A polymer solid electrolyte and a battery including the same

Abstract

The application provides a polymer solid-state electrolyte and a battery comprising the polymer solid-state electrolyte. The polymer solid-state electrolyte comprises a high molecular polymer, and a fast ion conductor ceramic material; the high molecular polymer is obtained by reaction of pentaerythritol tetraacrylate, an acrylate containing a hydroxyl group and an isocyanate containing a phenyl group. The polymer solid-state electrolyte of the application contains abundant ether oxygen bonds, can effectively complex lithium ions and accelerate the transmission of lithium ions; meanwhile, the addition of the fast ion conductor ceramic material can fill into the crystallization region of the high molecular polymer, improving the conductivity of the polymer solid-state electrolyte; the introduction of the benzene ring group can improve the mechanical strength of the polymer solid-state electrolyte and inhibit the generation of lithium dendrites. The polymer solid-state electrolyte can be widely applied to polymer solid-state batteries.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of solid-state batteries, and particularly relates to a polymer solid-state electrolyte and a battery comprising the same. BACKGROUND

[0002] With the popularization of new energy vehicles, lithium batteries, as the main components of vehicles, are in increasing demand. Due to the requirement of driving range, the energy density of the battery is increasingly high, and the safety of the battery is increasingly prominent. Safety is still a key factor restricting the application of lithium ion batteries in the field of high power / high energy. At present, a large amount of volatile and flammable carbonate solvents are applied in commercial lithium ion electrolytes. When the battery temperature rises, external force is extruded, overcharge, short circuit and other conditions occur, the battery will appear thermal runaway, combustion and even explosion, which exists great safety hazard.

[0003] The non-liquid electrolyte used in solid-state lithium ion batteries mainly includes polymer electrolyte, oxide electrolyte and sulfide electrolyte. The lithium ion conductivity of the oxide electrolyte is low, and the interface contact between the electrolyte and the electrode is poor. The sulfide electrolyte has not been applied on a large scale due to the high cost of raw material lithium sulfide and harsh production conditions. Therefore, the polymer electrolyte is expected to become the most promising next-generation solid-state electrolyte.

[0004] The existing polymer electrolyte is mainly divided into solid-state polymer electrolyte and gel polymer electrolyte. The main feature of the solid-state polymer electrolyte is excellent mechanical property, but its lithium ion conductivity is low. The gel polymer electrolyte has conductivity comparable to that of liquid electrolyte, but its mechanical property is poor and chemical stability is not good. SUMMARY

[0005] In order to improve the deficiencies of the prior art, the purpose of the present application is to provide a polymer solid-state electrolyte and a battery comprising the same. The present application grafts isocyanate containing phenyl on the oligomer formed by pentaerythritol tetraacrylate and acrylate containing hydroxyl to form a polymer solid-state electrolyte with two-dimensional interpenetrating network structure. The polymer solid-state electrolyte contains rich ether oxygen bond and benzene ring functional group, which can provide lithium ion transmission channel, increase lithium ion migration number, widen the electrochemical window of the polymer solid-state electrolyte, improve the mechanical strength of the polymer solid-state electrolyte, inhibit the generation of lithium dendrite, and improve the electrical performance and safety performance of the battery.

[0006] The purpose of the present application is realized by the following technical scheme:

[0007] A polymer solid-state electrolyte comprises a high molecular polymer, a fast ion conductor ceramic material; the high molecular polymer is obtained by reaction of pentaerythritol tetraacrylate, a hydroxyl-containing acrylate and a phenyl-containing isocyanate.

[0008] According to an embodiment of the present application, the polymer solid-state electrolyte has a two-dimensional interpenetrating network structure.

[0009] According to an embodiment of the present application, the high molecular polymer (in particular, the high molecular polymer contains abundant ether oxygen bonds and benzene ring functional groups) can provide lithium ion transmission channels, improve the electrochemical window of the polymer solid-state electrolyte, and improve the mechanical strength of the polymer solid-state electrolyte.

[0010] According to an embodiment of the present application, the high molecular polymer is obtained by reaction of an oligomer and a phenyl-containing isocyanate, the oligomer being obtained by reaction of pentaerythritol tetraacrylate and a hydroxyl-containing acrylate.

[0011] According to an embodiment of the present application, the high molecular polymer is obtained by reaction of an oligomer and a phenyl-containing isocyanate under the action of a catalyst, the oligomer being obtained by reaction of pentaerythritol tetraacrylate and a hydroxyl-containing acrylate under the action of an initiator.

[0012] According to an embodiment of the present application, the pentaerythritol tetraacrylate has a structural formula as shown in the following formula 1:

[0013]

[0014] According to an embodiment of the present application, the hydroxyl-containing acrylate is at least one selected from 2-hydroxyethyl acrylate, hydroxypropyl acrylate, 2-hydroxymethyl ethyl acrylate, 2-hydroxymethyl propyl acrylate, trimethylolpropane, and trihydroxypropane triacrylate.

[0015] According to an embodiment of the present application, the molar ratio of the pentaerythritol tetraacrylate and the hydroxyl-containing acrylate is 1:1-5, for example, 1:1, 1:1.5, 1:2, 1:3, 1:4 or 1:5.

[0016] According to an embodiment of the present application, the pentaerythritol tetraacrylate and the hydroxyl-containing acrylate react to form an oligomer, which can serve as the backbone structure of the polymer solid-state electrolyte. Both the pentaerythritol tetraacrylate and the hydroxyl-containing acrylate have abundant oxygen-containing functional groups in their molecular formulas, and the O in the functional groups has a lone pair of electrons that can form a chelation effect with free lithium ions, thereby transmitting lithium ions through the backbone of the polymer solid-state electrolyte.

[0017] According to an embodiment of the present application, the isocyanate containing phenyl is selected from at least one of toluene diisocyanate, isophorone diisocyanate, diphenyl methane diisocyanate, dicyclohexyl methane diisocyanate, lysine diisocyanate.

[0018] According to an embodiment of the present application, the molar ratio of the pentaerythritol tetraacrylate and the isocyanate containing phenyl is 1:1-2; for example, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9 or 1:2.

[0019] According to an embodiment of the present application, the isocyanate containing phenyl can be used as a crosslinking agent, and the isocyanate group on the isocyanate can react with the terminal hydroxyl group on the main chain (oligomer) of the polymer solid-state electrolyte to form a high molecular polymer with a two-dimensional interpenetrating network structure, and the high molecular polymer is connected by chemical bonds between molecules, which can effectively improve the stability of the polymer solid-state electrolyte; the structure can also effectively improve the mechanical strength and chemical stability of the polymer solid-state electrolyte, inhibit lithium dendrites, improve the safety performance of the battery, and at the same time, can widen the electrochemical window of the polymer solid-state electrolyte.

[0020] According to an embodiment of the present application, the fast ion conductor ceramic material is selected from at least one of lithium aluminum titanium phosphate (LATP), lithium aluminum germanium phosphate (LAGP), lithium lanthanum zirconium oxide (LLZO), lithium lanthanum titanium oxide (LLZO), lithium phosphate (Li3PO4), lithium lanthanum zirconium tantalum oxide (LLZTO), lithium germanium phosphorus sulfur (LGPS).

[0021] According to an embodiment of the present application, the fast ion conductor ceramic material can be filled in the voids of the two-dimensional interpenetrating network structure.

[0022] According to an embodiment of the present application, the median particle size D50 of the fast ion conductor ceramic material is 1-10 μm. 50

[0023] According to an embodiment of the present application, there will be a crystalline region inside the high molecular polymer, forming an ion trap to hinder the conduction of lithium ions inside the battery, and the fast ion conductor ceramic material as an additive can be filled into the crystalline region of the high molecular polymer to improve the conduction rate and migration number of lithium ions.

[0024] According to an embodiment of the present application, the polymer solid-state electrolyte is applied to a polymer solid-state battery.

[0025] According to an embodiment of the present application, the initiator is selected from at least one of azobisisobutyronitrile, azobisisoheptyl nitrile, dibenzoyl peroxide, diethylhexyl peroxydicarbonate, sodium persulfate or potassium persulfate. ​

[0026] According to an embodiment of the present application, the catalyst is selected from at least one of dibutyltin dilaurate, stannous octoate.

[0027] According to an embodiment of the present application, the high molecular polymer has a mass percentage of 80% to 95% in the total mass of the polymer solid electrolyte; for example, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, or 95%.

[0028] According to an embodiment of the present application, the fast ion conductor ceramic material has a mass percentage of 5% to 20% in the total mass of the polymer solid electrolyte; for example, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20%.

[0029] The present application also provides a preparation method of the polymer solid electrolyte, which comprises the following steps:

[0030] The pentaerythritol tetraacrylate, the hydroxyl-containing acrylate, the phenyl-containing isocyanate, and the fast ion conductor ceramic material are mixed and reacted to prepare the polymer solid electrolyte.

[0031] According to an embodiment of the present application, the method comprises the following steps:

[0032] (1) The pentaerythritol tetraacrylate and the hydroxyl-containing acrylate are mixed in an organic solvent to form a dilute solution, and then an initiator is added to react to form an oligomer;

[0033] (2) The phenyl-containing isocyanate and the fast ion conductor ceramic material are added to the oligomer obtained in step (2) to react to prepare the polymer solid electrolyte.

[0034] According to an embodiment of the present application, in step (1), the reaction temperature is 20°C to 40°C, for example, 20°C, 25°C, 30°C, 35°C, or 40°C.

[0035] According to an embodiment of the present application, in step (1), the reaction time is 1 to 5 hours, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, or 5 hours.

[0036] According to an embodiment of the present application, in step (2), the reaction temperature is 40°C to 80°C, for example, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, or 80°C.

[0037] According to an embodiment of the present application, in step (2), the reaction time is 24h-72h, such as 24h, 30h, 36h, 40h, 48h, 50h, 55h, 60h, 65h or 72h.

[0038] According to an embodiment of the present application, in step (2), the reaction is under inert or vacuum atmosphere.

[0039] According to an embodiment of the present application, the preparation method comprises the following steps:

[0040] (i) mixing pentaerythritol tetraacrylate and hydroxyl-containing acrylate in an organic solvent to form a dilute solution, then adding an initiator, and continuously stirring to form an oligomer;

[0041] (ii) adding a phenyl-containing isocyanate and a fast ionic conductor ceramic material to the oligomer obtained in step (i), and continuously stirring to form a precursor solution;

[0042] (iii) pouring the precursor solution obtained in step (ii) into a polytetrafluoroethylene mold, under inert or vacuum atmosphere, ensuring that the ambient temperature is 40℃-80℃, and the solvent volatilization time is 24h-72h, to prepare the polymer solid electrolyte.

[0043] According to an embodiment of the present application, the organic solvent is selected from at least one of acetone, tetrahydrofuran, chloroform, acetonitrile, and methyl ethyl carbonate.

[0044] The present application also provides the use of the above-mentioned polymer solid electrolyte in a battery.

[0045] The present application also provides a separator comprising the above-mentioned polymer solid electrolyte.

[0046] According to an embodiment of the present application, the polymer solid electrolyte can be formed into a film alone as a polymer solid electrolyte film, and arranged between the positive and negative electrodes to assemble a solid-state battery with the positive and negative electrodes.

[0047] The present application also provides a composite separator comprising the above-mentioned polymer solid electrolyte and a separator substrate, wherein the polymer solid electrolyte is arranged on at least one side surface of the separator substrate.

[0048] According to an embodiment of the present application, the separator substrate is selected from at least one of non-woven fabric, polypropylene, polyethylene, polyethylene and polypropylene composite material, polyamide, polyethylene terephthalate, polybutylene terephthalate, polystyrene, and poly-p-phenylene.

[0049] According to an embodiment of the present application, the polymer solid-state electrolyte can be arranged on at least one side surface of the diaphragm substrate to form a composite diaphragm, and arranged between the positive and negative electrodes to assemble the solid-state battery.

[0050] According to an embodiment of the present application, the polymer solid-state electrolyte is coated on at least one side surface of the diaphragm substrate by spraying, which can greatly save the cost of production line transformation from liquid-state battery production to solid-state battery production without changing the existing production equipment.

[0051] The present application also provides a battery comprising the polymer solid-state electrolyte described above, or comprising the diaphragm described above, or comprising the composite diaphragm described above.

[0052] According to an embodiment of the present application, the battery is a lithium ion battery, such as a solid-state lithium ion battery.

[0053] The present application has the following beneficial effects:

[0054] The present application provides a polymer solid-state electrolyte and a battery comprising the same. The polymer solid-state electrolyte of the present application contains abundant ether oxygen bonds, which can effectively complex lithium ions and accelerate the transmission of lithium ions. Meanwhile, the addition of fast ion conductor ceramic material can fill into the crystalline region of the polymer, thereby improving the conductivity of the polymer solid-state electrolyte. The introduction of benzene ring groups can improve the mechanical strength of the polymer solid-state electrolyte and inhibit the generation of lithium dendrites. The polymer solid-state electrolyte can be widely applied to polymer solid-state batteries. BRIEF DESCRIPTION OF DRAWINGS

[0055] Figure 1 : Structure diagram of the polymer solid-state electrolyte with two-dimensional interpenetrating network structure of the present application.

[0056] Figure 2 : Cross-section electron microscope image of the polymer solid-state electrolyte of Example 1. DETAILED DESCRIPTION

[0057] The present application will be further described in detail below with reference to specific examples. It should be understood that the following examples are only illustrative and explanatory of the present application, and should not be interpreted as limiting the scope of protection of the present application. Any technology realized based on the above description of the present application is covered within the scope of protection intended by the present application.

[0058] The experimental methods used in the following examples are conventional methods unless otherwise specified; the reagents, materials, etc. used in the following examples can be obtained from commercial channels unless otherwise specified.

[0059] Example 1

[0060] Pentaerythritol tetraacrylate, 2-hydroxyethyl acrylate and azobisisobutyronitrile were mixed in acetone at a molar ratio of 1:2:0.03, stirred at room temperature for 2h to form a dilute solution; then toluene diisocyanate with a molar ratio of 1:1.2 to pentaerythritol tetraacrylate was added, followed by the addition of a catalyst dibutyltin dilaurate accounting for 1% of the total mass of the polymerization monomers (pentaerythritol tetraacrylate, 2-hydroxyethyl acrylate and toluene diisocyanate), and continuous stirring to form a glue solution; then LLZTO accounting for 10% of the total mass of the polymer was added, and the mixture was stirred at 50°C for 24h to form a mixed solution, which was poured into a polytetrafluoroethylene mold and placed in a vacuum oven at 55°C, and the solvent evaporation time was 48h; a polymer solid electrolyte was obtained.

[0061] Example 2

[0062] Pentaerythritol tetraacrylate, 2-hydroxyethyl acrylate and azobisisobutyronitrile were mixed in acetone at a molar ratio of 1:2:0.03, stirred at room temperature for 2h to form a dilute solution; then toluene diisocyanate with a molar ratio of 1:1.2 to pentaerythritol tetraacrylate was added, followed by the addition of a catalyst dibutyltin dilaurate accounting for 1% of the total mass of the polymerization monomers (pentaerythritol tetraacrylate, 2-hydroxyethyl acrylate and toluene diisocyanate), and continuous stirring to form a glue solution; then LLZTO accounting for 10% of the total mass of the polymer was added, and the mixture was stirred at 50°C for 24h to form a mixed solution; the mixed solution was poured into a polytetrafluoroethylene mold and placed in a vacuum oven at 55°C, and the solvent evaporation time was 48h; a polymer solid electrolyte was obtained.

[0063] Example 3

[0064] Pentaerythritol tetraacrylate, 2-hydroxyethyl acrylate and azobisisobutyronitrile were mixed in acetone at a molar ratio of 1:2:0.03, stirred at room temperature for 2h to form a dilute solution; then toluene diisocyanate with a molar ratio of 1:1.2 to pentaerythritol tetraacrylate was added, followed by the addition of a catalyst dibutyltin dilaurate accounting for 1% of the total mass of the polymerization monomers (pentaerythritol tetraacrylate, 2-hydroxyethyl acrylate and toluene diisocyanate), and continuous stirring to form a glue solution; then LLZTO accounting for 10% of the total mass of the polymer was added, and the mixture was stirred at 50°C for 24h to form a mixed solution; the mixed solution was poured into a polytetrafluoroethylene mold and placed in a vacuum oven at 55°C, and the solvent evaporation time was 48h; a polymer solid electrolyte was obtained.

[0065] Comparative Example 1

[0066] Pentaerythritol tetraacrylate and azobisisobutyronitrile were mixed in acetone at a molar ratio of 1:0.03, stirred at room temperature for 2h to form a dilute solution; then 10% of the total mass of pentaerythritol tetraacrylate was added to LLZTO, stirred at 50°C for 24h to form a mixed solution; the mixed solution was poured into a polytetrafluoroethylene mold, placed in a vacuum oven at 55°C, and the solvent was evaporated for 48h; a polymer solid electrolyte was obtained.

[0067] Comparative Example 2

[0068] Pentaerythritol tetraacrylate, 2-hydroxyethyl acrylate and azobisisobutyronitrile were mixed in acetone at a molar ratio of 1:2:0.03, stirred at room temperature for 2h to form a dilute solution; then 10% of the total mass of pentaerythritol tetraacrylate was added to LLZTO, stirred at 50°C for 24h to form a mixed solution; the mixed solution was poured into a polytetrafluoroethylene mold, placed in a vacuum oven at 55°C, and the solvent was evaporated for 48h; a polymer solid electrolyte was obtained.

[0069] Comparative Example 3

[0070] The difference between this comparative example and Example 1 is that no fast ion ceramic electrolyte LLZTO is added, and the other conditions and parameters are exactly the same as in Example 1.

[0071] Performance test:

[0072] The polymer solid electrolytes of Examples 1-3 and Comparative Examples 1-3 were combined with stainless steel sheets to form half-batteries, and linear cyclic voltammetry was tested in the voltage range of 1.0V-5.5V to calculate the electrochemical window; at the same time, the polymer solid electrolytes of Examples 1-3 and Comparative Examples 1-3 were combined with lithium iron phosphate and graphite electrode sheets to form button cells, which were cycled 100 times at a charge-discharge rate of 0.2C in the voltage range of 2.5V-4.2V at 25°C, and the capacity retention rate was calculated, with the test results as follows:

[0073] Sample Electrochemical window / V 100 cycle discharge capacity retention / % Comparative Example 1 3.92 45.32％ Comparative Example 2 4.34 64.81％ Comparative Example 3 4.65 84.91％ Example 1 4.76 92.13％ Example 2 4.70 91.08％ Example 3 4.69 89.64％

[0074] From the above test results, it can also be seen that the discharge capacity retention rate of the batteries of Comparative Examples 1-3 decreases significantly after 100 cycles, indicating that metal lithium dendrites may have been formed, while the discharge capacity retention rate of the batteries of Examples 1-3 remains stable after 100 cycles, proving that no metal lithium dendrites are formed.

[0075] The above describes embodiments of the present application. However, the present application is not limited to the above embodiments. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A polymer solid-state electrolyte, characterized by, The polymer solid electrolyte is composed of a high molecular polymer and a fast ion conductor ceramic material; the high molecular polymer is obtained by reaction of pentaerythritol tetraacrylate, hydroxyl-containing acrylate and phenyl-containing isocyanate; the high molecular polymer is prepared by grafting phenyl-containing isocyanate on an oligomer formed by pentaerythritol tetraacrylate and hydroxyl-containing acrylate. The polymer solid electrolyte has a two-dimensional interpenetrating network structure.

2. The polymer solid-state electrolyte according to claim 1, characterized by, The high molecular polymer is obtained by reaction of an oligomer and phenyl-containing isocyanate, and the oligomer is obtained by reaction of pentaerythritol tetraacrylate and hydroxyl-containing acrylate.

3. The polymer solid-state electrolyte according to claim 1, wherein The hydroxyl-containing acrylate is at least one selected from 2-hydroxyethyl acrylate, hydroxypropyl acrylate, 2-hydroxymethyl ethyl acrylate, 2-hydroxymethyl propyl acrylate, trimethylolpropane and trihydroxypropyl acrylate.

4. The polymer solid-state electrolyte of claim 1, wherein The molar ratio of the pentaerythritol tetraacrylate and the hydroxyl-containing acrylate is 1:1-5.

5. The polymer solid-state electrolyte of claim 1, wherein The phenyl-containing isocyanate is at least one selected from toluene diisocyanate, isophorone diisocyanate, diphenyl methane diisocyanate, dicyclohexyl methane diisocyanate and lysine diisocyanate. The molar ratio of the pentaerythritol tetraacrylate and the phenyl-containing isocyanate is 1:1-2.

6. The polymer solid-state electrolyte of claim 1, wherein The fast ion conductor ceramic material is at least one selected from lithium aluminum titanium phosphate (LATP), lithium aluminum germanium phosphate (LAGP), lithium lanthanum zirconium oxide (LLZO), lithium lanthanum titanium oxide (LLZO), lithium phosphate (Li3PO4), lithium lanthanum zirconium tantalum oxide (LLZTO) and lithium germanium phosphorus sulfur (LGPS).

7. The polymer solid-state electrolyte of claim 1, wherein The mass percentage of the fast ion conductor ceramic material in the total mass of the polymer solid electrolyte is 5%-20%, and the mass percentage of the high molecular polymer in the total mass of the polymer solid electrolyte is 80%-95%.

8. A separator comprising the polymer solid electrolyte according to any one of claims 1-7.

9. A composite separator comprising the polymer solid electrolyte according to any one of claims 1-7 and a separator substrate, and the polymer solid electrolyte is arranged on at least one side surface of the separator substrate.

10. A battery comprising the polymer solid electrolyte according to any one of claims 1-7, or the battery comprises the separator according to claim 8, or the battery comprises the composite separator according to claim 9.

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