阅读说明：本技术 一种具有高强度、高离子电导率的环氧基固态电解质 (Epoxy solid electrolyte with high strength and high ionic conductivity ) 是由 李元庆 董光河 王向前 黄培 付绍云 于 2020-06-03 设计创作，主要内容包括：本发明公开了一种具有高强度、高离子电导率的环氧基固态电解质及其制备方法和应用,属于功能复合材料领域。所述环氧基固态电解质按重量份由下述组分构成：100份环氧树脂、35～45份固化剂、120～160份离子液体、50～70份锂盐、1～6份表面预处理短切碳纤维,其制备方法包括混合和固化两个步骤；所述表面预处理短切碳纤维的制备步骤包括：短切、去上浆剂和引入表面官能基团三个步骤。通过在环氧基固态电解质中引入表面预处理短切碳纤维,不但提高了电解质体系的自由锂离子浓度,而且将相互孤立的离子液体相串联成三维离子导电网络,大大提高了电解质的离子导电性；与此同时,显著改善了环氧基固态电解质的力学性能,适用于结构型电化学储能装置。(The invention discloses an epoxy solid electrolyte with high strength and high ionic conductivity, and a preparation method and application thereof, and belongs to the field of functional composite materials. The epoxy solid electrolyte comprises the following components in parts by weight: 100 parts of epoxy resin, 35-45 parts of curing agent, 120-160 parts of ionic liquid, 50-70 parts of lithium salt and 1-6 parts of surface pretreatment short-cut carbon fiber, wherein the preparation method comprises two steps of mixing and curing; the preparation method of the surface-pretreated chopped carbon fiber comprises the following steps: chopping, removing sizing agent and introducing surface functional group. By introducing the surface-pretreated chopped carbon fibers into the epoxy solid electrolyte, the free lithium ion concentration of an electrolyte system is improved, and the ionic liquids which are mutually isolated are connected in series to form a three-dimensional ionic conductive network, so that the ionic conductivity of the electrolyte is greatly improved; meanwhile, the mechanical property of the epoxy solid electrolyte is obviously improved, and the epoxy solid electrolyte is suitable for structural electrochemical energy storage devices.)

1. An epoxy-based solid electrolyte with high strength and high ionic conductivity, which comprises the following components in parts by weight:

2. the epoxy resin of claim 1, wherein: the epoxy resin is composed of at least one of bifunctional epoxy resin and polyfunctional epoxy resin. The bifunctional epoxy resin is bisphenol A type epoxy resin or bisphenol F type epoxy resin, preferably medium viscosity grades such as E51, NPEF-170 and the like, but not limited to the grades. The multifunctional epoxy resin is a trifunctional epoxy resin or a tetrafunctional epoxy resin, and preferably a multifunctional epoxy resin such as 4, 5-epoxyhexane-1, 2-dicarboxylic acid diglycidyl ester (TDE-85) and 4,4' -diaminodiphenylmethane epoxy resin (AG-80), but not limited to the above grades.

3. The curing agent of claim 1, being at least one of benzophenonetetracarboxylic dianhydride (BTDA), diaminodiphenyl sulfone (DDS), and polyetheramine (D230).

4. The ionic liquid according to claim 1, which is one of imidazole ionic liquid and pyridine ionic liquid. The imidazole ionic liquid is preferably 1-ethyl-3-methylimidazolium bis (trifluoromethanesulfonyl) imide (EMIM-TFSI) or 1-ethyl-3-methylimidazolium tetraborate (EMIM BF)₄) But is not limited thereto. The pyridine ionic liquid is preferably 1-ethylpyridine hydrochloride (C)₇H₁₀ClN), 1-ethylpyridine hydrobromide (C)₇H₁₀BrN), but is not limited thereto.

5. The lithium salt of claim 1 being lithium bistrifluoromethanesulfonylimide (LiTFSI) and hexafluorophosphoric acidLithium (LiPF)₆) At least one of (1).

6. The surface-pretreated chopped carbon fiber according to claim 1, which has a length of 0.5 to 2mm and is obtained by subjecting a commercial carbon fiber to surface pretreatment.

7. The surface pretreatment process for surface-pretreating chopped carbon fibers according to claim 1, comprising the steps of:

(a) chopping: the commercial continuous carbon fibers are cut into chopped carbon fibers of a desired length or directly used as raw materials.

(b) Removing sizing agent: soaking the chopped carbon fibers in an acetone solution at the temperature of 60-80 ℃ for 12-36 h, and then carrying out vacuum drying to remove the redundant solvent; or heating the chopped carbon fibers in inert gas at 400-600 ℃ for 0.1-1 h. The carbon fibers are treated in at least one of the above-described ways to remove sizing agents from the surface of commercial carbon fibers.

(c) Introduction of surface functional groups: soaking the chopped carbon fibers without the sizing agent in a strong acid solution or a strong base solution at the temperature of 30-80 ℃ for 6-36 h, and then washing and drying the chopped carbon fibers with deionized water; or the chopped carbon fiber without the sizing agent is put in air at 400-500 ℃ for oxidation treatment for 0.1-1 h. And carrying out surface treatment on the carbon fiber in at least one mode to introduce oxygen-containing functional groups on the surface of the carbon fiber.

8. The strong acid solution of claim 7 is at least one of concentrated nitric acid and concentrated sulfuric acid. The strong alkali solution is sodium hydroxide solution, and the concentration range is as follows: 0.1 to 1 mol/L.

9. The method of claim 1, wherein the method comprises the steps of:

(a) mixing: dissolving 50-70 parts of lithium salt in 120-160 parts of ionic liquid to obtain an ionic liquid electrolyte; then adding 100 parts of epoxy resin and 1-6 parts of surface pretreatment chopped carbon fiber into the ionic liquid electrolyte, and uniformly mixing at 40-70 ℃; and then adding 35-45 parts of curing agent, and uniformly mixing to obtain a premixed solution.

(b) And (3) curing: and (3) curing the premixed solution at 75-160 ℃ for 2-6 h, and cooling to room temperature to obtain the epoxy solid electrolyte.

10. The epoxy-based solid electrolyte with high strength and high ionic conductivity according to claim 1, which is used for solid aluminum-shell lithium batteries, solid lithium pouch batteries, lithium metal batteries and fiber-reinforced structural solid batteries.

Technical Field

The invention belongs to the field of structural energy storage, and provides an epoxy solid electrolyte with high strength and high ionic conductivity, and a preparation method and application thereof.

Background

In the fields of aerospace and automobiles, the fiber reinforced polymer composite material is used for replacing metal, so that the light weight of the structure can be realized, and further the effects of saving energy, reducing emission, reducing cost and improving working efficiency are achieved. The composite material structure providing mechanical bearing capacity and the battery providing energy storage are integrated, a structural energy storage device with the functions of structural bearing and energy storage is developed, and the method has important significance for the development of new-generation transportation tools. The solid lithium metal battery based on the metal lithium anode and the solid electrolyte has the advantages of high energy density, good safety, good long-term stability and the like, and has good application prospects in the fields of aerospace and automobiles. However, the current solid-state battery does not have structural bearing capacity, and the development of a solid electrolyte with excellent mechanical properties and high ion conductivity is a key for the development of structural solid-state batteries.

The organic solid polymer electrolyte has the characteristics of good electrode compatibility, small contact impedance and the like, and is the key point of the relevant research of the solid electrolyte. In recent years, efforts have been made to develop electrolytes based on polyethylene oxide, polyethylene carbonate, polyvinylidene fluoride-hexafluoropropylene copolymer, and the like. Most of the polymer-based electrolytes have excellent electrochemical characteristics, and the room-temperature ionic conductivity can reach 10^-4The polymer electrolytes are difficult to be compatible with fiber reinforced polymer composite materials and are not beneficial to the integration between a bearing structure and an energy storage structure, for example, Teyi et al prepares a polyethylene oxide based polymer electrolyte, although the ionic conductivity is as high as 1.2 × 10 at room temperature^-4S/cm, but the Young modulus is only a few MPa, so that the application requirement of the structural solid electrolyte is difficult to meet, and the development of the solid electrolyte with high strength and high ionic conductivity is urgently needed.

The epoxy resin has the advantages of high strength, large modulus, high thermal stability, high chemical stability and the like, and is the most common resin matrix in the aviation composite material. However, common epoxy resins have no ion transport ability and cannot be directly used as electrolyte materials. By introducing immiscible ionic liquid electrolyte into epoxy resin, a solid electrolyte with coexisting structure bearing and ion transport phases can be formed, and the electrolyte is hopeful to be used as an electrolyte of a structural solid battery. However, the increase in ionic conductivity of ionic liquid-modified epoxy resins is always accompanied by a decrease in mechanical strength and modulus. In order to obtain a solid electrolyte with both high mechanical strength and high ionic conductivity, further modification of the epoxy-ionic liquid system is required. For example, Zhangming et al prepared an organoclay-reinforced epoxy-ionic liquid composite electrolyte with Young's modulus of 211MPa and ionic conductivity of 0.09 mS/cm; meanwhile, the silicon dioxide reinforced epoxy-polyethylene glycol solid electrolyte is prepared by the method, and the Young modulus of the solid electrolyte is 135MPa, and the ionic conductivity of the solid electrolyte is 0.086 mS/cm. Related researches show that the introduction of nanoparticles into a polymer matrix is beneficial to improving the mechanical property and ionic conductivity of the matrix, but the improvement effect on the mechanical property and the ionic conductivity is limited, and the requirements of structural solid electrolytes cannot be met.

Disclosure of Invention

The purpose of the invention is as follows: aiming at the problems of poor mechanical property and poor compatibility with fiber reinforced composite materials of the existing polymer solid electrolyte, the invention provides an epoxy solid electrolyte with high strength and high ionic conductivity, and a preparation method and application thereof.

The technical scheme is as follows: the invention relates to an epoxy solid electrolyte with high strength and high ionic conductivity, a preparation method and application thereof.

(A) The epoxy solid electrolyte mainly comprises the following components in parts by weight: 100 parts of epoxy resin, 35-45 parts of curing agent, 120-160 parts of ionic liquid, 50-70 parts of lithium salt and 1-6 parts of surface pretreatment chopped carbon fiber.

The epoxy resin is at least one of bifunctional epoxy resin and polyfunctional epoxy resin.

The bifunctional epoxy resin is bisphenol A type epoxy resin or bisphenol F type epoxy resin, preferably medium viscosity grades such as E51, NPEF-170 and the like, but not limited to the grades.

The multifunctional epoxy resin is a trifunctional epoxy resin or a tetrafunctional epoxy resin, and preferably a multifunctional epoxy resin such as 4, 5-epoxyhexane-1, 2-dicarboxylic acid diglycidyl ester (TDE-85) and 4,4' -diaminodiphenylmethane epoxy resin (AG-80), but not limited to the above grades.

The curing agent is at least one of benzophenonetetracarboxylic dianhydride (BTDA), diaminodiphenyl sulfone (DDS) and polyether amine (D230).

The ionic liquid is at least one of imidazole ionic liquid and pyridine ionic liquid.

The imidazole ionic liquid is preferably 1-ethyl-3-methylimidazolium bis (trifluoromethanesulfonyl) imide (EMIM-TFSI) or 1-ethyl-3-methylimidazolium tetraborate (EMIM BF)₄) But is not limited thereto.

The pyridine ionic liquid is preferably 1-ethylpyridine hydrochloride (C)₇H₁₀ClN), 1-ethylpyridine hydrobromide (C)₇H₁₀BrN), but is not limited thereto.

The lithium salt is lithium bistrifluoromethanesulfonylimide (LiTFSI) and lithium hexafluorophosphate (LiPF)₆) At least one of (1).

The length of the surface-pretreated chopped carbon fiber is 0.5-2 mm.

(B) The surface-pretreated chopped carbon fiber is obtained by surface pretreatment of commercial carbon fiber, and the surface pretreatment process comprises the following steps:

chopping: the commercial continuous carbon fibers are cut into the chopped carbon fibers, or the commercial chopped carbon fibers are directly adopted as raw materials.

Removing sizing agent: soaking the chopped carbon fibers in an acetone solution at the temperature of 60-80 ℃ for 12-36 h, and then carrying out vacuum drying to remove the redundant solvent; or heating the chopped carbon fibers in inert gas at 400-600 ℃ for 0.1-1 h. And treating the carbon fibers in at least one mode to remove the sizing agent on the surfaces of the carbon fibers.

Introducing surface functional groups: the chopped carbon fibers without the sizing agent are placed in a strong acid or strong base solution at the temperature of 30-80 ℃ for treatment for 6-36 hours, then the chopped carbon fibers are washed and dried by deionized water, the strong acid solution is at least one of concentrated nitric acid and concentrated sulfuric acid, and the strong base solution is a sodium hydroxide solution (0.1-1 mol/L); or the chopped carbon fiber without the sizing agent is put in air at 400-500 ℃ for oxidation treatment for 0.1-1 h. And treating the surface of the carbon fiber in at least one mode to introduce oxygen-containing functional groups on the surface of the carbon fiber.

(C) The preparation method of the chopped carbon fiber reinforced epoxy-based solid electrolyte comprises the following steps:

firstly, dissolving 50-70 parts of lithium salt in 120-160 parts of ionic liquid to obtain an ionic liquid electrolyte;

secondly, adding 60-80 parts of bifunctional epoxy resin, 20-40 parts of polyfunctional epoxy resin and 1-6 parts of surface pretreatment chopped carbon fiber into the ionic liquid electrolyte, and uniformly stirring at 40-70 ℃;

thirdly, adding 35-45 parts of curing agent into the mixed system, and dispersing uniformly to obtain a premixed solution of the epoxy solid electrolyte;

and fourthly, curing the premixed solution at 75-160 ℃ for 2-6 h, and cooling to room temperature to obtain the epoxy solid electrolyte.

(D) The epoxy solid electrolyte is used for solid aluminum shell lithium batteries, solid soft package lithium batteries, lithium metal batteries and fiber reinforced structural solid batteries.

Compared with the prior art, the invention has the innovation points that:

the carbon fiber is used as a reinforcing material and is widely applied to the field of various composite materials. However, since carbon fibers themselves have good electronic conductivity, such as being used as a reinforcing material for a polymer electrolyte, the risk of short-circuiting of a battery is greatly increased, and thus cannot be applied to a polymer electrolyte. The chopped carbon fibers are subjected to surface pretreatment, so that the electronic conductivity of the carbon fibers is greatly reduced, and the short circuit risk of a battery is effectively avoided by adding the chopped carbon fibers into a polymer electrolyte. In addition, the surface of the carbon fiber is pretreated, rich oxygen-containing functional groups are introduced to the surface of the carbon fiber, and the oxygen-containing functional groups can generate Lewis acid action with lithium salt, so that the dissociation of the lithium salt is accelerated, and the concentration of free lithium ions in an electrolyte system is greatly improved.

Secondly, in the traditional ionic liquid modified epoxy solid electrolyte, most of the ionic liquid phase is distributed in the epoxy resin phase in an isolated manner, so that an ionic conduction path cannot be formed, and further the ionic conductivity of the electrolyte is low. Chopped carbon fibers are a typical one-dimensional material having a very large aspect ratio. The surface-pretreated chopped carbon fibers are dispersed in the epoxy-based solid electrolyte, lithium ions can be transmitted along the interface of the carbon fibers and the epoxy resin, and then mutually isolated ionic liquids are connected in series to form a three-dimensional ionic conductive network, so that the ionic conductivity of the electrolyte is greatly improved.

The carbon fiber has very high strength and modulus, and the chopped carbon fiber modified polymer has obvious reinforcing and toughening effects. However, the common chopped carbon fibers are difficult to be uniformly dispersed in the resin matrix, and have poor interface compatibility with the matrix, which is not favorable for the reinforcing effect of the matrix. The surface-pretreated chopped carbon fibers can be uniformly dispersed in an epoxy-based solid electrolyte, have good interface compatibility with a matrix, and have obvious reinforcing and toughening effects.

The epoxy solid electrolyte has high strength and high ionic conductivity, and is suitable for structural electrochemical energy storage devices. The strength of the common polymer solid electrolyte is lower, and the assembled solid battery has no structural strength; the solid battery assembled by the epoxy solid electrolyte has the functions of avoiding battery bulge, inhibiting lithium dendritic crystal growth and the like, and the assembled solid battery also has the function of structural support, so that the effect of structural lightweight is remarkable.

Drawings

FIG. 1 is a sample diagram of an epoxy-based solid electrolyte prepared according to the present invention

FIG. 2 is a tensile stress-strain curve of an epoxy-based solid electrolyte prepared according to the present invention

FIG. 3 shows the capacity of the solid-state lithium ion battery prepared according to the present invention at different current densities

Detailed Description

The present invention is illustrated by way of the following specific examples, which are not intended to be limiting.