Crosslinked composite solid electrolyte composition having both high conductivity and high flexibility

Abstract

The present invention relates to the technical field of lithium ion battery materials, and discloses a cross-linked composite solid electrolyte composition with high conductivity and high flexibility, the composition comprises 35-65 wt% of an inorganic electrolyte filler, 5-15 wt% of a lithium salt, 1-10 wt% of a cross-linking agent, an initiator and a polymer matrix, and the inorganic filler is active powder subjected to nanometer grinding and annealing pretreatment. The preparation method comprises the following steps: dissolving and dispersing the components in acetonitrile to prepare slurry, coating and drying, and initiating an in-situ cross-linking reaction through ultraviolet light or heating to form the film. The high-content nanofiller is utilized to reduce the crystallinity of the polymer, and the in-situ three-dimensional cross-linked network is matched to enhance the mechanical property, so that the problem of low room-temperature conductivity of the polyethylene oxide-based electrolyte is solved. The obtained electrolyte membrane has excellent flexibility and lithium dendrite inhibition capability, an electrochemical window is effectively widened, and the cycling stability of a solid-state lithium battery is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion battery materials, in particular to a cross-linked composite solid electrolyte composition with high conductivity and high flexibility. BACKGROUND

[0002] With the rapid development of portable electronic devices and new energy automobile industry, the market puts forward higher requirements for the energy density and safety of energy storage devices. Traditional liquid lithium ion batteries have safety hazards such as easy leakage, easy combustion and thermal runaway due to the use of organic liquid electrolyte. Solid-state batteries use non-flammable solid-state electrolyte to replace liquid electrolyte, which is expected to fundamentally solve the safety problem of batteries. Among many solid-state electrolyte systems, polyethylene oxide (PEO) has become the most widely studied polymer electrolyte matrix material due to its low density, good film-forming property and good interface stability to lithium negative electrode.

[0003] However, the polyethylene oxide-based solid-state electrolyte faces performance bottlenecks in practical application. First, the linear polyethylene oxide molecular chain has a high crystallinity at room temperature, which blocks the lithium ion transmission channel, and its room temperature ionic conductivity is usually low. This means that solid-state batteries using such electrolytes often need to work at a relatively high temperature (such as above 60℃), which limits their application range at room temperature. Second, the mechanical modulus of pure polyethylene oxide matrix is low, and the texture is soft, which makes it difficult to effectively inhibit the growth of lithium dendrites through mechanical blocking during long cycle of the battery. Once the lithium dendrites pierce the electrolyte film, it will cause internal short circuit of the battery and lead to safety accidents.

[0004] In order to improve the above problems, the existing technology often uses the method of adding inorganic ceramic fillers to the polymer matrix to prepare composite solid electrolyte, trying to combine the high strength and high conductivity of inorganic materials with the flexibility of polymers. However, this physical blending modification strategy still has some shortcomings. Due to the large difference in chemical properties between inorganic fillers and the surface of organic polymers, the interface compatibility between the two phases is poor, resulting in high interface contact resistance, which hinders the transmission of lithium ions across the interface. Especially when the amount of inorganic fillers is increased to greatly reduce the crystallinity of the polymer, the nanoparticles are prone to agglomeration, resulting in phase separation or pore defects in the composite material. This not only fails to effectively improve the conductivity, but also damages the continuity and density of the electrolyte film, making the film material brittle and reducing the flexibility, which is difficult to meet the dual requirements of processing performance and mechanical strength for soft package batteries and other devices. Therefore, developing a composite solid electrolyte that can maintain uniform dispersion of components at high filler loading, while also having high room temperature ionic conductivity, high mechanical strength and excellent flexibility, is a technical problem that needs to be solved in this field. SUMMARY

[0005] To address the shortcomings of existing technologies, this invention provides a cross-linked composite solid electrolyte composition with both high conductivity and high flexibility, and its preparation method. This solves the technical problems of existing polyoxyethylene solid electrolytes, which suffer from low ionic conductivity due to high room temperature crystallinity, difficulty in suppressing lithium dendrite growth due to insufficient mechanical strength, and easy agglomeration under high inorganic filler content, thus making it difficult to balance flexibility and electrochemical performance.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] The first aspect of this invention provides a cross-linked composite solid electrolyte composition that combines high conductivity and high flexibility, employing the following technical solution:

[0008] A cross-linked composite solid electrolyte composition possessing both high conductivity and high flexibility is made from raw materials comprising the following weight percentages:

[0009] Inorganic electrolyte filler: 35-65 wt%;

[0010] Lithium salt: 5-15 wt%

[0011] Crosslinking agent: 1-10 wt%

[0012] Initiator: 0.01-1 wt%;

[0013] Polymer matrix: Balance.

[0014] By employing the above technical solution, this invention resolves the contradiction between conductivity and mechanical properties through the synergistic effect of high-content nanofillers and in-situ crosslinking networks. Specifically, the content of inorganic electrolyte filler is increased to 35-65 wt%. Utilizing the large specific surface area of ​​the nanofiller, the Lewis acid sites on its surface interact with the Lewis base sites on the polymer matrix segments. This interaction disrupts the regular arrangement of polymer segments, reduces the crystallinity of the polymer, thereby expanding the volume of the amorphous region used for lithium-ion transport and improving room-temperature ionic conductivity. Furthermore, by introducing a three-dimensional network structure formed by a crosslinking agent, the dispersed inorganic nanofiller is physically fixed in the polymer matrix, preventing agglomeration or phase separation at high filler contents. Simultaneously, this crosslinking network restricts excessive slippage of polymer segments, imparting high tensile strength to the electrolyte membrane, thereby effectively suppressing lithium dendrite growth.

[0015] Preferably, the crosslinking agent is used in an amount of 5-40 wt% of the polymer matrix; the inorganic electrolyte filler is a powder that has undergone nano-grinding and high-temperature annealing pretreatment.

[0016] By adopting the above technical solution, the pretreated filler reduces surface impurities and lattice defects, which helps to reduce interfacial transport resistance. Controlling the crosslinking agent ratio within the above range can balance network density and chain segment mobility, ensuring mechanical strength while avoiding a decrease in ion mobility due to excessive crosslinking density.

[0017] Preferably, the polymer matrix is ​​polyethylene oxide, and the lithium salt is lithium bis(trifluoromethanesulfonyl)imide; the molar ratio of the ether oxygen atoms in the polyethylene oxide to the lithium ions in the lithium bis(trifluoromethanesulfonyl)imide is [insert molar ratio here]. .

[0018] By employing the above technical solution, this ratio range can balance the carrier concentration and the degree of dissociation of anions and cations. The large-volume anion of lithium bis(trifluoromethanesulfonylimide) can further assist in suppressing the crystallization of polyethylene oxide due to its plasticizing effect.

[0019] Preferably, the crosslinking agent is one of polyethylene glycol dimethacrylate or polyethylene glycol diacrylate; the initiator is a photoinitiator. Or one of the thermal initiators, azobisisobutyronitrile.

[0020] By adopting the above technical solution, the crosslinking agent molecular chain contains ethoxy groups, which have good chemical compatibility with polyoxyethylene esters and help to form a uniform crosslinking network.

[0021] Preferably, the inorganic electrolyte filler is one of NASICON-type lithium aluminum germanium phosphate, garnet-type oxide solid electrolyte, or sulfide solid electrolyte of silver sulfide type; the average particle size D50 of the inorganic electrolyte filler is 50-450 nm. The preparation method of the inorganic electrolyte filler with an average particle size D50 of 50-450 nm includes: dispersing micron-sized raw material powder in an anhydrous solvent, circulating and grinding it using 0.05-0.5 mm grinding media for 30 minutes to 4 hours, drying and recovering it... Lower annealing for 0.5-2 hours.

[0022] By adopting the above technical solution, the filler particle size can be controlled within the range of 50-450 nm, which increases the contact area between the polymer and the filler. Annealing after grinding can repair the lattice distortion generated during the grinding process and maintain the ion transport characteristics of the inorganic material.

[0023] By adopting the above technical solution, this thickness range reduces the battery's internal resistance while ensuring mechanical support. The in-situ formed three-dimensional network structure is the structural basis for achieving a composite electrolyte that combines high conductivity and excellent flexibility.

[0024] A preferred method for preparing a cross-linked composite solid electrolyte composition possessing both high conductivity and high flexibility includes the following steps:

[0025] S1. Dissolve the polymer matrix, lithium salt and crosslinking agent in anhydrous acetonitrile and stir to form a homogeneous polymer solution;

[0026] S2. Add inorganic electrolyte filler to the polymer solution and perform dispersion treatment to obtain composite slurry;

[0027] S3. Add an initiator to the composite slurry, stir evenly and degas;

[0028] S4. The degassed composite slurry is coated onto the substrate and vacuum dried to remove the acetonitrile solvent, forming a solid electrolyte membrane.

[0029] S5. The dried solid electrolyte membrane is subjected to ultraviolet light irradiation or heat treatment to initiate an in-situ crosslinking reaction, thereby obtaining a composite solid electrolyte composition.

[0030] By adopting the above technical solution, this invention solves the problems of difficult film formation and poor uniformity of highly filled slurries using an in-situ curing strategy. First, the system is in the liquid phase during the dispersion stage, which is beneficial for the uniform dispersion of high-content inorganic fillers. Second, using acetonitrile as a solvent can simultaneously dissolve the polymer and lithium salt. Removing the solvent before the crosslinking reaction avoids solvent molecules occupying crosslinking sites or forming micropore defects in the film. Finally, the precursor is directly polymerized and crosslinked on the substrate by ultraviolet light or thermal initiation. The resulting chemical bond network stabilizes the inorganic particles in the polymer matrix, ensuring the compactness and uniformity of the film.

[0031] Preferably, the dispersion process in step S2 includes ultrasonic dispersion for 20-40 minutes, followed by mechanical stirring for 3-8 hours.

[0032] By adopting the above technical solution, the soft agglomeration of nanoparticles is opened by ultrasonic action, and the suspension state is maintained by long-term mechanical stirring, thus ensuring the uniformity and stability of the composite slurry.

[0033] Preferably, in step S5, the wavelength of the ultraviolet irradiation is 365 nm, the power density is 20-40 mW / cm², and the irradiation time is 30-120 seconds; the temperature of the heat treatment is... The time is 3-5 hours.

[0034] By adopting the above technical solutions, the initiation energy and time are controlled to ensure that the crosslinking reaction proceeds fully, while preventing membrane surface shrinkage or local stress concentration caused by excessive heat generation due to the reaction rate.

[0035] Preferably, the vacuum drying in step S4 is performed during... The drying process is carried out at a certain temperature for 10-14 hours; steps S1 to S5 are carried out in an inert gas atmosphere with a water oxygen content of less than 0.1 ppm.

[0036] By employing the above technical solution, the low-temperature, long-term drying method avoids the phenomenon of rapid solvent evaporation leading to a dense surface while leaving residual solvent inside. Strict control of water and oxygen content prevents lithium salt hydrolysis and the failure of highly active fillers, ensuring the electrochemical stability of the final electrolyte membrane.

[0037] This invention provides a cross-linked composite solid electrolyte composition possessing both high conductivity and high flexibility, and a method for preparing the same. It offers the following advantages:

[0038] 1. This invention introduces a high content of nanoscale inorganic electrolyte filler, utilizing the interaction between the filler surface and polymer matrix segments to effectively reduce the crystallinity of polyethylene oxide and increase the proportion of amorphous regions in the polymer used for lithium-ion transport. This structural design overcomes the inherent defect of low room temperature conductivity in conventional polyethylene oxide electrolytes, improving the lithium-ion transport efficiency of the composite solid electrolyte at room temperature without adding liquid plasticizers.

[0039] 2. This invention utilizes in-situ curing technology to construct a three-dimensional cross-linked network structure within the polymer matrix. This network restricts the aggregation of inorganic particles, ensuring uniform dispersion of the filler even at high filler loadings. Simultaneously, the cross-linked network enhances the mechanical modulus of the polymer matrix, enabling the electrolyte membrane to achieve high tensile strength at break while maintaining flexibility for easy processing and assembly. This allows for effective suppression of lithium dendrite growth and puncture by mechanical force, improving battery operational safety.

[0040] 3. This invention achieves efficient composite formation of active inorganic fillers and cross-linked polymer networks, constructing a continuous and stable lithium-ion transport channel and reducing the interfacial impedance between the organic and inorganic phases. Compared to simple physical blending systems, this dense cross-linked composite structure exhibits better electrochemical stability, broadens the oxidative decomposition voltage window of the electrolyte, thus enabling the adaptation of cathode materials with higher voltage platforms and extending the cycle life of solid-state lithium metal batteries. Detailed Implementation

[0041] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the preparation examples, examples, comparative examples, and test examples. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] Preparation Examples 1-3:

[0043] Preparation Example 1:

[0044] This preparation example provides a pretreated lithium aluminum germanium phosphate nanopowder with an average particle size D50 of 50 nm, including the following steps:

[0045] In an argon-filled glove box, 100g of commercially available micron-sized lithium aluminum germanium phosphate powder (original D50 approximately 2μm) was mixed with 500mL of anhydrous ethanol to prepare a pre-dispersion, which was then pumped into a nano-sand mill containing 0.05mm high-purity zirconium oxide grinding beads.

[0046] Start the circulating cooling water system to control the material temperature below Adjust the grinding speed to 2500 rpm for circulating grinding.

[0047] Particle size was measured every 30 minutes, and after grinding for about 4 hours, the D50 reached 50 nm. The resulting slurry was dried and recovered using a spray dryer, and then processed in a tube furnace. Annealing for 1 hour to eliminate lattice stress, followed by natural cooling, yields the desired powder.

[0048] Preparation Example 2:

[0049] This preparation example provides a pretreated lithium aluminum germanium phosphate nanopowder with an average particle size D50 of 250 nm, including the following steps:

[0050] Its process flow is basically the same as that of Preparation Example 1, the only difference being the adjustment of grinding parameters;

[0051] Specifically, 0.2mm high-purity zirconia grinding beads were used, the grinding speed was adjusted to 1500rpm, and the cycle grinding time was shortened to 1.5 hours. After online monitoring confirmed that the particle size D50 reached 250nm, the grinding was stopped. After drying and annealing, the desired powder was obtained.

[0052] Preparation Example 3:

[0053] This preparation example provides a pretreated lithium aluminum germanium phosphate nanopowder with an average particle size D50 of 450 nm, including the following steps:

[0054] Its process flow is basically the same as that of Preparation Example 1, the only difference being the adjustment of grinding parameters;

[0055] Specifically, 0.5mm high-purity zirconia grinding beads were used, the grinding speed was adjusted to 1000rpm, and the cycle grinding time was shortened to 30 minutes. After online monitoring confirmed that the particle size D50 reached 450nm, the grinding was stopped. After drying and annealing, the desired powder was obtained.

[0056] Examples 1-11:

[0057] Example 1:

[0058] This embodiment provides an oxide composite solid electrolyte membrane based on in-situ crosslinking, wherein the inorganic filler has a mass fraction of 55 wt%, and includes the following steps:

[0059] (1) In a glove box filled with dry argon (water and oxygen content both less than 0.1 ppm), polyethylene oxide (PEO), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and crosslinking agent polyethylene glycol dimethacrylate (PEGDM) were added to anhydrous acetonitrile solvent, wherein the molar ratio of PEO to LiTFSI was as follows: Mix the ingredients according to the specified ratio, and stir magnetically for 6 hours until completely dissolved to form a homogeneous polymer solution;

[0060] (2) Add lithium aluminum germanium phosphate (LAGP) powder with a particle size D50 of 50 nm obtained in Preparation Example 1 to the above polymer solution, regardless of the total solid mass ( The LAGP mass fraction was 55wt%, and the PEGDM addition amount was 20wt% of the PEO mass; then ultrasonic dispersion was performed for 30 minutes, followed by strong mechanical stirring for 4 hours to obtain a uniformly dispersed composite slurry.

[0061] (3) Add to the composite slurry

[0062] The amount added is 1% of the mass of PEGDM. After stirring evenly, it is allowed to stand to degas.

[0063] (4) Apply the slurry to the polytetrafluoroethylene mold substrate using a doctor blade, control the wet film thickness, and vacuum dry at room temperature for 12 hours to remove acetonitrile solvent;

[0064] (5) Place the dried film in a UV curing device and cure it at a wavelength of 365 nm and a power density of 100 ppm. By irradiating the membrane with ultraviolet light for 60 seconds to induce a cross-linking reaction, a composite solid electrolyte membrane with a thickness of approximately 50 μm can be obtained.

[0065] Example 2:

[0066] This embodiment provides an oxide composite solid electrolyte membrane based on in-situ crosslinking, with an inorganic filler mass fraction of 35 wt%, including the following steps:

[0067] The preparation process is exactly the same as in Example 1, except that the raw material feeding ratio is different. In step (2) of this example, the amount of lithium aluminum germanium phosphate (LAGP) powder (from the same source as in Preparation Example 1) is adjusted so that its mass fraction in the total solid component is 35wt%, and the other components (PEO, LiTFSI, PEGDM) keep their respective relative proportions unchanged, and finally a composite solid electrolyte membrane of the same thickness is obtained.

[0068] Example 3:

[0069] This embodiment provides an oxide composite solid electrolyte membrane based on in-situ crosslinking, with an inorganic filler mass fraction of 65 wt%, including the following steps:

[0070] The preparation process is exactly the same as in Example 1, except that the raw material feeding ratio is different. In step (2) of this example, the amount of lithium aluminum germanium phosphate (LAGP) powder (from the same source as in preparation example 1) is adjusted so that its mass fraction in the total solid component is 65wt%, and the other components (PEO, LiTFSI, PEGDM) keep their respective relative proportions unchanged. Due to the high solid content, the mechanical stirring time in step (2) is extended to 8 hours to ensure uniform mixing, and finally a composite solid electrolyte membrane of the same thickness is obtained.

[0071] Example 4:

[0072] This embodiment provides an oxide composite solid electrolyte membrane based on in-situ crosslinking, using a filler with a particle size D50 of 250 nm, and includes the following steps:

[0073] The preparation process and the proportions of each component are exactly the same as in Example 1, except that the type of inorganic filler used in step (2) is different. In this example, lithium aluminum germanium phosphate (LAGP) powder with an average particle size D50 of 250 nm obtained in Preparation Example 2 is used to finally prepare a composite solid electrolyte membrane of the same thickness.

[0074] Example 5:

[0075] This embodiment provides an oxide composite solid electrolyte membrane based on in-situ crosslinking, using a filler with a particle size D50 of 450 nm, and includes the following steps:

[0076] The preparation process and the proportions of each component are exactly the same as in Example 1, except that the type of inorganic filler used in step (2) is different. In this example, lithium aluminum germanium phosphate (LAGP) powder with an average particle size D50 of 450 nm obtained in Preparation Example 3 was used to finally prepare a composite solid electrolyte membrane of the same thickness.

[0077] Example 6:

[0078] This embodiment provides an in-situ crosslinked oxide composite solid electrolyte membrane for verifying the compatibility of different types of oxide electrolyte materials, including the following steps:

[0079] The preparation process and the proportions of each component are exactly the same as in Example 1, except that the type of inorganic filler used in step (2) is different. In this example, lithium aluminum titanium phosphate (LATP) powder is used instead of LAGP powder in the raw materials and reagents section to finally obtain a composite solid electrolyte membrane of the same thickness.

[0080] Example 7:

[0081] This embodiment provides a sulfide composite solid electrolyte membrane based on in-situ crosslinking for verifying the compatibility of sulfide electrolyte materials, including the following steps:

[0082] The preparation process is basically the same as in Example 1, but the operating environment is more strictly controlled. Steps (1) to (5) are carried out in a high-purity argon glove box with a water oxygen content of less than 0.1 ppm. In step (2), the sulfide electrolyte (Li6PS5Cl) of silver sulfide germanium ore in the raw materials and reagents section is used instead of LAGP powder, while the proportions of PEO, LiTFSI and PEGDM remain unchanged, and a composite solid electrolyte membrane of the same thickness is finally obtained.

[0083] Example 8:

[0084] This embodiment provides an oxide composite solid electrolyte membrane based on in-situ crosslinking, used to verify the compatibility of different crosslinking agents, including the following steps:

[0085] The preparation process and the proportions of each component are basically the same as in Example 1, the only difference being the type of crosslinking agent used in step (1). In this example, polyethylene glycol diacrylate (PEGDA) is used to replace PEGDM in Example 1 by mass, and a composite solid electrolyte membrane of the same thickness is finally obtained.

[0086] Example 9:

[0087] This embodiment provides an oxide composite solid electrolyte membrane based on in-situ crosslinking, comprising the following steps:

[0088] The preparation process and the proportion of each component are basically the same as in Example 1, except that the amount of crosslinking agent is different. In step (2), the amount of crosslinking agent PEGDM is adjusted to 5wt% of the mass of PEO, while the relative proportions of the other components (PEO, LiTFSI, LAGP) and the proportion of HMPP initiator to PEGDM (1%) remain unchanged, and a composite solid electrolyte membrane of the same thickness is finally obtained.

[0089] Example 10:

[0090] This embodiment provides an oxide composite solid electrolyte membrane based on in-situ crosslinking, comprising the following steps:

[0091] The preparation process and the proportion of each component are basically the same as in Example 1, except that the amount of crosslinking agent is different. In step (2), the amount of crosslinking agent PEGDM is adjusted to 40wt% of the mass of PEO, while the relative proportions of the other components (PEO, LiTFSI, LAGP) and the proportion of HMPP initiator to PEGDM (1%) remain unchanged, and a composite solid electrolyte membrane of the same thickness is finally obtained.

[0092] Example 11:

[0093] This embodiment provides an oxide composite solid electrolyte membrane based on an in-situ thermosetting process to verify the compatibility of different curing methods, including the following steps:

[0094] (1) The raw material dissolution and dispersion steps are basically the same as in Example 1, that is, to prepare a composite slurry containing PEO, LiTFSI, PEGDM (20wt%) and LAGP (55wt%);

[0095] (2) The difference lies in the selection of the initiator and the curing process: In step (3), the thermal initiator azobisisobutyronitrile (AIBN) is used instead of the photoinitiator HMPP, and the amount of AIBN added is 2% of the mass of PEGDM;

[0096] (3) Apply the slurry to the polytetrafluoroethylene mold base using a scraper, first on... Vacuum drying for 12 hours removes acetonitrile solvent;

[0097] (4) Then place the dried membrane in Heating in an oven for 4 hours initiates a thermal crosslinking reaction, and after natural cooling, a composite solid electrolyte membrane with a thickness of approximately 50 μm can be obtained.

[0098] Comparative Examples 1-4:

[0099] Comparative Example 1:

[0100] Compared with Example 1, the difference is that no inorganic filler was added. Specifically, in step (2), the lithium aluminum germanium phosphate (LAGP) powder obtained in Example 1 was not added, and only a pure cross-linked polymer solid electrolyte membrane was prepared. The other raw materials and preparation processes were the same.

[0101] Comparative Example 2: Compared with Example 1, the difference lies in the particle size of the inorganic filler used. Specifically, in step (2), commercially available micron-sized lithium aluminum germanium phosphate powder (average particle size D50 of 2 μm) that has not been ground in Preparation Example 1 is added, while the other raw material ratios and preparation processes are the same.

[0102] Comparative Example 3:

[0103] Compared with Example 1, the difference is that no in-situ crosslinking network was constructed. Specifically, no crosslinking agent PEGDM was added in step (1), and no photoinitiator HMPP was added in step (3). Only straight-chain PEO and LAGP were mixed, and a physically blended composite electrolyte membrane was formed after the solvent evaporated. The other raw materials and preparation processes were the same.

[0104] Comparative Example 4:

[0105] Compared to Example 1, the difference lies in the type of inorganic filler (comparison with inert fillers). Specifically, in step (2), nano-silica with the same particle size (50 nm) is used. Inert filler was used instead of active lithium aluminum germanium phosphate (LAGP) filler, and the remaining raw material ratios and preparation processes were the same.

[0106] Test Example 1-2:

[0107] Test Example 1:

[0108] The solid electrolyte membranes prepared in Examples 1-11 and Comparative Examples 1-4 were characterized in terms of performance, and the specific methods are as follows:

[0109] (1) The solid electrolyte membrane was cut into 16mm diameter discs and sandwiched between two stainless steel sheets to assemble a blocked battery (SS / / SPE / / SS). An electrochemical impedance spectroscopy test was performed using an electrochemical workstation, with the frequency range... to Amplitude 10mV, test temperature According to the Nyquist plot intercept resistance and formula Calculate the ionic conductivity.

[0110] (2) Assemble a lithium / solid electrolyte / lithium (Li / / SPE / / Li) symmetrical battery. The chronoamperometry combined with AC impedance spectroscopy was used for testing. A constant DC polarization voltage of 10mV was applied to the battery, and the initial current was recorded. and steady-state current The interfacial impedance before and after polarization was measured respectively. and The lithium-ion transference number was calculated using the Bruce-Vincent formula.

[0111] (3) Assemble stainless steel / solid electrolyte / lithium (SS / / SPE / / Li) half-cells. Linear sweep voltammetry was used for testing, with a scan rate of... The voltage scan range is 2.0V to 6.0V. The inflection point voltage at which the current density rises sharply is used to determine the oxidation decomposition voltage.

[0112] (4) Cut the solid electrolyte membrane into standard dumbbell-shaped strips and perform tensile testing using a universal testing machine at a tensile rate of 5 mm / min. Record the stress-strain curve and read the tensile strength at break.

[0113] Table 1. Summary of Performance Test Data

[0114]

[0115] Results Analysis and Conclusions

[0116] Table 1 shows that the ionic conductivity of Example 1 is Compared to Comparative Example 1 ( This represents a two-order-of-magnitude improvement. The 50nm LAGP filler has a large specific surface area. Its Lewis acid sites interact with the ether oxygen atoms of the PEO segments, promoting lithium salt dissociation and increasing the concentration of free lithium ions. This interferes with PEO segment rearrangement, reduces polymer crystallinity, and increases the transport channels in the amorphous region.

[0117] Regarding mechanical flexibility, the elongation at break in all embodiments exceeded 50%. Comparing Example 3 (65% high filler content, elongation 58.2%) with Comparative Example 2 (micron-sized filler, elongation 98.6%) and Comparative Example 1 (pure polymer, elongation 350.2%), it can be seen that although adding inorganic fillers reduces the material's ductility to some extent, thanks to the effective bonding of the in-situ crosslinking network at the interface between the polymer matrix and the nanofiller, the composite electrolyte of this invention maintains high tensile strength (…). While maintaining flexibility to meet the requirements of processing and battery assembly, it also retains the necessary flexibility.

[0118] Compared with Examples 1, 4, 5 and Comparative Example 2, the ionic conductivity decreased as the filler particle size increased from 50 nm to the micrometer level. In Comparative Example 2, the micrometer-sized filler had a small contact area and agglomerated, failing to form an effective interaction network and thus failing to improve the interfacial impedance.

[0119] The conductivity and lithium-ion transference number of Example 1 are higher than those of Comparative Example 4. Active LAGP is superior to inert LAGP. In addition to inhibiting crystallization, it also participates in lithium-ion transport, forming a two-phase conduction system consisting of the polymer phase and the inorganic phase.

[0120] Comparative Example 3, without a cross-linked network, had a tensile strength of only 0.48 MPa. Although its elongation at break was high (280.5%), it lacked mechanical strength and had a gel-like morphology, making it unable to effectively block lithium dendrites. Example 1 introduced an in-situ cross-linked network, increasing the tensile strength to 8.42 MPa. Furthermore, the cross-linked network and the filler synergistically blocked anion migration, widening the electrochemical stability window from 4.10 V (Comparative Example 1) and 4.65 V (Comparative Example 3) to 5.35 V.

[0121] Example 7 uses a sulfide system and the highest ionic conductivity and transference number were measured, indicating that the process is suitable for different types of highly active electrolyte materials.

[0122] In-situ crosslinking combined with 50nm active filler solved the problems of low conductivity, poor mechanical strength, and insufficient high-pressure resistance of PEO-based electrolytes. By controlling the filler particle size and crosslinking density, a balance between ion transport efficiency and mechanical properties was achieved.

[0123] Test Example 2:

[0124] Solid-state button batteries were assembled using lithium iron phosphate (LiFePO4) as the positive electrode material and lithium metal as the negative electrode. The electrochemical performance of the electrolyte membranes prepared in the examples and comparative examples was verified.

[0125] Experimental steps:

[0126] (1) Mix lithium iron phosphate (LFP), conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) at a mass ratio of 8:1:1. Add Methylpyrrolidone (NMP) is ground and dispersed to form a slurry, which is then coated onto the surface of carbon-coated aluminum foil. Vacuum dried for 12 hours, rolled and cut into circular electrode sheets with a diameter of 14 mm, with the active material loading controlled at [value missing]. .

[0127] (2) In an argon glove box (water and oxygen content <0.1ppm), a CR2032 button cell was assembled using a 15.6mm diameter lithium metal sheet as the negative electrode, the electrolyte membrane (16mm diameter) of Examples 1-11 and Comparative Examples 1-4 as the separator and electrolyte, and the above LFP electrode as the positive electrode.

[0128] (3) The battery was left to stand at the test temperature for 12 hours. A constant current charge-discharge test was performed using a battery testing system. The cycle performance test temperature was 25℃, the voltage range was 2.5V-3.8V, and the charge-discharge rate was 0.5C (1C=170mAh / g). The discharge specific capacity and capacity retention rate after 200 cycles were recorded. The rate performance test temperature was... Charge and discharge at step rates of 0.1C, 0.2C, 0.5C, 1.0C, and 2.0C, with 5 cycles per stage, and finally return to 0.1C.

[0129] Table 2. LFP / SPE / Li Full Cells Electrochemical performance test results

[0130]

[0131] Note: - indicates that the voltage has reached the cutoff condition and the effective capacity cannot be released, or the battery has failed and the test is interrupted.

[0132] Results Analysis and Conclusions:

[0133] Table 2 shows that the battery in Example 1... The discharge capacity at 0.1C was 158.4 mAh / g, and the retention rate after 200 cycles was 93.4%. Comparative Example 1 (pure PEO-based) exhibited only 24.5 mAh / g capacity due to the low ionic conductivity of PEO at room temperature and severe battery polarization. Example 1, by introducing 50 nm LAGP filler, suppressed PEO crystallization and improved the room temperature lithium-ion transport efficiency.

[0134] Regarding cycle stability, Comparative Example 3 (uncrosslinked) experienced a short circuit at cycle 42. The physical blend system lacked sufficient mechanical strength to suppress lithium dendrite growth, which punctured the electrolyte membrane, causing contact between the positive and negative electrodes. Examples 1, 8, and 11 constructed a network structure through in-situ crosslinking, combined with inorganic fillers to enhance the modulus, thus preventing lithium dendrite penetration. Example 9, due to its low crosslinking density and limited mechanical blocking ability, experienced a short circuit at cycle 85.

[0135] Regarding rate performance, Example 1 maintained a capacity of 125.6 mAh / g at 2.0C. Comparative Example 2 (micron-sized filler) and Comparative Example 4 (inert)... Capacity decreases at high rates. LAGP active nanofillers provide additional... The system improves the transmission channel and enhances interfacial compatibility, reducing interfacial impedance. In Comparative Example 2, micron-sized particles lead to poor solid-solid interface contact, resulting in increased polarization under high current. In Example 10, excessively high crosslinking density restricts polymer chain movement, reduces ion mobility, and causes a deterioration in rate performance.

[0136] Example 7 (sulfide system) achieved a capacity of 140.2 mAh / g at 2.0C and a cycle retention rate of 95.1%, indicating that the preparation process is compatible with sulfide electrolytes and retains their high ion transport characteristics.

[0137] The results confirmed that the synergistic effect of the in-situ cross-linked network and the active nanofiller solved the problems of difficult room temperature operation and short cycle life of solid lithium metal batteries, and improved rate performance while ensuring mechanical safety.

Claims

1. A cross-linked composite solid electrolyte composition possessing both high conductivity and high flexibility, characterized in that, Made from raw materials comprising the following weight percentages: Inorganic electrolyte filler: 35-65 wt%; Lithium salt: 5-15 wt% Crosslinking agent: 1-10 wt% Initiator: 0.01-1 wt%; Polymer matrix: Balance.

2. The cross-linked composite solid electrolyte composition with both high conductivity and high flexibility according to claim 1, characterized in that, The crosslinking agent is used in an amount of 5-40 wt% of the polymer matrix; the inorganic electrolyte filler is a powder that has undergone nano-grinding and high-temperature annealing pretreatment.

3. The cross-linked composite solid electrolyte composition with both high conductivity and high flexibility according to claim 1, characterized in that, The polymer matrix is ​​polyethylene oxide, and the lithium salt is lithium bis(trifluoromethanesulfonylimide). The molar ratio of the ether oxygen atoms in the polyethylene oxide to the lithium ions in the lithium bis(trifluoromethanesulfonylimide) is: .

4. The cross-linked composite solid electrolyte composition with both high conductivity and high flexibility according to claim 1, characterized in that, The crosslinking agent is either polyethylene glycol dimethacrylate or polyethylene glycol diacrylate; The initiator is a photoinitiator. Or one of the thermal initiators, azobisisobutyronitrile.

5. The cross-linked composite solid electrolyte composition with both high conductivity and high flexibility according to claim 1, characterized in that, The inorganic electrolyte filler is one of NASICON-type lithium aluminum germanium phosphate, garnet-type oxide solid electrolyte, or sulfide solid electrolyte of silver sulfide type. The average particle size D50 of the inorganic electrolyte filler is 50-450 nm.

6. The cross-linked composite solid electrolyte composition with both high conductivity and high flexibility according to claim 5, characterized in that, The preparation method of the inorganic electrolyte filler with an average particle size D50 of 50-450 nm includes: The micron-sized raw material powder is dispersed in an anhydrous solvent and circulated and ground for 0.5-4 hours using 0.05-0.5mm grinding media. After drying and recovery, it is annealed at 550℃-650℃ for 0.5-2 hours.

7. The cross-linked composite solid electrolyte composition with both high conductivity and high flexibility according to claim 1, characterized in that, The preparation method of the composite solid electrolyte composition includes the following steps: S1. Dissolve the polymer matrix, lithium salt and crosslinking agent in anhydrous acetonitrile and stir to form a homogeneous polymer solution; S2. Add inorganic electrolyte filler to the polymer solution and perform dispersion treatment to obtain composite slurry; S3. Add an initiator to the composite slurry, stir evenly and degas; S4. The degassed composite slurry is coated onto the substrate and vacuum dried to remove the acetonitrile solvent, forming a solid electrolyte membrane. S5. The dried solid electrolyte membrane is subjected to ultraviolet light irradiation or heat treatment to initiate an in-situ crosslinking reaction, thereby obtaining a composite solid electrolyte composition.

8. The cross-linked composite solid electrolyte composition with both high conductivity and high flexibility according to claim 7, characterized in that, The dispersion process in step S2 includes ultrasonic dispersion for 20-40 minutes, followed by mechanical stirring for 3-8 hours.

9. The cross-linked composite solid electrolyte composition with both high conductivity and high flexibility according to claim 7, characterized in that, The ultraviolet irradiation in step S5 has a wavelength of 365 nm and a power density of 20-40 mW / cm². 2 The irradiation time is 30-120 seconds; The heat treatment is performed at a temperature of 70-90℃ for 3-5 hours.

10. The cross-linked composite solid electrolyte composition with both high conductivity and high flexibility according to claim 7, characterized in that, The vacuum drying in step S4 is carried out at a temperature of 20-45°C for 10-14 hours.

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