Battery, method for manufacturing the same, and electric device

Abstract

The application belongs to the technical field of batteries, and particularly relates to a battery, a preparation method of the battery and an electric device. The battery comprises: an outer package, which defines an accommodating space inside; and an electrode roll, which comprises a positive electrode sheet, a negative electrode sheet, a separator and a gel-state electrolyte, and is arranged in the accommodating space; wherein the separator is arranged between the adjacent positive electrode sheet and negative electrode sheet, and the positive electrode sheet, the negative electrode sheet and the separator are impregnated with the gel-state electrolyte; and a first electrolyte, which is located in a gap between the outer package and the electrode roll. The first electrolyte in the battery can enter the inside of the electrode roll to supplement the electrolyte consumption in the gel-state electrolyte, thereby effectively prolonging the cycle life of the battery.

Description

Technical Field

[0001] This application relates to the field of battery technology, specifically to batteries, their preparation methods, and electrical devices. Background Technology

[0002] In recent years, one of the development directions for batteries has been to increase the capacity of individual cells. However, large-capacity batteries also bring higher safety risks. Using gel electrolytes instead of flowing liquid electrolytes is one way to reduce these safety risks. A common method for preparing gel electrolytes is to add polymer monomers and initiators to a conventional electrolyte, and then initiate monomer polymerization under conditions such as heating and ultraviolet light irradiation to obtain a non-flowing gel electrolyte. For batteries with opaque outer packaging, thermal initiation is the most suitable polymerization method. However, during heat conduction, the outer side of the battery heats up first, and then the heat is conducted to the inside of the battery. This leads to uneven battery temperature; the electrolyte on the outer side polymerizes and solidifies first, while the electrolyte on the inside solidifies later. The resulting gel electrolyte inside the battery is unevenly solidified, and there is no electrolyte to replenish the gel electrolyte after long-term cycling, so the long-term cycle life of the battery still cannot meet the requirements. Therefore, the relevant technologies for gel electrolyte batteries still need improvement. Summary of the Invention

[0003] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, this invention proposes a battery, its preparation method, and an electrical device thereof. The gap between the electrode roll and the outer packaging contains a first electrolyte in a liquid state, while the interior of the electrode roll contains a gel-state electrolyte, exhibiting good safety and a long cycle life.

[0004] A first aspect of this application provides a battery. According to an embodiment of this application, the battery includes: an outer packaging, the inner part of which defines a receiving space; an electrode roll, the electrode roll including a positive electrode, a negative electrode, a separator, and a gel electrolyte, disposed within the receiving space; wherein the separator is disposed between adjacent positive and negative electrode sheets, and the positive electrode, the negative electrode, and the separator are impregnated with the gel electrolyte; and a first electrolyte, the first electrolyte being located in the gap between the outer packaging and the electrode roll. The use of a gel electrolyte inside the electrode roll effectively improves battery safety, while the presence of a liquid first electrolyte in the gap between the electrode roll and the outer packaging allows for replenishment of the gel electrolyte inside the electrode roll during charge-discharge cycles, thereby effectively extending the battery's cycle life.

[0005] According to embodiments of this application, the battery satisfies at least one of the following conditions:

[0006] Based on the total mass of the battery, the mass percentage of the first electrolyte is 1wt%~6wt%;

[0007] Based on the total mass of the first electrolyte and the gel electrolyte, the mass percentage of the first electrolyte is 5wt% to 30wt%.

[0008] According to an embodiment of this application, the gel electrolyte comprises a polymer backbone and a dispersion medium, wherein the dispersion medium is filled in the polymer backbone and the dispersion medium comprises a second electrolyte.

[0009] According to embodiments of this application, the polymer backbone in the gel electrolyte has a mass percentage of 0.5wt% to 5wt%, and / or the polymer backbone includes at least one of polyacrylate, polyacrylonitrile, polyethylene oxide, polymethyl methacrylate, and polyvinylidene fluoride.

[0010] According to embodiments of this application, the first electrolyte and the second electrolyte each independently include an organic solvent and an electrolyte salt; the solvent includes at least one of ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and propylene carbonate; the electrolyte salt includes at least one of lithium hexafluorophosphate, lithium difluorosulfonylimide, lithium difluorooxalate borate, and lithium difluorophosphate.

[0011] According to an embodiment of this application, in a fresh battery, there is no lithium plating on the surface of the negative electrode.

[0012] According to embodiments of this application, the positive electrode comprises lithium iron phosphate or lithium manganese iron phosphate; and / or, the negative electrode comprises graphite.

[0013] A second aspect of this application provides a method for manufacturing a battery. According to an embodiment of this application, the method includes: forming a positive electrode, a negative electrode, and a separator into an electrode roll; assembling the electrode roll into an outer packaging; injecting an electrolyte into the outer packaging; forming a first battery cell; injecting a supplementary electrolyte, a monomer, and an initiator into the first battery cell; allowing it to stand; forming a gel-state electrolyte inside the electrode roll of the second battery cell; and having a liquid electrolyte in the gap between the electrode roll and the outer packaging, thus obtaining a battery. The method of this application allows the electrolyte inside the electrode roll to solidify into a gel-state electrolyte, while the electrolyte in the gap between the electrode roll and the outer packaging remains liquid. The use of a gel-state electrolyte inside the electrode roll in the resulting battery effectively improves battery safety. The presence of a liquid first electrolyte in the gap between the electrode roll and the outer packaging allows for replenishment of the gel-state electrolyte inside the electrode roll during charge-discharge cycles, thereby effectively extending the battery's cycle life.

[0014] According to an embodiment of this application, forming a gel-like electrolyte inside the electrode roll of the second cell, and having a liquid electrolyte in the gap between the electrode roll and the outer packaging, includes: performing pulse charge-discharge cycles on the second cell with a pulsed current for a predetermined time. Thus, the pulse charge-discharge cycle can induce monomer polymerization in the electrolyte by self-heating inside the electrode roll, while the temperature outside the electrode roll is lower than the temperature inside the electrode roll due to heat conduction. The electrolyte in the gap between the electrode roll and the outer packaging remains in a liquid state, resulting in a battery with better safety and a longer cycle life.

[0015] According to embodiments of this application, the pulse charge-discharge cycle includes multiple charge-discharge cycles, one of which includes: charging with a first current for a first time, resting for a second time, discharging with a second current for a third time, and resting for a fourth time. This effectively induces monomer polymerization within the electrode roll to form a gel-like electrolyte, while maintaining the electrolyte in the gap between the electrode roll and the outer packaging in a liquid state, and also avoids lithium plating on the negative electrode.

[0016] According to embodiments of this application, the above method satisfies at least one of the following conditions:

[0017] The charging rate of the first current is 2C~6C;

[0018] The first time interval is 10s to 60s;

[0019] The second time is 10s~30s;

[0020] The discharge rate of the second current is 2C~6C;

[0021] The third time is 10s~60s;

[0022] The fourth time period is 10s~30s;

[0023] The scheduled time is 2 hours to 24 hours;

[0024] The ambient temperature for the pulse charge-discharge cycle is between 20°C and 50°C.

[0025] According to an embodiment of this application, during the pulse charge-discharge cycle, the temperature of the electrode roll is higher than the temperature at the gap between the electrode roll and the outer packaging.

[0026] According to embodiments of this application, the above method satisfies at least one of the following conditions:

[0027] Based on the total mass of the electrolyte and the supplementary electrolyte, the mass percentage of the monomer is 0.5 wt% to 5 wt%.

[0028] The amount of the initiator added is 1 wt% to 5 wt% of the total mass of the monomer;

[0029] The initiator includes at least one of dimethyl azobisisobutyrate, azobisisobutyronitrile, and azobisisoheptanenitrile;

[0030] The monomers include at least one of acrylate, acrylonitrile, ethylene oxide, methyl methacrylate, and vinylidene fluoride.

[0031] A third aspect of this application provides an electrical device. According to an embodiment of this application, the electrical device includes the battery described above. This electrical device has a long service life. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the structure of a battery according to an embodiment of this application.

[0033] Figure 2 This is a flowchart of a method for preparing a battery according to an embodiment of this application. Detailed Implementation

[0034] The embodiments of the present invention are described in detail below. These embodiments are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0035] This application is based on the inventor's discoveries and understanding of the following facts and problems:

[0036] During long-term charge-discharge cycles, the electrolyte is gradually consumed. For batteries using gel electrolytes, if liquid electrolyte is present on the outside of the electrode roll, it can be absorbed into the electrode roll after the gel electrolyte is consumed, replenishing the electrolyte and extending the battery's cycle life. However, in gel electrolyte batteries formed through thermosetting, the liquid electrolyte on the outside solidifies preferentially, leaving no liquid electrolyte on the outside. This results in a high degree of solidification on the outside of the electrode roll and a low degree of solidification on the inside. Furthermore, the external liquid electrolyte cannot enter the electrode roll, preventing replenishment of the gel electrolyte inside the electrode roll, leading to a reduced battery cycle life. To address this problem, the inventors of this application propose a battery with a novel gel electrolyte, which can effectively extend the battery's cycle life.

[0037] A first aspect of this application provides a battery. According to an embodiment of this application, referring to... Figure 1The battery includes: an outer packaging 10, which defines an internal receiving space; an electrode roll 20, which includes a positive electrode, a negative electrode, a separator, and a gel electrolyte, and is disposed within the receiving space; wherein the separator is disposed between adjacent positive and negative electrodes, and the positive electrode, the negative electrode, and the separator are impregnated with the gel electrolyte; and a first electrolyte 30, which is located in the gap between the outer packaging 10 and the electrode roll 20. The use of a gel electrolyte inside the electrode roll effectively improves battery safety, while the presence of a liquid first electrolyte in the gap between the electrode roll and the outer packaging allows for replenishment of the gel electrolyte inside the electrode roll during charge-discharge cycles, thereby effectively extending the battery's cycle life.

[0038] According to embodiments of this application, based on the total mass of the battery, the mass percentage of the first electrolyte is 1wt% to 6wt%, specifically 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, or any two of these ranges. Within this range, there is sufficient gel electrolyte to meet safety requirements, while the first electrolyte can effectively replenish the gel electrolyte, thereby extending the battery's cycle life.

[0039] In this paper, based on the total mass of the battery, the mass ratio of the first electrolyte can be detected by the following method: weigh the total mass of the battery, then disassemble the battery, take out the first electrolyte and weigh its mass, and then calculate the mass ratio of the first electrolyte in the total mass of the battery.

[0040] According to embodiments of this application, based on the total mass of the first electrolyte and the gel electrolyte, the mass percentage of the first electrolyte is 5wt% to 30wt%, specifically such as 5wt%, 8wt%, 10wt%, 12wt%, 15wt%, 18wt%, 20wt%, 22wt%, 25wt%, 28wt%, 30wt%, or any range between two of these. Within the above range, the gel electrolyte has a higher mass, which can maintain the battery cycle life. By adding 5wt% to 30wt% of the first electrolyte, it can be absorbed into the gel electrolyte within the electrode roll after long-term charging cycles, replenishing the gel electrolyte with sufficient electrolyte, thereby effectively improving the battery cycle life.

[0041] According to embodiments of this application, the gel electrolyte comprises a polymer backbone and a dispersion medium, wherein the dispersion medium is filled in the polymer backbone and comprises a second electrolyte. Therefore, the gel electrolyte exhibits superior ionic conductivity, mechanical properties, thermal stability, and interfacial compatibility, thereby improving the overall performance of the battery.

[0042] According to embodiments of this application, the polymer backbone in the gel electrolyte comprises 0.5wt% to 5wt% by mass, specifically 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt%, or any range between two of these. Within the above range, the gel electrolyte has a high proportion of dispersion medium, continuous ion migration channels, and high conductivity; simultaneously, it maintains close contact with the electrode, resulting in low interfacial impedance, thereby improving the overall performance of the battery.

[0043] According to embodiments of this application, the polymer backbone includes at least one selected from polyacrylate, polyacrylonitrile, polyethylene oxide, polymethyl methacrylate, and polyvinylidene fluoride. Therefore, the materials are widely available, have low cost, and the polymerization temperature is suitable for easy curing.

[0044] According to embodiments of this application, the first electrolyte and the second electrolyte each independently include an organic solvent and an electrolyte salt; wherein, the solvent includes at least one of ethylene carbonate (EC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and propylene carbonate (PC); and the electrolyte salt includes at least one of lithium hexafluorophosphate, lithium difluorosulfonylimide, lithium difluorooxalate borate, and lithium difluorophosphate.

[0045] According to an embodiment of this application, in a fresh battery, there is no lithium plating on the surface of the negative electrode. Therefore, the safety performance of the battery can be further improved.

[0046] In this article, "fresh battery" refers to a battery that has been prepared but not yet tested or used, or a battery that has been prepared but has been tested or has undergone capacity testing. For example, fresh batteries include, but are not limited to, batteries prepared in-house, and batteries purchased directly but not yet used.

[0047] In this article, lithium plating on the surface of the negative electrode can be detected by the following methods: After fully charging the battery and disassembling it, a normal battery without lithium plating will have a golden-yellow negative electrode. If lithium plating is present on the negative electrode surface, gray spots will be visible to the naked eye. Additionally, scanning electron microscopy (SEM) can reveal substances with morphologies different from graphite particles.

[0048] According to the embodiments of this application, it can be understood that there is no particular limitation on the specific type of battery, which can be a rechargeable battery; the shape of the battery can be a cylindrical battery, a square battery, or other arbitrary shaped batteries, and according to the outer packaging, the battery can be a hard-shell battery, a soft-pack battery, etc.

[0049] According to embodiments of this application, the positive electrode, negative electrode, and separator can be formed into an electrode roll by a winding or stacking process, wherein the positive electrode and negative electrode are alternately stacked, and the separator is disposed between adjacent positive and negative electrode sheets.

[0050] In some embodiments, the positive electrode sheet may include a positive current collector and a positive electrode material layer disposed on at least one side of the positive current collector. In some embodiments, the positive electrode material layer may include a positive electrode binder, a positive electrode conductive agent, and a positive electrode active material, and may also include additives with specific functions and effects, such as thickeners, lithium supplementers, sodium supplementers, film-forming additives, flame retardants, high-temperature / low-temperature stabilizers, etc., as needed.

[0051] In some embodiments, the positive current collector can be a metal current collector or a composite current collector. For example, metal current collectors include, but are not limited to, aluminum foil current collectors; composite current collectors may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. Composite current collectors can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0052] As an example, positive electrode active materials may include lithium nickel cobalt manganese oxide (including but not limited to NCM811, NCM613, NCM523, etc.), lithium cobalt oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium manganese oxide, lithium nickel manganese oxide, lithium-rich manganese-based materials, or positive electrode active materials commonly used in the art. Specifically, positive electrode active materials may include, but are not limited to, LiFe x Mn 1-x PO4, LiFePO4, LiCoO2, LiMn2O4, LiNi x Co y Mn z O2 (x+y+z=1, 0≤x≤1, 0≤y≤1, 0≤z≤1), LiNi x Co y Al z O2 (x+y+z=1, 0≤x≤1, 0≤y≤1, 0≤z≤1). As an example, positive electrode active materials include lithium iron phosphate or lithium manganese iron phosphate.

[0053] As an example, the positive electrode binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), hydrogenated nitrile butadiene rubber (HNBR), ethylene-tetrafluoroethylene-propylene terpolymer, ethylene-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0054] As an example, the positive electrode conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0055] According to embodiments of this application, the negative electrode sheet may include a negative electrode current collector and a negative electrode material layer disposed on at least one side of the negative electrode current collector. In some embodiments, the negative electrode material layer may include a negative electrode binder, a negative electrode conductive agent, and a negative electrode active material. Additives with specific functions and effects, such as thickeners, lithium supplements, sodium supplements, film-forming additives, flame retardants, and high / low temperature stabilizers, may also be added as needed.

[0056] According to embodiments of this application, the negative electrode current collector can be a metal current collector or a composite current collector. For example, metal current collectors include, but are not limited to, copper foil current collectors; composite current collectors may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. Composite current collectors can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0057] According to embodiments of this application, the negative electrode active material may include graphite, hard carbon, soft carbon, mesophase microspheres, silicon-carbon materials, silicon-oxygen materials, silicon, lithium titanate, tin-based materials, etc. As an example, the negative electrode active material includes graphite.

[0058] According to embodiments of this application, the negative electrode conductive agent may include, but is not limited to, at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0059] According to embodiments of this application, the negative electrode binder may include, but is not limited to, at least one of hydrogenated nitrile rubber (HNBR), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0060] In some embodiments, the positive electrode comprises lithium iron phosphate or lithium manganese iron phosphate; and / or, the negative electrode comprises graphite.

[0061] In some embodiments, the separator may be a separator known in the art that can be used in batteries and is stable to the electrolyte used, such as a polyethylene separator, a polypropylene separator, a polyethylene / polypropylene composite separator, etc.

[0062] According to the embodiments of this application, the battery can be a single cell, a battery module, a battery pack, etc. The specific structure of the battery module or battery pack is not particularly limited and can be carried out with reference to conventional technology in the field, which will not be described in detail here.

[0063] A second aspect of this application provides a method for manufacturing a battery. According to embodiments of this application, the method includes the following steps:

[0064] S10: The positive electrode, negative electrode and separator are made into an electrode roll, and the electrode roll is assembled into an outer packaging. Electrolyte is injected into the outer packaging to form the first battery cell.

[0065] In some embodiments, the positive electrode active material, positive electrode conductive agent, and positive electrode binder can be mixed to prepare a positive electrode slurry and coated onto the positive electrode current collector. Then, after drying, rolling, cutting, etc., a positive electrode sheet is prepared.

[0066] In some embodiments, a negative electrode active material, a negative electrode conductive agent, and a negative electrode binder can be mixed to prepare a negative electrode slurry, which is then coated onto a negative electrode current collector. After drying, rolling, cutting, etc., a negative electrode sheet is prepared.

[0067] In some embodiments, the prepared positive electrode, negative electrode and separator can be made into an electrode roll by a stacking process or a winding process, and then assembled into an outer packaging (such as an aluminum shell), injected with electrolyte, and completed to obtain the first battery cell.

[0068] S20: Inject supplementary electrolyte, monomer and initiator into the first cell, let it stand, and obtain the second cell.

[0069] In some embodiments, a supplementary electrolyte (which can be the same as the previous electrolyte) is injected into the first cell after formation, along with monomers and initiators required for forming the gel electrolyte, and the cell is allowed to stand to allow the electrolyte to fully saturate it. This allows for thorough electrolyte saturation, improving the overall performance of the battery.

[0070] In some embodiments, the polymer monomers include one or more of acrylates, acrylonitrile, ethylene oxide, methyl methacrylate, and vinylidene fluoride. This is beneficial for improving the ionic conductivity, mechanical properties, thermal stability, and interfacial compatibility of the gel electrolyte, thereby improving the overall performance of the battery.

[0071] In some embodiments, the amount of monomer added is 0.5wt% to 5wt% of the total electrolyte (the total amount of electrolyte injected before formation and the supplementary electrolyte injected after formation), specifically such as 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt%, or any range between two of these. Within the above range, the gel electrolyte has a high proportion of dispersion medium, continuous ion migration channels, and high conductivity; at the same time, it has close contact with the electrode and low interfacial impedance, which is beneficial to improving the overall performance of the battery.

[0072] In some embodiments, the initiator includes at least one of dimethyl azobisisobutyrate (AIBME), azobisisobutyronitrile (AIBN), and azobisisoheptanenitrile. This allows for effective initiation of monomer polymerization, thereby conveniently and efficiently obtaining a gel electrolyte.

[0073] In some embodiments, the initiator is added at a rate of 1 wt% to 5 wt% of the monomer, specifically 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, or any range between two of these. Within this range, the reaction rate can be accelerated, the monomer conversion rate improved, a polymer with suitable molecular weight and molecular weight distribution obtained, and the overall performance of the gel electrolyte enhanced.

[0074] S30: A gel electrolyte is formed inside the electrode roll of the second cell, and a liquid electrolyte is present in the gap between the electrode roll and the outer packaging to obtain a battery.

[0075] In this step, a gel-state electrolyte can be formed by performing pulsed charge-discharge cycles on the second cell for a predetermined time using a pulsed current. Specifically, by using a pulsed current to charge and discharge the second cell, the electrode roll temperature is preferentially increased, which in turn allows the electrolyte inside the electrode roll to preferentially solidify, resulting in a battery where the electrolyte inside the electrode roll is in a gel state, while at least a portion of the first electrolyte in the gap between the electrode roll and the outer packaging remains in a liquid state. Moreover, the pulsed charge-discharge cycle method can also reduce the possibility of lithium plating on the negative electrode, thus improving battery safety.

[0076] It is understood that during the pulse charge-discharge cycle, the charging voltage does not exceed the upper limit of the battery's operating voltage range, and the discharging voltage does not fall below the lower limit of the battery's operating voltage range. The battery's operating voltage range is related to the type of positive electrode active material used in the battery. For example, when the positive electrode active material is lithium iron phosphate, the battery's operating voltage range is 2.5V to 3.65V. The operating voltage range for other positive electrode active materials can be determined by referring to their battery performance, and will not be elaborated upon here.

[0077] According to an embodiment of this application, the pulse charge-discharge cycle includes multiple charge-discharge cycles, wherein at least one of the charge-discharge cycles includes: charging with a first current for a first time, resting for a second time, discharging with a second current for a third time, and resting for a fourth time. Therefore, the operation is convenient and simple, and the curing effect is better.

[0078] According to embodiments of this application, the charging rate of the first current is 2C to 6C, specifically within the range of 2C, 2.5C, 3C, 3.5C, 4C, 4.5C, 5C, 5.5C, 6C, or any two of these ranges. This charging current range allows for a uniform temperature rise in the internal electrode rolls of the battery, thereby causing the electrolyte inside the electrode rolls to solidify uniformly, resulting in a gel-like electrolyte with good performance. If the charging rate is less than 2C, the internal temperature rise of the battery may be slow; if the charging rate is too high, such as greater than 6C, the battery may be damaged.

[0079] According to an embodiment of this application, the first time is 10s to 60s, specifically 10s, 20s, 30s, 40s, 50s, 60s, or any two of these ranges. Within the above time range, it is beneficial for the temperature inside the electrode roll to rise uniformly, thereby facilitating the obtaining of a gel electrolyte with better uniformity.

[0080] According to embodiments of this application, the second time is 10s to 30s, specifically 10s, 15s, 20s, 25s, 30s, or any combination thereof. Within this time range, it is beneficial for the temperature inside the electrode roll to rise uniformly, thereby facilitating the obtaining of a gel electrolyte with better uniformity.

[0081] According to embodiments of this application, the discharge rate of the second current is 2C to 6C, specifically within the range of 2C, 2.5C, 3C, 3.5C, 4C, 4.5C, 5C, 5.5C, 6C, or any two of these ranges. This discharge current allows the temperature of the electrode rolls inside the battery to rise uniformly, thereby causing the electrolyte inside the electrode rolls to solidify uniformly, resulting in a gel-state electrolyte with good performance.

[0082] According to embodiments of this application, the third time is 10s to 60s, specifically 10s, 20s, 30s, 40s, 50s, 60s, or any combination thereof. Within this time range, it is beneficial for the temperature inside the electrode roll to rise uniformly, thereby facilitating the obtaining of a gel electrolyte with better uniformity.

[0083] According to embodiments of this application, the fourth time is 10s to 30s, specifically 10s, 15s, 20s, 25s, 30s, or any combination thereof. Within this time range, it is beneficial for the temperature inside the electrode roll to rise uniformly, thereby facilitating the obtaining of a gel electrolyte with better uniformity.

[0084] According to an embodiment of the present application, during the pulse charge and discharge cycle, the temperature of the electrode roll is higher than the temperature at the gap between the electrode roll and the outer package. Thereby, it can be ensured that a gel electrolyte is formed inside the electrode roll, while the electrolyte remains in a liquid state at the gap between the electrode roll and the outer package.

[0085] According to an embodiment of the present application, the predetermined time is 2h to 24h, specifically such as 2h, 5h, 8h, 10h, 12h, 15h, 18h, 20h, 22h, 24h or the range between any two of them. Within the above time range, the electrolyte inside the electrode roll can be fully and uniformly solidified, and at the same time, the electrolyte at the gap between the electrode roll and the outer package can remain in a liquid state, which is beneficial to improving the cycle life of the battery.

[0086] According to an embodiment of the present application, the ambient temperature of the pulse charge and discharge cycle is 20°C to 50°C, specifically such as 20°C, 22°C, 24°C, 26°C, 28°C, 30°C, 35°C, 40°C, 45°C, 50°C or the range between any two of them. Thereby, it is convenient to implement, beneficial to keeping the electrolyte at the gap between the electrode roll and the outer package in a liquid state, and the cost is relatively low.

[0087] As an example, in this step, the second battery cell can be charged and discharged with a pulse current of 2C to 6C in an environment with a set temperature T1 (20°C < T1 < 30°C), so that the temperature of the electrode roll of the second battery cell rises to 60°C to 80°C and continues to cycle for 2 hours to 24 hours. The present application adopts an internal self-heating method to replace the external heating method to induce the polymerization of monomers in the electrolyte. Due to heat conduction, the outside of the electrode roll is maintained below the polymerization temperature, and the electrolyte still remains in a liquid state. The battery obtained thereby has better safety and a longer cycle life.

[0088] It can be understood that the polymerization of monomers to form a gel electrolyte can be initiated only when the temperature inside the electrode roll reaches above the polymerization temperature of the monomers. However, the temperature inside the battery electrode roll is not convenient to measure directly. The electrode tab is usually connected to the current collector of the positive electrode or the negative electrode and is close to the temperature inside the electrode roll. Therefore, the temperature inside the electrode roll can be judged by detecting the temperature of the battery electrode tab. In some embodiments, when the temperature of the electrode tab is higher than the curing temperature by 20°C, it is considered that the temperature inside the electrode roll reaches the monomer polymerization temperature, that is, the gel electrolyte curing temperature. Taking the electrolyte curing temperature of 60°C as an example, when the temperature of the electrode tab is 80°C, it is considered that the temperature inside the electrode roll reaches the electrolyte curing temperature of 60°C and the monomers start to polymerize to form a gel electrolyte.

[0089] According to an embodiment of the present application, after stopping the pulse charge and discharge cycle, after the second battery cell cools down to room temperature, various tests such as battery cycle and safety can also be carried out according to needs.

[0090] A third aspect of this application provides an electrical device. According to an embodiment of this application, the electrical device includes the battery described above. This electrical device has a long service life.

[0091] According to embodiments of this application, the specific type of electrical device is not particularly limited and can be any device that uses a battery as a power source or energy storage unit. As examples, electrical devices include, but are not limited to, electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), mobile terminals (e.g., mobile phones, laptops, game consoles, wearable devices, etc.), drones, aerospace equipment, satellites, ships, energy storage systems, etc.

[0092] It is understandable that, in addition to the battery mentioned above, the electrical device also includes necessary structures and components, all of which can be made with reference to conventional technologies. For example, an electric vehicle may include a body, chassis, tires, navigation system, radar system, steering system, braking system, lubrication system, cooling system, driving system, etc., which will not be described in detail here.

[0093] The embodiments of this application are described in detail below.

[0094] Example 1:

[0095] S1. A positive electrode slurry is prepared by mixing lithium iron phosphate, carbon black, and PVDF in a mass ratio of 96:2:2 and then coating it onto aluminum foil to obtain a positive electrode sheet.

[0096] S2. A negative electrode slurry is prepared by mixing graphite (negative electrode material), carbon black (conductive agent), SBR (binder), and CMC (dispersant) in a mass ratio of 95.5:1:2:1.5 and then coating it onto copper foil to obtain a negative electrode sheet.

[0097] S3. The positive electrode, negative electrode and polyethylene (PE) separator prepared above are made into electrode rolls and assembled into an aluminum shell. An electrolyte with lithium hexafluorophosphate as salt and EC, DMC and EMC as solvent is injected and the formation is completed at 25°C in a conventional manner (0.02C charging to 10% SOC, 0.1C charging to 30% SOC).

[0098] S4. Inject the formed battery with supplementary electrolyte (i.e., secondary electrolyte injection), and add the monomer 2,2,2-trifluoroethyl methacrylate (PTFEMA) and the initiator dimethyl azobisisobutyrate (AIBME) required for forming the gel electrolyte. Let it stand at room temperature for 96 hours to allow the electrolyte to fully impregnate the battery. The amount of monomer added is 2% of the total mass of the electrolyte, and the amount of initiator added is 1% of the monomer mass.

[0099] S5. At an ambient temperature of 45℃, perform a charge-discharge cycle with a periodic pulse current of 3C (1C=320A) for 30 seconds, rest for 10 seconds, 3C discharge for 30 seconds, and rest for 10 seconds, until the internal temperature of the battery rises to above 65℃. Continue this cycle for 12 hours, then stop charging and discharging. After the battery temperature drops to 25℃, perform a 0.5C capacity test.

[0100] Disassembling the battery and observing the interface reveals that there is no obvious gel-like electrolyte on the outside of the electrode rolls, but rather a significant amount of electrolyte that remains in a liquid state. After disassembling the electrode rolls, the surface of the internal electrode plates shows no obvious liquid electrolyte; it is almost entirely gel-like electrolyte.

[0101] Example 2:

[0102] Same as Example 1, except that:

[0103] At an ambient temperature of 45℃, the battery was charged and discharged using a periodic pulse current of 2C (1C=320A) for 30 seconds, rested for 10 seconds, 2C discharge for 30 seconds, and rested for 10 seconds, until the internal temperature of the battery rose above 60℃. This cycle was continued for 24 hours, after which the charging and discharging was stopped. After the battery temperature dropped to 25℃, a 0.5C capacity test was performed.

[0104] Disassembling the battery and observing the interface reveals that there is no obvious gel-like electrolyte on the outside of the electrode rolls, but rather a significant amount of electrolyte that remains in a liquid state. After disassembling the electrode rolls, the surface of the internal electrode plates shows no obvious liquid electrolyte; it is almost entirely gel-like electrolyte.

[0105] Example 3:

[0106] Same as Example 1, except that:

[0107] At an ambient temperature of 45℃, the battery was charged and discharged using a periodic pulse current of 6C (1C=320A) for 30 seconds, rested for 10 seconds, discharged at 6C for 30 seconds, and rested for 10 seconds, until the internal temperature of the battery rose above 70℃. This cycle was continued for 24 hours, after which the charging and discharging was stopped. After the battery temperature dropped to 25℃, a 0.5C capacity test was performed.

[0108] Disassembling the battery and observing the interface reveals that there is no obvious gel-like electrolyte on the outside of the electrode rolls, but rather a significant amount of electrolyte that remains in a liquid state. After disassembling the electrode rolls, the surface of the internal electrode plates shows no obvious liquid electrolyte; it is almost entirely gel-like electrolyte.

[0109] Comparative Example 1:

[0110] Same as Example 1, except that:

[0111] After the battery obtained in step S4 is cured in an oven at 65°C for 12 hours, it is then subjected to capacity testing.

[0112] Upon disassembling the battery and observing the interface, it can be seen that a large amount of gel-like electrolyte is present on the outside of the electrode rolls, with no liquid electrolyte. The internal electrode surfaces show no obvious liquid electrolyte; they are primarily composed of gel-like electrolyte.

[0113] Comparative Example 2:

[0114] Same as Example 1, except that:

[0115] In step S4, no polymer monomers or initiators were added to the electrolyte for the second injection. After the battery was left to stand at room temperature for 12 hours, it was placed in an oven at 65°C for capacity testing.

[0116] Disassembling the battery and observing the interface reveals that no gel-like electrolyte is present on the outside of the electrode rolls, but there is a significant amount of liquid electrolyte. Inside the electrode rolls, the surface of the electrode plates contains liquid electrolyte, but no gel-like electrolyte is present.

[0117] Performance testing:

[0118] 1. Test the battery's cycle performance: Test the battery after capacity grading with a charge-discharge cycle at a power of 0.5P within a voltage range of 2.5-3.65V, and calculate the energy retention rate of the battery after 1000 cycles.

[0119] 2. Perform a needle penetration test on the battery sample. Fully charge the battery (cutoff voltage 3.65V), and use an 8mm steel needle to penetrate the battery at 25mm / s. Observe for 1 hour and check for phenomena such as fire or explosion.

[0120] 3. Lithium plating on the negative electrode: After fully charging the battery and disassembling it, a normal battery without lithium plating will have a golden-yellow negative electrode. If lithium plating is present on the surface of the negative electrode, gray spots will be visible to the naked eye. In addition, observation with a scanning electron microscope (SEM) will reveal substances with morphologies different from graphite particles.

[0121] 4. Percentage of the first electrolyte in the total battery mass: Weigh the total battery mass, then make a hole in the battery casing and pour out the first electrolyte, which is still in a liquid state. Weigh the mass of the liquid first electrolyte and calculate its percentage of the total battery mass.

[0122] Table 1: Performance Test Results

[0123]

[0124] As can be seen from Example 1 and Comparative Example 1, the battery of the present invention can maintain liquid electrolyte between the electrode roll and the casing, which can improve the cycle performance of the battery.

[0125] As can be seen from Example 1 and Comparative Example 2, the gel-state battery obtained by the present invention can improve the safety performance of the battery.

[0126] Comparative Examples 1 and 2 show that the gel-state battery obtained by the heat curing method has worse cycle performance than the conventional liquid battery.

[0127] In the description of this invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0128] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are 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.

[0129] 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 battery, characterized in that, include: Outer packaging, the interior of which defines a storage space; An electrode roll, comprising a positive electrode sheet, a negative electrode sheet, a separator, and a gel electrolyte, is disposed in the receiving space; wherein the separator is disposed between adjacent positive and negative electrode sheets, and the gel electrolyte is impregnated in the positive electrode sheet, the negative electrode sheet, and the separator; A first electrolyte is located in the gap between the outer packaging and the electrode roll; Based on the total mass of the battery, the mass percentage of the first electrolyte is 1wt%~6wt%; Based on the total mass of the first electrolyte and the gel electrolyte, the mass percentage of the first electrolyte is 5wt% to 30wt%.

2. The battery according to claim 1, characterized in that, The gel electrolyte includes: polymer backbone, and A dispersion medium, wherein the dispersion medium is filled in the polymer backbone, the dispersion medium comprising a second electrolyte.

3. The battery according to claim 2, characterized in that, The polymer backbone in the gel electrolyte has a mass percentage of 0.5wt% to 5wt%; and / or the polymer backbone includes at least one of polyacrylate, polyacrylonitrile, polyethylene oxide, polymethyl methacrylate, and polyvinylidene fluoride.

4. The battery according to claim 2, characterized in that, The first electrolyte and the second electrolyte each independently comprise an organic solvent and an electrolyte salt; The solvent includes at least one selected from ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and propylene carbonate; and / or, The electrolyte salt includes at least one of lithium hexafluorophosphate, lithium difluorosulfonylimide, lithium difluorooxalate borate, and lithium difluorophosphate.

5. The battery according to claim 1, characterized in that, In a fresh battery, there is no lithium plating on the surface of the negative electrode.

6. The battery according to claim 1, characterized in that, The positive electrode comprises lithium iron phosphate or lithium manganese iron phosphate; and / or, the negative electrode comprises graphite.

7. A method for preparing a battery, characterized in that, include: The positive electrode, negative electrode and separator are made into an electrode roll, and the electrode roll is assembled into an outer packaging. Electrolyte is injected into the outer packaging to form the first battery cell. Inject supplementary electrolyte, monomer and initiator into the first cell, let it stand, and obtain the second cell; A gel electrolyte is formed inside the electrode roll of the second cell, and a liquid electrolyte is present in the gap between the electrode roll and the outer packaging to obtain a battery; The liquid electrolyte accounts for 1 wt% to 6 wt% of the total mass of the battery. Based on the total mass of the liquid electrolyte and the gel electrolyte, the mass percentage of the liquid electrolyte is 5wt% to 30wt%.

8. The method according to claim 7, characterized in that, The formation of a gel-like electrolyte inside the electrode roll of the second battery cell, and the presence of a liquid electrolyte in the gap between the electrode roll and the outer packaging, includes: The second cell is subjected to pulse charge-discharge cycles for a predetermined time using pulse current.

9. The method according to claim 8, characterized in that, The pulse charge-discharge cycle includes multiple charge-discharge cycles, one of which includes: Charge with the first current for a first time, then pause for a second time, discharge with the second current for a third time, and pause for a fourth time.

10. The method according to claim 9, characterized in that, At least one of the following conditions must be met: The charging rate of the first current is 2C~6C; The first time interval is 10s to 60s; The second time is 10s~30s; The discharge rate of the second current is 2C~6C; The third time is 10s~60s; The fourth time period is 10s~30s; The scheduled time is 2 hours to 24 hours; The ambient temperature for the pulse charge-discharge cycle is 20℃~50℃.

11. The method according to claim 8, characterized in that, During the pulse charge-discharge cycle, the temperature of the electrode roll is higher than the temperature at the gap between the electrode roll and the outer packaging.

12. The method according to claim 7, characterized in that, At least one of the following conditions must be met: Based on the total mass of the electrolyte and the supplementary electrolyte, the mass percentage of the monomer is 0.5 wt% to 5 wt%. The amount of the initiator added is 1 wt% to 5 wt% of the total mass of the monomer; The initiator includes at least one of dimethyl azobisisobutyrate, azobisisobutyronitrile, and azobisisoheptanenitrile; The monomers include at least one of acrylate, acrylonitrile, ethylene oxide, methyl methacrylate, and vinylidene fluoride.

13. An electrical appliance, characterized in that, The battery includes any one of claims 1 to 6.

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