Polyethylene oxide-based block copolymer containing carborane hard segment, preparation method and solid electrolyte membrane

Abstract

The application discloses a polyethylene oxide-based block copolymer containing carborane hard segments, a preparation method and a solid electrolyte membrane, relates to the technical field of PEO-based solid electrolytes, and the structural general formula of the copolymer is PEO-b-P-LiCAr-MA, which comprises a soft segment PEO at the head and a hard segment LiCAr-MA connected with the soft segment, the soft segment is polyethylene oxide, and the hard segment is poly(lithium-o-ten carborane methyl propionate), and the structural general formula is: [-CH2-C(CH3)(COO-CH2-C2B 10 H 11 ‑Li + )] m , m=9-90, and the hard segment accounts for 25-35% of the total weight of the copolymer. By block polymerization, the flexible PEO and the single-ion conductor hard segment coexist in the same polymer chain, a double-continuous-phase nanostructure is formed, and the mechanical strength, ion unidirectional migration and conductivity of the copolymer are synergistically optimized.

Description

Technical Field

[0001] This invention relates to the field of PEO-based solid electrolyte technology, specifically to a polyoxyethylene block copolymer containing carborane hard segments, its preparation method, and a solid electrolyte membrane. Background Technology

[0002] Polyethylene oxide (PEO)-based polymers are widely used as electrolyte membranes in solid-state lithium batteries due to their excellent film-forming properties and flexibility. However, traditional PEO electrolyte membranes suffer from common drawbacks such as high crystallinity and poor room-temperature performance. At room temperature, the PEO segments are highly crystalline, limiting ion migration channels and resulting in conductivity typically below 1 × 10⁻⁶. -4 The conductivity of S / cm requires heating to above 60℃ to achieve higher conductivity, which is not suitable for room temperature energy storage devices.

[0003] Secondly, traditional PEO electrolytes require the introduction of binary lithium salts (such as LiTFSI and LiPF6), where both positive and negative ions can migrate (dual-ion conduction). This easily leads to concentration polarization during high-rate and long-term cycling, and the severe polarization caused by dual-ion migration reduces output power and cycle life. Existing technologies reduce negative ion migration by copolymerizing PEO with sulfonate or phosphate single-ion conductors as hard segments, but the hard and soft segments lack compatibility, resulting in coarse phase separation and discontinuous ion channels. The carboxylic acid groups in the sulfonate hard segments have strong coordination with lithium ions, leading to limited improvement in the migration number, and the room temperature conductivity is still generally only 0.3–0.4 mS / cm.

[0004] In addition, traditional PEO-based electrolyte membranes have insufficient mechanical strength and are easily punctured by dendrites. Although they can be reinforced by inorganic fillers (SiO2, Al2O3, LLZO), the poor interfacial bonding between inorganic particles and the PEO matrix leads to increased membrane brittleness and poor winding processing performance. Furthermore, the inorganic reinforcement scheme has not solved the problem of dual ion migration. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a polyoxyethylene block copolymer containing carborane hard segments, a preparation method, and a solid electrolyte membrane.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A first aspect of the present invention is to provide a polyoxyethylene block copolymer containing a carborane hard segment, having the general formula PEO-bP-LiCAr-MA, comprising a soft segment PEO at the first end and a hard segment P-LiCAr-MA connected to the soft segment, wherein the soft segment is selected from polyoxyethylene with the general structural formula [CH2-CH2-O]. nn=100-600, the hard segment is selected from poly(lithium-o-decanoborane methylpropionate), with the general structural formula: [-CH2-C(CH3)(COO-CH2-C2B 10 H 11 -Li + )] m m=9-90, and the hard segment accounts for 25-35% of the total weight of the copolymer.

[0008] This invention designs a poly(ethylene oxide) copolymer material for electrolyte membranes. Through block polymerization, flexible PEO (which transmits chain segment mobility) and single-ion conductor hard segments (which only migrate lithium ions) coexist in the same polymer chain to form a bicontinuous phase nanostructure, thereby synergistically optimizing mechanical strength, unidirectional ion migration and conductivity.

[0009] In this application, a carborane (CAr)-based single-ion conductor is introduced as a hard segment block into a poly(ethylene oxide) copolymer system. The general formula of this polymer material can be represented as: PEO-bP-LiCAr-MA. Here, b represents the "block" symbol, P represents the "polymer" symbol, and P-LiCAr-MA is the carborane-containing hard segment block designed in this application, specifically poly(lithium-o-decapod carborane methyl propionate), with the general structural formula: [-CH2-C(CH3)(COO-CH2-C2B 10 H 11 -Li + )] m m=9-90. As the hard segment of the copolymer system, it replaces the traditional sulfonate or phosphate hard segments (such as Li-SO3). - C2B 10 H 12 The highly delocalized electronic structure of borocarbonanes makes the anion (C2B) 10 H 11 - ) and Li + The interaction forces are much weaker than those of traditional sulfonate groups, and the coordination energy is low (approximately 58-65 kJ / mol), significantly reducing the Li... + The migration barrier is reduced, decreasing the time lithium ions are "bound" by anions, which can enable Li-ion exchange in electrolyte membranes. + High-speed migration. Meanwhile, because traditional PEO-based electrolytes often require the addition of binary salts such as LiTFSI, both anions and cations migrate together (migration number t). + (~0.2–0.3), which easily induces concentration polarization; the P-LiCAr hard segment of this application only allows Li... + Migration (theoretical t) + ≈1), which eliminates concentration polarization at its source and improves battery rate performance and cycle stability.

[0010] Secondly, this application modifies a PEO-based polymer by adding blocks. The PEO segments are polar, flexible segments that form continuous ion transport channels with lithium salt solvation, exhibiting good mobility. The carborane hard segments, on the other hand, are weakly polar, large-volume cage-like anionic units with a rigid framework and steric hindrance. When carborane units are randomly distributed on the polymer chain, the continuous ion transport channels are blocked by hard-segment islands, resulting in discontinuous migration pathways. Simultaneously, the carborane mechanical framework cannot form a continuous, interconnected structure. This application designs a structure where the boron carborane hard segments and PEO soft segments are polymerized and positioned at opposite ends of the copolymer chain. While maintaining ion transport channels, the arrangement at the block junctions forms a bicontinuous nanophase structure: connected to the soft segments to transport Li. + It connects with the hard segment to provide mechanical support and limit the excessive crystallization of the PEO chain segment, and avoids large-scale thermodynamic phase separation between the rigid borocarbon hard segment and the soft PEO chain.

[0011] Based on this, the n of the PEO soft segment is controlled to be 100-600, and the m of the poly(lithium-ortho-decapod carborane methylpropionate) hard segment is controlled to be 9-90, with the carborane hard segment accounting for 25-35% of the total weight of the copolymer. At this point, the soft segment length is sufficient to form a continuous PEO phase, and the hard segment length is sufficient to form a through-through rigid phase. This ratio achieves good synergy between channel penetration and supporting framework at the bicontinuous phase scale. The conductivity at room temperature can reach 1.2 mS / cm, while the modulus is increased to 20-25 MPa, and the synergistic effect between the soft and hard segments is optimal. If the proportion of carborane hard segments is too high (>35%), it will reduce the flexibility of the copolymer, block ion channels, and lead to a decrease in conductivity; if the proportion of carborane hard segments is too low (<25%), the framework effect is insufficient, the mechanical properties are poor, and dendrites are prone to piercing the film.

[0012] Preferably, the molar ratio of ethylene oxide monomer in the soft segment to weakly coordinated lithium ions in the hard segment is EO:Li + =7~11∶1, further adjust the length ratio of soft and hard segments to optimize their synergistic effect.

[0013] Preferably, the number-average molecular weight M of the polyethylene oxide in the soft segment is... n =4405-26430, further controlling the mobility and crystallinity of the chain segments.

[0014] A second aspect of the present invention provides a method for preparing a polyoxyethylene block copolymer containing carborane hard segments, comprising the following steps:

[0015] S1 chain transfer agent activation: 4-cyano-4-[(dodecylthiocarbonyl)thio]valoric acid is dissolved in anhydrous dichloromethane at a concentration of 1-10 mg / mL. Dicyclohexylcarbodiimide and 4-dimethylaminopyridine are added, and the mixture is stirred in an ice-water bath at 0-5°C for 30-120 min. The molar ratio of 4-cyano-4-[(dodecylthiocarbonyl)thio]valoric acid, dicyclohexylcarbodiimide, and 4-dimethylaminopyridine is 1:(1.0~1.5):(0.05~0.2), generating a chain transfer solution containing an active O-acylisourea intermediate.

[0016] S2 Activated Polyethylene Oxide: Polyethylene oxide is dissolved in anhydrous tetrahydrofuran and added to the chain transfer solution. The reaction is carried out at room temperature and under nitrogen protection for 1-24 h to obtain the activated polyethylene oxide intermediate PEO-macro-RAFT. The molar ratio of the terminal hydroxyl group of the polyethylene oxide to the 4-cyano-4-[(dodecylthiocarbonyl)thio]pentanoic acid is 1:1.2~2.0.

[0017] S3 Preparation of Hard Segment Monomer: Take Lithium Borane (Li2C2B) 10 H 10 It undergoes a nucleophilic substitution reaction with chloromethyl methacrylate (Cl-CH2-MA) in anhydrous tetrahydrofuran, with a molar ratio of Li2C2B. 10 H 10 The reaction ratio of Cl-CH2-MA is 1:1.1~1.2. The initial reaction temperature is -10~-20℃, then the temperature is raised to room temperature and stirred for 2-4 hours under inert gas protection until the reaction is complete and crude monomer is obtained. Then, sodium carbonate solution is added under ice bath to replace lithium salt. The molar ratio of crude monomer to sodium carbonate is 1:1.2~2. The temperature is raised to room temperature and stirred for 1-2 hours until lithium carbonate precipitate Li2CO3 is completely precipitated. After filtration, lithium-o-decatoporbora methylpropionate monomer LiCAr-MA is obtained.

[0018] S4 Prepolymerization: The polyethylene oxide intermediate PEO-macro-RAFT and the lithium-o-decapoded carborane methylpropionate monomer LiCAr-MA are dissolved in an anhydrous organic solvent and placed in a Schlenk reaction flask. The concentration of the polyethylene oxide intermediate PEO-macro-RAFT is 10-50 mg / mL, the concentration of the lithium-o-decapoded carborane methylpropionate monomer LiCAr-MA is 0.1-1 M, and the molar ratio of the polyethylene oxide intermediate PEO-macro-RAFT and the lithium-o-decapoded carborane methylpropionate monomer LiCAr-MA is 1:1 to 1:100. After freezing in liquid nitrogen at -190 to -196°C for 3-5 min, vacuum is applied and nitrogen is backfilled. The vacuuming and nitrogen backfilling operation is repeated 1-3 times to obtain the prepolymer solution.

[0019] S5 polymerization reaction: Azobisisobutyronitrile is added to the prepolymer solution, wherein the molar ratio of azobisisobutyronitrile to 4-cyano-4-[(dodecylthiocarbonyl)thio]valerate is 1:5 to 1:10, and the reaction is carried out in an oil bath at 65-70°C for 22-30 hours, with nitrogen protection and stirring during the reaction.

[0020] S6 Reaction Quenching: Turn off heating and stirring, allow the reaction solution to cool naturally to room temperature, and add anisole solution to quench the reaction. The solvent of the anisole solution is anhydrous tetrahydrofuran, to obtain a copolymer solution.

[0021] S7 Post-precipitation treatment: Pre-cool the precipitant to -18~-20℃, add the copolymer solution dropwise to the pre-cooled precipitant at a rate of 1-2 drops / s, the volume ratio of the copolymer solution to the precipitant is 1:10~1:100, and stir at a speed of 200-300 rpm to generate precipitate; after the addition is complete, continue stirring for 10~60 min to ensure complete precipitation, collect the precipitate and wash and dry it to obtain the polyoxyethylene block copolymer containing carborane hard segments.

[0022] Carborane units are spatially large cage-like structures with a rigid framework and significant steric hindrance. They are also weakly polar, which thermodynamically tends to cause phase separation with the polar flexible PEO segments. To avoid this, this application uses a RAFT chain transfer agent to control polymerization, resulting in highly selective and efficient block bonding between the two components. Furthermore, without interfering with ion transport, the two components exhibit excellent mechanical synergy, forming a flexible yet robust framework.

[0023] Specifically, the RAFT chain transfer agent selected was 4-cyano-4-[(dodecylthiocarbonyl)thio]pentanoic acid (CDTPA), which was activated with dicyclohexylcarbodiimide (DCC) and 4-dimethylaminopyridine (DMAP). The carboxyl group of the RAFT reagent itself is weakly reactive; activation with DCC, coupled with DMAP catalysis, generates an intermediate containing an active O-acyl isourea that reacts better with the terminal hydroxyl group of PEO (PEO-OH). The molar ratio of the three components was controlled at 1:(1.0~1.5):(0.05~0.2) to modify the PEO segment and build a bonding bridge between the soft and hard segments. During activation, the molar ratio of the terminal hydroxyl group of polyethylene oxide (PEO-OH) to 4-cyano-4-[(dodecylthiocarbonyl)thio]pentanoic acid (CDTPA) was controlled at 1:1.2~2.0. The modified active PEO segment intermediate is denoted as PEO-macro-RAFT.

[0024] Next, prepare the hard segment monomer LiCAr-MA for grafting. First, take lithium borane Li2C2B. 10 H 10The crude monomer, LiCAr-MA, is produced by a nucleophilic substitution reaction with chloromethyl methacrylate (Cl-CH2-MA) to generate lithium chloride and lithium-o-decapodized carborane methylpropionate monomer (LiCAr-MA). Li2C2B... 10 H 10 Extremely sensitive to water, Li2C2B 10 H 10 The reaction with chloromethyl methacrylate (Cl-CH2-MA) was carried out under strictly anhydrous conditions, with the molar ratio controlled at 1:1.1~1.2 to ensure Li2C2B 10 H 10 The reaction should proceed completely while avoiding the introduction of hydrolysis byproducts from excess Cl-CH2-MA. Anhydrous tetrahydrofuran (THF) should be used as the reaction solvent; if necessary, THF should be refluxed with sodium / benzophenone to ensure a moisture content <10 ppm. The initial reaction temperature should be maintained at -10 to -20°C to reduce the risk of Cl-CH2-MA hydrolysis. The temperature should then be slowly raised to room temperature, and the reaction should continue with stirring for 2-4 hours under an inert gas atmosphere such as nitrogen or argon to prevent Li2C2B hydrolysis. 10 H 10 Oxidation or THF hygroscopicity can cause the reaction to fail until it is complete. Alternatively, it can be achieved through... 1 The reaction progress was monitored by ¹H NMR, and the reaction endpoint was reached when the signal of the C-Cl bond disappeared in the δ~4.0 ppm range. Alternatively, Li could be determined by ICP-MS. + The residual amount should ideally be <5 ppm. Crude lithium-o-decaborane methacrylate is produced, with the yield of lithium-o-decaborane methacrylate monomer (LiCAr-MA) typically between 80-90% in this step.

[0025] The crude product is subjected to salt exchange with sodium carbonate and lithium salt is then replaced. Sodium carbonate (Na₂CO₃) replaces lithium ions in LiCAr-MA, yielding a more stable monomer (NaCAr-MA). Simultaneously, the lithium salt byproduct (LiCl) is removed. Through these two exchange processes, a higher purity and more stable hard-segment monomer, LiCAr-MA, is obtained. In this step, the yield of lithium-o-decatoporborane methacrylate monomer (LiCAr-MA) can reach over 95%. The material ratio of crude monomer to sodium carbonate is controlled during the process to ensure the purity of Li... +It is fully precipitated as Li2CO3 while avoiding the excessive introduction of alkaline impurities due to Na2CO3. Since sodium carbonate dissolves in water to form a solution, the volume ratio of THF to water in the mixed system is approximately 4:1 at this time. THF maintains the solubility of the monomer, and a small amount of water promotes the ionization of Na2CO3 to improve the reaction efficiency. The displacement reaction is carried out in an ice bath at 0 °C. An aqueous solution of Na2CO3 is slowly added to the crude monomer solution dissolved in THF in the previous step to reduce the risk of Na2CO3 hydrolysis. Subsequently, it is raised to room temperature and stirred for 1 - 2 hours until the white Li2CO3 precipitate is completely formed. After the reaction is completed, the Li2CO3 precipitate is filtered off, and the filtrate is concentrated under reduced pressure to obtain the crude product. Optionally, if high-purity monomers are required, silica gel column chromatography (petroleum ether∶ethyl acetate = 5∶1) can be used for purification.

[0026] The specific reaction process is as follows:

[0027] (1)Nucleophilic substitution to form the crude monomer:

[0028] .

[0029] Li2C2B 10 H 10 The C-Li bond in has strong nucleophilicity (similar to Grignard reagent), attacks the α-carbon of Cl-CH2-MA (Cl - is the leaving group), undergoes an SN2 reaction, and generates carboborane methacrylate (LiC2B 10 H 10 -CH2-MA, which can be abbreviated as LiCAr-MA) and the by-product LiCl. The ester group (MA) of Cl-CH2-MA stabilizes the positive charge of the α-carbon, making it more susceptible to nucleophilic attack. Otherwise, the Cl-CH3 analog is difficult to react. At the same time, the electron-withdrawing effect of the ester group enhances the leaving ability of Cl - and improves the reaction efficiency.

[0030] (2)Salt exchange:

[0031] .

[0032] As a weak alkaline salt, Na2CO3 preferentially precipitates Li + (Ksp(Li2CO3) << Ksp(Na2CO3)), pushing the equilibrium to the right.

[0033] (3)Back-exchange of lithium salt:

[0034] .

[0035] NaCAr-MA exhibits better solubility in organic solvents (THF), facilitating purification via filtration. The presence of LiCl ensures that the final product is in lithium salt form, suitable for subsequent in-situ polymerization reactions.

[0036] The polymerization reaction solution was then pre-prepared. The prepared activated polyethylene oxide intermediate PEO-macro-RAFT and the purified lithium-o-decapod borane methylpropionate monomer LiCAr-MA were dissolved in an anhydrous organic solvent and placed in a Schlenk reaction flask. The Schlenk reaction flask was used to create an anhydrous and oxygen-free inert environment to ensure stable reaction. During the reaction, the mixture was frozen with liquid nitrogen, then evacuated and backfilled with nitrogen. This evacuation and nitrogen backfilling process was repeated 1-3 times to ensure thorough deoxygenation. The molar ratio of the activated polyethylene oxide intermediate PEO-macro-RAFT to the lithium-o-decapod borane methylpropionate monomer LiCAr-MA was controlled to be 1:10 to 1:100. The chain transfer mechanism of RAFT determines the length of the target block by controlling the ratio of chain transfer agent (PEO-macro-RAFT) to monomer. The monomer is in excess (10-100 times) to ensure that the chain end of PEO-macro-RAFT fully initiates the growth of new blocks (carborane methacrylate segments).

[0037] After preparing the prepolymer solution, the initiator azobisisobutyronitrile (AIBN) is added, and the carborane monomer is grafted onto it to initiate in-situ polymerization. The free radicals generated by the decomposition of AIBN attack the thiocarbonyl groups (C=S) in the RAFT chain transfer liquid (PEO-macro-RAFT), generating intermediate free radicals, which in turn initiate the chain growth of the monomer (LiCAr-MA). After the reaction begins, samples of 1 mL are taken at time intervals of 30 min, 1 h, 2 h, and 4 h to monitor molecular weight growth using GPC, while controlling the dispersion coefficient K≈1.15.

[0038] After the reaction is complete, turn off heating and stirring, and allow it to cool naturally to room temperature to avoid sudden cooling that could cause the glassware to break. Quench the reaction by adding an anisole solution dissolved in anhydrous tetrahydrofuran. It is understood that, to ensure the stability of the reaction, the polymerization process of this invention is carried out under anhydrous conditions.

[0039] After obtaining the copolymer solution following the reaction, a precipitation method was used to purify and extract the solid copolymer. First, the precipitant was pre-cooled for 30 minutes in an ice-salt bath (-20°C) or a freezer (-18°C). Then, the copolymer solution was slowly added dropwise to the pre-cooled precipitant at a rate of 1-2 drops / s using a dropper or syringe, with magnetic stirring employed during the process. After the addition was complete, stirring continued to ensure complete precipitation. The precipitate was collected by filtration or centrifugation and washed 1-3 times with the appropriate precipitating reagent to remove impurities adsorbed on the solid surface. Finally, drying yielded the polyoxyethylene block copolymer containing carborane hard segments as described in this application.

[0040] Preferably, the anhydrous organic solvent used in step S4 to dissolve the polyethylene oxide intermediate PEO-macro-RAFT and the lithium-o-decapod carborane methylpropionate monomer LiCAr-MA is toluene and / or tetrahydrofuran. Options for solvents to dissolve the PEO and carborane monomers include anhydrous toluene, anhydrous tetrahydrofuran, or a mixture of both to allow for greater freedom of hard segments during chain growth, thereby improving the compatibility of the block junctions between hard and soft segments and reducing local phase separation.

[0041] Preferably, the vacuuming in step S4 includes controlling the vacuum level inside the Schlenk reaction flask to ≤0.1 mbar and maintaining it for 5-10 minutes; the nitrogen backfilling includes filling the Schlenk reaction flask with nitrogen gas of ≥99.999% purity and controlling the pressure inside the flask to 1.05-1.1 atm. This further improves the vacuuming effect and removes oxygen or water vapor from the flask.

[0042] Preferably, the precipitant in step S7 is anhydrous diethyl ether or anhydrous n-hexane. The choice of precipitant can be adaptively adjusted according to the length of the hard segment and the length of the prepared copolymer to ensure complete hard segment precipitation.

[0043] Preferably, the collection of precipitate in S7 includes: collection by suction filtration using a Buchner funnel and filter paper with a pore size of 0.01-0.45 μm, or collection by centrifugation at 3000-10000 rpm for 5-60 min. The pore size of the filter paper is controlled to better filter out other impurities such as dicyclohexylurea (DCU) precipitate.

[0044] Preferably, the drying in S7 includes placing the collected solid precipitate on a petri dish and placing it in a vacuum drying oven at 25-60°C and a vacuum degree of 0.01-0.1 mbar for 12-36 hours.

[0045] A third aspect of the present invention is to provide a solid electrolyte prepared using the aforementioned polyoxyethylene block copolymer containing carborane hard segments as a material.

[0046] The beneficial effects of this invention are:

[0047] (1) This invention uses block polymerization to coexist flexible PEO (which transmits the ability of chain segments to move) and single-ion conductor hard segments (which only migrate lithium ions) in the same polymer chain to form a bicontinuous phase nanostructure, thereby achieving synergistic optimization of the mechanical strength, unidirectional ion migration and conductivity of the copolymer.

[0048] (2) This invention introduces carborane (CAr)-based single-ion conductors as hard segments into the polyethylene oxide (PEO) block copolymer system for the first time, and optimizes the structural design of the block polymer (PEO-bP-LiCAr-MA) to make it have the three major characteristics of low crystallinity, high single-ion mobility number and strong mechanical strength.

[0049] (3) This invention uses lithium-ortho-decapod carborane methyl propionate (LiCAr) as a single-ion conductor block (P-LiCAr-MA) to replace the traditional sulfonate or phosphate hard segments (such as Li-SO3). - The highly delocalized electronic structure makes the anion ([CAr]) - ) and Li + Formation of weak coordination significantly reduces Li + Migration energy barrier. By combining the high degree of freedom of the PEO chain segment, the room temperature conductivity is increased to 0.8–1.2 mS / cm (compared to only 0.3–0.4 mS / cm in the prior art).

[0050] (4) The high rigidity of the P-LiCAr-MA hard segment gives the material a tensile strength of 30-50MPa, which can resist lithium dendrite puncture. At the same time, the steric hindrance of carborane effectively inhibits the crystallization of PEO chain, and maintains an ion conductivity of 0.25mS / cm even at low temperature (-20℃).

[0051] (5) By designing RAFT chain transfer reagents to control the polymerization reaction, flexible PEO soft segments are placed at the chain head, while borocarbon hard segments are concentrated at the other end to form blocks. The block ratio of PEO soft segments to P-LiCAr-MA hard segments is optimized and adjusted to form a bicontinuous nanophase separation structure. This ensures ion channel connectivity while maintaining homogeneous mixing and regular chain segment distribution in the copolymer. This end arrangement utilizes soft segments to form a through-flow ion transport phase, while hard segments are continuously distributed in the interface region, forming a flexible and robust framework. This avoids the interface compatibility problems caused by traditional inorganic fillers (such as LLZO), ensuring the flexibility and processability of the film. Attached Figure Description

[0052] Figure 1 This is a schematic diagram of the structure of a poly(ethylene oxide) block copolymer PEO-bP-LiCAr-MA containing a carborane hard segment according to the present invention. Detailed Implementation

[0053] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0054] See Figure 1 The present invention provides a technical solution:

[0055] S1 chain transfer agent activation: 4-cyano-4-[(dodecylthiocarbonyl)thio]valoric acid is dissolved in anhydrous dichloromethane at a concentration of 1-10 mg / mL. Dicyclohexylcarbodiimide and 4-dimethylaminopyridine are added, and the mixture is stirred in an ice-water bath at 0-5°C for 30-120 min. The molar ratio of 4-cyano-4-[(dodecylthiocarbonyl)thio]valoric acid, dicyclohexylcarbodiimide, and 4-dimethylaminopyridine is 1:(1.0~1.5):(0.05~0.2), generating a chain transfer solution containing an active O-acylisourea intermediate.

[0056] S2 Activated Polyethylene Oxide: Polyethylene oxide is dissolved in anhydrous tetrahydrofuran and added to the chain transfer solution. The reaction is carried out at room temperature and under nitrogen protection for 1-24 h to obtain the activated polyethylene oxide intermediate PEO-macro-RAFT. The molar ratio of the terminal hydroxyl group of the polyethylene oxide to the 4-cyano-4-[(dodecylthiocarbonyl)thio]pentanoic acid is 1:1.2~2.0.

[0057] S3 Preparation of Hard Segment Monomer: Take Lithium Borane (Li2C2B) 10 H 10 It undergoes a nucleophilic substitution reaction with chloromethyl methacrylate (Cl-CH2-MA) in anhydrous tetrahydrofuran, with a molar ratio of Li2C2B. 10 H 10 The reaction ratio of Cl-CH2-MA is 1:1.1~1.2. The initial reaction temperature is -10~-20℃, then the temperature is raised to room temperature and stirred for 2-4 hours under inert gas protection until the reaction is complete and crude monomer is obtained. Then, sodium carbonate solution is added under ice bath to replace lithium salt. The molar ratio of crude monomer to sodium carbonate is 1:1.2~2. The temperature is raised to room temperature and stirred for 1-2 hours until lithium carbonate precipitate Li2CO3 is completely precipitated. After filtration, lithium-o-decatoporbora methylpropionate monomer LiCAr-MA is obtained.

[0058] S4 Prepolymerization: The polyethylene oxide intermediate PEO-macro-RAFT and the lithium-o-decapoded carborane methylpropionate monomer LiCAr-MA are dissolved in an anhydrous organic solvent and placed in a Schlenk reaction flask. The concentration of the polyethylene oxide intermediate PEO-macro-RAFT is 10-50 mg / mL, the concentration of the lithium-o-decapoded carborane methylpropionate monomer LiCAr-MA is 0.1-1 M, and the molar ratio of the polyethylene oxide intermediate PEO-macro-RAFT and the lithium-o-decapoded carborane methylpropionate monomer LiCAr-MA is 1:1 to 1:100. After freezing in liquid nitrogen at -190 to -196°C for 3-5 min, vacuum is applied and nitrogen is backfilled. The vacuuming and nitrogen backfilling operation is repeated 1-3 times to obtain the prepolymer solution.

[0059] S5 polymerization reaction: Azobisisobutyronitrile is added to the prepolymer solution, wherein the molar ratio of azobisisobutyronitrile to 4-cyano-4-[(dodecylthiocarbonyl)thio]valerate is 1:5 to 1:10, and the reaction is carried out in an oil bath at 65-70°C for 22-30 hours, with nitrogen protection and stirring during the reaction.

[0060] S6 Reaction Quenching: Turn off heating and stirring, allow the reaction solution to cool naturally to room temperature, and add anisole solution to quench the reaction. The solvent of the anisole solution is anhydrous tetrahydrofuran, to obtain a copolymer solution.

[0061] S7 Post-precipitation treatment: Pre-cool the precipitant to -18~-20℃, add the copolymer solution dropwise to the pre-cooled precipitant at a rate of 1-2 drops / s, the volume ratio of the copolymer solution to the precipitant is 1:10~1:100, and stir at a speed of 200-300 rpm to generate precipitate; after the addition is complete, continue stirring for 10~60 min to ensure complete precipitation, collect the precipitate and wash and dry it to obtain the polyoxyethylene block copolymer containing carborane hard segments. Example 1

[0062] The implementation process of this embodiment 1 is in accordance with the technical solution in the specific embodiment. The process of preparing activated PEO segments and hard segment monomers in S1-S3 is consistent with the specific embodiment. Only the material ratio and operating conditions in S4-S7 are specifically selected and limited. The specific implementation is as follows.

[0063] S4 prepolymer: Prepare PEO-macro-RAFT: 1g (approximately 0.111mmol), where n of PEO is 200, M... nThe monomer LiCAr-MA (9000 g) and 0.345 g (approximately 1.00 mmol) of lithium-o-decapod borane methyl propionate were dissolved in 10 mL of anhydrous toluene (H₂O < 50 ppm) and placed in a dry Schlenk reaction flask. After freezing with liquid nitrogen, the mixture was evacuated and backfilled with nitrogen. This process was repeated three times.

[0064] S5 polymerization reaction: Initiator azobisisobutyronitrile (AIBN) 3.0 mg (approximately 0.018 mmol) was added, nitrogen gas was introduced for protection, and the reaction was carried out in an oil bath at 70 °C with stirring for 24 h. During this period, 1 mL of sample was taken every 4 h using a syringe for GPC analysis to monitor molecular weight growth and dispersion coefficient, with a target control of Đ≤1.15.

[0065] S6 reaction quenching: Turn off heating and stirring, allow the reaction solution to cool naturally to room temperature, add a small amount of anisole solution to quench the free radicals, and obtain the copolymer solution.

[0066] S7 Precipitation Post-treatment: Add the copolymer solution dropwise at a rate of 1-2 drops / s to 50 mL of anhydrous diethyl ether pre-cooled at -20℃, while stirring at a rate of 200-300 rpm to generate a white precipitate; after the addition is complete, continue stirring for 10-60 min to ensure complete precipitation.

[0067] After collecting the precipitate by filtration using a Buchner funnel and filter paper with a pore size of 0.45 μm, the precipitate was washed three times with cold diethyl ether. The precipitate was then placed in a petri dish and dried in a vacuum drying oven at 25 °C and 0.1 mbar to obtain the polyoxyethylene block copolymer containing carborane hard segments of this application.

[0068] The obtained poly(ethylene oxide) block copolymer containing carborane hard segments was subjected to relevant performance tests, and the results are as follows: The number-average molecular weight M of the copolymer was obtained by GPC testing in tetrahydrofuran (THF) mobile phase. n The weight ratio of PEO soft segments to P-LiCAr-MA carborane hard segments in the copolymer is approximately 70:30.

[0069] The obtained polyoxyethylene block copolymer containing carborane hard segments was used to prepare an electrolyte film. The relevant performance tests of the film were carried out. The test items, methods and results are shown in Table 1 below. The results show that the copolymer prepared in Example 1 has good performance and can be used as a solid lithium battery separator.

[0070] Thin film preparation method: The copolymer is dissolved in THF, cast onto a PTFE template, and the film thickness is 100 μm after drying.

[0071] Table 1. Performance test results of the electrolyte film in Example 1

[0072] Example 2

[0073] The implementation process of this embodiment 2 is the same as the technical solution in the specific embodiment. The process of preparing activated PEO segments and hard segment monomers in S1-S3 is consistent with the specific embodiment. Only the material ratio and operating conditions in S4-S7 are specifically selected and limited. The specific implementation is as follows.

[0074] S4 prepolymer: Prepare PEO-macro-RAFT: 1g (approximately 0.147mmol), where n of PEO is 150, M... n The concentration of 6800 and the monomer LiCAr-MA (lithium-o-decapod carborane methylpropionate): 0.480 g (approximately 1.39 mmol) were dissolved in 10 mL of anhydrous toluene (H₂O < 50 ppm) and placed in a dry Schlenk reaction flask. After freezing with liquid nitrogen, a vacuum was drawn and nitrogen was backfilled. This process was repeated twice.

[0075] S5 polymerization reaction: Add initiator azobisisobutyronitrile (AIBN): 4.5 mg (approximately 0.027 mmol), introduce nitrogen protection, place in an oil bath at 65°C and stir for 30 h, extend the polymerization time to obtain a higher hard segment ratio.

[0076] S6 reaction quenching: Turn off heating and stirring, allow the reaction solution to cool naturally to room temperature, add a small amount of anisole solution to quench the free radicals, and obtain the copolymer solution.

[0077] S7 Precipitation Post-treatment: Add the copolymer solution dropwise at a rate of 1-2 drops / s to 50 mL of anhydrous diethyl ether pre-cooled at -18℃, while stirring at a rate of 200-300 rpm to generate a white precipitate; after the addition is complete, continue stirring for 10-60 min to ensure complete precipitation.

[0078] After collecting the precipitate by filtration using a Buchner funnel and filter paper with a pore size of 0.45 μm, the precipitate was washed with cold diethyl ether until the conductivity test was not affected by residual monomers. The precipitate was then placed in a petri dish and dried in a vacuum drying oven at 25 °C and 0.1 mbar to obtain the polyoxyethylene block copolymer containing carborane hard segments of this application.

[0079] The obtained poly(ethylene oxide) block copolymer containing carborane hard segments was subjected to relevant performance tests, and the results are as follows: The number-average molecular weight M of the copolymer was obtained by GPC testing in tetrahydrofuran (THF) mobile phase. n The value is approximately 13,500; NMR analysis shows that the content of P-LiCAr-MA carborane hard segments in the copolymer is approximately 38%.

[0080] The obtained polyoxyethylene block copolymer containing carborane hard segments was used to prepare an electrolyte film. The relevant performance tests of the film were carried out. The test items, methods and results are shown in Table 2 below. The results show that the copolymer prepared in Example 2 has good performance, high mechanical strength and is suitable for high-rate lithium batteries.

[0081] Thin film preparation method: The copolymer is dissolved in THF, cast onto a PTFE template, and the film thickness is 100 μm after drying.

[0082] Table 2. Performance test results of the electrolyte film in Example 2

[0083] Example 3

[0084] The implementation process of this embodiment 3 is in accordance with the technical solution in the specific embodiment. The process of preparing activated PEO segments and hard segment monomers in S1-S3 is consistent with the specific embodiment. Only the material ratio and operating conditions in S4-S7 are specifically selected and limited. The specific implementation is as follows.

[0085] S4 prepolymer: Prepare PEO-macro-RAFT: 0.90g, where n of PEO is 180, M... n The concentration was 8000, and 0.400 g of lithium-o-decapod carborane methyl propionate monomer LiCAr-MA was dissolved in a mixed solvent of toluene and THF (anhydrous, volume ratio 7:3): 12 mL, and placed in a dry Schlenk reaction flask. After freezing with liquid nitrogen, a vacuum was drawn and nitrogen was backfilled. The above operation was repeated three times.

[0086] S5 polymerization reaction: Add initiator azobisisobutyronitrile (AIBN): 3.0 mg (approximately 0.018 mmol), introduce nitrogen protection, and stir in an oil bath at 68°C for 22 h.

[0087] S6 reaction quenching: Turn off heating and stirring, allow the reaction solution to cool naturally to room temperature, add a small amount of anisole solution to quench the free radicals, and obtain the copolymer solution.

[0088] S7 Precipitation Post-treatment: Add the copolymer solution dropwise at a rate of 1-2 drops / s to 50 mL of anhydrous hexane pre-cooled at -20℃, ensuring that the hard segments are insoluble and that precipitation is complete. Stir at 200-300 rpm during this process to generate a white precipitate. After the addition is complete, continue stirring for 10-60 min to ensure complete precipitation.

[0089] After collecting the precipitate by centrifugation, it was washed with cold hexane, placed in a petri dish, and dried in a vacuum drying oven at 25°C and 0.1 mbar to obtain the polyoxyethylene block copolymer containing carborane hard segments of this application.

[0090] The obtained poly(ethylene oxide) block copolymer containing carborane hard segments was subjected to relevant performance tests, and the results are as follows: The number-average molecular weight M of the copolymer was obtained by GPC testing in tetrahydrofuran (THF) mobile phase. n The content of P-LiCAr-MA carborane hard segments in the copolymer is approximately 32%.

[0091] The obtained polyoxyethylene block copolymer containing carborane hard segments was used to prepare an electrolyte film. The relevant performance tests of the film were carried out. The test items, methods and results are shown in Table 3 below. The results show that the copolymer prepared in Example 3 has good performance and can be used as a solid lithium battery separator.

[0092] Thin film preparation method: The copolymer is dissolved in THF, cast onto a PTFE template, and the film thickness is 100 μm after drying.

[0093] Table 3. Performance test results of the electrolyte film in Example 3

[0094]

[0095] The above description is merely a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the concept described herein through the above teachings or related technologies or knowledge. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. A poly(ethylene oxide)-based block copolymer containing a carborane hard segment, characterized in that, PEO-b-P-LiCAr-MA, including soft segment PEO at the head and hard segment P-LiCAr-MA connected with the soft segment, the soft segment is polyethylene oxide, the general structure is: [CH2-CH2-O] n , n=100-600, the hard segment is poly(lithium-o-ten top carborane methyl propionate), the general structure is: [-CH2-C(CH3)(COO-CH2-C2B 10 H 11 -Li + )] m , m=9-90, the hard segment accounts for 25~35% of the total weight of the block copolymer.

2. The poly(ethylene oxide)-based block copolymer containing a carborane hard segment according to claim 1, characterized in that, The molar ratio of oxirane monomers in the soft segment to weakly coordinating lithium ions in the hard segment is: EO:Li + =7~11∶1.

3. The poly(ethylene oxide)-based block copolymer containing a carborane hard segment according to claim 1, wherein, The number average molecular weight M of the polyalkylene oxide in the soft segment n = 4405 - 26430.

4. A process for the preparation of a poly(ethylene oxide) based block copolymer containing carborane hard segments as claimed in any one of claims 1 to 3, characterised in that, The method comprises the following steps: S1 chain transfer agent activation: 4-cyano-4-[(dodecylthiocarbonyl)thio] pentanoic acid is dissolved in anhydrous dichloromethane at a concentration of 1-10 mg / mL, dicyclohexyl carbodiimide and 4-dimethylamino pyridine are added, and stirring is carried out under an ice water bath at 0-5°C for 30-120 min, the molar ratio of the 4-cyano-4-[(dodecylthiocarbonyl)thio] pentanoic acid, the dicyclohexyl carbodiimide and the 4-dimethylamino pyridine is 1:(1.0-1.5):(0.05-0.2), and an active O-acyl isourea intermediate-containing chain transfer solution is generated; S2 activated polyethylene oxide: polyethylene oxide is dissolved in anhydrous tetrahydrofuran, and the chain transfer solution is added, and reaction is carried out at room temperature under nitrogen protection for 1-24 h, and an activated polyethylene oxide intermediate PEO-macro-RAFT is obtained, the molar ratio of the terminal hydroxyl group of the polyethylene oxide and the 4-cyano-4-[(dodecylthiocarbonyl)thio] pentanoic acid is 1:1.2-2.0; S3 preparation of hard segment monomer: take lithium borane Li2C2B 10 H 10 Nucleophilic substitution reaction with chloromethyl methacrylate Cl-CH2-MA in anhydrous tetrahydrofuran, the molar ratio of the two: Li2C2B 10 H 10 : Cl-CH2-MA = 1:1.1~1.2, the initial reaction temperature is-10~-20℃, then rise to room temperature and continue to stir under inert gas protection reaction 2-4h, until the reaction is complete to get crude monomer; then add sodium carbonate solution under ice bath to replace lithium salt, the molar ratio of the crude monomer and sodium carbonate is 1:1.2~2, rise to room temperature and stir for 1-2h, until the lithium carbonate Li2CO3 precipitate completely precipitate, after filtration to get lithium-ortho-deca top carbon borane methyl propionate monomer LiCAr-MA; S4 prepolymerization: the polyethylene oxide intermediate PEO-macro-RAFT and the lithium-o-ten carboborane methyl propionate monomer LiCAr-MA are dissolved in anhydrous organic solvent and placed in a Schlenk reaction bottle, the concentration of the polyethylene oxide intermediate PEO-macro-RAFT is 10-50 mg / mL, the concentration of the lithium-o-ten carboborane methyl propionate monomer LiCAr-MA is 0.1-1 M, the molar ratio of the polyethylene oxide intermediate PEO-macro-RAFT and the lithium-o-ten carboborane methyl propionate monomer LiCAr-MA is 1:1-1:100, vacuum is drawn after being frozen in liquid nitrogen at-190--196°C for 3-5 min, and nitrogen is backfilled, and the vacuum drawing and nitrogen backfilling operation is repeated 1-3 times, and a prepolymerization solution is obtained; S5 polymerization reaction: azobisisobutyronitrile is added to the prepolymerization solution, the molar ratio of the azobisisobutyronitrile and the 4-cyano-4-[(dodecylthiocarbonyl)thio] pentanoic acid is 1:5-1:10, reaction is carried out in an oil bath at 65-70°C for 22-30 h, nitrogen protection and stirring are used during the reaction; S6 reaction quenching: heating and stirring are turned off, the reaction solution is naturally cooled to room temperature, and anisole solution is added to quench the reaction, the solvent of the anisole solution is anhydrous tetrahydrofuran, and a copolymer solution is obtained; S7 post-treatment after precipitation: a precipitant is pre-cooled to-18--20°C, the copolymer solution is added to the pre-cooled precipitant at a speed of 1-2 drops / s, the volume ratio of the copolymer solution and the precipitant is 1:10-1:100, stirring is carried out at a speed of 200-300 rpm during the process, and a precipitate is generated; after the addition is completed, stirring is continued for 10-60 min to make the precipitate complete, the precipitate is collected and washed and dried, and the polyethylene oxide-based block copolymer containing a carboborane hard segment is obtained.

5. A process for the preparation of a poly(ethylene oxide) based block copolymer containing carborane hard segments according to claim 4, characterized in that, The anhydrous organic solvent used for dissolving the polyethylene oxide intermediate PEO-macro-RAFT and the lithium-o-benzenesulfonylcarbanion methyl propionate monomer LiCAr-MA in S4 is toluene and / or tetrahydrofuran.

6. A process for the preparation of a poly(ethylene oxide) based block copolymer containing carborane hard segments according to claim 4, characterized in that, The vacuum extraction in S4 includes controlling the vacuum degree in the Schlenk reaction bottle ≤ 0.1 mbar and maintaining for 5-10 min; the backfilling of nitrogen includes filling nitrogen with purity ≥ 99.999% into the Schlenk reaction bottle and controlling the pressure in the bottle at 1.05-1.1 atm. The precipitant in S7 is anhydrous diethyl ether or anhydrous n-hexane.

7. A process for the preparation of a poly(ethylene oxide) based block copolymer containing a carborane hard segment according to claim 4, characterized in that, The collection of precipitate in S7 includes: using a Buchner funnel and matching filter paper with a pore size of 0.01-0.45 μm to perform suction filtration collection, or centrifuging at a speed of 3000-10000 rpm for 5-60 min to collect.

8. A process for the preparation of a poly(ethylene oxide) based block copolymer containing carborane hard segments according to claim 4, characterized in that, The drying in S7 includes placing the collected solid precipitate on a watch glass and placing it in a vacuum drying oven, drying at 25-60℃, vacuum degree 0.01-0.1 mbar for 12-36 h.

9. A process for the preparation of a poly(ethylene oxide) based block copolymer containing a carborane hard segment according to claim 4, characterized in that, A polyethylene oxide-based block copolymer containing a carborane hard segment as claimed in any one of claims 1-3 is used as a material to obtain.

10. A solid state electrolyte membrane, characterized by, ​

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