High-conductivity and high-safety PES-based solid electrolyte and battery
By using ring-opening polymerization of cyclothioethane and ether monomers and forming an SEI layer with lithium salt, the mechanical properties and lithium-ion transport issues of polymer electrolytes are solved, achieving high conductivity and stability, extending battery life, and inhibiting lithium dendrite growth.
Patent Information
- Application Number
- CN202511476008.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-15
- Publication Date
- 2026-02-10
AI Technical Summary
Existing polymer electrolytes suffer from insufficient mechanical properties, slow lithium-ion transport kinetics, and poor electrode/electrolyte interface stability, resulting in low coulombic efficiency, rapid capacity decay, and limited cycle life in solid-state batteries during high-rate charge and discharge, and the inability to effectively control lithium dendrite growth.
A low-crystallinity cross-linked polymer was formed by ring-opening polymerization of a mixture of cyclothioethyl and ether monomers under Lewis acidic conditions. A passivation SEI layer was formed by lithium salt, and a small amount of polytetrahydrofuran was combined to promote the formation of a flexible framework, improve the contact surface between the electrolyte and the electrode, and reduce solid-solid interface resistance and side reactions.
A solid electrolyte with high conductivity, wide electrochemical window, and high stability was achieved, which inhibits lithium dendrite growth, extends battery cycle life, and improves battery performance.
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Figure CN121507073A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of electrolyte technology, specifically relating to a PES-based solid electrolyte and battery with high conductivity and high safety. Background Technology
[0002] Currently, solid-state batteries are receiving widespread attention due to their ability to largely avoid the safety issues of traditional batteries while significantly reducing manufacturing costs. Solid-state electrolytes, as a crucial component, are favored by researchers and companies, especially polymer electrolytes, which possess excellent interfacial contact and high industrial production potential, making them one of the most practical choices for achieving these goals. However, their insufficient mechanical properties, slow lithium-ion transport kinetics, and poor electrode / electrolyte interface stability severely limit the practical application of polymer electrolytes. Optimizing the Li-ion content in the electrolyte... + Transport pathways and modulation of ion conduction behavior at the electrolyte / electrode interface are employed to achieve rapid, high-throughput, and uniform Li₂ transport. + Transportation is crucial for achieving high-performance lithium metal batteries.
[0003] Solid-state batteries suffer from solid-solid interface incompatibility, especially under high-rate charge-discharge conditions, often leading to low coulombic efficiency, rapid capacity decay, and limited cycle life. Simultaneously, the mechanical properties of the electrolyte can limit the volume expansion of the negative electrode to some extent, and the strength of lithium dendrite growth regulation directly affects the utilization rate of the lithium negative electrode, the energy density of the lithium-ion battery, and its driving range. To address these issues, researchers have proposed numerous solutions, primarily including: employing in-situ crosslinking polymerization technology, constructing artificial CEI / SEI interface layers, developing suitable weakly solvated electrolyte additives, and constructing highly compatible electrode-electrolyte interfaces. Among these, the in-situ solidification technology for preparing solid and semi-solid electrolytes has attracted considerable attention from numerous companies due to its simple, economical, rapid, and reliable industrialization process, and is considered one of the promising technological routes for directly replacing liquid lithium batteries.
[0004] Introducing an appropriate amount of polytetrahydrofuran into poly(ethylene sulfide) (PES)-based electrolytes is beneficial for improving the mechanical properties of solid electrolytes, effectively weakening lithium-ion coupling energy, and promoting uniform lithium transport. Furthermore, it can regulate the solvation structure of lithium ions in solution, significantly increasing the electrochemical window voltage of the electrolyte. However, among the polyether-based solid electrolytes developed so far, ethylene sulfide electrolytes face the following challenges: First, although ethylene sulfide can regulate the lithium-ion coupling energy... +While coupling with CSC bonds is effective, it cannot effectively regulate the directional and uniform ion flow of lithium ions. For ether-based electrolytes, the lithium-ion solvation structure can be effectively adjusted and the electrochemical window improved, but these electrolytes have poor interfacial compatibility with ternary cathode electrodes, failing to fully function as protective electrodes. Finally, during rate discharge and charging, the positive and negative electrode interfaces cannot be continuously and dynamically monitored, making it impossible to determine the mechanisms and structure-activity relationships of interface problems. Based on the above analysis, there is an urgent need to develop solid-state electrolytes with good mechanical properties, fast lithium-ion transport kinetics, and good solid-liquid compatibility to improve and solve solid-solid interface instability, mitigate side reactions, and thus address the pain points of battery applications causing range anxiety. Summary of the Invention
[0005] In view of the above-mentioned problems in the prior art, the present invention provides a solid electrolyte, which is formed by in-situ polymerization of a mixed slurry; the mixed slurry comprises the following components: a cyclic sulfur monomer, an organic solvent, and a lithium salt; wherein the cyclic sulfur monomer contains a cyclic sulfur ethane group and an ether group, and the lithium salt is a Lewis acid type lithium salt; the lithium salt acts as a Lewis acid catalyst to initiate the ring-opening polymerization of the cyclic sulfur ethane group.
[0006] In some embodiments, the cyclic sulfur monomer is a compound of structural formula 1: Structural formula 1, wherein R is a C1-6 alkylene group.
[0007] In some embodiments, the cyclic sulfur monomer is a compound shown in structural formula 2: Structural formula 2.
[0008] The cyclic sulfur monomer provided by this invention contains a cyclic sulfur ethane group, which can undergo ring-opening polymerization under Lewis acidic conditions. The resulting cross-linked polymer has low crystallinity. At the same time, because the polymer contains CSC bonds, the interaction force with lithium ions is small, which can promote the transport of lithium ions in the polymer network.
[0009] In some embodiments, the organic solvent is a cyclic ether solvent; in some embodiments, the cyclic ether solvent includes tetrahydrofuran and / or 1,3-dioxolane; in some embodiments, the cyclic ether solvent is tetrahydrofuran.
[0010] In some embodiments, the lithium salt is a Lewis acid type lithium salt; in some embodiments, the Lewis acid type lithium salt is at least one of LiPF6, LiBF4, LiBOB, LiDFOB, LiTFSI, or LiFSI; in some embodiments, the Lewis acid type lithium salt is at least one of LiPF6, LiTFSI, or LiFSI.
[0011] In some embodiments, the concentration of lithium salt in the mixed slurry is 0.5M-1.5M; in some embodiments, the concentration of lithium salt in the mixed slurry is 0.8M-1.2M; in some embodiments, the concentration of lithium salt in the mixed slurry is 1M.
[0012] In some embodiments, the volume fraction of the cyclic sulfur monomer is 40%-60% based on the total volume of the monomer and the organic solvent; in some embodiments, the volume fraction of the cyclic sulfur monomer is 50% based on the total volume of the monomer and the organic solvent.
[0013] The lithium salt in this invention is a Lewis acid type lithium salt, which can provide Lewis acid conditions for the ring-opening polymerization of cyclothioethane monomers. Simultaneously, the lithium salt can effectively form a passivated SEI layer, helping to improve the electrochemical window of the battery and thus increasing its cycle life. A small amount of polytetrahydrofuran promotes the formation of a flexible polymer framework, increasing the flexibility of the solid electrolyte and improving its contact surface with the electrode, thereby reducing solid-solid interface resistance and interfacial side reactions.
[0014] The present invention provides a method for preparing the solid electrolyte, comprising the following steps: The cyclic sulfur monomer, organic solvent and lithium salt are mixed to obtain a mixed slurry, and then the mixed slurry is used to initiate a polymerization reaction.
[0015] In some implementations, the polymerization reaction is one or a combination of microwave, light, or thermal polymerization.
[0016] In some embodiments, the polymerization reaction is a thermal polymerization reaction, and the temperature of the thermal polymerization reaction is 40°C-60°C.
[0017] In some embodiments, the cyclic sulfur monomer contains a cyclic sulfur ethane group and an ether group, and the cyclic sulfur monomer is a compound shown in structural formula 2.
[0018] In some embodiments, the volume fraction of the monomer containing cyclothioethane and ether groups is 40%-60% based on the total volume of the monomer and the organic solvent; in some embodiments, the volume fraction of the monomer containing cyclothioethane and ether groups is 50% based on the total volume of the monomer and the organic solvent.
[0019] In some embodiments, the concentration of lithium salt in the mixed slurry is 0.5M-1.5M; in some embodiments, the concentration of lithium salt in the mixed slurry is 0.8M-1.2M; in some embodiments, the concentration of lithium salt in the mixed slurry is 1M.
[0020] In some embodiments, the organic solvent is a cyclic ether solvent; in some embodiments, the cyclic ether solvent is tetrahydrofuran and / or 1,3-dioxolane; in some embodiments, the cyclic ether solvent is tetrahydrofuran.
[0021] In some embodiments, the lithium salt is a Lewis acid type lithium salt; in some embodiments, the Lewis acid type lithium salt is at least one of LiPF6, LiBF4, LiBOB, LiDFOB, LiTFSI, or LiFSI; in some embodiments, the Lewis acid type lithium salt is at least one of LiPF6, LiTFSI, or LiFSI.
[0022] In some embodiments, the preparation process of the cyclic sulfur monomer is as follows: potassium thiocyanate is mixed with 1,4-butanediol glycidyl ether and the organic phase is extracted with anhydrous chloroform; in some embodiments, the organic phase is washed, dried, filtered and evaporated to obtain the cyclic sulfur monomer.
[0023] One aspect of the present invention provides an electrode comprising the solid electrolyte described above or the solid electrolyte prepared by the method described above.
[0024] The present invention provides a lithium-ion energy storage device comprising the aforementioned electrode.
[0025] In some implementations, the lithium-ion energy storage device includes a lithium metal battery, a lithium-ion battery, or a lithium-air battery.
[0026] The present invention has the following beneficial effects: 1) The electrolyte provided by the present invention contains a cyclic sulfur monomer that can undergo ring-opening polymerization under Lewis acidic conditions. The resulting cross-linked polymer has low crystallinity. At the same time, the polymer has low interaction with lithium ions due to the presence of CSC bonds, which promotes the transport of lithium ions in the polymer network. 2) The lithium salt in this invention can effectively form a passivated SEI layer on the surface of the lithium anode, which helps to improve the electrochemical window of the battery, thereby improving the cycle life of the battery. 3) The present invention adds a small amount of polytetrahydrofuran polymer to promote the formation of a flexible polymer skeleton, which increases the flexibility of the solid electrolyte and improves the contact surface between it and the electrode, thereby reducing solid-solid interface resistance and interfacial side reactions. 4) The solid electrolyte prepared by the invention exhibits high ionic conductivity, which can effectively reduce the battery polarization voltage. The battery prepared using the solid electrolyte provided by the invention has a high electrochemical stability window and high stability. At the same time, it can effectively suppress the growth of lithium dendrites and the occurrence of side reactions. Furthermore, the solid electrolyte interface (SEI) film on the surface of the lithium metal anode remains dense and uniform after cycling, thereby extending the battery cycle life. Attached Figure Description
[0027] Figure 1 The ionic conductivity of the electrolytes provided in comparative examples and Examples 1-9 at room temperature (25°C); Figure 2 Linear sweep voltammetry plots of lithium / SS symmetric cells in Examples 2, 5, and 8 at 0.1 mV / s and 25°C are shown. The plots illustrate the current density changes of the electrode materials in Examples 2, 5, and 8 at different voltages, with the electrode material in Example 5 exhibiting a wider electrochemical window. Figure 3 The images show the surface morphology of the lithium metal anode in Li||NCM811 batteries of Examples 2, 5, and 8 after 500 cycles; among them, Figure 3 (a, d, g) are macroscopic images of the surface morphology of the lithium metal anode after 500 cycles of the batteries in Examples 2, 5, and 8, respectively. Figure 3 (b, e, h) are SEM images of the surface of the lithium metal anode of the batteries in Examples 2, 5, and 8 after 500 cycles, observed at 5000x magnification; 3 (c, f, i) are SEM images of the surface of the lithium metal anode of the batteries in Examples 2, 5, and 8 after 500 cycles, observed at 20000x magnification. Detailed Implementation
[0028] The following specific embodiments further illustrate the technical solution of the present invention. These specific embodiments do not represent a limitation on the scope of protection of the present invention. Non-essential modifications and adjustments made by others based on the concept of the present invention still fall within the scope of protection of the present invention.
[0029] Example 1 Example 1 provides a solid electrolyte and its preparation method.
[0030] (1) Synthesis of monomers containing cyclothioethane and ether groups (1,4-butanediol cyclothioethane monomer, cyclothioethane monomer): 19.44 g of potassium thiocyanate was added to 50 mL of deionized water and dissolved completely. Then, 20 g of 1,4-butanediol glycidyl ether was slowly added. The mixture was stirred at room temperature (20-25℃) for 12 hours. After the reaction was completed, the mixture was extracted with anhydrous chloroform, the organic phase was collected, and washed several times with deionized water until the pH of the organic phase mixture was 7. Then, it was dried and filtered with 10 g of anhydrous sodium sulfate. The mixture was then evaporated to obtain a transparent and colorless liquid product. The theoretical yield of the product was calculated based on the mass of 1,4-butanediol glycidyl ether. The yield (%) = actual yield / theoretical yield * 100, and the calculated product yield was 95.8%.
[0031] (2) Preparation of solid electrolyte: The mixture was completely dissolved in a 20 mL reagent bottle with a volume ratio of 4:6 for cyclic sulfur monomer to tetrahydrofuran and a LiFSI concentration of 0.5 M. The resulting slurry was then slowly injected into a positive electrode containing the active material NCM811 within a 6 cm × 6 cm mold. The mold was then placed in a 40 °C constant temperature oven, where the electrolyte was polymerized in situ onto the NCM811 positive electrode to obtain a solid electrolyte.
[0032] All of the above operations were performed in a glove box (oxygen and moisture content both less than 0.1 ppm).
[0033] (3) Ionic conductivity test: In a Swaglok battery mold, using a stainless steel pad (SS) / in-situ polymerized electrolyte / SS battery profile, the ionic conductivity of the solid electrolyte provided in this embodiment was tested at room temperature. The conductivity results are as follows: Figure 1 As shown in Table 1.
[0034] Examples 2-9 The processes of Examples 2 to 9 are the same as those of Example 1, except that the ratio of cyclic sulfur monomers and tetrahydrofuran and the concentration of lithium salt LiFSI are different when preparing solid electrolytes, as detailed in Table 1.
[0035] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that Comparative Example 1 contains only lithium salt and tetrahydrofuran, does not contain the synthesized cyclic sulfur monomer, the concentration of lithium salt LiFSI is 1M, and other operations are the same as in Example 1.
[0036] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that Comparative Example 2 contains only lithium salt and synthesized cyclic sulfur monomers, does not contain tetrahydrofuran, the concentration of lithium salt LiFSI is 1M, and other operations are the same as in Example 1.
[0037] Table 1. Conditions for preparing solid electrolytes in each example and comparative example, and test results of the ionic conductivity of the prepared solid electrolytes.
[0038] Performance testing Based on the ionic conductivity results in Table 1, it can be found that the solid electrolyte exhibits high room temperature ionic conductivity when the lithium salt concentration is 1.0 M. Therefore, the solid electrolytes of Examples 2, 5 and 8 were selected for electrochemical window testing and battery cycle performance testing.
[0039] (1) Electrochemical stability window test Test method: Using a 0.25 mm thick lithium sheet as the working electrode and a 1 mm stainless steel pad (SS) as the electrode, the mixed slurries of Examples 2, 5 and 8 with superior ionic conductivity were injected into the Swagolk battery in the mold (14 mm in size) to assemble lithium / SS symmetric cells. The tests were performed using linear sweep voltammetry (LSV) at 25 °C with a scan rate of 0.1 mV / s.
[0040] Test results: as attached Figure 2 As shown, the electrolyte prepared in Example 5 has an electrochemical stability window of up to 5.3V, which is much higher than that of the sample in Example 2 (4.1V) and the sample in Example 8 (4.8V), indicating that it has higher stability.
[0041] (2) Battery cycle performance test Battery Assembly: Using NCM811 material as the positive electrode and a 0.25 mm thick lithium metal layer as the negative electrode, half-cells were assembled in Swaglok battery molds using the mixed slurries from Examples 2, 5, and 8, respectively. Capacity retention and coulombic efficiency were tested at 25°C and a charge / discharge rate of 0.2C. The test results are shown in Table 2 and... Figure 3 As shown.
[0042] Table 2. Cyclic performance test results of the half-cells prepared from the samples provided in Examples 2, 5, and 8.
[0043] After 500 cycles, the battery prepared using the solid electrolyte of Example 5 exhibited the best cycle performance, with significantly improved capacity retention and coulombic efficiency. Figure 3 It can be seen that the solid electrolyte interface (SEI) film on the surface of the battery negative electrode prepared using the solid electrolyte of Example 5 is more dense and uniform.
Claims
1. A solid electrolyte, characterized in that, The solid electrolyte is formed by polymerization of a mixed slurry, the mixed slurry comprising the following components: Cyclosulfide monomers; Organic solvents; as well as Lithium salts; Wherein, the lithium salt is a Lewis acid type lithium salt, and the cyclic sulfur monomer is the compound shown in structural formula 1: Structural formula 1, in which R is a C1-6 alkylene group.
2. The solid electrolyte according to claim 1, characterized in that, The cyclic sulfur monomer is the compound shown in structural formula 2: Structural formula 2.
3. The solid electrolyte according to claim 1, characterized in that, The mixed slurry satisfies at least one of (a)-(e): (a) The organic solvent is a cyclic ether solvent; (b) The organic solvent is a cyclic ether solvent, wherein the cyclic ether solvent is tetrahydrofuran and / or 1,3-dioxolane; (c) The Lewis acid type lithium salt is at least one of LiPF6, LiBF4, LiBOB, LiDFOB, LiTFSI or LiFSI; (d) The concentration of the lithium salt is 0.5M-1.5M; (e) The volume fraction of the cyclic sulfur monomer is 40%-60% based on the total volume of the monomer and the organic solvent.
4. A method for preparing a solid electrolyte as described in any one of claims 1-3, characterized in that, The cyclic sulfur monomer, organic solvent and lithium salt are mixed to obtain a mixed slurry, and then the mixed slurry is used to initiate a polymerization reaction.
5. The method according to claim 4, characterized in that, The polymerization reaction is one or more combinations of microwave, light, or thermal polymerization.
6. The method according to claim 5, characterized in that, The polymerization reaction is a thermal polymerization reaction, and the temperature of the thermal polymerization reaction is 40℃-60℃.
7. The method according to claim 4, characterized in that, The method for preparing the cyclic sulfur monomer is as follows: potassium thiocyanate is mixed with 1,4-butanediol glycidyl ether and stirred at 20-25°C for 8-15 hours, and the organic phase is collected using chloroform.
8. An electrode, characterized in that, Includes the solid electrolyte as described in any one of claims 1-3 or the solid electrolyte prepared by the method described in claims 4-7.
9. A lithium-ion energy storage device, characterized in that, It includes the electrode as described in claim 8.
10. The lithium-ion energy storage device according to claim 9, characterized in that, The lithium-ion energy storage device includes a lithium metal battery, a lithium-ion battery, or a lithium-air battery.