A polyurea, polythiourea superionic solid electrolyte and a preparation method and application thereof

Abstract

The application relates to the field of polymer solid-state batteries, and discloses a polyurea and polythiourea super-ionic solid-state electrolyte as well as a preparation method and application thereof. The super-ionic solid-state electrolyte comprises a polymer matrix and a metal lithium salt, and the polymer matrix is one of a main-chain type polythiourea, a side-chain type polythiourea or polyurea. The application introduces a thiourea group or a urea group on a polymer main chain or a side chain, forms a strong super-molecular interaction with a lithium salt anion, promotes the dissolution of the lithium salt in the polymer matrix, and introduces a novel transmission mechanism, so that a super-ionic solid-state electrolyte with a high transference number and a high ionic conductivity is obtained.

Description

Technical Field

[0001] This invention belongs to the field of polymer solid electrolyte materials, specifically relating to a polyurea and polythiourea superionic solid electrolyte, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries have been widely used in daily life due to their high energy density, high power, long lifespan, and excellent electrochemical performance. However, commercially available lithium-ion batteries have drawbacks in practical applications, including safety hazards such as leakage and flammability, and irreversible capacity decay caused by side reactions with electrode materials. Meanwhile, next-generation energy storage systems require even higher energy density and safety. Therefore, lithium metal anode solid-state batteries have sparked a global research boom in recent years.

[0003] To realize lithium metal anode solid-state batteries, there is an urgent need to develop solid-state electrolytes with high ionic conductivity, high mechanical strength, good interfacial compatibility, good processability, and chemical / electrochemical stability. Inorganic / ceramic solid-state electrolytes possess high mechanical strength, high room-temperature ionic conductivity, and a wide chemical window, but their poor chemical and electrochemical stability, poor processability, and relatively high solid / solid interface impedance limit their further applications. Another option is polymer solid-state electrolytes, which are easy to process and flexible. Currently, polymer solid-state electrolytes are mainly based on polyethylene oxide (PEO) materials. Due to the strong coupling between ion diffusion and polymer chain segment movement, their room-temperature ionic conductivity is low (10⁻⁶). -5 ~10 -6 S·cm -2 The low ion mobility (0.1–0.2) and weak mechanical strength of polymer solid-state electrolytes severely limit their application. To improve the performance of polymer solid-state electrolytes, various strategies have been proposed, including the introduction of nanofillers (S. Jayanthi and B. Sundaresan, Ionics, 2015, 21, 705-717), single-ion conductive polymers (W. Zhang, Chem. Mater. 2021, 33, 524-534), and block copolymers (M. Jia, Adv. Funct. Mater. 2021, 31, 2101736). However, none of these methods are sufficient to meet the practical application requirements of batteries.

[0004] To overcome the inherent contradiction between ionic conductivity, lithium-ion transference number, and mechanical strength in polymer electrolytes, the development of polymer solid electrolyte materials with novel transport mechanisms is urgently needed. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention aims to provide a polyurea / polythiourea superionic solid electrolyte, its preparation method, and its applications. This solid electrolyte exhibits high mechanical strength, high room-temperature ionic conductivity, and high ionic conductivity.

[0006] The specific technical solution of this invention is as follows:

[0007] A polyurea / polythiourea superionic solid electrolyte comprising a polymer matrix and a lithium metal salt.

[0008] The present invention introduces thiourea groups or urea groups onto the polymer backbone or side chains, offering the following advantages: 1) Thiourea groups or urea groups form a tight bond with lithium ions and anions through synergistic electrostatic and hydrogen bonding interactions, promoting the dissolution of lithium salts in the polymer matrix; 2) High-density thiourea groups or urea groups anchored along the polythiourea chain or polyurea chain act as polar sites to bind lithium ions, constructing ion conduction channels and assisting lithium ion movement in a manner decoupled from polymer chain segment movement. Through the introduction of this novel transport mechanism and the optimization of polymer materials, the superionic solid electrolyte of the present invention exhibits high transfer number, high ionic conductivity, and excellent mechanical strength.

[0009] The polymer matrix of this invention is one of main-chain polythiourea, side-chain polythiourea, or polyurea. The structure of the main-chain polythiourea is shown in Formula 1, and the structure of the side-chain polythiourea or polyurea is shown in Formula 2.

[0010]

[0011] R1 and R2 are One or two of them;

[0012] R3 is a urea group or a thiourea group;

[0013] R4 is One of them.

[0014] This invention provides a method for preparing polyurea and polythiourea superionic solid electrolytes, comprising the following steps: dissolving the polymer matrix and lithium salt separately and mixing them evenly, pouring the mixture into a polytetrafluoroethylene plate, and drying it to obtain the superionic solid electrolyte.

[0015] The lithium salt described in this invention is one of lithium perchlorate, lithium bis(trifluoromethanesulfonyl)imide, lithium tetrafluoroborate, and lithium bis(difluorosulfonyl)imide, and the lithium salt accounts for 1% to 50% of the total mass of the solid electrolyte.

[0016] When a polymer matrix is ​​selected as a main-chain polythiourea, a main-chain polythiourea superionic solid electrolyte is prepared. The preparation method of the main-chain polythiourea polymer matrix includes the following steps:

[0017] S1: In an inert gas atmosphere, sulfur, aliphatic diamine and diisocyanate are mixed and dissolved in N,N-dimethylformamide in a certain mass ratio;

[0018] S2: Stir the mixture obtained in step S1 at 40-50°C for 4-5 hours and then cool it to room temperature. Drip the reaction mixture into a hexane / dichloromethane mixed solvent through a cotton filter. Wash the resulting precipitate three times with methanol and then dry it to obtain a main-chain polythiourea.

[0019] Preferably, in step S1, the aliphatic diamine is one of 1,6-diaminohexane and 1,8-diamino-3,6-dioxane.

[0020] Preferably, in step S1, the diisocyanate is one of 1,6-diisocyanohexane and 1,2-bis(2-isocyanoethoxy)ethane.

[0021] When the polymer matrix is ​​selected as a side-chain polythiourea or polyurea, a side-chain polythiourea or polyurea superionic solid electrolyte is prepared. The preparation method of the side-chain polythiourea or polyurea polymer matrix includes the following steps:

[0022] T1: Under an inert gas atmosphere and at 0°C, aliphatic amines or aromatic amines and isocyanates or thioisocyanates are dissolved in tetrahydrofuran in a certain mass ratio and then mixed; the resulting mixture is reacted at 0-5°C for 4-5 hours, and then reacted at room temperature for 12-14 hours; the solution is evaporated to dryness to obtain the product containing urea or thiourea acrylate monomers.

[0023] T2: In an inert gas atmosphere, the monomer obtained in step T1 is dissolved in N,N-dimethylformamide, and 0.5659 mg of azobisisobutyronitrile per gram of monomer is added and mixed evenly; the resulting mixture is stirred and reacted at 60-70°C for 24-25 h; the reaction mixture is precipitated and centrifuged using a water / methanol mixed solvent (water to methanol volume ratio of 1:4); the precipitate is dried under vacuum to obtain side-chain polythiourea or polyurea polymer.

[0024] Preferably, in step T1, the aliphatic amine is n-butylamine, and the aromatic amine is one of aniline, 4-n-butylaniline, p-trifluoromethylaniline, m-di(trifluoromethyl)aniline, and 2,3,4,5,6-pentafluoroaniline;

[0025] Preferably, in step T1, the isocyanate is ethyl 2-isocyanate acrylate and the thioisocyanate is methyl 2-isothiocyanoacetate.

[0026] This invention also provides the application of the above-mentioned polythiourea and polyurea superionic solid electrolyte in the preparation of secondary batteries.

[0027] Compared with the prior art, the present invention has the following advantages and beneficial technical effects:

[0028] This invention introduces a novel transmission mechanism (see appendix) Figure 1 By introducing thiourea or urea groups onto the polymer backbone and side chains, strong supramolecular interactions are formed between the thiourea groups and lithium anions, promoting the dissolution of lithium salts in the polymer matrix. High-density thiourea or urea groups anchored along the polymer chain and lithium anions act as polar sites to bind lithium ions, constructing ion conduction channels and assisting lithium ion movement in a manner decoupled from polymer chain segment movement, thereby obtaining a superionic solid electrolyte with high transfer number and high ionic conductivity. Furthermore, the introduction of different electron-withdrawing groups or conjugated groups on polythiourea or polyurea side chains adjusts the binding constant between urea / thiourea groups and lithium salt anions, thereby optimizing the solubility of lithium salts and the ionic conductivity of the electrolyte.

[0029] Compared with the prior art, the present invention has the following advantages and beneficial technical effects:

[0030] (1) The polythiourea and polyurea superionic solid electrolytes prepared in this invention have high transfer numbers (>0.8) and high room temperature ionic conductivity (>1*10). -4 (s / cm, at 25℃).

[0031] (2) The polythiourea and polyurea superionic solid electrolytes prepared by this invention have high mechanical strength (>200MPa), thermal and (electro)chemical stability, and effectively suppress dendrite growth and side reactions on metal electrodes in ion batteries.

[0032] (3) The polymer solid electrolyte of the present invention is conducive to large-scale continuous production and equipment, and avoids the safety hazards of liquid electrolytes being flammable and prone to leakage. Attached Figure Description

[0033] Figure 1 The molecular interactions in the solid electrolyte of this invention and Li + A diagram illustrating hop transmission;

[0034] Figure 2 It is the polymer matrix PTU1 in Example 1 of this invention. 1 H NMR spectrum;

[0035] Figure 3 It is the polymer matrix PTU1 in Example 1 of this invention. 13 C NMR spectrum;

[0036] Figure 4 It is the polymer matrix PTU2 in Example 5 of this invention. 1 H NMR spectrum;

[0037] Figure 5 It is the polymer matrix PTU2 in Example 5 of this invention. 13 C NMR spectrum;

[0038] Figure 6 It is the polymer matrix PTU3 in Example 6 of this invention. 1 H NMR spectrum;

[0039] Figure 7 It is the polymer matrix PTU3 in Example 6 of this invention. 13 C NMR spectrum;

[0040] Figure 8 These are DSC diagrams of the polymer matrix in Examples 1, 5, and 6 of this invention;

[0041] Figure 9 These are DSC diagrams of the solid electrolytes obtained in Examples 1, 5, and 6 of this invention;

[0042] Figure 10 These are the XRD patterns of the solid electrolytes obtained in Examples 1, 5, 6 and the comparative examples of this invention;

[0043] Figure 11 These are the Fourier transform infrared spectra of the solid electrolytes obtained in Example 1 and the comparative example of this invention;

[0044] Figure 12 These are the ionic conductivity of the solid electrolytes obtained in Examples 1-4 of this invention at different temperatures;

[0045] Figure 13 These are the ionic conductivity of the solid electrolytes obtained in Examples 1, 5, 6 and the comparative examples of the present invention at different temperatures;

[0046] Figure 14 The ionic conductivity of the solid electrolytes obtained in Examples 7-9 and the comparative examples of this invention at room temperature;

[0047] Figure 15 The solid electrolytes Li obtained in Examples 1, 5, 6 and the comparative examples of this invention are Li + Number of migrations;

[0048] Figure 16 These are the LSV curves of the solid electrolytes obtained in Examples 1, 5, and 6 of this invention;

[0049] Figure 17 The solid electrolyte Li / electrolyte / Li symmetric battery obtained in Examples 1 and 5 of this invention has a performance of 0.1 mAh·cm⁻¹. -2 Cyclic stability at current density;

[0050] Figure 18These are the charge-discharge curves of the solid electrolyte Li / electrolyte / LFP full cells obtained in Examples 1 and 5 of this invention;

[0051] Figure 19 The cycling performance of the Li / PSE1 / LFP full cell with solid electrolyte obtained in Example 1 of this invention is shown.

[0052] Figure 20 This describes the cycle performance of the Li / PSE1 / NCM full cell with solid electrolyte obtained in Example 1 of this invention. Detailed Implementation

[0053] The present invention will be further described in detail below through specific embodiments. The following embodiments are only used to illustrate the present invention, but are not intended to limit the scope of implementation of the present invention. All technical solutions obtained by equivalent substitution or equivalent transformation fall within the protection scope of the present invention.

[0054] Examples 1-4

[0055] Preparation of a main-chain polythiourea superionic solid electrolyte

[0056] (1) Under nitrogen atmosphere, cyclooctasulfide S8 (12.0 mmol, 0.3837 g), 1,6-diisocyanohexane (4.0 mmol, 0.5444 g), and 1,6-diaminohexane (4.0 mmol, 0.4645 g) were added to a 25 mL Schlenk tube equipped with a magnetic stir bar, and then 8.0 mL of N,N-dimethylformamide was injected.

[0057] (2) After stirring at 40°C for 4 hours, the reaction mixture was cooled to room temperature and 300 mL of a mixed solvent of n-hexane / dichloromethane (v / v, 2 / 1) was added dropwise through a cotton filter. The precipitate was washed three times with methanol and then dried to give a yellow solid product, polythiourea matrix PTU1, in 88% yield. n =25700g / mol, M w =48100g / mol, M w / M n =1.87.

[0058] PTU1 polythiourea matrix 1 H NMR spectrum as shown Figure 2 As shown, 13 The C NMR spectrum is as follows Figure 3 As shown, the NMR data are as follows:

[0059] 1 H NMR (500MHz, DMSO-d6), δ (TMS, ppm): 7.29, 3.33, 1.45, 1.26.

[0060] 13 C NMR (125MHz, DMSO-d6), δ (TMS, ppm): 182.34, 43.86, 29.22, 26.63.

[0061] The product structure was determined to be as follows:

[0062] (3) The polymer matrix PTU1 and the lithium salt (lithium perchlorate) are dissolved separately and then mixed evenly to achieve a LiClO4 doping ratio (r = [Li + The mixture of [C=S] and [C=S] is 1, poured into a polytetrafluoroethylene plate, dried, and the superionic solid electrolyte PSE1 of Example 1 is obtained.

[0063] The same operation as above was performed, with LiClO4 doping ratios of 2, 0.5 and 0.2, and the mixture was dried to obtain the superionic solid electrolytes of Examples 2, 3 and 4, respectively.

[0064] Example 5

[0065] Preparation of a main-chain polythiourea superionic solid electrolyte

[0066] (1) Under nitrogen atmosphere, S8 (12.0 mmol, 0.3837 g), 1,6-diisocyanohexane (4.0 mmol, 0.5444 g), and 1,8-diamino-3,6-dioxaoctane (4.0 mmol, 0.5925 g) were added to a 25 mL Schlenk tube equipped with a magnetic stir bar, and then 8.0 mL of N,N-dimethylformamide was injected.

[0067] (2) After stirring at 45°C for 5 hours, the reaction mixture was cooled to room temperature and 300 mL of a mixed solvent of n-hexane / dichloromethane (v / v, 2 / 1) was added dropwise through a cotton filter. The precipitate was washed three times with methanol and then dried. A yellow solid product, polythiourea matrix PTU2, was obtained in 82% yield. n =23600g / mol, M w =42200g / mol, M w / M n =1.79.

[0068] PTU2 polythiourea matrix 1 H NMR spectrum as shown Figure 4 As shown, 13 The C NMR spectrum is as follows Figure 5 As shown, the NMR data are as follows:

[0069] 1H NMR (500MHz, DMSO-d6), δ (TMS, ppm): 7.47, 7.31, 3.53, 3.49, 3.48, 1.45, 1.26.

[0070] 13C NMR (125MHz, DMSO-d6), δ (TMS, ppm): 182.67, 69.60, 69.04, 43.36, 28.74, 26.20.

[0071] The product structure was determined to be as follows:

[0072] (3) After dissolving the polymer matrix PTU2 and the lithium salt (lithium perchlorate) separately, they are mixed evenly to make the molar ratio of thiourea group to lithium perchlorate 1:1. The mixture is poured into a polytetrafluoroethylene plate and dried to obtain the superionic solid electrolyte PSE2.

[0073] Example 6

[0074] Preparation of a main-chain polythiourea superionic solid electrolyte

[0075] (1) Under nitrogen atmosphere, S8 (12.0 mmol, 0.3837 g) and 1,2-bis(2-isocyanoethoxy)ethane (4.0 mmol, 0.6724 g) and 1,8-diamino-3,6-dioxooctane (4.0 mmol, 0.5925 g) were added to a 25 mL Schlenk tube equipped with a magnetic stir bar, and then 8.0 mL of N,N-dimethylformamide was injected.

[0076] (2) After stirring at 50°C for 4 hours, the reaction mixture was cooled to room temperature and 300 mL of a mixed solvent of n-hexane / dichloromethane (v / v, 2 / 1) was added dropwise through a cotton filter. The precipitate was washed three times with methanol and then dried. A yellow, viscous liquid product, polythiourea matrix PTU3, was obtained in 91% yield. n =8900g / mol, M w =14900g / mol, M w / M n =1.67.

[0077] PTU3 polythiourea matrix 1 H NMR spectrum as shown Figure 6 As shown, 13 The C NMR spectrum is as follows Figure 7 As shown, the NMR data are as follows:

[0078] 1 H NMR (500MHz, DMSO-d6), δ (TMS, ppm): 7.52, 3.53, 3.49.

[0079] 13 C NMR (125MHz, DMSO-d6), δ (TMS, ppm): 182.55, 69.59, 69.01, 43.51.

[0080] The product structure was determined to be as follows:

[0081] (3) After dissolving the polymer matrix PTU3 and lithium perchlorate separately, they are mixed evenly to make the molar ratio of thiourea group to lithium perchlorate 1:1. The mixture is poured into a polytetrafluoroethylene plate and dried to obtain superionic solid electrolyte PSE3.

[0082] Example 7

[0083] Preparation of a side-chain type polyurea superionic solid electrolyte

[0084] (1) Under an inert gas atmosphere and at 0°C, 4-n-butylaniline (34.0 mmol, 5.14 g) and ethyl 2-isocyanate acrylate (34.0 mmol, 4.86 g) were dissolved in tetrahydrofuran and mixed. The resulting mixture was reacted at 1°C for 5 hours, and then at room temperature for 13 hours. The solution was evaporated to dryness to obtain the product, an acrylate monomer containing urea groups.

[0085] (2) In an inert gas atmosphere, the monomer obtained in step (1) was dissolved in N,N-dimethylformamide, and 0.5659 mg of azobisisobutyronitrile per gram of monomer was added and mixed thoroughly. The resulting mixture was stirred at 65°C for 24 h. The reaction mixture was precipitated and centrifuged using a water / methanol mixed solvent. The precipitate was dried under vacuum to obtain the side-chain polyurea polymer matrix BPUA with a yield of 78%. Mn = 49663 g / mol, Mw = 87233 g / mol, Mw / Mn = 1.76. The product structure is as follows:

[0086] (3) After dissolving the polymer matrix BPUA and lithium perchlorate separately, they are mixed evenly to make the molar ratio of urea group to lithium bis(trifluoromethanesulfonyl)imide 1:1. The mixture is poured into a polytetrafluoroethylene plate and dried to obtain the superionic solid electrolyte BPSE.

[0087] Example 8

[0088] Preparation of a side-chain type polyurea superionic solid electrolyte

[0089] (1) Under an inert gas atmosphere and at 0°C, p-trifluoromethylaniline (34.0 mmol, 5.48 g) and ethyl 2-isocyanate acrylate (34.0 mmol, 4.86 g) were dissolved in tetrahydrofuran and mixed. The resulting mixture was reacted at 0°C for 4 hours, and then at room temperature for 12 hours. The solution was evaporated to dryness to obtain the product, an acrylate monomer containing urea groups.

[0090] (2) In an inert gas atmosphere, the monomer obtained in step (1) was dissolved in N,N-dimethylformamide, and 0.5659 mg of azobisisobutyronitrile per gram of monomer was added and mixed thoroughly. The resulting mixture was stirred at 65°C for 24 h. The reaction mixture was precipitated and centrifuged using a water / methanol mixed solvent. The precipitate was dried under vacuum to obtain the side-chain polyurea polymer matrix TFPUA, with a yield of 80%. Mn = 70000 g / mol. The product structure is as follows:

[0091] (3) The polymer matrix TFPUA and lithium perchlorate are dissolved and mixed evenly to make the molar ratio of urea group to lithium bis(trifluoromethanesulfonyl)imide 1:1. The mixture is poured into a polytetrafluoroethylene plate and dried to obtain the superionic solid electrolyte TFPSE.

[0092] Example 9

[0093] Preparation of a side-chain type polyurea superionic solid electrolyte

[0094] (1) Under an inert gas atmosphere and at 0°C, m-bis(trifluoromethyl)aniline (34.0 mmol, 7.79 g) and ethyl 2-isocyanate acrylate (34.0 mmol, 4.86 g) were dissolved in tetrahydrofuran and mixed. The resulting mixture was reacted at 5°C for 4 hours, and then at room temperature for 12 hours. The solution was evaporated to dryness to obtain the product, an acrylate monomer containing urea groups.

[0095] (2) In an inert gas atmosphere, the monomer obtained in step (1) was dissolved in N,N-dimethylformamide, and 0.5659 mg of azobisisobutyronitrile per gram of monomer was added and mixed thoroughly. The resulting mixture was stirred and reacted at 70°C for 25 h. The reaction mixture was precipitated using a water / methanol mixed solvent as a precipitant and centrifuged. The precipitate was dried under vacuum to obtain the side-chain polyurea polymer matrix DTFPUA with a yield of 75%. Mn = 31425 g / mol, Mw = 80551 g / mol, Mw / Mn = 2.56. The product structure is as follows:

[0096] (3) After dissolving the polymer matrix DTFPUA and lithium perchlorate respectively, they are mixed evenly to make the molar ratio of urea group to lithium bis(trifluoromethanesulfonyl)imide 1:1. The mixture is poured into a polytetrafluoroethylene plate and dried to obtain the superionic solid electrolyte DTFPSE.

[0097] Comparative Example

[0098] Preparation of a polymer solid electrolyte

[0099] Lithium perchlorate was dissolved in acetonitrile, and polyethylene oxide (PEO matrix) was added to make the mass ratio of polyethylene oxide to lithium perchlorate 3:2. The mixture was stirred for 12 hours to obtain a homogeneous solution, which was then poured into a polytetrafluoroethylene plate and dried to obtain the PEO-based polymer solid electrolyte PEO@LiClO4.

[0100] Application Example 1

[0101] Differential scanning calorimetry (DSC) was performed on the solid electrolytes and their polymer matrices obtained in Examples 1, 5, 6 and the comparative examples: a fixed heating and cooling scan rate of 20 °C / min was used, and the glass transition temperature (Tg) was obtained from the change in heat capacity during the second heating.

[0102] Depend on Figure 8 and Figure 9 It can be observed that the Tg value of the main-chain polythiourea matrix decreases with increasing ether bond content, from 70℃ for PTU1 to 36℃ for PTU2 and 16℃ for PTU3. This is because the introduction of ether bonds strongly disrupts the hydrogen bonds and chain filling in these polythioureas. The Tg values ​​of PSE1 and PSE2 are 53℃ and 29℃, respectively, lower than those of PTU1 and PTU2, while the change in PSE3 is minimal. The Tg decrease caused by the addition of lithium salt further reveals the disruption of hydrogen bonds between polythiourea chains.

[0103] Application Example 2

[0104] Large-angle X-ray diffraction (WAXD) tests were performed on the solid electrolytes obtained in Examples 1, 5, 6, and the comparative examples: under Kα radiation containing Cu. The procedure was performed on a Rigaku Ultima IV instrument. The recording time was 10 minutes.

[0105] Depend on Figure 10 The miscibility of solid electrolytes with lithium perchlorate was determined: only PSE1 exhibited completely amorphous characteristics, with no sharp diffraction peaks in its XRD pattern. In contrast, PSE2, PSE3, and PEO-based solid electrolytes showed sharp diffraction peaks at 21.21° (attributable to lithium perchlorate), with the PEO-based solid electrolyte showing particularly pronounced peaks. This indicates that lithium perchlorate crystallizes severely in PEO-based electrolytes, while exhibiting lower solubility in PTU2 and PTU3. This is consistent with... Figure 4This is consistent with the phenomenon observed in the solid electrolyte photograph where a large amount of lithium perchlorate salt crystallizes out in PEO.

[0106] Application Example 3

[0107] Fourier transform infrared (FT-IR) spectroscopy was performed on the solid electrolytes obtained in Example 1 and the comparative example.

[0108] Depend on Figure 11 In the middle, the peak value is ~621cm -1 The location corresponds to the dissociation of ClO4. - Free anions, and another peak at ~630cm. -1 The corresponding ion pair is LiClO4. Clearly, in PSE1, almost all the perchlorate moiety exists as free anions, indicating that LiClO4 dissolves well in PSE1.

[0109] Application Example 4

[0110] The ionic conductivity of the solid electrolytes obtained in Examples 1-9 and the comparative examples was tested: the solid electrolyte membrane was cut into regular sheets and assembled with stainless steel to form a counter electrode. Electrochemical impedance spectroscopy was used, with a frequency range of 1 Hz to 100 kHz, and measurements were taken at different temperatures. The ionic conductivity (σ) was calculated using the following formula: σ = d / R × S, where σ is the ionic conductivity (S·cm). -1 ), d is the thickness of the electrolyte, R is the volume resistance, and S represents the area in contact with the electrode.

[0111] Depend on Figure 12 The ion transport characteristics of polythiourea superionic electrolyte samples with different LiClO4 doping ratios using PTU1 as the polymer matrix were obtained. When r < 1, the higher the r value, the higher the ionic conductivity in PSE1; when r > 1, the ionic conductivity saturates and no longer increases. Furthermore, the conductivity-temperature relationship at all r values ​​follows Arrhenius-type behavior (i.e., logarithmic conductivity is linearly related to 1 / T). The activation energy of the PSE1 system calculated by the Arrhenius equation is 0.35 eV, which is much lower than the activation energy of the PEO system (0.6–1 eV). Additionally, the ionic conductivity of PSE1 at 30 °C is 3.3 × 10⁻⁶. -5 S·cm -1 Given that PSE1 has a high Tg value of 53℃, an ion hopping transport mechanism was implemented in PSE1.

[0112] Depend on Figure 13 It can be seen that, comparing the ionic conductivity of different main-chain polythiourea and PEO under the condition of r=1, polythiourea has a higher ionic conductivity than PEO. PSE2 and PSE3 have the same level of ionic conductivity, for example, 1×10⁻⁶ at 60℃. -3 S·cm -1 And at 30℃, it is 1×10 -4 S·cm -1 However, PSE1 exhibits a lower activation energy (0.35 eV) than PSE2 (0.61 eV) and PES3 (0.55 eV), which may be due to the ether bond with Li. + A stronger affinity and compatibility.

[0113] Depend on Figure 14 Comparing the ionic conductivity of polyurea and PEO with different side-chain types at room temperature, BPSE has an ionic conductivity of 1.9 × 10⁻⁶. -5 S·cm -1 The ionic conductivity of TFPSE is 2.9 × 10⁻⁶. -5 S·cm -1 The ionic conductivity of DTFPSE is 3.7 × 10⁻⁶. -5 S·cm -1 Polyurea has a higher ionic conductivity than PEO. Furthermore, the ionic conductivity of polyurea increases with the introduction of different electron-withdrawing groups or conjugated groups, as the number and strength of these groups increase.

[0114] Application Example 5

[0115] The solid electrolytes obtained in Examples 1, 5, 6 and the comparative example were subjected to Li... + Migration number testing: Solid electrolyte membranes were cut into regular sheets and assembled with lithium sheets to form a Li / solid electrolyte / Li symmetric battery structure. The Li migration number was measured using the Bruce-Vincent method, combining electrochemical impedance spectroscopy and chronoamperometry. + Number of migrations (tLi) + Li + The migration number is calculated using the following formula: t Li+ =I SS (ΔV-I0R0) / I0(ΔV-I SS R SS ), where ΔV is the applied polarization voltage, I0 and R0 are the initial current and interface resistance before polarization, respectively, I ss and R ss These are the final state current and interface impedance after polarization.

[0116] Depend on Figure 15 Therefore, the calculated Li of PSE1 can be obtained. + The migration number reaches 0.85, far exceeding that of PEO-based polymer electrolytes (0.2–0.5), and even comparable to single-ion conductive polymers (0.8–1.0). With increasing polar ether bond content, the t in PSE2 and PSE3... Li+ The values ​​decreased to 0.69 and 0.58, respectively.

[0117] Application Example 6

[0118] Electrochemical stability tests were conducted on the solid electrolytes obtained in Examples 1, 5, and 6: the solid electrolyte membrane was cut into regular sheets and assembled with lithium sheets to form a Li / solid electrolyte / stainless steel battery structure. Linear voltammetry (LSV) tests were performed using a potentiostat at a scan rate of 1 mV / s and within a potential range of 0-6 V.

[0119] Depend on Figure 16 The LSV curves for PSE1, PSE2, and PSE3 were obtained. All polythiourea superionic solid electrolytes exhibited excellent electrochemical stability up to 4.5 V (vs. Li / Li+). PSE1 and PSE2 could even maintain voltages close to 4.8 V.

[0120] Application Example 7

[0121] The superionic solid polymer electrolytes obtained in Examples 1 and 5 above were subjected to full-cell performance testing. The specific battery assembly test included the following steps:

[0122] (1) By dispersing LFP (or NMC811), Super P and PVDF (weight ratio of 8:1:1) in N-methylpyrrolidone (NMP) and grinding in a ball mill for 4 hours. The slurry is uniformly coated on aluminum foil and vacuum dried at 60°C for 12 hours, and then cut into cathode sheets with a diameter of 16 mm;

[0123] (2) In an Ar-filled glove box (<0.5ppm O2 and <0.5ppm H2O), an LFP (or NMC811) cathode, a superionic polymer electrolyte and a lithium foil anode are assembled in a CR2032 coin cell; the superionic polymer electrolyte and lithium foil are assembled into a Li / solid electrolyte / Li symmetric cell.

[0124] (3) Charge / discharge tests were performed on LFP|PSE|Li and NMC811|PSE|Li batteries using a battery tester. The test conditions were 60℃ constant current at 0.2C, with voltage ranges of 2.8-4.0V and 3.0-4.3V, respectively. The specific capacity was calculated based on the weight of the cathode active material.

[0125] Depend on Figure 17 It can be seen that in the Li|Li symmetric cell at 60℃, at 0.1 mAh·cm -2 At current densities, PSE1 exhibits higher cycling stability than PSE2 electrolyte. Figure 18 As can be seen, PSE1 can significantly improve discharge capacity. The capacity retention of PSE1 reaches approximately 124 mAh·g. -1Superior to approximately 109 mAh·g -1 The PSE2. Furthermore, the polarization between the charge and discharge plateaus of the Li|PSE1|LFP battery is only about 0.14V at the initial cycle of 0.2C, indicating good compatibility and stability between PSE1 and the lithium electrode. Figure 19 It can be seen that after 100 cycles, the discharge capacity of the Li|PSE1|LFP full cell retains 90% of its initial capacity. Furthermore, from... Figure 20 Thus, the capacity of the Li|PSE1|NCM full cell is further increased to 141.8 mAh·g. -1 It also has high and stable coulomb efficiency.

[0126] Unless otherwise specified, the raw materials and equipment used in this invention are all commonly used in the field; unless otherwise specified, the methods used in this invention are all conventional methods in the field.

[0127] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, alterations, and equivalent transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A solid electrolyte comprising a polymer matrix and a lithium metal salt, characterized in that, The polymer matrix is ​​one of main-chain polythiourea, side-chain polythiourea, or polyurea; the structure of the main-chain polythiourea is shown in Formula 1, and the structure of the side-chain polythiourea or polyurea is shown in Formula 2. Formula 1 Formula 2 R1 and R2 are , One or two of them; R3 is either ureido-NH-(C=O)-NH- or thioureo-NH-(C=S)-NH-; R4 is , , , , , One of them.

2. A method for preparing the solid electrolyte according to claim 1, characterized in that, Includes the following steps: The polymer matrix and lithium salt are dissolved separately and then mixed evenly. The mixture is poured into a polytetrafluoroethylene plate and dried to obtain a superionic solid electrolyte. The polymer matrix is ​​one of main-chain polythiourea, side-chain polythiourea, or polyurea. The preparation method of the main-chain polythiourea polymer matrix includes the following steps: S1: In an inert gas atmosphere, sulfur, aliphatic diamine and diisocyanate are mixed in a mass ratio and dissolved in N,N-dimethylformamide; S2: Stir the mixture obtained in step S1 at 40~50℃ for 4~5 hours and then cool it to room temperature. Pass the reaction mixture through a cotton filter and drop it into a hexane / dichloromethane mixed solvent. Wash the resulting precipitate with methanol and then dry it to obtain a main-chain polythiourea. The aliphatic diamine mentioned in step S1 is one of 1,6-diaminohexane and 1,8-diamino-3,6-dioxaoctane; the diisocyanate mentioned in step S1 is one of 1,6-diisocyanohexane and 1,2-bis(2-isocyanoethoxy)ethane. The preparation method of side-chain polythiourea or polyurea polymer matrix includes the following steps: T1: Under an inert gas atmosphere and at 0°C, aliphatic amines or aromatic amines and isocyanates or thioisocyanates are dissolved in tetrahydrofuran in a mass ratio and then mixed; the resulting mixture is reacted at 0~5°C for 4~5 hours, and then reacted at room temperature for 12~14 hours; the solution is evaporated to dryness to obtain the product containing urea or thiourea acrylate monomers. T2: In an inert gas atmosphere, the monomer obtained in step T1 is dissolved in N,N-dimethylformamide, and azobisisobutyronitrile is added and mixed evenly; the resulting mixture is stirred and reacted at 60~70℃ for 24~25h; the reaction mixture is precipitated with a precipitant and centrifuged; the precipitate is dried under vacuum to obtain side-chain polythiourea or polyurea polymer; The fatty amine in step T1 is n-butylamine, and the aromatic amine is one of aniline, 4-n-butylaniline, p-trifluoromethylaniline, m-di(trifluoromethyl)aniline, and 2,3,4,5,6-pentafluoroaniline; the isocyanate in step T1 is ethyl 2-isocyanate acrylate, and the thioisocyanate is methyl 2-isothiocyanoacetate.

3. The method for preparing a solid electrolyte according to claim 2, characterized in that, The lithium salt is one of lithium perchlorate, lithium bis(trifluoromethanesulfonyl)imide, lithium tetrafluoroborate, and lithium bis(difluorosulfonyl)imide, and the lithium salt accounts for 1% to 50% of the total mass of the solid electrolyte.

4. The method for preparing a solid electrolyte according to claim 2, characterized in that, In step T2, 0.5659 mg of azobisisobutyronitrile is added per gram of monomer.

5. The method for preparing a solid electrolyte according to claim 2, characterized in that, The precipitant in step T2 is a water / methanol mixed solvent, with a volume ratio of water to methanol of 1:

4.

6. A secondary battery, comprising a positive electrode, a negative electrode, and an electrolyte, characterized in that, The electrolyte is the solid electrolyte as described in claim 1.

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