Controllably etched shorted overcharge-preventing battery cell and secondary battery comprising the same

Abstract

This invention relates to a controllable corrosion-resistant overcharge protection cell and a secondary battery comprising the cell. The cell includes a positive electrode, a negative electrode, and an electrolyte; wherein the positive electrode includes a positive electrode tab, a positive electrode current collector, and a positive electrode active material, and the positive electrode tab and / or the positive electrode current collector includes an aluminum-containing substrate; the electrolyte contains an organic solvent represented by chemical formula I and / or chemical formula II, wherein R... 1 Each is independently selected from F, Cl, CF3, and C. n H 2n+1 C n H 2n+1‑x F x Or any combination thereof; R 2 and R 3 Whether the two are the same or different, each is independently selected from CF3 and C. n H 2n+1 C n H 2n+1‑x F x Or any combination thereof; R 4 Each was independently selected from C k H 2k‑q F q Or (CH2) k‑1 The annular portion shown in O (single ring, multi-ring, fused ring) is defined in the formula, where k≥3, q≥0, and q≤2k. The battery cell of this invention consumes excess charge through an active electrochemical reaction, preventing excessive heat generation during overcharging and avoiding the possibility of combustion or explosion.

Description

Technical Field

[0001] This invention relates to the field of secondary batteries, and more specifically to a controllable corrosion-resistant overcharge cell and a secondary battery comprising the cell. Background Technology

[0002] The poor driving range and safety issues of lithium-ion batteries have hindered their rapid development, with safety being particularly critical. While lithium-ion batteries are suitable for electric vehicles, they suffer from high cost and insufficient safety. Overcharging, breakdown, deformation due to compression, or use in high-temperature environments can cause chemical reactions between the electrodes and the organic electrolyte. These reactions generate significant heat and gases, which, if not dissipated promptly, can lead to combustion, fire, or explosion. To prevent overcharging of lithium-ion batteries, current methods typically involve controlling the battery voltage through both external and internal means.

[0003] External methods primarily involve control through the Battery Management System (BMS), such as current protection circuits (CID), battery vents, and thermal fuses. These are emergency measures after overcharging, increasing costs and reducing the battery's energy-to-weight ratio. They do not eliminate the risk of overcharging from the battery itself. When the BMS fails or loses connection with the battery, the battery still faces the risk of overcharging and potential safety hazards. Internal methods mainly involve adding anti-overcharge additives to the electrolyte. These additives are primarily divided into redox additives and electropolymerization additives. Electrolyte additives can improve battery safety performance. Adding additives to the electrolyte does not increase battery volume or mass and can react promptly in dangerous situations such as overcharging, preventing further damage. This is a highly efficient and low-cost method.

[0004] Alkyl carbonate solvents in conventional lithium-ion battery electrolytes are highly reactive and flammable, and are prone to changes at the high temperatures generated during lithiation and delithiation processes. At high temperatures, the solid electrolyte interphase (SEI) layer formed by the graphite anode is easily damaged, leading to the decomposition of the cathode material and the release of heat, resulting in a vicious cycle and potential explosion hazards. Commercial lithium-ion battery electrolytes typically dissolve LiPF6 in organic carbonates, forming a solution with a concentration of approximately 1 mol / L. While current electrolytes show potential in improving the safety of lithium-ion batteries, they also have some drawbacks and shortcomings, such as chemical stability issues. Existing additives may undergo undesirable side reactions with the electrolyte or electrode materials under high temperature or high voltage conditions, affecting the overall stability of the battery. Moreover, fluoroethylene carbonate (FEC) may reduce initial coulombic efficiency and generate gas when forming a protective layer, affecting the battery's energy density and overall performance. Although FEC can form a protective layer during overcharging, this protective layer may lead to gradual capacity decay during long-term cycling. Furthermore, FEC may decompose at high temperatures, generating heat, requiring effective thermal management measures.

[0005] Despite the great potential of electrolytes with overcharge protection in improving the safety of lithium-ion batteries, there are still many challenges and shortcomings in terms of chemical stability, battery performance, cost and manufacturing complexity, thermal management, reaction controllability and performance consistency.

[0006] Therefore, there is an urgent need to provide a new method and battery cell to prevent overcharging of lithium-ion batteries. Summary of the Invention

[0007] The purpose of this invention is to address the challenges and shortcomings of existing technologies. To this end, the inventors have discovered that using a specific electrolyte to corrode the aluminum-containing positive electrode current collector or tab can prevent safety issues such as combustion and explosion caused by overcharging. In this invention, a controlled corrosion reaction between the electrolyte and the aluminum-containing positive electrode is utilized. When the battery is overcharged, this controlled corrosion reaction consumes excess charge, preventing overheating, combustion, or explosion inside the battery. In this invention, the electrolyte contains components that can trigger a corrosion reaction at high voltages (>3.7V). When overcharging occurs, these components react with the aluminum, thereby corroding the aluminum to cut off the electron transport path, thus stopping charging and reducing the risk of overcharging.

[0008] On the one hand, the present invention provides a controllable corrosion-resistant overcharge protection cell, the cell comprising a positive electrode, a negative electrode and an electrolyte;

[0009] The positive electrode includes a positive electrode tab, a positive electrode current collector, and a positive electrode active material, wherein the positive electrode tab and / or the positive electrode current collector includes an aluminum-containing substrate;

[0010] The electrolyte contains an organic solvent represented by chemical formula I and / or chemical formula II:

[0011]

[0012]

[0013] In the formula, R 1 Each is independently selected from F, Cl, CF3, C n H 2n+1 C n H 2n+1-x F x Or any combination thereof, where n = 1-100, x = 1-3;

[0014] R 2 and R 3 Whether the two are the same or different, each is independently selected from CF3 and C. n H 2n+1 C n H 2n+1-x Fx Or any combination thereof, where n = 1-100, x = 1-3;

[0015] R 4 Each was independently selected from C k H 2k-q F q Or (CH2) k-1 The annular portion shown in O is given by the formula, where k≥3, q≥0, and q≤2k.

[0016] In a specific embodiment, the organic solvent represented by chemical formula I is dimethylaminosulfonyl fluoride (FSA); the organic solvent represented by chemical formula II is selected from one or more of the following cyclic organic solvents:

[0017]

[0018] In a specific embodiment, the positive electrode active material includes lithium iron phosphate.

[0019] In a specific embodiment, the positive electrode active material includes a nickel-cobalt-manganese ternary material or a nickel-cobalt-aluminum ternary material, and the electrolyte further contains 0.1-5% by weight of an overcharge protection agent based on the weight of the electrolyte.

[0020] In a specific embodiment, the overcharge protectant is selected from one or more of the following: vinylene carbonate, ethylene ethylene carbonate, fluoroethylene carbonate, 1,3-propanesulfonate lactone, 1,4-butanesulfonate lactone, vinyl sulfate, vinyl sulfite, propylene sulfate, propylene sulfite, butene sulfate, and lithium difluorophosphate.

[0021] In a specific embodiment, the aluminum-containing substrate is selected from aluminum foil, aluminum alloy, aluminized steel foil, aluminum-coated composite material, carbon-coated aluminum foil, nanostructured aluminum material, aluminum-containing conductive polymer composite material, or a combination thereof.

[0022] In a specific embodiment, the mass ratio of aluminum in the aluminum-containing substrate to the organic solvent is 50:(10-0.1).

[0023] In a specific embodiment, the amount of the organic solvent is 30%-95% based on the mass of the electrolyte, preferably 50%-85%.

[0024] In a specific embodiment, the electrolyte is a non-aqueous electrolyte.

[0025] In a specific embodiment, the electrolyte further comprises a lithium salt, preferably LiFSI and / or LiTFSI.

[0026] In a specific embodiment, the negative electrode includes a negative electrode tab, a negative electrode current collector, and a negative electrode active material located on the negative electrode current collector.

[0027] In a specific embodiment, the negative electrode active material comprises graphite material and optional conductive agent and binder; wherein the graphite material is selected from one or more combinations of natural graphite, artificial graphite, mesophase carbon microspheres (MCMB), hard carbon, silicon alloy, and silicon-carbon.

[0028] According to a second aspect of this application, a secondary battery is provided, comprising the aforementioned battery cell.

[0029] According to a third aspect of this application, an electrical device is provided, including the secondary battery.

[0030] The battery cell described in this invention consumes excess charge through an active electrochemical reaction, preventing excessive heat generation during overcharging and thus avoiding the possibility of combustion or explosion. Compared to passive safety measures, this method is more proactive and effective in protecting battery safety.

[0031] Compared to traditional electrolyte solvents or additives that undergo polymer molecular reactions, the battery cell of this invention does not form polymers on the electrodes, nor does it increase the resistance to ion transport, thus preventing battery damage. Compared to traditional electrolyte solvents or additives that undergo redox reactions, this invention prevents overcharging of the battery cell through controlled corrosion, overcoming the technical defects of limited protection and complex design. It also exhibits good long-term stability, requiring only the electrolyte solvent to react, without relying on specific protective materials. Overcharging is prevented by breaking the circuit through the corrosion reaction between the electrolyte and the aluminum-containing current collector or tabs. Furthermore, the electrolyte solvent molecules of this invention are smaller, maintaining their fluidity at low temperatures and reducing electrolyte viscosity, thereby improving battery performance in low-temperature environments. At high temperatures, it also maintains its chemical stability, resisting decomposition and ensuring normal battery operation in high-temperature environments. The electrolyte exhibits good chemical and electrochemical stability, remaining stable over a wide voltage range and at high temperatures, further enhancing its ionic conductivity. High ionic conductivity means lower internal resistance in the electrolyte, which helps reduce internal losses in the battery. Low internal resistance means less internal loss during battery operation, improving energy efficiency. Reducing heat buildup during charging and discharging also helps extend battery cycle life.

[0032] These and other features and advantages will become apparent from the following detailed description. It should be understood that the foregoing general description and the following detailed description are illustrative only and do not limit the scope of the claims. Attached Figure Description

[0033] Figure 1 The experiment showed that for the ternary cathode of the LiFSI / FSA system, when no overcharge protection agent was added to the electrolyte, the aluminum foil underwent an etching reaction when the battery was charged to 3.7V, and the battery could not continue to charge.

[0034] Figure 2 The results show that for the ternary cathode of the LiFSI / FSA system, when an overcharge protection agent is added to the electrolyte, the etching voltage of the aluminum foil increases to above 4.2V, the battery is charged to 4.2V and completes a full charge-discharge process. Detailed Implementation

[0035] Unless otherwise defined, the technical or scientific terms used in the claims and description shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0036] In this document, the term “about” used to modify, for example, the amount, concentration, process temperature, process time, flow rate, and similar values ​​and ranges of an ingredient in a composition, or the scale and similar values ​​and ranges of a component, refers to possible changes in numerical values, such as those arising from routine measurements and operations used in the manufacture or use of formulations for preparing materials, compositions, complexes, concentrates, components, articles; accidental errors in these processes; differences in the purity or composition of the manufacturing, source, or starting materials used to carry out the method; and similar factors.

[0037] In this document, when a numerical range such as 5-25 is given, this means at least 5 or not less than 5 and separately and independently not greater than or less than 25. In some embodiments, such a range may be independently defined as not less than 5 and separately and independently not greater than 25. Values ​​having such a range, such as 10, -15, or 10-20, also include the lower and upper limits of the range separately and independently in the same manner.

[0038] As used herein, unless otherwise specified, “% by weight” or “percentage by weight” for a component refers to the total weight of the composition or article containing that component. Terms such as “comprising” or “including” indicate that the elements or articles preceding “comprising” or “including” encompass the elements or articles listed following “comprising” or “including” and their equivalents, and do not exclude other elements or articles.

[0039] In some embodiments of the present invention, the controllable corrosion-resistant overcharge protection core includes a positive electrode, a negative electrode, and an electrolyte; wherein the positive electrode includes a positive electrode tab, a positive electrode current collector, and a positive electrode active material, and the positive electrode tab and / or the positive electrode current collector includes an aluminum-containing substrate. The aluminum-containing substrate is selected from aluminum foil, aluminum alloy, aluminized steel foil, aluminum-coated composite material, carbon-coated aluminum foil, nanostructured aluminum material, aluminum-containing conductive polymer composite material, or combinations thereof.

[0040] In some embodiments, the electrolyte comprises an organic solvent represented by Formula I:

[0041]

[0042] In the formula, R 1 Each is independently selected from F, Cl, and C. n H 2n+1 C n H 2n+1-x F x Or any combination thereof, where n = 1-100, 2-50, 5-20 or 8-12, x = 1, 2 or 3; in some embodiments, R 1 Each is independently selected from F and CF3; in some implementations, R 1 =F;

[0043] R 2 and R 3 They can be the same or different, and each can be independently selected from C. n H 2n+1 C n H 2n+1-x F x Or any combination thereof, where n = 1-100, 2-50, 5-20 or 8-12, x = 1, 2 or 3; in some embodiments, R 2 and R 3 Each is independently selected from CH3- and CH2F-; in some embodiments, R 2 =R 3 =CH3-;

[0044] R 4 Each was independently selected from C k H 2k-q F q Or (CH2) k-1 The annular portion shown in O, where k≥3, q≥0, q≤2k. In some embodiments, k≥5, q≥1, q≤2k. In some embodiments, R... 4 =(CH2)4O-. In some embodiments, the annular portion includes a monocyclic portion, a polycyclic portion, or a fused-ring portion.

[0045] In some embodiments, the electrolyte comprises an organic solvent represented by Formula II:

[0046]

[0047] In the formula, R 1 Each is independently selected from F, Cl, and C. n H 2n+1 C n H 2n+1-x F x Or any combination thereof, where n = 1-100, 2-50, 5-20 or 8-12, x = 1, 2 or 3; in some embodiments, R 1 Each is independently selected from F and CF3; in some implementations, R 1 =F;

[0048] R 2 and R 3 They can be the same or different, and each can be independently selected from C. n H 2n+1 C n H 2n+1-x F x Or any combination thereof, where n = 1-100, 2-50, 5-20 or 8-12, x = 1, 2 or 3; in some embodiments, R 2 and R 3 Each is independently selected from CH3- and CH2F-; in some embodiments, R 2 =R 3 =CH3-;

[0049] R 4 Each was independently selected from C k H 2k-q F q Or (CH2) k-1 The annular portion shown in O, where k≥3, q≥0, q≤2k. In some embodiments, k≥5, q≥1, q≤2k. In some embodiments, R... 4 =(CH2)4O-. In some embodiments, the annular portion includes a monocyclic portion, a polycyclic portion, or a fused-ring portion.

[0050] In some embodiments of the present invention, the organic solvent represented by Formula I is selected from N,N-dimethylaminosulfonyl fluoride (FSA), N,N-dimethylethylsulfonyl fluoride, or combinations thereof.

[0051] In some embodiments of the present invention, the organic solvent represented by Formula II is selected from one or more of the following cyclic organic solvents:

[0052]

[0053] In some embodiments of the present invention, the positive electrode active material includes lithium iron phosphate active material. In the lithium iron phosphate active material cell system, the voltage safety threshold of the secondary battery containing this cell is 3.65V; therefore, no additional overcharge protection agent is required in this system. When the battery voltage exceeds the safety threshold (3.65V) of the lithium iron phosphate battery system, the organic solvent will react with the aluminum-based material to form corrosion that inhibits the electrochemical reaction, causing the battery to disconnect and preventing the electrochemical reaction from continuing. In some embodiments, the electrolyte comprises only a lithium salt electrolyte and organic solvents represented by chemical formulas I and II; or the electrolyte is composed of a lithium salt electrolyte and organic solvents represented by chemical formulas I and II.

[0054] In some embodiments of the present invention, the electrolyte may contain an overcharge protectant to adjust and increase the internal resistance of the battery during overcharging, thereby achieving overcharge erosion protection under different systems. When the battery voltage exceeds the safety threshold (4.2V) of the ternary battery system, the organic solvent will react with the aluminum-based material to form corrosion that inhibits the electrochemical reaction, causing the battery to disconnect and preventing the electrochemical reaction from continuing. In some embodiments of the present invention, the positive electrode active material includes a nickel-cobalt-manganese ternary material or a nickel-cobalt-aluminum ternary material, and the electrolyte further contains 0.1-5% by weight of the overcharge protectant. In some embodiments of the present invention, the overcharge protectant is selected from one or more combinations of vinylene carbonate, ethylene ethylene carbonate, fluoroethylene carbonate, 1,3-propanesulfonate lactone, 1,4-butanesulfonate lactone, vinyl sulfate, vinyl sulfite, propylene sulfate, propylene sulfite, butene sulfate, and lithium difluorophosphate.

[0055] In some embodiments of the present invention, the mass ratio of aluminum element in the aluminum-containing substrate to the organic solvent is 50:(10-0.1), 50:(8-0.5), 50:(5-1), or 50:(3-2).

[0056] In some embodiments of the present invention, the amount of the organic solvent, based on the mass of the electrolyte, is 30%-95%, 40%-85%, 50%-75%, or 60%-65%. In this invention, if the content of the organic solvent is too low, even if it can react with the aluminum-containing substrate, it cannot effectively form corrosion, and is insufficient to effectively and continuously remove or block the overcharge current; the remaining current will still damage the battery. On the other hand, when the viscosity of the organic solvent is slightly high, a higher content of organic solvent may cause the electrolyte viscosity to be too high, which is not conducive to lithium-ion migration and also has a significant impact on the electrochemical performance of the battery.

[0057] In this invention, since the voltage stability window of water is around 1.23V, while the voltage of a lithium iron phosphate battery is around 3.65V, an aqueous electrolyte cannot meet the requirements of this lithium iron phosphate system without the addition of an overcharge protection agent. Therefore, the electrolyte is a non-aqueous electrolyte.

[0058] In this invention, the electrolyte may contain various lithium salts commonly used in the art; in some embodiments, the lithium salts include LiFSI and / or LiTFSI.

[0059] In this invention, the negative electrode includes a negative electrode tab, a negative electrode current collector, and a negative electrode active material located on the negative electrode current collector. The negative electrode active material comprises graphite material and optionally a conductive agent and a binder; wherein the graphite material is selected from one or more combinations of natural graphite, artificial graphite, mesophase carbon microspheres (MCMB), hard carbon, silicon alloys, silicon-carbon, silicon suboxide, and lithium metal. In some embodiments, the negative electrode current collector comprises sodium metal or a sodium alloy.

[0060] Lithium secondary batteries

[0061] The lithium secondary battery of this application includes a positive electrode (plate), a negative electrode (plate), and an electrolyte (including liquid, semi-solid, and solid electrolytes). During the charging and discharging process, lithium ions repeatedly insert and extract between the positive and negative electrode plates. The electrolyte acts as a conductor of ions between the positive and negative electrode plates.

[0062] [Positive electrode plate]

[0063] In the secondary battery of this application, the positive electrode sheet includes a positive current collector and a positive electrode film layer (or positive electrode active material layer) disposed on at least one surface of the positive current collector and comprising a positive electrode active material. For example, the positive current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector. In the secondary battery of this application, the positive current collector can be a metal foil or a composite current collector. For example, the metal foil can be aluminum foil, and the composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum 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 and its copolymers, etc.).

[0064] In the secondary battery of this application, the positive electrode active material (substance) may be a positive electrode active material known in the art for use in secondary batteries. For example, the positive electrode active material may include one or more of the following: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for secondary batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, and lithium nickel cobalt manganese oxide (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2(NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811)), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05 One or more of lithium iron phosphates, such as O2 and its modified compounds. Examples of lithium-containing phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, and lithium iron manganese phosphate and carbon composites. In embodiments of this application, the second and third positive electrode active materials may be the same or different, and are selected from at least one of lithium iron phosphate (LFP), lithium manganese oxide (LMO), lithium nickel cobalt manganese oxide (NCM), lithium cobalt oxide (LCO), and lithium nickel cobalt aluminum oxide (NCA).

[0065] In some embodiments, the positive electrode film layer may optionally include a binder. Non-limiting examples of binders that can be used in the positive electrode film layer may include one or more of the following: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins. In embodiments of this application, the first positive electrode active material layer and / or the second positive electrode active material layer each independently contain a binder selected from polyvinylidene fluoride, polyacrylic acid, polytetrafluoroethylene, polyimide, and combinations thereof.

[0066] In some embodiments, the positive electrode film layer may optionally include a conductive agent. Examples of conductive agents used for the positive electrode film layer may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In embodiments of this application, the first positive electrode active material layer and / or the second positive electrode active material layer each independently contain a conductive agent composed of graphite, carbon black, acetylene black, graphene, carbon nanotubes, and combinations thereof.

[0067] In one embodiment of this application, the positive electrode can be prepared by dispersing the above-mentioned components for preparing the positive electrode, such as positive electrode active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a uniform positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0068] [Negative electrode plate]

[0069] In the secondary battery of this application, the negative electrode sheet does not exclude other additional functional layers besides the negative electrode substrate layer. For example, in some embodiments, the negative electrode sheet of this application may also include a conductive undercoating layer (e.g., composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode substrate layer and disposed on the surface of the negative electrode current collector. In other embodiments, the negative electrode sheet of this application may also include a protective covering layer covering the surface of the second negative electrode film layer.

[0070] In the secondary battery of this application, the negative electrode current collector can be a metal foil or a composite current collector. For example, the metal foil can be a copper foil, silver foil, iron foil, or an alloy of the above metals. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. It 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 base layer (such as a base layer made of polypropylene PP, polyethylene terephthalate PET, polybutylene terephthalate PBT, polystyrene PS, polyethylene PE and its copolymers, etc.).

[0071] [Electrolytes]

[0072] The electrolyte acts as a conductor of ions between the positive and negative electrode plates. The electrolyte can be selected from at least one of solid electrolytes, semi-solid electrolytes, and liquid electrolytes. In one embodiment of this application, the electrolyte may optionally contain additives. For example, additives may include one or more of the following: negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, additives that improve battery low-temperature performance, etc.

[0073] [Isolation membrane]

[0074] In one embodiment of this application, the secondary battery further includes a separator membrane that separates the anode side from the cathode side of the secondary battery, providing selective permeability or blocking for substances of different types, sizes, and charges within the system. For example, the separator membrane can insulate against electrons, physically isolate the positive and negative electrodes of the secondary battery, prevent internal short circuits, and form an electric field in a certain direction, while allowing ions in the battery to pass through the separator membrane and move between the positive and negative electrodes. In one embodiment of this application, the material used to prepare the separator membrane may include one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator membrane can be a single-layer film or a multilayer composite film. When the separator membrane is a multilayer composite film, the materials of each layer can be the same or different. In an embodiment of this application, the separator membrane is selected from polyolefin separator membranes, polyester separator membranes, polyimide separator membranes, polyamide separator membranes, and cellulose separator membranes.

[0075] In one embodiment of this application, the above-mentioned positive electrode sheet, negative electrode sheet and separator can be manufactured into electrode assembly / bare cell by winding process or stacking process.

[0076] In one embodiment of this application, the secondary battery may include an outer packaging that can be used to encapsulate the aforementioned electrode components and electrolyte. In some embodiments, the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. In other embodiments, the outer packaging of the secondary battery may be a soft pack, such as a pouch. The material of the soft pack may be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0077] The secondary battery of this application can be cylindrical, square, or any other arbitrary shape. The outer packaging may include a shell and a cover plate. The shell may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The shell has an opening communicating with the receiving cavity, and the cover plate can be placed over the opening to close the receiving cavity. Positive electrode plates, negative electrode plates, and a separator can be formed into an electrode assembly using a winding or stacking process. This electrode assembly is encapsulated in the receiving cavity, and the electrolyte is immersed in the electrode assembly. The secondary battery may contain one or more electrode assemblies.

[0078] In one embodiment of this application, a number of secondary batteries can be assembled together to form a battery module. The battery module contains two or more secondary batteries, the specific number depending on the application of the battery module and the parameters of the individual battery module.

[0079] In the battery module, multiple secondary batteries can be arranged sequentially along the length of the battery module. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary batteries can be secured with fasteners. Optionally, the battery module may also include a housing with a receiving space in which the multiple secondary batteries are housed.

[0080] In one embodiment of this application, two or more of the above-described battery modules can be assembled into a battery pack. The number of battery modules contained in the battery pack depends on the application of the battery pack and the parameters of individual battery modules. The battery pack may include a battery box and multiple battery modules disposed within the battery box. The battery box includes an upper box and a lower box, the upper box being able to cover and fit snugly onto the lower box to form a closed space for accommodating the battery modules. Two or more battery modules can be arranged in the battery box in a desired manner.

[0081] In one embodiment of this application, the example battery pack may include a battery box and multiple battery modules disposed within the battery box. The battery box includes an upper box and a lower box, the upper box covering the lower box and forming a closed space for accommodating the battery modules. The multiple battery modules can be arranged in any manner within the battery box.

[0082] Electrical appliances

[0083] In one embodiment of this application, the electrical device includes at least one of the secondary battery, battery module, or battery pack described in this application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device includes, but is not limited to, mobile digital devices (e.g., mobile phones, laptops, etc.), 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.), electric trains, ships and satellites, energy storage systems, etc.

[0084] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0085] In the following text, the effects of lithium secondary batteries manufactured according to the embodiments of this application on the performance of electrochemical devices are characterized based on specific embodiments. However, it should be noted that the scope of protection of this application is defined by the claims and is not limited to the specific embodiments described above.

[0086] Example

[0087] Unless otherwise stated, all raw materials used in this invention are of analytical grade, and all water is deionized water.

[0088] 1. Preparation of positive electrode sheet

[0089] (1) Lithium iron phosphate system

[0090] 10% by weight of polyvinylidene fluoride was dissolved in N-methylpyrrolidone solvent as a binder, and 80% by weight of lithium iron phosphate positive electrode active material and 10% by weight of conductive carbon black were added to prepare a uniformly dispersed positive electrode slurry. The positive electrode slurry was uniformly coated on the surface of aluminum foil current collector, transferred to a vacuum oven for thorough drying, and the obtained positive electrode sheet was rolled and punched to obtain the target positive electrode disc.

[0091] (2) Tripartite system

[0092] 10% by weight of polyvinylidene fluoride binder was dissolved in N-methylpyrrolidone (NMP) solvent and stirred until homogeneous to form a binder solution. 80% by weight of nickel-cobalt-manganese (or nickel-cobalt-aluminum) ternary cathode material was added as the cathode active material, followed by 10% by weight of conductive carbon black. These components were thoroughly mixed with the binder solution and stirred until uniformly dispersed to form a cathode slurry. The cathode slurry was uniformly coated onto the surface of an aluminum foil current collector. The coated aluminum foil was transferred to a vacuum oven, and the resulting cathode sheet was compacted using a roller press to obtain a circular cathode sheet of suitable size.

[0093] 2. Preparation of negative electrode sheet

[0094] (1) Graphite-based

[0095] Dissolve 10% by weight of polyvinylidene fluoride binder in a suitable solvent. Add 80-90% by weight of graphite powder as the negative electrode active material. Select a suitable conductive agent (such as carbon black, acetylene black, or conductive carbon fiber) and add it to the negative electrode slurry; the amount of conductive agent is usually 5-10% by weight. Mix the graphite, binder, and conductive agent thoroughly and stir until uniformly dispersed to form the negative electrode slurry. Coat the prepared negative electrode slurry uniformly onto a copper foil current collector to obtain a cured negative electrode layer. After drying, the negative electrode sheet is compacted using a roller press, then rolled, punched, and cut to form negative electrode sheets of the specified shape and size. Common shapes include circular and rectangular sheets.

[0096] 3. Preparation of the separating membrane

[0097] Polypropylene porous polymer film is used as the separator.

[0098] 4. Preparation of electrolytes

[0099] (1) Lithium iron phosphate system

[0100] Under an Ar atmosphere, fully dried fluorinated salts (see Tables 1 and 3 for details, LiFSI and / or LiTFSI) are dissolved in organic solvents (see Tables 1 and 3, FSA, TFSPD or TFSMP), stirred thoroughly to prepare electrolytes.

[0101] (2) Tripartite system

[0102] Under an Ar atmosphere, fully dried fluorinated salts (see Tables 1 and 3 for details, LiFSI and / or LiTFSI) are dissolved in organic solvents (see Tables 1 and 3, FSA, TFSPD or TFSMP), and an overcharge protectant is added. The mixture is stirred thoroughly to prepare an electrolyte.

[0103] 5. Preparation of button cells

[0104] Stack the positive electrode, separator, and negative electrode in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. Add the electrolyte to assemble a coin cell.

[0105] The electrolytes used in Examples 1-18 and Comparative Examples 1-16 were prepared according to the above preparation method. The specific parameters of the electrolyte formulations are shown in Tables 1 and 3.

[0106] Table 1: Battery cells containing electrolyte and lithium iron phosphate cathode

[0107]

[0108] Table 2

[0109]

[0110] As shown in Table 2, the capacity retention rate of the batteries prepared in Examples 1-12 after 2000 cycles at room temperature is higher than 88%, which is comparable to that of the batteries prepared in Comparative Examples 1-10, and even generally slightly better than that of Comparative Examples 1-10. This is mainly due to the high solubility of FSA solvent in the electrolyte, which improves the conductivity of the electrolyte after addition, and the SEI film formed has better ion conductivity.

[0111] Moreover, the high-temperature capacity retention and recovery rates of the batteries prepared in Examples 1-12 are improved to a certain extent. This is mainly due to the high thermal stability of the FSA solvent and its ability to participate in the formation of the negative electrode SEI film inside the battery. The formed SEI film has better stability, thus making the battery more stable in high-temperature environments.

[0112] The batteries prepared in Examples 1-12 all passed the overcharge test: no leakage, no fire, and no explosion. In Comparative Examples 1-4, the amount of organic solvent used in the electrolyte was too low, resulting in failure to pass the overcharge test. In Comparative Examples 5-6, although aluminum-based materials electrically connected to the positive electrode were included, the electrolytes did not contain solvents such as FSA, and therefore also failed the overcharge test. In Comparative Examples 7-10, although the electrolytes contained solvents such as FSA, the lack of aluminum-based materials electrically connected to the positive electrode prevented them from passing the overcharge test.

[0113] Table 3: Battery cells containing electrolyte (including voltage additives) and ternary active material positive electrode

[0114]

[0115] Table 4

[0116]

[0117] As shown in Table 4, the capacity retention rate of the batteries prepared in Examples 13-18 after 2000 cycles at room temperature is higher than 86%, which is comparable to the capacity retention rate of the batteries prepared in Comparative Examples 11-16 after 2000 cycles at room temperature, and is even generally slightly better than that of Comparative Examples 11-16.

[0118] Moreover, the high-temperature capacity retention and recovery rates of the batteries prepared in Examples 13-18 are improved to a certain extent. This is mainly due to the high thermal stability of the FSA or TFSPD solvents, which can participate in the formation of the negative electrode SEI film in the battery. The formed SEI film has better stability, thus making the battery more stable in high-temperature environments.

[0119] The batteries prepared in Examples 13-18 all passed the overcharge test: no leakage, no fire, and no explosion. In Comparative Examples 11-12, the overcharge test was still failed due to the low amount of FSA or TFSPD solvent in the electrolyte. In Comparative Examples 13-14, although aluminum-based materials electrically connected to the positive electrode were included, the electrolyte did not contain solvents such as FSA, and therefore also failed the overcharge test. In Comparative Examples 15-16, although the electrolyte contained solvents such as FSA, the lack of aluminum-based materials electrically connected to the positive electrode prevented the overcharge test from being passed.

[0120] In summary, by adding an organic solvent such as FSA to the electrolyte and combining it with an aluminum-based current collector and / or tabs at the positive electrode, in a lithium iron phosphate battery system, when overcharging occurs, a rapid electrochemical oxidation reaction occurs between the aluminum-based current collector and / or tabs and solvents such as FSA, generating corrosion that prevents the reaction from continuing and thus prevents the overcharge voltage from rising further, thereby avoiding abnormal and dangerous situations caused by overcharging.

[0121] Because the positive electrode uses a ternary nickel-cobalt-manganese active material, although overcharge protection can be achieved, its energy advantage cannot be fully utilized due to the limitation of the charge / discharge voltage (the actual charge / discharge voltage range of this material in use is 3.0–4.2V). If its actual limit voltage of 4.2V is used, normal charge and discharge cannot be achieved. This is mainly because the aluminum-based current collector material electrically connected to the positive electrode undergoes a continuous and rapid electrochemical reaction with the FSA solvent at 3.7V, preventing charging to the 4.2V cutoff voltage. In other words, before reaching the cutoff voltage, the aluminum-based current collector material has already reacted with the FSA solvent at 3.7V, preventing normal charge and discharge and thus preventing it from reaching the optimal charge / discharge state. For nickel-cobalt-manganese batteries, this results in a decrease in their electrical performance. Therefore, an overcharge protection agent needs to be added to increase the battery's internal resistance during overcharge, achieving overcharge erosion protection within the ternary system. When the battery voltage exceeds the safety threshold (4.2V) of the ternary lithium battery system, the organic solvent will react with the aluminum-based material to form corrosion that can inhibit the electrochemical reaction, thereby disconnecting the battery and preventing the electrochemical reaction from continuing.

[0122] Testing and Standards

[0123] 1. Room temperature cycling test

[0124] At 25°C, the lithium secondary batteries prepared in the examples and comparative examples were subjected to full charge-discharge cycle tests at a 0.5C rate for 2000 cycles, and the capacity retention rate (%) of the batteries relative to their initial capacity was recorded. A higher retention rate indicates better cycle performance of the battery.

[0125] 2. High-temperature storage test

[0126] The lithium secondary batteries of the examples and comparative examples were charged at a constant current rate of 1C to the voltage safety threshold (3.65V for lithium iron phosphate and 4.2V for ternary systems), and then charged at the same voltage to a current of 0.05C. The batteries were then placed in an environment of 55°C for 7 days. After the batteries were removed and placed in a room temperature environment for 8 hours, they were discharged at a constant current rate of 1C to 2.5V. The capacity discharged / battery capacity × 100% was recorded as the high-temperature storage capacity retention rate. The batteries were then charged at a constant current rate of 1C to the voltage safety threshold, and then charged at the same voltage to a current of 0.05C. The batteries were then discharged at a constant current rate of 1C to 2.5V. The capacity discharged / battery capacity × 100% was recorded as the high-temperature storage capacity recovery rate.

[0127] 3. Overcharge test

[0128] At 25°C, the lithium secondary batteries prepared in the examples and comparative examples were charged and discharged at a rate of 0.5C. When the battery charging voltage was below 3.7V, the battery could be charged and discharged normally; when the charging voltage was ≥3.7V, and the voltage rose to 3.7V and then stopped rising until it remained at 3.7V, it indicated that the battery passed the overcharge test. At this time, the FSA solvent of this application reacted with the aluminum-based material, preventing the voltage from rising further and preventing the battery from overcharging; at the same time, the internal fluctuation of the increased current indicated that other reactions occurred inside the battery, namely the reaction between the FSA solvent and the aluminum-based material.

[0129] In a ternary system, the difference between adding and not adding a safety protectant is as follows: Without the overcharge protectant, when the charging voltage is ≥3.7V, it is found that the voltage rises to 3.7V and then stops rising, remaining at 3.7V until the end.

[0130] After adding the battery, it was found that the charging voltage could reach ≥3.7V, up to the theoretical safe voltage of 4.2V for a ternary lithium battery. The voltage then stopped rising after reaching 4.2V and remained at 3.7V until the end, indicating that the battery passed the overcharge test.

[0131] For ternary cathodes using the LiFSI / FSA system Figure 1 The electrolyte in the battery did not contain overcharge protection. When the battery was charged to 3.7V, the aluminum foil underwent an etching reaction, and the battery could not continue charging. Figure 2 The electrolyte in the battery, due to the addition of an overcharge protectant, increases the etching voltage of the aluminum foil to over 4.2V, allowing the battery to be charged to 4.2V and complete a full charge-discharge cycle.

[0132] Although the invention has been described in conjunction with specific embodiments, those skilled in the art will understand that many modifications and variations can be made to the invention. Therefore, it is to be appreciated that the claims are intended to cover all such modifications and variations that fall within the true conception and scope of the invention.

Claims

1. A controllable corrosion-resistant overcharge protection cell, the cell comprising a positive electrode, a negative electrode, and an electrolyte; in, The positive electrode includes a positive electrode tab, a positive electrode current collector, and a positive electrode active material, wherein the positive electrode tab and / or the positive electrode current collector includes an aluminum-containing substrate. The electrolyte contains an organic solvent represented by chemical formula I and / or chemical formula II: In the formula, R 1 Each is independently selected from F, Cl, and C. n H 2n+1 C n H 2n+1-x F x Or any combination thereof, where n = 1-100, x = 1-3; R 2 and R 3 Whether the two are the same or different, each is independently selected from C. n H 2n+1 C n H 2n+1-x F x Or any combination thereof, where n = 1-100, x = 1-3; R 4 Each is independently selected from C k H 2k-q F q Or (CH2) k-1 The annular portion shown in O is given by the formula, where k≥3, q≥0, and q≤2k.

2. The controllable corrosion-resistant overcharge protection core according to claim 1, wherein, The organic solvent represented by chemical formula I is N,N-dimethylaminosulfonyl fluoride; the organic solvent represented by chemical formula II is selected from one or more of the following cyclic organic solvents:

3. The controllable corrosion-resistant overcharge protection core according to claim 1, wherein, The positive electrode active material includes lithium iron phosphate.

4. The controllable corrosion-resistant overcharge protection core according to claim 1, wherein, The positive electrode active material includes a nickel-cobalt-manganese ternary material or a nickel-cobalt-aluminum ternary material, and the electrolyte further contains 0.1-5% by weight of an overcharge protection agent based on the weight of the electrolyte.

5. The controllable corrosion-resistant overcharge protection core according to claim 4, wherein, The overcharge protector is selected from one or more of the following: vinylene carbonate, ethylene ethylene carbonate, fluoroethylene carbonate, 1,3-propanesulfonate lactone, 1,4-butanesulfonate lactone, vinyl sulfate, vinyl sulfite, propylene sulfate, propylene sulfite, butene sulfate, and lithium difluorophosphate.

6. The controllable corrosion-resistant overcharge protection core according to claim 1, wherein, The aluminum-containing substrate is selected from aluminum foil, aluminum alloy, aluminized steel foil, aluminum-coated composite material, carbon-coated aluminum foil, nanostructured aluminum material, aluminum-containing conductive polymer composite material, or a combination thereof.

7. The controllable corrosion-resistant overcharge protection core according to claim 1, wherein, The amount of the organic solvent is 30%-95% based on the mass of the electrolyte.

8. The controllable corrosion-resistant overcharge protection core according to claim 1, wherein, The electrolyte also contains lithium salts, preferably LiFSI and / or LiTFSI.

9. The controllable corrosion-resistant overcharge protection core according to claim 1, wherein, The negative electrode includes a negative electrode tab, a negative electrode current collector, and a negative electrode active material located on the negative electrode current collector; the negative electrode active material includes graphite material and optional conductive agent and binder; wherein the graphite material is selected from one or more combinations of natural graphite, artificial graphite, mesophase carbon microspheres (MCMB), hard carbon, silicon alloy, and silicon-carbon.

10. A secondary battery comprising the cell according to any one of claims 1-9.

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