Cage siloxane-based semi-interpenetrating network copolymers, binders, preparation and use

Abstract

This invention relates to a semi-interpenetrating network copolymer based on cage-like silsesquioxanes, an adhesive, its preparation, and its application. The semi-interpenetrating network copolymer is formed by polymerization of cage-like polyhedral oligomeric silsesquioxanes, a boron-substituted polyether matrix, and a fluorinated matrix. The boron-substituted polyether matrix is ​​obtained by transesterification of dihydroxy compounds, alkoxy boron compounds, and (meth)acrylate compounds containing polyether branches. This invention fully utilizes the nanoscale effect and cross-linking effect of cage-like polyhedral oligomeric silsesquioxanes, combined with the flexibility and ion conductivity of polyether segments and the high-voltage resistance of the fluorinated matrix, giving the semi-interpenetrating network copolymer excellent bonding strength, mechanical toughness, interfacial stability, and ion conductivity. Applying the semi-interpenetrating network copolymer of this invention to batteries can significantly improve the cycle stability and rate performance of batteries.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, and in particular to a semi-interpenetrating network copolymer based on cage-like siloxane, a binder, its preparation and application. Background Technology

[0002] Binders are an indispensable component in composite electrodes. Although they account for a small percentage by mass, they play a crucial role in constructing a stable electrode structure. The main functions of binders include: tightly connecting active material particles to the conductive carbon network, maintaining the mechanical integrity of the electrode during charging and discharging, and buffering volume changes in the active material caused by ion insertion / extraction.

[0003] Currently, polyvinylidene fluoride (PVDF) is the most widely used commercial binder. PVDF possesses excellent electrochemical stability, a wide electrochemical window, and good oxidation resistance, enabling it to withstand the operating environment of high-voltage cathode materials. However, PVDF has several significant technical drawbacks in practical applications.

[0004] (1) Insufficient bonding strength: The PVDF molecular chain is mainly composed of inactive carbon-fluorine (CF) bonds, lacking polar groups that can form strong chemical bonds or hydrogen bonds with the surface of active material particles. Its bonding ability to electrode powder mainly relies on weak van der Waals forces, resulting in inherently insufficient bonding strength. During long-term cycling, especially when high-specific-capacity materials undergo drastic volume changes, the PVDF binder is prone to peeling and debonding, leading to the fragmentation of active particles, loss of electrical connection with the current collector, and ultimately, rapid capacity decay of the battery.

[0005] (2) Ion insulation problem: PVDF is essentially an ion insulating material and cannot conduct lithium ions. Ion transport inside the electrode is mainly achieved by the liquid electrolyte permeating the pores. When the electrode is compacted or an ultra-high areal capacity design is adopted, PVDF will occupy part of the volume and block the ion channels, resulting in an increase in the tortuosity of the ion transport path, which significantly limits the rate performance of the battery at high current densities.

[0006] Therefore, there is an urgent need to develop novel binders that combine high bonding strength, good flexibility, excellent ionic conductivity, and strong interfacial interaction with active materials / electrolytes. This is of great scientific significance and application value for improving the long-term cycle life and rate performance of high-energy-density batteries. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing technologies by providing a semi-interpenetrating network copolymer based on cage-like siloxanes, an adhesive, its preparation, and its application. This invention aims to solve the problems of existing adhesives such as polyvinylidene fluoride (PVDF) having insufficient bonding strength, difficulty in adapting to electrode materials with high volume changes, inability to conduct lithium ions thus limiting ion transport efficiency, and difficulty in simultaneously meeting the comprehensive performance requirements of high bonding strength, high ionic conductivity, good flexibility, and wide electrochemical window.

[0008] To achieve the above objectives, in a first aspect, the present invention provides a semi-interpenetrating network copolymer based on cage-like siloxanes, wherein the semi-interpenetrating network copolymer is formed by polymerization of cage-like polyhedral oligomeric silsesquioxanes, boronized polyether matrix and fluorinated matrix.

[0009] The general structural formula of the cage-like polyhedral oligomeric silsesquioxane is (RSiO 3 / 2 ) n , where n is 6, 8, 10 or 12, and R is an organic functional group participating in the polymerization reaction.

[0010] The boron-containing polyether matrix is ​​formed by transesterification of a dihydroxy compound, an alkoxyboron compound, and a polyether-branched (meth)acrylate compound; the polyether-branched (meth)acrylate compound includes: polyether-branched acrylate compounds and their derivatives, and polyether-branched methacrylate compounds and their derivatives. The fluorinated matrix includes one or more of the following: fluorinated vinyl monomers, fluorinated styrene monomers, fluorinated acrylate monomers, or fluorinated methacrylate monomers.

[0011] Preferably, R includes one or more organic functional groups selected from vinyl, epoxy, amino, hydroxy, or methacryloyloxy.

[0012] Preferably, the dihydroxy compound includes one or more of the following: ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,5-dimethylhexane-2,5-diol, hydroquinone, bisphenol A, cyclopentanediol, or cyclohexanediol.

[0013] The alkoxy boron compounds include one or more of the following: trimethyl borate, triethyl borate, tripropyl borate, tributyl borate, triethanolamine borate, triphenyl borate, trimethoxyboronium, or triisopropoxyboronium.

[0014] The acrylate compounds and their derivatives containing polyether branches include one or more of the following: polyethylene glycol acrylate, polypropylene glycol acrylate, polyethylene glycol methyl ether acrylate, polypropylene glycol methyl ether acrylate, polyethylene glycol diacrylate, and polypropylene glycol diacrylate. The polyether-branched methacrylate compounds and their derivatives include one or more of polyethylene glycol methacrylate, polypropylene glycol methacrylate, polyethylene glycol methyl ether methacrylate, polypropylene glycol methyl ether methacrylate, polyethylene glycol dimethacrylate, and polypropylene glycol dimethacrylate.

[0015] Preferably, the fluorinated vinyl monomers include tetrafluoroethylene or trans-1,3,3,3-tetrafluoropropylene; the fluorinated styrene monomers include one or more of 2-fluorostyrene, 3-fluorostyrene, or 4-fluorostyrene; and the fluorinated methacrylate monomers include one or more of 2,2,2-trifluoroethyl methacrylate, pentafluoropropyl methacrylate, nonafluoropentyl methacrylate, methyl 2-trifluoromethacrylate, or tert-butyl 2-trifluoromethacrylate.

[0016] In a second aspect, the present invention provides a method for preparing the semi-interpenetrating network copolymer described in the first aspect, the method comprising:

[0017] A dihydroxy compound, an alkoxy boron compound, and a (meth)acrylate compound containing polyether branches were subjected to transesterification in an organic solvent. After the reaction was completed, the mixture was purified by post-treatment to obtain a boron-substituted polyether matrix.

[0018] The boron-substituted polyether matrix, cage-like polyhedral oligomeric silsesquioxane, and fluorine-containing matrix are mixed in proportion, an initiator is added, and a polymerization reaction is carried out under an inert atmosphere to obtain a semi-interpenetrating network copolymer based on cage-like siloxane.

[0019] Preferably, the mass ratio of the dihydroxy compound, the alkoxyboron compound, and the polyether-branched (meth)acrylate compound is 1:0.5 to 2:1 to 5.

[0020] The organic solvent includes one or more of acetonitrile, toluene, tetrahydrofuran, dichloromethane, N,N-dimethylformamide, or dimethyl sulfoxide.

[0021] Preferably, the mass ratio of the boronized polyether matrix, the cage-like polyhedral oligomeric silsesquioxane, and the fluorinated matrix is ​​1-20:0.5-10:1-30.

[0022] The initiator includes one or more of the following: azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, di-tert-butyl peroxide, tert-butyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxide, and potassium persulfate.

[0023] The heating temperature is 50℃~120℃.

[0024] The polymerization reaction includes one or more of the following: living anionic polymerization, cationic polymerization, ligand polymerization, ring-opening polymerization, free radical polymerization, in-situ polymerization, or click chemical reaction polymerization.

[0025] Thirdly, the present invention provides a composite adhesive comprising the semi-interpenetrating network copolymer described in the first aspect above and other adhesives.

[0026] Preferably, the other adhesives include one or more of the following: polyvinylidene fluoride (PVDF), polyacrylic acid (PAA), polymethyl methacrylate (PMMA), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC-Na), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), fluorinated ethylene-propylene copolymer (FEP), perfluorosulfonic acid resin, ethyl polyacrylate, butyl polyacrylate, hydroxyethyl polymethacrylate, polycyanoacrylate, polyethylene glycol, polyethylene oxide, polypropylene glycol, polylactic acid, polycaprolactone, polyethylene terephthalate, sodium alginate, chitosan, cyclodextrin, epoxy resin, phenolic resin, polyurethane, polyvinyl alcohol, polyvinylpyrrolidone, poly(3,4-ethylenedioxythiophene), polystyrene sulfonic acid, polyaniline, or polypyrrole. The other adhesives constitute a percentage of the total mass of the composite adhesive that is greater than 0% and less than or equal to 70%.

[0027] Fourthly, the present invention provides a battery comprising the composite binder described in the third aspect above.

[0028] The present invention provides a semi-interpenetrating network copolymer based on cage-like siloxane, an adhesive, its preparation and application, which has the following technical effects.

[0029] (1) The semi-interpenetrating network copolymer based on cage-like siloxane provided by the present invention is formed by polymerization reaction of cage-like polyhedral oligomeric silsesquioxane, boron-substituted polyether matrix and fluorine-containing matrix. In this invention, the cage-like polyhedral oligomeric silsesquioxane forms rigid three-dimensional network nodes in the semi-interpenetrating network copolymer through its nano-size effect and cross-linking effect, which significantly enhances the cohesive strength and peel resistance of the copolymer, giving the semi-interpenetrating network copolymer strong mechanical toughness. The polyether segments in the boron-substituted polyether matrix provide good flexibility, giving the copolymer both high bonding strength and elasticity, which can effectively buffer the volume change of electrode active material during charging and discharging, prevent electrode cracking and active material shedding. In addition, the boron atoms in the boron-substituted polyether matrix act as Lewis acid sites can coordinate / decoordinate with lithium ions, and in conjunction with the chain movement of ether oxygen segments, a continuous ion transport channel is constructed within the binder, enabling the copolymer itself to possess lithium-ion conductivity and overcoming the ion insulation defects of traditional PVDF and other binders. The fluorine-containing matrix gives the semi-interpenetrating network copolymer excellent oxidation resistance and high-voltage stability, which can match the working environment of high-voltage cathode materials, thereby suppressing the decomposition side reactions of the electrolyte under high voltage. The rigid cage structure and low surface energy characteristics of the fluorine-containing segments of the semi-interpenetrating network copolymer of this invention give the copolymer a high thermal decomposition temperature and good electrolyte wetting stability, which can form a stable interface layer at the electrode / electrolyte interface and reduce interfacial impedance.

[0030] (2) The preparation method of the semi-interpenetrating network copolymer provided by the present invention first synthesizes a boron-substituted polyether matrix by transesterification reaction, and then copolymerizes it with cage-type polyhedral oligomeric silsesquioxane and fluorine-containing matrix. The polymerization reaction can adopt various polymerization methods such as anionic, cationic, and free radical polymerization to adapt to different monomer combinations and application requirements. By adjusting the mass ratio of boron-substituted polyether matrix, cage-type polyhedral oligomeric silsesquioxane and fluorine-containing matrix, as well as the reaction temperature and the type of initiator, the crosslinking density, ionic conductivity, flexibility and high voltage resistance of the copolymer can be controlled to meet the requirements of different electrode systems.

[0031] (3) The composite binder provided by the present invention combines semi-interpenetrating network copolymers with traditional binders in a certain proportion, which can complement each other's strengths. For example, blending with PVDF can maintain certain processing compatibility and introduce ion conduction function at the same time; blending with water-based binders (such as styrene-butadiene rubber and sodium carboxymethyl cellulose) can improve the flexibility and ionic conductivity of the electrode sheet; the composite binder can flexibly select the type and proportion of other binders according to the different requirements of the active material, thereby achieving comprehensive optimization of adhesion, flexibility, ionic conductivity and electrochemical stability.

[0032] (4) The composite binder provided by the present invention is used to prepare positive electrode sheets or negative electrode sheets. In the liquid electrolyte system, the electrode structure has good integrity, stable interface, fast lithium ion diffusion rate, and excellent rate performance. In solid-state batteries, since the semi-interpenetrating network copolymer itself has good ionic conductivity and interfacial compatibility with solid electrolyte, the composite binder can construct an effective ion permeation network and significantly reduce the charge transfer impedance in solid-state batteries.

[0033] Because the fluorine-containing matrix imparts a high antioxidant decomposition potential to the composite binder, the battery can still cycle stably under high voltage. The synergistic effect of the flexibility of the boron-substituted polyether segments and the toughness of the cage-like polyhedral oligomeric silsesquioxane crosslinking network makes the electrode less prone to powdering and cracking during coating, drying, rolling and cutting, thus improving the yield of electrode manufacturing. Attached Figure Description

[0034] Figure 1 This is a flowchart of the preparation method of the semi-interpenetrating network copolymer based on cage-type siloxane provided in Example 1 of the present invention.

[0035] Figure 2 Fourier transform infrared spectrum of boronized polyether matrix B-PEGMA containing cyclic borate ester groups and ether oxygen units provided in Example 1 of the present invention.

[0036] Figure 3 The 1H NMR spectrum of the boronized polyether matrix B-PEGMA containing cyclic borate ester groups and ether oxygen units provided in Example 1 of the present invention. Figure 4 The Fourier transform infrared spectrum of POSS-g-TFEMA / B-PEGMA, a semi-interpenetrating network copolymer based on cage-like siloxane, provided in Example 1 of this invention.

[0037] Figure 5 The 1H NMR spectrum of POSS-g-TFEMA / B-PEGMA, a semi-interpenetrating network copolymer based on cage-like siloxanes, provided in Example 1 of this invention.

[0038] Figure 6 The image shows a differential scanning calorimeter (DSC) test result of the semi-interpenetrating network copolymer POSS-g-TFEMA / B-PEGMA based on cage-like siloxanes provided in Example 1 of this invention.

[0039] Figure 7 Thermogravimetric analysis (TGA) diagram of POSS-g-TFEMA / B-PEGMA, a semi-interpenetrating network copolymer based on cage-like siloxane, provided in Example 1 of this invention.

[0040] Figure 8Fourier transform infrared spectra of the PVDF-OTB film prepared by the semi-interpenetrating network copolymer POSS-g-TFEMA / B-PEGMA based on cage-type siloxane provided in Example 1 of the present invention and the PVDF film prepared by the conventional binder PVDF in Comparative Example 1.

[0041] Figure 9 The thermal deformation tests were performed on the PVDF-OTB film prepared by the semi-interpenetrating network copolymer POSS-g-TFEMA / B-PEGMA based on cage-type siloxane provided in Example 1 of the present invention and the PVDF film prepared by the conventional binder PVDF in Comparative Example 1.

[0042] Figure 10 The images show scanning electron microscope (SEM) images and energy dispersive spectroscopy (EDS) test results of the PVDF-OTB film prepared from the semi-interpenetrating network copolymer POSS-g-TFEMA / B-PEGMA based on cage-like siloxanes provided in Example 1 of this invention.

[0043] Figure 11 The images show SEM and EDS results of the LCO-PVDF / OTB electrode prepared from the semi-interpenetrating network copolymer POSS-g-TFEMA / B-PEGMA based on cage-like siloxanes provided in Example 1 of this invention.

[0044] Figure 12 The resistivity of the LCO-PVDF / OTB electrode prepared by POSS-g-TFEMA / B-PEGMA based on cage-type siloxane in Example 1 of the present invention and the LCO-PVDF electrode prepared by conventional binder in Comparative Example 1 were measured.

[0045] Figure 13 The swelling rate of the LCO-PVDF / OTB electrode prepared by POSS-g-TFEMA / B-PEGMA based on cage-type siloxane in Example 1 of this invention and the LCO-PVDF electrode prepared by conventional binder in Comparative Example 1 were tested.

[0046] Figure 14 Cyclic voltammetry curves of the LCO-PVDF / OTB electrode assembly liquid battery prepared based on the cage-like siloxane semi-interpenetrating network copolymer POSS-g-TFEMA / B-PEGMA provided in Example 1 of the present invention were tested at different scan rates.

[0047] Figure 15The peak current and linear fitting curves of the square root of the scan rate are obtained from the cyclic voltammetry curves of the liquid battery assembled from the LCO-PVDF / OTB electrode prepared by the semi-interpenetrating network copolymer POSS-g-TFEMA / B-PEGMA based on cage-type siloxane provided in Example 1 of the present invention and the LCO-PVDF electrode prepared by the conventional binder PVDF in Comparative Example 1, which are tested at different scan rates.

[0048] Figure 16 The galvanostatic intermittent titration (GITT) curves of the LCO-PVDF / OTB electrode assembly liquid battery prepared based on the cage-like siloxane semi-interpenetrating network copolymer POSS-g-TFEMA / B-PEGMA provided in Example 1 of the present invention.

[0049] Figure 17 The diffusion coefficient of lithium ions during charging of the LCO-PVDF / OTB electrode prepared by the semi-interpenetrating network copolymer POSS-g-TFEMA / B-PEGMA based on cage-type siloxane provided in Example 1 of the present invention and the LCO-PVDF electrode prepared by the conventional binder PVDF based on Comparative Example 1 are shown.

[0050] Figure 18 The diffusion coefficient of lithium ions during discharge is measured in the LCO-PVDF / OTB electrode prepared by the semi-interpenetrating network copolymer POSS-g-TFEMA / B-PEGMA based on cage-type siloxane provided in Example 1 of the present invention and the LCO-PVDF electrode prepared by the conventional binder PVDF based in Comparative Example 1.

[0051] Figure 19 Rate testing of LCO-PVDF / OTB electrode prepared based on cage-type siloxane semi-interpenetrating network copolymer POSS-g-TFEMA / B-PEGMA in liquid battery, as provided in Example 1 of this invention.

[0052] Figure 20 The LCO-PVDF / OTB electrode prepared by POSS-g-TFEMA / B-PEGMA based on cage-type siloxane semi-interpenetrating network copolymer provided in Example 1 of the present invention and the LCO-PVDF prepared by Comparative Example 1 based on conventional binder PVDF were subjected to long-cycle testing in liquid batteries.

[0053] Figure 21 SEM and EDS tests were performed on the PVDF film prepared based on the conventional binder PVDF for Comparative Example 1.

[0054] Figure 22 SEM and EDS tests were performed on the LCO-PVDF electrode prepared based on the conventional binder PVDF for Comparative Example 1.

[0055] Figure 23 Cyclic voltammetry curves of liquid batteries assembled from LCO-PVDF electrodes prepared based on conventional binder PVDF, as shown in Comparative Example 1.

[0056] Figure 24 GITT test of the liquid battery assembled from LCO-PVDF electrodes prepared based on conventional binder PVDF, for Comparative Example 1. Detailed Implementation

[0057] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0058] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0059] This invention provides a semi-interpenetrating network copolymer based on cage-like siloxanes, which is formed by polymerization of cage-like polyhedral oligomeric silsesquioxanes, boronized polyether matrix and fluorinated matrix.

[0060] Specifically, cage-like polyhedral oligomeric silsesquioxanes form nanoscale cross-linked network structures; the general structural formula of cage-like polyhedral oligomeric silsesquioxanes is (RSiO 3 / 2 ) n Where n is any degree of polymerization of 6, 8, 10 or 12, and R is an organic functional group participating in the polymerization reaction, including one or more organic functional groups selected from vinyl, epoxy, amino, hydroxy or methacryloyloxy.

[0061] Boron-substituted polyethers contain polyether segments with ion-conducting capabilities. The boron-substituted polyether matrix is ​​formed by transesterification of dihydroxy compounds, alkoxyboron compounds, and polyether-branched (meth)acrylate compounds; the polyether-branched (meth)acrylate compounds include, but are not limited to, one or more of polyether-branched acrylate compounds and their derivatives, and polyether-branched methacrylate compounds and their derivatives.

[0062] The dihydroxy compounds include one or more of the following: ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,5-dimethylhexane-2,5-diol, hydroquinone, bisphenol A, cyclopentanediol, or cyclohexanediol.

[0063] Alkoxy boron compounds include one or more of the following: trimethyl borate, triethyl borate, tripropyl borate, tributyl borate, triethanolamine borate, triphenyl borate, trimethoxyboronium, or triisopropoxyboronium.

[0064] Acrylic ester compounds containing polyether branches and their derivatives include, but are not limited to, one or more of the following: polyethylene glycol acrylate, polypropylene glycol acrylate, polyethylene glycol methyl ether acrylate, polypropylene glycol methyl ether acrylate, polyethylene glycol diacrylate, and polypropylene glycol diacrylate; methacrylate compounds containing polyether branches and their derivatives include, but are not limited to, one or more of the following: polyethylene glycol methacrylate, polypropylene glycol methacrylate, polyethylene glycol methyl ether methacrylate, polypropylene glycol methyl ether methacrylate, polyethylene glycol dimethacrylate, and polypropylene glycol dimethacrylate. The basic structural formula of (meth)acrylate compounds containing polyether branches is as follows: .

[0065] Fluorine-containing matrices have high pressure resistance; fluorine-containing matrices contain copolymerizable functional groups, including one or more of the following: fluorinated vinyl monomers, fluorinated styrene monomers, fluorinated acrylate monomers, or fluorinated methacrylate monomers.

[0066] Fluorinated vinyl monomers include tetrafluoroethylene or trans-1,3,3,3-tetrafluoropropylene; fluorinated styrene monomers include one or more of 2-fluorostyrene, 3-fluorostyrene, or 4-fluorostyrene; fluorinated methacrylate monomers include one or more of 2,2,2-trifluoroethyl methacrylate, pentafluoropropyl methacrylate, nonafluoropentyl methacrylate, methyl 2-trifluoromethacrylate, or tert-butyl 2-trifluoromethacrylate.

[0067] The basic structural formulas of fluorinated vinyl monomers are as follows: .

[0068] This invention provides a method for preparing the above-mentioned semi-interpenetrating network copolymer, such as... Figure 1 As shown, it includes the following steps.

[0069] Step 110: The dihydroxy compound, the alkoxy boron compound, and the (meth)acrylate compound containing polyether branches are subjected to transesterification reaction in an organic solvent. After the reaction is completed, the mixture is purified by post-treatment to obtain the boron-substituted polyether matrix.

[0070] Specifically, a dihydroxy compound and an alkoxyboron compound are mixed in an organic solvent and stirred at 65°C under an inert gas atmosphere for 0.5 to 5 hours. Then, a (meth)acrylate compound containing polyether branches is added and the reaction continues for 2 to 6 hours to carry out an ester exchange reaction. After the reaction is completed, post-treatment purification is performed: the organic solvent is removed by vacuum distillation, the residue is dissolved in toluene, the insoluble matter is removed by filtration, the toluene is removed by rotary evaporation, and finally, the product is dried under vacuum at room temperature for 12 to 36 hours to obtain the boron-substituted polyether matrix.

[0071] The mass ratio of dihydroxy compounds, alkoxyboron compounds and (meth)acrylate compounds containing polyether branches is 1:0.5 to 2:1 to 5.

[0072] The dihydroxy compounds include one or more of the following: ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,5-dimethylhexane-2,5-diol, hydroquinone, bisphenol A, cyclopentanediol, or cyclohexanediol.

[0073] Alkoxy boron compounds include one or more of the following: trimethyl borate, triethyl borate, tripropyl borate, tributyl borate, triethanolamine borate, triphenyl borate, trimethoxyboronium, or triisopropoxyboronium.

[0074] Acrylic ester compounds containing polyether branches and their derivatives include, but are not limited to, one or more of the following: polyethylene glycol acrylate, polypropylene glycol acrylate, polyethylene glycol methyl ether acrylate, polypropylene glycol methyl ether acrylate, polyethylene glycol diacrylate, and polypropylene glycol diacrylate; methacrylate compounds containing polyether branches and their derivatives include, but are not limited to, one or more of the following: polyethylene glycol methacrylate, polypropylene glycol methacrylate, polyethylene glycol methyl ether methacrylate, polypropylene glycol methyl ether methacrylate, polyethylene glycol dimethacrylate, and polypropylene glycol dimethacrylate.

[0075] Organic solvents include one or more of acetonitrile, toluene, tetrahydrofuran, dichloromethane, N,N-dimethylformamide, or dimethyl sulfoxide. The amount of organic solvent used is 2 to 20 times the total mass of the reactants.

[0076] Step 120: The boron-substituted polyether matrix, cage-type polyhedral oligomeric silsesquioxane, and fluorine-containing matrix are mixed in proportion, an initiator is added, and the polymerization reaction is carried out under an inert atmosphere to obtain a semi-interpenetrating network copolymer based on cage-type siloxane.

[0077] The mass ratio of boronized polyether matrix, cage-type polyhedral oligomeric silsesquioxane, and fluorinated matrix is ​​1–20:0.5–10:1–30.

[0078] The fluorinated matrix includes one or more of the following: fluorinated vinyl monomers, fluorinated styrene monomers, fluorinated acrylate monomers, or fluorinated methacrylate monomers. Specifically, fluorinated vinyl monomers include tetrafluoroethylene or trans-1,3,3,3-tetrafluoropropylene; fluorinated styrene monomers include one or more of 2-fluorostyrene, 3-fluorostyrene, or 4-fluorostyrene; and fluorinated methacrylate monomers include one or more of 2,2,2-trifluoroethyl methacrylate, pentafluoropropyl methacrylate, nonafluoropentyl methacrylate, methyl 2-trifluoromethacrylate, or tert-butyl 2-trifluoromethacrylate.

[0079] The initiators include one or more of the following: azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, di-tert-butyl peroxide, tert-butyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxide, and potassium persulfate. The amount of initiator added is 0.1% to 1% of the total mass of the boron-substituted polyether matrix, cage-like polyhedral oligomeric silsesquioxane, and fluorinated matrix. It can be any value within this range, such as 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, etc., but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0080] The heating temperature is 50℃~120℃, and can be any temperature within this range, such as 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 120℃, etc., but is not limited to the listed temperatures. Other unlisted temperatures within this range are also applicable.

[0081] Polymerization reactions include one or more of the following: living anionic polymerization, cationic polymerization, ligand polymerization, ring-opening polymerization, free radical polymerization, in-situ polymerization, or click chemical reaction polymerization.

[0082] The semi-interpenetrating network copolymer provided in this invention can be mixed with other binders and solvents to obtain a composite binder. This liquid or slurry-like composite binder can be directly used in the preparation of positive or negative electrode sheets.

[0083] The percentage of other binders in the total mass of the composite binder is greater than 0% and less than or equal to 70%, and can be any value within this range, such as: 0.5%, 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, etc., but is not limited to the listed values; other unlisted values ​​within this range are also applicable. The percentage of other binders in the total mass of the composite binder is preferably 33% to 70%. Composite binders within this range can simultaneously possess low swelling ratio, high ionic conductivity, and good electrode processability.

[0084] Other binders include: polyvinylidene fluoride (PVDF), polyacrylic acid (PAA), polymethyl methacrylate (PMMA), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC-Na), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), fluorinated ethylene-propylene copolymer (FEP), perfluorosulfonic acid resin, ethyl polyacrylate, butyl polyacrylate, hydroxyethyl polymethacrylate, cyanoacrylate, polyethylene glycol, polyethylene oxide, polypropylene glycol, polylactic acid, polycaprolactone, polyethylene terephthalate, sodium alginate, chitosan, cyclodextrin, epoxy resin, phenolic resin, polyurethane, polyvinyl alcohol, polyvinylpyrrolidone, poly(3,4-ethylenedioxythiophene), polystyrene sulfonic acid, polyaniline, or one or more of polypyrrole.

[0085] Solvents include one or more of the following: deionized water, dichloromethane, dichlorobenzene, xylene, dimethyl sulfoxide, chloroform, tetrahydrofuran, toluenecyclohexanone, methanol, toluene, ethanol, acetonitrile, ethyl acetate, diethyl ether, acetone, n-hexane, cyclohexane, cyclohexanone, n-heptane, hexafluoroisopropanol, N-methylpyrrolidone, N,N-dimethylformamide, benzene, chlorophenol, 1,4-dioxane, pyridine, and petroleum ether.

[0086] The composite binder provided in this invention can be prepared into a thin film. The preparation process is as follows: a semi-interpenetrating network copolymer and other binders are mixed in a certain proportion, and a certain amount of solvent is added to form a mixture solution. This solution is then poured into a custom-made grooved Teflon mold, left to stand at room temperature for 12 to 24 hours, and then transferred to a vacuum drying oven at 90°C to 120°C for 12 to 24 hours to remove excess solvent, resulting in a thin film of the composite binder. This demonstrates that the composite binder provided in this invention, under the stated composition and proportions, can form a self-supporting thin film after solution casting and solvent evaporation, facilitating direct use in electrode preparation or further processing. The crosslinking nodes of the cage-like polyhedral oligomeric silsesquioxane and the flexibility of the polyether segments in the semi-interpenetrating network copolymer structure provided by this invention jointly provide the mechanical integrity of the film, preventing it from becoming brittle or excessively soft and unable to detach from the mold.

[0087] The composite binder provided in this embodiment of the invention can be mixed with positive or negative active materials to prepare positive or negative electrode sheets.

[0088] Positive electrode active materials include, but are not limited to, one or more of the following: lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, nickel-cobalt-manganese ternary materials, nickel-cobalt-aluminum ternary materials, Prussian blue analogues, or polyanionic compounds.

[0089] The negative electrode active materials include, but are not limited to, one or more of the following: artificial graphite, natural graphite, mesophase carbon microspheres, soft carbon, hard carbon, carbon nanotubes, graphene, silicon-carbon composite materials, and tin-based oxides.

[0090] The positive or negative electrode sheet containing a semi-interpenetrating network copolymer provided in this invention can be used to assemble batteries, including lithium-ion batteries or sodium-ion batteries. The lithium-ion batteries include liquid lithium-ion batteries, semi-solid lithium-ion batteries, or all-solid lithium-ion batteries, and the sodium-ion batteries include liquid sodium-ion batteries, semi-solid sodium-ion batteries, or all-solid sodium-ion batteries.

[0091] For example, a composite binder solution obtained by mixing a semi-interpenetrating network copolymer with other binders, conductive agents and solvents can be mixed evenly with a positive electrode active material, and then coated, cut and vacuum dried in a conventional manner to obtain the desired positive electrode sheet, which can then be used to assemble a battery.

[0092] Because the composite binder provided by this invention has good comprehensive properties of adhesion, flexibility, ionic conductivity and electrochemical stability, it not only makes the electrode less prone to powdering and cracking during coating, drying, rolling and cutting, thus improving the yield of electrode manufacturing, but also significantly improves the cycle stability and rate performance of the battery.

[0093] The batteries containing semi-interpenetrating network copolymers provided in the embodiments of the present invention can be applied to electric vehicles, hybrid electric vehicles, electric bicycles, energy storage power stations, portable electronic devices, mobile power supplies, drones, power tools, wearable devices, medical electronic devices, aerospace vehicles, marine power systems, or grid frequency regulation energy storage systems.

[0094] To better understand the technical solutions provided by this invention, the following examples illustrate the preparation process and application of the semi-interpenetrating network copolymer and composite adhesive based on cage-like siloxanes.

[0095] Example 1 This embodiment provides a preparation process for a semi-interpenetrating network copolymer based on cage-type siloxanes, the specific process of which is as follows.

[0096] (1) Synthesis of boronized polyether matrix B-PEGMA containing cyclic borate ester groups and ether oxygen units.

[0097] Weigh 1.0 g of 2,5-dimethylhexane-2,5-diol and 0.9 ml of trimethyl borate, dissolve them in 50 ml of anhydrous acetonitrile, place the solution in a 100 ml three-necked flask, set the oil bath temperature to 65 °C, and stir for 1 hour under an inert argon atmosphere. Then, add 2.4 g of polyethylene glycol methacrylate (PEGMA) to the three-necked flask and continue stirring for 3 hours. After the reaction is complete, collect the reaction solution and remove residual acetonitrile by vacuum distillation at room temperature. Dissolve the obtained product in toluene, remove insoluble impurities by filtration, remove the residual toluene solution by rotary evaporation, and finally dry the solid product under vacuum at room temperature for 24 hours to synthesize a boronized polyether matrix containing cyclic borate ester groups and ether oxygen units, abbreviated as B-PEGMA. In this step, cyclic borate ester groups are introduced into the polyether side chains through transesterification, giving the product ionic conductivity, while retaining the polymerizable methacrylate double bonds for subsequent copolymerization.

[0098] The synthesis scheme of boron-substituted polyether matrix B-PEGMA in this embodiment is as follows: .

[0099] The prepared boron-substituted polyether matrix B-PEGMA was characterized as follows.

[0100] The shift of characteristic peaks in the Fourier transform infrared spectrum preliminarily confirms the presence of the boron-substituted polyether matrix B-PEGMA (see appendix). Figure 2 Fourier transform infrared spectroscopy shows that at 2868 cm⁻¹ -1 The peak represents the stretching vibration characteristic of saturated CH bonds, corresponding to an alkyl structure; 1717 cm⁻¹ -1 Attributable to the carbonyl C=O stretching vibration, 1636 cm⁻¹-1 It is the C=C stretching vibration peak of the carbon-carbon double bond, 1102 cm⁻¹. -1 This is the stretching vibration peak of the aliphatic ether bond COC; low wavenumbers 730-659 cm⁻¹ -1 The vibrational peaks in the blue-marked area are characteristic absorption peaks of the BO bond, indicating that the B-containing part has been successfully grafted onto the PEGMA monomer. All characteristic peaks together confirm that the B-PEGMA prepared in this example contains alkyl, carbonyl, carbon-carbon double bonds, ether bonds, and boron-oxygen structures.

[0101] The shifts in the corresponding characteristic peaks in the 1H NMR spectrum further confirm the presence of the boron-substituted polyether matrix B-PEGMA (see appendix). Figure 3 The resonance peaks at chemical shifts of 1.96 ppm (a), 5.59 ppm (b), and 6.14 ppm (c) originate from protons in the PEGMA backbone. The peaks at chemical shifts of 3.66–4.31 ppm (d) originate from protons in the CH2-CH2-O segment of PEGMA. The resonance peaks at 1.26 ppm (e) and 1.59 ppm (f) belong to protons in the alkyl and vinyl groups of the borate ester, indicating that B was successfully grafted onto the PEGMA fragment.

[0102] (2) The semi-interpenetrating network copolymer POSS-g-TFEMA / B-PEGMA based on cage-type siloxane was prepared by free radical polymerization as follows.

[0103] Octapolysilsesquioxane (OV-POSS) (0.6722 g), 2,2,2-trifluoroethyl methacrylate (TFEMA) (1.513 g), and boron-modified polyether matrix B-PEGMA (3.3972 g) containing cyclic borate ester groups and ether oxygen units were placed in a 100 mL three-necked flask. 50 mL of anhydrous acetonitrile was added to dissolve the solids. AIBN (0.5 wt% of the total mass of OV-POSS, TFEMA, and PEGMA) was used as the initiator. The mixture was heated to 70 °C under an argon atmosphere for 12 hours. After the reaction, the mixture was dissolved in tetrahydrofuran solution and precipitated three times in petroleum ether to remove residual monomers. Finally, the collected product was dried under vacuum at 60 °C for 12 hours to obtain a semi-interpenetrating network copolymer, abbreviated as POSS-g-TFEMA / B-PEGMA.

[0104] The synthesis scheme of POSS-g-TFEMA / B-PEGMA in this embodiment is as follows: .

[0105] The prepared semi-interpenetrating network copolymer POSS-g-TFEMA / B-PEGMA was characterized and tested as follows.

[0106] The shift of characteristic peaks in Fourier transform infrared spectroscopy preliminarily confirms the formation of the POSS-g-TFEMA / B-PEGMA semi-interpenetrating network copolymer based on cage-like siloxanes (see appendix). Figure 4 It can be seen that it is 2864 cm. -1 This is the stretching vibration signal of alkyl CH4, 1723 cm. -1 Belongs to carbonyl group, 1603 cm -1 The peak at 1275 cm⁻¹ belongs to a carbon-carbon double bond, which is due to the unreacted vinyl group in the OV-POSS. -1 The characteristic peak of CF confirms the successful copolymerization of TFEMA fluorinated units. Due to the overlap of the Si-O-Si peaks of COC and POSS, at 1108 cm⁻¹... -1 There is a strong absorption peak at 778 cm⁻¹, and in the low wavenumber region... -1 The BO characteristic peaks confirmed the introduction of the boron-oxygen structure. All characteristic absorption peaks corresponded completely to the four major structural units: POSS, trifluoromethacrylate, boron group, and polyethylene glycol methacrylate, confirming the successful preparation of the semi-interpenetrating network copolymer POSS-g-TFEMA / B-PEGMA.

[0107] The shifts in the corresponding characteristic peaks in the 1H NMR spectrum further confirm the formation of the POSS-g-TFEMA / B-PEGMA semi-interpenetrating network copolymer based on cage-like siloxanes (see Appendix). Figure 5 According to the NMR spectrum, the resonance peaks with chemical shifts of 6.12-5.55 ppm in the obtained random copolymer POSS-g-TFEMA / B-PEGMA are attributed to the unreacted vinyl protons in OV-POSS, while the strong resonance peaks at 1.24, 1.56, and 3.44 ppm are attributed to CH2 and the terminal CH3 groups, indicating the successful synthesis of the surface copolymer.

[0108] Differential scanning calorimetry (DSC) tests confirmed that the glass transition temperature of the semi-interpenetrating network copolymer POSS-g-TFEMA / B-PEGMA based on cage-like siloxanes is -4℃. (See attached image) Figure 6 As can be seen in the figure, the glass transition temperature of POSS-g-TFEMA / B-PEGMA is much lower than the conventional operating temperature of the battery, which makes the binder containing the semi-interpenetrating network copolymer prepared in this embodiment exhibit high flexibility and elasticity in the working state, and the molecular chains have a high mobility, which directly endows the binder with excellent flexibility and good ion conduction ability. Thermogravimetric analysis (TGA) demonstrated that the POSS-g-TFEMA / B-PEGMA semi-interpenetrating network copolymer based on cage-like siloxanes exhibits good thermal stability (see attached figure). Figure 7 As can be seen, POSS-g-TFEMA / B-PEGMA exhibits good thermal stability below 300℃; the peak temperature of rapid thermal decomposition of POSS-g-TFEMA / B-PEGMA is 405.6℃, indicating excellent resistance to thermal decomposition. The thermogravimetric analysis (TGA) conditions were as follows: sample mass approximately 5 mg, inert atmosphere nitrogen, scan rate 10℃ / min, and test temperature range room temperature to 800℃.

[0109] (3) Prepare a composite adhesive film PVDF-OTB containing a semi-interpenetrating network copolymer based on cage-type siloxane, as follows.

[0110] The semi-interpenetrating network copolymer (POSS-g-TFEMA / B-PEGMA) based on cage-like siloxane of the present invention and polyvinylidene fluoride (PVDF) were mixed at mass ratios of 1:1 and 1:2, respectively. An appropriate amount of NMP solvent was added, and mixing continued to obtain the binder solution PVDF-OTB (OTB indicates the semi-interpenetrating network copolymer POSS-g-TFEMA / B-PEGMA prepared in this embodiment). This solution was then poured into a custom-made grooved Teflon mold and allowed to stand at room temperature for 12 hours. It was then transferred to a vacuum drying oven at 100°C and heated for 12 hours to remove excess solvent, yielding a PVDF-OTB film. This demonstrates that the composite binder possesses a certain degree of self-supporting ability. The film's performance was then tested.

[0111] Fourier transform infrared spectroscopy (FTIR) of the PVDF-OTB thin film prepared in Example 1 is shown in the appendix. Figure 8 .

[0112] The thermal deformation test of the PVDF-OTB thin film prepared in Example 1 is shown in the appendix. Figure 9 .

[0113] SEM and EDS tests of the PVDF-OTB film prepared in Example 1 are shown in the appendix. Figure 10 ,in, Figure 10 (a) is a SEM image of the PVDF-OTB film. Figure 10 (b, c) are EDS diagrams of PVDF-OTB films. Figure 10 (b) Display element F, Figure 10 (c) Display the Si element.

[0114] The present invention uses a semi-interpenetrating network copolymer based on cage-like siloxane (POSS-g-TFEMA / B-PEGMA) and polyvinylidene fluoride (PVDF) mixed at mass ratios of 1:1 and 1:2, respectively. After adding an appropriate amount of NMP solvent, the mixture is further mixed to obtain the adhesive solution PVDF-OTB.

[0115] Using the PVDF-OTB binder solution prepared in different proportions as described above, lithium cobalt oxide (LCO) positive electrode powder, binder solution, and conductive carbon black were mixed evenly according to a mass ratio of active material: binder solution: conductive agent = 8:1:1. After uniform coating, the mixture was cut and vacuum dried to obtain the desired LCO-PVDF / OTB positive electrode sheet. The performance of this positive electrode sheet was tested as follows.

[0116] SEM and EDS tests of the LCO-PVDF / OTB electrode prepared in Example 1 are shown in the appendix. Figure 11 ,in Figure 11 (a) is a SEM image of the LCO-PVDF / OTB electrode. Figure 11 (b, c) are the EDS diagrams of the LCO-PVDF / OTB electrode, where Figure 11 (b) Display element F, Figure 10 (c) Display the Si element.

[0117] The resistivity test of the LCO-PVDF / OTB electrode prepared in Example 1 is shown in the appendix. Figure 12 .

[0118] The LCO-PVDF / OTB electrode prepared using this embodiment was immersed in electrolyte for 10 days to test the swelling rate of the binder. (See attached figure.) Figure 13 .

[0119] The LCO-PVDF / OTB positive electrode sheet prepared in this embodiment was used to assemble a liquid lithium-ion battery and then tested, as detailed below.

[0120] The assembly process is as follows: A lithium metal sheet, a separator, electrolyte, LCO-PVDF / OTB positive electrode sheet, a stainless steel gasket, and a spring clamping sheet are sequentially placed on the negative electrode shell, ensuring alignment of the center points of each part. Finally, the positive electrode shell is placed in the shell, with the negative electrode of the coin cell facing upwards. Insulated tweezers are used to transfer the battery to a battery packaging machine for sealing, ready for testing. The separator is a polyethylene membrane, and the electrolyte is a ethylene carbonate / dimethyl carbonate / (EC:DMC volume ratio 1:1) solution containing 1 mol / L lithium hexafluorophosphate.

[0121] The LCO-PVDF / OTB electrode-assembled liquid battery prepared in Example 1 was subjected to cyclic voltammetry testing at different scan rates. The tests were conducted using an electrochemical workstation within a voltage range of 3.0–4.3 V at different scan rates (0.05 mV / s, 0.1 mV / s, 0.15 mV / s, and 0.2 mV / s). The cyclic voltammetry curves are attached. Figure 14The figure shows a reversible redox peak at 3.8V and 4.1V, indicating that the positive electrode sheet containing the composite binder POSS-g-TFEMA / B-PEGMA prepared in Example 1 has good reversibility of electrode reaction.

[0122] The peak current and linear fitting curves of the peak current and the square root of the scan rate of the cyclic voltammetry curves of the LCO-PVDF / OTB electrode-assembled liquid battery prepared in Example 1 at different scan rates are shown in the appendix. Figure 15 The linear fitting curves of peak current versus the square root of the scan rate show that the fitting slope for the oxidation section is 3.83 for the LCO-PVDF / OTB system and 2.52 for the LCO-PVDF system; the fitting slope for the reduction section is 1.77 for the LCO-PVDF / OTB system and 1.19 for the LCO-PVDF system. According to the Randles-Sevcik formula, a larger fitting slope indicates a higher lithium-ion diffusion coefficient. It can be seen that after introducing OTB to modify the binder, the lithium-ion diffusion coefficients corresponding to the electrode oxidation and reduction processes are significantly improved, indicating that OTB effectively optimizes the lithium-ion migration and transport kinetics performance inside the LCO electrode.

[0123] The galvanic-current intermittent titration (GITT) test curves of the LCO-PVDF / OTB electrode assembly liquid battery prepared in Example 1 are shown in the attached figure. Figure 16 By measuring Li + The chemical diffusion coefficient in the electrode solid material is used to quantitatively assess its kinetic rate; a larger diffusion coefficient value indicates that Li... + The smoother the movement within the material, the better the rate performance and fast charging potential of the electrode. (According to the appendix...) Figure 16 The GITT test yielded the lithium-ion diffusion coefficient during charging and discharging, see attached figure. Figure 17 and attached Figure 18 .

[0124] The LCO-PVDF / OTB electrode assembly liquid battery prepared in Example 1 was subjected to rate testing, see attached figure. Figure 19 The test conditions were to conduct charge and discharge tests at different charge and discharge rates of 0.1C, 0.5C, 1C, 3C, 5C, 7C, and 0.1C.

[0125] The LCO-PVDF / OTB electrode assembly liquid battery prepared in Example 1 underwent long-cycle testing, as shown in the attached figure. Figure 20 The long-cycle test conditions are 3.0V-4.3V, and the long-cycle test is performed at a 1C rate.

[0126] To better illustrate the effects of the embodiments of the present invention, Comparative Example 1 is compared with Example 1.

[0127] Comparative Example 1 This comparative example provides a method for preparing an adhesive film and performance testing of the assembled lithium battery. The film preparation method and testing method are the same as in Example 1, but instead of using the cage-type siloxane-based semi-interpenetrating network copolymer POSS-g-TFEMA / B-PEGMA, only the conventional adhesive PVDF is used.

[0128] LCO-PVDF electrode sheets were prepared using the comparative binder PVDF solution according to conventional methods.

[0129] Fourier transform infrared spectroscopy (FTIR) of the PVDF thin film prepared in Comparative Example 1 is shown in the appendix. Figure 8 Comparing the four Fourier transform infrared (FTIR) curves, it can be seen that the pure PVDF in Comparative Example 1 only exhibits its own CF framework vibration signal. Both the synthesized OTB and the film-formed OTB stably exhibit characteristic absorptions representing their own structure, such as the C=O carbonyl group, COC ether bond, and Si-O-Si silicon-oxygen bond. The film-forming process did not destroy the chemical framework of OTB. The PVDF / OTB composite film simultaneously possesses the CF peak of the PVDF matrix and the absorption peaks of all characteristic functional groups of OTB, with no new chemical bond characteristic peaks appearing. This indicates that the composite binder PVDF / OTB formed by physically blending OTB and PVDF in Example 1 retains the complete OTB structure.

[0130] The thermal deformation test of the PVDF film prepared in Comparative Example 1 is shown in the appendix. Figure 9 As can be seen, both the PVDF-OTB film based on cage-like siloxane semi-interpenetrating network copolymer in Example 1 and the PVDF film based on conventional binder in Comparative Example 1 can withstand a high temperature of 180°C, indicating that the semi-interpenetrating network copolymer synthesized by random copolymerization in Example 1 and the PVDF-OTB film prepared using it have excellent thermal stability.

[0131] The resistivity test results of the LCO-PVDF electrode prepared in Comparative Example 1 are shown in the appendix. Figure 12 As can be seen, the LCO-PVDF electrode without OTB in Comparative Example 1 has the highest resistivity. In Example 1, the resistivity of the LCO-PVDF / OTB electrode after the introduction of OTB decreased significantly, and the resistivity further decreased when the OTB ratio was increased from 1:1 to 1:2. This indicates that the OTB added in Example 1 can effectively optimize the conductivity of the LCO-PVDF electrode system and improve the charge conduction efficiency.

[0132] The LCO-PVDF electrode prepared using this comparative example was immersed in electrolyte for 10 days to test the swelling rate of the binder. (See attached figure.) Figure 13As can be seen, the introduction of a small amount of OTB (PVDF to OTB mass ratio of 1:1) into the LCO-PVDF / OTB electrode can reduce the electrolyte swelling degree of the PVDF binder. However, when the OTB ratio is increased to 1:2, the swelling rate increases sharply. This indicates that low OTB content can slightly optimize the electrolyte swelling resistance of the binder. High OTB content, due to its own electrolyte-loving structure such as polyethylene glycol flexible ether chains, will significantly aggravate the swelling of the composite binder in the electrolyte.

[0133] Comparative Example 1: SEM and EDS tests of PVDF films prepared based on conventional binder PVDF are shown in the appendix. Figure 21 .

[0134] Comparative Example 1: SEM and EDS tests of LCO-PVDF electrodes prepared based on conventional binder PVDF are shown in the appendix. Figure 22 ,in Figure 22 (a) SEM image of LCO-PVDF electrode prepared with conventional binder PVDF. Figure 22 (b) EDS diagram of LCO-PVDF electrode prepared with conventional binder PVDF.

[0135] The resistivity tests of the LCO-PVDF electrode prepared in this comparative example are shown in the appendix. Figure 12 As can be seen, the LCO-PVDF electrode prepared based on the traditional binder PVDF in this comparative example has the highest resistivity. With the addition of the semi-interpenetrating network copolymer POSS-g-TFEMA / B-PEGMA based on cage-like siloxane, the resistivity of the LCO-PVDF / OTB electrode can be reduced, indicating that the PVDF-OTB binder can effectively reduce the electron transport distance between positive electrode particles and increase the electronic conductivity.

[0136] The swelling rate test of the LCO-PVDF electrode prepared in this comparative example is shown in the appendix. Figure 13 As can be seen, when the ratio of the semi-interpenetrating network copolymer POSS-g-TFEMA / B-PEGMA based on the cage-like siloxane in the embodiment is 1:1, the swelling ratio of the electrode is slightly lower than that of LCO-PVDF. However, as the ratio of the semi-interpenetrating network copolymer POSS-g-TFEMA / B-PEGMA based on the cage-like siloxane in the embodiment increases to 1:2, the swelling ratio of the electrode LCO-PVDF / OTB increases sharply, which will be detrimental to battery cycling.

[0137] Cyclic voltammetry curves at different scan rates for the LCO-PVDF electrode-assembled liquid battery prepared in Comparative Example 1 are shown in the appendix. Figure 23 .

[0138] The linear fitting curves of the peak current and the square root of the scan rate of the cyclic voltammetry curves of the liquid battery assembled with LCO-PVDF electrodes prepared in Comparative Example 1 at different scan rates are compared with the linear fitting curves of the liquid battery assembled with LCO-PVDF / OTB electrodes in Example 1. (See Appendix) Figure 15 It can be seen that the redox fitting slope of the battery assembled based on the LCO-PVDF electrode prepared with the traditional binder PVDF is lower than that of the battery assembled based on the LCO-PVDF / OTB electrode prepared with the cage-like siloxane semi-interpenetrating network copolymer POSS-g-TFEMA / B-PEGMA based on the example. This indicates that the active lithium ions diffuse faster in the LCO-PVDF / OTB electrode prepared with the cage-like siloxane semi-interpenetrating network copolymer POSS-g-TFEMA / B-PEGMA based on the example.

[0139] The LCO-PVDF electrode assembly liquid battery prepared in Comparative Example 1 was subjected to GITT testing, see Appendix. Figure 24 The diffusion coefficients of lithium ions during charging and discharging were obtained based on GITT tests, as shown in the appendix. Figure 17 and 18 Further evidence shows that active lithium ions diffuse faster in LCO-PVDF / OTB electrodes prepared based on the semi-interpenetrating network copolymer POSS-g-TFEMA / B-PEGMA of cage-like siloxanes.

[0140] Liquid cells were assembled using the LCO-PVDF electrodes prepared in this comparative example, and rate tests were conducted (see attached figure). Figure 19 It can be seen that under different rate testing conditions, the discharge capacity of the battery assembled with LCO-PVDF / OTB electrode based on the semi-interpenetrating network copolymer POSS-g-TFEMA / B-PEGMA of cage-type siloxane is higher than that of the battery assembled with LCO-PVDF electrode based on the traditional PVDF binder.

[0141] The LCO-PVDF electrode prepared in this comparative example was used to assemble a liquid battery for long-cycle testing. See attached figure. Figure 20As can be seen, during the long-cycle test, the battery in Example 1 with an LCO-PVDF / OTB electrode prepared based on the cage-like siloxane semi-interpenetrating network copolymer POSS-g-TFEMA / B-PEGMA showed little difference from the battery in Comparative Example 1 with an LCO-PVDF electrode prepared based on a conventional PVDF binder in the first 50 cycles. However, with the increase in the number of cycles, the battery with the LCO-PVDF electrode prepared based on the conventional PVDF binder exhibited faster capacity decay, with a capacity retention rate of 64.1% after 250 cycles, while the battery with the LCO-PVDF / OTB electrode prepared based on the cage-like siloxane semi-interpenetrating network copolymer POSS-g-TFEMA / B-PEGMA had a capacity retention rate of 80.8%. This indicates that the cage-like siloxane semi-interpenetrating network copolymer POSS-g-TFEMA / B-PEGMA can effectively improve the cycle performance of the battery.

[0142] Example 2 This embodiment provides a preparation process for a semi-interpenetrating network copolymer based on cage-type siloxanes. Unlike Example 1, it prepares a different boron-substituted polyether matrix. The specific process is as follows.

[0143] (1) Synthesize boronized polyether matrix B-PEGDA containing cyclic borate ester groups and ether oxygen units.

[0144] Weigh 1.0 g of 2,5-dimethylhexane-2,5-diol and dissolve it in 50 ml of anhydrous acetonitrile along with 0.9 ml of trimethyl borate. Place the solution in a 100 ml three-necked flask, set the oil bath temperature to 65 °C, and stir for 1 hour under an inert argon atmosphere. Then, add 3.57 g of polyethylene glycol acrylate (PEGDA) to the three-necked flask and continue stirring for 3 hours. After the reaction is complete, collect the reaction solution and remove residual acetonitrile by vacuum distillation at room temperature. Dissolve the obtained product in toluene, remove insoluble impurities by filtration, remove the residual toluene solution by rotary evaporation, and finally dry the solid product under vacuum at room temperature for 24 hours to synthesize a boronized polyether matrix containing cyclic borate ester groups and ether oxygen units, abbreviated as B-PEGDA. In this step, cyclic borate ester groups are introduced into the polyether side chains through transesterification, giving the product ionic conductivity while retaining the polymerizable methacrylate double bonds for subsequent copolymerization.

[0145] The synthesis scheme of boron-substituted polyether matrix B-PEGDA in this embodiment is as follows: .

[0146] (2) The semi-interpenetrating network copolymer POSS-g-TFEMA / B-PEGDA based on cage-type siloxane was prepared by free radical polymerization as follows.

[0147] Octapolysilsesquioxane (OV-POSS) (0.6772 g), 2,2,2-trifluoroethyl methacrylate (TFEMA) (1.513 g), and boron-modified polyether matrix B-PEGDA (3.0574 g) containing cyclic borate ester groups and ether oxygen units were placed in a 100 ml three-necked flask. A certain amount of anhydrous acetonitrile was added to dissolve the solid, and then AIBN (0.5 wt% of the total mass of OV-POSS, TFEMA, and PEGDA) was used as the initiator. The mixture was heated to 70 °C under an argon atmosphere for 12 hours. After the reaction, the mixture was dissolved in tetrahydrofuran solution and precipitated three times in petroleum ether to remove residual monomers. Finally, the collected product was dried under vacuum at 60 °C for 12 hours to obtain a semi-interpenetrating network copolymer, abbreviated as POSS-g-TFEMA / B-PEGDA.

[0148] The synthesis scheme of POSS-g-TFEMA / B-PEGDA in this embodiment is as follows: .

[0149] This embodiment successfully synthesized a semi-interpenetrating network copolymer based on cage-like siloxanes, namely POSS-g-TFEMA / B-PEGDA.

[0150] In summary, the semi-interpenetrating network copolymer based on cage-like siloxanes provided in this embodiment of the invention has the characteristics of high bonding strength, good flexibility, excellent ionic conductivity, and strong interfacial interaction with active materials and electrolytes. The liquid battery assembled using the electrode prepared by the semi-interpenetrating network copolymer based on cage-like siloxanes in this embodiment has excellent cycle stability, which has important scientific significance and application value for improving the long-term cycle life and rate performance of high-energy-density batteries and solid-state batteries.

[0151] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., 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 cage siloxane based semi- interpenetrating network copolymer characterized in that, The semi-interpenetrating network copolymer is formed by the polymerization reaction of cage-type polyhedral oligomeric silsesquioxane, boronized polyether matrix and fluorinated matrix; The cage polyhedral oligomeric silsesquioxane has a general structure of (RSiO 3 / 2 ) n wherein n is 6, 8, 10 or 12, and R is an organic functional group participating in the polymerization reaction. The boron-substituted polyether matrix is ​​formed by transesterification of a dihydroxy compound, an alkoxy boron compound, and a polyether-branched (meth)acrylate compound; the polyether-branched (meth)acrylate compound includes one or more of polyether-branched acrylate compounds and their derivatives, and polyether-branched methacrylate compounds and their derivatives. The fluorinated matrix includes one or more of the following: fluorinated vinyl monomers, fluorinated styrene monomers, fluorinated acrylate monomers, or fluorinated methacrylate monomers.

2. The semi-interpenetrating network copolymer of claim 1, wherein The R includes one or more organic functional groups selected from vinyl, epoxy, amino, hydroxy, or methacryloyloxy.

3. The semi-interpenetrating network copolymer of claim 1, wherein The dihydroxy compound includes one or more of the following: ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,5-dimethylhexane-2,5-diol, hydroquinone, bisphenol A, cyclopentanediol, or cyclohexanediol. The alkoxy boron compounds include one or more of the following: trimethyl borate, triethyl borate, tripropyl borate, tributyl borate, triethanolamine borate, triphenyl borate, trimethoxyboronium, or triisopropoxyboronium. The acrylate compounds containing polyether branches and their derivatives include one or more of polyethylene glycol acrylate, polypropylene glycol acrylate, polyethylene glycol methyl ether acrylate, polypropylene glycol methyl ether acrylate, polyethylene glycol diacrylate, and polypropylene glycol diacrylate. The polyether-branched methacrylate compounds and their derivatives include one or more of polyethylene glycol methacrylate, polypropylene glycol methacrylate, polyethylene glycol methyl ether methacrylate, polypropylene glycol methyl ether methacrylate, polyethylene glycol dimethacrylate, and polypropylene glycol dimethacrylate.

4. The semi-interpenetrating network copolymer of claim 1, wherein The fluorinated vinyl monomers include tetrafluoroethylene or trans-1,3,3,3-tetrafluoropropylene; the fluorinated styrene monomers include one or more of 2-fluorostyrene, 3-fluorostyrene, or 4-fluorostyrene; the fluorinated methacrylate monomers include one or more of 2,2,2-trifluoroethyl methacrylate, pentafluoropropyl methacrylate, nonafluoropentyl methacrylate, methyl 2-trifluoromethacrylate, or tert-butyl 2-trifluoromethacrylate.

5. A method for preparing the semi-interpenetrating network copolymer according to any one of claims 1-4, characterized in that, The preparation method includes: A dihydroxy compound, an alkoxy boron compound, and a (meth)acrylate compound containing polyether branches were subjected to transesterification in an organic solvent. After the reaction was completed, the mixture was purified by post-treatment to obtain a boron-substituted polyether matrix. The boron-substituted polyether matrix, cage-like polyhedral oligomeric silsesquioxane, and fluorine-containing matrix are mixed in proportion, an initiator is added, and a polymerization reaction is carried out under an inert atmosphere to obtain a semi-interpenetrating network copolymer based on cage-like siloxane.

6. The preparation method according to claim 5, characterized in that, The mass ratio of the dihydroxy compound, the alkoxyboron compound, and the polyether-branched (meth)acrylate compound is 1:0.5-2:1-5. The organic solvent includes one or more of acetonitrile, toluene, tetrahydrofuran, dichloromethane, N,N-dimethylformamide, or dimethyl sulfoxide.

7. The preparation method according to claim 5, characterized in that, The mass ratio of the boron-substituted polyether matrix, the cage-like polyhedral oligomeric silsesquioxane, and the fluorinated matrix is ​​1–20: 0.5–10: 1–30. The initiator includes one or more of the following: azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, di-tert-butyl peroxide, tert-butyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxide, and potassium persulfate; The heating temperature is 50℃~120℃; The polymerization reaction includes one or more of the following: living anionic polymerization, cationic polymerization, ligand polymerization, ring-opening polymerization, free radical polymerization, in-situ polymerization, or click chemical reaction polymerization.

8. A composite adhesive, characterized in that, The composite adhesive includes the semi-interpenetrating network copolymer as described in any one of claims 1-4 and other adhesives.

9. The composite adhesive according to claim 8, characterized in that, The other binders include: polyvinylidene fluoride (PVDF), polyacrylic acid (PAA), polymethyl methacrylate (PMMA), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC-Na), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), fluorinated ethylene-propylene copolymer (FEP), perfluorosulfonic acid resin, ethyl polyacrylate, butyl polyacrylate, hydroxyethyl polymethacrylate, polycyanoacrylate, polyethylene glycol, polyethylene oxide, polypropylene glycol, polylactic acid, polycaprolactone, polyethylene terephthalate, sodium alginate, chitosan, cyclodextrin, epoxy resin, phenolic resin, polyurethane, polyvinyl alcohol, polyvinylpyrrolidone, poly(3,4-ethylenedioxythiophene), polystyrene sulfonic acid, polyaniline, or one or more of polypyrrole. The other adhesives constitute a percentage of the total mass of the composite adhesive that is greater than 0% and less than or equal to 70%.

10. A battery, characterized in that, The battery comprises the composite binder as described in any one of claims 8-9.

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