Gel polymer electrolyte, preparation method thereof and battery

Abstract

The invention discloses a gel polymer electrolyte, a preparation method thereof and a battery. The gel polymer electrolyte comprises a polymer matrix; an electrolyte in the polymer matrix; wherein the polymer matrix comprises a polymer formed by polymerizing a phosphate ester compound as shown in a formula I, in the formula I, R1 and R2 are respectively C1-C4 substituted alkyl or unsubstituted alkyl, and a substituent group in the substituted alkyl is selected from at least one of halogen and cyano; the electrolyte comprises a carbonate solvent and an additive; and the additive comprises lithium disalicylate borate as shown in a formula II. The gel polymer electrolytic electrolyte comprises a polymer formed by polymerizing phosphate monomers and the lithium disalicylate borate, and the polymer and the lithium disalicylate borate have a synergistic effect, so that the oxidation potential of the carbonate electrolyte can be improved, and the battery performance can be improved.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, specifically relating to a gel polymer electrolyte, its preparation method, and a battery. Background Technology

[0002] Commercial lithium-ion battery electrolytes primarily consist of conductive lithium salts (such as LiPF6), linear and cyclic carbonate solvents, and small amounts of functional additives. This is mainly because these electrolytes possess high conductivity, good aluminum foil passivation properties, a wide electrochemical window, and can form a chemically and electrochemically stable solid electrolyte film on the graphite anode surface. However, liquid electrolytes pose risks such as leakage, combustion, and internal short circuits, resulting in a low safety factor and a high likelihood of battery safety issues.

[0003] Gel polymer electrolytes utilize polymer networks to adsorb liquid electrolytes, addressing potential safety issues such as leakage and combustion associated with liquid electrolytes. They also inherit the excellent compatibility between liquid electrolytes and positive and negative electrode materials, making them a key area of ​​focus for industry and academia over the past three decades. However, currently used gel polymer electrolytes still face the challenge of low oxidation potential. Under high-voltage operating conditions, the battery's cycle performance deteriorates, severely limiting the market adoption of gel electrolytes in 4V-class batteries. Summary of the Invention

[0004] This invention aims to at least partially address one of the technical problems in related technologies. Therefore, one object of this invention is to provide a gel polymer electrolyte, its preparation method, and a battery thereof. Through the synergistic effect of a polymer synthesized from phosphate ester monomers and lithium disalicylate borate, the oxidation potential of the gel polymer electrolyte can be increased, ultimately improving battery performance.

[0005] In one aspect of the invention, a gel polymer electrolyte is provided, comprising:

[0006] Polymer matrix;

[0007] Electrolyte located in the polymer matrix;

[0008] The polymer matrix includes polymers formed by polymerizing phosphate ester compounds as shown in Formula I:

[0009]

[0010]

[0011] In Formula I, R1 and R2 are either substituted alkyl groups of C1 to C4 or unsubstituted alkyl groups of C1 to C4, respectively; the substituents in the substituted alkyl groups of C1 to C4 are selected from at least one of halogen and cyano groups;

[0012] The electrolyte includes carbonate solvents and additives;

[0013] The additives include lithium disalicylate borate as shown in Formula II:

[0014]

[0015] The gel polymer electrolyte provided in this application comprises a polymer polymerized from phosphate ester compounds as monomers and a carbonate electrolyte. On one hand, the polymer formed after polymerization of phosphate ester monomers possesses a high oxidation potential, which can be matched with high-voltage cathode materials. On the other hand, lithium bis(salicylate)borate (LiBSB) has excellent film-forming ability, and can oxidize and decompose on the electrode surface to form a high-quality, high-voltage-resistant interface film, thereby increasing the oxidation potential of the carbonate electrolyte. Ultimately, through the synergistic effect of the polymer formed by polymerization of phosphate ester monomers and LiBSB, the oxidation potential of the gel polymer electrolyte can be increased, ultimately achieving the goal of improving battery performance.

[0016] Carboxylic acid ester monomers are commonly used monomers for preparing gel electrolytes, but the polymers formed by the polymerization of carboxylic acid ester monomers have the problem of low oxidation potential, which is inconsistent with high voltage (>4.25V vs. Li / Li). + The compatibility of the cathode material is relatively poor. Compared with carboxylic acid ester monomers, phosphate ester polymers formed by the polymerization of phosphate ester monomers have a higher oxidation potential and better compatibility with high-voltage cathode materials. Moreover, the phosphate ester polymers formed after the polymerization of phosphate ester monomers can reduce the flammability of liquid carbonate electrolytes, greatly improve the thermal stability of gel electrolytes, reduce the risk of thermal runaway of batteries, and thus improve battery safety.

[0017] Taking traditional LiPF6 carbonate electrolyte as an example, the electrolyte has a low oxidation potential, and at high voltages (>4.25V vs. Li / Li), it exhibits a low oxidation potential. +When used in batteries, severe oxidative decomposition of the electrolyte leads to a sharp decline in battery performance. LiBSB, as an additive, can significantly increase the oxidation potential of LiPF6 carbonate electrolyte. This is mainly because LiBSB has excellent film-forming ability, forming substances containing both benzene rings and boron structures on the electrode surface, providing excellent protection for the electrode interface and greatly inhibiting the oxidative decomposition of the carbonate electrolyte. However, the decomposition of LiBSB leads to a decrease in the first-cycle efficiency of the battery and a significant increase in battery impedance, which is detrimental to the battery's capacity and rate performance. The use of phosphate ester monomers can reduce the flammability of the electrolyte and improve the thermal stability of the gel electrolyte. Simultaneously, the phosphate ester polymers formed after the polymerization of phosphate ester monomers participate in the formation of the positive and negative electrode interface films. These polymer-formed interface films can, on the one hand, weaken the decomposition of LiBSB, and on the other hand, the polymers decompose on the electrode surface to form phosphate esters, which are beneficial to Li… + Rapid conduction at the positive and negative electrode interface film ultimately reduces battery impedance.

[0018] In some embodiments of this application, R1 and R2 are respectively substituted alkyl groups of C1 to C2 or unsubstituted alkyl groups of C1 to C2; the substituents in the substituted alkyl groups of C1 to C2 are selected from halogens and cyano groups.

[0019] In some embodiments of this application, the substituents in the substituted alkyl groups of C1 to C4 are fluorine.

[0020] In some embodiments of this application, the polymer matrix has a mass percentage content of 7% to 20% in the gel polymer electrolyte, and the electrolyte has a mass percentage content of 80% to 93% in the gel polymer electrolyte.

[0021] In some embodiments of this application, the additive has a mass percentage content of 0.05% to 5% in the electrolyte.

[0022] In some embodiments of this application, the carbonate solvent includes at least one of ethylene carbonate, propylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate.

[0023] And / or, the electrolyte further includes a lithium salt, including at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bisfluorosulfonylimide, lithium bistrifluoromethylsulfonylimide, lithium bis(oxalate)borate, lithium difluorobis(oxalate)borate, lithium difluorobis(oxalate)phosphate, lithium tetrafluorooxalate phosphate, and lithium 4,5-dicyano-2-trifluoromethyl-imidazolium.

[0024] A second aspect of this application discloses a method for preparing a gel polymer electrolyte, comprising:

[0025] A mixture is prepared by mixing raw materials including the phosphate ester compound shown in Formula I, a crosslinking agent, an initiator, and an electrolyte. The mixture is then subjected to polymerization treatment to obtain the above-mentioned gel polymer electrolyte.

[0026] The gel polymer electrolyte provided in this application comprises a polymer polymerized from phosphate ester compounds as monomers and a carbonate electrolyte. On one hand, the polymer formed after polymerization of phosphate ester monomers possesses a high oxidation potential, which can be matched with high-voltage cathode materials. On the other hand, lithium bis(salicylate)borate (LiBSB) has excellent film-forming ability, and can oxidize and decompose on the electrode surface to form a high-quality, high-voltage-resistant interface film, thereby increasing the oxidation potential of the carbonate electrolyte. Ultimately, through the synergistic effect of the polymer formed by polymerization of phosphate ester monomers and LiBSB, the oxidation potential of the gel polymer electrolyte can be increased, ultimately achieving the goal of improving battery performance.

[0027] Carboxylic acid ester monomers are commonly used monomers for preparing gel electrolytes, but the polymers formed by the polymerization of carboxylic acid ester monomers have the problem of low oxidation potential, which is inconsistent with high voltage (>4.25V vs. Li / Li). + The compatibility of the cathode material is relatively poor. Compared with carboxylic acid ester monomers, phosphate ester polymers formed by the polymerization of phosphate ester monomers have a higher oxidation potential and better compatibility with high-voltage cathode materials. Moreover, the phosphate ester polymers formed after the polymerization of phosphate ester monomers can reduce the flammability of liquid carbonate electrolytes, greatly improve the thermal stability of gel electrolytes, reduce the risk of thermal runaway of batteries, and thus improve battery safety.

[0028] Taking traditional LiPF6 carbonate electrolyte as an example, the electrolyte has a low oxidation potential, and at high voltages (>4.25V vs. Li / Li), it exhibits a low oxidation potential. + When used in batteries, severe oxidative decomposition of the electrolyte leads to a sharp decline in battery performance. LiBSB, as an additive, can significantly increase the oxidation potential of LiPF6 carbonate electrolyte. This is mainly because LiBSB has excellent film-forming ability, forming substances containing both benzene rings and boron structures on the electrode surface, providing excellent protection for the electrode interface and greatly inhibiting the oxidative decomposition of the carbonate electrolyte. However, the decomposition of LiBSB leads to a decrease in the first-cycle efficiency of the battery and a significant increase in battery impedance, which is detrimental to the battery's capacity and rate performance. The use of phosphate ester monomers can reduce the flammability of the electrolyte and improve the thermal stability of the gel electrolyte. Simultaneously, the phosphate ester polymers formed after the polymerization of phosphate ester monomers participate in the formation of the positive and negative electrode interface films. These polymer-formed interface films can, on the one hand, weaken the decomposition of LiBSB, and on the other hand, the polymers decompose on the electrode surface to form phosphate esters, which are beneficial to Li…+ Rapid conduction at the positive and negative electrode interface film ultimately reduces battery impedance.

[0029] In some embodiments of this application, the preparation method satisfies at least one of the following:

[0030] (a) The mass ratio of the phosphate ester compound and the crosslinking agent shown in Formula I is (85-70):(15-30);

[0031] (b) The initiator accounts for 0.02% to 0.1% of the total mass of the phosphate ester compound and crosslinking agent shown in Formula I;

[0032] (c) The additive in the electrolyte has a mass percentage of 0.05% to 5%;

[0033] (d) Total mass of electrolyte: The total mass of phosphate ester compounds and crosslinking agents shown in Formula I = (93-80):(7-20), and the sum of the first and second terms is 100.

[0034] In some embodiments of this application, at least one of the following is satisfied:

[0035] (i) The initiator includes at least one of azobisisobutyronitrile, benzoyl peroxide, diisopropyl peroxide dicarbonate, and N,N-dimethylaniline;

[0036] (ii) Crosslinking agents include polyethylene glycol dimethacrylate or carboxylic acid ester compounds; wherein:

[0037] The molecular formula of polyethylene glycol dimethacrylate is: C3H5C(O)(OCH2CH2). n OC(O)C3H5, where n = 1 to 10;

[0038] The structures of carboxylic acid ester compounds are shown in Formula III:

[0039]

[0040] In some embodiments of this application, the control parameters for polymerizing the mixture include: a temperature of 40°C to 80°C, and / or a time of 6h to 24h.

[0041] A third aspect of this application provides a battery comprising the gel polymer electrolyte described above, or the gel polymer electrolyte obtained by the preparation method described above.

[0042] The battery provided in this application includes the gel polymer electrolyte described above, or the gel polymer electrolyte obtained by the above preparation method, and has a high oxidation potential, low resistance, and good cycle performance.

[0043] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Detailed Implementation

[0044] The embodiments of the present invention are described in detail below, and are intended to explain the present invention, but should not be construed as limiting the present invention.

[0045] Commercial lithium-ion battery electrolytes primarily consist of conductive lithium salts (such as LiPF6), linear and cyclic carbonate solvents, and small amounts of functional additives. This is mainly because these electrolytes possess high conductivity, good aluminum foil passivation properties, a wide electrochemical window, and can form a chemically and electrochemically stable solid electrolyte film on the graphite anode surface. However, liquid electrolytes pose risks such as leakage, combustion, and internal short circuits, resulting in a low safety factor and a high likelihood of battery safety issues.

[0046] Gel polymer electrolytes utilize polymer networks to adsorb liquid electrolytes, addressing potential safety issues such as leakage and combustion associated with liquid electrolytes. They also inherit the excellent compatibility between liquid electrolytes and positive and negative electrode materials, making them a key area of ​​focus for industry and academia over the past three decades. However, currently used gel polymer electrolytes still face the challenge of low oxidation potential. Under high-voltage operating conditions, the battery's cycle performance deteriorates, severely limiting the market adoption of gel electrolytes in 4V-class batteries.

[0047] Therefore, a first aspect of the embodiments of this application provides a gel polymer electrolyte, comprising:

[0048] Polymer matrix;

[0049] Electrolyte adsorbed in polymer matrix;

[0050] The polymer matrix includes polymers formed by polymerizing phosphate ester compounds as shown in Formula I:

[0051]

[0052] In Formula I, R1 and R2 are substituted or unsubstituted alkyl groups of C1 to C4, respectively, and the substituents are selected from at least one of halogens and cyano groups;

[0053] The electrolyte includes carbonate solvents and additives;

[0054] The additives include lithium disalicylate borate as shown in Formula II:

[0055]

[0056] The gel polymer electrolyte provided in this application includes a polymer polymerized from phosphate ester compounds as monomers and a carbonate electrolyte. On one hand, the gel polymer electrolyte formed after polymerization of phosphate ester monomers has a higher oxidation potential, which can match high-voltage cathode materials. On the other hand, lithium bis(salicylate)borate (LiBSB) has good film-forming ability and can oxidize and decompose on the electrode surface to form a high-quality, high-voltage resistant interface film, thereby improving the oxidation potential of the carbonate electrolyte. Ultimately, through the synergistic effect of the polymer polymerized from phosphate ester monomers and LiBSB, the oxidation potential of the carbonate electrolyte can be improved, thus enhancing battery performance.

[0057] Carboxylic acid ester monomers are commonly used monomers for preparing gel electrolytes, but the polymers formed by the polymerization of carboxylic acid ester monomers have a low oxidation potential, which is a problem when compared with high voltage (>4.25V vs. Li / Li). + The compatibility of the cathode material is relatively poor. Compared with carboxylic acid ester monomers, phosphate ester polymers formed by the polymerization of phosphate ester monomers have a higher oxidation potential and better compatibility with high-voltage cathode materials. Moreover, the phosphate ester polymers formed after the polymerization of phosphate ester monomers can reduce the flammability of liquid carbonate electrolytes, greatly improve the thermal stability of gel electrolytes, reduce the risk of thermal runaway of batteries, and thus improve battery safety.

[0058] Taking traditional LiPF6 carbonate electrolyte as an example, the electrolyte has a low oxidation potential, and at high voltages (>4.25V vs. Li / Li), it exhibits a low oxidation potential. + When used in batteries, severe oxidative decomposition of the electrolyte leads to a sharp decline in battery performance. LiBSB, as an additive, can significantly increase the oxidation potential of LiPF6 carbonate electrolyte. This is mainly because LiBSB has excellent film-forming ability, forming substances containing both benzene rings and boron structures on the electrode surface, providing excellent protection for the electrode interface and greatly inhibiting the oxidative decomposition of the carbonate electrolyte. However, the decomposition of LiBSB leads to a decrease in the first-cycle efficiency of the battery and a significant increase in battery impedance, which is detrimental to the battery's capacity and rate performance. The use of phosphate ester monomers can reduce the flammability of the electrolyte and improve the thermal stability of the gel electrolyte. Simultaneously, the phosphate ester polymers formed after the polymerization of phosphate ester monomers participate in the formation of the positive and negative electrode interface films. These polymer-formed interface films can, on the one hand, weaken the decomposition of LiBSB, and on the other hand, the polymers decompose on the electrode surface to form phosphate esters, which are beneficial to Li… +Rapid conduction at the positive and negative electrode interface ultimately reduces battery impedance. The decomposition products of LiBSB at the positive and negative electrode interface are mainly substances containing benzene rings and boron structures. Meanwhile, the polymers formed by the polymerization of phosphate ester monomers at the positive and negative electrode interface mainly consist of phosphate-containing substances. These decomposition products all exhibit good stability during battery cycling, which can improve the stability of the positive and negative electrode interface film, thereby improving the cycle stability of the battery.

[0059] In the embodiments of this application, R1 and R2 are respectively substituted alkyl groups of C1 to C4 or unsubstituted alkyl groups of C1 to C4; the substituents in the substituted alkyl groups of C1 to C4 are selected from at least one of halogens and cyano groups. In specific examples, alkyl groups include methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, etc., and halogens include fluorine, chlorine, bromine, iodine, etc.

[0060] In some embodiments of this application, R1 and R2 are respectively substituted alkyl groups of C1 to C2 or unsubstituted alkyl groups of C1 to C2; the substituents in the substituted alkyl groups of C1 to C2 are selected from halogens and cyano groups.

[0061] In the embodiments of this application, in Formula I, R1 and R2 are substituted alkyl groups of C1 to C2 or unsubstituted alkyl groups of C1 to C2, respectively. The carbon chains of this type of phosphate ester compound are relatively short, and the movement between molecules is less restricted, which is beneficial to improving the migration speed of lithium ions and the overall ionic conductivity of the electrolyte.

[0062] In some embodiments of this application, the substituents in the substituted alkyl groups of C1 to C4 are fluorine.

[0063] In the embodiments of this application, in Formula I, R1 and R2 are substituted alkyl groups of C1 to C4, with fluorine as the substituent. The polymers formed by monomers of fluorinated alkyl phosphate esters contain CF bonds with high bond energies, which gives the fluoropolymers high chemical stability, enabling them to resist chemical corrosion during battery operation, thereby protecting the electrode surface and enhancing the stability of the interfacial film. Due to the high electrochemical stability of fluoropolymers, they are less prone to redox reactions during battery charging and discharging, which helps reduce electrolyte decomposition, thus forming a more stable interfacial film on the electrode surface. Furthermore, fluorine in the fluoropolymers has high electronegativity and strong electron-withdrawing ability, which helps to increase the oxidation potential of the electrolyte. Further, R1 and R2 are substituted alkyl groups of C1 to C2, with fluorine as the substituent.

[0064] In some embodiments of this application, the polymer matrix has a mass percentage content of 7% to 20% in the gel polymer electrolyte, and the electrolyte has a mass percentage content of 80% to 93% in the gel polymer electrolyte.

[0065] In this embodiment of the application, the contents of the polymer matrix and electrolyte in the gel polymer electrolyte system meet the above conditions, which is beneficial to obtaining higher conductivity and improving the electrochemical performance of the battery. In specific examples, the mass percentage of the polymer matrix in the gel polymer electrolyte is 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, etc., and the mass percentage of the electrolyte in the gel polymer electrolyte is 93%, 92%, 91%, 90%, 89%, 88%, 87%, 86%, 85%, 84%, 83%, 82%, 81%, 80%, etc.

[0066] In some embodiments of this application, the additive has a mass percentage content of 0.05% to 5% in the electrolyte.

[0067] In this embodiment, the additive content in the electrolyte meets the above conditions, which facilitates the synergistic effect with the polymer formed by the phosphate ester compound, increases the oxidation potential of the carbonate electrolyte, reduces resistance, and improves the electrochemical performance of the battery. Specifically, the mass percentage of the additive in the electrolyte is 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.5%, 2%, 2.5%, 3%, 4%, and 5%.

[0068] Furthermore, the additive's mass percentage in the electrolyte is 1% to 3%. This helps to increase the overall oxidation potential of the electrolyte, reduce resistance, and improve the battery's electrochemical performance. In specific examples, the additive's mass percentage in the electrolyte is 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, and 3%, etc.

[0069] In some embodiments of this application, the carbonate solvent includes at least one of ethylene carbonate, propylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate.

[0070] In this embodiment, the carbonate solvent provides a solubilizing environment for the electrolyte. This type of carbonate solvent has a low oxidation potential and is more prone to decomposition under high voltage. In this embodiment, the overall oxidation potential of the electrolyte is improved and the electrochemical performance of the battery is improved by the synergistic effect of the polymer formed by the polymerization of phosphate ester compounds as monomers and the additive lithium disalicylate borate.

[0071] In some embodiments of this application, the electrolyte further includes a lithium salt, which includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethyl)sulfonyl)imide, lithium bis(oxalate)borate, lithium difluorobis(oxalate)borate, lithium difluorobis(oxalate)phosphate, lithium tetrafluorooxalate phosphate, and lithium 4,5-dicyano-2-trifluoromethyl-imidazolium.

[0072] Furthermore, the lithium salt is at least one of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide. This type of lithium salt has high electrical conductivity.

[0073] Furthermore, the lithium salt concentration in the electrolyte is 1.0 mol / L to 1.5 mol / L.

[0074] The optimal concentration of commercial lithium-ion battery electrolytes is approximately 1.0 mol / L–1.5 mol / L. At this concentration, the electrolyte exhibits high conductivity, low viscosity, good wettability of the separator and electrode materials, and relatively low cost, which facilitates market promotion. Specific examples include lithium salt concentrations of 1.0 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, and 1.5 mol / L.

[0075] A second aspect of this application provides a method for preparing a gel polymer electrolyte, comprising:

[0076] A mixture of the phosphate ester compound shown in Formula I, an electrolyte, a crosslinking agent, and an initiator is obtained. The mixture is then subjected to polymerization treatment to obtain the above-mentioned gel polymer electrolyte.

[0077] The gel polymer electrolyte prepared in this application includes a polymer polymerized from phosphate ester compounds as monomers and a carbonate electrolyte. On one hand, the gel polymer electrolyte formed after polymerization of phosphate ester monomers has a higher oxidation potential, which can match high-voltage cathode materials. On the other hand, lithium bis(salicylate)borate (LiBSB) has good film-forming ability and can oxidize and decompose on the electrode surface to form a high-quality, high-voltage-resistant interface film, thereby improving the oxidation potential of the carbonate electrolyte. Finally, through the synergistic effect of the polymer polymerized from phosphate ester monomers and LiBSB, the oxidation potential of the carbonate electrolyte can be improved, thus improving battery performance.

[0078] Carboxylic acid ester monomers are commonly used monomers for preparing gel electrolytes, but the polymers formed by the polymerization of carboxylic acid ester monomers have a low oxidation potential, which is a problem when compared with high voltage (>4.25V vs. Li / Li). +The compatibility of the cathode material is relatively poor. Compared with carboxylic acid ester monomers, phosphate ester polymers formed by the polymerization of phosphate ester monomers have a higher oxidation potential and better compatibility with high-voltage cathode materials. Moreover, the phosphate ester polymers formed after the polymerization of phosphate ester monomers can reduce the flammability of liquid carbonate electrolytes, greatly improve the thermal stability of gel electrolytes, reduce the risk of thermal runaway of batteries, and thus improve battery safety.

[0079] Taking traditional LiPF6 carbonate electrolyte as an example, the electrolyte has a low oxidation potential, and at high voltages (>4.25V vs. Li / Li), it exhibits a low oxidation potential. + When used in batteries, severe oxidative decomposition of the electrolyte leads to a sharp decline in battery performance. LiBSB, as an additive, can significantly increase the oxidation potential of LiPF6 carbonate electrolyte. This is mainly because LiBSB has excellent film-forming ability, forming substances containing both benzene rings and boron structures on the electrode surface, providing excellent protection for the electrode interface and greatly inhibiting the oxidative decomposition of the carbonate electrolyte. However, the decomposition of LiBSB leads to a decrease in the first-cycle efficiency of the battery and a significant increase in battery impedance, which is detrimental to the battery's capacity and rate performance. The use of phosphate ester monomers can reduce the flammability of the electrolyte and improve the thermal stability of the gel electrolyte. Simultaneously, the phosphate ester polymers formed after the polymerization of phosphate ester monomers participate in the formation of the positive and negative electrode interface films. These polymer-formed interface films can, on the one hand, weaken the decomposition of LiBSB, and on the other hand, the polymers decompose on the electrode surface to form phosphate esters, which are beneficial to Li… + Rapid conduction at the positive and negative electrode interface film ultimately reduces battery impedance.

[0080] In some embodiments of this application, at least one of the following is satisfied:

[0081] (a) The mass ratio of the phosphate ester compound and the crosslinking agent shown in Formula I is (85-70):(15-30);

[0082] (b) The initiator accounts for 0.02% to 0.1% of the total mass of the phosphate ester compound and crosslinking agent shown in Formula I;

[0083] (c) The additive in the electrolyte has a mass percentage of 0.05% to 5%;

[0084] (d) Total mass of electrolyte: The total mass of phosphate ester compounds and crosslinking agents shown in Formula I = (93-80):(7-20), and the sum of the first and second terms is 100.

[0085] In the embodiments of this application, the mass ratio of the phosphate ester compound shown in Formula I to the crosslinking agent is (85-70):(15-30), and the sum of the first and second terms is 100. This facilitates the formation of a gel electrolyte system, which, together with the additives, increases the oxidation potential of the electrolyte and improves the electrochemical performance of the battery. In specific examples, the mass ratio of the phosphate ester compound shown in Formula I to the crosslinking agent is 85:15, 84:16, 83:17, 82:18, 81:19, 80:20, 79:21, 78:22, 77:23, 76:24, 75:25, 74:26, 73:27, 72:28, 71:29, 70:30, etc.

[0086] In this embodiment, the initiator accounts for 0.02% to 0.1% of the total mass of the phosphate ester compound and the crosslinking agent shown in Formula I. Specifically, the total mass is the sum of the masses of the phosphate ester compound and the crosslinking agent shown in Formula I, and the initiator's mass percentage is 0.02% to 0.1% based on this total mass. In specific examples, the initiator's mass percentage is 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, etc. The initiator is used to initiate the polymerization process between the monomer molecules of the phosphate ester compound, forming a polymer. Further, the initiator's mass percentage is 0.05%.

[0087] In this embodiment, the additive content in the electrolyte meets the above conditions, which facilitates the synergistic effect with the polymer formed by the phosphate ester compound, increases the oxidation potential of the carbonate electrolyte, reduces resistance, and improves the electrochemical performance of the battery. Specifically, the mass percentage of the additive in the electrolyte is 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.5%, 2%, 2.5%, 3%, 4%, and 5%.

[0088] Furthermore, the additive's mass percentage in the electrolyte is 1% to 3%. This helps to increase the overall oxidation potential of the electrolyte, reduce resistance, and improve the battery's electrochemical performance. In specific examples, the additive's mass percentage in the electrolyte is 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, and 3%, etc.

[0089] In this embodiment, the total mass of the electrolyte is: the total mass of the phosphate ester compound shown in Formula I and the crosslinking agent = (93-80):(7-20), and the sum of the first and second terms is 100. That is, the mass of the electrolyte is taken as the total mass A, and the sum of the mass of the phosphate ester compound shown in Formula I and the mass of the crosslinking agent is taken as the total mass B. The ratio of A to B is (93-80):(7-20), and the sum of the first term A and the second term B is 100. The ratio of the total mass of the electrolyte and the total mass of the phosphate ester compound shown in Formula I to the total mass of the crosslinking agent satisfies the above conditions, which is conducive to the formation of polymers, to obtaining higher conductivity, and to improving the electrochemical performance of the battery. In specific examples, the total mass of the electrolyte is calculated as follows: the total mass of the phosphate ester compound and crosslinking agent shown in Formula I is 93:7, 92:8, 91:9, 90:10, 89:11, 88:12, 87:13, 86:14, 85:15, 84:16, 83:17, 82:18, 81:19, 80:20, etc. Here, the total mass of the electrolyte refers to the sum of the masses of conventional electrolyte components, including solvents, additives, and lithium salts. Since the amount of initiator added is relatively small, in actual operation, the sum of the masses of the phosphate ester compound and the crosslinking agent shown in Formula I can be directly used as the total mass B and compared with the total mass A of the electrolyte.

[0090] In some embodiments of this application, the preparation method satisfies at least one of the following:

[0091] (i) The initiator includes at least one of azobisisobutyronitrile, benzoyl peroxide, diisopropyl peroxide dicarbonate, and N,N-dimethylaniline;

[0092] (ii) Crosslinking agents include polyethylene glycol dimethacrylate or carboxylic acid ester compounds; wherein:

[0093] The molecular formula of polyethylene glycol dimethacrylate is: C3H5C(O)(OCH2CH2). n OC(O)C3H5, where n = 1 to 10;

[0094] The structures of carboxylic acid ester compounds are shown in Formula III:

[0095]

[0096] In some embodiments of this application, the control parameters for polymerizing the mixture include: a temperature of 40°C to 80°C, and / or a time of 6h to 24h.

[0097] In this embodiment, phosphate ester compounds are used as monomers to polymerize and form polymers. Controlling the temperature and time during the polymerization process to meet the above conditions is beneficial for effective polymerization and avoids the decomposition of substances such as lithium salts.

[0098] In specific examples, the controlled temperatures are 40℃, 41℃, 42℃, 43℃, 44℃, 45℃, 46℃, 47℃, 48℃, 49℃, 50℃, 51℃, 52℃, 53℃, 54℃, 55℃, 56℃, 57℃, 58℃, 59℃, 60℃, 61℃, 62℃, 63℃, 64℃, 65℃, 66℃, 67℃, 68℃, 69℃, 70℃, 71℃, 72℃, 73℃, 74℃, 75℃, 76℃, 77℃, 78℃, 79℃, and 80℃.

[0099] In specific examples, the control time is 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h, 24h, etc.

[0100] A third aspect of this application provides a semi-solid-state battery comprising the gel polymer electrolyte described above, or the gel polymer electrolyte obtained by the preparation method described above.

[0101] The battery provided in this application embodiment includes the gel polymer electrolyte described above, or the gel polymer electrolyte obtained by the above preparation method, and has a high oxidation potential, low resistance, and good cycle performance.

[0102] Furthermore, the semi-solid battery is a semi-solid lithium-ion battery.

[0103] In some embodiments of this application, the battery further includes a positive electrode material and a negative electrode material.

[0104] Furthermore, the cathode materials include lithium manganese oxide (LiMn2O4), lithium cobalt oxide (LiCoO2), and lithium nickel manganese oxide (LiNi). x Co y Mn z At least one of O2, x+y+z=1. Further, the negative electrode material includes at least one of graphite, silicon-carbon, silicon-oxygen and their composites.

[0105] A fourth aspect of this application provides a method for preparing a battery, comprising the steps of:

[0106] The mixture obtained by mixing the phosphate ester compound shown in Formula I, the electrolyte, the crosslinking agent, and the initiator is the gel polymer electrolyte precursor solution.

[0107] The mixture is injected into the battery cell, vacuum sealed, left to stand at room temperature, and then polymerized to obtain a semi-solid battery.

[0108] In some embodiments of this application, the preparation method satisfies at least one of the following:

[0109] The standing time at room temperature is 12h to 36h;

[0110] The polymerization temperature is 40℃~80℃;

[0111] The polymerization process takes 6 to 24 hours.

[0112] It should be noted that the features and advantages described above for the preparation methods of the gel polymer electrolyte of the first and second aspects of this application are also applicable to the preparation methods of the battery of the third and fourth aspects of this application, and will not be repeated here.

[0113] The present invention will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the invention in any way. The reagents used in the embodiments are all from Aladdin Biochemical Technology Co., Ltd.

[0114] Gel polymer electrolyte

[0115] Example 1

[0116] In a glove box filled with high-purity argon (H2O, O2 < 1 ppm), ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed at a mass ratio of EC:EMC = 3:7. After thorough mixing, lithium hexafluorophosphate (LiPF6) was added to obtain the basic electrolyte, named LiPF6-EC / EMC, with a LiPF6 concentration of 1 mol / L (1 M).

[0117] Subsequently, dimethyl vinyl phosphate, pentaerythritol tetraacrylate (PETEA), azobisisobutyronitrile (AIBN), 1M LiPF6-EC / EMC, and LiBSB were mixed in a mass ratio of 8:2:0.05:88.2:1.8, and the mixture was homogeneous to obtain a gel polymer electrolyte precursor solution.

[0118] The gel polymer electrolyte precursor solution was vacuum sealed and placed in a constant temperature oven at 60°C for 12 hours to obtain the gel polymer electrolyte, which was named GPE1.

[0119] Examples 2-27

[0120] The preparation methods of the gel polymer electrolytes provided in Examples 2-27 are the same as those in Example 1, with the differences shown in Table 1. The obtained gel polymer electrolytes are named GPE2, GPE3, GPE4, GPE5, GPE6, GPE7, GPE8, GPE9, GPE10, GPE11, GPE12, GPE13, GPE14, GPE15, GPE16, GPE17, GPE18, GPE19, GPE20, GPE21, GPE22, GPE23, GPE24, GPE25, GPE26, and GPE27, respectively.

[0121] Comparative Example 1

[0122] In a glove box filled with high-purity argon (H2O, O2 < 1 ppm), EC and EMC were mixed at a mass ratio of EC:EMC = 3:7. After thorough mixing, a measured amount of LiPF6 was added, with a concentration of 1 mol / L (1 M). After the lithium salt was completely dissolved, 2 wt% of the total electrolyte amount of LiBSB was added. The resulting electrolyte was named D1.

[0123] Comparative Examples 2-5

[0124] The preparation methods of the gel polymer electrolytes provided in Comparative Examples 2-5 were the same as those in Example 1, with the differences shown in Table 1. The obtained electrolytes were named D2, D3, D4, and D5, respectively.

[0125] Table 1. Preparation parameters for Examples 1-27 and Comparative Examples 1-5

[0126]

[0127] Where A / B represents the mass ratio, where A is the total mass of the electrolyte, and B is the sum of the mass of the phosphate ester compound shown in Formula I and the mass of the crosslinking agent.

[0128] Performance testing

[0129] I. Testing Method:

[0130] 1. Conductivity test: The conductivity of the gel polymer electrolytes in the examples and comparative examples was tested using a conductivity electrode (Lei Ci, DJS-1C type platinum black bright conductivity electrode).

[0131] 2. Oxidation Potential Testing: The oxidation potential of the electrolyte was tested using linear sweep voltammetry. A three-electrode system was assembled with platinum (Pt) as the working electrode and lithium metal as the counter and reference electrodes; the working area of ​​the Pt electrode was 0.0314 cm². 2 During the test, the scan voltage range was from open-circuit voltage to 6.5V vs. Li / Li. +The scan rate was 1 mV / s. The potential value corresponding to a current density of 0.05 mA on the polarization curve was taken as the oxidation potential of the electrolyte.

[0132] II. Test Results:

[0133] The results of testing the electrolytes provided in Examples 1-27 and Comparative Examples 1-5 are shown in Table 2.

[0134] Table 2 Electrolyte performance test results

[0135]

[0136] The test results above show that the synergistic effect of the polymer synthesized from phosphate ester monomers and LiBSB can increase the oxidation potential of carbonate electrolyte.

[0137]

Battery

[0138] Preparation of the positive electrode: The lithium nickel cobalt manganese oxide ternary material LiNi 0.8 Co 0.1 Mn 0.1 O2, conductive agent Super P, carbon nanotubes, and binder polyvinylidene fluoride (PVDF) were mixed with N,N-dimethylpyrrolidone in a mass ratio of 96.3:2:0.5:1.2 to prepare a uniform slurry. The slurry was uniformly coated onto an aluminum foil current collector, dried at 85°C, and then rolled. The rolled electrode was then trimmed, cut, and slit. After slitting, it was vacuum dried at 85°C for 5 hours, and then the tabs were welded to obtain the positive electrode sheet for a lithium-ion battery.

[0139] Preparation of the negative electrode sheet: Graphite material, conductive agent Super P, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) are mixed with water at a mass ratio of 95:1.5:2.0:1.5 to form a uniform slurry. The slurry is evenly coated onto a copper foil current collector, dried at 85°C, and then rolled. The rolled electrode sheet is then trimmed, cut, and slit. After slitting, it is vacuum dried at 85°C for 5 hours, and then tabs are welded to obtain the lithium-ion battery negative electrode sheet.

[0140] Diaphragm: Polyethylene (PE) diaphragm.

[0141] The prepared positive electrode sheet, separator, and negative electrode sheet are stacked neatly in sequence and wound to obtain a dry cell. The dry cell is then placed in an aluminum-plastic film outer packaging. Vacuum drying at 85℃ for 48 hours yields the battery cell.

[0142] The gel polymer electrolyte precursor solution or electrolyte of Examples 1-27 and Comparative Examples 1-5 was injected into the cell, vacuum sealed, and placed at room temperature for 12-36 hours to allow the electrode plates, separator and gel polymer electrolyte precursor solution to be fully wetted; then the cell was heated at 60°C for 12 hours. After polymerization, the cell was subjected to formation, degassing and other processes in sequence to finally obtain the shaped semi-solid cell.

[0143] The batteries corresponding to Examples 1-27 and Comparative Examples 1-5 are named BAT1, BAT2, BAT3, BAT4, BAT5, BAT6, BAT7, BAT8, BAT9, BAT10, BAT11, BAT12, BAT13, BAT14, BAT15, BAT16, BAT17, BAT18, BAT19, BAT20, BAT21, BAT22, BAT23, BAT24, BAT25, BAT26, BAT27, D1#, D2#, D3#, D4#, and D5#, respectively.

[0144] Performance testing

[0145] I. Testing Method:

[0146] 1. First-week efficiency: During the formation process, the battery is first charged at 0.1C to 4.4V, and then charged at constant voltage until the cutoff current is 0.05C. The capacity of the battery during the charging process is recorded as C0. Then, it is discharged at 0.1C to 2.75V. The capacity of the battery during the discharge process is recorded as D0. First-week efficiency = D0 / C0*100%.

[0147] 2. Capacity at 1C: After formation, the battery is charged and discharged at a rate of 0.1 / 01C for 5 weeks, and then charged and discharged at 1 / 1C for 5 weeks. The discharge capacity at 1 / 1C in the 5th week is the capacity at 1C.

[0148] 3. DC polarization internal resistance (DCR): The battery is first charged at 1.0C (I 1.0C Constant current charging for half an hour, then at 5.0C (I 5.0C Charge the battery at a rate of 5.0C for 10 seconds and record the voltage change ΔV before and after polarization. DCR = ΔV / I 5.0C .

[0149] 4. Capacity retention after 500 cycles at 25℃: C / LiNi 0.8 CoMn 0.1 Mn 0.1The O2 battery was charged and discharged using a constant current charge-constant voltage charge-constant current discharge (CC-CV) method. The battery's charge and discharge voltage range was 2.75V-4.4V, and the test temperature was 25℃. First, it was charged at a constant current of 1.0C to 4.4V, then charged at a constant voltage to the cutoff current of 0.05C, and then discharged at a constant current of 1.0C to 2.75V. The discharge capacity was recorded as C1. This charge and discharge cycle was repeated for 500 cycles to obtain the discharge capacity on the 500th cycle, denoted as C. 500 The capacity retention rate of a battery after 500 cycles = C 500 / C1*100%.

[0150] II. Test Results:

[0151] The performance of the provided battery samples was tested, and the test results are shown in Table 3.

[0152] Table 3 Performance test results of battery samples

[0153]

[0154] The test results above show that the synergistic effect of the polymer synthesized from phosphate ester monomers and LiBSB can increase the oxidation potential of carbonate electrolyte, reduce internal resistance, and improve the cycle performance of the battery.

[0155] A comparison of Examples 1-7 with Comparative Example 5 shows that introducing LiBSB into the electrolyte can increase the oxidation potential of the phosphate ester-based gel electrolyte, reduce the DC polarization internal resistance of the battery, and ultimately improve the cycling performance of the gel electrolyte under high voltage.

[0156] A comparison of Examples 1-7 with Comparative Example 1 shows that, compared with methyl methacrylate, phosphate-based materials have a higher oxidation potential, and the batteries exhibit better cycle performance.

[0157] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0158] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A gel polymer electrolyte, characterized in that, include: Polymer matrix; Electrolyte located in the polymer matrix; The polymer matrix comprises a polymer formed by polymerizing phosphate ester compounds as shown in Formula I: In Formula I, R1 and R2 are either substituted alkyl groups of C1 to C4 or unsubstituted alkyl groups of C1 to C4, respectively; the substituents in the substituted alkyl groups of C1 to C4 are selected from at least one of halogens and cyano groups; The electrolyte includes a carbonate solvent and additives; The additive includes lithium disalicylic acid borate as shown in Formula II:

2. The gel polymer electrolyte according to claim 1, characterized in that, R1 and R2 are either substituted alkyl groups of C1 to C2 or unsubstituted alkyl groups of C1 to C2, respectively; the substituents in the substituted alkyl groups of C1 to C2 are selected from halogens and cyano groups.

3. The gel polymer electrolyte according to claim 1, characterized in that, The substituted alkyl groups in the C1 to C4 structures are fluorine substituents.

4. The gel polymer electrolyte according to any one of claims 1 to 3, characterized in that, The polymer matrix in the gel polymer electrolyte has a mass percentage content of 7% to 20%, and the electrolyte has a mass percentage content of 80% to 93%.

5. The gel polymer electrolyte according to claim 1, characterized in that, The additive has a mass percentage of 0.05% to 5% in the electrolyte.

6. The gel polymer electrolyte according to claim 1, characterized in that, The carbonate solvent includes at least one of ethylene carbonate, propylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate, dimethyl carbonate, methyl ethyl carbonate, and diethyl carbonate. And / or, the electrolyte further includes a lithium salt, the lithium salt comprising at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethyl)sulfonylimide, lithium bis(oxalate)borate, lithium difluorobis(oxalate)borate, lithium difluorobis(oxalate)phosphate, lithium tetrafluorooxalate phosphate, and lithium 4,5-dicyano-2-trifluoromethyl-imidazolium.

7. A method for preparing a gel polymer electrolyte, characterized in that, include: A mixture is prepared by mixing raw materials including a phosphate ester compound of Formula I, a crosslinking agent, an initiator, and an electrolyte. The mixture is then subjected to polymerization treatment to obtain the gel polymer electrolyte according to any one of claims 1 to 6.

8. The preparation method according to claim 7, characterized in that, Meet at least one of the following: (a) The mass ratio of the phosphate ester compound shown in Formula I to the crosslinking agent is (85-70):(15-30); (b) The initiator comprises 0.02% to 0.1% by mass of the total mass of the phosphate ester compound shown in Formula I and the crosslinking agent; (c) The additive in the electrolyte has a mass percentage of 0.05% to 5%; (d) The total mass of the electrolyte: the total mass of the phosphate ester compound shown in Formula I and the crosslinking agent = (93-80):(7-20), and the sum of the first and second terms is 100.

9. The preparation method according to claim 7 or 8, characterized in that, (i) The initiator includes at least one of azobisisobutyronitrile, benzoyl peroxide, diisopropyl peroxide dicarbonate and N,N-dimethylaniline; (ii) The crosslinking agent comprises polyethylene glycol dimethacrylate or a carboxylic acid ester compound; wherein: The molecular formula of the polyethylene glycol dimethacrylate is: C3H5C(O)(OCH2CH2). n OC(O)C3H5, where n = 1 to 10; The structure of the carboxylic acid ester compound is shown in Formula III:

10. The preparation method according to claim 7, characterized in that, In the polymerization treatment of the mixture, the control parameters include: temperature of 40℃~80℃, and / or time of 6h~24h.

11. A battery, characterized in that, It includes the gel polymer electrolyte according to any one of claims 1 to 6, or the gel polymer electrolyte obtained by the preparation method according to any one of claims 7 to 10.

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