Polylactic acid-based solid electrolyte, preparation method and application thereof, and lithium battery

Abstract

The invention provides a polylactic acid-based solid electrolyte, a preparation method and application thereof, and a lithium battery, and belongs to the technical field of solid-state batteries. The polylactic acid-based solid electrolyte provided by the invention comprises a polymer matrix, a lithium salt, an ionic liquid and an ultraviolet light initiator, the polymer matrix comprises a first polymer and a second polymer, the first polymer is polylactic acid, and the second polymer is polyethylene glycol diacrylate and / or polyethylene glycol methacrylate. According to the invention, the easily degradable polylactic acid is introduced into a polymer matrix, the structure of the polylactic acid in the battery is stable, and the polylactic acid can generate degradation reaction after hydrolysis treatment, so that the damage to the environment can be avoided; meanwhile, by adding the ionic liquid, the electrochemical performance such as the ionic conductivity and the cycle performance of the electrolyte is improved, and a guarantee is provided for preparing the high-performance degradable polymer solid electrolyte.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid-state batteries, and specifically relates to a polylactic acid-based solid electrolyte, a preparation method and application thereof, and a lithium battery. Background Art

[0002] Lithium-ion batteries have high specific energy, high rated voltage and are environmentally friendly. They are not only used in digital products such as mobile phones, laptops and tablets, but also in the field of electric vehicles. However, traditional lithium batteries still use liquid organic compounds as electrolytes, which have disadvantages including flammability, volatility, leakage and environmental toxicity. Therefore, research efforts are focused on safe new electrolytes with excellent performance and sustainability, especially solid electrolytes. Compared with liquid organic electrolytes, they are non-volatile and not easy to leak; in addition, they have excellent mechanical properties, ensuring the safety performance of lithium batteries during long-term cycles. At present, solid electrolytes are made of polymer materials, such as polyethylene oxide (PEO), polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA), polypropylene oxide (PPO) and polyvinylidene chloride (PVDC), but these electrolytes are usually difficult to degrade, which will cause a surge in electronic waste pollution and ultimately have a negative impact on the environment.

[0003] In the prior art, degradable materials are incorporated into the polymer matrix of traditional solid electrolytes to construct sustainable solid electrolytes. Among them, polylactic acid (PLA) is one of the most environmentally friendly and biodegradable polymers, which can be produced from renewable sources such as corn sugar, potatoes and sugar cane. Although PLA can be used in degradable solid electrolytes, its ionic conductivity is relatively low, and its conductivity at room temperature is only close to 10 -4 S cm -1 , which cannot meet the requirements of sustainable high-performance solid electrolytes. Summary of the invention

[0004] The purpose of the present invention is to provide a polylactic acid-based solid electrolyte, a preparation method and application thereof, and a lithium battery. The polylactic acid-based solid electrolyte of the present invention is biodegradable and has high ionic conductivity, meeting the requirements of sustainable high-performance solid electrolytes.

[0005] In order to achieve the purpose of the present invention, the present invention provides the following technical solutions:

[0006] A polylactic acid-based solid electrolyte comprising a polymer matrix, a lithium salt, an ionic liquid and an ultraviolet light initiator;

[0007] The polymer matrix comprises a first polymer and a second polymer, wherein the first polymer is polylactic acid, and the second polymer is polyethylene glycol diacrylate and / or polyethylene glycol methacrylate.

[0008] Preferably, the ionic liquid is one or more of N-butyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imide, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-butyl-3-methylimidazolium hexafluorophosphate and 1-butyl-3-methylimidazolium tetrafluoroborate.

[0009] Preferably, the lithium salt is lithium bis(trifluoromethanesulfonyl)imide and / or lithium hexafluorophosphate.

[0010] Preferably, the ultraviolet light initiator includes 2-hydroxy-2-methyl-1-phenyl-1-propanone or 2,4,6-trimethylbenzoyl-diphenylphosphine oxide.

[0011] Preferably, the mass of polylactic acid in the polymer matrix is ​​10% to 50%.

[0012] Preferably, the mass of the ionic liquid accounts for 20 to 40 wt% of the total mass of the polylactic acid-based solid electrolyte;

[0013] The mass of the ultraviolet light initiator accounts for 2-5 wt % of the mass of the polymer matrix.

[0014] The present invention also provides a method for preparing the polylactic acid-based solid electrolyte described in the above technical solution, comprising the following steps:

[0015] The polymer matrix, lithium salt, ionic liquid, ultraviolet light initiator and organic solvent are mixed to obtain a precursor solution;

[0016] The precursor solution is cured by ultraviolet light to obtain the polylactic acid-based solid electrolyte.

[0017] Preferably, the UV curing time is 30 to 60 minutes.

[0018] The present invention also provides the use of the polylactic acid-based solid electrolyte described in the above technical solution or the polylactic acid-based solid electrolyte prepared by the preparation method described in the above technical solution in a secondary battery.

[0019] The present invention also provides a lithium battery, comprising a positive electrode, an electrolyte and a negative electrode, wherein the electrolyte is the polylactic acid-based solid electrolyte described in the above technical solution or the polylactic acid-based solid electrolyte prepared by the preparation method described in the above technical solution.

[0020] The present invention provides a polylactic acid-based solid electrolyte, comprising a polymer matrix, a lithium salt, an ionic liquid and an ultraviolet light initiator; the polymer matrix comprises a first polymer and a second polymer, the first polymer being polylactic acid, and the second polymer being polyethylene glycol diacrylate and / or polyethylene glycol methacrylate. The present invention introduces polylactic acid, which is easily degraded, into the polymer matrix. On the one hand, polylactic acid has polar functional groups ester groups (-COO-) and hydroxyl groups (-OH) that are beneficial to ion conduction; on the other hand, polylactic acid has a certain crystallinity, and the crystalline region can provide mechanical strength to prevent the electrolyte from deforming or breaking during the charge and discharge process, and has a stable structure in the battery, and a degradation reaction can occur after hydrolysis treatment, which can avoid damage to the environment; at the same time, the present invention improves the electrochemical properties of the electrolyte, such as ionic conductivity and cycle performance, by adding ionic liquids, providing a guarantee for the preparation of high-performance degradable polymer solid electrolytes. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 The impedance diagrams of the polylactic acid-based solid electrolytes obtained in Examples 1 to 3 and Comparative Example 1;

[0023] Figure 2 The impedance diagrams of the polylactic acid-based solid electrolytes obtained in Example 4 and Comparative Example 1;

[0024] Figure 3 The linear sweep voltammetry curves of the steel sheet / solid electrolyte / lithium sheet batteries obtained in Example 3 and Comparative Example 1;

[0025] Figure 4 This is a cycle performance diagram of a lithium iron phosphate full battery assembled with a polylactic acid-based solid electrolyte membrane obtained in Comparative Example 1;

[0026] Figure 5 This is a cycle performance diagram of a lithium iron phosphate full battery assembled with a polylactic acid-based solid electrolyte membrane obtained in Example 3;

[0027] Figure 6 The constant current charge-discharge curves of the polylactic acid-based solid electrolyte membrane obtained in Example 3 at the 5th, 50th and 100th cycles;

[0028] Figure 7 This is a cycle performance diagram of a lithium iron phosphate full battery assembled with a polylactic acid-based solid electrolyte membrane obtained in Example 4;

[0029] Figure 8 The lithium-lithium symmetrical battery assembled with the polylactic acid-based solid electrolyte membrane obtained in Comparative Example 1 and Example 3 was tested at 0.1 mA / cm -2 Cyclic test diagram under conditions;

[0030] Fig. 9 This is a degradation change diagram of the polylactic acid-based solid electrolyte membrane obtained in Example 3 under the conditions of 50°C and 1M NaOH solution. DETAILED DESCRIPTION

[0031] The present invention provides a polylactic acid-based solid electrolyte, comprising a polymer matrix, a lithium salt, an ionic liquid and an ultraviolet light initiator;

[0032] The polymer matrix comprises a first polymer and a second polymer, wherein the first polymer is polylactic acid, and the second polymer is polyethylene glycol diacrylate and / or polyethylene glycol methacrylate.

[0033] In the present invention, unless otherwise specified, all preparation raw materials are commercially available products well known to those skilled in the art.

[0034] In the present invention, the polymer matrix includes a first polymer and a second polymer, wherein the first polymer is polylactic acid, and the second polymer is polyethylene glycol diacrylate (PEGDA) and / or polyethylene glycol methacrylate, and in a specific embodiment, it can be polylactic acid and polyethylene glycol diacrylate, polylactic acid or polyethylene glycol methacrylate; the mass of polylactic acid in the polymer matrix is ​​10% to 50%, and in a specific embodiment, it can be 16%, 30% or 42%. The present invention introduces polylactic acid, which is easily degraded, into the polymer matrix, so that the structure of polylactic acid in the battery is stable, and degradation reaction can occur after hydrolysis treatment, thereby avoiding damage to the environment.

[0035] In the present invention, the lithium salt is lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and / or lithium hexafluorophosphate (LiPF 6 ), in a specific embodiment, it can be lithium bis(trifluoromethanesulfonyl)imide. In the present invention, the lithium salt provides conductive ions to ensure effective ion conduction between the positive and negative electrodes of the battery; at the same time, the lithium salt can maintain electrolyte stability and participate in battery reactions.

[0036] In the present invention, the ionic liquid is N-butyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imide salt (Pyr 14 TFSI), 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide salt ([EMIM]TFSI), 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF 6 ) and 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF 4) or more. In the present invention, the ionic liquid provides ions with high ion concentration and a large number of mobile carriers, which significantly improves the ionic conductivity; the ionic liquid acts as a plasticizer, which can reduce the glass transition temperature of the polymer electrolyte, reduce the crystalline area, and increase the number of lithium ion transport in the non-crystalline area, thereby promoting the migration of ions; at the same time, the ionic liquid has a high dielectric constant, can effectively dissociate lithium salts, increase the concentration of free lithium ions, and improve lithium ion conductivity.

[0037] In the present invention, the ultraviolet light initiator includes 2-hydroxy-2-methyl-1-phenyl-1-propanone (HMPP) or 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO).

[0038] In the present invention, the mass of the ionic liquid accounts for 20-40wt% of the total mass of the polylactic acid-based solid electrolyte, and in a specific embodiment, it can be 30wt% or 35wt%; the mass of the ultraviolet light initiator accounts for 2-5wt% of the mass of the polymer matrix, and in a specific embodiment, it can be 3wt% or 4wt%.

[0039] The present invention also provides a method for preparing the polylactic acid-based solid electrolyte described in the above technical solution, comprising the following steps:

[0040] The polymer matrix, lithium salt, ionic liquid, ultraviolet light initiator and organic solvent are mixed to obtain a precursor solution;

[0041] The precursor solution is cured by ultraviolet light to obtain the polylactic acid-based solid electrolyte.

[0042] In the present invention, the organic solvent is N-methylpyrrolidone (NMP).

[0043] In the present invention, the mixing is carried out at room temperature and under stirring conditions; the stirring rate is not particularly limited; the mixing time is 1 to 5 hours, and in a specific embodiment, it can be 5 hours.

[0044] In the present invention, the UV curing time is 30 to 60 minutes, and in a specific embodiment, it can be 40 or 50 minutes; the wavelength of the UV light is 10 to 400 nm, and in a specific embodiment, it can be 365 nm. During the UV curing process of the present invention, the molecule transitions from the ground state to the excited state, and then a decomposition reaction occurs to generate free radicals, such as the double bond (C=C) in the PEGDA molecule. Under the action of the free radical, the double bond opens and undergoes a cross-linking reaction with the double bonds of other PEGDA molecules. As the cross-linking reaction in the UV curing proceeds, the PEGDA molecules gradually form a three-dimensional network structure and are finally cured into a polymer electrolyte with a cross-linked network.

[0045] The present invention also provides the use of the polylactic acid-based solid electrolyte described in the above technical solution or the polylactic acid-based solid electrolyte prepared by the preparation method described in the above technical solution in a secondary battery.

[0046] The present invention also provides a lithium battery, comprising a positive electrode, an electrolyte and a negative electrode, wherein the electrolyte is the polylactic acid-based solid electrolyte described in the above technical solution or the polylactic acid-based solid electrolyte prepared by the preparation method described in the above technical solution.

[0047] In the present invention, the lithium battery can be one of a stainless steel symmetrical battery, a lithium-lithium symmetrical battery and a lithium iron phosphate full battery.

[0048] In the present invention, the positive electrode is a composite of a positive electrode active material, a binder and a conductive agent coated on a current collector; the positive electrode active material is lithium iron phosphate; the binder is polyvinylidene fluoride (PVDF); the positive electrode conductive agent is conductive carbon black; the mass ratio of the positive electrode active material, the binder and the conductive agent is 8 to 9:0.5 to 1:0.5 to 1.

[0049] In order to further illustrate the present invention, the polylactic acid-based solid electrolyte, its preparation method and application, and lithium battery provided by the present invention are described in detail below in conjunction with the accompanying drawings and examples, but they should not be understood as limiting the scope of protection of the present invention.

[0050] In the following examples of the present invention, lithium iron phosphate is used as the positive electrode active material, polyvinylidene fluoride is used as the binder, conductive carbon black is used as the conductive agent, and N-methylpyrrolidone is used as the solvent to prepare the positive electrode material. The specific operation is as follows:

[0051] Lithium iron phosphate, polyvinylidene fluoride and conductive carbon black were mixed and ground in a mass ratio of 8:1:1 to obtain 300 mg of the mixture, and the mixture was uniformly mixed in 600 μL of N-methylpyrrolidone (NMP) to obtain a slurry;

[0052] According to 1.5mg cm -2 The slurry was evenly coated on aluminum foil with a coating amount of , and after vacuum drying at 120°C for 12 hours, it was cut into electrodes with a diameter of 12 mm and placed in a glove box for use.

[0053] Example 1

[0054] 0.1 g of polylactic acid, 0.5 g of polyethylene glycol methacrylate and 0.24 g of LiTFSI were placed in a reagent bottle, and 3 mL of N-methylpyrrolidone and 20 wt% of Pyr 14 TFSI and HMPP with a concentration of 2 wt % were stirred for 5 h to obtain a precursor solution;

[0055] The precursor was poured into a glass mold, cured with UV light (365 nm) for 30 min, and after drying, cut into polylactic acid-based solid electrolyte membranes with a diameter of 16 mm and placed in a glove box for later use.

[0056] Example 2

[0057] 0.1 g of polylactic acid, 0.5 g of polyethylene glycol methacrylate and 0.24 g of LiTFSI were placed in a reagent bottle, and 3 mL of N-methylpyrrolidone and 30 wt% of Pyr 14 TFSI and HMPP with a concentration of 2 wt % were stirred for 5 h to obtain a precursor solution;

[0058] The precursor was poured into a glass mold, cured with UV light (365 nm) for 30 min, and after drying, cut into polylactic acid-based solid electrolyte membranes with a diameter of 16 mm and placed in a glove box for later use.

[0059] Example 3

[0060] 0.1 g of polylactic acid, 0.5 g of polyethylene glycol methacrylate and 0.24 g of LiTFSI were placed in a reagent bottle, and 3 mL of N-methylpyrrolidone and 40 wt% of Pyr 14 TFSI and HMPP with a concentration of 2 wt % were stirred for 5 h to obtain a precursor solution;

[0061] The precursor was poured into a glass mold, cured with UV light (365 nm) for 30 min, and after drying, cut into polylactic acid-based solid electrolyte membranes with a diameter of 16 mm and placed in a glove box for later use.

[0062] Example 4

[0063] A polylactic acid-based solid electrolyte membrane was prepared according to the preparation method described in Example 3, except that the ionic liquid was [EMIM]TFSI].

[0064] Example 5

[0065] A polylactic acid-based solid electrolyte membrane was prepared according to the preparation method described in Example 3, except that the polymer matrix was 0.1 g polylactic acid and 0.5 g polyethylene glycol diacrylate.

[0066] Comparative Example 1

[0067] 0.1 g of polylactic acid, 0.5 g of polyethylene glycol methacrylate and 0.24 g of LiTFSI were placed in a reagent bottle, 3 mL of N-methylpyrrolidone and 2 wt% of HMPP were added, and stirred for 5 h to obtain a precursor solution;

[0068] The precursor was poured into a glass mold, cured with UV light (365 nm) for 30 min, and after drying, cut into polylactic acid-based solid electrolyte membranes with a diameter of 16 mm and placed in a glove box for later use.

[0069] Application Examples

[0070] The polylactic acid-based solid electrolyte membranes obtained in Examples 1 to 5 and Comparative Example 1 were assembled into a battery, and the specific steps are as follows:

[0071] The battery was assembled in an argon-filled glove box (O 2 <0.1ppm,H 2 O<0.1ppm), and the diameter of the lithium sheet used was 15mm.

[0072] Stainless steel symmetrical battery: Use a CR2032 battery shell, place the negative electrode shell, spring sheet, gasket, polylactic acid-based solid electrolyte membrane, gasket in sequence, and finally cover the negative electrode shell, seal it with a button battery sealing machine, and obtain an assembled stainless steel symmetrical battery.

[0073] Lithium-lithium symmetrical battery: Use a CR2032 battery shell, place the negative electrode shell, spring sheet, gasket, lithium sheet, polylactic acid-based solid electrolyte membrane, lithium sheet in sequence, and finally cover the negative electrode shell, seal it with a button battery sealing machine to obtain an assembled lithium-lithium symmetrical battery.

[0074] Lithium iron phosphate full battery (LFP full battery): Use a CR2032 battery shell, place the negative electrode shell, spring sheet, gasket, lithium sheet, polylactic acid-based solid electrolyte membrane, and positive electrode sheet in sequence, and finally cover the negative electrode shell and seal it with a button battery sealing machine to obtain an assembled lithium iron phosphate full battery.

[0075] Test Case

[0076] (1) Ionic conductivity test: The polylactic acid-based solid electrolyte membranes obtained in Comparative Example 1 and Examples 1 to 4 were assembled into a stainless steel symmetrical battery according to the method described in the application example, and its impedance was tested;

[0077] According to the formula shown in formula I, the ionic conductivity of the polylactic acid-based solid electrolyte membranes obtained in Comparative Example 1 and Examples 1 to 4 assembled into a stainless steel pair was calculated. The results are as follows: Figure 1 As shown:

[0078] σ = L / (A × R) Formula I;

[0079] In formula I, σ represents the conductivity (S / cm), L represents the thickness of the polymer electrolyte membrane (μm), and A represents the contact area between the stainless steel gasket and the electrolyte membrane (cm 2 ), R is the body impedance (Ω).

[0080] Depend on Figure 1The results show that after adding different concentrations of ionic liquid to the electrolyte membrane, the conductivity is significantly improved with the increase of ionic liquid concentration. 14 The electrolyte membrane of TFSI ionic liquid (Example 3) has the highest conductivity, which is 7.61×10 -4 S cm -1 .

[0081] Depend on Figure 2 The results show that adding 40% [EMIM]TFSI] ionic liquid to the electrolyte membrane increases the conductivity to 2.1×10 -3 S cm -1 .

[0082] (2) According to the method described in the application example, the polylactic acid-based solid electrolyte membranes obtained in Comparative Example 1 and Example 3 were assembled into a steel sheet / solid electrolyte / lithium sheet battery, and the electrochemical window thereof was tested. The results are as follows: Figure 3 As shown:

[0083] Depend on Figure 3 The results show that the addition of Pyr 14 TFSI ionic liquid improves the high voltage resistance of the polylactic acid-based solid electrolyte and improves the electrochemical stability window of the polylactic acid-based solid electrolyte. The oxidation decomposition voltage of Comparative Example 1 is 4.2V, and the oxidation decomposition voltage of Example 3 is about 4.7V.

[0084] (3) Battery charge and discharge test: The polylactic acid-based solid electrolyte membranes obtained in Comparative Example 1 and Example 3 were assembled into LFP full batteries according to the method described in the application example. The charge and discharge voltage range was 2.5 to 3.8 V. The battery was tested using a CT2001A blue battery test system. The test results are as follows:

[0085] Figure 4 The cycle performance diagram of the lithium iron phosphate full battery assembled with the polylactic acid-based solid electrolyte membrane obtained in Comparative Example 1 is shown in FIG. Figure 4 The results show that the first cycle discharge capacity of the battery can only reach 100 mAh g under 0.1C conditions. -1 .

[0086] Figure 5 The cycle performance diagram of the lithium iron phosphate full battery assembled with the polylactic acid-based solid electrolyte membrane obtained in Example 3 is shown in FIG. Figure 5 The results show that the battery can achieve a discharge capacity of 100 mAh g at 0.5C. -1 The above can stably cycle 100 times, and the coulomb efficiency is close to 100%. Figure 6The constant current charge-discharge curves of the polylactic acid-based solid electrolyte membrane prepared in Example 3 at the 5th, 50th and 100th cycles are shown in FIG. Figure 6 The results show that the electrolyte exhibits a wide electrochemical window and voltage range when matched with lithium iron phosphate. It also maintains stability in the charge and discharge cycle within the voltage range of 2.5V to 3.8V, with small polarization and high specific capacity, indicating that the electrolyte is conducive to the transmission of lithium ions.

[0087] Figure 7 The cycle performance diagram of the lithium iron phosphate full battery assembled with the polylactic acid-based solid electrolyte membrane obtained in Example 4 is shown in FIG. Figure 7 The results show that after 45 cycles at 0.5C, the discharge capacity of the battery increased from 80.49 mAh g -1 Down to 14.25mAh g -1 .

[0088] Figure 8 The graph of the lithium-lithium symmetric battery cycle test assembled with the polylactic acid-based solid electrolyte membrane obtained in Comparative Example 1 and Example 3 is shown in FIG. Figure 8 The results show that at 0.1 mA·cm -2 At a current density of , Example 3 is more stable in charge and discharge than Comparative Example 1, can stably cycle for more than 800 h, and exhibits a smaller polarization voltage (100 mV).

[0089] (4) Degradability test: The polylactic acid-based solid electrolyte membrane obtained in Example 3 was degraded at 50° C. using 1 M NaOH solution. The degradation process is as follows: Fig. 9 As shown by Fig. 9 The results show that after 8 hours of degradation treatment, the polylactic acid-based solid electrolyte membrane can be completely degraded, which proves that the polylactic acid-based solid electrolyte membrane prepared in the present invention has a high efficiency of degradation ability.

[0090] From the above analysis, it can be seen that compared with the polylactic acid-based solid electrolyte membrane obtained in Example 1, the conductivity of the assembled battery is significantly better in Examples 1 to 3. Compared with Comparative Example 1, the conductivity of the stainless steel symmetrical battery assembled with the polylactic acid-based solid electrolyte membrane obtained in Examples 1 to 3 is higher, the battery stability is stronger, and the electrochemical window is expanded to 4.9V. The overpotential (Voltage) of the lithium-lithium symmetrical battery assembled with the polylactic acid-based solid electrolyte membrane obtained in Example 3 is smaller, indicating that the impedance of the lithium-lithium symmetrical battery is smaller during charge and discharge, and the lithium-lithium symmetrical battery is 0.1mA·cm -2 The lithium iron phosphate battery can be stably cycled for more than 900 hours at a current density of 0.5C, and the discharge capacity of the lithium iron phosphate battery can reach 100mAh g -1The polylactic acid-based solid electrolyte membrane prepared by the preparation method of the present invention can improve the lithium ion conductivity and electrochemical stability of the polymer electrolyte. At the same time, the polylactic acid-based solid electrolyte membrane of the present invention can be degraded under alkaline hydrolysis conditions, and the reaction is efficient and fast, and has good industrial application prospects and environmental benefits.

[0091] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A polylactic acid-based solid electrolyte, characterized in that: It includes a polymer matrix, a lithium salt, an ionic liquid and an ultraviolet light initiator; The polymer matrix comprises a first polymer and a second polymer, wherein the first polymer is polylactic acid, and the second polymer is polyethylene glycol diacrylate and / or polyethylene glycol methacrylate.

2. The polylactic acid-based solid electrolyte according to claim 1, characterized in that The ionic liquid is one or more of N-butyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imide, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-butyl-3-methylimidazolium hexafluorophosphate and 1-butyl-3-methylimidazolium tetrafluoroborate.

3. The polylactic acid-based solid electrolyte according to claim 1, characterized in that The lithium salt is lithium bis(trifluoromethanesulfonyl)imide and / or lithium hexafluorophosphate.

4. The polylactic acid-based solid electrolyte according to claim 1, characterized in that The ultraviolet light initiator includes 2-hydroxy-2-methyl-1-phenyl-1-propanone or 2,4,6-trimethylbenzoyl-diphenylphosphine oxide.

5. The polylactic acid solid electrolyte according to claim 1, characterized in that The mass of the polylactic acid in the polymer matrix is ​​10% to 50%.

6. The polylactic acid-based solid electrolyte according to claim 1, 2 or 4, characterized in that: The mass of the ionic liquid accounts for 20 to 40 wt% of the total mass of the polylactic acid-based solid electrolyte; The mass of the ultraviolet light initiator accounts for 2-5 wt% of the mass of the polymer matrix.

7. The method for preparing the polylactic acid-based solid electrolyte according to any one of claims 1 to 6, characterized in that: The following steps are involved: The polymer matrix, lithium salt, ionic liquid, ultraviolet light initiator and organic solvent are mixed to obtain a precursor solution; The precursor solution is cured by ultraviolet light to obtain the polylactic acid-based solid electrolyte.

8. The preparation method according to claim 7, characterized in that: The UV curing time is 30 to 60 minutes.

9. Use of the polylactic acid-based solid electrolyte according to any one of claims 1 to 6 or the polylactic acid-based solid electrolyte prepared by the preparation method according to claim 7 or 8 in a secondary battery.

10. A lithium battery comprising a positive electrode, an electrolyte and a negative electrode, characterized in that: The electrolyte is the polylactic acid-based solid electrolyte described in any one of claims 1 to 6 or the polylactic acid-based solid electrolyte prepared by the preparation method described in claim 7 or 8.

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