A lithium trifluoroacetate-containing polymer solid-state electrolyte, a preparation method and applications thereof

Abstract

The application discloses a lithium trifluoroacetate-containing polymer solid electrolyte and a preparation method and application thereof, and relates to the technical field of polymer electrolytes, and specifically discloses a lithium trifluoroacetate-containing polymer solid electrolyte, a preparation method and application thereof, and a lithium trifluoroacetate-containing polymer solid electrolyte is prepared through three steps of preparation of a lithium hydroxide dispersion, preparation of lithium trifluoroacetate and preparation of the lithium trifluoroacetate-containing polymer solid electrolyte.

Description

Technical Field

[0001] This invention belongs to the field of materials science, specifically relating to a polymer solid electrolyte containing lithium trifluoroacetate, its preparation method, and its application. Background Technology

[0002] Lithium metal batteries are considered an ideal choice for next-generation energy storage devices due to their high energy density. However, their development is limited by key issues such as cycle stability and safety, especially the formation of lithium dendrites and the instability of the electrolyte interface. Side reactions constantly occurring at the lithium metal anode-electrolyte interface lead to capacity loss and shorten battery life, while uneven lithium deposition easily induces dendrite growth, increasing the risk of internal short circuits. In liquid batteries, solid electrolyte interfaces (SEIs) rich in inorganic components, especially LiF, have been shown to effectively suppress lithium dendrite formation. This is because the weak affinity (lithium-repellent) between LiF and lithium metal makes it difficult for lithium ions to extend into dendrites outside the interface. Furthermore, the LiF-enriched SEI layer possesses low diffusion energy and high specific surface energy, significantly improving the conductivity of lithium ions and reducing charge transfer impedance. Studies have shown that the reduction of fluorinated inorganic anions can directly form an inorganic-rich SEI layer on the lithium metal surface, while the reduction of fluorinated organic anions forms a mixed organic and inorganic SEI layer. Furthermore, in polymer electrolytes, the reduction reactions of lithium salt, polymer matrix, and solvent must be considered simultaneously, as the organic components formed by solvent reduction may hinder the efficient transport and uniform deposition of lithium ions. Therefore, understanding and optimizing the reduction behavior of each component of the electrolyte is crucial for improving the performance of lithium metal batteries. Currently, there is a technology for preparing a main-chain fluorinated polymer electrolyte FEOP based on the polyfluorinated substituted biepoxide crosslinking agent BEPFB. This electrolyte achieves a LiF-based interfacial layer, resulting in high ionic conductivity and oxidation stability. It is suitable for high-voltage cathodes and solid-state lithium metal pouch batteries, exhibiting excellent cycle performance and practical application prospects (Angewandte Chemie International Edition (DOI:10.1002 / anie.202424685)). However, it has the following drawbacks: the lithium-ion transference number still needs improvement; insufficient lithium-ion transference number leads to significant concentration polarization; it is difficult to suppress the growth of lithium dendrites during long-term charge-discharge cycles; and the synthesis of fluorinated monomers (such as BEPFB) is complex and the raw materials are expensive, posing economic challenges for large-scale application. Furthermore, perfluorinated compounds may cause environmental persistence issues. In addition, although the crosslinking structure enhances stability, it may lead to insufficient electrolyte toughness, which may cause battery failure under abuse conditions such as bending. In addition, patent CN118016989A discloses a method for preparing a fluorinated reinforced polymer electrolyte. The polymer electrolyte prepared by this method is complex and has mediocre electrochemical performance (it can only cycle about 300 times). Summary of the Invention

[0003] (I) Purpose of the Invention

[0004] The purpose of this invention is to provide a polymer solid electrolyte containing lithium trifluoroacetate, its preparation method and application, aiming to solve the technical problems of existing polymer electrolytes such as general electrochemical performance, low ionic conductivity, insufficient cycle stability, and complex preparation methods and poor process controllability.

[0005] (II) Technical Solution

[0006] To address the above problems, a first aspect of the present invention provides a method for preparing a polymer solid electrolyte containing lithium trifluoroacetate, comprising:

[0007] S1, Preparation of lithium hydroxide dispersion: Weigh 0.2-0.5g of lithium hydroxide, dissolve it in 5-10mL of alcohol solvent, and sonicate it under constant temperature to obtain lithium hydroxide dispersion.

[0008] S2, Preparation of lithium trifluoroacetate: 0.5-2 mL of trifluoroacetic acid solution is added dropwise to the lithium hydroxide dispersion, stirred, cooled, and then placed in a vacuum oven for the first drying to obtain a viscous liquid. The viscous liquid is then freeze-dried to obtain powdered lithium trifluoroacetate.

[0009] S3, Preparation of a polymer solid electrolyte containing lithium trifluoroacetate: First, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and polyethylene glycol were dried a second time in a vacuum oven and then stored in an inert gas glove box. Then, 0.1–0.9 g of LiTFSI, 0.2–0.6 g of PVA, and 0.1–0.9 g of lithium trifluoroacetate were weighed and mixed. The mixture was dissolved in 15–30 ml of dimethyl sulfoxide, stirred evenly, and placed in a polytetrafluoroethylene mold. It was then dried a third time in a vacuum oven to obtain a polymer solid electrolyte containing lithium trifluoroacetate. This application uses lithium trifluoroacetate because it preferentially decomposes to form an inorganic interface layer dominated by LiF. This interface structure is dense and highly stable, which is key to improving the cycle life of batteries at room temperature. The strong electronic effect and specific molecular size of the trifluoromethyl group (-CF3) determine its unique decomposition path and final interface composition, which cannot be achieved by other substances. Room temperature cycling test data clearly show that lithium trifluoroacetate is significantly superior to all comparative substances in key indicators such as capacity retention and coulombic efficiency, directly proving its irreplaceable effect.

[0010] Furthermore, the preparation method of lithium trifluoroacetate in step S2 is specifically designed for lithium metal battery electrolyte applications. While there are various synthetic routes for lithium trifluoroacetate (e.g., the metathesis reaction of trifluoroacetic acid with lithium carbonate, or the substitution reaction of its silver salt with lithium chloride), the simple room-temperature acid-base neutralization reaction (LiOH + CF3COOH → CF3COOLi + H2O) employed in this invention is a well-considered approach. The core reason is that this method operates under mild conditions, effectively avoiding the introduction of metallic impurities or decomposition products that may be introduced by high temperatures or complex processes. Simultaneously, by reacting directly in an alcohol solvent, the high purity of the product and the neutrality of the solution can be precisely controlled, thereby minimizing the potential harm of residual acid, alkali, or impurity ions to the stability of the lithium metal anode interface. This is crucial for ensuring excellent cycle life of the battery. Therefore, this synthetic route is an important part of achieving the technical effects of this invention.

[0011] In this application, LiTFSI, PVA, and LiTFA were selected for composite preparation. This was based on a specific design that utilizes the complementary functions of these three components to construct a solid-state electrolyte system with both high ionic conductivity and excellent interfacial stability. LiTFSI provides basic ionic conductivity but suffers from poor interfacial stability. Lithium trifluoroacetate compensates for this deficiency by constructing a fluorine-rich interface but still lacks sufficient ionic conductivity. A strict ratio of these two components is required to achieve a performance balance. PVA, as a matrix, exhibits excellent lithium salt dissociation and ion transport. Furthermore, its dense film-forming properties and ether-free structure endow the system with good mechanical strength and electrochemical stability. Experimental data confirm that any deviation of the component ratio from the specified range leads to interfacial deterioration or a decrease in conductivity. Specifically, excess LiTFSI results in a decrease in cycle life, excess lithium trifluoroacetate leads to a decrease in ionic conductivity, and excess PVA leads to a decrease in coulombic efficiency. Only within the required range can high ionic conductivity, coulombic efficiency, and excellent cycle stability be achieved simultaneously.

[0012] Preferably, in step S1, the constant temperature is 20–40°C, the ultrasonic frequency is 30–50 kHz, and the ultrasonic time is 20–50 minutes. This can be appropriately extended or shortened depending on the actual situation to ensure complete dispersion. To prevent the heat generated during ultrasonic treatment from causing solvent evaporation or unstable reaction conditions, the temperature is set within the range of 20–40°C and can be maintained at a constant temperature using a water bath or cooling device.

[0013] Preferably, in step S2, the first drying temperature is 40–80°C and the first drying time is 6–20 hours, in order to gently remove excess alcohol solvent, so as to ensure that the subsequent freeze-drying process can be carried out effectively and to avoid interference from solvent crystallization.

[0014] Preferably, in step S2, the freeze-drying temperature is -40℃ to -80℃ and the freeze-drying time is 30 to 90 hours, so as to ensure that any residual alcohol solvents that may remain after the first drying are completely removed by sublimation under extremely low temperature conditions, and to avoid their thermal decomposition or residue affecting the purity of the electrolyte.

[0015] Preferably, in step S3, the second drying temperature is 60–90°C and the second drying time is 12–24 hours, which aims to fully remove trace amounts of moisture from the lithium salt and polymer matrix, ensuring that the moisture content is extremely low when assembling the battery, thereby avoiding irreversible damage to the lithium metal anode interface.

[0016] Preferably, the moisture and oxygen content of the glove box are both below 0.1 ppm, and the inert gas includes at least one of nitrogen and argon.

[0017] Preferably, the third drying temperature is 30–60°C and the third drying time is 10–20 hours, so as to completely volatilize the dimethyl sulfoxide solvent during the preparation of the polymer solid electrolyte containing lithium trifluoroacetate, and form a solid electrolyte with complete structure and uniform composition.

[0018] Preferably, the alcohol solvent includes methanol, ethanol, butanol, or isobutanol.

[0019] A second aspect of the present invention provides a polymer solid electrolyte containing lithium trifluoroacetate, wherein the polymer solid electrolyte containing lithium trifluoroacetate is obtained by any of the preparation methods described above.

[0020] A third aspect of the present invention provides the application of a lithium trifluoroacetate-containing polymer solid electrolyte in the preparation of lithium batteries, wherein the lithium trifluoroacetate-containing polymer solid electrolyte is obtained by any of the preparation methods described above.

[0021] (III) Beneficial Effects

[0022] The above-mentioned technical solution of the present invention has the following beneficial technical effects: The present invention provides a polymer solid electrolyte containing lithium trifluoroacetate, its preparation method and application. This method successfully constructs a fluorine-rich interface by introducing LiTFA into a PSA electrolyte, thereby effectively suppressing the formation of lithium dendrites and significantly improving the cycle stability of lithium metal batteries. The method first prepares a lithium hydroxide dispersion, then prepares lithium trifluoroacetate (LiTFA) in situ based on the lithium hydroxide dispersion using an acid-base neutralization reaction, and finally weighs and treats a mixture of LiTFSI, PVA and lithium trifluoroacetate in corresponding proportions in redundant dimethyl sulfoxide to obtain the polymer solid electrolyte containing lithium trifluoroacetate. This method, due to the presence of LiTFA... - With Li + There are high binding energies and TFAs.- Having a high number of donors, these two factors work together to make TFA - Anions can effectively enter the solvation sheath of lithium ions. This structure lowers the migration barrier of Li+, inhibits ion aggregation, increases the concentration of free Li+, and significantly improves the lithium-ion transport efficiency of the electrolyte, thereby enhancing ionic conductivity. Studies have shown that the introduction of LiTFA can preferentially reduce on the surface of the lithium metal anode, forming a LiF-rich solid electrolyte interphase (SEI) layer, effectively improving the cycle life and stability of the battery. Attached Figure Description

[0023] Figure 1 This is a flowchart of the preparation method of the polymer solid electrolyte containing lithium trifluoroacetate according to the present invention;

[0024] Figure 2 Photographs of the polymer solid electrolyte obtained in Example 1 of this invention and its processability;

[0025] Figure 3 A comparison of the surface morphology of the polymer solid electrolytes obtained in Examples 1-4 of this invention;

[0026] Figure 4 The figures show the capacity-voltage curves and performance graphs of the full cells obtained in Examples 1-10 of this invention. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0028] Example 1

[0029] (1) Preparation of lithium hydroxide dispersion

[0030] First, accurately weigh 0.3 g of lithium hydroxide (LiOH) and slowly add it to 10 mL of methanol solution. After adding the lithium hydroxide, thoroughly treat the solution using an ultrasonic device to ensure that the lithium hydroxide is uniformly dispersed in the solvent. Set the ultrasonic frequency to 40 kHz, the treatment time to 30 minutes, and the ultrasonic temperature to 30°C, maintaining a constant temperature using a water bath or cooling device. After ultrasonic treatment, observe whether the solution has achieved a uniform dispersion without obvious particles to ensure its suitability for subsequent reaction or preparation steps.

[0031] (2) Preparation of lithium trifluoroacetate (LiTFA)

[0032] Slowly add 0.932 mL of trifluoroacetic acid solution dropwise to the ultrasonic dispersion of lithium hydroxide obtained in step (1), gently shaking or stirring while adding, until the solution becomes clear and transparent. To ensure a complete reaction, the dropping rate should be slow and continuous stirring should be maintained to prevent localized high concentrations that could lead to uneven reaction. After the solution cools to room temperature, place it in a vacuum oven at 70°C and dry for 12 hours until a viscous liquid is formed. Then, transfer the viscous liquid to a freeze dryer and continue drying at -50°C for 48 hours until completely dried into a uniform powder of lithium trifluoroacetate. The resulting product should be kept away from air to prevent moisture absorption that could affect subsequent use.

[0033] (3) Polymer solid electrolytes containing lithium trifluoroacetate (LiTFA-based polymers can be used to prepare solid electrolytes, abbreviated as PSA-1)

[0034] Before preparing the electrolyte, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and polyethylene glycol (PVA) were dried in a vacuum oven at 70°C for 15 hours and stored in an inert gas glove box. The moisture and oxygen levels in the glove box were both below 0.1 ppm. To prepare the PSA solid electrolyte, 0.4 g PVA, 0.6 g LiTFSI, 0.4 g LiTFA, and 15 ml dimethyl sulfoxide (DMSO) were weighed sequentially in the glove box and stirred overnight at 800 rpm at 60°C. The homogeneous mixture was placed in a polytetrafluoroethylene mold and dried in a vacuum oven at 50°C for more than 12 hours to obtain the PSA-1 electrolyte. Figure 2 -a indicates that the electrolyte is in the form of milky white, round tablets. Figure 2 -b indicates that the electrolyte has good mechanical flexibility, which can effectively suppress lithium dendrites from piercing the electrolyte during cycling and improve the battery's long cycle life.

[0035] Example 2

[0036] (1) Preparation of lithium hydroxide dispersion

[0037] First, accurately weigh 0.3 g of lithium hydroxide (LiOH) and slowly add it to 10 mL of an alcohol solvent. After adding the lithium hydroxide, thoroughly treat the solution using an ultrasonic device to ensure that the lithium hydroxide is uniformly dispersed in the solvent. Set the ultrasonic frequency to 40 kHz, the treatment time to 30 minutes, and the ultrasonic temperature to 30°C, maintaining a constant temperature using a water bath or cooling device. After ultrasonic treatment, observe whether the solution has achieved a uniform dispersion without obvious particles to ensure its suitability for subsequent reaction or preparation steps.

[0038] (2) Preparation of lithium trifluoroacetate (LiTFA)

[0039] Slowly add 0.932 mL of trifluoroacetic acid solution dropwise to the ultrasonic dispersion of lithium hydroxide obtained in step (1), gently shaking or stirring while adding, until the solution becomes clear and transparent. To ensure a complete reaction, the dropping rate should be slow and continuous stirring should be maintained to prevent localized high concentrations that could lead to uneven reaction. After the solution cools to room temperature, place it in a vacuum oven at 70°C and dry for 12 hours until a viscous liquid is formed. Then, transfer the viscous liquid to a freeze dryer and continue drying at -50°C for 48 hours until completely dried into a uniform powder of lithium trifluoroacetate. The resulting product should be kept away from air to prevent moisture absorption that could affect subsequent use.

[0040] (3) Preparation of LiTFA-based polymers as solid electrolytes (PSA-2)

[0041] Before preparing the electrolyte, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and polyethylene glycol (PVA) were dried in a vacuum oven at 70°C for 15 hours and stored in an inert gas glove box. The moisture and oxygen levels in the glove box were both below 0.1 ppm. To prepare the PSA solid electrolyte, 0.4 g PVA, 0.5 g LiTFSI, 0.5 g LiTFA, and 15 ml dimethyl sulfoxide (DMSO) were weighed sequentially in the glove box and stirred overnight at 800 rpm at 60°C. The homogeneous mixture was placed in a polytetrafluoroethylene mold and dried in a vacuum oven at 50°C for more than 12 hours to obtain the PSA-2 electrolyte.

[0042] Example 3

[0043] (1) Preparation of lithium hydroxide dispersion

[0044] First, accurately weigh 0.3 g of lithium hydroxide (LiOH) and slowly add it to 10 mL of an alcohol solvent. The alcohol solvent can be any one of methanol, ethanol, butanol, or isobutanol; the specific choice can be adjusted according to experimental requirements. After adding the lithium hydroxide, thoroughly treat the solution using an ultrasonic device to ensure that the lithium hydroxide is uniformly dispersed in the solvent. Set the ultrasonic frequency to 40 kHz, the treatment time to 30 minutes, and the ultrasonic temperature to 30°C, maintaining a constant temperature using a water bath or cooling device. After ultrasonic treatment, observe whether the solution has achieved a uniform dispersion without obvious particles to ensure its suitability for subsequent reaction or preparation steps.

[0045] (2) Preparation of lithium trifluoroacetate (LiTFA)

[0046] Slowly add 0.932 mL of trifluoroacetic acid solution dropwise to the ultrasonic dispersion of lithium hydroxide obtained in step (1), gently shaking or stirring while adding, until the solution becomes clear and transparent. To ensure a complete reaction, the dropping rate should be slow and continuous stirring should be maintained to prevent localized high concentrations that could lead to uneven reaction. After the solution cools to room temperature, place it in a vacuum oven at 70°C and dry for 12 hours until a viscous liquid is formed. Then, transfer the viscous liquid to a freeze dryer and continue drying at -50°C for 48 hours until completely dried into a uniform powder of lithium trifluoroacetate. The resulting product should be kept away from air to prevent moisture absorption that could affect subsequent use.

[0047] (3) Preparation of LiTFA-based polymers as solid electrolytes (PSA-3)

[0048] Before preparing the electrolyte, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and polyethylene glycol (PVA) were dried in a vacuum oven at 70°C for 15 hours and stored in an inert gas glove box. The moisture and oxygen levels in the glove box were both below 0.1 ppm. To prepare the PSA solid electrolyte, 0.4 g PVA, 0.4 g LiTFSI, 0.6 g LiTFA, and 15 ml dimethyl sulfoxide (DMSO) were weighed sequentially in the glove box and stirred overnight at 800 rpm at 60°C. The homogeneous mixture was placed in a polytetrafluoroethylene mold and dried in a vacuum oven at 50°C for more than 12 hours to obtain the PSA-3 electrolyte.

[0049] Example 4

[0050] (1) Preparation of lithium hydroxide dispersion

[0051] First, accurately weigh 0.3 g of lithium hydroxide (LiOH) and slowly add it to 10 mL of methanol solution. After adding the lithium hydroxide, thoroughly treat the solution using an ultrasonic device to ensure that the lithium hydroxide is uniformly dispersed in the solvent. Set the ultrasonic frequency to 40 kHz, the treatment time to 30 minutes, and the ultrasonic temperature to 30°C, maintaining a constant temperature using a water bath or cooling device. After ultrasonic treatment, observe whether the solution has achieved a uniform dispersion without obvious particles to ensure its suitability for subsequent reaction or preparation steps.

[0052] (2) Preparation of lithium trifluoroacetate (LiTFA)

[0053] Slowly add 0.932 mL of trifluoroacetic acid solution dropwise to the ultrasonic dispersion of lithium hydroxide obtained in step (1), gently shaking or stirring while adding, until the solution becomes clear and transparent. To ensure a complete reaction, the dropping rate should be slow and continuous stirring should be maintained to prevent localized high concentrations that could lead to uneven reaction. After the solution cools to room temperature, place it in a vacuum oven at 70°C and dry for 12 hours until a viscous liquid is formed. Then, transfer the viscous liquid to a freeze dryer and continue drying at -50°C for 48 hours until completely dried into a uniform powder of lithium trifluoroacetate. The resulting product should be kept away from air to prevent moisture absorption that could affect subsequent use.

[0054] (3) Preparation of LiTFA-based polymers as solid electrolytes (PSA-4)

[0055] Before preparing the electrolyte, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and polyethylene glycol (PVA) were dried in a vacuum oven at 70°C for 15 hours and stored in an inert gas glove box. The moisture and oxygen levels in the glove box were both below 0.1 ppm. To prepare the PSA solid electrolyte, 0.4 g PVA, 0.3 g LiTFSI, 0.7 g LiTFA, and 15 ml dimethyl sulfoxide (DMSO) were weighed sequentially in the glove box and stirred overnight at 800 rpm at 60°C. The homogeneous mixture was placed in a polytetrafluoroethylene mold and dried in a vacuum oven at 50°C for more than 12 hours to obtain the PSA-4 electrolyte.

[0056] Example 5

[0057] (1) Preparation of lithium hydroxide dispersion

[0058] First, accurately weigh 0.3 g of lithium hydroxide (LiOH) and slowly add it to 10 mL of methanol solution. After adding the lithium hydroxide, thoroughly treat the solution using an ultrasonic device to ensure that the lithium hydroxide is uniformly dispersed in the solvent. Set the ultrasonic frequency to 40 kHz, the treatment time to 30 minutes, and the ultrasonic temperature to 30°C, maintaining a constant temperature using a water bath or cooling device. After ultrasonic treatment, observe whether the solution has achieved a uniform dispersion without obvious particles to ensure its suitability for subsequent reaction or preparation steps.

[0059] (2) Preparation of lithium trifluoroacetate (LiTFA)

[0060] Slowly add 0.932 mL of trifluoroacetic acid solution dropwise to the ultrasonic dispersion of lithium hydroxide obtained in step (1), gently shaking or stirring while adding, until the solution becomes clear and transparent. To ensure a complete reaction, the dropping rate should be slow and continuous stirring should be maintained to prevent localized high concentrations that could lead to uneven reaction. After the solution cools to room temperature, place it in a vacuum oven at 70°C and dry for 12 hours until a viscous liquid is formed. Then, transfer the viscous liquid to a freeze dryer and continue drying at -50°C for 48 hours until completely dried into a uniform powder of lithium trifluoroacetate. The resulting product should be kept away from air to prevent moisture absorption that could affect subsequent use.

[0061] (3) Preparation of LiTFA-based polymers as solid electrolytes (PSA-5)

[0062] Before preparing the electrolyte, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and polyethylene glycol (PVA) were dried in a vacuum oven at 70°C for 15 hours and stored in an inert gas glove box. The moisture and oxygen levels in the glove box were both below 0.1 ppm. To prepare the PSA solid electrolyte, 0.4 g PVA, 0.2 g LiTFSI, 0.8 g LiTFA, and 15 ml dimethyl sulfoxide (DMSO) were weighed sequentially in the glove box and stirred overnight at 800 rpm at 60°C. The homogeneous mixture was placed in a polytetrafluoroethylene mold and dried in a vacuum oven at 50°C for more than 12 hours to obtain the PSA-5 electrolyte.

[0063] Example 6

[0064] (1) Preparation of lithium hydroxide dispersion

[0065] First, accurately weigh 0.3 g of lithium hydroxide (LiOH) and slowly add it to 10 mL of methanol solution. After adding the lithium hydroxide, thoroughly treat the solution using an ultrasonic device to ensure that the lithium hydroxide is uniformly dispersed in the solvent. Set the ultrasonic frequency to 40 kHz, the treatment time to 30 minutes, and the ultrasonic temperature to 30°C, maintaining a constant temperature using a water bath or cooling device. After ultrasonic treatment, observe whether the solution has achieved a uniform dispersion without obvious particles to ensure its suitability for subsequent reaction or preparation steps.

[0066] (2) Preparation of lithium trifluoroacetate (LiTFA)

[0067] Slowly add 0.932 mL of trifluoroacetic acid solution dropwise to the ultrasonic dispersion of lithium hydroxide obtained in step (1), gently shaking or stirring while adding, until the solution becomes clear and transparent. To ensure a complete reaction, the dropping rate should be slow and continuous stirring should be maintained to prevent localized high concentrations that could lead to uneven reaction. After the solution cools to room temperature, place it in a vacuum oven at 70°C and dry for 12 hours until a viscous liquid is formed. Then, transfer the viscous liquid to a freeze dryer and continue drying at -50°C for 48 hours until completely dried into a uniform powder of lithium trifluoroacetate. The resulting product should be kept away from air to prevent moisture absorption that could affect subsequent use.

[0068] (3) Preparation of LiTFA-based polymers as solid electrolytes (PSA-6)

[0069] Before preparing the electrolyte, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and polyethylene glycol (PVA) were dried in a vacuum oven at 70°C for 15 hours and stored in an inert gas glove box. The moisture and oxygen levels in the glove box were both below 0.1 ppm. To prepare the PSA solid electrolyte, 0.4 g PVA, 0.1 g LiTFSI, 0.9 g LiTFA, and 15 ml dimethyl sulfoxide (DMSO) were weighed sequentially in the glove box and stirred overnight at 800 rpm at 60°C. The homogeneous mixture was placed in a polytetrafluoroethylene mold and dried in a vacuum oven at 50°C for more than 12 hours to obtain the PSA-6 electrolyte.

[0070] Example 7

[0071] (1) Preparation of lithium hydroxide dispersion

[0072] First, accurately weigh 0.3 g of lithium hydroxide (LiOH) and slowly add it to 10 mL of methanol solution. After adding the lithium hydroxide, thoroughly treat the solution using an ultrasonic device to ensure that the lithium hydroxide is uniformly dispersed in the solvent. Set the ultrasonic frequency to 40 kHz, the treatment time to 30 minutes, and the ultrasonic temperature to 30°C, maintaining a constant temperature using a water bath or cooling device. After ultrasonic treatment, observe whether the solution has achieved a uniform dispersion without obvious particles to ensure its suitability for subsequent reaction or preparation steps.

[0073] (2) Preparation of lithium trifluoroacetate (LiTFA)

[0074] Slowly add 0.932 mL of trifluoroacetic acid solution dropwise to the ultrasonic dispersion of lithium hydroxide obtained in step (1), gently shaking or stirring while adding, until the solution becomes clear and transparent. To ensure a complete reaction, the dropping rate should be slow and continuous stirring should be maintained to prevent localized high concentrations that could lead to uneven reaction. After the solution cools to room temperature, place it in a vacuum oven at 70°C and dry for 12 hours until a viscous liquid is formed. Then, transfer the viscous liquid to a freeze dryer and continue drying at -50°C for 48 hours until completely dried into a uniform powder of lithium trifluoroacetate. The resulting product should be kept away from air to prevent moisture absorption that could affect subsequent use.

[0075] (3) Preparation of LiTFA-based polymers as solid electrolytes (PSA-7)

[0076] Before preparing the electrolyte, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and polyethylene glycol (PVA) were dried in a vacuum oven at 70°C for 15 hours and stored in an inert gas glove box. The moisture and oxygen levels in the glove box were both below 0.1 ppm. To prepare the PSA solid electrolyte, 0.4 g PVA, 0.7 g LiTFSI, 0.3 g LiTFA, and 15 ml dimethyl sulfoxide (DMSO) were weighed sequentially in the glove box and stirred overnight at 800 rpm at 60°C. The homogeneous mixture was placed in a polytetrafluoroethylene mold and dried in a vacuum oven at 50°C for more than 12 hours to obtain the PSA-7 electrolyte.

[0077] Example 8

[0078] (1) Preparation of lithium hydroxide dispersion

[0079] First, accurately weigh 0.3 g of lithium hydroxide (LiOH) and slowly add it to 10 mL of methanol solution. After adding the lithium hydroxide, thoroughly treat the solution using an ultrasonic device to ensure that the lithium hydroxide is uniformly dispersed in the solvent. Set the ultrasonic frequency to 40 kHz, the treatment time to 30 minutes, and the ultrasonic temperature to 30°C, maintaining a constant temperature using a water bath or cooling device. After ultrasonic treatment, observe whether the solution has achieved a uniform dispersion without obvious particles to ensure its suitability for subsequent reaction or preparation steps.

[0080] (2) Preparation of lithium trifluoroacetate (LiTFA)

[0081] Slowly add 0.932 mL of trifluoroacetic acid solution dropwise to the ultrasonic dispersion of lithium hydroxide obtained in step (1), gently shaking or stirring while adding, until the solution becomes clear and transparent. To ensure a complete reaction, the dropping rate should be slow and continuous stirring should be maintained to prevent localized high concentrations that could lead to uneven reaction. After the solution cools to room temperature, place it in a vacuum oven at 70°C and dry for 12 hours until a viscous liquid is formed. Then, transfer the viscous liquid to a freeze dryer and continue drying at -50°C for 48 hours until completely dried into a uniform powder of lithium trifluoroacetate. The resulting product should be kept away from air to prevent moisture absorption that could affect subsequent use.

[0082] (3) Preparation of LiTFA-based polymers as solid electrolytes (PSA-8)

[0083] Before preparing the electrolyte, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and polyethylene glycol (PVA) were dried in a vacuum oven at 70°C for 15 hours and stored in an inert gas glove box. The moisture and oxygen levels in the glove box were both below 0.1 ppm. To prepare the PSA solid electrolyte, 0.4 g PVA, 0.8 g LiTFSI, 0.2 g LiTFA, and 15 ml dimethyl sulfoxide (DMSO) were weighed sequentially in the glove box and stirred overnight at 800 rpm at 60°C. The homogeneous mixture was placed in a polytetrafluoroethylene mold and dried in a vacuum oven at 50°C for more than 12 hours to obtain the PSA-8 electrolyte.

[0084] Example 9

[0085] (1) Preparation of lithium hydroxide dispersion

[0086] First, accurately weigh 0.3 g of lithium hydroxide (LiOH) and slowly add it to 10 mL of methanol solution. After adding the lithium hydroxide, thoroughly treat the solution using an ultrasonic device to ensure that the lithium hydroxide is uniformly dispersed in the solvent. Set the ultrasonic frequency to 40 kHz, the treatment time to 30 minutes, and the ultrasonic temperature to 30°C, maintaining a constant temperature using a water bath or cooling device. After ultrasonic treatment, observe whether the solution has achieved a uniform dispersion without obvious particles to ensure its suitability for subsequent reaction or preparation steps.

[0087] (2) Preparation of lithium trifluoroacetate (LiTFA)

[0088] Slowly add 0.932 mL of trifluoroacetic acid solution dropwise to the ultrasonic dispersion of lithium hydroxide obtained in step (1), gently shaking or stirring while adding, until the solution becomes clear and transparent. To ensure a complete reaction, the dropping rate should be slow and continuous stirring should be maintained to prevent localized high concentrations that could lead to uneven reaction. After the solution cools to room temperature, place it in a vacuum oven at 70°C and dry for 12 hours until a viscous liquid is formed. Then, transfer the viscous liquid to a freeze dryer and continue drying at -50°C for 48 hours until completely dried into a uniform powder of lithium trifluoroacetate. The resulting product should be kept away from air to prevent moisture absorption that could affect subsequent use.

[0089] (3) Preparation of LiTFA-based polymers as solid electrolytes (PSA-9)

[0090] Before preparing the electrolyte, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and polyethylene glycol (PVA) were dried in a vacuum oven at 70°C for 15 hours and stored in an inert gas glove box. The moisture and oxygen levels in the glove box were both below 0.1 ppm. To prepare the PSA solid electrolyte, 0.4 g PVA, 0.9 g LiTFSI, 0.1 g LiTFA, and 15 ml dimethyl sulfoxide (DMSO) were weighed sequentially in the glove box and stirred overnight at 800 rpm at 60°C. The homogeneous mixture was placed in a polytetrafluoroethylene mold and dried in a vacuum oven at 50°C for more than 12 hours to obtain the PSA-9 electrolyte.

[0091] Example 10

[0092] (1) Preparation of lithium hydroxide dispersion

[0093] First, accurately weigh 0.3 g of lithium hydroxide (LiOH) and slowly add it to 10 mL of methanol solution. After adding the lithium hydroxide, thoroughly treat the solution using an ultrasonic device to ensure that the lithium hydroxide is uniformly dispersed in the solvent. Set the ultrasonic frequency to 40 kHz, the treatment time to 30 minutes, and the ultrasonic temperature to 30°C, maintaining a constant temperature using a water bath or cooling device. After ultrasonic treatment, observe whether the solution has achieved a uniform dispersion without obvious particles to ensure its suitability for subsequent reaction or preparation steps.

[0094] (2) Preparation of lithium trifluoroacetate (LiTFA)

[0095] Slowly add 0.932 mL of trifluoroacetic acid solution dropwise to the ultrasonic dispersion of lithium hydroxide obtained in step (1), gently shaking or stirring while adding, until the solution becomes clear and transparent. To ensure a complete reaction, the dropping rate should be slow and continuous stirring should be maintained to prevent localized high concentrations that could lead to uneven reaction. After the solution cools to room temperature, place it in a vacuum oven at 70°C and dry for 12 hours until a viscous liquid is formed. Then, transfer the viscous liquid to a freeze dryer and continue drying at -50°C for 48 hours until completely dried into a uniform powder of lithium trifluoroacetate. The resulting product should be kept away from air to prevent moisture absorption that could affect subsequent use.

[0096] (3) Preparation of LiTFA-based polymers as solid electrolytes (PSA-10)

[0097] Before preparing the electrolyte, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and polyethylene glycol (PVA) were dried in a vacuum oven at 70°C for 15 hours and stored in an inert gas glove box. The moisture and oxygen levels in the glove box were both below 0.1 ppm. To prepare the PSA solid electrolyte, 0.5 g PVA, 0.6 g LiTFSI, 0.4 g LiTFA, and 15 ml dimethyl sulfoxide (DMSO) were weighed sequentially in the glove box and stirred overnight at 800 rpm at 60°C. The homogeneous mixture was placed in a polytetrafluoroethylene mold and dried in a vacuum oven at 50°C for more than 12 hours to obtain the PSA-10 electrolyte.

[0098] Comparative Example 1

[0099] Unlike Example 1, Comparative Example 1 only added lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). Before preparing the electrolyte, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and polyethylene glycol (PVA) were dried in a vacuum oven at 70°C for 15 hours and stored in an inert gas glove box. The moisture and oxygen levels in the glove box were both below 0.1 ppm. To prepare the PS solid electrolyte, 0.4 g of PVA, 1 g of LiTFSI, and 15 ml of dimethyl sulfoxide (DMSO) were weighed sequentially in the glove box and stirred overnight at 800 rpm at 60°C. The homogeneous mixture was placed in a polytetrafluoroethylene mold and dried in a vacuum oven at 50°C for 12 hours to obtain the PS solid electrolyte.

[0100] Comparative Example 2

[0101] Unlike Example 2, Comparative Example 2 only added lithium trifluoroacetate (LiTFA). Before preparing the electrolyte, lithium trifluoroacetate (LiTFA) and polyethylene glycol (PVA) were dried in a vacuum oven at 70°C for 15 hours and stored in an inert gas glove box. The moisture and oxygen levels in the glove box were both below 0.1 ppm. To prepare the PA solid electrolyte, 0.4 g PVA, 1 g LiTFA, and 15 ml dimethyl sulfoxide (DMSO) were weighed sequentially in the glove box and stirred overnight at 800 rpm at 60°C. The homogeneous mixture was placed in a polytetrafluoroethylene mold and dried in a vacuum oven at 50°C for 12 hours to obtain the PA solid electrolyte.

[0102] Comparative Example 3

[0103] (1) Preparation of lithium hydroxide dispersion

[0104] First, accurately weigh 0.3 g of lithium hydroxide (LiOH) and slowly add it to 10 mL of methanol solution. After adding the lithium hydroxide, thoroughly treat the solution using an ultrasonic device to ensure that the lithium hydroxide is uniformly dispersed in the solvent. Set the ultrasonic frequency to 40 kHz, the treatment time to 30 minutes, and the ultrasonic temperature to 30°C, maintaining a constant temperature using a water bath or cooling device. After ultrasonic treatment, observe whether the solution has achieved a uniform dispersion without obvious particles to ensure its suitability for subsequent reaction or preparation steps.

[0105] (2) Preparation of lithium tetrafluoropropionate (LiTFPA)

[0106] Slowly add 1.17 mL of tetrafluoropropionic acid solution to the ultrasonic dispersion of lithium hydroxide obtained in step (1), gently shaking or stirring while adding, until the solution becomes clear and transparent. To ensure a complete reaction, the addition rate should be slow and continuous stirring should be maintained to prevent localized high concentrations that could lead to uneven reaction. After the solution cools to room temperature, place it in a vacuum oven at 70°C and dry for 12 hours until a viscous liquid is formed. Then, transfer the viscous liquid to a freeze dryer and continue drying at -50°C for 48 hours until completely dried into a uniform powder of lithium trifluoroacetate. The resulting product should be kept away from air to prevent moisture absorption that could affect subsequent use.

[0107] (3) Preparation of LiTFPA-based polymers for solid electrolytes (PSPs)

[0108] Before preparing the electrolyte, lithium tetrafluoropropionate (LiTFPA) and polyethylene glycol (PVA) were dried in a vacuum oven at 70°C for 15 hours and stored in an inert gas glove box. The moisture and oxygen levels in the glove box were both below 0.1 ppm. To prepare the PSA solid electrolyte, 0.4 g PVA, 0.6 g LiTFPA, 0.4 g LiTFA, and 15 ml dimethyl sulfoxide (DMSO) were weighed sequentially in the glove box and stirred overnight at 800 rpm at 60°C. The homogeneous mixture was then placed in a polytetrafluoroethylene mold and dried in a vacuum oven at 50°C for more than 12 hours to obtain the PSP electrolyte.

[0109] Comparative Example 4

[0110] (1) Preparation of lithium hydroxide dispersion

[0111] First, accurately weigh 0.3 g of lithium hydroxide (LiOH) and slowly add it to 10 mL of methanol solution. After adding the lithium hydroxide, thoroughly treat the solution using an ultrasonic device to ensure that the lithium hydroxide is uniformly dispersed in the solvent. Set the ultrasonic frequency to 40 kHz, the treatment time to 30 minutes, and the ultrasonic temperature to 30°C, maintaining a constant temperature using a water bath or cooling device. After ultrasonic treatment, observe whether the solution has achieved a uniform dispersion without obvious particles to ensure its suitability for subsequent reaction or preparation steps.

[0112] (2) Preparation of lithium pentafluoropropionate (LiPFPA)

[0113] Slowly add 1.32 mL of pentafluoropropionic acid solution to the ultrasonic dispersion of lithium hydroxide obtained in step (1), gently shaking or stirring while adding, until the solution becomes clear and transparent. To ensure a complete reaction, the addition rate should be slow and continuous stirring should be maintained to prevent localized high concentrations that could lead to uneven reaction. After the solution cools to room temperature, place it in a vacuum oven at 70°C and dry for 12 hours until a viscous liquid is formed. Then, transfer the viscous liquid to a freeze dryer and continue drying at -50°C for 48 hours until completely dried into a uniform powder of lithium trifluoroacetate. The resulting product should be kept away from air to prevent moisture absorption that could affect subsequent use.

[0114] (3) Preparation of LiPFPA-based polymers as solid electrolytes (PSFs)

[0115] Before preparing the electrolyte, lithium pentafluoropropionate (LiPFPA) and polyethylene glycol (PVA) were dried in a vacuum oven at 70°C for 15 hours and stored in an inert gas glove box. The moisture and oxygen levels in the glove box were both below 0.1 ppm. To prepare the PSA solid electrolyte, 0.4 g PVA, 0.6 g LiPFPA, 0.4 g LiTFA, and 15 ml dimethyl sulfoxide (DMSO) were weighed sequentially in the glove box and stirred overnight at 800 rpm at 60°C. The homogeneous mixture was then placed in a polytetrafluoroethylene mold and dried in a vacuum oven at 50°C for more than 12 hours to obtain the PSF electrolyte.

[0116] Figure 3 The comparison of ad shows that the electrolyte surface without lithium plating stripping treatment is relatively smooth. This indicates that the surface of PSA-1 electrolyte is more uniform and has fewer cracks than PSA-2, PSA-3, and PSA-4 electrolytes. This not only increases the contact area with the lithium anode and cathode but also provides favorable conditions for uniform lithium ion deposition. Figure 1e shows the surface morphology of the electrolyte and electrodes after cycling. The surface morphology of PSA-1 electrolyte after cycling shows almost no lithium deposit particles. Similarly, the lithium anode surface remains relatively smooth and flat overall. In the case of PSA-2 electrolyte, however, lithium dendrites grow significantly on its surface and on the lithium anode, resulting in a large amount of uneven lithium deposition. PSA-3 and PSA-4 electrolytes also exhibit similar phenomena. Therefore, compared with PSA-2, PSA-3, and PSA-4 electrolytes, PSA-1 electrolyte shows a better effect in suppressing lithium dendrite growth. Figure 4 Figures a and b show the capacity-voltage curves of PSA-2 and PSA-1 full cells, respectively; (c) represents the performance of PSA-1 to PSA-10 full cells at 0.5C. The comparison in Figures a and b illustrates that as the number of cycles exceeds 200, the PSA-1 full cell maintains a relatively stable charge-discharge voltage plateau, while the charge-discharge plateau curve of the PSA-2 full cell clearly transforms into an arc shape, accompanied by a sharp decrease in capacity. This observation indicates that although the PSA-1 full cell exhibits a higher overpotential in the initial cycling phase, it demonstrates superior stability and battery performance during long-term cycling. Conversely, although the PSA-2 full cell has a lower initial overpotential, its charge-discharge plateau stability is poor, ultimately leading to a significant decrease in capacity.

[0117] Figure c clearly illustrates the impact of different PSA systems on battery performance. At 0.5C rate, the PSA-1 full cell exhibits the best overall performance, with an initial capacity of 145.3 mAh / g and a capacity retention of 88.7% after 500 cycles, while maintaining a coulombic efficiency above 99.9%. This result demonstrates that the optimized electrolyte composition can establish a stable lithium-ion transport solvation structure, promoting the formation of a dense SEI layer rich in inorganic fluorides, thereby effectively suppressing lithium dendrite growth and achieving a highly efficient lithium deposition / stripping process.

[0118] In contrast, while the PSA-2 full cell boasts a relatively high initial capacity of 151.4 mAh / g, its average coulombic efficiency is only 97.12%, and its capacity retention is below 80%. This indicates that its SEI layer structure is loose and rich in organic components, failing to effectively prevent the continuous occurrence of interfacial side reactions. The PSA-3 full cell, due to its excessively high intrinsic electrolyte impedance, has an initial capacity of only 102.9 mAh / g, demonstrating severely limited ion transport kinetics. In the PSA-4 to PSA-5 systems, the battery capacity decreases with increasing LiTFA content; while when the LiTFSI content increases (PSA-6 to PSA-9), although the initial capacity remains high, the capacity rapidly decays due to decreased interfacial stability. In Example 10, the increased PVA content led to a significant decrease in the system's ionic conductivity. These comparative results fully demonstrate the equal importance of electrolyte composition balance for achieving high ionic conductivity and a stable interfacial layer; any deviation from these components will lead to a significant decrease in battery performance.

[0119] Meanwhile, the comparative analysis of the data in Table 2 shows that although Comparative Example 1 (PS system) has the highest conductivity, its capacity retention rate decays to 80.6% after 200 cycles, proving that a single lithium salt system cannot simultaneously achieve high ion conductivity and interface stability. Comparative Example 2 (PA system) is limited by its extremely low ion conductivity, resulting in poor actual capacity and cycle performance. Comparative Example 3 (PSP system) and Comparative Example 4 (PSF system) have capacity retention rates of 84.2% and 85.4% respectively after 400 cycles, which are better than Comparative Examples 1 and 2, but still significantly lower than Example 1, and have shorter cycle periods. These comparative results fully verify the synergistic effect of the LiTFSI and LiTFA dual-salt system with the PVA matrix: the balanced structure achieved through precise proportioning can maintain sufficient ion conductivity and construct a stable electrode / electrolyte interface, thereby significantly improving the long cycle life of the battery.

[0120] Table 1 Comparison of the electrochemical performance of batteries in Examples 1-10

[0121]

[0122] Table 2 compares the electrochemical performance of batteries in Comparative Examples 1-4 (including Example 1).

[0123]

[0124] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. A method for preparing a polymer solid electrolyte containing lithium trifluoroacetate, characterized in that, include: S1, Preparation of lithium hydroxide dispersion: Weigh 0.2-0.5g of lithium hydroxide, dissolve it in 5-10mL of alcohol solvent, and sonicate it under constant temperature to obtain lithium hydroxide dispersion. S2, Preparation of lithium trifluoroacetate: 0.5-2 mL of trifluoroacetic acid solution is added dropwise to the lithium hydroxide dispersion, stirred, cooled, and then placed in a vacuum oven for the first drying to obtain a viscous liquid. The viscous liquid is then freeze-dried to obtain powdered lithium trifluoroacetate. S3, Preparation of polymer solid electrolyte containing lithium trifluoroacetate: First, LiTFSI and PVA were dried a second time in a vacuum oven and then stored in an inert gas glove box. Then, 0.1-0.9g of LiTFSI, 0.2-0.6g of PVA and 0.1-0.9g of powdered lithium trifluoroacetate were weighed and mixed. The mixture was dissolved in 15-30ml of dimethyl sulfoxide, stirred evenly, placed in a polytetrafluoroethylene mold, and then placed in a vacuum oven for a third drying to obtain the polymer solid electrolyte containing lithium trifluoroacetate.

2. The method for preparing the polymer solid electrolyte containing lithium trifluoroacetate according to claim 1, characterized in that, In step S1, the constant temperature is 20–40°C, the ultrasonic frequency is 30–50 kHz, and the ultrasonic time is 20–50 minutes.

3. The method for preparing the polymer solid electrolyte containing lithium trifluoroacetate according to claim 1, characterized in that, In step S2, the first drying temperature is 40–80°C, and the first drying time is 6–20 hours.

4. The method for preparing the polymer solid electrolyte containing lithium trifluoroacetate according to claim 1, characterized in that, In step S2, the freeze-drying temperature is -40℃ to -80℃, and the freeze-drying time is 30 to 90 hours.

5. The method for preparing the polymer solid electrolyte containing lithium trifluoroacetate according to claim 1, characterized in that, In step S3, the second drying temperature is 60–90°C, and the second drying time is 12–24 hours.

6. The method for preparing the polymer solid electrolyte containing lithium trifluoroacetate according to claim 1, characterized in that, The glove box has a moisture and oxygen content of less than 0.1 ppm, and the inert gas includes at least one of nitrogen and argon.

7. The method for preparing the polymer solid electrolyte containing lithium trifluoroacetate according to claim 1, characterized in that, The third drying temperature is 30-60℃, and the third drying time is 10-20 hours.

8. The method for preparing the polymer solid electrolyte containing lithium trifluoroacetate according to claim 1, characterized in that, The alcohol solvents include methanol, ethanol, butanol, or isobutanol.

9. A polymer solid electrolyte containing lithium trifluoroacetate, characterized in that, The polymer solid electrolyte containing lithium trifluoroacetate is obtained by the preparation method according to any one of claims 1-8.

10. The application of a polymer solid electrolyte containing lithium trifluoroacetate in the preparation of lithium batteries, characterized in that, The polymer solid electrolyte containing lithium trifluoroacetate is obtained by the preparation method according to any one of claims 1-8.

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