Multifunctional carbon fiber composite electrolyte and preparation method and application thereof

Abstract

The invention belongs to the technical field of electrochemical energy storage, and discloses a multifunctional carbon fiber composite electrolyte and a preparation method and application thereof. The multifunctional carbon fiber composite electrolyte comprises an epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer and a mixed electrolyte layer which are laminated. According to the preparation method, the balance of mechanical properties and ionic conductivity is realized by optimizing a double-phase structure formed by mixing the epoxy resin and the ionic liquid and controlling curing dynamics and microphase separation behaviors, and high filling of the carbon fibers is realized by utilizing a vacuum-assisted compression molding process, so that the volume fraction of the fibers is remarkably increased, and interlayer gaps are reduced. And moreover, the added mixed electrolyte layer has a layered structure, so that the thermal stability and the electrochemical performance can be improved at the same time. The multifunctional carbon fiber composite electrolyte provided by the invention has relatively high energy density and mechanical properties, and is suitable for being applied to the fields requiring light weight, multifunctionality and high safety.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical energy storage, and in particular to a multifunctional carbon fiber composite electrolyte and a preparation method and application thereof. Background Art

[0002] Existing electrochemical energy storage devices have problems such as low specific capacity, insufficient safety and poor mechanical properties in structural applications. Structural battery technology that integrates energy storage and load-bearing capacity into a single material has become a research hotspot. However, the current multifunctional structural batteries based on carbon fiber and polymer electrolytes have problems such as low fiber volume fraction, uneven thickness, poor thermal stability and insufficient interface bonding strength, which seriously limit their commercial application. Summary of the invention

[0003] The purpose of the present invention is to provide a multifunctional carbon fiber composite electrolyte and its preparation method and application, so as to solve the problems of low fiber volume fraction, uneven thickness, poor thermal stability and insufficient interface bonding strength existing in the existing multifunctional structural batteries based on carbon fiber and polymer electrolyte.

[0004] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0005] The present invention provides a multifunctional carbon fiber composite electrolyte, which comprises an epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer and a mixed electrolyte layer stacked in sequence; the mass fraction of the epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer in the multifunctional carbon fiber composite electrolyte is 50-80%;

[0006] The epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer comprises a laminated epoxy resin solid polymer electrolyte functional layer and a carbon fiber layer; the volume fraction of the carbon fiber layer in the epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer is 40-60%.

[0007] Preferably, in the multifunctional carbon fiber composite electrolyte, the preparation method of the epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer comprises the following steps:

[0008] (1) mixing bisphenol A epoxy resin, a curing agent, a catalyst and a liquid composite electrolyte, and performing graded curing to obtain an epoxy resin solid polymer electrolyte;

[0009] (2) coating the epoxy resin solid polymer electrolyte on carbon fiber and performing vacuum assisted compression molding to obtain an epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer.

[0010] Preferably, in the multifunctional carbon fiber composite electrolyte, in the preparation method of the epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer, in step (1), the curing agent includes one or more of hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, diethylenetriamine, and 4,4'-diaminodiphenylmethane;

[0011] The catalyst includes N,N-dimethylbenzylamine;

[0012] The mass ratio of the bisphenol A epoxy resin to the curing agent is 10:8 to 10:10;

[0013] The mass of the catalyst is 0.5-2% of the mass of the bisphenol A epoxy resin.

[0014] Preferably, in the multifunctional carbon fiber composite electrolyte, in the method for preparing the epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer, in step (1), the liquid composite electrolyte comprises a mixture of a lithium salt, an ionic liquid and a solvent;

[0015] The lithium salt includes LiClO 4 、LiPF 6 , LiBF 4 , LiTFSI or more;

[0016] The ionic liquid includes one or more of 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide, and 1-butyl-3-methylimidazolium methanesulfonate;

[0017] The concentration of the lithium salt in the liquid composite electrolyte is 0.5 to 2 mol / L;

[0018] The volume fraction of the ionic liquid in the liquid composite electrolyte is 40 to 80%;

[0019] The mass fraction of the liquid composite electrolyte in the epoxy resin solid polymer electrolyte is 30-50%.

[0020] Preferably, in the multifunctional carbon fiber composite electrolyte, in the method for preparing the epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer, in step (1), the graded curing is divided into three or four stages;

[0021] The temperature of the first stage curing is 60-80°C, and the time of the first stage curing is 120-300 minutes;

[0022] The temperature of the second stage curing is 100-120°C, and the time of the second stage curing is 120-280 minutes;

[0023] The temperature of the third stage curing is 130-150°C, and the time of the third stage curing is 60-250 minutes;

[0024] The temperature of the fourth stage curing is 160-180°C, and the time of the fourth stage curing is 30-140 minutes.

[0025] Preferably, in the multifunctional carbon fiber composite electrolyte, in the preparation method of the epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer, in step (2), the conditions of the vacuum assisted compression molding include: pressure of 80 to 120 bar, temperature of 80 to 150°C, insulation time of 2 to 6h, vacuum degree of 0.01 to 0.05mbar, and heating rate to the required temperature of 2 to 5°C / min.

[0026] Preferably, in the multifunctional carbon fiber composite electrolyte, the mixed electrolyte layer comprises a mixture of epoxy resin-based solid electrolyte and functional materials;

[0027] The mass fraction of the epoxy resin-based solid electrolyte in the mixed electrolyte layer is 50-70%;

[0028] The functional material comprises two of a liquid electrolyte, an inorganic filler, and a toughening material;

[0029] The liquid electrolyte includes a mixture of LiTFSI, 1-ethyl-3-methylimidazolium tetrafluoroborate, and ethylene carbonate;

[0030] The inorganic filler includes one or more of lithium oxide, silicon dioxide, aluminum oxide, and lithium ion conductive ceramics;

[0031] The toughening material includes polyvinylidene fluoride and / or polyvinyl alcohol;

[0032] The mass fraction of the liquid electrolyte in the mixed electrolyte layer is 20-40%;

[0033] The mass fraction of the inorganic filler in the mixed electrolyte layer is 10 to 30%;

[0034] The mass fraction of the toughening material in the mixed electrolyte layer is 3-20%.

[0035] Preferably, in the multifunctional carbon fiber composite electrolyte, the method for preparing the mixed electrolyte layer comprises the following steps:

[0036] The epoxy resin-based solid electrolyte is mixed with the functional material, cast or coated to form a film, and then graded cured to obtain a mixed electrolyte layer;

[0037] Wherein, in the method for preparing the mixed electrolyte layer, the graded curing is divided into three or four stages;

[0038] The temperature of the first stage curing is 60-80°C, and the time of the first stage curing is 120-300 minutes;

[0039] The temperature of the second stage curing is 100-120°C, and the time of the second stage curing is 120-280 minutes;

[0040] The temperature of the third stage curing is 130-150°C, and the time of the third stage curing is 60-250 minutes;

[0041] The temperature of the fourth stage curing is 160-180°C, and the time of the fourth stage curing is 30-140 minutes.

[0042] The present invention also provides a method for preparing a multifunctional carbon fiber composite electrolyte, comprising the following steps:

[0043] The epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer and the mixed electrolyte layer are stacked and co-cured to obtain a multifunctional carbon fiber composite electrolyte;

[0044] The co-curing conditions include: a heating rate of 2 to 5°C / min to the required temperature, a temperature of 120 to 160°C, a pressure of 80 to 120 bar, a curing time of 2 to 6 hours, and a vacuum degree of 0.01 to 0.05 mbar.

[0045] The present invention also provides an application of a multifunctional carbon fiber composite electrolyte in the preparation of a multifunctional structural battery.

[0046] It can be seen from the above technical solution that compared with the prior art, the present invention has the following beneficial effects:

[0047] When preparing the epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer, the present invention optimizes the dual-phase structure of the epoxy resin and ionic liquid mixture, controls the curing kinetics and microphase separation behavior, achieves a balance between mechanical properties and ionic conductivity, and then uses a vacuum-assisted compression molding process to achieve a high filling of carbon fibers, significantly improves the fiber volume fraction, and reduces interlayer gaps. The prepared mixed electrolyte layer has a layered structure that can simultaneously improve thermal stability and electrochemical performance.

[0048] The multifunctional structural battery prepared by the multifunctional carbon fiber composite electrolyte provided by the present invention can have a discharge capacity of 120 to 135 mAh / g, has high energy density and mechanical properties, and is very suitable for use in fields requiring lightweight, multifunctionality and high safety, such as: in the aerospace field, the integration of the fuselage and battery of an unmanned aerial vehicle (UAV) or aircraft structural batteries; in robots and wearable devices, the integrated design of the battery and skeleton in bionic robots or industrial robots, or high-strength thin batteries for high-end wearable devices such as smart watches and smart glasses; in the automotive and transportation field, structural batteries for electric vehicles such as doors, floors or roofs , rail transit vehicles such as train car siding; renewable energy storage, energy storage units in wind turbine blades, or rooftop batteries to support smart buildings; consumer electronics and small energy storage devices, structural batteries for new smartphones and tablets, or small modular battery packs for home energy storage devices; national defense and military equipment, military drones, electric chariots, etc. that require lightweight and multifunctional energy storage devices, or wearable military equipment, such as embedded batteries in communication devices; special environment equipment, deep-sea probes, batteries combined with load-bearing structures for long-term underwater missions, or polar scientific research equipment, requiring multifunctional batteries that are resistant to high and low temperatures. DETAILED DESCRIPTION

[0049] The present invention provides a multifunctional carbon fiber composite electrolyte, which comprises an epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer and a mixed electrolyte layer stacked in sequence; the mass fraction of the epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer in the multifunctional carbon fiber composite electrolyte is 50-80%;

[0050] The epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer comprises a laminated epoxy resin solid polymer electrolyte functional layer and a carbon fiber layer; the volume fraction of the carbon fiber layer in the epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer is 40-60%.

[0051] In the present invention, the mass fraction of the epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer in the multifunctional carbon fiber composite electrolyte is preferably 50-70%, more preferably 55-65%, and more preferably 60%.

[0052] In the present invention, the volume fraction of the carbon fiber layer in the epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer is preferably 45-60%, more preferably 48-55%, and even more preferably 52%.

[0053] In the present invention, the preparation method of the epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer preferably comprises the following steps:

[0054] (1) mixing bisphenol A epoxy resin, a curing agent, a catalyst and a liquid composite electrolyte, and performing graded curing to obtain an epoxy resin solid polymer electrolyte;

[0055] (2) coating the epoxy resin solid polymer electrolyte on carbon fiber and performing vacuum assisted compression molding to obtain an epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer.

[0056] In the present invention, in the preparation method of the epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer, in step (1), the method of mixing the bisphenol A epoxy resin, the curing agent, the catalyst and the liquid composite electrolyte is preferably: the bisphenol A epoxy resin and the curing agent are mixed, and then the catalyst and the liquid composite electrolyte are added in sequence for mixing.

[0057] In the present invention, in the preparation method of the epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer, in step (1), the curing agent preferably includes one or more of hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, diethylenetriamine, and 4,4'-diaminodiphenylmethane, and further preferably includes hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, diethylenetriamine or 4,4'-diaminodiphenylmethane, and more preferably hexahydrophthalic anhydride.

[0058] In the present invention, in the method for preparing the epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer, in step (1), the mass ratio of the bisphenol A epoxy resin to the curing agent is preferably 10:8 to 10:10, more preferably 10:8.5 to 10:9.5, and more preferably 10:9.

[0059] In the present invention, in the method for preparing the epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer, in step (1), the catalyst preferably includes N,N-dimethylbenzylamine.

[0060] In the present invention, in the method for preparing the epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer, in step (1), the mass of the catalyst is preferably 0.5-2% of the mass of the bisphenol A epoxy resin, more preferably 0.8-1.2%, and more preferably 1%.

[0061] In the present invention, in the method for preparing the epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer, in step (1), the liquid composite electrolyte preferably comprises a mixture of a lithium salt, an ionic liquid and a solvent.

[0062] In the present invention, the lithium salt preferably includes LiClO 4 、LiPF 6, LiBF 4 , LiTFSI, and preferably LiClO 4 、LiPF 6 , LiBF 4 or LiTFSI, more preferably LiTFSI.

[0063] In the present invention, the concentration of the lithium salt in the liquid composite electrolyte is preferably 0.5 to 2 mol / L, more preferably 0.8 to 1.2 mol / L, and even more preferably 1 mol / L.

[0064] In the present invention, the ionic liquid preferably includes one or more of 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide, and 1-butyl-3-methylimidazolium methyl sulfonate, and further preferably includes 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide or 1-butyl-3-methylimidazolium methyl sulfonate, and more preferably 1-ethyl-3-methylimidazolium tetrafluoroborate.

[0065] In the present invention, the volume fraction of the ionic liquid in the liquid composite electrolyte is preferably 40 to 80%, more preferably 40 to 60%, and even more preferably 50%.

[0066] In the present invention, the solvent preferably includes one or more of ethylene carbonate, dimethyl carbonate, diethyl carbonate, dimethoxyethane, and tetrahydrofuran, and further preferably includes ethylene carbonate, dimethyl carbonate, diethyl carbonate, dimethoxyethane or tetrahydrofuran, and more preferably is ethylene carbonate.

[0067] In the present invention, the mass fraction of the liquid composite electrolyte in the epoxy resin solid polymer electrolyte is preferably 30 to 50%, more preferably 30 to 40%, and more preferably 30%.

[0068] In the present invention, in the method for preparing the epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer, in step (1), the graded curing is preferably divided into three or four stages, and more preferably four stages.

[0069] In the present invention, in the preparation method of the epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer, in step (1), the temperature of the first stage curing of the graded curing is preferably 60-80°C, more preferably 70-80°C, and more preferably 80°C; the time of the first stage curing is preferably 120-300min, more preferably 250-300min, and more preferably 300min.

[0070] In the present invention, in the preparation method of the epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer, in step (1), the temperature of the second stage curing of the graded curing is preferably 100-120°C, more preferably 100-110°C, and more preferably 100°C; the time of the second stage curing is preferably 120-280min, more preferably 240-280min, and more preferably 280min.

[0071] In the present invention, in the preparation method of the epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer, in step (1), the temperature of the third stage curing of the graded curing is preferably 130-150°C, more preferably 130-140°C, and more preferably 130°C; the time of the third stage curing is preferably 60-250min, more preferably 180-250min, and more preferably 250min.

[0072] In the present invention, in the method for preparing the epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer, in step (1), the temperature of the fourth stage curing of the graded curing is preferably 160-180°C, more preferably 160-170°C, and more preferably 160°C; the time of the fourth stage curing is preferably 30-140min, more preferably 80-140min, and more preferably 140min.

[0073] In an embodiment of the present invention, in the method for preparing the epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer, in step (2), the carbon fiber is preferably a T700 spread tow.

[0074] In the present invention, in the preparation method of the epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer, in step (2), the conditions of the vacuum assisted compression molding include: the pressure is preferably 80-120 bar, and more preferably 80, 110 bar; the temperature is preferably 80-150°C, and more preferably 80, 120, 150°C; the insulation time is preferably 2-6h, and more preferably 3-4.5h, and more preferably 3.5h; the vacuum degree is preferably 0.01-0.05mbar, and more preferably 0.01-0.03mbar, and more preferably 0.02mbar; the rate of heating to the required temperature is preferably 2-5°C / min, and more preferably 2-4°C / min, and more preferably 2°C / min.

[0075] In the present invention, in the preparation method of the epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer, in step (2), after the vacuum-assisted compression molding, the step preferably further comprises: cooling to room temperature. The cooling rate to room temperature is preferably 2 to 10°C / min, more preferably 4 to 7°C / min, and more preferably 5°C / min.

[0076] In the present invention, the mixed electrolyte layer includes a mixture of an epoxy resin-based solid electrolyte and a functional material.

[0077] In the present invention, in the mixed electrolyte layer, the epoxy resin-based solid electrolyte preferably includes raw materials of the following components: bisphenol A epoxy resin, a curing agent, a catalyst and a liquid composite electrolyte.

[0078] In the present invention, in the epoxy resin-based solid electrolyte in the mixed electrolyte layer, the curing agent preferably includes one or more of hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, diethylenetriamine, and 4,4'-diaminodiphenylmethane, and further preferably includes hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, diethylenetriamine or 4,4'-diaminodiphenylmethane, and more preferably hexahydrophthalic anhydride.

[0079] In the present invention, in the epoxy resin-based solid electrolyte in the mixed electrolyte layer, the mass ratio of the bisphenol A epoxy resin to the curing agent is preferably 10:8 to 10:10, more preferably 10:8.5 to 10:9.5, and more preferably 10:9.

[0080] In the present invention, in the epoxy resin-based solid electrolyte in the mixed electrolyte layer, the catalyst preferably includes N,N-dimethylbenzylamine.

[0081] In the present invention, in the epoxy resin-based solid electrolyte in the mixed electrolyte layer, the mass of the catalyst is preferably 0.5 to 2% of the mass of the bisphenol A epoxy resin, more preferably 0.8 to 1.2%, and even more preferably 1%.

[0082] In the present invention, in the epoxy resin-based solid electrolyte in the mixed electrolyte layer, the liquid composite electrolyte preferably includes a mixture of a lithium salt, an ionic liquid and a solvent.

[0083] In the present invention, the lithium salt preferably includes LiClO 4 、LiPF 6 , LiBF 4 , LiTFSI, and preferably LiClO 4 、LiPF 6 , LiBF 4or LiTFSI, more preferably LiTFSI.

[0084] In the present invention, the concentration of the lithium salt in the liquid composite electrolyte is preferably 0.5 to 2 mol / L, more preferably 0.8 to 1.2 mol / L, and even more preferably 1 mol / L.

[0085] In the present invention, the ionic liquid preferably includes one or more of 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide, and 1-butyl-3-methylimidazolium methyl sulfonate, and further preferably includes 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide or 1-butyl-3-methylimidazolium methyl sulfonate, and more preferably 1-ethyl-3-methylimidazolium tetrafluoroborate.

[0086] In the present invention, the volume fraction of the ionic liquid in the liquid composite electrolyte is preferably 40 to 80%, more preferably 40 to 60%, and even more preferably 50%.

[0087] In the present invention, the solvent preferably includes one or more of ethylene carbonate, dimethyl carbonate, diethyl carbonate, dimethoxyethane, and tetrahydrofuran, and further preferably includes ethylene carbonate, dimethyl carbonate, diethyl carbonate, dimethoxyethane or tetrahydrofuran, and more preferably is ethylene carbonate.

[0088] In the present invention, the mass fraction of the liquid composite electrolyte in the epoxy resin-based solid electrolyte is preferably 30 to 50%, more preferably 30 to 40%, and more preferably 30%.

[0089] In the present invention, in the mixed electrolyte layer, the mass fraction of the epoxy resin-based solid electrolyte in the mixed electrolyte layer is preferably 50 to 70%, more preferably 50 to 60%, and more preferably 50%.

[0090] In the present invention, in the mixed electrolyte layer, the functional material preferably includes two of a liquid electrolyte, an inorganic filler, and a toughening material, and more preferably includes two of a liquid electrolyte and a toughening material.

[0091] In the present invention, in the mixed electrolyte layer, the liquid electrolyte preferably comprises a mixture of LiTFSI, 1-ethyl-3-methylimidazolium tetrafluoroborate, and ethylene carbonate.

[0092] In the present invention, in the mixed electrolyte layer, the concentration of LiTFSI in the liquid electrolyte is preferably 1 mol / L.

[0093] In the present invention, in the mixed electrolyte layer, the volume fraction of the 1-ethyl-3-methylimidazolium tetrafluoroborate in the liquid electrolyte is preferably 50 to 90%, more preferably 60 to 80%, and even more preferably 70%.

[0094] In the present invention, the mass fraction of the liquid electrolyte in the mixed electrolyte layer is preferably 20 to 40%, more preferably 25 to 35%, and even more preferably 30%.

[0095] In the present invention, in the mixed electrolyte layer, the inorganic filler preferably includes one or more of lithium oxide, silicon dioxide, aluminum oxide, and lithium ion conductive ceramics, and further preferably includes lithium oxide, silicon dioxide, aluminum oxide or lithium ion conductive ceramics, and more preferably is lithium oxide.

[0096] In the present invention, the lithium ion conductive ceramic preferably comprises Li 7 La 3 Zr 2 O 12 .

[0097] In the present invention, the mass fraction of the inorganic filler in the mixed electrolyte layer is preferably 10 to 30%, more preferably 15 to 25%, and even more preferably 20%.

[0098] In the present invention, in the mixed electrolyte layer, the toughening material preferably includes polyvinylidene fluoride and / or polyvinyl alcohol, and more preferably polyvinylidene fluoride.

[0099] In the present invention, the mass fraction of the toughening material in the mixed electrolyte layer is preferably 3-20%, more preferably 10-20%, and more preferably 20%.

[0100] In the present invention, the method for preparing the mixed electrolyte layer preferably comprises the following steps:

[0101] The epoxy resin-based solid electrolyte is mixed with the functional material, cast into a film or coated into a film, and then graded cured to obtain a mixed electrolyte layer.

[0102] In the present invention, in the method for preparing the mixed electrolyte layer, the epoxy resin-based solid electrolyte is preferably mixed with the functional material and then vacuum degassed.

[0103] In the present invention, in the method for preparing the mixed electrolyte layer, the vacuum degree of the vacuum degassing is preferably 0.01 to 0.05 mbar, more preferably 0.01 to 0.03 mbar, and more preferably 0.02 mbar.

[0104] In the present invention, in the method for preparing the mixed electrolyte layer, the graded curing is preferably divided into three or four stages, and more preferably four stages.

[0105] In the present invention, in the method for preparing the mixed electrolyte layer, the temperature of the first stage curing of the graded curing is preferably 60-80°C, more preferably 70-80°C, and more preferably 80°C; the time of the first stage curing is preferably 120-300min, more preferably 250-300min, and more preferably 300min.

[0106] In the present invention, in the method for preparing the mixed electrolyte layer, the temperature of the second stage curing of the graded curing is preferably 100-120°C, more preferably 100-110°C, and more preferably 100°C; the time of the second stage curing is preferably 120-280min, more preferably 240-280min, and more preferably 280min.

[0107] In the present invention, in the method for preparing the mixed electrolyte layer, the temperature of the third stage curing of the graded curing is preferably 130-150°C, more preferably 130-140°C, and more preferably 130°C; the time of the third stage curing is preferably 60-250min, more preferably 180-250min, and more preferably 250min.

[0108] In the present invention, in the method for preparing the mixed electrolyte layer, the temperature of the fourth stage curing of the graded curing is preferably 160-180°C, more preferably 160-170°C, and more preferably 160°C; the time of the fourth stage curing is preferably 30-140min, more preferably 80-140min, and more preferably 140min.

[0109] The present invention also provides a method for preparing a multifunctional carbon fiber composite electrolyte, comprising the following steps:

[0110] The epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer and the mixed electrolyte layer are stacked and co-cured to obtain a multifunctional carbon fiber composite electrolyte.

[0111] In the present invention, the co-curing conditions include: the rate of heating to the desired temperature is preferably 2-5°C / min, more preferably 2.5-4°C / min, and more preferably 3°C / min; the temperature is preferably 120-160°C, more preferably 125-145°C, and more preferably 130°C; the pressure is preferably 80-120 bar, more preferably 90-110 bar, and more preferably 100 bar; the curing time is preferably 2-6h, more preferably 2.5-4.5h, and more preferably 3h; the vacuum degree is preferably 0.01-0.05mbar, more preferably 0.01-0.03mbar, and more preferably 0.02mbar.

[0112] The present invention also provides an application of a multifunctional carbon fiber composite electrolyte in the preparation of a multifunctional structural battery.

[0113] In the present invention, the application method is not limited, and any method known to those skilled in the art may be used.

[0114] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0115] Example 1

[0116] The present embodiment provides a multifunctional carbon fiber composite electrolyte, including a laminated epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer and a mixed electrolyte layer, and the interface between the two is fully bonded by co-curing. The preparation process is as follows: the epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer and the mixed electrolyte layer are laminated according to the design ratio to ensure that the surfaces of the two layers of materials are flat and well aligned; the laminated composite material is placed in a hot pressing device, heated to 130°C at a heating rate of 3°C / min, and a pressure of 100 bar is applied at 130°C for 3 hours, while maintaining the vacuum degree at 0.02 mbar to promote the interface bonding and mutual penetration between the two layers of materials; after the heat preservation is completed, the temperature is slowly lowered to room temperature to ensure the stability of the material structure; the mass fraction of the epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer is 60%;

[0117] The preparation method of epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer is as follows:

[0118] (1) Bisphenol A epoxy resin (manufacturer Nantong Xingchen Synthetic Materials Co., Ltd., brand E-51, epoxy value 0.51, viscosity 13000-15000 mPa·s (25°C)) and curing agent methyl hexahydrophthalic anhydride (MHHPA-95, anhydride content ≥95%) were mixed in a mass ratio of 10:9, and a catalyst N,N-dimethylbenzylamine (DMBA-1, density about 0.97 g / cm) was added at 1% by mass of the bisphenol A epoxy resin. 3 ), then adding a liquid composite electrolyte (including 1 mol / L lithium salt LiTFSI, 40vt% ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate and solvent ethylene carbonate) to mix, and performing four-stage graded curing, the first stage curing condition is 80°C, 300min, the second stage curing condition is 100°C, 280min, the third stage curing condition is 130°C, 250min, and the fourth stage curing condition is 160°C, 140min, to obtain an epoxy resin solid polymer electrolyte, the mass fraction of the liquid composite electrolyte is 30%;

[0119] (2) The epoxy resin solid polymer electrolyte is uniformly coated on the T700 spread tow (manufacturer: Toray Industries, Ltd., Japan, brand: T700 SC-12000), and vacuum-assisted compression molding is performed, with a heating rate of 2°C / min, pre-compression stage conditions: 80°C, 80 bar, vacuum degree 0.02 mbar, 0.5 h, molding stage conditions: 120°C, 110 bar, vacuum degree 0.02 mbar, 2 h, final curing conditions: 150°C, 110 bar, vacuum degree 0.02 mbar, 1 h, and then the temperature is decreased to room temperature at a rate of 5°C / min to obtain an epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer, and the volume fraction of the carbon fiber layer is 52%;

[0120] The preparation method of the mixed electrolyte layer is as follows:

[0121] A 50 wt% epoxy resin-based solid electrolyte (whose composition includes: bisphenol A epoxy resin (manufacturer Nantong Xingchen Synthetic Materials Co., Ltd., brand E-51, epoxy value 0.51, viscosity 13000-15000 mPa·s (25°C)), curing agent methyl hexahydrophthalic anhydride (MHHPA-95, anhydride content ≥95%), catalyst N,N-dimethylbenzylamine (DMBA-1, density about 0.97 g / cm 3), a liquid composite electrolyte (including 1 mol / L lithium salt LiTFSI, 40vt% ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate and solvent ethylene carbonate), the mass fraction of the liquid composite electrolyte in the epoxy resin-based solid electrolyte is 30%, the mass ratio of bisphenol A epoxy resin to the curing agent is 10:9, and the catalyst is 1% of the mass of bisphenol A epoxy resin), 30wt% liquid electrolyte (1 mol / LLiTFSI, 70vt% of a mixture of 1-ethyl-3-methylimidazolium tetrafluoroborate and ethylene carbonate), 20wt% toughening material polyvinylidene fluoride (weight average molecular weight 500,000) are mixed, degassed under a vacuum degree of 0.02mbar, and then coated to form a film, followed by four-stage graded curing, the first stage curing conditions are 80°C, 300min, the second stage curing conditions are 100°C, 280min, the third stage curing conditions are 130°C, 250min, and the fourth stage curing conditions are 160°C, 140min, to obtain a mixed electrolyte layer.

[0122] Example 2

[0123] This embodiment provides a multifunctional carbon fiber composite electrolyte. The difference from Embodiment 1 is that the mass fraction of the liquid composite electrolyte in the epoxy resin solid polymer electrolyte is modified to 50%, and other parameter conditions are the same as those in Embodiment 1.

[0124] The microdrop method was used to test the interfacial bonding strength between a single carbon fiber and the epoxy resin solid polymer electrolyte in the preparation of the epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer in Examples 1 and 2 without curing, and the method was as follows:

[0125] A single T700 carbon fiber with a length of 50 mm is cleaned with ethanol or acetone to remove surface contaminants; the fiber surface is observed under a microscope to ensure that it is clean and has no obvious defects; a liquid epoxy resin solid polymer electrolyte is accurately dripped into the middle of a single carbon fiber using a microinjection system, the volume of the droplet is controlled to have a diameter of 200 μm, and the solidification is performed according to the graded curing conditions of Example 1; the prepared fiber-droplet sample is fixed on a clamping device to ensure that the fiber is uniformly stressed during the test, the test sample is installed on a tensile testing machine, and the debonding behavior of the droplet on the fiber is measured by loading the tangential force at the droplet site, the loading speed is 0.3 mm / min, and the maximum debonding load Fmax is recorded, which is calculated by the formula: interface shear strength IFSS = maximum load Fmax ÷ (π × fiber diameter D × embedding length L of the droplet on the fiber).

[0126] According to the test results of Examples 1 and 2, as the mass fraction of the liquid composite electrolyte increases from 30% to 50%, the interface shear strength decreases by 66.5%.

[0127] Example 3

[0128] This embodiment provides a multifunctional carbon fiber composite electrolyte, which differs from Embodiment 1 in that the volume fraction of the ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate in the liquid composite electrolyte added during the preparation of the epoxy resin solid polymer electrolyte is modified to 50vt%, and other parameter conditions are the same as those in Embodiment 1.

[0129] Example 4

[0130] This embodiment provides a multifunctional carbon fiber composite electrolyte, which is different from Embodiment 1 in that the volume fraction of the ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate in the liquid composite electrolyte added during the preparation of the epoxy resin solid polymer electrolyte is modified to 60vt%, and other parameter conditions are the same as those in Embodiment 1.

[0131] Test Case

[0132] The performance of the multifunctional carbon fiber composite electrolyte obtained in Examples 1, 3 to 4 was tested according to the following test method:

[0133] (1) Tensile properties

[0134] The test is carried out according to the standards ASTM D3039 / D3039M (tensile properties test of fiber reinforced composite materials) and ISO 527 (tensile properties test of plastics). The test method is as follows:

[0135] Dumbbell-shaped or rectangular samples are prepared according to the standard, and the size meets the clamping requirements of the test equipment. An electronic tensile testing machine is used, equipped with a high-precision displacement sensor, with a loading speed of 3 mm / min. The Young's modulus is calculated by the slope of the linear part of the stress-strain curve, and the elongation at break is calculated by measuring the ratio of the total deformation at break to the initial length of the sample.

[0136] From the test results, it can be seen that the Young's modulus of Example 1 is 120 GPa and the elongation at break is 3.2%. The Young's modulus of Example 3 is 90 GPa and the elongation at break is 3.8%. The Young's modulus of Example 4 drops to 75 GPa and the elongation at break is 4.3%, but it still meets the load-bearing requirements of general structure batteries.

[0137] (2) Ionic conductivity

[0138] The test method is as follows:

[0139] Prepare a film sample with a thickness of 100 μm to ensure that there are no obvious defects; use an electrochemical workstation CHI equipped with an impedance test module and a stainless steel symmetrical electrode structure (stainless steel / film / stainless steel) to test in the frequency range of 0.1 Hz to 1 MHz and room temperature to 80 ° C. The calculation formula is σ = R × AL, σ: ionic conductivity (S / cm), L: film thickness (cm); R: impedance (Ω); A: electrode area (cm 2 ).

[0140] The test results show that the ionic conductivity of Example 1 is 3.5×10 -4 S / cm, Example 3 is 4.8×10 -4 S / cm, Example 4 is 6.1×10 -4 S / cm.

[0141] (3) Thermal stability

[0142] The test is carried out according to ASTM E537 (differential scanning calorimetry test standard) and ISO 11357 (differential scanning calorimetry analysis standard for plastics). The test method is as follows:

[0143] Weigh 10 mg of the sample, put it into an aluminum crucible and seal it. Test it with a differential scanning calorimeter at 30-300°C and a heating rate of 10°C / min under nitrogen protection, and record the initial decomposition temperature.

[0144] From the test results, it can be seen that the initial decomposition temperature of Example 1 is 160°C, that of Example 3 is 165°C, and that of Example 4 is 170°C.

[0145] Application Examples

[0146] The multifunctional carbon fiber composite electrolytes obtained in Examples 1, 3 and 4 are respectively assembled into battery modules. The preparation method of the battery module is as follows:

[0147] Electrode preparation

[0148] Positive electrode: LiFePO 4 Positive electrode material, conductive agent SuperP (manufacturer IMERYS (formerly Temeka), brand SUPER Li) and binder PVDF (weight average molecular weight 500,000) were mixed in a mass ratio of 80:10:10, dispersed with solvent NMP, and coated on an aluminum foil current collector, and then rolled and dried to obtain a positive electrode sheet;

[0149] Negative electrode: metal lithium sheet is selected and coated on the copper foil current collector, which is dried and rolled into a negative electrode sheet; pretreatment of multifunctional carbon fiber composite electrolyte

[0150] Cut the multifunctional carbon fiber composite electrolyte obtained in Example 1, 3 or 4 into a membrane structure matching the size of the electrode sheet, ensuring that the surface is flat and undamaged;

[0151] Battery stack assembly

[0152] In a glove box (dew point ≤ -40°C), stack the positive electrode sheet / multifunctional carbon fiber composite electrolyte / negative electrode sheet in this order; load the stacked electrode unit into an aluminum-plastic film shell, evacuate the shell and heat-seal it to obtain a soft-pack battery cell; after the battery is assembled, let it stand for 12 hours in a 25°C environment to ensure that the electrolyte fully infiltrates the electrode material; form the battery in a constant temperature environment (charge to the set voltage at 0.05C, let it stand, and then discharge at 0.1C, repeat twice), and then perform performance testing.

[0153] The LAND battery test system was used for constant current charge and discharge, with a current rate of 0.1C, a voltage range of 2.5 to 4.2V, and a test temperature of 25°C, and the first cycle discharge capacity and the capacity retention rate after 250 cycles of the above battery module were recorded. From the test results, it can be seen that the discharge capacity of the battery module prepared in Example 1 is 105mAh / g, and the capacity retention rate is 95% after 250 cycles; the discharge capacity of Example 3 reaches 120mAh / g, and the capacity retention rate is 93% after 250 cycles; and Example 4 reaches 135mAh / g, and the capacity retention rate is 90% after 250 cycles.

[0154] In summary, the multifunctional carbon fiber composite electrolyte prepared by the present invention can provide mechanical bearing function while still obtaining good electrochemical performance, with a discharge capacity of 105-135 mAh / g at a rate of 0.1C, and a capacity retention rate of 90-95% or more after 250 cycles, which is much higher than the general polymer composite electrolyte system with insufficient modification, showing higher stability and practicality. It can be applied to occasions with higher requirements for lightweight, multifunctionality and safety, such as unmanned aerial vehicle (UAV) fuselage battery integration, wearable devices and aerospace vehicles, showing potential commercial application prospects.

[0155] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A multifunctional carbon fiber composite electrolyte, characterized in that: The multifunctional carbon fiber composite electrolyte comprises an epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer and a mixed electrolyte layer stacked in sequence; the mass fraction of the epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer in the multifunctional carbon fiber composite electrolyte is 50-80%; The epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer comprises a laminated epoxy resin solid polymer electrolyte functional layer and a carbon fiber layer; the volume fraction of the carbon fiber layer in the epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer is 40-60%.

2. A multifunctional carbon fiber composite electrolyte according to claim 1, characterized in that: The preparation method of the epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer comprises the following steps: (1) mixing bisphenol A epoxy resin, a curing agent, a catalyst and a liquid composite electrolyte, and performing graded curing to obtain an epoxy resin solid polymer electrolyte; (2) coating the epoxy resin solid polymer electrolyte on carbon fiber and performing vacuum assisted compression molding to obtain an epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer.

3. A multifunctional carbon fiber composite electrolyte according to claim 2, characterized in that: In the preparation method of the epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer, in step (1), the curing agent includes one or more of hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, diethylenetriamine, and 4,4'-diaminodiphenylmethane; The catalyst includes N,N-dimethylbenzylamine; The mass ratio of the bisphenol A epoxy resin to the curing agent is 10:8 to 10:10; The mass of the catalyst is 0.5-2% of the mass of the bisphenol A epoxy resin.

4. A multifunctional carbon fiber composite electrolyte according to claim 2 or 3, characterized in that: In the preparation method of the epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer, in step (1), the liquid composite electrolyte includes a mixture of a lithium salt, an ionic liquid and a solvent; The lithium salt includes one or more of LiClO4, LiPF6, LiBF4, and LiTFSI; The ionic liquid includes one or more of 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide, and 1-butyl-3-methylimidazolium methanesulfonate; The concentration of the lithium salt in the liquid composite electrolyte is 0.5 to 2 mol / L; The volume fraction of the ionic liquid in the liquid composite electrolyte is 40 to 80%; The mass fraction of the liquid composite electrolyte in the epoxy resin solid polymer electrolyte is 30-50%.

5. The multifunctional carbon fiber composite electrolyte according to claim 2, characterized in that: In the method for preparing the epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer, in step (1), the graded curing is divided into three or four stages; The temperature of the first stage curing is 60-80°C, and the time of the first stage curing is 120-300 minutes; The temperature of the second stage curing is 100-120°C, and the time of the second stage curing is 120-280 minutes; The temperature of the third stage curing is 130-150°C, and the time of the third stage curing is 60-250 minutes; The temperature of the fourth stage curing is 160-180°C, and the time of the fourth stage curing is 30-140 minutes.

6. A multifunctional carbon fiber composite electrolyte according to claim 2 or 5, characterized in that: In the preparation method of the epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer, in step (2), the conditions of the vacuum assisted compression molding include: pressure of 80 to 120 bar, temperature of 80 to 150°C, insulation time of 2 to 6 hours, vacuum degree of 0.01 to 0.05 mbar, and heating rate to the required temperature of 2 to 5°C / min.

7. The multifunctional carbon fiber composite electrolyte according to claim 1, characterized in that: The mixed electrolyte layer includes a mixture of epoxy resin-based solid electrolyte and functional materials; The mass fraction of the epoxy resin-based solid electrolyte in the mixed electrolyte layer is 50-70%; The functional material includes two of a liquid electrolyte, an inorganic filler, and a toughening material; The liquid electrolyte includes a mixture of LiTFSI, 1-ethyl-3-methylimidazolium tetrafluoroborate, and ethylene carbonate; The inorganic filler includes one or more of lithium oxide, silicon dioxide, aluminum oxide, and lithium ion conductive ceramics; The toughening material includes polyvinylidene fluoride and / or polyvinyl alcohol; The mass fraction of the liquid electrolyte in the mixed electrolyte layer is 20 to 40%; The mass fraction of the inorganic filler in the mixed electrolyte layer is 10 to 30%; The mass fraction of the toughening material in the mixed electrolyte layer is 3-20%.

8. A multifunctional carbon fiber composite electrolyte according to claim 1 or 7, characterized in that: The preparation method of the mixed electrolyte layer comprises the following steps: The epoxy resin-based solid electrolyte is mixed with the functional material, cast or coated to form a film, and then graded cured to obtain a mixed electrolyte layer; Wherein, in the method for preparing the mixed electrolyte layer, the graded curing is divided into three or four stages; The temperature of the first stage curing is 60-80°C, and the time of the first stage curing is 120-300 minutes; The temperature of the second stage curing is 100-120°C, and the time of the second stage curing is 120-280 minutes; The temperature of the third stage curing is 130-150°C, and the time of the third stage curing is 60-250 minutes; The temperature of the fourth stage curing is 160-180°C, and the time of the fourth stage curing is 30-140 minutes.

9. The method for preparing a multifunctional carbon fiber composite electrolyte according to any one of claims 1 to 8, characterized in that: The following steps are involved: The epoxy resin solid polymer electrolyte-multifunctional carbon fiber composite layer and the mixed electrolyte layer are stacked and co-cured to obtain a multifunctional carbon fiber composite electrolyte; The co-curing conditions include: a heating rate of 2 to 5°C / min to the required temperature, a temperature of 120 to 160°C, a pressure of 80 to 120 bar, a curing time of 2 to 6 hours, and a vacuum degree of 0.01 to 0.05 mbar.

10. Use of a multifunctional carbon fiber composite electrolyte as claimed in any one of claims 1 to 8 or a multifunctional carbon fiber composite electrolyte prepared by the preparation method as claimed in claim 9 in preparing a multifunctional structural battery.