A modified high-pressure-resistant gel electrolyte based on lithium nitrate and application thereof

Abstract

The application specifically relates to a modified high-pressure-resistant gel electrolyte based on lithium nitrate and application thereof, and adopts a polymer substrate and a porous support framework to construct a gel electrolyte, wherein polymer monomers are polymerized in the porous support framework to form a gel electrolyte with a multiple cross-linking network structure; meanwhile, the multiple cross-linking compact network structure has a binding effect on liquid molecules, reduces the existence of free liquid molecules, thereby improving the thermal stability of the electrolyte and avoiding leakage and the like, and overall improves the safety performance of a battery. Lithium nitrate is low in cost, low in environmental sensitivity and good in compatibility with a lithium metal negative electrode, and when applied in a lithium ion battery, the safety performance and electrochemical performance of the lithium battery can be effectively balanced.

Description

Technical Field

[0001] This invention relates to the field of polymer electrolyte technology, specifically to a modified high-pressure resistant gel electrolyte based on lithium nitrate and its applications. Background Technology

[0002] Commercial lithium-ion battery liquid electrolytes consist of fluorinated lithium salts and solvents. Fluorinated lithium salts are sensitive to air and water, easily producing byproducts such as hydrofluoric acid and corroding the lithium-ion battery current collector. Lithium nitrate is often introduced into lithium-ion battery systems as an additive, facilitating the formation of a relatively stable passivation layer on the electrode surface and aiding in the construction of high-voltage batteries. Replacing traditional lithium salts with lithium nitrate can significantly reduce the cost and environmental sensitivity of the electrolyte; however, lithium nitrate has low solubility in traditional carbonate electrolytes, resulting in low ionic conductivity and easy lithium salt precipitation, hindering its application in electrolyte systems. Lithium-ion battery systems constructed using an "electrolyte + separator" configuration still suffer from leakage problems.

[0003] Therefore, it is necessary to provide a high-pressure resistant gel electrolyte with good ion transport capabilities, which can match high-specific-energy cathodes at room temperature and maintain good safety performance to overcome the above problems. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings and deficiencies of the existing technology and to provide a modified high-pressure resistant gel electrolyte based on lithium nitrate and its application.

[0005] The first aspect of this invention is to provide a modified high-pressure resistant gel electrolyte based on lithium nitrate, the preparation method of which includes the following steps:

[0006] (1) Mix lithium nitrate, lithium salt, and plasticizer, and stir until a clear solution is obtained to obtain solution A;

[0007] (2) Add polymer monomers and initiators to solution A and stir until a clear solution is obtained to obtain solution B;

[0008] (3) The solution B is added to the porous support framework, and the solution B is polymerized by ultraviolet light or heating at 40~100℃ to form a polymer substrate, thereby obtaining a gel electrolyte with a multi-crosslinked network structure in which the polymer substrate network and the porous support framework network are crosslinked.

[0009] Preferably, in step (1), the dielectric constant ε of the plasticizer is 5~90, and the number of donors DN of the cosolvent is 15~30.

[0010] Preferably, in solution B, the mass of lithium salt is 0.1-50% of the mass of plasticizer, the mass of lithium nitrate is 10-90% of the mass of plasticizer, the mass ratio of plasticizer to polymer monomer is 9:1-1:9, and the initiator content is 0.1-50% of the mass of polymer monomer.

[0011] Preferably, in step (1), the lithium salt is selected from at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(oxalate)borate, and lithium difluorooxalateborate.

[0012] Preferably, in step (1), the plasticizer is selected from ether solvents or ester solvents.

[0013] Preferably, the plasticizer includes at least one selected from the following: ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, 1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, ethylene carbonate, vinylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethyl acetate, trimethyl phosphate, trimethyl phosphite, triethyl phosphate, triethyl phosphite, succinate, and adiponitrile.

[0014] Preferably, in step (2), the polymer monomer is selected from at least one of acrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, tert-butyl acrylate, polyethylene glycol dimethacrylate, ethoxylated trimethylolpropane triacrylate, pentaerythritol tetraacrylate, methoxy polyethylene glycol methacrylate, ethylene oxide, and acrylonitrile.

[0015] Preferably, in step (3), the porous support frame is one or more of polyethylene diaphragm, polypropylene diaphragm, glass fiber diaphragm, qualitative filter paper, polyimide diaphragm, and para-aramid diaphragm.

[0016] The initiator is a photoinitiator or a thermal initiator.

[0017] The photoinitiator is at least one of 2,4-dihydroxybenzophenone, α,α-diethoxyacetophenone, α-hydroxyalkylbenzophenone, α-aminealkylbenzophenone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, arylphosphine oxide, bisbenzoylphenylphosphine oxide, 1-hydroxycyclohexylphenyl ketone, ethyl 2,4,6-trimethylbenzoylphenylphosphonate, benzophenone, benzoin ethyl ether, diphenyl ethyl ketone, α,α-dimethoxy-α-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropanone, 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone, thiopropoxythioxanthonone, isopropylthioxanthonone, benzoin, benzoin dimethyl ether, benzoin isopropyl ether, benzoin butyl ether, and 2,4-dihydroxybenzophenone.

[0018] The thermal initiator is at least one of azobisisobutylamidine hydrochloride, dicumyl peroxide, dimethyl azobisisobutyrate, benzoyl peroxide, azobisisobutyronitrile, ammonium persulfate, diisopropyl peroxide, dicyclohexyl peroxide, methyl ethyl ketone peroxide, and cyclohexanone peroxide.

[0019] A second aspect of the present invention is to provide an application as an electrolyte in a modified high-voltage resistant gel electrolyte lithium-ion battery as described above.

[0020] The beneficial effects of this invention are as follows: Using lithium nitrate as the main salt in the gel electrolyte achieves excellent lithium nitrate solubility over a wide concentration range, improving the electrolyte's ionic conductivity and stability. Lithium nitrate as the main salt facilitates the construction of a passivation interface layer rich in inorganic matter, enabling its compatibility and stable operation with the high-voltage cathode. A gel electrolyte is constructed using a polymer substrate and a porous support framework. During the polymerization of polymer monomers into the polymer substrate within the porous support framework, the polymer substrate network crosslinks with the porous support framework network, forming a gel electrolyte with a multi-layered crosslinked network structure. This strengthens the interaction between the crosslinked network and the plasticizer liquid solvent molecules. Simultaneously, the dense, multi-layered crosslinked network structure binds the liquid molecules, making them less volatile, thereby improving the electrolyte's thermal stability and preventing leakage, thus enhancing the overall battery safety performance. Its application in lithium-ion batteries can effectively balance the safety and electrochemical performance of lithium batteries. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, obtaining other drawings based on these drawings without creative effort still falls within the scope of the present invention.

[0022] Figure 1 is an optical photograph of the gel electrolyte of Example 1 prepared using the present invention;

[0023] Figure 2 shows the cyclic voltammetry test results of the gel electrolytes prepared using Examples 1 and 2 of the present invention;

[0024] Figure 3 shows the long-cycle charge-discharge diagram of the gel electrolyte prepared using Examples 1 and 2 of the present invention in a lithium cobalt oxide half-cell at a voltage range of 3.0V-4.5V and a rate of 0.5C.

[0025] Figure 4 Safety testing of the pouch battery assembled using Embodiment 1 of the present invention. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings.

[0027] Example 1

[0028] (a1) Lithium nitrate (LiNO3) was dissolved in triethylene glycol dimethyl ether (TEGDME) at a molar concentration of 0.95 mol / L. After complete dissolution, lithium bisfluorosulfonyl imide (LiFSI) was added to obtain solution A, in which the molar ratio of LiNO3 to LiFSI was 95:5.

[0029] (a2) Photoinitiator 2-hydroxy-2-methylphenylacetone (HMPP) and ethoxylated trimethylolpropane triacrylate (ETPTA) are added sequentially to solution A to obtain solution B. The mass ratio of ETPTA to solution A is 1:5, and HMPP accounts for 1% of the mass of ETPTA.

[0030] (a3) Inject solution B into a polypropylene membrane and place it in an ultraviolet curing machine for 1 hour to polymerize the monomers, thereby obtaining a high-pressure resistant gel electrolyte with lithium nitrate as the main salt.

[0031] Example 2

[0032] (a1) Lithium nitrate (LiNO3) was dissolved in triethylene glycol dimethyl ether (TEGDME) at a molar concentration of 1.9 mol / L. After complete dissolution, lithium bisfluorosulfonyl imide (LiFSI) was added to obtain solution A, in which the molar ratio of LiNO3 to LiFSI was 95:5.

[0033] (a2) Photoinitiator 2-hydroxy-2-methylphenylacetone (HMPP) and ethoxylated trimethylolpropane triacrylate (ETPTA) are added sequentially to solution A to obtain solution B. The mass ratio of ETPTA to solution A is 1:5, and HMPP accounts for 1% of the total mass of ETPTA.

[0034] (a3) Inject solution B into a polypropylene membrane and place it in an ultraviolet curing machine for 1 hour to polymerize the monomers, thereby obtaining a high-pressure resistant gel electrolyte with lithium nitrate as the main salt.

[0035] Example 3

[0036] (a1) Lithium nitrate (LiNO3) was dissolved in triethyl phosphate (TEP) at a molar concentration of 0.95 mol / L. After complete dissolution, lithium difluoromethanesulfonyl imide (LiFSI) was added to obtain solution A, in which the molar ratio of LiNO3 to LiFSI was 95:5.

[0037] (a2) The thermal initiator azobisisobutyronitrile (AIBN) and ethoxylated trimethylolpropane triacrylate (ETPTA) are added sequentially to solution A to obtain solution B. The mass ratio of ETPTA to solution A is 1:5, and HMPP accounts for 1% of the total mass of ETPTA.

[0038] (a3) Solution B was injected into a polypropylene membrane and heated on an 80°C heating platform for 10 hours to obtain a high-pressure resistant gel electrolyte with lithium nitrate as the main salt.

[0039] Example 4

[0040] The difference from Example 3 is that triethyl phosphate (TEP) is replaced with triethylene glycol dimethyl ether (TEGDME).

[0041] Example 5

[0042] The difference between Example 5 and Example 1 is that the lithium difluoromethanesulfonylimide is replaced by any one of lithium difluorosulfonylimide, lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(oxalato)borate, and lithium difluorooxalatoborate, while the other preparation conditions are the same.

[0043] Example 6

[0044] The difference between Example 6 and Example 1 is that the ethoxylated trimethylolpropane triacrylate (ETPTA) is replaced with at least one of acrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, tert-butyl acrylate, polyethylene glycol dimethacrylate, ethoxylated trimethylolpropane triacrylate, pentaerythritol tetraacrylate, methoxylated polyethylene glycol methacrylate, ethylene oxide, and acrylonitrile, while the other preparation conditions remain the same.

[0045] Example 7

[0046] The difference between Example 7 and Example 1 is that the triethylene glycol dimethyl ether (TEGDME) is replaced with at least one of the following: ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol diethyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, 1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, ethylene carbonate, vinylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethyl acetate, trimethyl phosphate, trimethyl phosphite, triethyl phosphate, triethyl phosphite, succinate, and adiponitrile; all other preparation conditions remain the same.

[0047] Application examples

[0048] The gel electrolyte prepared in the above embodiments of the present invention is used as the electrolyte of a lithium battery.

[0049] The high-voltage resistant gel electrolytes prepared in Examples 1-7 of this invention were matched with lithium cobalt oxide high-voltage cathodes at 0.1 mV s. -1 The CV curves at the scan rate show that lithium-ion transport is fast, and it has a wide charge-discharge range of 3.0-4.5V, exhibiting good high-voltage resistance. Figure 2 Meanwhile, the lithium cobalt oxide half-cell prepared with this electrolyte still retains 130 mAh g⁻¹ after multiple cycles at 0.5C. -1 With its high discharge specific capacity and rapid ion transport, it can be used as a fast-charging lithium-ion battery in the future. Figure 3 The gel electrolyte was assembled into a small pouch cell, which continued to power the device normally after shear failure without thermal runaway or other problems, indicating that this type of electrolyte membrane has excellent application prospects in the construction of high-safety battery systems. Figure 4 ).

[0050] The above description discloses only preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A modified high-voltage resistant gel electrolyte based on lithium nitrate, characterized in that, Its preparation method includes the following steps: (1) Mix lithium nitrate, lithium salt, and plasticizer, and stir until a clear solution is obtained to obtain solution A; (2) Add polymer monomers and initiators to solution A and stir until a clear solution is obtained to obtain solution B; (3) The solution B is added to the porous support framework, and the solution B is polymerized by ultraviolet light irradiation or heating at 40~100℃ to form a polymer substrate, thereby obtaining a gel electrolyte with a multi-crosslinked network structure in which the polymer substrate network and the porous support framework network are crosslinked. The polymer monomer is ethoxylated trimethylolpropane triacrylate, the plasticizer is triethylene glycol dimethyl ether, and the porous support framework is a polypropylene membrane. In solution B, the mass of lithium salt is 0.1-50% of the mass of plasticizer, the mass of lithium nitrate is 10-90% of the mass of plasticizer, the mass ratio of plasticizer to polymer monomer is 9:1-1:9, and the initiator content is 0.1-50% of the mass of polymer monomer.

2. The lithium nitrate-based modified high-voltage resistant gel electrolyte according to claim 1, characterized in that: In step (1), the lithium salt is selected from at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(oxalate)borate, and lithium difluorooxalateborate.

3. The lithium nitrate-based modified high-voltage resistant gel electrolyte according to claim 1, characterized in that: The initiator is a photoinitiator or a thermal initiator. The photoinitiator is at least one of 2,4-dihydroxybenzophenone, α,α-diethoxyacetophenone, α-hydroxyalkylbenzophenone, α-aminealkylbenzophenone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, arylphosphine oxide, bisbenzoylphenylphosphine oxide, 1-hydroxycyclohexylphenyl ketone, ethyl 2,4,6-trimethylbenzoylphenylphosphonate, benzophenone, benzoin ethyl ether, diphenyl ethyl ketone, α,α-dimethoxy-α-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropanone, 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone, thiopropoxythioxanthonone, isopropylthioxanthonone, benzoin, benzoin dimethyl ether, benzoin isopropyl ether, benzoin butyl ether, and 2,4-dihydroxybenzophenone. The thermal initiator is at least one of azobisisobutylamidine hydrochloride, dicumyl peroxide, dimethyl azobisisobutyrate, benzoyl peroxide, azobisisobutyronitrile, ammonium persulfate, diisopropyl peroxide, dicyclohexyl peroxide, methyl ethyl ketone peroxide, and cyclohexanone peroxide.

4. Use as an electrolyte in the modified high-voltage resistant gel electrolyte lithium-ion battery as described in any one of claims 1-3.

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