Solid-state electrolyte filler, preparation method of solid-state electrolyte and solid-state battery

Abstract

The invention provides a solid electrolyte filler, a preparation method of a solid electrolyte and a solid-state battery, and the preparation method comprises the following steps: adding 1, 3-diaminoguanidine hydrochloride into ethanol for dissolving to obtain a first mixed solution; adding nitrosalicylaldehyde into the first mixed solution to obtain a second mixed solution; and carrying out solid-liquid separation on the second mixed solution to obtain the first solid electrolyte filler. The first solid electrolyte filler can be compounded with polyoxyethylene to prepare a solid electrolyte, after anions are separated, vacancies of cations are anchored to TFSI-, charges are transferred to the TFSI-, breakage of C-F bonds is promoted, lithium fluoride is formed, chloride ions contained in the filler can be combined with lithium ions to form lithium chloride, then SEI of composite phase LiF-LiCl is generated, and the solid electrolyte is prepared. The SEI layer generated by the solid electrolyte with higher lithium fluoride content at the same temperature has lower lithium deposition nucleation overpotential, higher lithium cycle stability and longer lithium metal total battery cycle life.

Description

Technical Field

[0001] The present application belongs to the technical field of battery manufacturing, and in particular relates to a solid electrolyte filler, a method for preparing a solid electrolyte, and a solid-state battery. Background Art

[0002] Polymer solid electrolytes, represented by polyethylene oxide (PEO), have attracted considerable attention in the field of solid-state lithium metal batteries due to their excellent processing properties and interfacial compatibility with lithium metal. However, due to the active chemical properties of lithium metal, the lithium anode easily reacts with the electrolyte, spontaneously forming a solid electrolyte interface (SEI) layer. This SEI layer, due to its poor mechanical properties, repeatedly breaks and repairs itself in situ on the lithium anode, making it difficult to resist the growth and penetration of lithium dendrites, leading to capacity degradation and lifespan reduction.

[0003] Studies have shown that the LiF-rich solid electrolyte interface (SEI) layer can give lithium metal batteries multiple performance advantages, including high elastic modulus to resist electrode volume deformation, wide bandgap characteristics to suppress electron tunneling, and low lithium ion diffusion energy barrier to promote uniform lithium ion transport.

[0004] However, this application found that while fluorinated SEI can improve battery performance, a higher degree of fluorination may mean continued electrolyte side reactions, which may have a negative impact on the long-term stability and performance of the battery. Moreover, under fast charging and high temperature conditions, the low ionic conductivity and high interfacial impedance of the fluorinated SEI also expose instability, limiting the application of batteries at high temperatures or high loads. Summary of the Invention

[0005] In the prior art, the fluorination degree of the SEI layer is too high, which will lead to problems such as low ion conductivity and high interface impedance.

[0006] To solve the above technical problems, according to some embodiments, the present application provides a method for preparing a solid electrolyte filler, which is used as a filler for preparing an electrolyte based on polyethylene oxide and lithium bis(trifluoromethanesulfonyl)imide, comprising:

[0007] Ethanol and water are mixed to obtain an ethanol-water solution; 1,3-diaminoguanidine hydrochloride is added to the ethanol-water solution to dissolve to obtain a first mixed solution; nitrosalicylicylaldehyde is added to the first mixed solution, and the mixture is heated to reflux for a first preset time to obtain a second mixed solution; the molar ratio of the 1,3-diaminoguanidine hydrochloride to the nitrosalicylicylaldehyde is 1:2; the second mixed solution is subjected to solid-liquid separation, and the separated solid matter is washed and dried to obtain a first solid electrolyte filler.

[0008] Furthermore, the volume ratio of ethanol to water in the ethanol aqueous solution is 7:1;

[0009] The molar concentration of 1,3-diaminoguanidine hydrochloride in the first mixed solution is 0.078 mol / L.

[0010] Furthermore, the reaction conditions for adding 1,3-diaminoguanidine hydrochloride to the ethanol aqueous solution for dissolution are: stirring at room temperature for 2 hours until dissolved.

[0011] Furthermore, the solid-liquid separation of the second mixed liquid and washing and drying the separated solid matter comprises: washing the solid matter with pure water, anhydrous ethanol and ether in sequence, and then drying in vacuum.

[0012] Furthermore, the first solid electrolyte filler is added to a saturated sodium fluoride aqueous solution and stirred to obtain a third mixed solution, wherein the mass volume ratio of the first solid electrolyte filler to the saturated sodium fluoride aqueous solution is 8 g / ml; the third mixed solution is subjected to solid-liquid separation, and the separated solid matter is dried to obtain a powdered second solid electrolyte filler.

[0013] Furthermore, the step of adding the first solid electrolyte filler to a saturated sodium fluoride aqueous solution and stirring the mixture comprises: stirring at 60° C. for 72 hours; wherein the sodium fluoride solution is replaced every 24 hours;

[0014] The solid matter after separation was dried under vacuum at 90°C for 12 hours.

[0015] On the other hand, the present application proposes a method for preparing a solid electrolyte, comprising: vacuum drying polyethylene oxide and lithium bistrifluoromethanesulfonylimide with a molecular weight of 600,000, respectively, at a temperature of 60°C for 12 hours; weighing polyethylene oxide and lithium bistrifluoromethanesulfonylimide, wherein the molar ratio of the polyethylene oxide unit to the lithium ion in the lithium bistrifluoromethanesulfonylimide is 10:1; mixing polyethylene oxide, lithium bistrifluoromethanesulfonylimide and the first solid electrolyte filler in any of the above technical solutions; wherein the first solid electrolyte filler accounts for 1-3% of the total mass; injecting anhydrous acetonitrile solvent into the mixture and stirring to obtain a first slurry; forming the first slurry in a mold to obtain an electrolyte membrane; allowing the electrolyte membrane to stand at room temperature to volatilize the solvent; and baking the electrolyte membrane under vacuum to remove residual solvent at a baking temperature of 60°C to obtain a solid electrolyte.

[0016] Another aspect of the present application provides a solid-state battery, comprising a positive electrode sheet, a negative electrode sheet, and the solid electrolyte of the above technical solution arranged between the positive electrode sheet and the negative electrode sheet.

[0017] The present invention uses the first solid electrolyte filler (DG-Cl) with optimized structure as polymer matrix filler, which can be compounded with polyethylene oxide (PEO, specification Mw ~ 600000) to prepare solid electrolyte. The electron delocalization effect on TFSI is analyzed by cyclic voltammetry (CV) and XPS analysis results. - Catalytic mechanism of anion decomposition: after the anion is separated, the vacant cation anchors TFSI - , charge is transferred to TFSI - It promotes the breaking of the CF bond and then generates the SEI of the composite phase LiF-LiCl. At the same temperature, the SEI layer produced by the solid electrolyte with higher fluorination degree (taking the electrolyte PEO-DG-F prepared with the second solid electrolyte filler DG-F as an example) has lower lithium deposition nucleation overpotential, higher lithium cycle stability and longer lithium metal full battery cycle life. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the traditional technology, the following is a brief introduction to the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0019] Figure 1 This is the synthetic route of DG-Cl and DG-F in one embodiment of the present application.

[0020] Figure 2 (a) is the infrared spectrum of DG-X, and (b) is the nuclear magnetic resonance spectrum of DG-Cl and DG-F.

[0021] Figure 3 These are the scanning electron microscope images and elemental analysis spectra of DG-F and DG-Cl.

[0022] Figure 4 It is the ionic conductivity of different solid electrolytes and PEO-based polymer solid electrolytes.

[0023] Figure 5 These are the impedance spectra of different solid electrolytes at different temperatures.

[0024] Figure 6 This is a comparison chart of the crystallinity of different solid electrolytes.

[0025] Figure 7 This is a comparison chart of electrolyte Tg of different solid electrolytes.

[0026] Figure 8 These are infrared spectra of different solid electrolytes.

[0027] Figure 9 (a) is a comparison diagram of the electrostatic potential of DG and TG, and (b) is a comparison diagram of the binding energy of DG and TG.

[0028] Figure 10 Figure 2 is a graph of lithium ion migration of Li / CSEs / Li batteries prepared with different solid electrolytes.

[0029] Figure 11 This is the electrochemical window comparison of Li / CSEs / SS.

[0030] Figure 12 These are the XPS spectra of different composite solid electrolytes.

[0031] Figure 13 The TOF-SIMS spectrum of LiF2 is the SEI on the lithium surface after Li / CSEs / Li battery cycling. - Signal indicates LiF, LiCl2 - The signal represents LiCl.

[0032] Figure 14 Comparison of Li / CSEs / SS battery CV curves.

[0033] Figure 15 (a) The charge density difference of TGCl, (b) is the charge density difference of DG-Cl; (c)(d)(e)(f) are AIMD simulation snapshots of PEO-DG-Cl.

[0034] Figure 16 (a) is the Li / CSEs / Li battery at 0.1 mA cm -2 (b) is the constant current cycling curve of Li / CSEs / Li battery at 0.2 mA cm -2 Constant current cycle curve under CSE.

[0035] Figure 17 These are the cycling curves of different Li / CSEs / Li batteries at different current densities.

[0036] Figure 18 This is an SEM image of the lithium surface of different Li / CSEs / Li batteries after 200 hours of cycling in an embodiment of the present application.

[0037] Figure 19 Junction voltage-density curves of different Li / CSEs / Li batteries.

[0038] Figure 20 Comparison of EIS curves of different Li / CSEs / Li.

[0039] Figure 21(a) is the nucleation overpotential of the Li / CSEs / Cu battery; (b) is the Tafel curve of the Li / CSEs / Li symmetric battery.

[0040] Figure 22 (a) is the cycling performance of LFP / CSEs / Li battery at a current density of 2C rate; (b) is the cycling curve of LFP / PEO-DG-Cl / Li battery at a current density of 1C rate.

[0041] Figure 23 (a) is the rate performance comparison of LFP / CSEs / Li battery; (b) is the charge and discharge curve of LFP / PEO-DG-Cl / Li battery at different rates; (c) is the charge and discharge curve of LFP / PEO-DG-F / Li battery at different rates.

[0042] Figure 24 This is the cycling performance of LFP / PEO-DG-Cl / Li battery at 30℃ and 0.1C.

[0043] Figure 25 This is the cycling performance of LFP / PEO-DG-Cl / Li battery at 60℃ and 0.2C. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, each embodiment of the present application will be described in detail below with reference to the accompanying drawings. However, it will be understood by those skilled in the art that in each embodiment of the present application, many technical details are proposed to enable the reader to better understand the present application. However, even without these technical details and various changes and modifications based on the following embodiments, the technical solutions claimed in the present application can be implemented. The division of the following embodiments is for convenience of description and should not constitute any limitation on the specific implementation of the present application. The various embodiments can be combined with each other and referenced to each other under the premise of no contradiction.

[0045] Example 1

[0046] like Figure 1 As shown, this embodiment provides a method for preparing a solid electrolyte filler, which is used as a filler for an electrolyte based on polyethylene oxide and lithium bis(trifluoromethanesulfonyl)imide. The specific steps include:

[0047] Ethanol and water are mixed in a volume ratio of 7:1 to prepare an ethanol aqueous solution. Alternatively, an existing ethanol aqueous solution in this volume ratio may be used.

[0048] 5 mmol of 1,3-diaminoguanidine hydrochloride (abbreviated as TG-CL) was measured and added to 64 mL of ethanol aqueous solution, and stirred at room temperature for two hours until dissolved to obtain a first mixed solution.

[0049] 5 mmol of nitrosalicylicylaldehyde (5-ND) was added to the first mixed solution, heated to reflux for 8 hours, and then cooled to obtain a second mixed solution. This step utilizes the Schiff base reaction principle.

[0050] The second mixed liquid is subjected to solid-liquid separation, and the separated solid matter is washed and dried to obtain a powdered first solid electrolyte filler (named DG-Cl); wherein the washing process includes washing with pure water several times to remove unreacted raw materials, then washing with anhydrous ethanol (about -20°C) to remove residual water in the product and reduce product loss; finally, washing with ether to remove residual ethanol in the product and facilitate drying; and after washing, vacuum drying is performed at room temperature.

[0051] Example 2

[0052] 200 mg of the DG-Cl obtained in Example 1 was added to 25 ml of a saturated aqueous sodium fluoride solution and stirred at 60° C. for 72 hours, with the sodium fluoride solution being replaced every 24 hours, to obtain a third mixed solution. The DG-Cl was separated by filtration each time the sodium fluoride solution was replaced to maximize the reaction between the DG-Cl and the saturated aqueous sodium fluoride solution and achieve a more thorough replacement. The weight percentage of sodium fluoride in the saturated aqueous sodium fluoride solution was approximately 4.2 wt %.

[0053] The third mixed liquid is subjected to solid-liquid separation, and the separated solid matter is dried to obtain a powdered second solid electrolyte filler (named DG-F); wherein the drying condition is: drying at 90° C. under vacuum for 12 hours.

[0054] The reaction process of preparing DG-Cl in Example 1 and preparing DG-F in Example 2 is as follows Figure 1 As shown, the first step is the reaction of nitrosalicylicylaldehyde with 1,3-diaminoguanidine hydrochloride to obtain DG-Cl, and the second step is the reaction of DG-Cl with saturated sodium fluoride to obtain DG-F.

[0055] The first solid electrolyte filler (DG-Cl) obtained in Example 1 was subjected to Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) experimental tests, and the test results are as follows:

[0056] like Figure 2 As shown in the FTIR spectrum ( Figure 2 (a)), at the aldehyde group of nitrosalicylaldehyde (5-ND) (1662 cm -1 ) and 1,3-diaminoguanidine hydrochloride (TG-Cl) at 1668 cm -1The condensation at 5-ND (1662 cm) forms a new imine bond (C=N) stretching vibration band. -1 ) and the amino peaks of TG-Cl (2421 and 2128 cm -1 ) further confirmed the formation of the imine bond, thereby confirming the synthesis of DG-Cl.

[0057] In the 13C (carbon 13) NMR spectrum ( Figure 2 (b)), the signal peaks observed at positions 1-5 and 8 are consistent with the carbon signals of the benzene ring in the DG-Cl structure. The signal peak of 156.72ppm belongs to the guanidine group in the DG-Cl structure, while the signal peak of 141.71ppm indicates the C=N bond on the side chain of the benzene ring. After ion exchange (TG-Cl is converted to DG-F), a shift in the 13CNMR spectrum was observed. This change is due to a change in the electronic environment of the carbon atom, which shifts toward the forward field (higher ppm). The results obtained from nuclear magnetic resonance and FTIR spectra are consistent, indicating that the DG-Cl is the first solid electrolyte filler to be synthesized in this application.

[0058] There is no significant difference between DG-Cl and DG- in NMR and FTIR spectra, indicating that the interaction between the organic group and the anion is weak.

[0059] The DG-Cl prepared in Example 1 and the DG-F prepared in Example 2 were examined by scanning electron microscope (SEM). The SEM images and the corresponding energy dispersive spectroscopy (EDS) elemental maps are shown in FIG. Figure 3 The EDS spectrum shows that there is no F element in DG-Cl; the F element is evenly distributed in DG-F, and there is no obvious Cl element.

[0060] Both DG-Cl and DG-F can be used as solid electrolyte fillers. The differences in solid electrolyte and battery performance prepared using the two as fillers will be explained in the subsequent examples and corresponding experiments.

[0061] Example 3, for preparing a variety of solid electrolytes, includes the following specific examples:

[0062] Example 3-1-1

[0063] This embodiment provides a method for preparing a solid electrolyte, comprising: vacuum drying polyethylene oxide (PEO) having a molecular weight of 600,000 and lithium bis(trifluoromethanesulfonylimide) (LiTFSI) at 60° C. for 12 hours; weighing the polyethylene oxide and lithium bis(trifluoromethanesulfonylimide) such that the molar ratio of polyethylene oxide units to lithium ions in the lithium bis(trifluoromethanesulfonylimide) is 10:1;

[0064] Polyethylene oxide, lithium bis(trifluoromethanesulfonyl imide) and TG-Cl (solid electrolyte filler) in Example 1 were mixed; wherein TG-Cl accounted for 1% of the total mass.

[0065] Anhydrous acetonitrile solvent was injected into the mixture, and magnetic stirring was performed for 24 hours to obtain a first slurry; wherein the mass ratio of the acetonitrile solvent to the polyethylene oxide was 15:1.

[0066] The first slurry is cast into a polytetrafluoroethylene mold and tape-cast to obtain an electrolyte membrane with a thickness of 70-200 microns. The electrolyte membrane is left to stand at room temperature to allow the solvent to evaporate. The electrolyte membrane is baked under vacuum to remove residual solvent at a baking temperature of 60°C to obtain a solid electrolyte. For easy testing, the electrolyte membrane is cut into 19mm discs and encapsulated in an inert atmosphere glove box (O2<0.01ppm, H2O<0.01ppm).

[0067] Example 3-1-2: The other steps of this example are the same as those of Example 3-1-1, except that the total mass of TG-Cl is replaced by 2%. Example 3-1-3: The other steps of this example are the same as those of Example 3-1-1, except that the total mass of TG-Cl is replaced by 3%.

[0068] Example 3-2-1: The other steps of this example are the same as those of Example 3-1-1, except that TG-Cl is replaced with DG-Cl prepared in Example 1, which accounts for 1% of the total mass. Example 3-2-2: The other steps of this example are the same as those of Example 3-1-1, except that TG-Cl is replaced with DG-Cl prepared in Example 1, which accounts for 2% of the total mass. Example 3-2-3: The other steps of this example are the same as those of Example 3-1-1, except that TG-Cl is replaced with DG-Cl prepared in Example 1, which accounts for 3% of the total mass.

[0069] Example 3-3-1: The other steps of this example are the same as those of Example 3-1-1, except that TG-Cl is replaced with DG-F prepared in Example 1, which accounts for 1% of the total mass. Example 3-3-2: The other steps of this example are the same as those of Example 3-1-1, except that TG-Cl is replaced with DG-F prepared in Example 1, which accounts for 2% of the total mass. Example 3-3-3: The other steps of this example are the same as those of Example 3-1-1, except that TG-Cl is replaced with DG-F prepared in Example 1, which accounts for 3% of the total mass.

[0070] Example 3-4 (control group): The other steps are the same as Example 3-1-1, and "mixing polyethylene oxide, lithium bistrifluoromethanesulfonyl imide and TG-Cl in Example 1" is replaced by "mixing polyethylene oxide and lithium bistrifluoromethanesulfonyl imide", that is, no filler is added.

[0071] Example 4: SS / CSEs / SS (positive and negative electrodes are stainless steel)

[0072] Two inert stainless steel (SS) electrodes were used as pole pieces, and multiple button cells (abbreviated as SS / CSEs / SS) were assembled with multiple solid electrolytes prepared in Example 3 and tested respectively.

[0073] (1) Ionic conductivity test: The ionic conductivity of composite solid electrolytes (CSEs) with different filler contents (1, 2, and 3 wt%) was determined by AC impedance spectroscopy to determine the most appropriate filler and addition amount. The ionic conductivity of solid electrolytes at different temperatures (30-60°C) was measured on an electrochemical workstation (Shanghai Chenhua, CHI660E). The Arrhenius plots of the ionic conductivity of PEO electrolyte and different solid electrolytes as a function of temperature are shown in Figure 2. Figure 4 As shown; the impedance comparison is Figure 5 As shown in Figure 2, the impedance of different solid electrolytes decreases with increasing temperature, while their ionic conductivity increases accordingly. When the filler content is 1 wt%, the solid electrolyte has the highest ionic conductivity, which is the optimal ratio.

[0074] As can be seen from Table 1 below, the specific ionic conductivity (unit: Scm) of different electrolytes at different temperatures -1 ). At 60℃, the ionic conductivity of 1wt% PEO-DG-Cl reached 3.48×10 -4 Scm -1 , much higher than the 4.68×10 -5 Scm -1 The increase in ionic conductivity is due to the fact that as the temperature rises, PEO changes from a crystalline state to a viscous fluid state, which enhances the movement of the chain segments and accelerates the Li + The Lewis acid sites on the surface of the filler form a strong interaction with the TFSI- anion, weakening the Li + Coulombic binding with anions promotes the dissociation of lithium salts and increases the concentration of free lithium ions. The addition of fillers forces the PEO segments to undergo local rearrangement, increasing the non-crystalline area and the ion transmission path, thereby improving the ionic conductivity. However, due to the strong adsorption of excess fillers on the PEO chains, the movement of the segments is hindered and agglomeration is initiated, blocking the continuous ion transmission path and causing a decrease in ionic conductivity. Therefore, when the filler content is in the range of 1-3wt%, the ionic conductivity of the solid electrolyte decreases with increasing filler content. Moreover, at the same temperature, with 1wt% filler, the ionic conductivity of PEO-DG-Cl is higher than that of PEO-DG-F and PEO-LiTFSI.

[0075] Table 1 Ionic conductivity of cells (SPE) with different fillers and proportions at different temperatures

[0076]

[0077] Subsequent tests were conducted using the electrolyte or battery prepared in the specific embodiment in Example 3, in which the filler accounted for 1 wt %, as the sample.

[0078] (2) Solid electrolyte crystallinity test: X-ray diffraction (XRD) was used to measure the crystallinity of the composite solid electrolyte to verify that the addition of different fillers broke the crystalline region of PEO. Figure 6 As shown in the figure, PEO-LiTFSI has a high degree of crystallinity at room temperature, and its PEO exhibits obvious crystallization peaks at 2θ angles of approximately 19.2° and 23.3°. In comparison, PEO-DG-Cl and PEO-DG-F have no obvious characteristic peaks, and the peak intensity of the PEO-DG-Cl electrolyte is significantly lower than that of PEO-DG-F, indicating that the addition of filler DG-Cl can further reduce the crystallinity of PEO. The characteristic phenomenon of PEO-DG-Cl can be attributed to the strong interaction between the PEO block and the filler, which leads to the phase transition of the PEO matrix block copolymer to form a molecular complex, Cl - Diameter ratio F - The larger the particle size, the easier it is to destroy the pure chain segments of PEO and increase the amorphous region of the polymer.

[0079] (3) Scanning calorimetry (DSC) test: The glass transition temperature (Tg) is the critical temperature at which polymer materials change from a glassy state (rigid, amorphous) to a highly elastic state (flexible, chain segments can move). Its essence reflects the mobility of polymer segments. The test results of the scanning calorimetry (DSC) also verify the test results of the solid electrolyte crystallinity, such as Figure 7 As shown in the figure, the Tg of PEO-DG-Cl is -54.5°C, which is significantly lower than that of PEO-DG-F (-53.2°C), PEO-TG-C (-49.1°C), and PEO-LiTFSI (-47.8°C). The lower the Tg, the worse the crystallinity of the electrolyte, indicating that the low crystallinity of the PEO-DG-Cl electrolyte can promote the transport of lithium ions.

[0080] (4) Characterization test of characteristic vibration region: Fourier transform infrared spectroscopy (FTIR) was used to characterize the 1400-1000 cm -1 The characteristic vibration region is characterized to analyze the dissociation effect of DG molecules in LiTFSI in the composite electrolyte. Figure 8 As shown, in the electrolyte system of PEO and LiTFSI, 1196 cm -1 The double peaks at 1096cm -1The three peaks at 1327.4 and 1295.3 cm correspond to the -CH2- rocking vibration and COC symmetric / asymmetric stretching vibration. The -SO2 symmetric stretching vibration and asymmetric stretching vibration appear at 1327.4 and 1295.3 cm, respectively. -1 After the introduction of fillers, the -SO2 stretching vibration peaks shifted to 1329.7 and 1296.0 cm -1 (PEO-TG-Cl) and 1332.54 cm -1 、1298.4cm -1 (PEO-DG-Cl). It is worth noting that the -CF3 vibration peak is from 1096.4cm -1 (PEO-LiTFSI) shifted significantly to 1098.9 cm -1 (PEO-TG-Cl) and 1102.1 cm -1 (PEO-DG-Cl), the changes of these two peaks are more obvious in PEO-DG-Cl, which indicates that the interaction between DG and TFSI- is stronger and can weaken the Li + and TFSI - The Coulomb attraction between them promotes the dissociation of LiTFSI and releases more Li + .

[0081] (5) Density functional theory (DFT) was used to calculate the electrostatic potential distribution and binding energy of TG and DG molecules. Figure 9 As shown, in Figure 9 The electrostatic potential distribution in (a) shows that compared with the TG molecule, the DG molecule has a higher electrostatic potential energy distribution, and its electrostatic potential is mainly concentrated around the guanidine chain segment of DG, indicating that the charge binding interaction between DG and TFSI- is stronger. Figure 9 (b) Binding energy calculations show that DG and Li + The binding energy of DG reached 0.46eV, which is significantly higher than that of PEO polymer chains (0.19eV) and TG small molecules (0.21eV). This result shows that DG not only effectively fixes LiTFSI molecules through strong coordination, but also weakens the ionic binding of lithium salts due to its unique molecular structure, significantly improving the degree of dissociation of lithium salts.

[0082] (6) Lithium ion migration test: Li + The transference number is a key indicator to measure the efficiency of lithium ion movement and determines the charging rate and energy density of the battery. + The closer the migration number is to 1, the higher the proportion of lithium ions migrating in the solid electrolyte, and the higher the efficiency of the electrolyte in transferring charge between the positive and negative electrodes; on the contrary, when Li + When the migration number is small, a large concentration gradient will be formed inside the battery, forming a reverse electric field, which is not conducive to Li +transmission, resulting in Li + The results of the migration number test are as follows: Figure 10 As shown in Figure 3, PEO-DG-Cl has a higher lithium ion transference number.

[0083] Example 5: Li / CSEs / SS (lithium metal as positive electrode, stainless steel as negative electrode)

[0084] (7) Electrochemical stability window (ESW) and its oxidative decomposition behavior test: This test uses assembled lithium metal as positive electrode and stainless steel as negative electrode (Li / CSEs / SS) as samples, such as Figure 11 As shown in the figure, PEO-LiTFSI shows a significant change in oxidation current at 4.19V, followed by decomposition of the electrolyte. In comparison, PEO-DG-Cl exhibits the best antioxidant stability, with an electrochemical window of around 4.98V, which is higher than the electrochemical window of PEO-DG-F (4.65V). This shows that the LiCl-LiF dual-phase SEI layer can better protect the electrolyte from decomposition and can match the high-voltage positive electrode. The electrochemical window of PEO-TG-Cl is only 3.01V, even lower than that of PEO, indicating that the addition of unmodified small molecules (TG-Cl in PEO-TG-Cl) not only fails to protect the electrolyte from oxidative decomposition, but even undergoes violent side reactions with PEO, causing it to decompose prematurely.

[0085] Example 6: A lithium symmetrical battery is assembled using a lithium electrode and multiple solid electrolytes in Example 3.

[0086] (8) X-ray photoelectron spectroscopy (XPS) was used to analyze the SEI components on the surface of the lithium metal negative electrode in different Li / CSEs / Li / batteries after 200 h of cycling. Figure 12 As shown, during the cycling process, the PEO electrolyte decomposes in contact with the active lithium metal, resulting in surface degradation and uneven deposition of lithium ions. XPS studies show that the decomposition peaks (CC, COC, and C=O) in the C1s spectra of the DG-Cl and DG-F modified PEO electrolytes are significantly reduced, indicating that the decomposition of the electrolyte is successfully alleviated. In addition, we also observed the disappearance of CF3 and a significant increase in CF2 (290.2 eV), which indicates that DG-Cl and DG-F promote the TFSI - The CF bond cleavage in the reaction increases the formation of CF2 radicals, F - With Li + Combined to form LiF. In the solid electrolyte of PEO-DG-Cl, LiTFSI is the only source of fluorine, and in the C1s and F1s spectra, it can be seen that PEO-DG-Cl has more CF2 and LiF than PEO-DG-F. This shows that DG-Cl can catalyze more TFSI -Decomposes to form LiF. This may be due to F - It has stronger electronegativity and is difficult to separate from the macromolecular cation. - There is a certain degree of competitive coordination. Simultaneously, the Cl2p spectrum reveals the formation of lithium chloride in PEO-DG-Cl, enabling the co-growth of LiF / LiCl. These results indicate that the SEI layer enriched with lithium fluoride and lithium chloride has stronger interfacial stability than single-phase lithium fluoride, mitigates additional electrolyte decomposition, promotes uniform lithium ion deposition, and improves battery cycling stability and safety.

[0087] (9) Using lithium symmetric batteries as samples to verify the XPS results, time-of-flight secondary ion mass spectrometry (TOF-SIMS) was used to characterize the contents of LiF and LiCl in the SEI on the surface of the lithium metal anode in different solid electrolytes after 200 h. Figure 13 The SEI components formed on the lithium negative electrode of PEO-DG-Cl and PEO-TG-Cl batteries contain both LiF and LiCl. Moreover, the content of LiF on the lithium negative electrode of PEO-DG-Cl is higher than that of PEO-DG-F and PEO-TG-Cl batteries, which is consistent with the detection results of XPS.

[0088] (10) Using Li / CSEs / SS battery as a sample, verify the effect of DG-Cl on TFSI - The regulation of anion decomposition was investigated by cyclic voltammetry (CV, scan rate 0.1 mV / s, voltage window 0.01-2.5 V vs. Li+ / Li) to analyze the redox behavior of Li / CSEs / SS batteries. Figure 14 As shown, strong reduction peaks appear in the 1.2-1.5V range, corresponding to TFSI - The decomposition peak of PEO-LiTFSI electrolyte gradually disappears after the first cycle, indicating that most of the TFSI - In the PEO-DG-F electrolyte, the peak gradually disappears after the second cycle, indicating that most of the TFSI- has been completely decomposed. By comparing the CV curves of different electrolytes, it can be found that the TFSI in PEO-DG-Cl - The reduction was the most intense and persisted throughout the cycle, which indicated that DG-Cl and TFSI - The strongest force can make more TFSI - The above results are also verified by the experimental results of XPS.

[0089] (11) Charge transfer process detection: Using lithium symmetric battery as a sample, the charge density difference method was used to detect the charge transfer process to analyze the effect of DG-Cl on TFSI.- The test results are as follows: Figure 15 As shown, when TFSI - When in contact with DG-Cl and TG-Cl, TFSI - Pairing with the polar functional group - amino group on TG-Cl, thereby transferring charge to TFSI - The charge transfer number of TG-Cl is only 0.10584e - In contrast, the charge transfer number of the optimized DG-Cl is about 17 times that of TG-Cl (l1.8453e). This is because the intermolecular π-π interaction of the optimized DG-Cl molecules forms a dense electron cloud, which allows the charge to be transferred to the TFSI. - Furthermore, each process of LiTFSI decomposition was monitored by AIMD simulation time. - The decomposition process of Figure 15 As shown, after 280 fs, the CS and NS bonds in LiTFSI are broken to form CF3 - 、SO2 - and LiNSO2CF3 - .also, Figure 15 It shows that the Cl of DG-Cl - Falling off from the center, and then with Li + Combined to form LiCl. After 520fs, the 1.1263e of DG-Cl - Injected anions, LiNSO2CF3 - Decomposes into CF3- and LiNSO2 - At 760fs, these CF3 - Further decomposed into CF2 - and F - , and finally with Li + Combined to form LiF.

[0090] (12) Test of lithium deposition and release behavior of solid electrolytes: Lithium symmetric batteries were used as samples, and Li / PEO-DG-Cl / Li was used to represent batteries with PEO-DG-Cl as the electrolyte; Li / PEO-DG-F / Li was used to represent batteries with PEO-DG-F as the electrolyte; and Li / PEO-LiTFSI / Li was used to represent batteries with PEO-LiTFSI as the electrolyte.

[0091] At 60°C 0.1 mA cm -2 and 0.2 mA cm -2 Long cycle test is performed under Figure 16 As shown. The current density is 0.1mAcm -2When the PEO-LiTFSI assembled battery showed a high initial overpotential during the plating / stripping process, and short-circuited after only 300 h of cycling due to the growth of lithium dendrites. However, both PEO-DG-Cl and PEO-DG-F were able to cycle stably with a small polarization voltage and had a cycle life of more than 2400 h and 4000 h, respectively, without any obvious short-circuit events. Increasing the current density to 0.2 mA cm -2 , PEO-DG-F can also cycle for 1000 hours before being pierced by lithium dendrites and then short-circuited, while the PEO-DG-Cl battery can cycle stably for more than 2200 hours.

[0092] (13) Measure the polarization voltage of the battery at different current densities: Using lithium symmetrical batteries as samples, the current density used in the test ranges from 0.05 to 0.5 mA cm -2 The test results are as follows Figure 17 As shown in Figure 2, the polarization voltage increases steadily with the increase of current density. The Li / PEO-DG-Cl / Li battery can maintain the lowest voltage platform for stable cycling during the entire plating / stripping process, which is much smaller than that of the Li / PEO-LiTFSI / Li battery. When the current returns to 0.05 mA cm -2 and 0.1 mA cm -2 After high current cycling, the polarization voltage of Li / PEO-DG-Cl / Li showed no significant change compared with that before high current cycling, while that of Li / PEO-DG-F / Li and Li / PEO-LiTFSI / Li showed a significant change. The above results indicate that PEO-DG-Cl electrolyte has good compatibility with lithium metal anode and can maintain long-term stable cycling.

[0093] (14) Detection of lithium deposition morphology of lithium symmetric batteries after 200 h of static cycling: The lithium deposition morphology of symmetric lithium batteries with different solid electrolytes after 200 h of static cycling was observed using a scanning electron microscope (SEM). Figure 18 As shown, the lithium anode surface in Li / PEO-LiTFSI / Li exhibits a typical porous, mossy structure, accompanied by vertically growing fractal dendrites and flaky accumulation of "dead lithium." The deactivation of a large amount of active lithium leads to battery capacity decay. In Li / PEO-DG-F / Li, the lithium metal surface is uneven, and the spherical dendrites are significantly reduced but still exist and are accompanied by cracks. This may be because although LiF can improve the mechanical strength of the SEI, the high grain boundary impedance of LiF leads to an imbalance in the local lithium ion flux. After cycling, the lithium sheet surface of Li / PEO-DG-Cl / Li is smooth and free of obvious dendrites or dead lithium, indicating good compatibility between metallic lithium and PEO-DG-Cl. The resulting LiCl-LiF dual-phase SEI layer effectively suppresses the formation of lithium dendrites and enables uniform lithium deposition.

[0094] (15) Critical current density test: Critical current density (CCD) is the highest current density that a symmetrical lithium battery can withstand before failure (short circuit or sharp rise in overpotential) occurs. Under 60°C, the voltage-time curves of symmetrical batteries with different electrolytes at different current densities are monitored. The test results are as follows: Figure 19 As shown in Figure 2, with the increase of current density, the critical current density of Li / PEO-DG-Cl / Li battery is as high as 1.23 mA cm -2 The critical current density of the Li / PEO-DG-F / Li battery is 0.93 mA cm -2 ; Li / PEO-LiTFSI / Li at 0.5 mA cm -2 The significant increase in the critical current density when short-circuited indicates that PEO-DG-Cl can withstand a larger current density and has good dendrite inhibition and high interface stability.

[0095] (16) Electrochemical impedance spectroscopy (EIS) measurements were performed to evaluate the interfacial stability between CSE and Li metal at different cycle intervals (0 to 50 cycles). At a constant current density, the interfacial impedance changed dynamically with time, initially increasing gradually, which was due to the instability of the SEI formed in the early stages of battery cycling. Figure 20 As shown in the figure, the initial interfacial impedance between PEO-DG-CL and metallic lithium (477Ω) is much lower than the initial interfacial impedance between PEO-LiTFSI / Li and lithium (1873Ω) and the initial interfacial impedance between PEO-DG-F and lithium (558Ω). The interfacial impedance between PEO-DG-CL and lithium metal increases slightly over time and stabilizes at around 563Ω after 40 hours, indicating that the SEI generated by PEO-DG-CL is relatively stable. In contrast, the interfacial resistance between PEO-DG-F and lithium metal remains unstable after 40 hours and increases to 1005Ω after 50 hours. Although the interfacial impedance of PEO-LiTFSI decreases after 50 hours, it remains at 1553Ω. This result shows that the CSE based on PEO-DG-CL has good compatibility with the lithium metal anode interface.

[0096] Example 7: Using lithium symmetric batteries and lithium copper batteries as samples

[0097] Using multiple solid electrolytes from Example 3, a symmetric Li / Li battery with lithium at both electrodes (referred to as Li / CSEs / Li) and a Li / Cu battery with lithium and copper electrodes (referred to as Li / CSEs / Cu) were assembled.

[0098] (17) Detect the exchange current density of Li / CSEs / Li) battery. The test results are as follows Figure 21As shown in (a), the exchange current of PEO-DG-Cl is 0.0782 mA cm -2 , is PEO-DG-F (0.0335mAcm -2 ) is more than twice that of PEO-LiTFSI (0.0157mAcm -2 ) by 5 times, and the higher exchange current density indicates that DG-CL promotes the charge transfer process at the lithium / polymer electrolyte interface. + The transport kinetics are faster. Detection of the nucleation overpotential of Li / CSEs / Cu batteries: The nucleation overpotential is a key parameter for evaluating the lithium affinity of electrodes, reflecting the nucleation barrier of lithium atoms on heterogeneous substrates. A higher nucleation overpotential indicates a tendency for non-uniform lithium deposition. Figure 21 As shown in (b), the measured nucleation overpotentials of PEO-LiTFSI, PEO-DG-CL and PEO-DG-F in the initial stage of lithium deposition are 34 mV, 16.5 mV and 29.2 mV, respectively. The lithium nucleation barrier of PEO-DG-CL is the lowest, indicating that the hopping energy barrier that PEO-DG-CL needs to overcome in lithium deposition is the smallest. + The above shows that the SEI layer interface rich in LiF-LiCl can accelerate the deposition of Li + The transmission speed is improved, promoting the uniform deposition of lithium ions.

[0099] Example 7: The solid electrolytes prepared in various specific examples of Example 3 were separately prepared into multiple batteries to test the performance of the solid electrolytes and batteries. The battery positive electrode preparation process is as follows: LiFePO4 (LFP), polyvinylidene fluoride (PVDF), and conductive carbon black were mixed and stirred in N-methylpyrrolidone at a mass ratio of 8:1:1 for 8 hours, then coated on aluminum foil, vacuum dried at 100°C for 24 hours, and then placed in a glove box for later use.

[0100] Batteries were prepared using the above-mentioned mixed material as the positive electrode and lithium metal as the negative electrode. In this example, they are referred to as LFP / CSEs / Li batteries, where CSEs represents a solid electrolyte. The batteries were assembled and tested at 60°C. The batteries included: LFP / PEO-TGCl / Li, LFP / PEO-DG-Cl / Li, LFP / PEO-DG-F / Li, and LFP / PEO-LiTFSI / Li.

[0101] (18) Long cycle test current density: A long cycle test was conducted at 60°C. Figure 22 (a) Shows the cycling performance of multiple batteries at a current density of 2C with lithium anode. Figure 22 (b) shows that at a current density of 1C, the initial capacity of the LFP / PEO-DG-Cl / Li battery is 132.9 mAh g-1 After 750 charge and discharge cycles, the reversible capacity of the battery is 107.5 mAh g -1 , the capacity retention rate is 80.8%. When the cycle current density is increased to 2C, the Figure 22 As shown in (a), the initial capacity of the LFP / PEO-DG-Cl / Li battery is 123.7 mAh g -1 After 800 charge and discharge cycles, the discharge capacity of the LFP / PEO-DG-Cl / Li battery reached 99.8 mAh g -1 , the capacity is retained at 80.6%. In contrast, the initial discharge capacity of the LFP / PEO-DG-F / Li battery reaches 120.9mAh -1 , the reversible capacity after 800 charge and discharge cycles is 70.6 mAh g -1 The charge and discharge capacity of the LFP / PEO-LiTFSI / Li and LFP / PEO-TGCl / Li batteries were lower than those of the LFP / PEO-DG-Cl / Li and LFP / PEO-LiTFSI / Li throughout the entire cycle. The LFP / PEO-LiTFSI / Li failed after approximately 250 cycles, while the charge and discharge capacity of the LFP / PEO-TGCl / Li battery was even lower than that of the LFP / PEO-LiTFSI / Li, failing after more than 100 cycles due to severe side reactions.

[0102] (19) Rate performance testing: Excellent rate response capability can indicate that the electrode interface has fast charge transfer kinetics and can adapt to different currents for rapid charging and discharging. Here, LFP / PEO-DG-Cl / Li, LFP / PEO-DG-F / Li, and LFP / PEO-LiTFSI / Li batteries were measured at constant currents at different rates from 0.1C to 2C to evaluate the rate performance of solid-state electrolytes (CSEs). Figure 23 (a) shows that the initial discharge capacities of the three batteries at 0.1C are not much different; among them, LFP / PEO-DG-Cl / Li and LFP / PEO-LiTFSI / Li are 159.3 mAh g -1 , LFP / PEO-DG-F / Li is 154 mAh g-1. Subsequently, the charge rate continues to increase, and the rate performance difference of the three solid electrolytes gradually becomes larger. The discharge specific capacities of LFP / PEO-DG-Cl / Li battery at 0.2C, 0.5C, 1C and 2C are 154.69, 146.16, 136.01 and 120.44 mAh g-1, respectively. -1 , when it returns to 0.1C from high current, it still has 154.54mAhg -1The capacity retention rate is 97%. The discharge specific capacities of LFP / PEO-DG-F / Li battery at 0.2C, 0.5C, 1C and 2C are 146.30, 138, 129.8 and 112.7 mAh g respectively. -1 When the current returns to 0.1C, the reversible discharge capacity is 144.8 mAh g -1 , the capacity retention rate is 94%. Figure 23 (b) and (c) show the voltage curves of LFP / PEO-DG-Cl / Li and LFP / PEO-DG-F / Li batteries at different charge and discharge rates. LFP / PEO-DG-Cl / Li always maintains a low polarization and a stable charge and discharge platform, indicating that the rate performance of LFP / PEO-DG-Cl / Li battery is more stable. The above test results show that the PEO-DG-Cl electrolyte has excellent rate cycling performance. It can not only adapt to different current rates for stable cycling, but also can ensure effective discharge specific capacity at high currents. This shows that the SEI layer of the dual-phase LiF-LiCl can effectively inhibit the growth of lithium dendrites and ensure the long cycle life of the battery.

[0103] (20) Crystallinity test: The PEO electrolyte alone has high crystallinity and low ionic conductivity at room temperature, so its performance at room temperature is not ideal. Here, the cycling performance of the LFP / PEO-DG-Cl / Li battery was tested at 30°C. Figure 24 As shown, the initial discharge capacity at a current of 0.1C reaches 127.7mAhg -1 After 250 cycles, the discharge capacity did not decrease significantly. When LFP was increased to 6.12 mg, the initial capacity of LFP / PEO-DG-Cl / Li at 60 ° C and 0.2 C was 136.2 mAh g -1 After more than 50 stable cycles, the remaining specific capacity is still 122.7 mAh g -1 ( Figure 25 ).

[0104] It should be understood that the above-mentioned specific embodiments of the present application are merely illustrative or explain the principles of the present application and do not constitute a limitation of the present application. Therefore, any modifications, equivalent substitutions, improvements, etc. made without departing from the spirit and scope of the present application should be included in the scope of protection of the present application. In addition, the claims attached hereto are intended to cover all variations and modifications that fall within the scope and boundaries of the appended claims, or the equivalent forms of such scope and boundaries.

Claims

1. A method for preparing a solid electrolyte filler, wherein the solid electrolyte filler is used as a filler for preparing an electrolyte based on polyethylene oxide and lithium bis(trifluoromethanesulfonyl)imide, characterized in that: include: Mixing ethanol and water to obtain an ethanol-water solution; adding 1,3-diaminoguanidine hydrochloride to the ethanol aqueous solution to dissolve it to obtain a first mixed solution; adding nitrosalicylicylaldehyde to the first mixed solution, heating to reflux for a first preset time to obtain a second mixed solution, wherein the molar ratio of the 1,3-diaminoguanidine hydrochloride to the nitrosalicylicylaldehyde is 1:2; The second mixed liquid is subjected to solid-liquid separation, and the separated solid matter is washed and dried to obtain a first solid electrolyte filler.

2. The method for preparing a solid electrolyte filler according to claim 1, wherein: The volume ratio of ethanol to water in the ethanol aqueous solution is 7:1; The molar concentration of 1,3-diaminoguanidine hydrochloride in the first mixed solution is 0.078 mol / L.

3. The method for preparing a solid electrolyte filler according to claim 2, wherein: The reaction conditions for adding 1,3-diaminoguanidine hydrochloride to the ethanol aqueous solution to dissolve it are: stirring at room temperature for 2 hours until it dissolves.

4. The method for preparing a solid electrolyte filler according to claim 1, wherein: The solid-liquid separation of the second mixed liquid and washing and drying the separated solid matter comprises: washing the solid matter with pure water, anhydrous ethanol and ether in sequence, and then drying in vacuum.

5. The method for preparing a solid electrolyte filler according to claim 1, wherein: adding the first solid electrolyte filler to a saturated sodium fluoride aqueous solution and stirring to obtain a third mixed solution, wherein the mass volume ratio of the first solid electrolyte filler to the saturated sodium fluoride aqueous solution is 8 g / ml; The third mixed liquid is subjected to solid-liquid separation, and the separated solid matter is dried to obtain a powdered second solid electrolyte filler.

6. The method for preparing a solid electrolyte filler according to claim 5, characterized in that: The step of adding the first solid electrolyte filler to a saturated sodium fluoride aqueous solution and stirring the solution comprises: stirring the solution at 60° C. for 72 hours; wherein the sodium fluoride solution is replaced every 24 hours; The solid matter after separation was dried under vacuum at 90°C for 12 hours.

7. A method for preparing a solid electrolyte, characterized in that: include: Polyethylene oxide with a molecular weight of 600,000 and lithium bis(trifluoromethanesulfonyl)imide were vacuum dried at 60°C for 12 hours. Weighing polyethylene oxide and lithium bis(trifluoromethanesulfonyl)imide, wherein the molar ratio of the polyethylene oxide unit to the lithium ion in the lithium bis(trifluoromethanesulfonyl)imide is 10:1; Mixing polyethylene oxide, lithium bis(trifluoromethanesulfonylimide) and the first solid electrolyte filler according to any one of claims 1 to 6; wherein the first solid electrolyte filler accounts for 1 to 3% of the total mass; injecting anhydrous acetonitrile solvent into the mixture and stirring to obtain a first slurry; forming the first slurry in a mold to obtain an electrolyte membrane; leaving the electrolyte membrane at room temperature to allow the solvent to evaporate; The electrolyte membrane is baked under vacuum to remove residual solvent at a baking temperature of 60° C., thereby obtaining a solid electrolyte.

8. A solid electrolyte, characterized in that Made by the preparation method of the solid electrolyte according to claim 7. 9 . A solid-state battery comprising a positive electrode sheet, a negative electrode sheet, and the solid electrolyte according to claim 8 disposed between the positive electrode sheet and the negative electrode sheet.

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