A PEO-based solid-state electrolyte containing an azobenzene side group polymer additive, and a preparation method and application thereof

Abstract

The application belongs to the technical field of solid electrolyte, and discloses a PEO-based solid electrolyte containing azobenzene side group polymer additive as well as a preparation method and application thereof. The solid electrolyte is constructed by taking polyethylene oxide as a polymer matrix, butanedinitrile as a plasticizer, and a polymer containing azobenzene side groups as a functional additive and lithium bis-trifluoromethanesulfonimide. After the four components are uniformly mixed, a mixed solution is obtained, and then the solution is dried to obtain the solid electrolyte. The technical problem that the traditional PEO-based electrolyte has high room temperature crystallinity, low ionic conductivity, and difficulty in simultaneously considering mechanical strength and interface stability is solved, and a new idea and potential approach are provided for the development of high-performance solid lithium batteries.

Description

Technical Field

[0001] This invention belongs to the field of solid electrolyte technology, and relates to a PEO-based solid electrolyte containing azobenzene side-group polymer additives, its preparation method and application. Background Technology

[0002] Against the backdrop of global energy structure transformation and the booming development of the electric vehicle industry, the market has placed unprecedented demands on the performance of lithium batteries, pursuing not only higher energy density and longer cycle life, but also placing safety at the core. Traditional liquid lithium-ion batteries, due to their use of flammable organic electrolytes, have always posed safety hazards such as leakage, combustion, and even explosion, and their energy density is gradually approaching its theoretical limit, making it difficult to meet the urgent needs of next-generation energy storage technologies. Under these circumstances, solid-state lithium-ion batteries, which replace liquid electrolytes with solid electrolytes, have emerged. With their outstanding advantages such as high safety, high energy density, small size, and long life, they are recognized as the most promising next-generation lithium battery technology and have become a focus of attention for both industry and academia.

[0003] Among various solid electrolyte materials, polymer solid electrolytes, especially polyethylene oxide (PEO)-based electrolytes, are highly favored due to their excellent flexibility, good interfacial compatibility, and ease of processing. The ether oxygen groups on the PEO molecular chain can coordinate with lithium ions, forming ion transport channels and enabling lithium ion migration. However, PEO-based electrolytes face significant challenges in practical applications: their high crystallinity at room temperature leads to low ionic conductivity (typically below 10). -6 S·cm - ¹), which cannot meet the needs of practical applications. In addition, the interface stability between PEO and lithium metal anode is poor, which easily induces the growth of lithium dendrites, which not only increases the interface impedance, but also seriously affects the cycle life and safety performance of the battery, becoming a key bottleneck restricting its development.

[0004] To overcome these limitations, researchers typically employ strategies such as adding plasticizers, inorganic fillers, copolymerization, or crosslinking to improve the ionic conductivity of PEO-based electrolytes. Among these, succinic anionyl (SN) is a commonly used plasticizer that can effectively reduce the crystallinity of PEO and enhance chain segment mobility, thereby improving ion mobility. However, this method also introduces new problems: the addition of succinic anionyl often leads to a significant decrease in the mechanical strength of the electrolyte, and its chemical stability against lithium metal still needs improvement. More importantly, a single plasticizer strategy struggles to achieve an ideal balance between ionic conductivity, interfacial stability, and mechanical properties. Therefore, developing a PEO-based solid-state electrolyte that can significantly improve ionic conductivity, effectively enhance interfacial stability and suppress lithium dendrite growth, while also possessing good mechanical properties, has become a pressing research hotspot and challenge in the field of solid-state batteries. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a PEO-based solid electrolyte containing azobenzene side-group polymer additives, its preparation method, and its application. This solves the problem that existing technologies, when improving the ionic conductivity of PEO-based solid electrolytes, struggle to balance mechanical strength and interfacial stability, and thus fail to achieve synergistic optimization of these three properties.

[0006] This invention is achieved through the following technical solution: A method for preparing a PEO-based solid electrolyte containing an azobenzene side-group polymer additive includes the following steps: S1: n-Butylaniline, sodium nitrite, and hydrochloric acid are mixed and subjected to a diazotization reaction in an ice-water bath to generate a diazonium salt intermediate; the diazonium salt intermediate is mixed with phenol under alkaline conditions and subjected to a coupling reaction to obtain hydroxyazobenzene; the hydroxyazobenzene is subjected to a ring-opening polymerization reaction with an aliphatic cyclic carbonate monomer containing a benzene ring to obtain a polymer containing azobenzene side groups; S2: Polyethylene oxide, plasticizer and lithium salt are dissolved in an organic solvent, mixed by stirring once, and then the polymer containing azobenzene side groups is added. The mixture is stirred a second time to obtain a mixed slurry. Finally, the mixed slurry is dried to obtain the PEO-based solid electrolyte containing the azobenzene side group polymer additive.

[0007] Preferably, in step S1, the molar ratio of n-butylaniline to sodium nitrite is 1:(1.05~1.2).

[0008] Preferably, in step S1, the pH of the system is 2-3 when the diazotization reaction is carried out, and the pH of the system is 9-10 when the coupling reaction is carried out.

[0009] Preferably, in step S1, the molar ratio of the hydroxyazobenzene to the aliphatic cyclic carbonate monomer containing a benzene ring is 1:(55~65).

[0010] Preferably, in step S1, the reaction temperature of the ring-opening polymerization reaction is 60~100℃, and the reaction time is 12~48h.

[0011] Preferably, in step S2, the molar ratio of polyethylene oxide to lithium salt is (9~24):1; and the mass ratio of plasticizer to polyethylene oxide is 1:(8~12).

[0012] Preferably, in step S2, the mass of the polymer containing azobenzene side groups added is 0.2% to 0.8% of the mass of polyethylene oxide.

[0013] Preferably, in step S2, the time for the first stirring is 4~18h; and the time for the second stirring is 6~24h.

[0014] A PEO-based solid electrolyte containing azobenzene side-group polymer additives is prepared by the above-described method for preparing a PEO-based solid electrolyte containing azobenzene side-group polymer additives.

[0015] The above-mentioned application of a PEO-based solid electrolyte containing azobenzene side-group polymer additives in lithium-ion batteries.

[0016] Compared with the prior art, the present invention has the following beneficial technical effects: This invention discloses a method for preparing a PEO-based solid electrolyte with an azobenzene side-group polymer additive. This method, through molecular structure design and multiphase component control, solves the technical challenge of simultaneously improving mechanical strength and interfacial stability in PEO-based solid electrolytes while enhancing ionic conductivity. The method first synthesizes a polymer containing azobenzene side groups as a key additive. Utilizing the photoresponsive properties of the azobenzene group and the rigid structure of the benzene ring, a dynamic physical cross-linking network is constructed within the polymer matrix. This network not only effectively inhibits excessive crystallization of PEO segments, providing abundant and rapid transport channels for lithium ions and significantly improving ionic conductivity, but also compensates for the mechanical strength loss due to the addition of plasticizers by introducing the rigid benzene ring, preventing lithium dendrite puncture. Furthermore, a specific interaction exists between the azobenzene side groups and lithium salt anions, which can fix the anions and promote the uniform dissociation of lithium salts, thereby forming a stable solid electrolyte interfacial film at the electrode interface and reducing interfacial impedance. Finally, this method, through a one-step synthesis and a simple solution blending process, achieves a triple synergistic optimization of ion transport channel construction, mechanical framework enhancement, and interfacial chemical stability, breaking through the bottleneck of mutual constraints on the performance of traditional solid electrolytes.

[0017] Furthermore, in step S1, the molar ratio of n-butylaniline to sodium nitrite is 1:(1.05~1.2). By maintaining a slight excess of sodium nitrite, it is ensured that the n-butylaniline raw material is completely converted into the diazonium salt intermediate, thereby effectively avoiding the residue of unreacted aromatic amines. If the amine raw material is not completely converted, it is very easy to undergo a self-coupling side reaction with the diazonium salt in subsequent steps. This ratio control ensures the purity of the coupling reaction and the yield of the final product from the source.

[0018] Furthermore, in step S1, the pH of the system is 2-3 during the diazotization reaction and 9-10 during the coupling reaction. In a strongly acidic environment of pH 2-3, the diazonium salt intermediate can maintain extremely high stability, preventing premature decomposition. In a weakly alkaline environment of pH 9-10, phenol can be fully converted into phenolate anions. This highly active nucleophile greatly improves the rate and conversion of the coupling reaction, while avoiding the problem of diazonium salt deactivation caused by excessive alkalinity.

[0019] Furthermore, in step S1, the molar ratio of the hydroxyazobenzene to the aliphatic cyclic carbonate monomer containing the benzene ring is 1:(55~65). This ratio range ensures that the synthesized polymer containing azobenzene side groups has a suitable molecular chain length, which can both ensure that it forms an effective physical cross-linking network in the solid electrolyte matrix to provide mechanical support, and avoid poor solubility or processing difficulties caused by excessive molecular weight.

[0020] Furthermore, in step S1, the reaction temperature of the ring-opening polymerization reaction is 60~100℃ and the reaction time is 12~48h. This combination of temperature and time ensures that the monomer can be fully converted and the high molecular weight polymer can be successfully synthesized, while effectively avoiding side reactions such as polymer chain degradation and cross-linking caused by excessively high temperature or excessive time, thus ensuring the regularity of the polymer structure and the purity of the product.

[0021] Furthermore, in step S2, the molar ratio of polyethylene oxide to lithium salt is (9~24):1; the mass ratio of plasticizer to polyethylene oxide is 1:(8~12). This ratio of lithium salt ensures sufficient lithium-ion transport channels, while the specific ratio of plasticizer effectively destroys the crystallinity of PEO. This significantly improves the room temperature ionic conductivity while preventing a sharp drop in the mechanical strength of the electrolyte caused by excessive plasticizer.

[0022] Furthermore, in step S2, the added mass of the polymer containing azobenzene side groups is 0.2% to 0.8% of the mass of polyethylene oxide. At this extremely low addition amount, the azobenzene polymer can form a uniform rigid skeleton or interface protective layer in the matrix, thereby significantly enhancing the mechanical strength of the electrolyte and improving the stability of the electrode interface, while avoiding damage to the original ion transport network or phase separation of the system due to excessive addition.

[0023] Furthermore, in step S2, the first stirring time is 4~18h; the second stirring time is 6~24h. The staged long-term stirring first ensures that the high molecular weight PEO is fully swollen and completely dissolved in the solvent, and then ensures the uniform distribution of trace polymer additives, lithium salts and plasticizers, effectively avoiding local agglomeration, thereby ensuring the uniformity of the final solid electrolyte film and the stability of its electrochemical performance. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 The XRD patterns are of PEO-SN-0.2%PMBC, PEO-SN-0.4%PMBC, PEO-SN-0.6%PMBC and PEO-SN-0.8%PMBC prepared in Example 1 of the present invention and PEO-SN prepared in Comparative Example 1. Figure 2 Tensile diagrams of PEO-SN-0.2%PMBC, PEO-SN-0.4%PMBC, PEO-SN-0.6%PMBC and PEO-SN-0.8%PMBC prepared in Example 1 of the present invention and PEO-SN prepared in Comparative Example 1. Figure 3 The battery cycle curves at different rates are for batteries assembled with PEO-SN-0.6%PMBC prepared in Example 1 of the present invention and PEO-SN solid electrolyte prepared in Comparative Example 1. Figure 4 The battery cycle curves at a current density of 0.5C are shown for the batteries assembled with PEO-SN-0.6%PMBC prepared in Example 1 of the present invention and PEO-SN solid electrolyte prepared in Comparative Example 1. Figure 5The impedance comparison diagrams of batteries assembled with PEO-SN-0.6%PMBC prepared in Example 1 and PEO-SN solid electrolyte prepared in Comparative Example 1 at different temperatures are shown. Figure 6 The figures show the DC polarization current curves of the batteries assembled with PEO-SN-0.6%PMBC prepared in Example 1 of the present invention and PEO-SN solid electrolyte prepared in Comparative Example 1. The inset shows the AC impedance before and after DC polarization. Figure 7 The battery assembled with the PEO-SN-0.6%PMBC solid electrolyte prepared in this embodiment of the invention operates at 0.01 mA·cm⁻¹. 2 Long-cycle plot at current density. Detailed Implementation

[0026] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0027] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0028] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0029] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0030] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0031] This invention provides a method for preparing a PEO-based solid electrolyte containing an azobenzene side-group polymer additive, comprising the following steps: S1: Preparation of azobenzene side-group-containing polymers (PMBC): n-Butylaniline, sodium nitrite, and hydrochloric acid are mixed and subjected to a diazotization reaction in an ice-water bath to generate a diazonium salt intermediate. The diazonium salt intermediate is then mixed with phenol under alkaline conditions and subjected to a coupling reaction to obtain hydroxyazobenzene. The hydroxyazobenzene is then mixed with an aliphatic cyclic carbonate monomer containing a benzene ring and subjected to a ring-opening polymerization reaction under argon protection to obtain a polymer containing azobenzene side groups (PMBC). Specifically, the above process is as follows: n-Butylaniline and sodium nitrite (NaNO2) are mixed and reacted in an ice-water bath and a strongly acidic environment (HCl). NaNO2 reacts with HCl to generate nitrous acid (HNO2), which then reacts with n-Butylaniline to generate a diazonium salt intermediate. The diazonium salt is then mixed with phenol under alkaline conditions (KOH) for 2 hours. The diazonium salt acts as an electrophilic reagent to attack the para position of the phenol oxide anion to form an azo bond (-N=N-), generating hydroxyazobenzene. The hydroxyazobenzene is used as an initiator and mixed with an aliphatic cyclic carbonate monomer (MBC) containing a benzene ring. The mixture undergoes a ring-opening polymerization reaction at 85°C for 30 hours. The terminal hydroxyl groups generated after the monomer ring-opening continue to initiate the growth of subsequent monomer chains. Finally, one end of the polymer chain is capped by an azophenyl group. After treatment, a polymer containing azobenzene side groups (PMBC) is obtained.

[0032] In step S1, the molar ratio of n-butylaniline to sodium nitrite is 1:(1.05~1.2).

[0033] When carrying out the diazotization reaction, the pH value of the system is less than 3, preferably 2 to 3; When the coupling reaction is carried out, the pH value of the system is greater than 9, preferably 9-10; The molar ratio of the hydroxyazobenzene to the aliphatic cyclic carbonate monomer containing a benzene ring is 1:(55~65), preferably 1:60; The ring-opening polymerization reaction is carried out at a temperature of 60-100℃, preferably 85℃, for a reaction time of 12-48 hours, preferably 30 hours.

[0034] S2: Preparation of composite solid electrolyte: Polyethylene oxide, plasticizer, and lithium salt are dissolved in an organic solvent, mixed once, and then the polymer containing azobenzene side groups is added. The mixture is stirred a second time to obtain a mixed slurry. Finally, the mixed slurry is dried to obtain the PEO-based solid electrolyte containing the azobenzene side group polymer additive.

[0035] The above process is as follows: polyethylene oxide (PEO), plasticizer (which can be succinate, SN) and lithium salt (which can be lithium bis(trifluoromethanesulfonylimide, LiTFSI)) are dissolved in acetonitrile. After one stirring, the polymer containing azobenzene side groups (PMBC) is added. After a second stirring, a uniform and transparent slurry is obtained. Then, it is vacuum dried at 60°C for 8-10 hours to obtain the PEO-based solid electrolyte containing the polymer additive containing azobenzene side groups.

[0036] Preferably, the molar ratio of polyethylene oxide to lithium salt is (9~24):1, more preferably 20:1. This ratio allows the ether oxygen groups on the polyethylene oxide molecular chain to react with the lithium salt. + Sufficient coordination is achieved to construct a stable ion transport channel, while ensuring appropriate dissociation of the lithium salt, avoiding ion pair aggregation due to excessive lithium salt or free Li due to insufficient lithium salt. + The concentration is too low. This ratio satisfies the ion transport requirements while maintaining the inherent flexibility of the PEO-based system, achieving a balance between ionic conductivity and mechanical properties.

[0037] The mass ratio of the plasticizer to polyethylene oxide is 1:(8~12), preferably 1:10. This ratio allows succinic anionyl nitrile to fully exert its plasticizing effect, disrupting the crystallinity of polyethylene oxide while avoiding abnormal viscosity or excessive decrease in mechanical strength due to excessive succinic anionyl nitrile. Too high a ratio will cause the electrolyte membrane to deform easily, while too low a ratio will result in insufficient plasticizing effect and inability to effectively reduce the crystallinity of polyethylene oxide. This ratio range allows for synergistic optimization of plasticizing effect and structural stability.

[0038] The polymer containing azobenzene side groups is added at a mass of 0.2% to 0.8% of the mass of polyethylene oxide, specifically 0.2%, 0.4%, 0.6%, or 0.8%.

[0039] Vacuum drying at 60℃ for 8-10 hours ensures sufficient evaporation of acetonitrile solvent while preventing oxidation of polyethylene oxide, decomposition of butadiene nitrogen, or changes in the PMBC structure caused by excessively high temperatures. It also prevents solvent residue from remaining due to excessively low temperatures or short drying times, which could affect the ion transport performance and chemical stability of the electrolyte. Precise drying parameters guarantee the structural integrity and performance consistency of the electrolyte membrane, ensuring long-term stable battery operation.

[0040] The initial stirring time is 4–18 hours, preferably 10 hours; the secondary stirring time is 6–24 hours, preferably 14 hours. Prolonged stirring ensures that polyethylene oxide, lithium bis(trifluoromethanesulfonyl)imide, and succinate are fully dissolved and uniformly mixed in acetonitrile. Extended stirring after the subsequent addition of PMBC promotes uniform dispersion of the additives, preventing localized excessive concentrations or agglomeration. Insufficient stirring time leads to uneven mixing and performance fluctuations; excessive stirring time causes excessive solvent evaporation or abnormal system viscosity.

[0041] This invention discloses a method for preparing a PEO-based solid electrolyte containing an azobenzene side-group polymer additive. The method involves mixing an azobenzene side-group polymer (PMBC) as a functional additive with polyethylene oxide (PEO), succinate (SN), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), followed by solution casting and drying to obtain the solid electrolyte. This solid electrolyte significantly improves ionic conductivity and interfacial stability while maintaining excellent flexibility. PMBC is uniformly dispersed in the PEO matrix, synergistically disrupting the regular stacking of PEO molecular chains with SN, effectively reducing polymer crystallinity, expanding the amorphous region, and providing ample channels for lithium-ion transport. Simultaneously, its ester functional groups form a synergistic coordination system with the etheroxy groups of PEO and the cyano groups of SN, promoting lithium salt dissociation and increasing the concentration of free lithium ions. This solid electrolyte possesses high ionic conductivity, good mechanical strength, and excellent electrode interfacial compatibility, effectively suppressing lithium dendrite growth and reducing interfacial impedance, providing a reliable material basis and design direction for the practical development of solid-state batteries. This invention discloses a method for preparing a PEO-based solid electrolyte containing an azobenzene side-group polymer additive. The azobenzene side-group polymer additive (PMBC) is prepared by diazo coupling reaction and ring-opening polymerization reaction. It has a controllable structure and good compatibility with the PEO matrix. When mixed with PEO, SN, and LiTFSI, it can synergistically optimize the crystal structure, ion transport performance and interface stability of the electrolyte, providing a new idea and potential approach for the development of high-performance solid-state lithium batteries.

[0042] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0043] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0044] Example 1 A method for preparing a PEO-based solid electrolyte containing an azobenzene side-group polymer additive includes the following steps: (1) Preparation of polymers containing azobenzene side groups (PMBC): 0.5 mol of n-butylaniline was dissolved in 100 mL of 1 mol / L hydrochloric acid solution and cooled to 0 °C in an ice-water bath. 0.55 mol of sodium nitrite aqueous solution (20% by mass) was slowly added dropwise and stirred for 1 h to generate a diazonium salt intermediate. Separately, 0.5 mol of phenol was dissolved in 50 mL of 2 mol / L potassium hydroxide solution and slowly added to the diazonium salt solution. The reaction was continued for 2 h. After acidification with hydrochloric acid, filtration, and washing, hydroxyazobenzene was obtained. 0.01 mol of hydroxyazobenzene, 0.6 mol of aliphatic cyclic carbonate monomer (MBC) containing a benzene ring, and 100 mL of anhydrous dichloromethane were added to a dry three-necked flask. Argon gas was introduced for protection, and 0.001 mol of stannous octoate was added as a catalyst. The temperature was raised to 85 °C and the reaction was carried out for 30 h. After the reaction was completed, the product was poured into excess methanol to precipitate, filtered, and dried under vacuum at 65 °C for 14 h to obtain a polymer containing azobenzene side groups (PMBC).

[0045] (2) Preparation of solid electrolytes: 1.5 g of polyethylene oxide (PEO, molecular weight 600,000) was placed in a flat-bottomed flask, and 20 mL of acetonitrile solvent, 0.15 g of succinic anionyl nitrile (SN), and 0.489 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) were added. The mixture was stirred at room temperature for 10 h. 0.2% PMBC (by weight of PEO) was added to the mixture, and stirring was continued for 14 h to obtain a slurry. The slurry was poured onto a polytetrafluoroethylene plate and vacuum dried in an oven at 60 °C for 8 h to obtain a solid electrolyte, namely a PEO-based solid electrolyte containing azobenzene side-group polymer additives, which was named PEO-SN-0.2%PMBC.

[0046] Example 2 The difference between this embodiment and embodiment 1 is that in step (2), PMBC with a mass of 0.4% of polyethylene oxide mass is added to the mixture to obtain a PEO-based solid electrolyte containing azobenzene side group polymer additive, named PEO-SN-0.4%PMBC.

[0047] Example 3 The difference between this embodiment and embodiment 1 is that in step (2), PMBC with a mass of 0.4% of polyethylene oxide is added to the mixture to obtain a PEO-based solid electrolyte containing azobenzene side group polymer additive, named PEO-SN-0.6%PMBC.

[0048] Example 4 The difference between this embodiment and embodiment 1 is that in step (2), PMBC with a mass of 0.4% of polyethylene oxide is added to the mixture to obtain a PEO-based solid electrolyte containing azobenzene side group polymer additive, named PEO-SN-0.8%PMBC.

[0049] Comparative Example 1 The difference from Example 1 is that in step S2, no azobenzene side-group polymer (PMBC) is added, and only PEO, SN and LiTFSI are used to prepare the solid electrolyte. The solid electrolyte prepared in this comparative example is named PEO-SN.

[0050] Example 5 A method for preparing a PEO-based solid electrolyte containing an azobenzene side-group polymer additive includes the following steps: S1: Butylaniline, sodium nitrite, and hydrochloric acid are mixed, and the pH of the system is controlled to be 2. The molar ratio of n-butylaniline to sodium nitrite is 1:1.05. A diazotization reaction is carried out under an ice-water bath to generate a diazonium salt intermediate. The diazonium salt intermediate is mixed with phenol under alkaline conditions at pH 9 to carry out a coupling reaction to obtain hydroxyazobenzene. The hydroxyazobenzene is mixed with an aliphatic cyclic carbonate monomer containing a benzene ring, and the molar ratio of the hydroxyazobenzene to the aliphatic cyclic carbonate monomer containing a benzene ring is 1:55. A ring-opening polymerization reaction is carried out at 60°C for 48 hours under argon protection to obtain a polymer containing azobenzene side groups (PMBC). S2: Polyethylene oxide, plasticizer, and lithium salt are dissolved in an organic solvent. The molar ratio of polyethylene oxide to lithium salt is 9:1, and the mass ratio of plasticizer to polyethylene oxide is 1:8. After stirring for 4 hours, the polymer containing azobenzene side groups is added, and the mixture is stirred for 6 hours to obtain a mixed slurry. The mass of the polymer containing azobenzene side groups added is 0.2% of the mass of polyethylene oxide. Finally, the mixture is dried under vacuum at 60°C for 8 hours to obtain a PEO-based solid electrolyte with the polymer additive containing azobenzene side groups.

[0051] Example 6 A method for preparing a PEO-based solid electrolyte containing an azobenzene side-group polymer additive includes the following steps: S1: Butylaniline, sodium nitrite, and hydrochloric acid are mixed, and the pH of the system is controlled to be 3, wherein the molar ratio of n-butylaniline to sodium nitrite is 1:1.2. A diazotization reaction is carried out under an ice-water bath to generate a diazonium salt intermediate. The diazonium salt intermediate is mixed with phenol under alkaline conditions at pH 10 to carry out a coupling reaction to obtain hydroxyazobenzene. The hydroxyazobenzene is mixed with an aliphatic cyclic carbonate monomer containing a benzene ring, wherein the molar ratio of hydroxyazobenzene to the aliphatic cyclic carbonate monomer containing a benzene ring is 1:65. A ring-opening polymerization reaction is carried out at 100°C for 12 hours under argon protection to obtain a polymer containing azobenzene side groups (PMBC). S2: Polyethylene oxide, plasticizer, and lithium salt are dissolved in an organic solvent. The molar ratio of polyethylene oxide to lithium salt is 24:1, and the mass ratio of plasticizer to polyethylene oxide is 1:12. After stirring for 18 hours, the polymer containing azobenzene side groups is added, and the mixture is stirred for 24 hours to obtain a mixed slurry. The mass of the polymer containing azobenzene side groups added is 0.8% of the mass of polyethylene oxide. Finally, the mixture is dried under vacuum at 60°C for 10 hours to obtain a PEO-based solid electrolyte with the polymer additive containing azobenzene side groups.

[0052] Example 7 A method for preparing a PEO-based solid electrolyte containing an azobenzene side-group polymer additive includes the following steps: S1: Butylaniline, sodium nitrite, and hydrochloric acid are mixed, and the pH of the system is controlled to be 2. The molar ratio of n-butylaniline to sodium nitrite is 1:1.15. A diazotization reaction is carried out under an ice-water bath to generate a diazonium salt intermediate. The diazonium salt intermediate is mixed with phenol under alkaline conditions at pH 9 to carry out a coupling reaction to obtain hydroxyazobenzene. The hydroxyazobenzene is mixed with an aliphatic cyclic carbonate monomer containing a benzene ring, and the molar ratio of the hydroxyazobenzene to the aliphatic cyclic carbonate monomer containing a benzene ring is 1:60. A ring-opening polymerization reaction is carried out at 80°C for 35 hours under argon protection to obtain a polymer containing azobenzene side groups (PMBC). S2: Polyethylene oxide, plasticizer, and lithium salt are dissolved in an organic solvent. The molar ratio of polyethylene oxide to lithium salt is 15:1, and the mass ratio of plasticizer to polyethylene oxide is 1:10. After stirring for 10 hours, the polymer containing azobenzene side groups is added, and the mixture is stirred for 20 hours to obtain a mixed slurry. The mass of the polymer containing azobenzene side groups added is 0.5% of the mass of polyethylene oxide. Finally, the mixture is dried under vacuum at 60°C for 9 hours to obtain a PEO-based solid electrolyte with the polymer additive containing azobenzene side groups.

[0053] To verify the performance of the solid electrolyte prepared in this invention, it was assembled into a battery, and its performance was tested, as follows: This invention assembles three types of batteries: Li / CSEs / LFP, ss / CSEs / ss, and Li / CSEs / Li.

[0054] The assembly processes for the three types of batteries are as follows: (1) Li / CSEs / LFP (Li / solid electrolyte / lithium iron phosphate) battery: The positive electrode of the lithium-ion battery uses a mixture of 80 wt% lithium iron phosphate (as the active material), 10 wt% binder (polyvinylidene fluoride, PVDF), and 10 wt% Ketjen black. After mixing, it is ground in a mill for 1 hour and then placed into a container. Subsequently, an appropriate amount of nitrogen is added to the container. methyl 2 Pyrrolidone (NMP, solvent) was added and stirred at a constant speed on a magnetic stirrer for 6 hours to ensure the mixture reached a viscous fluid state. During this process, carbon-coated aluminum foil was used as a current collector, and the mixture was uniformly coated onto its surface. Then, the carbon-coated aluminum foil was placed in a vacuum drying oven at 60°C for 12 hours before being removed for use. Next, the prepared carbon-coated aluminum foil was cut into several electrode discs using a specialized slicer to obtain the lithium cathode material.

[0055] The negative electrode of this lithium-ion battery is a Li sheet, and the above-mentioned positive electrode, negative electrode and composite solid electrolyte are assembled into an LFP battery for subsequent testing.

[0056] (2) SS / CSEs / SS (SS / Solid Electrolyte / SS) Battery: The positive and negative electrodes of this lithium-ion battery are both stainless steel sheets (SS), and the above positive and negative electrodes and composite solid electrolyte are assembled into SS / SS batteries for subsequent testing.

[0057] (3) Li / CSEs / Li (Li / solid electrolyte / Li) battery: The positive and negative electrodes of this lithium-ion battery are both Li sheets, and the positive and negative electrodes and the composite solid electrolyte are assembled into a Li / Li battery for subsequent testing.

[0058] Test 1: Physical Property Testing of Materials The physical performance evaluation of solid electrolyte membranes mainly includes X-ray diffraction analysis (XRD) and mechanical property testing.

[0059] (1) Electrolyte membrane XRD test Figure 1 The XRD patterns of the PEO-SN composite systems with different PMBC additions in Example 1 of this invention are shown. As can be seen from the figures, characteristic crystallization peaks of PEO appear in each system around 2θ≈20°, with PEO-SN exhibiting the highest peak intensity and sharpest peak shape. As the PMBC addition increases to 0.2%, the PEO crystallization peak intensity decreases; when the PMBC addition further increases to 0.4%~0.6%, the crystallization peak intensity continues to weaken but the change becomes gradual, with the lowest peak intensity at 0.6%; when the PMBC addition further increases to 0.8%, the crystallization peak intensity increases, indicating that excessive PMBC molecules will aggregate in the PEO matrix; all curves show only PEO peaks without impurity peaks, indicating that no new crystalline phase or impurities are introduced. This demonstrates that the introduction of PMBC does not change the crystalline structure of PEO, but only reduces its crystallinity by disrupting the regularity of the molecular chains, also proving that the preparation process of the system is stable and the target product structure meets expectations.

[0060] (2) Electrolyte membrane mechanical property testing Figure 2 The figure shows tensile diagrams of the PEO-SN composite system with different PMBC addition amounts in Example 1 of this invention. As can be seen from the figure, the maximum stress of the PEO-SN electrolyte membrane is 1.54 MPa. The four types of electrolyte membranes with different PMBC addition amounts (PEO-SN-0.2%, PEO-SN-0.4%, PEO-SN-0.6%, and PEO-SN-0.8%) are also shown. The maximum stress of the plasma membrane increased to 1.74, 2.55, 3.05, and 2.63 MPa, respectively. When the PMBC content was between 0.2% and 0.6%, it could be uniformly dispersed in the PEO matrix. The rigid side groups of each PMBC molecule interacted with the PEO molecular chains, effectively improving the tensile strength of the system, as shown by the increase in strength with increasing content. However, when the PMBC content increased to 0.8%, the PMBC molecules in the system could not maintain uniform dispersion due to the excessively high concentration, and rigid agglomeration occurred, forming local rigid agglomerates. These agglomerates were not uniform reinforcing units, but became stress concentration sources in the system. During the tensile process, the PEO molecular chains around the agglomerates would experience local stress overload due to uneven stress distribution, causing the PEO chain segments to preferentially break in the stress concentration areas, ultimately resulting in a decrease in the overall tensile strength of the system compared to 0.6%.

[0061] Test 2: Assembly and Electrochemical Performance Testing of Lithium-ion Batteries During the testing phase, CR-2025 coin cells were used for assembly. Specifically, the positive and negative electrode casings, gaskets, nickel foam, and solid electrolytes prepared in Example 1 and Comparative Example 1 were assembled into a battery in an argon-filled glove box, and its performance was subsequently comprehensively tested. Before assembly, the electrode sheets were accurately weighed, and the content of active material was calculated.

[0062] (1) Capacity curve test To verify the potential of PEO-SN and PEO-SN-0.6%PMBC in practical applications, Li / LFP full cells were assembled. The performance of the prepared cells was tested using a Blue Electricity testing system. Charge-discharge tests were conducted at 60°C. The results are as follows: Figure 3 As shown, the rate performance of the Li / PEO-SN / LFP battery and the Li / PEO-SN-0.6%PMBC / LFP battery are demonstrated. Figure 3 It can be seen that the assembled PEO-SN-0.6%PMBC battery has a discharge specific capacity of 163.5, 156.0, 152.5, 148.1, and 140.9 mAh g at current densities of 0.1C-1C. -1 The PEO-SN values ​​were 125.9, 124.1, 122.1, 116.9, and 101.9 mAh g. -1 This indicates that PEO-SN-0.6%PMBC has more significant rate performance.

[0063] And it was tested cyclically, and the results were as follows: Figure 4 As shown, by Figure 4It can be seen that the Li / PEO-SN-0.6%PMBC / LFP battery remains stable after 300 cycles at 60℃, providing 144.0 mAh·g. -1 The discharge capacity and retention rate are 78.5%, while the Li / PEO-SN / LFP battery retains 67.8% of its capacity after 300 cycles.

[0064] (2) Electrochemical testing Battery performance can be assessed by ionic conductivity (σ) and lithium-ion transference number (t). Li + The evaluation will be conducted using [the provided text]. See the results below. Figure 5 and Figure 6 The SS / SS battery assembled from PEO-SN-0.6%PMBC and PEO-SN solid electrolyte exhibits an ionic conductivity of 8.54 × 10⁻⁶ at 70 °C. -4 S cm -1 5.70×10 -4 S cm -1 Lithium-ion transference number (t) Li + The ion transport capabilities of CSSE were evaluated, such as... Figure 6 The initial current of PEO-SN-0.6%PMBC before polarization was 3.42 μA, and the steady-state current after polarization was 1.26 μA, exhibiting a lithium-ion transference number of 0.45, exceeding that of PEO-SN (0.13). Introducing PMBC into the PEO matrix significantly enhances the lithium-ion transference number. The PMBC molecular chain contains ester groups, benzene rings, and other functional groups, which can interact with the etheroxy groups of the PEO molecular chain and the cyano groups of succinate (SN). This multi-functional interaction can disrupt the Li in LiTFSI. + With TFSI - The binding of ion pairs promotes the complete dissociation of lithium salt, releasing more free Li. + PMBC expands the amorphous region by inhibiting PEO crystallization. The amorphous region has higher molecular chain flexibility, further weakening the Li... + The binding strength with the coordinating group makes Li + It is easier to break free from constraints and participate in migration, providing a material basis for increasing the number of migrations.

[0065] A symmetrical Li / CSEs / Li battery was assembled, and the suppression effect of lithium dendrites was investigated. Figure 7 These symmetrical cells were shown to operate at 60°C and a current density of 0.01 mA cm⁻¹. -2 In the plating / stripping experiment, Li / PEO-SN-0.6%PMBC / Li exhibited excellent cycling stability over 2400 hours, while its polarization voltage changed smoothly without significant fluctuations, effectively suppressing the formation of lithium dendrites.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a PEO-based solid electrolyte containing an azobenzene side-group polymer additive, characterized in that, Includes the following steps: S1: n-Butylaniline, sodium nitrite, and hydrochloric acid are mixed and subjected to a diazotization reaction in an ice-water bath to generate a diazonium salt intermediate; the diazonium salt intermediate is mixed with phenol under alkaline conditions and subjected to a coupling reaction to obtain hydroxyazobenzene; the hydroxyazobenzene is subjected to a ring-opening polymerization reaction with an aliphatic cyclic carbonate monomer containing a benzene ring to obtain a polymer containing azobenzene side groups; S2: Polyethylene oxide, plasticizer and lithium salt are dissolved in an organic solvent, mixed by stirring once, and then the polymer containing azobenzene side groups is added. The mixture is stirred a second time to obtain a mixed slurry. Finally, the mixed slurry is dried to obtain the PEO-based solid electrolyte containing the azobenzene side group polymer additive.

2. The method for preparing a PEO-based solid electrolyte containing an azobenzene side-group polymer additive according to claim 1, characterized in that, In step S1, the molar ratio of n-butylaniline to sodium nitrite is 1:(1.05~1.2).

3. The method for preparing a PEO-based solid electrolyte containing an azobenzene side-group polymer additive according to claim 1, characterized in that, In step S1, the pH of the system is 2-3 when the diazotization reaction is carried out; the pH of the system is 9-10 when the coupling reaction is carried out.

4. The method for preparing a PEO-based solid electrolyte containing an azobenzene side-group polymer additive according to claim 1, characterized in that, In step S1, the molar ratio of the hydroxyazobenzene to the aliphatic cyclic carbonate monomer containing a benzene ring is 1:(55~65).

5. The method for preparing a PEO-based solid electrolyte containing an azobenzene side-group polymer additive according to claim 1, characterized in that, In step S1, the reaction temperature of the ring-opening polymerization reaction is 60~100℃, and the reaction time is 12~48h.

6. The method for preparing a PEO-based solid electrolyte containing an azobenzene side-group polymer additive according to claim 1, characterized in that, In step S2, the molar ratio of polyethylene oxide to lithium salt is (9~24):1; the mass ratio of plasticizer to polyethylene oxide is 1:(8~12).

7. The method for preparing a PEO-based solid electrolyte containing an azobenzene side-group polymer additive according to claim 1, characterized in that, In step S2, the mass of the polymer containing azobenzene side groups added is 0.2% to 0.8% of the mass of polyethylene oxide.

8. The method for preparing a PEO-based solid electrolyte containing an azobenzene side-group polymer additive according to claim 1, characterized in that, In step S2, the first stirring time is 4~18h; the second stirring time is 6~24h.

9. A PEO-based solid electrolyte containing an azobenzene side-group polymer additive, characterized in that, The PEO-based solid electrolyte with azobenzene side-group polymer additive as described in any one of claims 1 to 8 is prepared by the method described in claims 1 to 8.

10. The application of the PEO-based solid electrolyte containing azobenzene side-group polymer additive as described in claim 9 in lithium-ion batteries.

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