 1.94 O 12 Wherein 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 inverse perovskite structure, and the chemical formula of the inorganic solid electrolyte particles is Li 3 OX, X is one of F, cl and 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 Li 10 GeP 2 S 12 、Li 2 S-SiS 2 、Li 2 S-P 2 S 5 、70Li 2 S-30P 2 S 5 One or more of the following.
The particle size of the inorganic solid electrolyte particles is preferably 0.1 μm 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 and PVDF-HFP, PVP, PEO, PAN, EVA, PMMA.
The conductive agent is one or more of Super-P, ketjen black, CNTs and graphene.
The skeleton layer is a three-dimensional porous structure nonwoven film, and comprises a first polymer base material, wherein the first polymer base material is one of cellulose and PET, PI, PVDF, PA, PVC.
The reinforcing layer comprises a second polymer substrate, and the second polymer substrate is one of PE, PP and PE/PP/PE.
A preparation method of a lithium supplementing functional electrolyte membrane 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 inorganic solid electrolyte in NMP, and respectively ball-milling to prepare a lithium-containing compound dispersion liquid and an inorganic solid electrolyte dispersion liquid; 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 continuing ball milling, dispersing 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, 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 unreeling mode, drying in an oven of a coating machine, and further forming a lithium supplementing electrolyte layer between the reinforcing layer and the framework layer, so that the lithium supplementing functional electrolyte membrane for the solid-state lithium battery is obtained.
Specifically, in step S1, a binder solution was prepared by dissolving a binder in NMP with stirring at a solid content of 10%. The particle size of the lithium-containing compound after ball milling in the step S1 is 0.1-2 mu m, and the particle size of the inorganic solid electrolyte particles after ball milling in the step S1 is 0.1-2 mu m.
The temperature of the oven in the step S4 is 60-80 ℃, the content of the lithium-containing compound in the lithium-supplementing electrolyte layer obtained in the step S4 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 dispersing and ball milling equipment in the steps S1, S2 and S3 comprises a double-planetary dispersing machine, a planetary ball mill and a horizontal ball mill.
Example 1,
A preparation method of a lithium supplementing functional electrolyte membrane for a solid lithium battery comprises the following specific steps:
s1, respectively weighing Li 2 NiO 2 LATP, PVP and Super-P, li to be weighed 2 NiO 2 And LATP are respectively dispersed in NMP according to the solid content of 45 percent, and are respectively ball-milled to prepare lithium-containing compound dispersion liquid and inorganic solid electrolyte dispersion liquid, wherein the ball-milling speed is 300rpm, so that Li in the lithium-containing compound dispersion liquid 2 NiO 2 Particle diameter range is 0.8 μm, so that the particle diameter of LATP in the inorganic solid electrolyte dispersion 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 into the mixture, and continuing ball milling and dispersing, mixing to prepare a mixed dispersion liquid, wherein the ball milling speed is 300rpm, and the ball milling time is 1h;
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 rotating speed is 300rpm;
and S4, 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 unreeling mode, drying in an oven of a coating machine at 60-80 ℃, and further forming a lithium supplementing electrolyte layer between the reinforcing layer and the framework layer, thereby obtaining the lithium supplementing functional electrolyte membrane for the solid-state lithium battery. Wherein the first polymer substrate of the framework layer is PET, the second polymer base material of the enhancement layer is PE, and Li in the prepared lithium supplementing electrolyte layer 2 NiO 2 The LATP, PVP and Super-P contents were 30%, 64.5%, 4% and 1.5%, respectively.
EXAMPLE 2,
A preparation method of a lithium supplementing functional electrolyte membrane for a solid lithium battery comprises the following specific steps:
s1, respectively weighing Li 5 FeO 4 LLZTO, PVDF and Super-P/CNTs, li to be weighed 5 FeO 4 And LLZTO are respectively dispersed in NMP according to the solid content of 45 percent, and are respectively ball-milled to prepare lithium-containing compound dispersion liquid and inorganic solid electrolyte dispersion liquid, wherein the ball-milling speed is 300rpm, so that Li in the lithium-containing compound dispersion liquid 5 FeO 4 The particle size range is 0.1 μm, so that the particle size of LLZTO in the inorganic solid electrolyte dispersion 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 into the mixture, and continuing ball milling and dispersing, mixing to prepare a mixed dispersion liquid, wherein the ball milling speed is 300rpm, and the ball milling time is 1h;
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 rotating speed is 300rpm;
and S4, 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 unreeling mode, drying in an oven of a coating machine at 60-80 ℃, and further forming a lithium supplementing electrolyte layer between the reinforcing layer and the framework layer, thereby obtaining the lithium supplementing functional electrolyte membrane for the solid-state lithium battery. Wherein the first polymer base material of the framework layer is PI, the second polymer base material of the reinforcing layer is PE, and Li in the prepared lithium supplementing electrolyte layer 5 FeO 4 The LLZTO, PVDF and Super-P/CNTs contents were 20%, 73.5%, 5% and 1.5%, respectively.
EXAMPLE 3,
A preparation method of a lithium supplementing functional electrolyte membrane for a solid lithium battery comprises the following specific steps:
s1, respectively weighing Li 2 DHBN, LLZNO, PVDF-HFP and graphene/CNTs, li to be weighed 2 Respectively dispersing DHBN and LLZNO in NMP according to solid content of 45%, respectively ball-milling to obtain lithium-containing compound dispersion liquid and inorganic solid electrolyte dispersion liquid, and ball-milling at 300rpm to obtain Li in the lithium-containing compound dispersion liquid 2 The DHBN particle size range is 0.3 μm, so that the particle size of LLZNO in the inorganic solid electrolyte dispersion is 0.8 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 into the mixture, and continuing ball milling and dispersing, mixing to prepare a mixed dispersion liquid, wherein the ball milling speed is 300rpm, and the ball milling time is 1h;
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 rotating speed is 300rpm;
and S4, 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 unreeling mode, drying in an oven of a coating machine at 60-80 ℃, and further forming a lithium supplementing electrolyte layer between the reinforcing layer and the framework layer, thereby obtaining the lithium supplementing functional electrolyte membrane for the solid-state lithium battery. Wherein the first polymer base material of the framework layer is cellulose, the second polymer base material of the reinforcing layer is PE, and Li in the prepared lithium supplementing electrolyte layer 2 The contents of DHBN, LLZNO, PVDF-HFP and graphene/CNTs were 40%, 52.2%, 7% and 0.8%, respectively.
EXAMPLE 4,
A preparation method of a lithium supplementing functional electrolyte membrane for a solid lithium battery comprises the following specific steps:
s1, respectively weighing Li 6 CoO 4 LAGP, EAV and CNTs, li to be weighed 6 CoO 4 Respectively dispersing LAGP in NMP according to solid content of 45%, respectively ball-milling to obtain lithium compound dispersion liquid and inorganic solid electrolyte dispersion liquid, ball-milling to obtain the final productAt a speed of 300rpm to allow Li in the lithium-containing compound dispersion 6 CoO 4 The particle size range is 1.5 mu m, so that the particle size of LAGP in the inorganic solid electrolyte dispersion liquid is 0.6 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 into the mixture, and continuing ball milling and dispersing, mixing to prepare a mixed dispersion liquid, wherein the ball milling speed is 300rpm, and the ball milling time is 1h;
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 rotating speed is 300rpm;
and S4, 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 unreeling mode, drying in an oven of a coating machine at 60-80 ℃, and further forming a lithium supplementing electrolyte layer between the reinforcing layer and the framework layer, thereby obtaining the lithium supplementing functional electrolyte membrane for the solid-state lithium battery. Wherein the first polymer base material of the framework layer is PA, the second polymer base material of the reinforcing layer is PP, and Li in the prepared lithium supplementing electrolyte layer 6 CoO 4 The LAGP, EAV and CNTs content was 15%, 78%, 6% and 1%, respectively.
EXAMPLE 5,
A preparation method of a lithium supplementing functional electrolyte membrane for a solid lithium battery comprises the following specific steps:
s1, respectively weighing Li 2 C 2 O 4 LLTO, PAN and graphene/CNTs, li to be weighed 2 C 2 O 4 And LLTO are respectively dispersed in NMP according to the solid content of 45 percent, and are respectively ball-milled to prepare a lithium-containing compound dispersion liquid and an inorganic solid electrolyte dispersion liquid, wherein the ball-milling speed is 300rpm, so that Li in the lithium-containing compound dispersion liquid 2 C 2 O 4 The particle size range was 1.5. Mu.m, so that the particle size of LLTO in the inorganic solid electrolyte dispersion was 0.6. 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 into the mixture, and continuing ball milling and dispersing, mixing to prepare a mixed dispersion liquid, wherein the ball milling speed is 300rpm, and the ball milling time is 1h;
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 rotating speed is 300rpm;
and S4, 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 unreeling mode, drying in an oven of a coating machine at 60-80 ℃, and further forming a lithium supplementing electrolyte layer between the reinforcing layer and the framework layer, thereby obtaining the lithium supplementing functional electrolyte membrane for the solid-state lithium battery. Wherein the first polymer base material of the framework layer is PET, the second polymer base material of the reinforcing layer is PP, and Li in the prepared lithium supplementing electrolyte layer 2 C 2 O 4 The contents of LLTO, PAN and graphene/CNTs were 40%, 54.2%, 5% and 0.8%, respectively.
The lithium battery is prepared by respectively adopting the lithium supplementing functional electrolyte membrane and the ceramic coating membrane for the solid lithium battery, which are obtained in the examples 1-5, and the specific steps are as follows:
step 1, preparing a positive plate, namely mixing nickel cobalt lithium manganate, carbon black and a binder (PVDF) in a mass ratio of 95:2:3 for pulping, uniformly coating the slurry on a carbon-coated aluminum foil current collector, drying in a blowing oven at 80 ℃, and then drying in vacuum at 80 ℃ for 8 hours to prepare the positive plate;
step 2, preparing a negative plate, namely uniformly coating slurry on a copper foil current collector by mixing SiOx/graphite (SiOx: graphite=3:7, x is more than 0 and less than or equal to 2), carbon black and a styrene-butadiene emulsion binder according to the mass ratio of 94:1.8:4.2 and water as a solvent, drying in a blast oven at 55 ℃, and then vacuum drying at 60 ℃ for 12 hours to prepare the negative plate;
step 3, respectively adopting the lithium supplementing electrolyte membrane for the solid-state lithium battery and the comparative ceramic coating film prepared in the embodiments 1-5 to prepare a 5Ah soft-package battery core by lamination, and welding, side sealing and top sealing the tab of the positive electrode and the negative electrode according to n/p=1.05;
step 4, adding an interface wetting agent (1M LiPF6 is dissolved in an organic solvent with the volume ratio of EC: DEC: DMC=1:1:1) into a glove box under the protection of argon, and sealing.
And 5, forming, sealing for two times and separating the volume to prepare the lithium battery.
And carrying out thermal shrinkage and thermal puncture tests on the prepared electrolyte membrane with the lithium supplementing function for the solid-state lithium battery and the common ceramic coating membrane.
Thermal shrinkage Property test referring to Standard ISO 14616-1997 test for Heat shrink films of polyethylene, ethylene copolymer and mixtures thereof-test for shrinkage stress, the samples were cut into square samples of 120mm by 120mm using an image measuring apparatus, 10cm lines were drawn on the samples in MD and TD directions, and heat shrinkage rates in MD and TD directions of films heat-treated at 180℃for 60 minutes were measured.
And (3) testing the thermal puncture performance, wherein a steel needle heated to 300 ℃ passes through the membrane surface at a speed of 100mm/min on a tensile machine, and measuring the pore diameter of the membrane surface by using an image measuring instrument.
TABLE 1,
300 ℃ thermal puncture test, membrane surface pore diameter (mm)
Example 1 2.69
Comparative example 1 (PE ceramic coating film) 4.99
Comparative example 2 (PP ceramic coating film) 5.284
As is clear from the comparison of fig. 3 and 4, which show that the electrolyte membrane in example 1 has significantly better temperature resistance than the conventional ceramic coating film, particularly PE ceramic coating film, after baking at 180 c, the film is completely broken and not formed.
According to the thermal puncture performance test, after the lithium-supplementing functional electrolyte membrane is subjected to thermal puncture at 300 ℃, the pore diameter of the membrane surface is obviously smaller than that of a comparative example, and the needling performance of the battery can be further improved.
Cycle stability test, cycle life curves in 1C (1c=5a) charge and discharge modes are shown in fig. 2, and it can be seen from the cycle performance of example 1 and comparative example batteries that the lithium ion battery can realize more stable cycle through the surplus lithium ions provided by the first cycle of the lithium supplementing compound in the lithium supplementing electrolyte membrane, and the example 1 can still have 100% capacity retention rate after 360 cycles of 1C cycle; in the comparative example, the cycle performance was deteriorated due to the low utilization efficiency of lithium ions, and the retention rate was 77.41% after 243 cycles.
Compared with the prior art, the lithium-supplementing functional electrolyte membrane for the solid-state lithium battery replaces the traditional lithium ion battery diaphragm, can supplement lithium ions for the first circle after the battery is assembled, improves the cycle performance of the battery, and does not damage the performance of the battery after the first circle is charged. The lithium supplementing electrolyte layer is filled in the framework layer and between the enhancement layers, so that good lithium supplementing can be realized, and the lithium supplementing agent can be prevented from falling into the electrolyte, so that the lithium supplementing efficiency is reduced. Meanwhile, the lithium supplementing electrolyte layer has controllable thickness, and the lithium supplementing 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.
While the preferred embodiments of the present invention have been described in detail, it is to be clearly understood that the same may be varied in many ways by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (7)

1. A lithium supplementing functional electrolyte membrane for a solid lithium battery, characterized in that: 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 is provided with a three-dimensional porous structure, and part of the lithium supplementing electrolyte layer is filled in the porous structure of the framework layer;
the lithium supplementing electrolyte layer comprises a lithium-containing compound, inorganic solid electrolyte particles, a binder and a conductive agent;
the particle size of the inorganic solid electrolyte particles is 0.1-2 mu m;
the binder is at least one of PVDF, PVDF-HFP, PVP, PEO, PAN, EVA and PMMA;
the skeleton layer is a three-dimensional porous structure nonwoven film, and comprises a first polymer base material, wherein the first polymer base material is one of cellulose, PET, PI, PVDF, PA and PVC;
the reinforcing layer comprises a second polymer base material, wherein the second polymer base material is one of PE, PP and PE/PP/PE.
2. The lithium-compensating functional electrolyte membrane for a solid state lithium battery according to claim 1, wherein: 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%.
3. The lithium-compensating functional electrolyte membrane for a solid state lithium battery according to claim 2, wherein: the lithium-containing compound comprises lithium iron oxide, lithium nickel oxide, lithium cobalt oxide, organic lithium salt, li 2 O、Li 2 O 2 At least one of lithium sulfide, lithium phosphide, and lithium nitride.
4. A lithium-supplementing functional electrolysis for a solid state lithium battery as claimed in claim 3Plasma membrane, its characterized in that: the lithium-containing compound is Li 5 FeO 4 、Li 5 Fe 5 O 8 、Li 6 CoO 4 、Li 2 NiO 2 、Li 2 S、Li 3 P、Li 3 N、Li 2 C 2 O 4 And Li (lithium) 2 At least one of DHBN.
5. The lithium-compensating functional electrolyte membrane for a solid state lithium battery according to claim 3, wherein: the particle diameter of the lithium-containing compound is 0.1-2 mu m.
6. The lithium-compensating functional electrolyte membrane for a solid state lithium battery according to claim 1, wherein: the inorganic solid electrolyte particles are of a NASICON structure, and the chemical formula of the inorganic solid electrolyte particles is LiM 2 (PO 4 ) 3 、Li 1+ x Al x Ti 2-x (PO 4 ) 3 And Li (lithium) 1+x Al x Ge 2-x (PO 4 ) 3 Wherein M is one of Ti, ge and Hf, and x is more than 0 and less than 2;
or the inorganic solid electrolyte particles are of perovskite structure, and the chemical formula of the inorganic solid electrolyte particles is Li 0.34 La 0.56 TiO 3 And/or Li 0.5 La 0.5 TiO 3 ；
Or the inorganic solid electrolyte particles are LISICON structures, and the chemical formula of the inorganic solid electrolyte particles is Li 14 Zn(GeO 4 ) 4 ；
Or the inorganic solid electrolyte particles are garnet-type structures, and the chemical formula of the inorganic solid electrolyte particles is Li 5 La 3 R 2 O 12 、Li 6 ALa 2 R 2 O 12 、Li 5.5 La 3 R 1.75 D 0.25 O 12 、Li 7 La 3 Zr 2 O 12 And Li (lithium) 7.06 E 3 Y 0.06 Zr 1.94 O 12 Wherein 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 inverse perovskite structure, and the chemical formula of the inorganic solid electrolyte particles is Li 3 OX, wherein X is one of F, cl and 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 Li 10 GeP 2 S 12 、Li 2 S-SiS 2 、Li 2 S-P 2 S 5 、70Li 2 S-30P 2 S 5 One or more of the following.
7. The lithium-compensating functional electrolyte membrane for a solid state lithium battery according to claim 1, wherein: the conductive agent is at least one of Super-P, ketjen black, CNTs and graphene.
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