Elastomer solid polymer electrolyte, solid metal lithium battery and preparation method thereof

Abstract

The invention belongs to the field of new energy materials, and particularly relates to an elastomer solid polymer electrolyte, a solid metal lithium battery and a preparation method thereof. The preparation method of the elastomer solid polymer electrolyte comprises the following steps: providing a reaction mixture containing an acrylate monomer, a lithium salt, an initiator and a cross-linking agent, injecting the reaction mixture into a diaphragm, standing, and then sequentially carrying out microwave treatment and heat treatment. The elastomer solid-state polymer electrolyte has high electrochemical stability, and after the elastomer solid-state polymer electrolyte is applied to a solid-state lithium metal battery, the solid-state lithium metal battery can show good cycle stability.

Description

Technical Field

[0001] This invention belongs to the field of new energy materials, and specifically relates to elastomeric solid polymer electrolytes, solid metal lithium batteries and their preparation methods. Background Technology

[0002] Solid-state lithium batteries are widely recognized as the core development direction of next-generation energy storage systems due to their high energy density (>500Wh / kg) and inherent safety. However, current mainstream solid-state electrolytes face severe bottlenecks: rigid ceramic electrolytes suffer from poor interfacial contact (porosity >30%) and brittle fracture (short-circuit rate >60% after 100 cycles), requiring external pressure exceeding 100MPa to maintain ion channels; linear polymer electrolytes, such as PEO-based materials, are limited by low room temperature conductivity (<10). -4 With low S / cm and weak mechanical strength (Young's modulus < 0.1 GPa), it cannot effectively suppress lithium dendrite growth; traditional in-situ polymerized gel electrolytes cause interface peeling due to large free radical polymerization shrinkage stress (volume shrinkage rate > 15%), and the liquid precursor is not fully polymerized in the deep layer of the porous electrode (residual monomer > 10%).

[0003] Despite the advantages of elastomeric electrolytes reported in the literature in accommodating lithium metal volume changes, existing technologies still face three major unresolved challenges: small molecule plasticizers (such as dibutyl phthalate and polyethylene glycol) continuously leach out at a high voltage of 4.2V, catalyzing the dissolution of the cathode metal (NCM811 capacity retention rate <70% after 200 cycles); physical blending leads to separation of the porous framework-polymer phase, causing ion channel blockage and high-temperature interface peeling; and the thermal initiation process causes localized burst stress cracks due to the large temperature gradient (±10℃), and the mismatch between the initiator decomposition half-life and polymerization kinetics results in an excessively wide molecular weight distribution. Summary of the Invention

[0004] The purpose of this invention is to solve the problems of in-situ polymerization of monomer residues and poor battery cycle stability in existing elastomeric solid polymer electrolytes. This invention provides an elastomeric solid polymer electrolyte, its preparation method, and its application. This elastomeric solid polymer electrolyte has high ionic conductivity, and when applied to solid lithium metal batteries, it enables the solid lithium metal batteries to exhibit excellent cycle stability.

[0005] To achieve the above objectives, the present invention adopts the following technical solution.

[0006] In a first aspect, the present invention provides a method for preparing an elastomeric solid polymer electrolyte, comprising the following steps:

[0007] A reaction mixture comprising acrylate monomers, lithium salts, initiators and crosslinking agents is provided. The reaction mixture is injected into a diaphragm and allowed to stand, followed by microwave treatment and heat treatment in sequence.

[0008] The acrylate monomer has the structural formula CH2=C(R1)C(O)O-R2, where R is hydrogen (H) or methyl (CH3), and R2 is an alkyl or substituted alkyl. The general structural formula of the acrylate monomer is shown in structural formula I.

[0009]

[0010] This invention first provides a reaction mixture comprising acrylate monomers, lithium salts, an initiator, and a crosslinking agent. During the preparation of this reaction mixture, the substances in the reaction mixture can be thoroughly mixed, and the lithium salt dissociates into free lithium ions through intermolecular forces. Subsequently, after injection into a separator, microwave treatment is used to initiate precursor polymerization. Microwave polymerization ensures uniform initiation of the initiator internally, avoiding uneven initiation that could lead to explosive polymerization or incomplete polymerization, thereby effectively reducing the problem of excessively wide polymer molecular weight distribution. After microwave treatment, heat treatment is performed, which further promotes in-situ polymerization, improves polymerization uniformity, and further reduces monomer residue. When applied to the subsequent preparation of solid-state lithium metal batteries, transferring the electrolyte to the inside of the battery for heat treatment after microwave treatment ensures close contact between the formed elastomeric solid polymer electrolyte and the electrode. This avoids the reaction of residual acrylate monomers with the electrode material, which could degrade battery cycle stability; and it improves the smoothness of the elastomeric solid polymer electrolyte surface, facilitating good interfacial contact with the electrode and further improving battery cycle stability.

[0011] Therefore, by using the preparation method of the present invention, the elastomer solid polymer electrolyte can exhibit a longer cycle life when applied to lithium metal batteries.

[0012] In some embodiments, the settling time is 1 to 2 hours.

[0013] In some embodiments, the heat treatment temperature is 60–80°C and the time is 15–1500 min.

[0014] In some embodiments, the heat treatment temperature is 65–75°C and the time is 850–950 min.

[0015] In some embodiments, the microwave processing power is 150–500W; the frequency is 915±50MHz or 2450±50MHz; the time is 10–700s; and the pulse duty cycle is 20–40%.

[0016] In some embodiments, the microwave processing power is 400–450W; the frequency is 915±50MHz; the time is 280–320s; and the pulse duty cycle is 30%.

[0017] The pulse duty cycle of 30% is defined as follows: if the pulse period is 10 milliseconds and the high level lasts for 3 milliseconds, then the pulse duty cycle is 30%.

[0018] In some embodiments, the reaction mixture further includes a plasticizer. Introducing a plasticizer can alter the solvation structure of lithium ions, increasing their migration rate in the elastomeric solid polymer electrolyte, which is beneficial for achieving high-energy-density fast-charging lithium metal batteries.

[0019] In some embodiments, the method for preparing the reaction mixture includes:

[0020] The acrylate monomers were mixed with a portion of the lithium salt to obtain precursor solution A;

[0021] The plasticizer is mixed with the remaining portion of the lithium salt to obtain precursor solution B;

[0022] Precursor solution A and precursor solution B are mixed to obtain monomer prepolymer solution;

[0023] An initiator and a crosslinking agent are added to the monomer prepolymer solution to obtain a reaction mixture.

[0024] By adopting this sequence to form a reaction mixture of raw materials, the raw materials can be fully and uniformly mixed. After the reaction, a highly dense elastomeric solid polymer electrolyte with uniformly distributed components can be formed, which is beneficial to improving the ionic conductivity and mechanical properties of the elastomeric solid polymer electrolyte.

[0025] In some embodiments, the molar ratio of acrylate monomers to a portion of the lithium salt in precursor solution A is 10:(0.5-10).

[0026] In some embodiments, in precursor solution B, the molar ratio of plasticizer to the remaining lithium salt is 10:(0.5-5).

[0027] In some embodiments, the volume ratio of precursor solution A to precursor solution B is 10:(1 to 100).

[0028] In some embodiments, R2 is C1-C 18 Alkyl groups or C2-C groups substituted with 1-3 C1-C4 alkoxy groups 12 alkyl.

[0029] In some embodiments, R2 is selected from -CH2CH2OCH3, -CH2CH2OCH2CH3, -(CH2)3OCH3 or -(CH2)2O(CH2)2OCH3.

[0030] In some embodiments, the acrylate monomers include 2-methoxyethyl acrylate (CAS 3121-61-7) and / or 2-(2-methoxyethoxy)ethyl methacrylate (CAS 45103-59-1).

[0031] In some embodiments, the lithium salt includes at least one selected from lithium bis(trifluoromethanesulfonyl)imide, lithium trifluorosulfonylimide, lithium difluorooxalateborate, lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium perchlorate. It is understood that the lithium salts in precursor solution A and precursor solution B may be the same or different.

[0032] Lithium salts such as lithium bis(trifluoromethanesulfonyl)imide, lithium trifluorosulfonylimide, lithium difluorooxalateborate, lithium hexafluorophosphate, and lithium tetrafluoroborate contain fluorine. During battery operation, they can generate a solid electrolyte interface layer containing LiF in situ on the lithium metal surface, which is beneficial for protecting lithium metal, inducing uniform deposition of lithium ions, and inhibiting the formation of lithium dendrites.

[0033] In some embodiments, the plasticizer includes at least one of nitrile plasticizers, ester plasticizers, and ether plasticizers. Nitrile plasticizers include at least one of succinic anionyl nitrile and adiponitrile; ester plasticizers include at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, and diethyl carbonate; ether plasticizers include at least one of ethylene glycol dimethyl ether and 1,3-dioxolane.

[0034] In some embodiments, the initiator includes at least one selected from peroxide initiators and azo initiators. Peroxide initiators include at least one selected from benzoyl peroxide and lauroyl peroxide; azo initiators include at least one selected from azobisisobutyronitrile, azobisisoheptanenitrile, and azobiscyclohexylformitrile. The mass of the initiator is 0.1–2 wt% of the methacrylate monomer.

[0035] In some embodiments, the crosslinking agent includes at least one selected from polyethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, N,N'-methylenebisacrylamide, and acrylic anhydride. The mass of the crosslinking agent is 0.1 to 3 wt% of the methacrylate monomer.

[0036] In some embodiments, the porous polymer membrane includes at least one of polyethylene membrane, polypropylene membrane, polytetrafluoroethylene membrane, polyimide membrane, polyisophthalamide membrane, polyvinylidene fluoride membrane, cellulose nanofibers, and functionalized composite or modified membranes thereof.

[0037] In some embodiments, the membrane thickness is 5–200 μm and the porosity is 20–90%.

[0038] In some embodiments, the membrane has a thickness of 15 μm and a porosity of 50%.

[0039] In a second aspect, the present invention provides an elastomeric solid polymer electrolyte, which is prepared by the preparation method described in the first aspect above.

[0040] The elastomeric solid polymer electrolyte of the present invention has high ionic conductivity and a smooth surface, providing excellent interfacial contact performance with the electrode.

[0041] In some embodiments, the elastomeric solid polymer electrolyte comprises polyacrylate (plastic phase), plasticizer, lithium salt, and a separator, wherein the polyacrylate, plasticizer, and lithium salt are compounded by intermolecular forces. According to the preparation method of the present invention, acrylate monomers are polymerized to form polyacrylate, which simultaneously interacts with the plasticizer and lithium salt to form an elastomeric solid polymer electrolyte comprising polyacrylate, plasticizer, and lithium salt. The separator provides physical support for the elastomeric electrolyte, facilitating the transfer of the prepolymerized electrolyte membrane during the process.

[0042] In some embodiments, the mass fractions of polyacrylate, plasticizer, and lithium salt in the elastomeric solid polymer electrolyte are 20%–60%, 20%–60%, and 10%–40%, respectively.

[0043] In some embodiments, the diaphragm is a polyethylene diaphragm with a porosity of 50% and a thickness of 15 μm.

[0044] Thirdly, the present invention provides a solid-state lithium metal battery comprising the above-mentioned elastomeric solid polymer electrolyte.

[0045] This solid-state lithium metal battery includes a positive electrode and a negative electrode. The positive electrode includes a positive electrode material, which includes any one or any combination of the following: LiFePO4, LiCoO2, LiMn 0.8 Fe 0.2 PO4, lithium manganese oxide, polyanionic cathode materials, ternary cathode materials, and sulfur and metal sulfide cathode materials. The anode includes anode materials, which include one or any combination of Li metal, LiSi alloy, and LiIn alloy.

[0046] When the elastomeric solid polymer electrolyte of the present invention is used in a solid lithium metal battery, the solid lithium metal battery can exhibit excellent cycle stability.

[0047] Fourthly, the present invention provides a method for preparing a solid-state lithium metal battery, comprising: injecting a reaction mixture containing acrylate monomers, lithium salts, initiators and crosslinking agents into a separator, allowing it to stand for 1 to 2 hours, then subjecting it to microwave treatment, and subsequently transferring the prepolymerized electrolyte membrane into a battery casing for heat treatment.

[0048] Understandably, the positive and negative electrodes are placed inside the battery case before the prepolymerized electrolyte membrane is transferred into the battery case.

[0049] The composition, microwave treatment, and heat treatment of the reaction mixture are the same as those of the preparation method of the first aspect of the elastomeric solid polymer electrolyte.

[0050] The reaction mixture can be polymerized in situ within the battery casing to form an elastomeric solid polymer electrolyte, which, when combined with the positive and negative electrodes, forms a solid-state lithium metal battery.

[0051] Compared with the prior art, the advantages of the present invention are:

[0052] This invention achieves a breakthrough by pioneering a "microwave pre-initiation-in-situ polymerization of elastomers" technical route: at the molecular design level, it utilizes acrylate monomers (general formula CH...) 2＝ The C(R1)C(O)OR2) structure constructs flexible side chains, endowing the polymer with high free volume. Structurally, a plasticizer is innovatively introduced to form a deep eutectic complex with lithium salt, simultaneously improving ionic conductivity and antioxidant voltage. Mechanical properties are enhanced by utilizing a membrane framework (such as PE, PP, PI). In terms of processing, microwave selective pre-initiation (e.g., 2.45GHz pulse-activated AIBN) generates a prepolymer (conversion rate 10-30%) within the framework pores, ensuring the fluidity of the liquid precursor for tight electrode / film adhesion. Thermal polymerization then forms a rigid-flexible interpenetrating network, resulting in a strong interfacial bond. This breakthrough achieves a room-temperature ionic conductivity >10. -4 With a capacity retention rate of 91% after 400 cycles at 4.0V and a speed of S / cm, this technology lays the foundation for the industrialization of solid-state lithium metal batteries. Attached Figure Description

[0053] Figure 1 This is a scanning electron microscope image of the elastomeric solid polymer electrolyte in Example 1;

[0054] Figure 2 This is a graph showing the ionic conductivity of the elastomeric solid polymer electrolyte in Example 1 at different temperatures.

[0055] Figure 3 The overpotential curve of the symmetrical lithium metal battery of Example 1 is shown in the figure at 30°C.

[0056] Figure 4 The cycling curve of the LFP lithium battery in Comparative Example 1 at 30°C is shown.

[0057] Figure 5 This is a cycle curve of the LFP battery in Example 1 at 30°C;

[0058] Figure 6 The Fourier transform infrared spectra of the elastomeric solid polymer electrolytes prepared in Example 1 and Comparative Example 1 are shown. Detailed Implementation

[0059] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0060] Unless otherwise specified, the reagents, methods, and equipment used in this invention are all conventional reagents, methods, and equipment in this technical field, which can be obtained commercially or prepared using known methods.

[0061] Example 1

[0062] This embodiment provides an elastomeric solid polymer electrolyte and a solid metal lithium battery; the preparation method of the elastomeric solid polymer electrolyte includes the following steps:

[0063] (a) Methyl methacrylate monomer and LiTFSI (lithium trifluoromethanesulfonylimide) were mixed in a molar ratio of 10:1 to obtain precursor solution A;

[0064] (b) Mix succinate and LiTFSI in a molar ratio of 10:1 to obtain precursor solution B;

[0065] (c) Mix precursor solution A and precursor solution B at a volume ratio of 4:6 to obtain monomer prepolymer solution;

[0066] (d) Add 0.5 wt% azobisisobutyronitrile initiator and 0.5 wt% polyethylene glycol dimethacrylate crosslinking agent to the monomer prepolymer solution, stir evenly, and then inject into a diaphragm (polyethylene diaphragm, thickness 15 μm, porosity 50%), and let stand for 1.5 h. Then, microwave prepolymerize (power 450 W, frequency 915 MHz, time 300 s, pulse duty cycle 30%) to obtain a prepolymerized electrolyte membrane, and then heat treat the prepolymerized electrolyte membrane (held at 70 °C for 900 min) to obtain an elastomeric solid polymer electrolyte.

[0067] The preparation method of the solid-state lithium metal battery is the same as steps (a) to (c) of the elastomeric solid polymer electrolyte. Step (d) is as follows: 0.5 wt% of azobisisobutyronitrile initiator and 0.5 wt% of polyethylene glycol dimethacrylate crosslinking agent are added to the monomer prepolymer solution at a weight ratio relative to the methacrylate monomer. After stirring evenly, the mixture is injected into a separator (polyethylene separator, thickness 15 μm, porosity 50%) and allowed to stand for 1.5 h. Then, the mixture is prepolymerized by microwave treatment (power 450 W, frequency 915 MHz, time 300 s, pulse duty cycle 30%) to obtain a prepolymerized electrolyte membrane. Subsequently, the prepolymerized electrolyte membrane is transferred to the battery interior (the battery interior components are LFP positive electrode (lithium iron phosphate positive electrode) and lithium metal negative electrode) and subjected to heat treatment (held at 70 °C for 900 min) to obtain a solid-state lithium metal battery containing an elastomeric solid polymer electrolyte.

[0068] Example 2

[0069] This embodiment provides an elastomeric solid polymer electrolyte and a solid metal lithium battery; the preparation method of the elastomeric solid polymer electrolyte includes the following steps:

[0070] (a) Methyl methacrylate monomer and LiTFSI were mixed in a molar ratio of 10:0.5 to obtain precursor solution A;

[0071] (b) Mix succinate and LiTFSI in a molar ratio of 10:5 to obtain precursor solution B;

[0072] (c) Mix precursor solution A and precursor solution B at a volume ratio of 4:6 to obtain monomer prepolymer solution;

[0073] (d) Add 0.5 wt% of an azobisisobutyronitrile azo initiator and 0.5 wt% of polyethylene glycol dimethacrylate crosslinking agent to the monomer prepolymer solution, stir evenly, and then inject into a diaphragm (polyethylene diaphragm, thickness 15 μm, porosity 50%) and let stand for 1.5 h. Then, microwave heating (power 450 W, frequency 2450 MHz, time 300 s; pulse duty cycle 30%) is performed on the prepolymer to obtain a prepolymerized electrolyte membrane. Subsequently, the prepolymerized electrolyte membrane is heat-treated (held at 70 °C for 900 min) to obtain an elastomeric solid polymer electrolyte.

[0074] The preparation method of the solid-state lithium metal battery is the same as steps (a) to (c) of the elastomeric solid polymer electrolyte. Step (d) is as follows: 0.5 wt% of an azobisisobutyronitrile initiator and 0.5 wt% of polyethylene glycol dimethacrylate crosslinking agent are added to the monomer prepolymer solution at a weight ratio relative to the methacrylate monomer. After stirring evenly, the mixture is injected into a separator (polyethylene separator, thickness 15 μm, porosity 50%) and allowed to stand for 1.5 h. Then, the mixture is prepolymerized by microwave treatment (power 450 W, frequency 2450 MHz, time 300 s, pulse duty cycle 30%) to obtain a prepolymerized electrolyte membrane. Subsequently, the prepolymerized electrolyte membrane is transferred to the battery interior (the battery interior components are LFP positive electrode and lithium metal negative electrode) and subjected to heat treatment (held at 70 °C for 900 min) to obtain a solid-state lithium metal battery containing an elastomeric solid polymer electrolyte.

[0075] Example 3

[0076] This embodiment provides an elastomeric solid polymer electrolyte and a solid metal lithium battery; the preparation method of the elastomeric solid polymer electrolyte includes the following steps:

[0077] (a) Mix ethyl methacrylate monomer and LiTFSI in a molar ratio of 1:1 to obtain precursor solution A;

[0078] (b) Mix succinate and LiTFSI in a molar ratio of 10:0.5 to obtain precursor solution B;

[0079] (c) Mix precursor solution A and precursor solution B at a volume ratio of 4:6 to obtain monomer prepolymer solution;

[0080] (d) Benzoyl peroxide initiator and N,N'-methylenebisacrylamide crosslinking agent were added to the monomer prepolymer solution at a weight ratio of 0.5 wt% relative to the methacrylate monomer. After stirring evenly, the mixture was injected into a diaphragm (polyethylene diaphragm, thickness 15 μm, porosity 50%) and allowed to stand for 1.5 h. Then, the prepolymer was treated with microwave heating (power 450 W, frequency 2450 MHz, time 300 s, pulse duty cycle 30%) to obtain a prepolymerized electrolyte membrane. Subsequently, the prepolymerized electrolyte membrane was heat-treated (held at 70 °C for 900 min) to obtain an elastomeric solid polymer electrolyte.

[0081] The preparation method of the solid-state lithium metal battery is the same as steps (a) to (c) of the elastomeric solid polymer electrolyte. Step (d) is as follows: Benzoyl peroxide initiator and N,N'-methylenebisacrylamide crosslinking agent at a weight ratio of 0.5 wt% to methacrylate monomer are added to the monomer prepolymer solution. After stirring evenly, the mixture is injected into a separator (polyethylene separator, thickness 15 μm, porosity 50%) and allowed to stand for 1.5 h. Then, prepolymerization is carried out by microwave heating (power 450 W, frequency 2450 MHz, time 300 s, pulse duty cycle 30%) to obtain a prepolymerized electrolyte membrane. Subsequently, the prepolymerized electrolyte membrane is transferred to the battery interior (the components inside the battery are LFP positive electrode and lithium metal negative electrode) for heat treatment (held at 70 °C for 900 min) to obtain a solid-state lithium metal battery containing an elastomeric solid polymer electrolyte.

[0082] Example 4

[0083] This embodiment provides an elastomeric solid polymer electrolyte and a solid metal lithium battery; the preparation method of the elastomeric solid polymer electrolyte includes the following steps:

[0084] (a) Mix methacrylate monomer and LiTFSI in a molar ratio of 10:1 to obtain precursor solution A;

[0085] (b) Mix succinate and LiTFSI in a molar ratio of 10:1 to obtain precursor solution B;

[0086] (c) Mix precursor solution A and precursor solution B at a volume ratio of 3:7 to obtain monomer prepolymer solution;

[0087] (d) Benzoyl peroxide initiator and N,N'-methylenebisacrylamide crosslinking agent were added to the monomer prepolymer solution at a weight ratio of 0.5 wt% relative to the methacrylate monomer. After stirring evenly, the mixture was injected into a diaphragm (polyethylene diaphragm, thickness 15 μm, porosity 50%) and allowed to stand for 1.5 h. Then, the prepolymer was treated with microwave heating (power 450 W, frequency 2450 MHz, time 300 s, pulse duty cycle 30%) to obtain a prepolymerized electrolyte membrane. Subsequently, the prepolymerized electrolyte membrane was heat-treated (held at 70 °C for 900 min) to obtain an elastomeric solid polymer electrolyte.

[0088] The preparation method of the solid-state lithium metal battery is the same as steps (a) to (c) of the elastomeric solid polymer electrolyte. Step (d) is as follows: Benzoyl peroxide initiator and N,N'-methylenebisacrylamide crosslinking agent at a weight ratio of 0.5 wt% relative to the methacrylate monomer are added to the monomer prepolymer solution. After stirring evenly, the mixture is injected into a porous polyethylene membrane (polyethylene membrane, thickness 15 μm, porosity 50%) and allowed to stand for 1.5 h. Then, prepolymerization is carried out by microwave heating (power 450 W, frequency 2450 MHz, time 300 s, pulse duty cycle 30%) to obtain a prepolymerized electrolyte membrane. Subsequently, the prepolymerized electrolyte membrane is transferred to the battery interior (the components inside the battery are the LFP positive electrode and the lithium metal negative electrode) for heat treatment (held at 70 °C for 900 min) to obtain a solid-state lithium metal battery containing an elastomeric solid polymer electrolyte.

[0089] Example 5

[0090] This embodiment provides an elastomeric solid polymer electrolyte and a solid metal lithium battery; the preparation method of the elastomeric solid polymer electrolyte includes the following steps:

[0091] (a) Mix methacrylate monomer and LiTFSI in a molar ratio of 10:1 to obtain precursor solution A;

[0092] (b) Mix succinate and LiFSI (lithium bisfluorosulfonyl imide) in a molar ratio of 10:1 to obtain precursor solution B;

[0093] (c) Mix precursor solution A and precursor solution B at a volume ratio of 2:8 to obtain monomer prepolymer solution;

[0094] (d) Benzoyl peroxide initiator and N,N'-methylenebisacrylamide crosslinking agent were added to the monomer prepolymer solution at a weight ratio of 0.5 wt% relative to the methacrylate monomer. After stirring evenly, the mixture was injected into a membrane (polyethylene membrane, thickness 15 μm, porosity 50%) and allowed to stand for 1.5 h. Then, microwave heating (power 450 W, frequency 2450 MHz, time 300 s, pulse duty cycle 30%) was performed to prepolymerize and obtain a prepolymerized electrolyte membrane. Subsequently, the prepolymerized electrolyte membrane was heat-treated (held at 70 °C for 900 min) to obtain an elastomeric solid polymer electrolyte.

[0095] The preparation method of the solid-state lithium metal battery is the same as steps (a) to (c) of the elastomeric solid polymer electrolyte. Step (d) is as follows: Benzoyl peroxide initiator and N,N'-methylenebisacrylamide crosslinking agent at a weight ratio of 0.5 wt% to methacrylate monomer are added to the monomer prepolymer solution. After stirring evenly, the mixture is injected into a separator (polyethylene separator, thickness 15 μm, porosity 50%) and allowed to stand for 1.5 h. Then, prepolymerization is carried out by microwave heating (power 450 W, frequency 2450 MHz, time 300 s, pulse duty cycle 30%) to obtain a prepolymerized electrolyte membrane. Subsequently, the prepolymerized electrolyte membrane is transferred to the battery interior (the components inside the battery are LFP positive electrode and lithium metal negative electrode) for heat treatment (held at 70 °C for 900 min) to obtain a solid-state lithium metal battery containing an elastomeric solid polymer electrolyte.

[0096] Example 6

[0097] This embodiment provides an elastomeric solid polymer electrolyte and a solid metal lithium battery; the preparation method of the elastomeric solid polymer electrolyte includes the following steps:

[0098] Methyl methacrylate monomer and LiDFOB (lithium difluorooxalate borate) were mixed at a molar ratio of 10:1, and then an initiator and a crosslinking agent were added. The initiator was azobisisobutyronitrile (AIB), with a mass of 0.5 wt% of the methyl methacrylate monomer; the crosslinking agent was polyethylene glycol dimethacrylate, with a mass of 0.5 wt% of the methyl methacrylate monomer. After thorough mixing, the mixture was injected into a diaphragm (polyethylene diaphragm, 15 μm thick, 50% porosity) and allowed to stand for 1.5 h. Then, microwave heating (450 W power, 2450 MHz frequency, 300 s time, 30% pulse duty cycle) was used for prepolymerization to obtain a prepolymerized electrolyte membrane. Subsequently, the prepolymerized electrolyte membrane was heat-treated (held at 70 °C for 900 min) to obtain an elastomeric solid polymer electrolyte.

[0099] The solid-state lithium metal battery is prepared as follows: methyl methacrylate monomer and LiDFOB (lithium difluorooxalate borate) are mixed at a molar ratio of 10:1, and then an initiator and a crosslinking agent are added. The initiator is azobisisobutyronitrile (AIB), with a mass of 0.5 wt% of the methyl methacrylate monomer; the crosslinking agent is polyethylene glycol dimethacrylate, with a mass of 0.5 wt% of the methyl methacrylate monomer. After thorough stirring, the mixture is injected into a separator (polyethylene separator, 15 μm thick, 50% porosity) and allowed to stand for 1.5 h. Then, microwave heating (450 W power, 2450 MHz frequency, 300 s time, 30% pulse duty cycle) is performed to prepolymerize a prepolymerized electrolyte membrane. The prepolymerized electrolyte membrane is then transferred to the battery interior (where the internal components are the LFP positive electrode and the lithium metal negative electrode) for heat treatment (held at 70 °C for 900 min) to obtain a solid-state lithium metal battery containing an elastomeric solid polymer electrolyte.

[0100] Example 7

[0101] This embodiment provides an elastomeric solid polymer electrolyte and a solid metal lithium battery; the difference between the preparation method of the elastomeric solid polymer electrolyte and that of Embodiment 1 is that the heat treatment time in step (d) is adjusted to 1500 min.

[0102] Example 8

[0103] This embodiment provides an elastomeric solid polymer electrolyte and a solid metal lithium battery; the difference between the preparation method of the elastomeric solid polymer electrolyte and that of Embodiment 1 is that the heat treatment temperature in step (d) is adjusted to 80°C.

[0104] Example 9

[0105] This embodiment provides an elastomeric solid polymer electrolyte and a solid metal lithium battery; the difference between the preparation method of the elastomeric solid polymer electrolyte and that of Embodiment 1 is that the microwave heating power in step (d) is adjusted to 500W.

[0106] Example 10

[0107] This embodiment provides an elastomeric solid polymer electrolyte and a solid metal lithium battery; the difference between the preparation method of the elastomeric solid polymer electrolyte and that of Embodiment 1 is that the microwave heating frequency in step (d) is 2450MHz.

[0108] Comparative Example 1

[0109] This comparative example provides an elastomeric solid polymer electrolyte and a solid metal lithium battery; the difference between the preparation method of the elastomeric solid polymer electrolyte and Example 1 is that the microwave heating step is not performed in step (d).

[0110] Comparative Example 2

[0111] This comparative example provides an elastomeric solid polymer electrolyte and a solid metal lithium battery; the difference between the preparation method of the elastomeric solid polymer electrolyte and Example 1 is that, in step (d), the microwave heating step is not performed, and the heat treatment time is extended to 1500 min.

[0112] Comparative Example 3

[0113] This comparative example provides an elastomeric solid polymer electrolyte and a solid metal lithium battery. The difference between the preparation method of the elastomeric solid polymer electrolyte and that of Example 1 is that, in step (d), the microwave heating step is not performed, and the heat treatment temperature is increased to 80°C.

[0114] Comparative Example 4

[0115] This comparative example provides an elastomeric solid polymer electrolyte and a solid metal lithium battery; the difference between the preparation method of the elastomeric solid polymer electrolyte and Example 1 is that, in step (d), no heat treatment step is performed.

[0116] Physical and electrochemical tests were performed on elastomer solid polymer electrolytes or solid lithium metal batteries, and the results are as follows:

[0117] (1) Scanning electron microscope image of the elastomeric solid polymer electrolyte prepared in Example 1 is shown below. Figure 1 As shown. By Figure 1 It can be seen that the surface of the solid polymer elastomer electrolyte is flat and smooth, with no microphase separation. The flat surface is conducive to forming a good interfacial contact with the electrode.

[0118] (2) The ionic conductivity of different elastomeric solid polymer electrolytes at different temperatures was tested. A stainless steel symmetrical battery was assembled, with a stainless steel sheet replacing the LFP cathode and lithium metal, separated by a 15μm porous polyethylene membrane (steel sheet | elastomeric solid polymer electrolyte | steel sheet, calculation formula: σ=L / RS, where L represents the thickness of the elastomeric solid polymer electrolyte, R represents the volume impedance of the elastomeric solid polymer electrolyte, and S represents the contact area). The ionic conductivity was tested using a Shanghai Chenhua electrochemical workstation, and the results are as follows: Figure 2 As shown. By Figure 2 It can be concluded that, at 30°C, the ionic conductivity of the elastomeric solid polymer electrolyte of Example 1 is 0.497 mS·cm. -1 The ionic conductivity of the elastomeric solid polymer electrolytes of Examples 2-10 and Comparative Examples 1-4 is shown in Table 1.

[0119] Table 1

[0120]

[0121] As can be seen from Table 1, when the further selection of the standing and microwave treatment times is within the range given in this invention, the obtained elastomeric solid polymer electrolyte exhibits a high ionic conductivity, reaching 0.295 mS·cm. -1 In summary, when no microwave or heat treatment is performed, the ionic conductivity of the resulting elastomeric solid polymer electrolyte decreases significantly.

[0122] (3) Cyclic performance tests were conducted on different solid lithium metal batteries. Specifically, the batteries were charged and discharged at 30°C and 0.5C rate. Specifically, the Wuhan Landian Battery Testing System was used for constant current charge and discharge, and the capacity retention rate was recorded after 200 cycles. The results are shown in Table 2.

[0123] Table 2

[0124]

[0125]

[0126] As can be seen from Table 2, when the technical solution provided by the present invention is adopted, the obtained solid-state lithium metal battery has good cycle performance, and the capacity retention rate is more than 65% after 200 cycles.

[0127] Meanwhile, constant current charge-discharge tests were performed on the battery prepared in Example 1. Using the elastomeric solid polymer electrolyte prepared in Example 1 as raw material, a symmetrical lithium metal half-cell (Li|elastomeric solid polymer electrolyte|Li symmetrical cell, constant current charge-discharge performed using the Wuhan Landian Battery Testing System) was assembled and the results of the constant current charge-discharge tests are as follows: Figure 3 As shown, Figure 3 This is the overpotential curve of the symmetrical lithium metal battery containing an elastomeric solid polymer electrolyte in Example 1, cycled at 30°C. Figure 3 It can be seen that the symmetrical lithium metal battery with elastomeric solid polymer electrolyte assembled in Example 1 can be stably cycled for more than 300 hours at 30°C and has very stable overpotential.

[0128] Figure 4 The graph shows the cycle curves of the solid metal lithium battery in Comparative Example 1 at the same current and 0.5C charge-discharge rate. Figure 5 This is a cycle curve of the solid metal lithium battery in Example 1 at the same current and 0.5C charge / discharge rate; from Figure 4-5It can be seen that Comparative Example 1, without microwave treatment during the polymerization of the elastomeric solid polymer electrolyte, exhibited a shorter cycle life for its all-solid-state lithium metal battery; while Example 1, employing microwave and heat treatment, enabled its all-solid-state lithium metal battery to demonstrate excellent cycle stability. Further Fourier transform infrared spectroscopy analysis was performed on the elastomeric solid polymer electrolytes prepared in Example 1 (microwave treated) and Comparative Example 1 (without microwave treatment), as shown... Figure 6 As shown, from Figure 6 As can be seen, microwave treatment and electrolyte polymerization are more complete, and residual monomers are significantly reduced.

[0129] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing an elastomeric solid polymer electrolyte, characterized in that, Includes the following steps: A reaction mixture comprising acrylate monomers, lithium salts, initiators and crosslinking agents is provided. The reaction mixture is injected into a diaphragm and allowed to stand, followed by microwave treatment and heat treatment in sequence. The acrylate monomer has the structural formula CH2=C(R1)C(O)O-R2, where R1 is hydrogen or methyl, and R2 is alkyl or substituted alkyl. The general structural formula of the acrylate monomer is shown in structural formula I.

2. The method for preparing the elastomeric solid polymer electrolyte according to claim 1, characterized in that, The settling time is 1 to 2 hours; And / or, the power of the microwave processing is 150–500W; the frequency is 915±50MHz or 2450±50MHz; the pulse duty cycle is 20–40%; and the time is 10–700s. And / or, the heat treatment temperature is 60-80°C and the time is 15-1500 min.

3. The method for preparing the elastomeric solid polymer electrolyte according to claim 1 or 2, characterized in that, The reaction mixture also includes a plasticizer.

4. The method for preparing the elastomeric solid polymer electrolyte according to claim 3, characterized in that, The preparation method of the reaction mixture includes: The acrylate monomer is mixed with a portion of the lithium salt to obtain precursor solution A; The plasticizer is mixed with the remaining lithium salt to obtain precursor solution B; The precursor solution A and the precursor solution B are mixed to obtain a monomer prepolymer solution; The initiator and the crosslinking agent are added to the monomer prepolymer solution to obtain the reaction mixture.

5. The method for preparing the elastomeric solid polymer electrolyte according to claim 4, characterized in that, In the precursor solution A, the molar ratio of the acrylate monomer to a portion of the lithium salt is 10:(0.5-10); And / or, in the precursor solution B, the molar ratio of the plasticizer to the remaining lithium salt is 10:(0.5-5).

6. The method for preparing the elastomeric solid polymer electrolyte according to claim 4, characterized in that, The volume ratio of precursor solution A to precursor solution B is 10:(1-100).

7. The method for preparing the elastomeric solid polymer electrolyte according to claim 5 or 6, characterized in that, R2 is C1-C 18 Alkyl groups or C2-C groups substituted with 1-3 C1-C4 alkoxy groups 12 alkyl; And / or, the lithium salt includes at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium trifluorosulfonylimide, lithium difluorooxalateborate, lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium perchlorate; And / or, the plasticizer includes at least one of nitrile plasticizers, ester plasticizers, and ether plasticizers; And / or, the membrane includes at least one of polyethylene membrane, polypropylene membrane, polytetrafluoroethylene membrane, polyimide membrane, polyisophthalamide membrane, polyvinylidene fluoride membrane, cellulose nanofibers and their functionalized composite or modified membranes. And / or, the thickness of the diaphragm is 5–200 μm, and the porosity is 20–90%.

8. An elastomeric solid polymer electrolyte, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 7.

9. A solid-state lithium metal battery, characterized in that, Includes the elastomeric solid polymer electrolyte of claim 8.

10. A method for preparing a solid-state lithium metal battery according to claim 9, characterized in that, include: The reaction mixture comprising the acrylate monomer, the lithium salt, the initiator, and the crosslinking agent is injected into the separator and allowed to stand, followed by microwave treatment, and then transferred into the battery casing for heat treatment.

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