A ternary composite interface layer, a preparation method thereof and a composite pole piece

Abstract

The application belongs to the technical field of batteries, and provides a ternary composite interface layer, a preparation method thereof and a composite pole piece. g The ternary composite interface layer comprises the following components in mass fractions: a high polymer binder with a glass transition temperature T ‑4 ≥200℃ of 5-20 parts, an ionic liquid plasticizer obtained by mixing a lithium salt and an ionic liquid of 10-30 parts, and inorganic ceramic fillers of 1-10 parts; the molar concentration of the lithium salt in the ionic liquid plasticizer is 0.1-5.0 mol / L. The ternary composite interface layer can not only form a firm physical and chemical combination with the separator and the active material layer of the pole piece, significantly improving the peeling strength, but also achieve an ionic conductivity at room temperature of the order of 10 ‑4 S / cm, significantly reducing the interface impedance of the battery. The thermal shrinkage rate of the ternary composite interface layer at 180℃ can be as low as 0.5%, the high-temperature dimensional stability is excellent, the thermal safety performance of the battery is greatly improved, and the ternary composite interface layer has a very broad application prospect.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a ternary composite interface layer, its preparation method, and a composite electrode. Background Technology

[0002] The continuous improvement in the energy density of lithium-ion batteries has placed higher demands on the compactness and safety of the battery's internal structure. The thermal bonding technology of the separator and the positive electrode usually introduces a polymer adhesive layer between the two to integrate them, replacing the traditional simple physical stacking. This technology aims to improve the mechanical stability of the battery, improve interface contact, and suppress the risk of internal short circuits, and is therefore regarded as one of the key processes for the next generation of high-energy-density batteries.

[0003] Currently, the mainstream technical solutions in the industry mainly focus on patterning polymer adhesive layers (such as PVDF, SBR, etc.) to alleviate problems such as stress concentration, membrane wrinkles, and misalignment that occur during thermal bonding. For example, the existing Chinese invention patent with patent number CN119447710A achieves stress release by setting a discontinuous adhesive layer with a specific hollow structure.

[0004] However, regardless of whether the adhesive layer is continuous or patterned, its material system is essentially still a polymer that is ionicly and electronically insulated. This traditional "adhesive layer" approach has the following inherent limitations: 1. Limited functionality and increased impedance: It only provides physical bonding, which inevitably increases the interface impedance of the battery, which is not conducive to fast charging and power performance improvement.

[0005] 2. Insufficient heat resistance: The thermal stability of polymer matrices, represented by PVDF, is limited. When the battery temperature rises abnormally, it is prone to softening and shrinkage, which may lead to bonding failure and cause greater safety hazards.

[0006] 3. Narrow process window: The pattern accuracy of the adhesive layer, the hot pressing temperature and pressure need to be strictly matched, the process is complex and the error tolerance is low.

[0007] Therefore, existing technologies have reached a bottleneck in fine-tuning the morphology of the "adhesive layer." To fundamentally solve the above problems, there is an urgent need for an innovative "interface layer" that originates from the material itself. This layer should not only achieve strong adhesion but also possess high ionic conductivity and excellent thermal stability, thereby breaking through the limitations of existing technologies. Summary of the Invention

[0008] In view of this, the present invention provides a ternary composite interface layer and its preparation method, as well as a composite electrode, to solve the problems of high battery interface impedance, poor high-temperature safety, and difficulty in synergistic optimization of electrochemical and mechanical properties caused by existing polymer adhesive layers.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a ternary composite interface layer comprising the following components in parts by mass: 5-20 parts of polymeric binder, 10-30 parts of ionic liquid plasticizer, and 1-10 parts of inorganic ceramic filler; the glass transition temperature T of the polymeric binder. g ≥200℃; the ionic liquid plasticizer is obtained by mixing lithium salt and ionic liquid; the molar concentration of lithium salt in the ionic liquid plasticizer is 0.1~5.0 mol / L.

[0010] Preferably, the polymeric binder includes one or more of nitrogen-containing heterocyclic polymers, polyarylene ether resins, fluoropolymers, heat-resistant modified epoxy resins, and heat-resistant phenolic resins.

[0011] Preferably, the nitrogen-containing heterocyclic polymer includes one or more of polyimide, polyamide-imide, and polyether-imide; the polyarylether resin includes one or more of polyetheretherketone, polyphenylene sulfide, and polyethersulfone; the fluoropolymer includes polytetrafluoroethylene and / or tetrafluoroethylene-hexafluoropropylene copolymer; the heat-resistant modified epoxy resin includes one or more of epoxy resin cured with aromatic amine curing agents, epoxy resin cured with acid anhydride curing agents, and epoxy resin cured with multifunctional epoxy resin systems; the heat-resistant phenolic resin includes one or more of nitrile rubber modified phenolic resin, epoxy modified phenolic resin, and silicone modified phenolic resin.

[0012] Preferably, the lithium salt comprises one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium hexafluorophosphate, and lithium perchlorate; the ionic liquid comprises imidazole ionic liquids and / or pyrrolidine ionic liquids; the imidazole ionic liquid comprises one or more of 1-ethyl-3-methylimidazole bis(trifluoromethanesulfonyl)imide, 1-butyl-3-methylimidazole bis(trifluoromethanesulfonyl)imide, and 1-ethyl-3-methylimidazole bis(fluorosulfonyl)imide; the pyrrolidine ionic liquid comprises one or more of 1-methyl-1-propylpyrrolidine bis(trifluoromethanesulfonyl)imide, N-methyl-N-butylpyrrolidine bis(trifluoromethanesulfonyl)imide, and N-methyl-N-propylpyrrolidine bis(fluorosulfonyl)imide.

[0013] Preferably, the particle size D of the inorganic ceramic filler is... 50 The nanometer size is 20~100 nm; the inorganic ceramic filler includes nano-oxides and / or fast ion conductors; the nano-oxides include nano-alumina and / or nano-silica; the fast ion conductors include one or more of lithium lanthanum zirconium oxide, lithium lanthanum titanium oxide, and lithium titanium aluminum phosphate.

[0014] The present invention also provides a method for preparing the above-mentioned ternary composite interface layer, comprising the following steps: 1) Mix polymer binder, ionic liquid plasticizer, inorganic ceramic filler and organic solvent to obtain slurry; 2) Coat the surface of the positive electrode with the slurry and dry it to form a ternary composite interface layer.

[0015] Preferably, the organic solvent in step 1) includes one or more of N-methylpyrrolidone, N,N-dimethylformamide and N,N-dimethylacetamide; the solid content of the slurry is 15~60 wt%.

[0016] Preferably, the drying temperature in step 2) is 60~100℃ and the time is 5~30 min; the thickness of the ternary composite interface layer is 1~20 μm.

[0017] The present invention also provides a composite electrode, comprising a positive electrode, a separator, and a ternary composite interface layer located between the two; the ternary composite interface layer is the aforementioned ternary composite interface layer.

[0018] This invention also provides a method for preparing a composite electrode, comprising the following steps: A positive electrode coated with a ternary composite interface layer is sequentially hot-pressed and heat-cured with a separator to obtain a composite electrode; the ternary composite interface layer is the aforementioned ternary composite interface layer.

[0019] Preferably, the hot-pressing composite temperature is 120~160℃, the pressure is 0.3~1.0 MPa, and the time is 5 s~10 min.

[0020] Preferably, the heat treatment curing temperature is 160~200℃ and the time is 1~4 h.

[0021] As can be seen from the above technical solution, compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention abandons the single polymer binder and constructs a ternary composite interface layer consisting of a polymer binder, an ionic liquid plasticizer, and an inorganic ceramic filler. The mechanism of this ternary composite interface layer differs fundamentally from that of traditional polymer binders: traditional binders (such as PVDF) rely solely on the viscoelasticity of the polymer itself for physical bonding, their insulation hinders ion transport, and they exhibit poor thermal stability. In this invention, the ionic liquid plasticizer not only acts as a processing aid but also constructs continuous lithium-ion transport channels within the interface layer; the inorganic ceramic filler improves thermal stability and mechanical strength, and some fast ion conductors themselves can also provide ion conduction pathways; the heat-resistant polymer binder forms a stable three-dimensional framework. Through synergistic effects, these three components transform the interface layer into a multifunctional solid composite electrolyte interface at the microscopic level, possessing ion conductivity, high-temperature shape retention, and strong adhesion, fundamentally resolving the contradiction between interface impedance and thermal safety in traditional technologies. In other words, this invention transforms a passive and harmful "insulating layer" in the battery into an active and beneficial "functionalized interface layer," representing a fundamental breakthrough brought about by material system innovation. In addition, this ternary composite interface layer not only has excellent ion conductivity and outstanding thermal stability, but also forms a strong physicochemical bond with the porous membrane and the electrode active material layer, significantly improving the peel strength.

[0022] 2. The ternary composite interface layer of the present invention introduces an ionic liquid as a functional medium that combines plasticization and high ionic conductivity, utilizing the ionic liquid's ability to handle high glass transition temperatures (T0). g The plasticizing effect of the heat-resistant polymer binder allows for thermal bonding of the interface layer at relatively mild temperatures, simplifying the process. Furthermore, the ionic liquid can construct rapid ion transport channels, enabling the interface layer to achieve an ionic conductivity of up to 10 at room temperature. -4 This significantly reduces the interfacial impedance of the battery, which is on the order of S / cm.

[0023] 3. The ternary composite interface layer of the present invention also introduces inorganic ceramic filler as a thermal stabilizer and mechanical enhancer, which together with the heat-resistant polymer binder forms a rigid skeleton, so that the interface layer still maintains dimensional stability at 180°C, greatly improving the thermal safety of the battery. Detailed Implementation

[0024] This invention provides a ternary composite interface layer comprising the following components in parts by mass: The mixture comprises 5-20 parts of polymeric binder, 10-30 parts of ionic liquid plasticizer, and 1-10 parts of inorganic ceramic filler; preferably 6-18 parts of polymeric binder, 12-28 parts of ionic liquid plasticizer, and 2-8 parts of inorganic ceramic filler; more preferably 8-15 parts of polymeric binder, 15-25 parts of ionic liquid plasticizer, and 4-7 parts of inorganic ceramic filler; and even more preferably 10-12 parts of polymeric binder, 18-20 parts of ionic liquid plasticizer, and 5-6 parts of inorganic ceramic filler.

[0025] In this invention, the glass transition temperature T of the polymeric binder g ≥200℃, preferably 205~300℃, more preferably 210~280℃, and even more preferably 220~250℃.

[0026] In this invention, the ionic liquid plasticizer is obtained by mixing lithium salt and ionic liquid; the molar concentration of lithium salt in the ionic liquid plasticizer is 0.1~5.0 mol / L, preferably 0.3~4 mol / L, more preferably 0.5~3 mol / L, and even more preferably 1~2 mol / L.

[0027] In this invention, the polymeric binder preferably includes one or more of nitrogen-containing heterocyclic polymers, polyarylene ether resins, fluoropolymers, heat-resistant modified epoxy resins, and heat-resistant phenolic resins.

[0028] In this invention, the nitrogen-containing heterocyclic polymer preferably includes one or more of polyimide (PI), polyamide-imide (PAI), and polyether-imide (PEI); the polyarylene ether resin preferably includes one or more of polyether ether ketone (PEEK), polyphenylene sulfide (PPS), and polyether sulfone (PES); the fluoropolymer preferably includes polytetrafluoroethylene (PTFE) and / or tetrafluoroethylene-hexafluoropropylene copolymer (FEP); the heat-resistant modified epoxy resin preferably includes one or more of epoxy resin cured with aromatic amine curing agents, epoxy resin cured with acid anhydride curing agents, and epoxy resin cured with multifunctional epoxy resin systems; the heat-resistant phenolic resin preferably includes one or more of nitrile rubber modified phenolic resin, epoxy modified phenolic resin, and silicone modified phenolic resin.

[0029] In this invention, the lithium salt preferably includes one or more of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium hexafluorophosphate (LiPF6), and lithium perchlorate (LiClO4); the ionic liquid preferably includes imidazole ionic liquids and / or pyrrolidine ionic liquids; the imidazole ionic liquid preferably includes 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([EMIM][TFSI]) and 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([BMIM]). [TFSI] and 1-ethyl-3-methylimidazolium difluorosulfonylimide salt ([EMIM][FSI]); the pyrrolidine ionic liquid preferably includes one or more of 1-methyl-1-propylpyrrolidine bis(trifluoromethanesulfonyl)imide salt ([Py13][TFSI]), N-methyl-N-butylpyrrolidine bis(trifluoromethanesulfonyl)imide salt ([Py14][TFSI]) and N-methyl-N-propylpyrrolidine difluorosulfonylimide salt ([Py13][FSI]).

[0030] In this invention, the particle size D of the inorganic ceramic filler is... 50 The nm size is 20-100 nm, preferably 25-90 nm, more preferably 30-80 nm, and even more preferably 40-50 nm; the inorganic ceramic filler is preferably spherical or near-spherical particles; the inorganic ceramic filler preferably includes nano-oxides and / or fast ion conductors; the nano-oxides preferably include nano-alumina (Al2O3) and / or nano-silica (SiO2); the fast ion conductors preferably include lithium lanthanum zirconium oxide (Li7La3Zr2O3). 12 LLZO), lithium lanthanum titanium oxide (Li 3x La 2 / 3-x TiO3, LLTO) and lithium titanium aluminum phosphate (Li 1+x Al x Ti 2-x One or more of (PO4)3, LATP.

[0031] The present invention also provides a method for preparing the above-mentioned ternary composite interface layer, comprising the following steps: 1) Mix polymer binder, ionic liquid plasticizer, inorganic ceramic filler and organic solvent to obtain slurry; 2) Coat the surface of the positive electrode with the slurry and dry it to form a ternary composite interface layer.

[0032] In this invention, the organic solvent in step 1) preferably includes one or more of N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), and N,N-dimethylacetamide (DMAC); the solid content of the slurry is 15-60 wt%, preferably 22-55 wt%, more preferably 28-50 wt%, and even more preferably 33-45 wt%.

[0033] In this invention, the mixing method described in step 1) preferably includes one or more of ball milling, high-speed shear dispersion and planetary stirring.

[0034] In this invention, the shape of the coating in step 2) preferably includes one or more of stripes, dots, and waves; when the shape of the coating is stripes or waves, the direction of the coating is preferably horizontal and / or vertical, the area of ​​each stripe or wave is ≤ the area of ​​the coating area, and the number of coatings N1 ≥ 1; when the shape of the coating is dots, the diameter of each dot is ≤ the width of the coating area, and the number of coatings N2 ≥ 1.

[0035] In this invention, the drying temperature in step 2) is 60~100℃, preferably 65~90℃, more preferably 70~85℃, and even more preferably 75~80℃; the drying time is 5~30 min, preferably 8~28 min, more preferably 10~25 min, and even more preferably 15~20 min; the thickness of the ternary composite interface layer is 1~20 μm, preferably 3~16 μm, more preferably 5~15 μm, and even more preferably 8~10 μm.

[0036] The present invention also provides a composite electrode, comprising a positive electrode, a separator, and a ternary composite interface layer located between the two; the ternary composite interface layer is the aforementioned ternary composite interface layer.

[0037] This invention also provides a method for preparing a composite electrode, comprising the following steps: A positive electrode coated with a ternary composite interface layer is sequentially hot-pressed and heat-cured with a separator to obtain a composite electrode; the ternary composite interface layer is the aforementioned ternary composite interface layer.

[0038] In this invention, the temperature of the hot-pressing composite is 120~160℃, preferably 125~155℃, more preferably 130~150℃, and even more preferably 135~140℃; the pressure of the hot-pressing composite is 0.3~1.0 MPa, preferably 0.4~0.9 MPa, more preferably 0.5~0.8 MPa, and even more preferably 0.6~0.7 MPa; the time of the hot-pressing composite is 5 s~10 min, preferably 10 s~5 min, more preferably 30 s~2 min, and even more preferably 60 s~1.5 min.

[0039] In this invention, the heat treatment curing temperature is 160~200℃, preferably 165~195℃, more preferably 170~190℃, and even more preferably 175~180℃; the heat treatment curing time is 1~4 h, preferably 1.5~3.8 h, more preferably 2~3.5 h, and even more preferably 2.5~3 h.

[0040] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0041] Example 1

[0042] The components of the ternary composite interface layer in this embodiment are: PAI adhesive (T) g 10 parts of ionic liquid plasticizer (obtained by mixing LiTFSI and [Py13][TFSI], with a molar concentration of LiTFSI of 0.5 mol / L and CAS number of [Py13][TFSI] 223437-05-6), and nano-Al2O3 (particle size D) at 280℃. 50 Two copies of 50 nm were used.

[0043] The preparation method of the ternary composite interface layer is as follows: The above components were mixed with N-methylpyrrolidone (NMP, 78 parts by mass), dispersed by high-speed shearing, and ball-milled for 24 h to obtain a slurry with a solid content of 22 wt%. This slurry was then coated onto the surface of a positive electrode sheet in a strip coating manner. The positive electrode sheet contained lithium iron phosphate (LiFePO4), a conductive agent (conductive carbon black), and a binder (polyvinylidene fluoride PVDF) in a mass ratio of 94:3:3, and was coated onto an aluminum foil current collector. Specifically, three parallel strip coatings were coated along the length (longitudinal) of the positive electrode sheet; each strip was 5 mm wide, and the center-to-center distance between adjacent strips was 1 / 4 of the electrode sheet width; the length of the coating extended to cover the entire width of the electrode sheet. After drying at 80 °C for 10 min, a ternary composite interface layer with a thickness of 5 μm was formed.

[0044] The preparation method of composite electrodes is as follows: A polyethylene (PE) separator was placed on the surface of a positive electrode coated with a ternary composite interface layer (the separator was in contact with the ternary composite interface layer). The electrode was then hot-pressed at 130°C and 0.5 MPa for 30 s, and finally heat-cured in a vacuum environment at 160°C for 2 h to obtain an integrated composite electrode.

[0045] Example 2

[0046] The components of the ternary composite interface layer in this embodiment are: 15 parts of PAI binder (same as in Example 1), 10 parts of ionic liquid plasticizer (obtained by mixing LiTFSI and [Py13][TFSI], with a molar concentration of LiTFSI of 1.0 mol / L and CAS number of [Py13][TFSI] 223437-05-6), and nano-SiO2 (particle size D) 50 Three copies of 30 nm were used.

[0047] The preparation method of the ternary composite interface layer is as follows: The above components were mixed with N-methylpyrrolidone (NMP), dispersed by high-speed shearing and ball milled for 24 h to obtain a slurry with a solid content of 28 wt%. The slurry was then coated onto the surface of a positive electrode sheet (same as in Example 1) with lithium iron phosphate (LiFePO4) as the positive electrode active material and coated on an aluminum foil current collector using the same coating method as in Example 1. After drying at 80 °C for 10 min, a ternary composite interface layer with a thickness of 5 μm was formed.

[0048] The preparation method of the composite electrode is the same as in Example 1.

[0049] Example 3

[0050] The components of the ternary composite interface layer in this embodiment are: PI adhesive (T g 8 parts of ionic liquid plasticizer (obtained by mixing LiTFSI and [EMIM][TFSI], with a molar concentration of 0.8 mol / L for LiTFSI and CAS number 174899-82-2 for [EMIM][TFSI]), and 20 parts of LLZO powder (particle size D) 50 Five copies of 80 nm were used.

[0051] The preparation method of the ternary composite interface layer is as follows: The above components were mixed with N-methylpyrrolidone (NMP, 67 parts by mass), dispersed by high-speed shearing and ball milled for 24 h to obtain a slurry with a solid content of 33 wt%. The slurry was then coated onto the surface of a positive electrode sheet (same as in Example 1) with lithium iron phosphate (LiFePO4) as the positive electrode active material and coated on an aluminum foil current collector using the same coating method as in Example 1. After drying at 80°C for 10 min, a ternary composite interface layer with a thickness of 5 μm was formed.

[0052] The preparation method of composite electrodes is as follows: A polyethylene (PE) separator is covered on the surface of a positive electrode coated with a ternary composite interface layer (the separator is in contact with the ternary composite interface layer). Then, hot pressing is performed at 150°C and 0.5 MPa for 60 s, and finally heat treatment is carried out in a vacuum environment at 180°C for 2 h to obtain an integrated composite electrode.

[0053] Comparative Example 1

[0054] The components of the adhesive layer in this comparative example are: 12 parts of polyvinylidene fluoride (PVDF) adhesive.

[0055] The method for preparing the adhesive layer is as follows: The above components were mixed with N-methylpyrrolidone (NMP, 88 parts by mass), dispersed by high-speed shearing and ball milled for 24 h to obtain a slurry; then the slurry was coated onto the surface of a positive electrode sheet (same as in Example 1) with lithium iron phosphate (LiFePO4) as the positive electrode active material and coated on an aluminum foil current collector using the same coating method as in Example 1, and dried at 80°C for 10 min to form an adhesive layer with a thickness of 5 μm.

[0056] The preparation method of composite electrodes is as follows: A polyethylene (PE) separator is placed over the surface of the positive electrode sheet coated with an adhesive layer (the separator and adhesive layer are in contact). Then, hot-pressing is performed for 10 seconds at 90°C and 0.5 MPa, within the optimal process window for PVDF material, to obtain an integrated composite electrode sheet. (Since PVDF is a thermoplastic material, its bonding is achieved through hot pressing, eliminating the need for subsequent high-temperature heat treatment curing.) Comparative Example 2 The components of the interface layer in this comparative example are: 10 parts of PAI binder (same as in Example 1) and 10 parts of ionic liquid plasticizer (obtained by mixing LiTFSI and [Py13][TFSI], with a molar concentration of 0.5 mol / L for LiTFSI and CAS number 223437-05-6 for [Py13][TFSI]).

[0057] The method for preparing the interface layer is as follows: The above components were mixed with N-methylpyrrolidone (NMP, 80 parts by mass), dispersed by high-speed shearing and ball milled for 24 h to obtain a slurry with a solid content of 20 wt%. The slurry was then coated onto the surface of a positive electrode sheet (same as in Example 1) with lithium iron phosphate (LiFePO4) as the positive electrode active material and coated on an aluminum foil current collector using the same coating method as in Example 1. After drying at 80°C for 10 min, an interface layer with a thickness of 5 μm was formed.

[0058] The preparation method of composite electrodes is as follows: A polyethylene (PE) separator is covered on the surface of the positive electrode coated with an interface layer (the separator is in contact with the interface layer), and then hot-pressed at 130°C and 0.5 MPa for 30 s. Finally, it is heat-cured in a vacuum environment at 160°C for 2 h to obtain an integrated composite electrode.

[0059] Detection of ionic conductivity: The slurry of the ternary composite interface layer in Examples 1-3 and the slurry of the adhesive layer in Comparative Examples 1-2 were prepared into independent, dense thin film discs. Their bulk resistance was then tested by electrochemical impedance spectroscopy (EIS), and their ionic conductivity at room temperature (25°C) was calculated.

[0060] Testing of thermal dimensional stability: The integrated composite electrode sheets prepared in Examples 1-3 and Comparative Examples 1-2 were cut into standard-sized samples (50 mm × 50 mm), placed in a forced-air drying oven at 180°C and left to stand for 30 min. After being taken out and cooled to room temperature (25°C), their dimensional changes were measured and the thermal shrinkage rate was calculated.

[0061] Testing of interfacial peel strength: Using a universal testing machine, the bonding strength between the separator and the positive electrode in the composite electrodes prepared in Examples 1-3 and Comparative Examples 1-2 was tested at a peel angle of 90° and a constant speed of 50 mm / min.

[0062] Thermal stability analysis: According to the slurry formulations of Examples 1-3 and Comparative Examples 1-2, respectively, the slurries were coated onto flat polytetrafluoroethylene (PTFE) plates. After undergoing the same drying, hot-pressing, and heat-curing processes as in Examples 1-3 and Comparative Examples 1-2, independent, self-supporting film samples were obtained by peeling. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to test the interface layer materials in Examples 1-3 and Comparative Examples 1-2 to evaluate their glass transition temperatures (Tg). g ) and thermal decomposition behavior.

[0063] Battery cycle performance, rate performance, and high-temperature storage performance testing: The composite electrodes prepared in Examples 1-3 and Comparative Examples 1-2 were used as positive electrodes, and lithium metal sheets were used as counter electrodes / reference electrodes. A general electrolyte (a mixed solution of EC / DMC in 1 mol / L LiPF6, wherein the volume ratio of EC to DMC was 1:1) was used to assemble CR2032 coin cells in an argon-protected glove box.

[0064] Cycling performance: Constant current charge-discharge cycles were performed at a rate of 1 C within a voltage range of 2.5 to 4.2 V, and the discharge capacity retention rate was recorded after 500 cycles.

[0065] Rate performance: First, activate and test the baseline capacity at a rate of 0.2 C. Then, discharge at rates of 0.5 C, 1 C, 2 C, and 5 C in sequence, record the discharge capacity at each rate, and calculate the retention rate based on the capacity at 0.2 C.

[0066] High-temperature storage performance: Fully charged (charged to 4.2 V) batteries were stored in an 85°C constant temperature chamber for 24 h, then cooled to room temperature. The change in battery thickness was measured, and the batteries were discharged to examine capacity recovery.

[0067] The results of the above tests are shown in Table 1.

[0068] Table 1 Performance test results of ternary composite interface layer and battery

[0069] As shown in Table 1, the interface layers of the ternary composite systems provided in Examples 1-3 of this invention are comprehensively and significantly superior to those of Comparative Example 1, which uses a traditional PVDF adhesive layer, in key indicators such as ion conductivity, high-temperature dimensional stability, interfacial bonding strength, and the long cycle life, high-rate performance, and high-temperature storage stability of the final battery. It is noteworthy that compared to the binary composite system also containing ionic liquid (Comparative Example 2, without the addition of inorganic ceramic filler), the ternary composite interface layer of this invention still exhibits significant advantages in core properties such as ionic conductivity, thermal dimensional stability (180℃ thermal shrinkage rate), and interfacial peel strength. This comparative result strongly demonstrates that the "heat-resistant polymer-ionic liquid-inorganic ceramic filler" ternary synergistic system constructed in this invention is a necessary condition for achieving the aforementioned superior comprehensive performance, and its effect is not a simple superposition of the functions of each component.

[0070] This invention innovates from the fundamental material system to successfully construct a functionally integrated composite interface layer. It fundamentally solves the industry pain points of high battery interface impedance and high-temperature safety risks caused by the low ionic conductivity and poor heat resistance of traditional adhesive layers, and has a very wide range of application prospects.

[0071] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A ternary composite interface layer, characterized in that, The components include the following parts by mass: 5-20 parts of polymeric binder, 10-30 parts of ionic liquid plasticizer, and 1-10 parts of inorganic ceramic filler; The glass transition temperature T of the polymer binder g ≥200℃; The ionic liquid plasticizer is obtained by mixing lithium salt and ionic liquid; The molar concentration of lithium salt in the ionic liquid plasticizer is 0.1~5.0 mol / L.

2. The ternary composite interface layer according to claim 1, characterized in that, The polymeric binder includes one or more of nitrogen-containing heterocyclic polymers, polyarylene ether resins, fluoropolymers, heat-resistant modified epoxy resins, and heat-resistant phenolic resins. The nitrogen-containing heterocyclic polymers include one or more of polyimides, polyamide-imides, and polyether-imides; The polyarylene ether resin includes one or more of polyetheretherketone, polyphenylene sulfide and polyethersulfone; The fluoropolymer includes polytetrafluoroethylene and / or tetrafluoroethylene-hexafluoropropylene copolymer; The heat-resistant modified epoxy resin includes one or more of the following: epoxy resin cured with aromatic amine curing agents, epoxy resin cured with acid anhydride curing agents, and epoxy resin cured with a multifunctional epoxy resin system. The heat-resistant phenolic resin includes one or more of nitrile rubber modified phenolic resin, epoxy modified phenolic resin, and organosilicon modified phenolic resin.

3. The ternary composite interface layer according to claim 2, characterized in that, The lithium salt includes one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium hexafluorophosphate, and lithium perchlorate; The ionic liquid includes imidazole ionic liquids and / or pyrrolidine ionic liquids; The imidazole ionic liquids include one or more of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, and 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt; The pyrrolidine ionic liquids include one or more of 1-methyl-1-propylpyrrolidine bis(trifluoromethanesulfonyl)imide salt, N-methyl-N-butylpyrrolidine bis(trifluoromethanesulfonyl)imide salt, and N-methyl-N-propylpyrrolidine bis(fluorosulfonyl)imide salt.

4. A ternary composite interface layer according to any one of claims 1 to 3, characterized in that, The particle size D of the inorganic ceramic filler 50 The wavelength is 20~100 nm. The inorganic ceramic filler includes nano-oxides and / or fast ion conductors; The nano-oxides include nano-alumina and / or nano-silica; The fast ion conductor includes one or more of lithium lanthanum zirconium oxide, lithium lanthanum titanium oxide, and lithium titanium aluminum phosphate.

5. A method for preparing a ternary composite interface layer according to any one of claims 1 to 4, characterized in that, Includes the following steps: 1) Mix polymer binder, ionic liquid plasticizer, inorganic ceramic filler and organic solvent to obtain slurry; 2) Coat the surface of the positive electrode with the slurry and dry it to form a ternary composite interface layer.

6. The method for preparing a ternary composite interface layer according to claim 5, characterized in that, The organic solvent mentioned in step 1) includes one or more of N-methylpyrrolidone, N,N-dimethylformamide and N,N-dimethylacetamide; The solid content of the slurry is 15~60 wt%.

7. The method for preparing a ternary composite interface layer according to claim 6, characterized in that, The drying temperature in step 2) is 60~100℃, and the time is 5~30 min; The thickness of the ternary composite interface layer is 1~20 μm.

8. A composite electrode, characterized in that, It includes the positive electrode, the separator, and the ternary composite interface layer located between the two; The ternary composite interface layer is the ternary composite interface layer according to any one of claims 1 to 4.

9. The method for preparing the composite electrode according to claim 8, characterized in that, Includes the following steps: A composite electrode is obtained by sequentially hot-pressing and heat-curing a positive electrode coated with a ternary composite interface layer and a separator. The ternary composite interface layer is a ternary composite interface layer as described in any one of claims 1 to 4.

10. The method for preparing the composite electrode according to claim 9, characterized in that, The hot-pressing composite process is carried out at a temperature of 120~160℃, a pressure of 0.3~1.0 MPa, and a time of 5 s~10 min. The heat treatment curing temperature is 160~200℃, and the time is 1~4 h.

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