A polymer having a v-shaped polyether side chain and a method for preparing the same as a polymer solid-state electrolyte

Abstract

The application belongs to the technical field of functional polymers, and particularly relates to synthesis of a polymer with V-shaped polyether side chains and a preparation method of the polymer as a polymer solid-state electrolyte. The polymer is or the structure of the side chain R is n and m are polymerization degrees, x and y are positive integers of 1-30, R1-R and R2 are structural units constituting the polymer, the structure of R1-R does not contain lithium ions, and the structure of R2 contains lithium ions. The side group R is a heteroatom-containing polyether with a V-shaped structure, the oxirane chain segment in the structure can complex and decomplex with lithium ions, plays a role of dissolving and conducting lithium salt, and R3 is a multivalent element such as P, N, C and Si. The application links short-chain polyoxirane with high density to the polymer side chain, breaks the long-range ordered regular structure of the polymer, gives the polymer the characteristics of low crystallinity and flexible movement of the side chain, improves the free volume of lithium ions which can be transported and migrated, and further improves the ionic conductivity.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of functional polymers, and particularly relates to a polymer with V-shaped polyether side chains and a preparation method of the polymer as a polymer solid-state electrolyte. BACKGROUND

[0002] Electrochemical energy storage represented by lithium ion batteries has the characteristics of high energy density, long service life, no heavy metal pollution, and environmental friendliness, and is an important means to replace traditional fossil energy and realize sustainable development and green energy storage. Lithium ion batteries have high energy density, can be quickly charged and discharged, have relatively low self-discharge, high efficiency, and light weight, and have become the main power source for electronic communication devices, power grid energy storage, electric vehicles, and other devices and instruments. With the rapid development of these industries, people have higher demands for batteries with high energy density and high safety. However, its actual application still faces great challenges. This is mainly because the commonly used liquid electrolyte is mostly ester and ether organic matter, which is not compatible with high-energy electrode materials, is prone to side reactions, has inherent shortcomings such as easy leakage and high-temperature volatilization failure, is prone to the generation of lithium dendrites, and increases the risk of battery thermal runaway. Compared with liquid electrolyte, solid-state electrolyte has the characteristics of not easy to diffuse, not easy to volatilize and burn, high thermal stability, chemical stability and electrochemical stability, and good compatibility with electrode materials, which is expected to improve the interface stability between electrolyte and electrode material and the safety of the battery. Therefore, using solid-state electrolyte to replace traditional liquid electrolyte is the best solution to solve thermal runaway and improve electrode compatibility, and is the inevitable choice for the realization and practical application of high-energy batteries.

[0003] Commonly used polymer solid electrolytes include polyethylene oxide (PEO) homopolymer, PEO copolymer (including block, graft and hyperbranched types) and other polar polymers such as aliphatic polyester, polyacrylonitrile, polysiloxane, polyphosphazene, etc. Among them, PEO homopolymer is the earliest, most mature and most commonly used matrix in polymer electrolyte system research, with many advantages such as low glass transition temperature and strong lithium salt solubility. However, the PEO polymer chain is relatively regular, the interchain interaction is strong, and thus it shows high crystallinity, which makes the ionic conductivity of PEO at room temperature relatively low, limiting its application in solid-state electrolytes. In order to improve its crystallinity, various methods such as blending, copolymerization, inorganic doping and structure design can be used, among which changing the polymer structure and the arrangement of polyethylene oxide segments in the polymer structure is the most common and easy to implement method. Existing PEO-type polymer solid electrolyte systems include (1) PEO homopolymer directly blended with lithium salt and (2) various block copolymers containing PEO and (3) various grafted polymer electrolytes prepared by copolymerization of new PEO-containing monomers such as polyethoxymethyl methacrylate (PEGMA) and (4) various polymers grafted and hyperbranched with short-chain polyethylene oxide, among which (2), (3) and (4) are specific forms of structure design to improve crystallinity.

[0004] Among the above-mentioned polymer electrolytes, the ionic conductivity of the structure containing long-chain polyethylene oxide is significantly lower than that of the polymer electrolyte containing short-chain polyethylene oxide, which is due to the advantages of short-chain polyethylene oxide structure in terms of chain flexibility and movement ability. Although longer polyethylene oxide segments have stronger lithium salt solubility, their structure is relatively regular, but this long-range ordered and closely packed structure mostly leads to high crystallinity, showing lower amorphous region proportion, weaker segment movement ability and poorer flexibility, which is not conducive to the stretching, curling and peristalsis of polymer segments, reducing the free volume available for lithium ion transport and migration, thus greatly reducing the lithium ion transport rate. In addition, short-chain ethylene oxide in branched form has strong free swing and peristaltic ability, and also plays a role in plasticizing small molecules to some extent, not only effectively breaking the regular structure of the polymer, reducing the glass transition temperature of the system, increasing the free volume, but also helping to improve the dimensional stability of the polymer and facilitate film formation. Therefore, the polymer electrolyte with short-chain polyethylene oxide grafted on the side chain has obvious advantages in all aspects.

[0005] In the existing polymer electrolyte system, polyphosphates and polyphosphazenes have various topological structures, and are the main force for preparing side chain branched short chain polyethylene oxide type polymer electrolyte. The existing technology uses the reactivity of phosphorus oxychloride to connect TEG triethylene glycol monomethyl ether segment and hydroxyethyl acrylate to prepare a phosphonate monomer containing short chain polyethylene oxide in the side chain. However, the synthesis and separation technology of the monomer has relatively high requirements, it is difficult to control the reaction degree of TEG and phosphorus oxychloride, the product separation and purification is troublesome, the synthesis is difficult, and the branching and crosslinking degree is too high, which is not conducive to the dissolution and movement of lithium ions. Another phosphorus-containing polymer that can successfully graft short chain polyethylene oxide is polyphosphazene, and its representative is MEEP poly(bis(2-(2-methoxyethoxy)ethoxy) phosphazene). The ether-containing polyphosphazene with a shorter polyethylene oxide segment as a side group has strong flexibility and segment movement ability under the premise of maintaining the inherent flexibility of polyphosphazene and the function of polyether dissolving lithium salt, which is conducive to the rapid conduction of lithium salt at low temperature, and is considered as an ideal polymer matrix of solid-state electrolyte. However, MEEP still has some defects. First, from the synthesis, the synthesis and post-modification of polyphosphazene are harsh to reaction conditions, and it is difficult to obtain a product with a relatively single structure. In addition, similar to polyphosphates, the hydrolysis stability of polyphosphazene still needs to be improved, and it may have problems such as side group rupture and P-N bond degradation on the main chain under water conditions. Second, due to the flexible structure of polyphosphazene itself, the grafting of flexible polyethylene oxide segment makes MEEP exhibit poor mechanical strength and dimensional stability and high viscosity, which is not conducive to film formation. Third, the structure of MEEP contains a large amount of N element, and this heteroatom also has coordination ability with lithium ions, which leads to the competition between N on the main chain and O in the side chain for lithium ions, limits the movement of lithium ions along the polyethylene oxide side chain, and reduces the ion migration rate to a certain extent.

[0006] In summary, the structure of the polymer solid-state electrolyte still needs to be further improved and developed, and a new type of polymer solid-state electrolyte with high grafting density of side chain and flexible short chain polyethylene oxide needs to be developed. SUMMARY

[0007] The purpose of the present application is to provide a polymer with V-shaped polyether side chain and a preparation method thereof as a polymer solid-state electrolyte, which improves the polymer chain segment movement ability by the high grafting density of V-shaped short chain polyethylene oxide, increases the free volume of movable lithium ions, and thus improves the comprehensive performance of the solid-state electrolyte.

[0008] To achieve the above purpose, the present application provides a polymer for solid-state electrolyte, comprising The structure of the side chain R is

[0009] wherein n and m are the degree of polymerization, x and y are both positive integers from 1 to 30, R1-R and R2 are structural units constituting the polymer, the structure of R1-R does not contain lithium salt, and the structure of R2 contains lithium salt. The side group R is a heteroatom-containing polyether with a V-shaped structure, the ethylene oxide segment in the structure can complex and decomplex with lithium ions, playing a role in dissolving and conducting lithium salt, and R3 is a multivalent element such as P, N, C, Si, etc., which is used to synthesize the V-shaped polyether side chain. Specifically, when R3 is a different element, the structure of the side chain R is (wherein R4 is an arbitrary substituent, such as hydrogen, halogen, or a carbon chain substituent, preferably hydrogen, halogen, hydroxyl, a carbon chain substituent with 1-36 carbon atoms, or a derivative thereof, the carbon chain substituent is an aliphatic substituent or an aromatic substituent, the aliphatic substituent is an alkyl group, an alkenyl group, an alkoxy group, etc., and the number of carbon atoms is preferably 1-18):

[0010]

[0011] Further, the main chain of the polymer is one or more of a carbon chain type polymer (such as polystyrene, polymethacrylate, polyacrylamide, polyethylene, polypropylene, polybutylene, etc.), a hetero-chain type polymer (such as polyethylene oxide, polysiloxane, polycarbonate, polyphosphate, etc.), or an inorganic polymer (polyphosphazene, etc.); the molar content of the repeating unit R1-R is 1-100%, for example, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, etc., where the molar content refers to the molar ratio of the content of the repeating unit R1-R to the content of the polymerization unit of the polymer, and a molar content of 100% indicates that each polymerization unit is connected to a structure R. The polymer can also include other copolymerization units, i.e., the molar content of the structure R1-R is less than 100%, and the polymer is multifunctional through copolymerization.

[0012] Further, the polymerization monomer R1-R is selected from one or more of the following structural formulas:

[0013]

[0014] Further, the R1-R is obtained by reacting a halide of the polymerization monomer R1 with a hydroxymethyl compound containing a multivalent element, specifically including the following steps:

[0015] S1, reacting the halide of the polymerization monomer R1 with a hydroxymethyl compound to obtain one of the following products:

[0016]

[0017] S2, etherifying the product of step S1 with to obtain the R1-R; wherein R3 is Br or p-toluenesulfonyl (OTs).

[0018] Further, step S2 is carried out under alkaline conditions, and the catalysts used include one or more of benzyltriethylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium hydrogen sulfate, trioctylmethylammonium chloride, dodecyltrimethylammonium chloride, tetradecyltrimethylammonium chloride, crown ether, and polyethylene glycol;

[0019] When water is used as the solvent, the base used is one or more of NaOH, KOH, LiOH, K2CO3, Na2CO3, Li2CO3, potassium tert-butoxide, and quaternary ammonium bases such as tetramethylammonium hydroxide; or when an organic solvent is used, the base used is one or more of sodium methoxide, NaH, LiH, NaOH, KOH, LiOH, K2CO3, Na2CO3, Li2CO3, potassium tert-butoxide, and quaternary ammonium bases such as tetramethylammonium hydroxide.

[0020] Further, the polymer is obtained by step-by-step polymerization or chain polymerization of the polymerized monomers.

[0021] The present application also provides a polymer solid-state electrolyte. An additional lithium salt is required as a lithium source, and the polymer solid-state electrolyte can be used only after blending, R2 is a lithium source, and the polymer solid-state electrolyte can be used directly. Depending on the structure and composition of the polymer, the types of solid-state electrolytes that can be formed are as follows:

[0022] ① + Small molecule lithium salt - blended to form a double-ion conductor type polymer solid-state electrolyte;

[0023] ② + Macromolecular lithium salt - blended to form a single-ion conductor type polymer solid-state electrolyte;

[0024] ③ - Directly obtain a single-ion conductor type polymer solid-state electrolyte.

[0025] Further, when the lithium salt is a small molecule lithium salt, a double-ion conductor type polymer solid-state electrolyte is obtained by compounding with a polymer, and when the lithium salt is a macromolecular lithium salt (including blending and copolymerization), a single-ion conductor type polymer solid-state electrolyte is obtained by compounding with a homopolymer. The small molecule lithium salt includes one or more of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, and lithium bis(trifluoromethylsulfonyl)imide; the macromolecular lithium salt includes one or more of the following structural formulas:

[0026]

[0027] wherein m1 and n1 are both positive integers, representing the number of repeating structural units in the polymer structure; preferably a positive integer of 1-30.

[0028] Preferably, the solid-state electrolyte is a copolymer obtained by monomer chemical copolymerization and polymer post-modification, and is selected from one or more of the following structural formulas, including but not limited to polymers containing various anion groups such as carboxylate-COO - , sulfonate-SO3 - , sulfonamide-SO2N (-) SO2- and borate-B -

[0029]

[0030] Wherein a, b and c are positive integers, representing the number of repeating structural units in the polymer structure.

[0031] The present application improves the proportion of amorphous region, segment motion ability and flexibility of the polymer, increases the free volume of lithium ion transmission and migration, promotes the migration of lithium ion in the polymer and thus improves the ionic conductivity by grafting high-density short-chain polyethylene oxide on the side chain of the polymer, using the advantages of low crystallinity, free volume, segment flexibility and motion ability, etc. The shorter polyether side chain in the structure has stronger segment motion ability than the long-chain polyether, and plays a plasticizing role to some extent, which is beneficial to weaken the interaction between molecules, break the regular structure of the polymer and thus reduce the glass transition temperature and crystallinity of the polymer, and improve the overall flexibility of the polymer. More importantly, the V-shaped polyether side chain can form a structure similar to open-chain crown ether by two sufficiently close ethylene oxide segments, which constitutes the center of lithium ion dissolution, complexation, decomplexation and migration. In addition, the binding strength between the V-shaped polyether side chain and lithium ion is weaker than that of the closed crown ether, so it does not limit the movement of lithium ion, but can promote the transmission of lithium ion through the rapid motion of short-chain polyethylene oxide, thereby improving the performance of the polymer solid-state electrolyte.

[0032] The present application also provides a preparation method of the polymer solid-state electrolyte, characterized in that it comprises: copolymerizing the polymer monomer of the solid-state electrolyte polymer and the polymer monomer of the macromolecular lithium salt in the polymer solid-state electrolyte as a comonomer to obtain the polymer solid-state electrolyte.

[0033] Further, the molar ratio of the polymer monomer of the solid-state electrolyte polymer and the polymer monomer of the macromolecular lithium salt is (50:50) to (95:5);

[0034] And / or, the solvent used in the copolymerization reaction is a mixed solvent composed of one or more of DMF, DMSO, DMAc, methanol, ethanol and water;

[0035] ​And / or, the initiator used in the copolymerization reaction is an azo initiator or a persulfate-sodium bisulfite system.

[0036] In some embodiments, taking polystyrene as an example, the preparation process is as shown in the following formula. Figure 9

[0037] The polymeric monomer is obtained by reacting p-vinylbenzyl chloride (when other polymer segments are used, the corresponding monomer halide can be selected accordingly) and tris(hydroxymethyl) phosphine, and then oxidizing and etherifying; the free radical homopolymerization is carried out to obtain a polymer solid electrolyte by blending with a lithium salt or by free radical copolymerization with a monomer containing a lithium salt.

[0038] The application further provides a preparation method of the polymer solid electrolyte film, which comprises dissolving the polymer solid electrolyte in a solvent, and then solidifying the polymer solid electrolyte into a film by solvent evaporation to obtain the polymer solid electrolyte film.

[0039] Overall, compared with the prior art, the above technical solutions conceived by the application mainly have the following technical advantages:

[0040] 1. The polymer with V-shaped polyether side chains provided by the application has a short-chain polyethylene oxide with high grafting density in the structure, which improves the polymer segment movement ability, increases the movable free volume of lithium ions, and effectively reduces the crystallinity of the system.

[0041] 2. The main chain of the polymer is a carbon chain type polymer (such as polystyrene, polymethacrylate, etc.), a hetero-chain type polymer (such as polyethylene oxide, polysiloxane, etc.), or an inorganic polymer (polyphosphazene, etc.), two short-chain polyether side chains are introduced by one-step Williamson synthesis, forming a structure similar to an open-chain crown ether, which has the characteristics of simple synthesis method, diverse structure, high stability, etc. The prepared polymer has the ability to dissolve metal ions (such as lithium ions, sodium ions, potassium ions, etc.), and is expected to be used as a polymer solid electrolyte.

[0042] 3. The phosphorus-carbon bond is introduced into the structure, which has high stability and is difficult to introduce by many methods. The introduction of phosphorus elements can enhance the thermal stability of the system, and the phosphine oxygen bond O=P also improves the lithium salt solubility and the flame retardant performance of the polymer electrolyte to a certain extent.

[0043] 4. The V-shaped polyether side chain is introduced by using the multivalent nature of the phosphorus-containing compound, forming a structure similar to a crown ether but not closed, which has high solubility for lithium ions without limiting the movement of lithium ions, and the system has low crystallinity and low glass transition temperature. The high thermal stability and dimensional stability, good lithium salt solubility, and low glass transition temperature of the application make it suitable for polymer solid electrolytes. BRIEF DESCRIPTION OF DRAWINGS

[0044] ​Figure 1 Hydrogen and phosphorus nuclear magnetic resonance spectra of monomer VBzBHPO-1EO, (b) carbon nuclear magnetic resonance spectrum of monomer VBzBHPO-1EO (DMSO-d6);

[0045] Figure 2 High resolution mass spectrum of monomer VBzBHPO-1EO;

[0046] Figure 3 Hydrogen and phosphorus nuclear magnetic resonance spectra of phosphorus-containing polymer solid-state electrolyte film with V-shaped polyether side chains prepared in Example One (DMSO-d6);

[0047] Figure 4 DSC curve of phosphorus-containing polymer solid-state electrolyte film with V-shaped polyether side chains prepared in Example One, with glass transition temperature T g = -28.6°C;

[0048] Figure 5 TGA-DTG thermogravimetric curve of phosphorus-containing polymer solid-state electrolyte film with V-shaped polyether side chains prepared in Example One;

[0049] Figure 6 EIS impedance diagram of phosphorus-containing polymer solid-state electrolyte film with V-shaped polyether side chains prepared in Example One measured at different temperatures;

[0050] Figure 7 EIS impedance diagram of phosphorus-containing polymer solid-state electrolyte film with V-shaped polyether side chains prepared in Example Twelve measured at different temperatures;

[0051] Figure 8 EIS impedance diagram of phosphorus-containing polymer solid-state electrolyte film with V-shaped polyether side chains prepared in Example Thirteen measured at different temperatures;

[0052] Figure 9 Preparation flow chart of phosphorus-containing polymer solid-state electrolyte of the present application. DETAILED DESCRIPTION

[0053] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail in conjunction with the following examples. It should be understood that the specific examples described herein are only used to explain the present application, and are not used to limit the present application. In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as they do not conflict with each other.

[0054] The application provides a polymer solid-state electrolyte with V-shaped polyether side chains and a preparation method thereof, and aims to improve the diversity of ether-containing polymer solid-state electrolyte structures. The application utilizes the multivalence of phosphorus elements, introduces two short-chain polyether side chains at one time through Williamson synthesis, forms a structure similar to an open-chain crown ether, provides a novel phosphorus-containing monomer with V-shaped polyether side chains, and has the characteristics of simple synthesis method, structural diversity, high stability and the like, and provides a novel phosphorus-containing polymer electrolyte with good performance for the practical application of a solid-state battery.

[0055] In the polymer solid-state electrolyte, the phosphorus-oxygen bond O=P(CH2OH)2 serves as a reaction site, and the nucleophilic substitution of the brominated short-chain polyether introduces the V-shaped polyether side chain. The phosphorus-oxygen bond O=P also improves the lithium salt solubility and the polymer electrolyte flame retardation performance to a certain extent. The ethylene oxide segment in the structure can complex and decomplex with lithium ions, providing the ability to dissolve and transport lithium salts. Compared with the existing PEO polyether-type polymer electrolyte, the structure has significant advantages, specifically, the shorter polyether side chain in the structure has stronger segment motion ability than the long-chain polyether, and at the same time, plays a plasticizing role to a certain extent, which is conducive to weakening the intermolecular interaction and thus reducing the glass transition temperature and crystallinity of the polymer, and improving the overall flexibility of the polymer. More importantly, although the V-shaped polyether side chain is similar in structure to a crown ether, after complexation with lithium ions, it does not limit the movement of lithium ions like the ring-closed structure of a crown ether, but can form an open-chain crown ether structure through two ethylene oxide segments close enough to each other, to build the center of lithium ion solubility, complexation, decomplexation and migration, and promote the transport of lithium ions through the rapid motion of the short-chain polyethylene oxide. In addition, the rigid structure of the benzene ring as the polymer backbone can also effectively improve the mechanical properties and thermal stability of the polymer solid-state electrolyte.

[0056] The following is described in detail through specific examples, taking P-C type as an example.

[0057] 1. Preparation of core monomer

[0058] In the synthesis method of the monomer, the Williamson synthesis method is selected, and the hydroxyl group on VBzBHPO is used for SN2 bimolecular nucleophilic substitution with an ether-containing brominated compound to prepare a novel monomer containing an ethylene oxide structure. VBzBHPO refers to the compound shown below:

[0059]

[0060] (1) Formula when the solvent is water

[0061] The type of base used: NaOH, KOH, LiOH, K2CO3, Na2CO3, Li2CO3, potassium tert-butoxide, and quaternary ammonium bases such as tetramethylammonium hydroxide;

[0062] Amount and concentration of base: 2-6 eq of monomer; concentration: 5-40% by mass;

[0063] Type and amount of phase transfer catalyst: benzyltriethylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium hydrogen sulfate, trioctylmethylammonium chloride, dodecyltrimethylammonium chloride, tetradecyltrimethylammonium chloride, crown ether, polyethylene glycol;

[0064] The solvent used in the basic solution is water, and the base used is NaOH, KOH, LiOH, K2CO3, Na2CO3, Li2CO3, etc.; the amount is 0.25-15 mol% of the monomer;

[0065] Type and amount of polymerization inhibitor: 2,2,6,6-tetramethylpiperidine-1-oxyl radical TEMPO; amount: 1 ‰-10 mol ‰;

[0066] Temperature: 40-60°C;

[0067] Time: 12-72 h.

[0068] (2) Formulation when the solvent is THF (type and amount of phase transfer catalyst and polymerization inhibitor are the same as in the 1-1 formulation)

[0069] Type of base used: sodium methoxide, NaH, LiH, NaOH, KOH, LiOH, K2CO3, Na2CO3, Li2CO3, potassium tert-butoxide, and quaternary ammonium bases such as tetramethylammonium hydroxide;

[0070] Amount of base: 2-6 eq of monomer;

[0071] Monomer concentration: 0.05-1 mol / L;

[0072] Temperature: room temperature-70°C reflux;

[0073] Time: 12-72 h.

[0074] (3) Formulation when the solvent is DMSO / DMF / DMAc (type and amount of phase transfer catalyst and polymerization inhibitor are the same as in the 1-1 formulation)

[0075] Type of base used: sodium methoxide, NaH, LiH, NaOH, KOH, LiOH, K2CO3, Na2CO3, Li2CO3, potassium tert-butoxide, and quaternary ammonium bases such as tetramethylammonium hydroxide;

[0076] Amount of base: 2-6 eq of monomer;

[0077] Monomer concentration: 0.05-1 mol / L;

[0078] Temperature: room temperature ~ 80℃;

[0079] Time: 12 ~ 72h.

[0080] Monomer synthesis and post-processing example-1 (take VBzBHPO-1EO as an example):

[0081]

[0082] ① Take sodium hydroxide (three times the equivalent of VBzBHPO) and prepare a 20% mass fraction of sodium hydroxide aqueous solution;

[0083] ② Add 1 mol% of VBzBHPO tetra-n-butylammonium bromide TBAB as the phase transfer catalyst of the system, and 1 mol% of TEMPO as the polymerization inhibitor of the system;

[0084] ③ Take VBzBHPO, stir until completely dissolved;

[0085] ④ Take 2-bromoethyl methyl ether (3.2 times the equivalent of VBzBHPO), and add it slowly in batches;

[0086] ⑤ 60℃ oil bath pot heating for 22h;

[0087] ⑥ Post-processing: after the reaction is completed, the upper layer is a light yellow oily liquid, and the lower layer is an aqueous phase, which is directly separated. The aqueous phase is extracted with DCM three times, and the organic phase is combined and washed with water three times, saturated brine three times, anhydrous sodium sulfate overnight, filtered and dried at room temperature to obtain a light yellow oily liquid, with a yield of 70-90%.

[0088] As Figure 1 and Figure 2 , the molecular weight of the monomer VBzBHPO-1EO is determined by high-resolution mass spectrometry in cation mode, and the characteristic ion fragments m / z=343.16 and m / z=365.14 correspond to [VBzBHPO-1EO+H] + and [VBzBHPO-1EO+Na] + , respectively, which is consistent with the theoretical molecular weight of VBzBHPO-1EO, which is 342.16.

[0089] Monomer synthesis and post-processing example-2 (take VBzBHPO-2EO as an example):

[0090]

[0091] ① Take VBzBHPO, add THF and stir until completely dissolved to prepare a 0.1 mol / L solution;

[0092] 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) as the polymerization inhibitor at 2 mol% of the monomer;

[0093] 3. Slowly add NaH (2.4 times the equivalent of VBzBHPO);

[0094] 4. Slowly add 1-bromo-2-(2-methoxyethoxy)ethane (3 times the equivalent of VBzBHPO) in batches under ice water bath condition;

[0095] 5. Heat at 40°C for 64 h;

[0096] 6. Post-treatment: After the reaction is completed, add a small amount of ethanol to quench the reaction, dry the solvent at room temperature, then dissolve in DCM, wash the organic phase with water three times, wash with saturated brine three times, dry with anhydrous sodium sulfate overnight, filter, and dry at room temperature to obtain a light yellow oily liquid with a yield of 70-90%.

[0097] Example 3 of monomer synthesis and post-treatment (take VBzBHPO-3EO as an example):

[0098]

[0099] 1. Weigh VBzBHPO and add stirring DMSO to completely dissolve to prepare a 1 mol / L solution;

[0100] 2. Add tetra-n-butylammonium bromide (TBAB) as the phase transfer catalyst at 1 mol% of VBzBHPO, and 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) as the polymerization inhibitor at 2 mol% of the monomer;

[0101] 3. Slowly add NaOH (5 times the equivalent of VBzBHPO);

[0102] 4. Slowly add diethylene glycol-2-bromoethyl methyl ether (5 times the equivalent of VBzBHPO) in batches under ice water bath condition;

[0103] 5. React at room temperature for 12 h;

[0104] 6. Post-treatment: Dilute the system with a large amount of DCM, wash with water three times to remove DMSO, excess NaOH, and other water-soluble impurities, wash with saturated brine three times, dry with anhydrous sodium sulfate overnight, filter, and dry at room temperature to obtain a light yellow oily liquid with a yield of 70-90%.

[0105] 2. Preparation of ion-conductor type polymer solid-state electrolyte

[0106] A single-ion conductor type polymer solid electrolyte is prepared in one step by copolymerization of monomers containing lithium ion conducting and dissolving lithium salt groups and monomers containing lithium source, to fix lithium ions on the polymer backbone. Specifically, VBzBHPO-nEO and 2-acrylamido-2-methylpropane sulfonic acid AMPS are used as comonomers, and an equivalent amount of LiOH-H2O is added to neutralize AMPS to form lithium sulfonate, wherein the molar ratio of VBzBHPO-nEO and AMPS is any ratio between 50:50 and 95:5. The copolymerization solvent is DMF, DMSO, DMAc, methanol, ethanol, water, and mixed solvents thereof in different proportions, and the monomer concentration is 0.1 g / mL to 0.3 g / mL; the initiator can be APS (ammonium persulfate), KPS (potassium persulfate), ACVA (azo dicyanovinyl acid), AIBN (azo diisobutyronitrile), ABVN (azo diisobutyronitrile), BPO (benzoyl peroxide), etc., and the amount is 0.2 mol% to 1 mol% of the total amount of monomers. After deoxygenation of the solution, polymerization is carried out under argon atmosphere for 24 h, and the polymerization temperature depends on the type of initiator used. If an azo initiator is used, the temperature is generally selected to be 60-80°C, and if a redox system such as persulfate-sodium bisulfite is used, a lower temperature of -10-40°C can be selected. After the reaction is completed, small molecules can be removed by solvent precipitation or dialysis, and the polymer solid electrolyte is obtained by drying at 80°C.

[0107] 3. Preparation of polymer electrolyte membrane

[0108] The preparation of the polymer electrolyte thin film is carried out by solvent evaporation method. The polymer solid electrolyte is dissolved in solvents such as ethanol, acetonitrile, water, DMF, DMSO, etc., and after evaporation at room temperature for 24 h, the temperature is raised for drying, so that the solvent is completely volatilized to form a uniform polymer electrolyte membrane.

[0109] 4. Assembly of stainless steel symmetric battery and EIS impedance test

[0110] The polymer electrolyte is assembled into a stainless steel symmetric CR2032 button cell in the order of positive shell-elastic sheet-stainless steel gasket-polymer solid electrolyte-stainless steel gasket-negative shell, and the electrochemical impedance of the button cell at different temperatures is tested using a CHI760E electrochemical workstation, and the Nyquist plot is drawn and the specific ion conductivity is calculated. The specific test conditions are: the frequency is 10 6 -0.1 Hz, the amplitude is 0.01-0.02 V, and the temperature is selected to be 50°C, 60°C, 70°C, 80°C, and 90°C. Before testing at each temperature, the temperature is kept constant in the oven for 1 h to ensure that the temperature inside and outside the battery is consistent.

[0111] A specific example of the preparation of a polymer electrolyte is as follows: (where AMPS is the monomer 2-acrylamido-2-methylpropane sulfonic acid, and LiSTFSI is the monomer lithium p-styrenesulfonate trifluoromethylsulfonimide)

[0112] Example 1

[0113] Taking the VBzBHPO-1EO prepared in the above Example-1 and AMPS as an example, the required raw materials for the preparation of a single-ion conductor type polymer solid electrolyte are shown in Table 1.

[0114] Table 1

[0115]

[0116] The specific steps are as follows:

[0117] 1. Measure 12.1 mL of DMF and 4.1 mL of H2O, prepare the mixed solvent and cool to room temperature;

[0118] 2. Weigh 0.64 g of AMPS, and add an equivalent amount of LiOH·H2O 0.1296 g to neutralize the AMPS into lithium sulfonate;

[0119] 3. Add 4.20 g of VBzBHPO-1EO monomer and 0.0254 g of initiator AIBN, stir until uniform and transparent;

[0120] 4. After removing oxygen in the solution for 30 min under argon, polymerize at 80°C for 24 h under argon atmosphere;

[0121] 5. After removing small molecules by dialysis bag (which can pass substances with a molecular weight of 3500), spin dry to constant weight, to obtain a polymer solid electrolyte with a number average molecular weight of 30,000 and a molecular weight distribution index of 2.4;

[0122] 6. The preparation of the polymer electrolyte film is carried out by solvent evaporation method. The polymer solid electrolyte is dissolved in ethanol to prepare a solution of 0.3 g / ml, which is dropped on a stainless steel gasket using a pipette gun. After volatilizing at room temperature for 24 h, gradually heating to 80°C for 24 h, the solvent is completely volatilized to form a transparent and uniform polymer electrolyte film with an average thickness of 242 um.

[0123] Example 2

[0124] Taking the VBzBHPO-1EO and AMPS copolymerization to prepare a single-ion conductor type polymer solid electrolyte as an example, the required raw materials are shown in Table 2.

[0125] Table 2

[0126] ​

[0127] The operation steps are the same as in Example 1, the number average molecular weight of the polymer is 40,000, the molecular weight distribution index is 2.5, and the average thickness after film formation is 174 um.

[0128] Example Three

[0129] The VBzBHPO-1EO and AMPS were copolymerized to prepare a single-ion conductor type polymer solid electrolyte, and the required raw materials are shown in Table 3.

[0130] Table 3

[0131]

[0132]

[0133] The operation steps are the same as in Example 1, the number average molecular weight of the polymer is 50,000, the molecular weight distribution index is 1.9, and the average thickness after film formation is 133 um.

[0134] Example Four

[0135] The VBzBHPO-2EO prepared in the above Example-2 and AMPS were copolymerized to prepare a single-ion conductor type polymer solid electrolyte, and the required raw materials are shown in Table 4.

[0136] Table 4

[0137]

[0138] The operation steps are the same as in Example 1, the number average molecular weight of the polymer is 45,000, the molecular weight distribution index is 2, and the average thickness after film formation is 260 um.

[0139] Example Five

[0140] The VBzBHPO-2EO and AMPS were copolymerized to prepare a single-ion conductor type polymer solid electrolyte, and the required raw materials are shown in Table 5.

[0141] Table 5

[0142]

[0143] The operation steps are the same as in Example 1, the number average molecular weight of the polymer is 30,000, the molecular weight distribution index is 2.2, and the average thickness is 190 um.

[0144] Example Six

[0145] The VBzBHPO-2EO and AMPS were copolymerized to prepare a single-ion conductor type polymer solid electrolyte, and the required raw materials are shown in Table 6.​​​​

[0146] Table 6

[0147]

[0148] The operation steps are the same as in Example 1, the number average molecular weight of the polymer is 45,000, the molecular weight distribution index is 2, and the average thickness is 205 um.

[0149] Example Seven

[0150] Taking the preparation of a single-ion conductor type polymer solid electrolyte by copolymerization of VBzBHPO-3EO and AMPS prepared in the above Example-3 as an example, the required raw materials are shown in Table 7.

[0151] Table 7

[0152]

[0153] The operation steps are the same as in Example 1, the number average molecular weight of the polymer is 60,000, the molecular weight distribution index is 2.8, and the average thickness is 210 um.

[0154] Example Eight

[0155] Taking the preparation of a single-ion conductor type polymer solid electrolyte by copolymerization of VBzBHPO-3EO and AMPS as an example, the required raw materials are shown in Table 8.

[0156] Table 8

[0157]

[0158] The operation steps are the same as in Example 1, the number average molecular weight of the polymer is 30,000, the molecular weight distribution index is 2.2, and the average thickness is 218 um.

[0159] Example Nine

[0160] Taking the preparation of a single-ion conductor type polymer solid electrolyte by copolymerization of VBzBHPO-3EO and AMPS as an example, the required raw materials are shown in Table 9.

[0161] Table 9

[0162]

[0163] The operation steps are the same as in Example 1, the number average molecular weight of the polymer is 40,000, the molecular weight distribution index is 2.7, and the average thickness is 216 um.

[0164] Example Ten

[0165] ​​​​Example 1

[0166] Table 10

[0167]

[0168] The operation steps are the same as those in Example 1. The number average molecular weight of the polymer is 80,000, the molecular weight distribution index is 2.4, and the average thickness is 193 um.

[0169] Example 11

[0170] Example 1

[0171] Table 11

[0172]

[0173] The operation steps are the same as those in Example 1. The number average molecular weight of the polymer is 70,000, the molecular weight distribution index is 2, and the average thickness is 133 um.

[0174] Example 12

[0175] Example 1

[0176] Table 12

[0177]

[0178] The operation steps are the same as those in Example 1. The number average molecular weight of the polymer is 74,000, the molecular weight distribution index is 2, and the average thickness is 140 um.

[0179] Example 13

[0180] Example 1

[0181] Table 13

[0182]

[0183] The operation steps are the same as those in Example 1. The number average molecular weight of the polymer is 80,000, the molecular weight distribution index is 2.1, and the average thickness is 109 um. ​​​​

[0184] 1. Characterization of VBzBHPO-1EO monomer

[0185] The 1H and 1P NMR spectra of the VBzBHPO-1EO monomer are as follows: Figure 1 As shown in (a), the chemical shifts of hydrogen atoms on the vinyl group include three peaks: 5.23–5.26 (doublet), 5.80–5.84 (doublet), and 6.69–6.76 (quartet) ppm. The hydrogen atoms on the benzene ring have doublets at 7.22–7.25 and 7.42–7.44 ppm, and the hydrogen atoms on the methylene group attached to the benzene ring have doublets at 3.17–3.21 ppm. H The 2Ph) ppm, the hydrogen chemical shifts of the remaining methylene structures are multiplets at 3.82-3.72, 3.67-3.59, and 3.48-3.45 ppm, respectively, while the hydrogen chemical shift of the terminal methyl group is a singlet at 3.28 ppm. The phosphorus chemical shift of the monomer is at 38.89 ppm, representing a component with only one phosphorus chemical environment. The carbon NMR spectrum of the monomer is shown below. Figure 1 As shown in (b), 136.82 and 114.35 ppm correspond to two carbon chemical shifts of vinyl groups. The four carbon chemical shifts in the benzene ring are concentrated between 126 and 135 ppm. 31-32 and 65 ppm correspond to the carbon chemical shifts of the methylene group attached to phosphorus. The carbon chemical shifts of the remaining methylene structures are at 71.39 and 72.65 ppm, respectively. The carbon atom chemical shift on the terminal methyl group is 58.61 ppm.

[0186] from Figure 4 It can be seen that the glass transition temperature T of the phosphorus-containing polymer solid electrolyte film with V-shaped polyether side chains prepared in Example 1 is... g = -28.6℃, which is conducive to the movement of polymer chain segments at room temperature.

[0187] Figure 5 The TGA-DTG thermogravimetric curve of the phosphorus-containing polymer solid electrolyte film with V-shaped polyether side chains prepared in Example 1 shows that its initial decomposition temperature is 293.6℃, ​​and the maximum decomposition temperatures are 412.7℃ and 444.2℃, respectively, exhibiting high thermal stability.

[0188] Figure 6 The EIS impedance diagrams of the phosphorus-containing polymer solid electrolyte film with V-shaped polyether side chains prepared in Example 1 were measured at different temperatures. The ionic conductivity at 90℃ was calculated to be δ = 4.18 × 10⁻⁶. -7 S / cm.

[0189] Figure 7EIS impedance plots of the P-containing polymer solid-state electrolyte thin film with V-shaped polyether side chains prepared for Example Twelve measured at different temperatures, and the ionic conductivity at 90℃ was calculated as δ = 2.35 x 10 -6 S / cm.

[0190] Figure 8 EIS impedance plots of the P-containing polymer solid-state electrolyte thin film with V-shaped polyether side chains prepared for Example Thirteen measured at different temperatures, and the ionic conductivity at 90℃ was calculated as δ = 2.36 x 10 -6 S / cm.

[0191] In summary, the present application utilizes the multivalence of phosphorus element, on the basis of benzyl vinyl structure, introduces two short chain polyether side chains at one time through Williamson synthesis, forms a structure similar to open-chain crown ether, and provides a novel P-containing monomer with V-shaped polyether side chains, which has the characteristics of simple synthesis method, diverse structure, high stability, and the like, and provides a new type of P-containing polymer electrolyte with good performance for practical application of solid-state batteries.

[0192] Those skilled in the art will easily understand that the above description is only a preferred embodiment of the present application, and is not intended to limit the present application, and any modification, equivalent replacement and improvement within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A polymer, characterized in that, Its structural formula is Wherein, n and m are the degrees of polymerization, R1-R and R2 are the structural units constituting the polymer, the structure of R1-R does not contain lithium salt, and the structure of R2 contains lithium salt; the side chain R of the polymer includes one or more of the following structural formulas: Where x and y are both positive integers from 1 to 30, and R4 is hydrogen, halogen, hydroxyl, carbon chain substituent with 1 to 36 carbon atoms or its derivatives. The Selected from one or more of the following structural formulas: 。 2. The polymer according to claim 1, characterized in that, R1 includes one or more of carbon chain polymers, heterochain polymers, or inorganic polymers; The carbon-chain polymer includes one or more of polystyrene, polymethacrylate, polyacrylamide, polyethylene, polypropylene, and polybutene; the heterochain polymer includes one or more of polyethylene oxide, polysiloxane, polycarbonate, and polyphosphate; and the inorganic polymer is polyphosphazene.

3. The polymer according to claim 2, characterized in that, The polymeric monomers R1-R in the polymer are selected from one or more of the following structural formulas: 。 4. The polymer according to claim 1, characterized in that, The R1-R is obtained by reacting the halogenated product of the monomer of R1 with a hydroxymethyl compound containing a multivalent element, specifically including the following steps: S1. React the halogenated product of the monomer of R1 with a hydroxymethyl compound to obtain one of the following products: S2, Combine the product from step S1 with... and An etherification reaction is carried out to obtain R1-R; wherein R3 is Br or p-toluenesulfonyl.

5. The polymer according to claim 4, characterized in that, Step S2 is carried out under alkaline conditions, and the phase transfer catalyst used includes one or more of the following: benzyltriethylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium hydrogen sulfate, trioctylmethylammonium chloride, dodecyltrimethylammonium chloride, tetradecyltrimethylammonium chloride, crown ether, and polyethylene glycol. When water is used as the solvent in step S2, the base used is one or more of NaOH, KOH, LiOH, K2CO3, Na2CO3, Li2CO3, potassium tert-butoxide, and quaternary ammonium bases; when an organic solvent is used, the base used is one or more of sodium methoxide, NaH, LiH, NaOH, KOH, LiOH, K2CO3, Na2CO3, Li2CO3, potassium tert-butoxide, and quaternary ammonium bases.

6. The polymer according to claim 1, characterized in that, The Selected from one or more of the following structural formulas: 。 7. A polymer solid electrolyte, characterized in that, Includes the polymer described in any one of claims 1-6.

8. The polymer solid electrolyte according to claim 7, characterized in that, The molar ratio of R1 to R2 is (50:50) ~ (95:5).

9. A method for preparing a polymer solid electrolyte membrane, characterized in that, The polymer solid electrolyte of any one of claims 7-8 is dissolved in a solvent and then solidified into a film by solvent evaporation to obtain a polymer solid electrolyte membrane.

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