A thermosetting polymer-based structural electrolyte, a method for preparing the same and a lithium-ion structural battery

Abstract

This invention belongs to the field of battery material technology, specifically a method for preparing a thermosetting polymer-based electrolyte, comprising: mixing a mechanically supporting phase precursor and an ion-conducting phase precursor, followed by in-situ crosslinking and curing to form a bicontinuous phase structure composed of an elastomeric phase and a crystalline phase, thereby obtaining the thermosetting polymer-based electrolyte; the mechanically supporting phase precursor includes acrylate monomers, a multifunctional crosslinking agent, a hydrogen bond-enhancing monomer, a lithium salt, and an initiator; the ion-conducting phase precursor includes a nitrile ion-conducting component, a lithium salt, and an interface-stabilizing additive; the acrylate monomer is a monomer containing only one acrylate group, and the multifunctional crosslinking agent is a crosslinking agent containing at least two acrylate groups. The electrolyte obtained by this invention possesses high mechanical strength, high ionic conductivity, high lithium-ion transport number, and flame-retardant safety, and can be used in structural batteries and other energy storage devices that require simultaneous ion conduction and structural support.

Description

Technical Field

[0001] This invention belongs to the field of battery materials technology, specifically relating to a thermosetting polymer-based electrolyte, its preparation method, and a lithium-ion battery. Background Technology

[0002] Lithium-ion batteries, due to their high energy density and long cycle life, are widely used in portable electronic devices, electric vehicles, drones, and aerospace equipment. With the increasing demand for lightweight and integrated equipment, the traditional separate design of "battery pack + load-bearing structure" is gradually revealing problems such as low system mass utilization, structural redundancy, and large space occupation. Structural batteries, by integrating energy storage units with load-bearing components, allow some structural components to simultaneously undertake energy storage and load-bearing tasks, thereby improving system-level mass efficiency.

[0003] In structured batteries, the structural electrolyte is a key material connecting electrochemical and structural functions. It needs to provide a continuous and stable lithium-ion transport channel between the positive and negative electrodes, and also serve as a matrix material for load transfer and interfacial support. Existing structural electrolytes typically employ polymer solid-state electrolytes, gel electrolytes, or thermosetting resin-based electrolytes. While thermoplastic polymer electrolytes are easy to process, their mechanical strength and thermal stability are limited; traditional thermosetting resins have high crosslinking density and good mechanical support capabilities, but their small free volume restricts polymer chain movement, resulting in significant resistance to lithium-ion migration within the polymer phase.

[0004] To improve ion conductivity, existing technologies propose introducing ionic liquids or organic liquid electrolytes into thermosetting resins. This involves constructing a phase-separated structure through reaction-induced phase separation, where the resin phase primarily provides mechanical support, while the liquid-rich phase provides ion conduction. However, ionic liquid systems typically have high viscosity and low lithium-ion transference numbers, making them prone to concentration polarization at the electrode / electrolyte interface. Structured electrolytes containing large amounts of organic liquid electrolytes may also pose risks of volatilization, leakage, and flammability.

[0005] Therefore, achieving high ionic conductivity, high lithium-ion transference number, a supportable thermosetting network, and good interfacial safety simultaneously within the same electrolyte system remains a core challenge in structural battery material design. This is particularly true for carbon fiber structure batteries, where the electrolyte must not only be fully wetted by the carbon fiber-supported positive electrode, carbon fiber negative electrode, and separator, but also maintain a continuous internal ionic pathway after curing, while avoiding disruption of the support network's continuity due to excessive introduction of conductive phase.

[0006] Therefore, it is necessary to develop a new thermosetting polymer-based electrolyte to solve the above problems. Summary of the Invention

[0007] The purpose of this invention is to provide a thermosetting polymer-based electrolyte, its preparation method, and a lithium-ion battery. By forming a dual continuous phase structure consisting of an elastomeric phase and a crystalline phase, the coupling between lithium ions and the polymer support phase is reduced, thereby achieving a synergistic improvement in mechanical and electrochemical performance.

[0008] To achieve the above objectives, the present invention provides a method for preparing a thermosetting polymer-based electrolyte, comprising: mixing a mechanically supporting phase precursor and an ion-conducting phase precursor and then crosslinking and curing them in situ; and forming a bicontinuous phase structure consisting of an elastomer phase and a plastic crystal phase through polymerization-induced phase separation, thereby obtaining the thermosetting polymer-based electrolyte. The mechanically supported phase precursor includes acrylate monomers, multifunctional crosslinking agents, hydrogen bond-enhancing monomers, lithium salts, and initiators; the ion-conducting phase precursor includes nitrile ion-conducting components, lithium salts, and interface-stabilizing additives. The acrylate monomer is a monomer that includes only one acrylate group, and the multifunctional crosslinker is a crosslinker that includes at least two acrylate groups.

[0009] Furthermore, the multifunctional crosslinking agent includes one or more of trimethylolpropane triacrylate, polyethylene glycol diacrylate, diethylene glycol diacrylate, and pentaerythritol triacrylate; preferably trimethylolpropane triacrylate.

[0010] Furthermore, the acrylate monomers include one or more of butyl acrylate, butyl methacrylate, ethyl acrylate, methyl acrylate, and polyethylene glycol methyl ether acrylate; preferably, they include butyl acrylate.

[0011] Furthermore, the hydrogen bond reinforcing monomer includes one or more of acrylamide, methacrylamide, N-hydroxymethylacrylamide, and N-vinylpyrrolidone, preferably methacrylamide, and the hydrogen bond reinforcing monomer forms a hydrogen bond network in the cured mechanical support phase through amide groups.

[0012] Furthermore, the nitrile ion-conducting component includes one or more of succinic acid, adiponitrile, glutaronitrile, and ethylenedionitrile; preferably succinic acid, and the ion-conducting phase is a succinic acid-rich ion-conducting phase.

[0013] The lithium salt includes one or more of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, and lithium difluorooxalate borate, preferably lithium bis(fluorosulfonyl)imide. The lithium salt has good solubility in a nitrile-rich conductive phase, can provide a high concentration of migratable lithium ions, and is beneficial to improving the overall ion conductivity of the electrolyte.

[0014] The interface stabilizing additives include one or more of fluoroethylene carbonate, vinylene carbonate, ethylene carbonate, methyl ethyl carbonate, dimethyl carbonate, and diethyl carbonate, preferably fluoroethylene carbonate and vinylene carbonate. These additives can participate in the formation of the electrode interface film, improve the interfacial stability between the structural electrolyte and the carbon fiber-based positive and negative electrodes, and reduce capacity decay caused by side reactions and interfacial impedance growth during cycling.

[0015] Furthermore, the ion-conducting phase precursor accounts for 20% to 90% of the total volume of the mechanical support phase precursor and the ion-conducting phase precursor; preferably 40% to 80%, more preferably 50% to 70%; and even more preferably 60%. When the proportion of the ion-conducting phase is too high, the elastomer phase is significantly diluted, and the electrolyte carrying capacity decreases.

[0016] It should be noted that the formation of the bicontinuous structure of the elastomeric phase and the plastic crystal phase requires the simultaneous presence and appropriate ratio of the BA-based thermosetting crosslinked network and the SN-rich plastic crystal phase: when the SN volume fraction is 0%, the system only forms the BA-TMPTA-MAAm crosslinked polymer phase, lacking SN-rich continuous ion channels; when the SN volume fraction is 100%, the system lacks the BA-based polymerizable support phase and cannot form a thermosetting crosslinked support network; when the SN volume fraction is too low (e.g., 20%~40%), the SN-rich regions are mainly isolated or partially connected; when the SN volume fraction is too high (e.g., 80% and above), the BA-based continuous support network is weakened. At approximately 60% SN volume fraction, both the elastomeric phase and the plastic crystal phase can maintain continuous connectivity, making it easier to form a stable bicontinuous phase structure.

[0017] Furthermore, the acrylate monomer accounts for 40% to 90% of the total mass of the acrylate monomer, the multifunctional crosslinking agent, and the hydrogen bond reinforcing monomer, for example, 60%, 70%, 80%, preferably 70%; the multifunctional crosslinking agent accounts for 5% to 30% of the total mass of the acrylate monomer, the multifunctional crosslinking agent, and the hydrogen bond reinforcing monomer, for example, 10%, 15%, 20%, 25%, preferably 15%.

[0018] The hydrogen bond reinforcing monomer accounts for 5% to 30% of the total mass of the acrylate monomer, the multifunctional crosslinking agent and the hydrogen bond reinforcing monomer; for example, 10%, 15%, 20% and 25%, preferably 15%.

[0019] And / or, the concentration of lithium salt in the mechanically supported phase precursor is 0.5~3.0 mol L⁻¹, preferably 1.0~2.0 mol L⁻¹, more preferably about 1.5 mol L⁻¹.

[0020] Furthermore, the final concentration of lithium salt in the ion-conducting phase precursor is 0.5~3.0 mol L⁻¹, preferably 1.0~2.0 mol L⁻¹, and more preferably about 1.5 mol L⁻¹.

[0021] Furthermore, in the ion-conducting phase precursor, the volume ratio of ethylene carbonate / ethyl methyl carbonate / dimethyl carbonate cosolvent is 1:1:1, and its total amount is 5% to 20% of the volume of the nitrile ion-conducting component, preferably 10%; the amount of fluoroethylene carbonate is 5% to 25% of the volume of the nitrile ion-conducting component, preferably 15%; and the amount of vinylene carbonate is 0.5% to 5% of the volume of the nitrile ion-conducting component, preferably 1%.

[0022] Furthermore, the in-situ crosslinking curing temperature is 50-90℃, and the time is 0.5-8 h, preferably 1-3 h; more preferably, the thermal curing temperature is 60-75℃, and the thermal curing time is 2 h; the preparation process is carried out in an inert atmosphere, wherein the oxygen content and water content in the inert atmosphere are both not higher than 1 ppm, preferably not higher than 0.1 ppm. An inert atmosphere can reduce the inhibition of free radical polymerization by oxygen and reduce the influence of moisture on lithium salts, nitrile components, and electrode interfaces. The inert atmosphere can be argon or nitrogen. Furthermore, the preparation method specifically includes: (1) mixing acrylate monomers, multifunctional crosslinking agents, hydrogen bond reinforcing monomers, lithium salts and thermal initiators uniformly to obtain a mechanically supported phase precursor; (2) The nitrile ion-conducting component, lithium salt and interface stabilizing additive are mixed evenly to obtain an ion-conducting phase precursor; (3) Mix the mechanical support phase precursor and the ion-conducting phase precursor in a predetermined ratio, and inject the mixed precursor liquid into the mold, electrode / separator assembly or battery. (4) The mixture is thermosetting at 50~90℃ for 0.5~8 h to allow free radical polymerization and polymerization-induced phase separation to occur in the mixed precursor liquid, thereby obtaining the thermosetting polymer-based electrolyte.

[0023] Under optimal preparation conditions, the components of the mechanically supported phase precursor are added sequentially and stirred until homogeneous. The succinate and lithium salt in the ion-conducting phase precursor are thoroughly mixed before the interface stabilizing additive is added. The two-phase precursor solution should be used for potting or coating as soon as possible after mixing to ensure that the precursor solution fully wets the electrodes and separator before curing.

[0024] Furthermore, the initiator includes one or more of azobisisobutyronitrile, benzoyl peroxide, and azobisisoheptanenitrile, and the amount of the initiator is 0.1% to 2.0% of the total mass of the acrylate monomer, the multifunctional crosslinking agent, and the hydrogen bond reinforcing monomer.

[0025] The present invention also provides a thermosetting polymer-based electrolyte, which is prepared by any of the preparation methods described above.

[0026] The present invention also provides a lithium-ion structure battery, including a positive electrode, a negative electrode, a separator, and the thermosetting polymer-based structure electrolyte described above, wherein the thermosetting polymer-based structure electrolyte is located between the positive electrode and the negative electrode and forms continuous contact with the positive electrode, the negative electrode, and the separator.

[0027] Furthermore, the positive electrode is a carbon fiber-supported positive electrode containing lithium-ion battery active positive electrode materials (such as lithium nickel cobalt manganese oxide, lithium iron phosphate, lithium cobalt oxide, or lithium manganese oxide), and the negative electrode is a carbon fiber or carbon fiber composite material negative electrode (such as graphite-coated carbon fiber, carbon / carbon composite material). Preferably, the positive electrode is an NCM622 / carbon fiber fabric positive electrode, and the negative electrode is a carbon / carbon composite material self-supporting negative electrode.

[0028] Furthermore, the lithium-ion structural battery also includes a fiber-reinforced resin structural layer located on the outside of the battery; the fiber-reinforced resin structural layer and the thermosetting polymer-based structural electrolyte together form a load transfer structure, enabling the structural battery to simultaneously have the functions of power output and structural support.

[0029] Furthermore, the positive electrode, separator, and negative electrode are stacked and added to a mixed precursor solution composed of the mechanically supporting phase precursor and the ion-conducting phase precursor, so that the mixed precursor solution wets the interface of the positive electrode, separator, and negative electrode; then, in-situ thermal curing is performed to obtain an electrochemical core; then, carbon fiber / resin prepreg is laid on the outside of the electrochemical core, and an integrated structure battery is obtained by vacuum bag pressing and thermal curing.

[0030] The structural layer can be a carbon fiber / epoxy resin layer, a carbon fiber / phenolic resin layer, a glass fiber / epoxy resin layer, or an aramid fiber / resin layer. By combining the electrochemical core with the fiber-reinforced structural layer, the battery can simultaneously perform energy output and structural support functions, making it suitable for lightweight casings, load-bearing plates, drone components, robot shells, and other composite energy storage applications.

[0031] In summary, compared with the prior art, the above-described technical solutions conceived by this invention mainly possess the following technical advantages: 1. The method for preparing thermosetting polymer-based electrolytes provided by this invention no longer simply designs the polymer electrolyte as a single homogeneous network, nor does it rely on a large amount of liquid electrolyte to compensate for the low conductivity of thermosetting polymers. Instead, it uses acrylates with different functionalities and hydrogen-bonding-enhancing monomers as precursors for the mechanically supporting phase, and nitrile ion-conducting components and lithium salts as precursors for the ion-conducting phase. Through polymerization-induced phase separation, a bicontinuous phase structure is constructed in the thermosetting polymer system, so that the elastomeric phase composed of the thermosetting polymer network and the crystalline phase composed of nitrile components and lithium salts form continuous networks respectively. The elastomeric phase undertakes the functions of mechanical load-bearing and interfacial support, while the crystalline phase provides lithium-rich and nitrile-rich nanoscale fast ion transport channels. The two phases are spatially interpenetrating but functionally distinct, alleviating the inherent conflict between mechanical strength and ionic conductivity at the structural level, thus simultaneously possessing good mechanical strength and high ionic conductivity.

[0032] 2. This invention utilizes the strong coordination effect of nitrile ion-conducting components on lithium ions, enabling lithium ions to preferentially distribute and migrate in the plastic crystal phase, reducing the coupling between lithium ions and polar groups such as carbonyl groups in the polymer backbone, thereby reducing the damage of ion coordination to the hydrogen bond network of the mechanical phase.

[0033] 3. This invention introduces hydrogen-bonded reinforcing monomers into the mechanically supporting phase, enabling the cured polymer network to have more reversible intermolecular interactions. This structure is beneficial for improving the electrolyte's deformation tolerance, interfacial recovery ability after localized damage, and battery stability under mechanical loads. The multifunctional crosslinking agent can form multiple connection nodes during polymerization, improving the dimensional stability and load transfer capacity of the cured electrolyte, and reducing the migration of the crystalline phase under long-term cycling or mechanical disturbances.

[0034] 4. The electrolyte structure described in this invention is an in-situ curing system, adaptable to conventional battery or composite material processes such as coating, impregnation, filling, and thermosetting. Its precursor solution can enter and cure at the electrode / separator interface after assembly, helping to reduce interfacial gaps and form continuous ion channels.

[0035] 5. The structural electrolyte of the present invention has non-flammable and thermosetting network confinement characteristics, which can reduce the risk of leakage, combustion and interface failure of traditional liquid electrolytes under mechanical and thermal abuse conditions.

[0036] 6. This invention can be used to construct carbon fiber structure batteries that combine energy output and structural load-bearing functions, so that the battery is no longer just an auxiliary power source, but can be used as part of the body, shell, support plate or load-bearing component. Attached Figure Description

[0037] Figure 1This is a schematic diagram of the dual continuous phase structure and ion transport mechanism of the thermosetting polymer-based electrolyte (SN volume fraction of about 60%) of the present invention. In the diagram, a is the three-dimensional interpenetrating structure of the elastomeric phase (mechanically supporting phase) and the plastic crystal phase (ion-conducting phase), b is a schematic diagram of the lithium ion transport path in the plastic crystal phase, and c is a schematic diagram of the competitive coordination mechanism between SN and BA-based polymer structural units.

[0038] Figure 2 This is a schematic diagram of the preparation process of the thermosetting polymer-based electrolyte of the present invention.

[0039] Figure 3 This is a schematic diagram illustrating the formation mechanism of thermosetting polymer-based electrolytes.

[0040] Figure 4 For Li + A comparison diagram of coordination interactions with SN (butadienenitrile) and BA (butyl acrylate) structural units, where a represents Li + -SN and Li + - Comparison diagram of coordination structure and binding energy of BA, b is Li + With SN, BA and FSI - A comparison chart of coordination numbers.

[0041] Figure 5 SEM images and phase structure diagrams of the electrolytes with different SN volume fractions are shown. a and d correspond to samples with SN volume fractions of 0%, 40%, 60%, and 80%, respectively. Among them, the 60% sample shows a bicontinuous phase structure in which the elastomer phase and the plastic crystal phase are interpenetrated.

[0042] Figure 6 This is a graph showing the relationship between the volume fraction of the conductive phase and the ionic conductivity and tensile strength of the structural electrolyte.

[0043] Figure 7 Lithium-ion transference number test chart for the preferred structure electrolyte.

[0044] Figure 8 From left to right, the graphs show the relationship between the volume fraction of the conductive phase and the tensile modulus, extrusion modulus, and Young's modulus of the structural electrolyte.

[0045] Figure 9 The left-middle figure shows the cycle performance of the C / C||NCM622 full cell containing the structured electrolyte, and the right-middle figure shows the charge-discharge curve.

[0046] Figure 10 The left figure shows the rate performance of the C / C||NCM622 full cell containing the structured electrolyte, and the right figure shows the charge-discharge curves at different rates.

[0047] Figure 11The graph shows the electrochemical performance of a structural battery containing a structured electrolyte under different types of loads. a, b, and c represent tensile load, compressive load, and bending load, respectively.

[0048] Figure 12 This is a graph showing the temperature and voltage changes during the nailing process of a structural battery containing a structural electrolyte.

[0049] Figure 13 The ARC temperature-time curves are shown for structural batteries with structured electrolytes and conventional liquid electrolyte batteries. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0051] The general preparation process and mechanism of action of this invention are as follows: The thermosetting polymer-based electrolyte of this invention can be prepared according to the route of "separate preparation, proportional mixing, interface wetting, and in-situ curing". First, a mechanically supporting phase precursor containing polymerizable monomers, crosslinking agents, hydrogen bonding reinforcing monomers, lithium salts, and thermal initiators is prepared; second, an ion-conducting phase precursor containing nitrile ion-conducting components, lithium salts, carbonate auxiliaries, and film-forming additives is prepared; then, the two phase precursors are mixed in a predetermined ratio to maintain a flowable state before curing; finally, the mixed precursor liquid is injected into a mold, electrode pores, separator, or battery interior to complete in-situ polymerization and phase separation under thermal initiation conditions.

[0052] like Figure 3 During the curing process, the polymerization of the mechanically supporting phase and the separation of the two phases occur simultaneously. The polymerizable components of the mechanically supporting phase precursor undergo free radical polymerization and form a cross-linked network. Multifunctional cross-linking agents provide three-dimensional network nodes, ensuring that the material does not experience significant flow or leakage after curing; hydrogen-bonded monomers provide reversible intermolecular interactions through amide groups, improving the energy dissipation capacity of the polymer network under tensile, compressive, and flexural loads. As acrylate monomers and multifunctional cross-linking agents gradually form a cross-linked network, the compatibility of different components in the system changes, and the plastic crystal phase gradually separates from the mixed precursor liquid and forms a continuous region. This process differs from post-filling with liquid electrolyte or simple mixing of liquid-phase plasticizers; instead, it directly generates an interpenetrating network during the material forming stage, thus enabling in-situ forming at the electrode / separator interface, carbon fiber fabric pores, and the confined space inside the battery.

[0053] The phase separation in this invention is not simple particle filling, nor is it random residue of liquid electrolyte in the pores of solid resin. Instead, it is an interpenetrating network formed simultaneously during polymerization and crosslinking. This results in a more uniform distribution of the crystalline phase, which is micro- to nano-scale, thus facilitating ion conduction without significantly deteriorating mechanical properties. The elastomeric and crystalline phases are in contact with and interconnected, but their primary functions differ. The elastomeric phase mainly provides load transfer and interfacial support, while the crystalline phase primarily supports lithium-ion migration. This division of labor mitigates the contradiction that "increasing crosslinking density reduces ion conduction."

[0054] This invention further improves ion transport through competitive coordination. In traditional polymer electrolytes, lithium ions often coordinate with polar groups such as oxygen, carbonyl, or ether oxygen groups on the polymer chain. Lithium ion migration depends on the movement of polymer chain segments, leading to coupling between ion migration and mechanical network motion. In contrast, the nitrile component in this invention has a stronger coordination effect on lithium ions, causing lithium ions to preferentially distribute in the crystalline phase, thereby releasing polar groups in the elastomer phase and retaining more hydrogen bonding.

[0055] Specifically, acrylate monomers, such as butyl acrylate, can form an elastomeric skeleton with a certain degree of flexibility after polymerization. This is beneficial for maintaining the continuity of the electrolyte under tensile, compressive, or bending loads, and reduces the risk of interfacial failure caused by brittle fracture.

[0056] Multifunctional crosslinking agents can form multiple connection nodes during polymerization, improving the dimensional stability and load transfer capability of the electrolyte after curing, and reducing the migration of the plastic crystal phase under long-term cycling or mechanical disturbance.

[0057] Hydrogen-bonded monomers are used to enhance intermolecular interactions in the mechanically supporting phase, thereby further improving mechanical strength. Among them, the amide groups in methacrylamide can form hydrogen bonds in the cured polymer network. This interaction not only enhances the energy dissipation capacity of the polymer phase but also provides a certain degree of recovery after local damage or interfacial disturbances.

[0058] Nitrile components, such as succinate, possess high polarity and good lithium salt solubility. The nitrile groups can coordinate with lithium ions, and their coordination ability is stronger than that of polar groups such as carbonyl groups in the acrylate polymer backbone. This results in lithium ions being primarily distributed in the crystalline phase and migrating along continuous conductive channels. Compared to electrolytes that rely entirely on polymer chain movement, this competitive coordination mechanism reduces the interference of lithium ions on the hydrogen bonding network in the polymer's mechanical phase, allowing the mechanical phase to maintain good intermolecular interactions and carrying capacity, while simultaneously enabling the conductive phase to undertake the main lithium ion migration function.

[0059] Compared with traditional liquid electrolytes, the structural electrolyte of this invention can restrict electrolyte flow and interface migration after solidification, reducing the risk of internal dislocation under mechanical load; compared with single-phase thermosetting polymer electrolytes, this invention significantly improves lithium-ion transport capacity through a plastic crystal phase; compared with gel systems containing a large amount of organic liquid electrolyte, this invention improves shape stability and abuse safety through thermosetting networks and plastic crystal quasi-solid phases.

[0060] Performance testing methods For structural characterization, scanning electron microscopy was used to observe the cross-sectional morphology of the electrolyte with different conductive phase ratios, and the elemental distribution results were combined to determine whether the plastic crystal phase formed a continuous network. Differential scanning calorimetry, Fourier transform infrared spectroscopy, Raman spectroscopy, thermogravimetric analysis or X-ray diffraction were used to determine whether the two phases retained their respective characteristic signals.

[0061] Regarding ion conduction and electrochemical performance, the ionic conductivity of the electrolyte under different conductive phase ratios was tested using AC impedance spectroscopy, the activation energy for ion migration was calculated using Arrhenius curves, the lithium-ion transference number was calculated using DC polarization combined with impedance spectroscopy, and the electrochemical stability window was evaluated using linear sweep voltammetry. In battery testing, half-cells or full cells were constructed using an NCM622 cathode, a carbon / carbon composite anode, and the described electrolyte structure, and rate and cycle tests were conducted within a voltage range of 2.8–4.2 V.

[0062] In terms of mechanical properties, a universal testing machine was used to conduct tensile, compression, and springback tests on the cured structural electrolyte, and charge-discharge tests were performed on the structural battery using the electrolyte under tensile, out-of-plane compression, and three-point bending conditions. Regarding safety performance, flame retardancy tests, nail penetration tests, and accelerated calorimetry tests were used to evaluate the response of the electrolyte and structural battery under flame, internal short-circuit, and thermal abuse conditions.

[0063] Example 1: Preparation of thermosetting polymer-based electrolyte A mechanically supported phase precursor was prepared in an argon-atmospheric glove box. Butyl acrylate was used as the main monomer, with an amount of butyl acrylate equal to 70 wt% of the total mass of the polymerizable components of the mechanically supported phase (acrylate monomers, multifunctional crosslinking agents, and hydrogen-bonding reinforcing monomers). Trimethylolpropane triacrylate was added as a multifunctional crosslinking agent, with an amount of trimethylolpropane triacrylate equal to 15 wt% of the total mass of the polymerizable components of the mechanically supported phase. Methacrylamide was added as a hydrogen-bonding reinforcing monomer, with an amount of methacrylamide equal to 15 wt% of the total mass of the polymerizable components of the mechanically supported phase. Lithium difluorosulfonylimide was added as a lithium salt to achieve a final concentration of 1.5 mol / L. -1Azobisisobutyronitrile (AIBN) was added as a thermal initiator, with the amount of AIBN being 0.5 mol% of the total monomer molarity. The above components were mixed sequentially and stirred for 2 h to obtain a homogeneous mechanically supported phase precursor.

[0064] The ion-conducting precursor uses succinate as the main ion-conducting component, and lithium bis(fluorosulfonyl)imide is added to achieve a final lithium salt concentration of 1.5 mol / L. -1 Then, a carbonate co-solvent and an interface stabilizer are added. The carbonate co-solvent is a mixed solvent of EC / EMC / DMC in a volume ratio of 1:1:1, and the total amount is 10 vol% of the succinate volume. The interface stabilizer includes fluoroethylene carbonate and vinylene carbonate, with fluoroethylene carbonate accounting for 15 vol% of the succinate volume and vinylene carbonate accounting for 1 vol% of the succinate volume. After thoroughly mixing the above components, a succinate-rich ion-conductive phase precursor is obtained.

[0065] The mechanically supporting phase precursor and the ion-conducting phase precursor are mixed at the desired volume ratio, preferably with the ion-conducting phase having a volume fraction of 60%. The resulting mixed precursor solution is directly injected into a mold or battery and thermocured at 65°C for 2 hours. During the curing process, the acrylate monomers and crosslinking agent undergo free radical polymerization, while the two phases undergo polymerization-induced phase separation, ultimately yielding a thermosetting polymer-based electrolyte with a bicontinuous structure.

[0066] Example 2: Effect of different conductive phase ratios on the performance of structural electrolytes Following the method in Example 1, samples with SN volume fractions of 0%, 20%, 40%, 50%, 60%, 80%, and 100% were prepared, respectively. The 0% sample did not contain an SN-rich ion-conducting phase, and the 100% sample did not contain a BA-based mechanically supported precursor. The test results are as follows: Figure 6 As the volume fraction of the ion-conducting phase increases, the overall ionic conductivity of the structural electrolyte increases, while the tensile strength and compressive load-bearing capacity gradually decrease. This trend indicates that the crystalline phase mainly contributes to ion transport, while the elastomeric phase mainly contributes to load-bearing capacity.

[0067] In samples with an SN volume fraction of approximately 60%, the structural electrolyte exhibits an ionic conductivity of approximately 6.0 mS cm⁻¹ at room temperature, with a lithium-ion transference number reaching 0.89 (e.g., ...). Figure 7 Tensile strength approximately 5~6 MPa ( Figure 6 This formulation offers a good balance between conductivity, lithium-ion transference number, and mechanical integrity, making it a preferred embodiment for subsequent battery construction.

[0068] Example 3: Verification of competitive coordination mechanism and bicontinuous structure The molecular coordination and structural characterization of the electrolyte obtained in Example 1 were performed. Density functional theory calculations showed that Li + The binding energy with SN is approximately -3.87 eV, significantly stronger than that with Li. + The binding energy with the BA carbonyl group is approximately -2.16 eV. This result indicates that in the electrolyte structure of this invention, lithium ions thermodynamically tend to coordinate with SN rather than strongly couple with the carbonyl group in the polymer mechanical phase. The relevant coordination structure and binding energy results are as follows: Figure 4 As shown in Figure a.

[0069] Further through coordination number, radial distribution function and solid state 7 Li NMR spectroscopy verified the lithium-ion coordination environment. After the introduction of the SN-rich phase, the local coordination environment of lithium ions shifted from being dominated by polymer polar groups to being dominated by SN, indicating that lithium ions are mainly distributed in the SN-rich ion-conductive phase. This coordination regulation weakens the coupling between lithium-ion migration and polymer chain movement, which is beneficial for reducing concentration polarization and increasing the lithium-ion transference number.

[0070] The microstructure of the structural electrolyte was observed using scanning electron microscopy and elemental distribution analysis (see...). Figure 5 When the SN volume fraction is 0%, the sample only forms a BA-based thermosetting crosslinked network, and no SN-rich continuous phase is observed in the SEM morphology. When the SN volume fraction is 20%–40%, the crystalline phase is mostly locally connected or isolated, making it difficult to form continuous ion channels throughout the sample, resulting in limited improvement in conductivity. When the SN volume fraction is 50%–70%, especially around 60%, the SN-rich region exhibits a clearer continuous interpenetrating network. When the SN volume fraction increases to 80% or 100%, the proportion of SN-rich phase is too high and weakens the BA-based continuous supporting phase, significantly reducing the tensile strength and compressive load-bearing capacity of the sample, making it difficult to meet the requirements of the structural battery for electrolyte support and interface support. Combining the DSC, Raman, FT-IR, and TGA results, it can be seen that the two phases retain their respective characteristic signals after curing, indicating that the dual continuous structure of the present invention is mainly formed by polymerization-induced phase separation and physical interpenetration, rather than by complete homogenization of the two phases or the formation of new host chemical bonds.

[0071] Example 4: Construction of a carbon fiber structured battery containing a structural electrolyte In this embodiment, the preferred electrolyte structure obtained in Example 1 is used to construct a carbon fiber structure battery. The positive electrode uses carbon fiber fabric as both the current collector and structural support. The carbon fiber fabric is first soaked in acetone at 60°C for 30 min to remove surface slurry and organic contaminants, then naturally dried, and subsequently placed in a 30 wt% hydrogen peroxide solution at 60°C for 45 min to introduce oxygen-containing functional groups and improve slurry wettability. The treated carbon fiber fabric is then dried for later use.

[0072] 1 g of NCM622 positive electrode active material was mixed with 5 g of single-walled carbon nanotube dispersion, stirred for 6 h and sonicated for 2 h to obtain a uniform positive electrode slurry. The slurry was then coated onto the surface of a pretreated carbon fiber fabric and vacuum dried at 80 °C for 12 h to obtain an NCM622 / carbon fiber fabric structure positive electrode.

[0073] The negative electrode is a self-supporting carbon / carbon composite material. This negative electrode is obtained by chemical vapor deposition of a carbon matrix using PAN-based carbon fiber felt, followed by high-temperature graphitization. The resulting carbon / carbon composite material possesses electrical conductivity, lithium storage, and structural support functions, and can be used directly as a negative electrode without the need for additional polymer binders, conductive agents, or metal current collectors.

[0074] After sequentially stacking the structural positive electrode, the alumina-coated polyethylene separator, and the carbon / carbon negative electrode, the precursor solution of the structural electrolyte from Example 1 was injected into the electrode / separator assembly to fully wet the interface. Subsequently, it was cured in situ at 65°C for 2 hours to obtain an electrochemical core containing a thermosetting polymer-based structural electrolyte. Further, carbon fiber / resin prepreg was deposited on the outer side of the core, and after vacuum bagging and thermosetting, an integrated all-fiber structure battery was obtained.

[0075] Performance Test Results and Analysis from Figure 1 It can be seen that the electrolyte structure is not a single homogeneous polymer, nor is it a simple filling of a liquid electrolyte within a solid framework. Instead, it is an interpenetrating structure composed of an elastomeric phase and a crystalline phase. The elastomeric phase forms a continuous support network within the system, while the crystalline phase forms nanoscale rapid ion migration channels. This structure is the basis for the synergistic effect of mechanical and electrochemical functions in this invention.

[0076] from Figure 2 As can be seen, this invention employs a process route of separately preparing two-phase precursors, mixing them in proportion, injecting them into a battery or mold, and then thermally curing them in situ. This route eliminates the need for first preparing an independent electrolyte membrane and then performing complex bonding; instead, it allows for direct curing and molding within the electrode / separator assembly. This improves the interfacial contact between the electrolyte and the electrode and facilitates adaptation to the fabrication processes of lithium-ion batteries and carbon fiber structure batteries.

[0077] from Figure 4 As can be seen from the calculation results, Li + The first solvated sheath layer is mainly composed of SN molecules, and Li + It tends to coordinate with SN. This figure illustrates that, in this invention, the plastic phase not only plays a role in dilution or plasticization, but more importantly, it guides lithium ions into the conductive phase through its strong lithium ion coordination ability, thus supporting the competitive coordination mechanism at the molecular level.

[0078] Figure 5Morphological results indicate that, in this invention, the BA-based mechanical support phase and the SN-rich conductive phase must coexist and be in an appropriate ratio. An SN volume fraction of approximately 60% is the preferred condition for forming a bicontinuous structure of elastomeric phase and plastic crystal phase while taking into account both ion conduction and mechanical support.

[0079] from Figure 6 It can be seen that as the proportion of the crystalline phase increases, the overall ionic conductivity of the electrolyte increases, while the tensile strength gradually decreases. In the region with a low proportion of conductive phase, the increase in conductivity is not significant, indicating that ion migration is still limited by the discrete phase structure. When the proportion of conductive phase enters the range of approximately 50% to 70%, the conductivity increases significantly, indicating that continuous ion channels are gradually established. At this proportion, the mechanical properties of the electrolyte decrease relatively slowly, which meets the requirements of the structural battery. This figure demonstrates that the proportion of conductive phase is an important parameter for regulating the ion transport performance of the electrolyte in this invention.

[0080] Figure 7 This is a lithium-ion transport number graph for a preferred electrolyte structure. From... Figure 7 It can be seen that the preferred electrolyte structure exhibits a high lithium-ion transference number, reaching approximately 0.89. This high transference number indicates a higher proportion of lithium-ion contribution to current conduction, which can reduce concentration polarization during battery cycling. This result is consistent with the crystalline phase and competitive coordination mechanism of this invention, demonstrating that lithium ions can migrate more effectively in the conductive phase.

[0081] from Figure 8 It can be seen that as the proportion of the conductive phase increases, the tensile, compressive, and Young's moduli of the structural electrolyte all show a decreasing trend. This is because the crystalline phase mainly undertakes the function of ion conduction and has a certain dilution effect on the cross-linked support network. Figure 6 and Figure 8 According to the explanation, the proportion of conductive phase cannot be increased indefinitely, but needs to be balanced between conductivity and mechanical modulus; the sample with a conductive phase volume fraction of about 60% exhibits better overall performance between the two.

[0082] from Figure 9 It can be seen that the full cell maintains a relatively stable capacity and a high coulombic efficiency during cycling, indicating that the electrolyte structure of this invention has good compatibility with the positive and negative electrode interfaces. Combined with the rate performance, it can be seen that this electrolyte structure not only achieves initial capacity output but also maintains a relatively stable interface and ion transport channels during continuous charge and discharge.

[0083] from Figure 10It can be seen that the full cell using the electrolyte structure of this invention can provide a high discharge specific capacity at low rates. The capacity gradually decreases as the rate increases, but recovers upon rate recovery, indicating that the battery has a reversible rate response. This result shows that the ion channels formed by the structured electrolyte can meet the lithium-ion transport requirements between the C / C anode and the NCM622 cathode, and the presence of the thermosetting network does not completely limit the electrochemical reaction.

[0084] from Figure 11 It can be seen that the structured battery maintains stable capacity output under tensile, compressive, and bending loads, exhibiting slower capacity decay compared to traditional liquid electrolyte pouch batteries. This result indicates that the cured thermosetting polymer network can provide interfacial support during bending deformation, reducing the relative displacement between the electrodes, separator, and electrolyte, thereby improving electrochemical stability under mechanical loads.

[0085] Figure 12 This is a graph showing the temperature and voltage changes during the nail penetration process of a structural battery containing a structural electrolyte. From... Figure 12 As can be seen, the battery temperature did not experience a significant surge during the needle penetration process, remaining within a range close to room temperature. This result demonstrates that even if localized mechanical damage triggers an internal short circuit, the electrolyte structure of this invention can still mitigate the risk of severe thermal expansion through its non-flammable properties and solidified network constraint. This figure can be used in conjunction with photographs of the actual device after needle penetration or voltage change data, but retaining the temperature curve in the official accompanying figures is sufficient to highlight the safety features.

[0086] Figure 13 This shows the ARC temperature-time curves for the structured battery and the conventional liquid electrolyte battery. From... Figure 13 It can be seen that traditional liquid electrolyte pouch batteries experience rapid temperature rise near lower temperatures, while the rapid thermal runaway initiation temperature of the battery containing the electrolyte structure of this invention is significantly delayed. This result indicates that the electrolyte structure of this invention can improve the safety threshold of the battery under thermal abuse conditions and delay the violent exothermic process. Combined with the needle penetration temperature curve, it can be seen that this invention exhibits better safety performance under both mechanical and thermal abuse conditions.

[0087] In summary, this invention addresses the problem of existing structural electrolytes' inability to simultaneously achieve mechanical load-bearing capacity and efficient lithium-ion transport by providing a thermosetting polymer-based structural electrolyte. This structural electrolyte uses a thermosetting cross-linked polymer network as the mechanical support phase and a nitrile-rich component as the ion-conducting phase. During in-situ curing, polymerization-induced phase separation forms a bicontinuous elastomer-plastic crystal phase structure, allowing the load transfer path and the lithium-ion transport path to be mutually specialized yet continuously interconnected within the same electrolyte. Therefore, this structural electrolyte can provide rapid lithium-ion conductivity while maintaining the stability and interfacial support capabilities of the thermosetting polymer structure, making it suitable for lithium-ion batteries and structural energy storage devices requiring both energy output and load-bearing capabilities.

[0088] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a thermosetting polymer-based electrolyte, characterized in that, include: After mixing the mechanically supporting phase precursor and the ion-conducting phase precursor, they are cross-linked and cured in situ. A dual continuous phase structure consisting of an elastomer phase and a plastic crystal phase is formed by polymerization-induced phase separation, thus obtaining the thermosetting polymer-based electrolyte. The mechanically supported phase precursor includes acrylate monomers, multifunctional crosslinking agents, hydrogen bond-enhancing monomers, lithium salts, and initiators; the ion-conducting phase precursor includes nitrile ion-conducting components, lithium salts, and interface-stabilizing additives. The acrylate monomer is a monomer that includes only one acrylate group, and the multifunctional crosslinker is a crosslinker that includes at least two acrylate groups.

2. The method for preparing the thermosetting polymer-based electrolyte according to claim 1, characterized in that, The multifunctional crosslinking agent includes one or more of trimethylolpropane triacrylate, polyethylene glycol diacrylate, diethylene glycol diacrylate, and pentaerythritol triacrylate; And / or, the acrylate monomers include one or more of butyl acrylate, butyl methacrylate, ethyl acrylate, methyl acrylate, and polyethylene glycol methyl ether acrylate; And / or, the hydrogen bond reinforcing monomer includes one or more of acrylamide, methacrylamide, N-hydroxymethylacrylamide, and N-vinylpyrrolidone.

3. The method for preparing the thermosetting polymer-based electrolyte according to claim 1, characterized in that, The nitrile ion-conducting components include one or more of succinic acid, adiponitrile, glutaronitrile, and ethylenedionitrile; And / or, the lithium salt includes one or more of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, and lithium difluorooxalate borate. And / or, the interface stabilizing additive includes one or more of fluoroethylene carbonate, vinylene carbonate, ethylene carbonate, methyl ethyl carbonate, dimethyl carbonate, and diethyl carbonate.

4. The method for preparing the thermosetting polymer-based electrolyte according to any one of claims 1-3, characterized in that, The ion-conducting phase precursor accounts for 20% to 90% of the total volume of the mechanically supporting phase precursor and the ion-conducting phase precursor; preferably 40% to 80%.

5. The method for preparing the thermosetting polymer-based electrolyte according to any one of claims 1-3, characterized in that, The acrylate monomers account for 40% to 90% of the total mass of the acrylate monomers, multifunctional crosslinking agents, and hydrogen bond reinforcing monomers, preferably 60% to 80%. And / or, the multifunctional crosslinking agent accounts for 5% to 30% of the total mass of the acrylate monomer, the multifunctional crosslinking agent, and the hydrogen bond reinforcing monomer, preferably 10% to 20%; And / or, the hydrogen bond reinforcing monomer accounts for 5% to 30% of the total mass of the acrylate monomer, the multifunctional crosslinking agent and the hydrogen bond reinforcing monomer, preferably 10% to 20%; And / or, the concentration of lithium salt in the mechanically supported phase precursor is 0.5~3.0 mol L. -1 Preferably, the concentration is 1.0~2.0 mol / L. -1 .

6. The method for preparing the thermosetting polymer-based electrolyte according to claim 3, characterized in that, The final concentration of lithium salt in the ion-conducting phase precursor is 0.5~3.0 mol L⁻¹, preferably 1.0~2.0 mol L⁻¹. -1 ; The interface stabilizing additive simultaneously comprises fluoroethylene carbonate, vinylene carbonate, ethylene carbonate, methyl ethyl carbonate, and dimethyl carbonate. The amount of fluoroethylene carbonate is 5% to 25% of the volume of the nitrile ion-conducting component; the amount of vinylene carbonate is 0.5% to 5% of the volume of the nitrile ion-conducting component; the interface stabilizing additive also includes three co-solvents in a volume ratio of ethylene carbonate, methyl ethyl carbonate, and dimethyl carbonate of 1:1:1, and the total amount of the co-solvents is 5% to 20% of the volume of the nitrile ion-conducting component.

7. The method for preparing the thermosetting polymer-based electrolyte according to any one of claims 1-3, characterized in that, The in-situ cross-linking curing temperature is 50~90℃, and the time is 0.5~8 h; And / or, the initiator includes one or more of azobisisobutyronitrile, benzoyl peroxide, and azobisisoheptanenitrile, and the amount of the initiator is 0.1% to 2.0% of the total mass of the acrylate monomer, the multifunctional crosslinking agent and the hydrogen bond reinforcing monomer.

8. A thermosetting polymer-based electrolyte, characterized in that, It is prepared by the preparation method according to any one of claims 1-7.

9. A lithium-ion battery, characterized in that, It includes a positive electrode, a negative electrode, a separator, and a thermosetting polymer-based electrolyte as described in claim 8.

10. The lithium-ion battery according to claim 9, characterized in that, The positive electrode is a carbon fiber-supported positive electrode containing lithium-ion battery active positive electrode material, and the negative electrode is a carbon fiber or carbon fiber composite material negative electrode; the assembly method of the lithium-ion structure battery includes: stacking the positive electrode, separator and negative electrode and adding them into a mixed precursor liquid composed of the mechanical support phase precursor and the ion-conducting phase precursor, so that the mixed precursor liquid wets the interface of the positive electrode, separator and negative electrode; then performing in-situ crosslinking and curing to obtain an electrochemical core.

Images