Electrolyte, battery, battery pack and electronic equipment

Abstract

The invention provides an electrolyte, a battery, a battery pack and electronic equipment, the electrolyte comprises an electrolyte salt, and the electrolyte salt comprises a halogen main salt and an auxiliary salt; the auxiliary salt comprises an organic acid ligand doped borate derivative. According to the electrolyte prepared by the preparation method, the conductivity and the stability of the electrolyte can be considered at the same time.

Description

Technical Field

[0001] The present invention relates to the technical field of ion batteries, and in particular to an electrolyte, a battery, a battery pack and an electronic device. Background Art

[0002] In the field of large-scale energy storage, ion batteries have attracted widespread attention from technicians due to their high energy density and low cost. However, the electrolytes used in traditional ion batteries often cannot provide both high conductivity and thermal stability. For example, halogen salts such as hexafluorophosphate as electrolytes have high conductivity but need to improve thermal stability, which in turn affects the battery's cycling stability. On the other hand, borates as electrolytes have high thermal stability but their ionic conductivity cannot meet the requirements of fast charging, which in turn affects the cycling performance of ion batteries.

[0003] Therefore, it is necessary to develop an electrolyte that can balance electrical conductivity and thermal stability to improve the cycle performance of ion batteries. Summary of the Invention

[0004] The present invention provides an electrolyte. The prepared electrolyte can take into account both the conductivity and stability of the electrolyte and improve the cycle performance of the battery.

[0005] The present invention provides a battery and a battery pack. The prepared battery or battery pack has excellent cycle performance.

[0006] The present invention provides an electronic device. The prepared electronic device has a long service life and meets quality assurance requirements.

[0007] One aspect of the present invention provides an electrolyte solution, comprising an electrolyte salt; the electrolyte salt comprises a halogen-based main salt and an auxiliary salt; the auxiliary salt comprises a borate derivative doped with an organic acid ligand.

[0008] According to one embodiment of the present invention, the molar ratio of the halogen main salt to the auxiliary salt is (7-9.5):(0.5-3).

[0009] According to one embodiment of the present invention, the organic acid ligand includes one or more of oxalic acid, malonic acid, succinic acid, o- / m- / terephthalic acid, cis- / fumaric acid, tartaric acid, cyclohexanedicarboxylic acid, dimercaptosuccinic acid, 1,5-naphthalene disulfonic acid or aspartic acid; and / or the halogen main salt includes one or more of hexafluorophosphate, perchlorate, bis(fluorosulfonic acid)imide salt or bis(trifluoromethylsulfonyl)imide salt.

[0010] According to one embodiment of the present invention, the electrolyte further includes an ester solvent and / or a phosphazene additive; wherein the ester solvent includes one or more of polycarbonate, ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate or diethyl carbonate; and / or the phosphazene additive includes one or more of ethoxypentafluorocyclotriphosphazene, methoxypentafluorocyclotriphosphazene, hexafluorocyclotriphosphazene or phenoxycyclotriphosphazene.

[0011] According to one embodiment of the present invention, the molar ratio of the electrolyte salt, the ester solvent and the phosphazene additive is 1:(3-8):(1-6).

[0012] According to one embodiment of the present invention, the organic acid ligand-doped borate derivative is prepared by a method comprising the following processes: after mixing an organic acid ligand, a metal hydroxide and boric acid, performing a first reaction and a second reaction in sequence to obtain the organic acid ligand-doped borate derivative; the reaction temperature of the first reaction is lower than the reaction temperature of the second reaction.

[0013] According to one embodiment of the present invention, the molar ratio of the organic acid ligand, the metal hydroxide and the boric acid is (1-3):1:1; and / or the reaction temperature of the first reaction is 100°C-120°C, and the reaction time is 4h-8h; and / or the reaction temperature of the second reaction is 200°C-300°C, and the reaction time is 4h-8h.

[0014] According to one embodiment of the present invention, the electrolyte is a lithium salt electrolyte, the cations in the halogen main salt are lithium ions, and the auxiliary salt includes LiBOB doped with an organic acid ligand; and / or, the electrolyte is a sodium salt electrolyte, the cations in the halogen main salt are sodium ions, and the auxiliary salt includes NaBOB doped with an organic acid ligand.

[0015] Another aspect of the present invention provides a battery comprising the above-mentioned electrolyte.

[0016] Another aspect of the present invention provides a battery pack, comprising the above-mentioned battery.

[0017] Another aspect of the present invention provides an electronic device comprising the above-mentioned battery or the above-mentioned battery pack.

[0018] The electrolyte provided by the present invention can balance the ionic conductivity and stability of the electrolyte by adopting the synergistic effect of a halogen-based primary salt and a secondary salt, thereby improving the cycling performance of the ion battery. The use of a borate derivative doped with an organic acid ligand as a secondary salt can not only improve its own solubility and ionic conductivity, but also anchor free solvent molecules through the strong complexation between the organic ligand and the metal ion, reducing the occurrence of side reactions and thus improving the thermal stability of the electrolyte. At the same time, combined with a halogen-based primary salt with high ionic conductivity, the conductivity of the electrolyte can be further improved, thereby improving the cycling performance of the battery. DETAILED DESCRIPTION

[0019] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0020] As previously mentioned, halogen salts such as hexafluorophosphate have advantages in improving electrolyte ionic conductivity, while borates have advantages in improving electrolyte thermal stability. The inventors of this application attempted to combine halogen salts and borates to further improve the cycling performance of ion batteries. However, the effect of combining halogen salts and borates was not as expected.

[0021] The inventors speculate that the composite electrolyte's performance may be less than expected due to the low solubility of borates in the electrolyte solvent. Therefore, the inventors focused on improving and optimizing the solubility of borates, hoping to achieve an electrolyte that balances ionic conductivity and stability. Based on this, the first aspect of the present invention provides an electrolyte comprising an electrolyte salt, the electrolyte salt comprising a halogen-based primary salt and a secondary salt; the secondary salt comprising a borate derivative doped with an organic acid ligand.

[0022] Among them, the halogen main salt refers to the salt compound containing halogen (fluorine or chlorine, etc.) commonly used in the art, and the borate derivative doped with organic acid ligand refers to the compound obtained by doping and coordinating borate with the anion of organic acid as a ligand.

[0023] It should be noted that the cations in the halogen main salt of the present invention can be active metal ions such as sodium ions, lithium ions or potassium ions. The specific selection can be determined according to the battery used for the electrolyte. For example, when the battery is a sodium ion battery, the cations in the halogen main salt are sodium ions; similarly, in the borate derivative doped with an organic acid ligand, the cations can be active metal ions such as sodium ions, lithium ions or potassium ions. The specific selection can be determined according to the battery used for the electrolyte.

[0024] The electrolyte of the present invention can take into account both high ionic conductivity and thermal stability. The ion battery prepared from this electrolyte has excellent cycle performance. The reason is that, on the one hand, the halogen main salt has a high ionic conductivity. On the other hand, doping the organic acid ligand with a borate derivative as an auxiliary salt can improve the solubility of the borate in the electrolyte solvent, thereby helping to improve the ionic conductivity of the borate derivative. At the same time, the strong complexation effect of the organic acid ligand is utilized to anchor the free solvent molecules in the electrolyte, reducing the occurrence of side reactions, which can further improve the thermal stability of the borate derivative and thus improve the thermal stability of the electrolyte. That is, the electrolyte prepared by the synergistic combination of the halogen main salt and the auxiliary salt of the present invention not only has excellent ionic conductivity, but also has excellent thermal stability. The ion battery prepared from this electrolyte has excellent cycle performance.

[0025] In order to further improve the ionic conductivity and thermal stability of the electrolyte, the molar ratio of the halogen main salt and the auxiliary salt can be further regulated. In some embodiments, the molar ratio of the halogen main salt and the auxiliary salt is (7-9.5): (0.5-3), and illustratively, the molar ratio of the halogen main salt and the auxiliary salt can be 7:0.5, 8:0.5, 9:0.5, 9.5:0.5, 7:1, 8:1, 9:1, 9.5:1, 7:2, 8:2, 9:2, 9.5:2, 7:3, 8:3, 9:3 or 9.5:3, etc.

[0026] According to the inventors' research, the molar ratio of the halogen primary salt to the auxiliary salt in the aforementioned electrolyte affects the electrolyte's ionic conductivity and thermal stability. Within a specific range of molar ratios, a moderate ratio of the halogen primary salt to the auxiliary salt can not only further reduce the probability of side reactions and improve the electrolyte's thermal stability, but also further enhance the electrolyte's ionic conductivity. Consequently, ion batteries prepared using this electrolyte exhibit excellent cycling performance.

[0027] In order to further improve the ionic conductivity and thermal stability of the borate derivative doped with an organic acid ligand, the type of organic acid ligand can be further optimized. The organic acid ligand includes one or more of oxalic acid, malonic acid, succinic acid, o- / m- / terephthalic acid, cis- / fumaric acid, tartaric acid, cyclohexanedicarboxylic acid, dimercaptosuccinic acid, 1,5-naphthalenedisulfonic acid, or aspartic acid.

[0028] According to the inventors' research, the specific organic acids defined in this invention exhibit strong complexing properties, reacting with free solvent molecules in the electrolyte to form organic complexes, thereby anchoring the free solvent molecules in the electrolyte. This effectively inhibits side reactions in the electrolyte during battery cycling, thereby improving the thermal stability of the electrolyte.

[0029] There are many types of halogen main salts. In order to ensure high ionic conductivity of the electrolyte, it is necessary to further limit the types of halogen main salts. In some embodiments of the present invention, the halogen main salt includes one or more of hexafluorophosphate, perchlorate, bis(fluorosulfonyl)imide salt or bis(trifluoromethylsulfonyl)imide salt.

[0030] In addition to the electrolyte salt, the electrolyte solution further includes an ester solvent and / or a phosphazene additive.

[0031] Furthermore, the ester solvent includes one or more of polycarbonate, ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate or diethyl carbonate.

[0032] Among them, the standardized abbreviation of polycarbonate is PC, the standardized abbreviation of ethylene carbonate is EC, the standardized abbreviation of ethyl methyl carbonate is EMC, the standardized abbreviation of dimethyl carbonate is DMC, and the standardized abbreviation of diethyl carbonate is DEC.

[0033] In order to further improve the ionic conductivity and thermal stability of the electrolyte, the composition of the ester solvent may be further limited. The ester solvent includes polycarbonate, ethylene carbonate and dimethyl carbonate.

[0034] When the ester solvent includes polycarbonate, ethylene carbonate and dimethyl carbonate, the volume ratio of the polycarbonate, ethylene carbonate and dimethyl carbonate can be (2-3):1:(6-7). For example, the volume ratio of polycarbonate, ethylene carbonate and dimethyl carbonate can be 2:1:6, 2:1:7, 3:1:6 or 3:1:7, etc.

[0035] Meanwhile, the ester solvent may also include other combinations, that is, the ester solvent includes polycarbonate, ethylene carbonate and diethyl carbonate.

[0036] When the ester solvent includes polycarbonate, ethylene carbonate and diethyl carbonate, the volume ratio of the polycarbonate, ethylene carbonate and diethyl carbonate can be (2-3):1:(6-7). For example, the volume ratio of polycarbonate, ethylene carbonate and diethyl carbonate can be 2:1:6, 2:1:7, 3:1:6 or 3:1:7, etc.

[0037] On the other hand, the ester solvent may also be composed of other components, that is, the ester solvent includes polycarbonate and ethylene carbonate.

[0038] When the ester solvent includes polycarbonate and ethylene carbonate, the volume ratio of polycarbonate to ethylene carbonate can be (2-3):(6-7). For example, the volume ratio of polycarbonate to ethylene carbonate can be 2:6, 2:7, 3:6 or 3:7, etc.

[0039] In the application scenarios of existing ion batteries, ion batteries are required not only to have excellent cycle performance, but also to have excellent safety performance. Among the safety performance, the improvement of thermal stability will not only increase the service life of the battery, but also further prevent the occurrence of thermal runaway, which is the research focus of technical personnel in this field.

[0040] Based on this, the present invention utilizes phosphazene additives based on the synergistic combination of a halogen-based primary salt and a secondary salt. Phosphazene additives not only effectively inhibit the decomposition of the electrolyte and interfacial side reactions, preventing gas production caused by these side reactions, but also improve the thermal stability of the electrolyte without sacrificing ionic conductivity.

[0041] Furthermore, the phosphazene additive includes one or more of ethoxypentafluorocyclotriphosphazene, methoxypentafluorocyclotriphosphazene, hexafluorocyclotriphosphazene or phenoxycyclotriphosphazene.

[0042] The standardized abbreviation of ethoxypentafluorocyclotriphosphazene is PFPN.

[0043] According to the inventors' research, the introduction of phosphazene additives into the above-mentioned electrolyte not only helps to form a composite passivation film at the electrode-electrolyte interface, scavenges O and H free radicals, and improves battery safety by blocking the exothermic chain reaction between the electrolyte and the electrode, but also can cooperate with conventional additives to reduce the impedance of the SEI film, block the exothermic chain reaction between the electrolyte and the electrode, increase the thermal runaway starting temperature, and improve the safety of the ion battery.

[0044] In order to further improve the ionic conductivity and thermal stability of the electrolyte, the composition of the electrolyte can also be limited. The molar ratio of the electrolyte salt, the ester solvent, and the phosphazene additive is 1:(3-8):(1-6). For example, the molar ratio of the electrolyte salt, the ester solvent, and the phosphazene additive can be 1:3:1, 1:5:1, 1:7:1, 1:8:1, 1:3:3, 1:5:3, 1:7:3, 1:8:3, 1:3:5, 1:5:5, 1:7:5, 1:8:5, 1:3:6, 1:5:6, 1:7:6, or 1:8:6, etc.

[0045] According to the inventors' research, the molar ratio of the electrolyte salt, ester solvent, and additive in the above-mentioned electrolyte affects the electrochemical and safety performance of the electrolyte. Within the preferred molar ratio range, the exothermic reaction between the electrolyte and the negative electrode is mild, further improving the thermal stability of the electrolyte. Furthermore, within this preferred molar ratio range, the concentration of the active component in the electrolyte is moderate, thereby ensuring a moderate ionic conductivity of the electrolyte, which is beneficial for further improving the ionic conductivity of the electrolyte and, in turn, the cycling performance of the ion battery.

[0046] In some embodiments, the preparation method of the organic acid ligand-doped borate derivative comprises the following steps: after mixing the organic acid ligand, metal hydroxide and boric acid, performing a first reaction and a second reaction in sequence to obtain the organic acid ligand-doped borate derivative; the reaction temperature of the first reaction is lower than the reaction temperature of the second reaction.

[0047] Specifically, the metal cation in the metal hydroxide is selected based on the application scenario of the electrolyte. For example, when the electrolyte is used in lithium-ion batteries, lithium hydroxide is used as the metal hydroxide to prepare a lithium borate derivative doped with an organic acid ligand; when the electrolyte is used in sodium-ion batteries, sodium hydroxide is used as the metal hydroxide to prepare a sodium borate derivative doped with an organic acid ligand.

[0048] In the present invention, a partial reaction occurs during the first reaction, removing some moisture from the raw materials. The remaining moisture evaporates relatively slowly at the reaction temperature of the first reaction. The presence of a small amount of water can, to a certain extent, inhibit the loss of the organic acid. Furthermore, in the second reaction, further increasing the reaction temperature not only accelerates the reaction rate but also promotes complete reaction. Furthermore, during the first reaction, byproducts such as organic acid salts or metaboric acid may be produced. By increasing the reaction temperature, these byproducts can be further converted into borate derivatives doped with organic acid ligands.

[0049] According to the inventors' research, the solid-phase synthesis method is used to prepare organic ligand-doped borate derivatives, which can reduce the preparation cost on the one hand, and reduce the loss of metal ions Na or Li on the other hand, thereby improving the utilization rate of raw materials.

[0050] In order to further improve the mixing effect and ensure the purity of the borate derivative doped with the organic acid ligand, the mixing method can be further limited. The mixing method includes dry mixing.

[0051] Furthermore, the mixing method includes spheroidal ink mixing.

[0052] In the embodiment of the present invention, the mixing speed of the spherical ink, the ratio of the balls to the materials, the mixing temperature or the mixing time are conventional washing methods in the art and are not particularly limited thereto.

[0053] In order to further improve the purity of the borate derivative doped with the organic acid ligand, the mixed raw material can be limited, and the molar ratio of the organic acid ligand, the metal hydroxide and the boric acid is (1-3):1:1. For example, the molar ratio of the organic acid ligand, the metal hydroxide and the boric acid can be 1:1:1, 1:1.5:1, 1:2:1, 1:2.5:1 or 1:3:1, etc.

[0054] Wherein, the metal hydroxide includes sodium hydroxide or lithium hydroxide.

[0055] To further improve the purity of the borate derivative doped with the organic acid ligand, the reaction temperature and reaction time of the first reaction and the second reaction may also be limited. The reaction temperature of the first reaction is 100° C. to 120° C., and the reaction time is 4 to 8 hours. For example, the reaction temperature of the first reaction is 100° C., 105° C., 110° C., 115° C., or 120° C., and the reaction time of the first reaction is 4 hours, 5 hours, 6 hours, 7 hours, or 8 hours.

[0056] At the same time, the reaction temperature of the second reaction is 200°C-300°C, and the reaction time is 4h-8h. Exemplarily, the reaction temperature of the second reaction is 200°C, 220°C, 240°C, 260°C, 280°C or 300°C, and the reaction time of the second reaction is 4h, 5h, 6h, 7h or 8h, etc.

[0057] After the first reaction and the second reaction are completed, the product may be washed and dried.

[0058] Furthermore, the washing detergent includes ethanol.

[0059] In the embodiment of the present invention, the washing method is a conventional washing method in the art, and the number of washing times and the criteria for determining the washing endpoint can also be obtained by those skilled in the art through limited experiments and are not particularly limited thereto.

[0060] At the same time, the drying conditions are further limited, and the drying insulation temperature is 50°C-80°C. Exemplarily, the drying insulation temperature is 50°C, 60°C, 70°C, 75°C or 80°C.

[0061] In an embodiment of the present invention, the endpoint of the drying includes complete evaporation of the detergent.

[0062] In summary, the electrolyte is a lithium salt electrolyte, the cations in the halogen main salt are lithium ions, and the auxiliary salt includes LiBOB doped with an organic acid ligand; and / or the electrolyte is a sodium salt electrolyte, the cations in the halogen main salt are sodium ions, and the auxiliary salt includes NaBOB doped with an organic acid ligand.

[0063] Furthermore, the electrolyte is a lithium salt electrolyte, and the halogen main salt includes one or more of lithium hexafluorophosphate, lithium perchlorate, lithium bisfluorosulfonimide or lithium bistrifluoromethylsulfonyl imide; and / or, the electrolyte is a sodium salt electrolyte, and the halogen main salt includes one or more of sodium hexafluorophosphate, sodium perchlorate, sodium bisfluorosulfonimide or sodium bistrifluoromethylsulfonyl imide.

[0064] A second aspect of the present invention provides a method for preparing an electrolyte, comprising the following steps: stirring and mixing the electrolyte salt, an ester solvent, and a phosphazene additive to prepare the electrolyte.

[0065] In the embodiments of the present invention, the stirring and mixing device, the stirring and mixing speed, the stirring and mixing time, etc. can be obtained by those skilled in the art through limited experiments and are not particularly limited thereto.

[0066] A third aspect of the present invention provides a battery, comprising the above-mentioned electrolyte or the electrolyte prepared according to the above-mentioned preparation method.

[0067] In some embodiments, when the electrolyte is a lithium salt electrolyte, the battery is a lithium ion battery.

[0068] In some embodiments, when the electrolyte is a sodium salt electrolyte, the battery is a sodium ion battery.

[0069] Generally, a battery consists of an electrolyte, a cell, and an aluminum-plastic film encapsulating the cell. The electrolyte is injected into the dry cell within the aluminum-plastic film. The cell includes a positive electrode sheet, a negative electrode sheet, and a separator located between the positive and negative electrodes. The cell can be a laminated cell, meaning that the cell is constructed by alternating positive electrode sheets, separators, and negative electrode sheets.

[0070] In an embodiment of the present invention, the positive electrode sheet includes a positive electrode current collector and a positive electrode active layer located on at least one side surface of the positive electrode current collector. Specifically, the positive electrode active layer can be provided on one side surface of the positive electrode current collector in the thickness direction, or the positive electrode active layer can be provided on both sides of the positive electrode current collector in the thickness direction.

[0071] In an embodiment of the present invention, the positive electrode active layer may include a positive electrode active material, a conductive agent and a binder. In the positive electrode active layer, the mass percentage of the positive electrode active material may be 70% to 99%, for example, 70%, 75%, 80%, 85%, 90%, 93%, 95%, 97%, 99% or a range consisting of any two thereof; the mass fraction of the conductive agent may be 0.5% to 15%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 8%, 10%, 13%, 15% or a range consisting of any two thereof; the mass fraction of the binder may be 0.5% to 15%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 8%, 10%, 13%, 15% or a range consisting of any two thereof.

[0072] In embodiments of the present invention, the positive electrode active material may include one or more of sodium iron phosphate, sodium vanadium phosphate, sodium iron sulfate, sodium nickel iron manganate, or sodium vanadium fluorophosphate. These positive electrode active materials have high energy density, and the use of these materials as positive electrode active materials in the present invention is beneficial for improving the energy storage capacity of the battery.

[0073] In embodiments of the present invention, the positive electrode active material may include one or more of lithium iron phosphate, lithium vanadium phosphate, lithium iron sulfate, lithium nickel iron manganese oxide, or lithium vanadium fluorophosphate. These positive electrode active materials have high energy density, and the use of these materials as positive electrode active materials in the present invention is beneficial for improving the energy storage capacity of the battery.

[0074] In embodiments of the present invention, the conductive agent in the positive electrode active layer may be a conventional conductive material in the art. For example, the conductive agent in the positive electrode active layer may include one or more of conductive carbon black, conductive graphite, carbon nanotubes (CNTs), carbon fibers, graphene, acetylene black, or Ketjen black. Such conductive agents provide the battery of the present invention with good electrical conductivity and mechanical strength, thereby improving the overall performance of the battery.

[0075] In an embodiment of the present invention, the binder in the positive electrode active layer may be a conventional binding material in the art. For example, the binder in the positive electrode active layer may include one or more of polyvinylidene fluoride (PVDF), polyvinylidene fluoride, polyvinyl fluoride, polyethylene, polypropylene, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, ethylene oxide-containing polymers, polyvinyl pyrrolidone, or polyurethane. The present invention uses a binder to provide a bonding effect between the positive electrode active material and the conductive agent, thereby ensuring the mechanical stability and ion conductivity of the electrode material during charge and discharge cycles.

[0076] In the embodiment of the present invention, a conventional positive electrode current collector in the art may be used. For example, the positive electrode current collector includes aluminum foil.

[0077] In the embodiments of the present invention, the positive electrode sheet can be prepared by conventional methods in the art, such as a coating method. Specifically, the components used to form the positive electrode active layer, such as the positive electrode active material, conductive agent, and binder, can be dispersed in a solvent, such as N-methylpyrrolidone (NMP), to prepare a positive electrode slurry, which is then coated on the surface of the positive electrode current collector. After drying and roller pressing, the positive electrode sheet is prepared. The coating, drying, and roller pressing steps involved are conventional operations for preparing positive electrode sheets using the coating method and are not particularly limited thereto.

[0078] In an embodiment of the present invention, a negative electrode active layer may be provided on one surface of the negative electrode current collector in the thickness direction, or on two opposite surfaces of the negative electrode current collector in the thickness direction.

[0079] In an embodiment of the present invention, the negative electrode active layer may include a negative electrode active material, a conductive agent, and a binder. In the negative electrode active layer, the mass percentage of the negative electrode active material may be 80% to 99%, for example, but not limited to, 80%, 82%, 85%, 88%, 90%, 92%, 95%, 98%, 99%, or a range consisting of any two thereof; the mass percentage of the conductive agent may be 0.5% to 5%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or a range consisting of any two thereof; the mass fraction of the binder may be 0.5% to 15%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 8%, 10%, 13%, 15%, or a range consisting of any two thereof.

[0080] In an embodiment of the present invention, the negative electrode active layer includes at least one or more of graphite, silicon, tin, or lithium titanate. These negative electrode active materials have excellent electrical conductivity and, as negative electrode active materials, are beneficial for improving the electrochemical performance and safety of the battery.

[0081] In an embodiment of the present invention, the binder in the negative electrode active layer may be any binder suitable for the negative electrode known in the art. For example, the binder in the negative electrode active layer may include polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC), tetrafluoroethylene and its copolymers, polyvinylidene fluoride and its copolymers, polyolefins and their copolymers (e.g., polyethylene-polyethylene glycol block copolymers, etc.), polyethers and their copolymers (e.g., polyethylene oxide, etc.), polyphenylene ethers and their copolymers, polysiloxanes and their copolymers (e.g., polydimethylsiloxane, poly(dimethylsiloxane-co-alkylmethylsiloxane), etc.), polyesters and their copolymers (e.g., polyvinyl esters, polyvinyl acetate, polyacrylates, etc.), carboxymethyl cellulose, styrene-butadiene latex, nitrile rubber or polyacrylic acid (PAA). At least one of these. Specifically, the polyolefin includes one or more of polyethylene, polypropylene, ethylene / propylene copolymer, ethylene / vinylidene fluoride copolymer, or propylene / vinylidene fluoride copolymer; polytetrafluoroethylene and its copolymers can be at least one of tetrafluoroethylene / ethylene copolymer, tetrafluoroethylene / propylene copolymer, tetrafluoroethylene / vinylidene fluoride copolymer, tetrafluoroethylene / ether copolymer, tetrafluoroethylene / branched polyether copolymer, tetrafluoroethylene / vinyl ether copolymer, tetrafluoroethylene / branched polyether / vinyl ether copolymer, or tetrafluoroethylene / siloxane copolymer. The present invention utilizes a binder to provide a bond between the negative electrode active material and the conductive agent, ensuring mechanical stability and ion conductivity of the electrode material during charge and discharge cycles.

[0082] In embodiments of the present invention, the conductive agent in the negative electrode active layer may be a conventional conductive material in the art. For example, the conductive agent in the negative electrode active layer may include one or more of hard carbon, conductive carbon black, conductive graphite, carbon nanotubes (CNTs), carbon fibers, graphene, acetylene black, or Ketjen black. These conductive agents provide the battery of the present invention with excellent electrical conductivity and mechanical strength, thereby improving the overall performance of the battery.

[0083] The embodiment of the present invention may use a conventional negative electrode current collector in the art, for example, the negative electrode current collector includes copper foil.

[0084] For example, in a specific implementation, a negative electrode current collector with a primer (such as copper foil) can be used, that is, the surface of the negative electrode current collector has a primer, and then the negative electrode membrane used to form the negative electrode active layer is pressed onto the negative electrode current collector, that is, the negative electrode membrane is bonded to the negative electrode current collector through the primer to obtain a negative electrode sheet (the primer forms the bonding layer of the negative electrode sheet).

[0085] In embodiments of the present invention, the negative electrode sheet can be produced by a dry process (i.e., rolling the material for forming the negative electrode active layer into a film and then compounding it with the negative electrode current collector to produce the negative electrode sheet), or by a wet process (coating method) (i.e., applying the negative electrode slurry for forming the negative electrode active layer to the surface of the negative electrode current collector, followed by drying, rolling, and other steps to form a negative electrode active layer on the surface of the negative electrode sheet to produce the negative electrode sheet). The coating, drying, rolling, and other steps involved are conventional operations for producing negative electrode sheets using the coating method and are not particularly limited thereto.

[0086] In an embodiment of the present invention, the electrolyte of the battery includes the electrolyte described above, and the electrolyte includes an electrolyte salt, and the electrolyte salt includes a halogen main salt and an auxiliary salt.

[0087] In the embodiment of the present invention, the separator is used to separate the positive electrode sheet and the negative electrode sheet to prevent the positive electrode sheet and the negative electrode sheet from short-circuiting. The embodiment of the present invention can adopt conventional separators in the art and is not particularly limited thereto.

[0088] In the embodiment of the present invention, conventional aluminum-plastic film materials in the art may be used to encapsulate the battery cell, and there is no particular limitation on this.

[0089] In the embodiments of the present invention, components such as positive electrode sheets, separators, and negative electrode sheets can be assembled into a battery by conventional methods in the art. For example, the positive electrode sheets, separators, and negative electrode sheets can be staggered and stacked to produce a laminated battery cell; the battery cell is then placed in an aluminum-plastic film (outer packaging), and after conventional processes such as liquid injection (i.e., injecting electrolyte) and packaging, a battery precursor is produced; the battery precursor is then subjected to aging (standing) treatment, formation treatment, aging treatment, lithium supplement agent decomposition treatment, secondary liquid injection treatment, and subsequent capacity division and other processes to produce a battery.

[0090] In the embodiment of the present invention, the processes involved, such as liquid injection, sealing, aging, formation, aging treatment, and capacity separation, are all conventional battery assembly processes in the art and are not particularly limited thereto.

[0091] A fourth aspect of the present invention provides a battery pack comprising the above-described battery. In the battery pack described above, multiple batteries are connected in series, in parallel, or in a combination of series and parallel to form a modular system, without particular limitation. The battery pack is widely used in electric vehicles, energy storage systems, portable electronic devices, and other fields, and exhibits a long battery life.

[0092] A fifth aspect of the present invention provides an electronic device, which includes the above-mentioned battery or the above-mentioned battery pack. The invention does not specifically limit the type of electronic device, such as power equipment (such as electric vehicles, electric vehicles), electronic equipment (such as mobile phones, tablet computers, laptops, digital cameras, etc.), wearable devices (such as watches, bracelets, VR glasses, etc.) or energy storage power stations, etc. By using the battery as described above in an electronic device, electric energy can be continuously and stably output to supply the electronic device for use, so that the electronic device has a longer service life, and at the same time, the maintenance of the battery in the electronic device can be reduced, which is conducive to cost saving.

[0093] The present invention is further described below through specific examples.

[0094] Example 1

[0095] The preparation of the electrolyte in this embodiment includes the following steps:

[0096] 1) Preparation of auxiliary salt NaBOB derivatives:

[0097] Phthalic acid, NaOH, and boric acid were mixed in a dry process in a molar ratio of 2:1:1, and the mixture was first reacted at 110°C for 6 hours, and then at 240°C for 6 hours. The mixture was then washed with ethanol and dried at 60°C until the ethanol was completely evaporated to obtain the auxiliary salt NaBOB derivative.

[0098] 2) Preparation of electrolyte

[0099] Electrolyte sodium salt (halogen main salt NaPF6: the above auxiliary salt NaBOB (C8H6O4) 0.5 =8:2), an ester solvent (containing PC, EC, and DEC, and the volume ratio of PC, EC and DEC is 3:1:6) and a phosphazene additive PFPN are stirred and mixed in a molar ratio of 1:6:3 to prepare a highly dispersed and clear electrolyte.

[0100] Example 2

[0101] The only difference between this embodiment and embodiment 1 is that in step 2), the halogen main salt NaPF6 is: the auxiliary salt NaBOB (C8H6O4) 0.5 =7:3, and the rest are the same as in Example 1.

[0102] Example 3

[0103] The only difference between this embodiment and embodiment 1 is that in step 2), the halogen main salt NaPF6 is: the auxiliary salt NaBOB (C8H6O4) 0.5 =9.5:0.5, and the rest are the same as in Example 1.

[0104] Example 4

[0105] The only difference between this embodiment and embodiment 1 is that in step 2), the halogen main salt NaPF6 is: the auxiliary salt NaBOB (C8H6O4) 0.5 =7:4, and the rest are the same as in Example 1.

[0106] Example 5

[0107] The only difference between this embodiment and embodiment 1 is that in step 2), the halogen main salt NaPF6 is: the auxiliary salt NaBOB (C8H6O4) 0.5 =9.5:0.1, and the rest are the same as in Example 1.

[0108] Example 6

[0109] The only difference between this embodiment and embodiment 1 is that the molar ratio of the electrolyte salt, the ester solvent and the phosphazene additive PFPN in step 2) is 1:8:1, and the rest is the same as embodiment 1.

[0110] Example 7

[0111] The only difference between this embodiment and embodiment 1 is that the molar ratio of the electrolyte salt, the ester solvent and the phosphazene additive PFPN in step 2) is 1:3:6, and the rest is the same as embodiment 1.

[0112] Example 8

[0113] The only difference between this embodiment and embodiment 1 is that the molar ratio of the electrolyte salt, the ester solvent and the phosphazene additive PFPN in step 2) is 1:7:2, and the rest is the same as in embodiment 1.

[0114] Example 9

[0115] The only difference between this embodiment and embodiment 1 is that the halogen main salt in step 2) is replaced by NaPF6 with NaFSI, and the rest is the same as embodiment 1.

[0116] Example 10

[0117] The only difference between this embodiment and embodiment 1 is that DEC in the ester solvent in step 2) is replaced by DMC, and the rest is the same as embodiment 1.

[0118] Example 11

[0119] The only difference between this embodiment and embodiment 1 is that the composition of the ester solvent in step 2) contains PC and EC, and the volume ratio of PC to EC is 3:7. The rest is the same as embodiment 1.

[0120] Example 12

[0121] The only difference between this embodiment and embodiment 1 is that the phosphazene additive in step 2) is replaced by hexafluorocyclotriphosphazene instead of PFPN, and the rest is the same as embodiment 1.

[0122] Example 13

[0123] The only difference between this embodiment and embodiment 1 is that the phosphazene additive in step 2) is replaced by fluoroethylene carbonate instead of PFPN. The rest is the same as embodiment 1.

[0124] Example 14

[0125] The only difference between this embodiment and embodiment 1 is that no additive is added in step 2), and the molar ratio of the electrolyte sodium salt to the ester solvent is 1:9. The rest is the same as embodiment 1.

[0126] Example 15

[0127] The only difference between this embodiment and embodiment 1 is that phthalic acid in step 1) is replaced by oxalic acid, and the rest is the same as embodiment 1.

[0128] Example 16

[0129] The preparation of the electrolyte in this embodiment includes the following steps:

[0130] 1) Preparation of auxiliary salt LiBOB derivatives:

[0131] Phthalic acid, LiOH, and boric acid were mixed in a dry process in a molar ratio of 2:1:1, and the mixture was first reacted at 110°C for 6 hours, and then at 240°C for 6 hours. The mixture was then washed with ethanol and dried at 60°C until the ethanol was completely evaporated to obtain the auxiliary salt LiBOB derivative.

[0132] 2) Preparation of electrolyte

[0133] The electrolyte lithium salt (halogen main salt LiPF6: the above auxiliary salt LiBOB (C8H6O4) 0.5=8:2), an ester solvent (containing PC, EC, and DEC, and the volume ratio of PC, EC and DEC is 3:1:6) and a phosphazene additive PFPN are stirred and mixed in a molar ratio of 1:6:3 to prepare a highly dispersed and clear electrolyte.

[0134] Comparative Example 1

[0135] The preparation of the electrolyte in this comparative example comprises the following steps:

[0136] Electrolyte sodium salt (NaPF6), ester solvent (containing PC, EC, DEC, and the volume ratio of PC, EC and DEC is 3:1:6) and phosphazene additive PFPN are stirred and mixed in a molar ratio of 1:6:3 to prepare a highly dispersed and clear electrolyte.

[0137] Comparative Example 2

[0138] The only difference between this comparative example and Example 1 is that the electrolyte sodium salt in step 2) only includes the auxiliary salt NaBOB (C8H6O4) 0.5 Except for NaPF6, the rest are the same as those in Example 1.

[0139] Comparative Example 3

[0140] The preparation of the electrolyte in this comparative example comprises the following steps:

[0141] The electrolyte sodium salt (phosphazene main salt NaPF6: auxiliary salt sodium borate = 8:2), ester solvent (containing PC, EC, DEC, and the volume ratio of PC, EC and DEC is 3:1:6) and phosphazene additive PFPN are stirred and mixed in a molar ratio of 1:6:3 to prepare a highly dispersed and clear electrolyte.

[0142] Comparative Example 4

[0143] The preparation of the electrolyte in this comparative example comprises the following steps:

[0144] The electrolyte lithium salt (LiPF6), ester solvent (containing PC, EC, DEC, and the volume ratio of PC, EC and DEC is 3:1:6) and phosphazene additive PFPN are stirred and mixed in a molar ratio of 1:6:3 to prepare a highly dispersed and clear electrolyte.

[0145] Comparative Example 5

[0146] The only difference between this comparative example and Example 16 is that the electrolyte lithium salt in step 2) only includes the auxiliary salt LiBOB (C8H6O4) 0.5 Except for LiPF6, everything else is the same as Example 16.

[0147] Test example

[0148] The electrolytes provided in Examples 1-15 and Comparative Examples 1-3 were respectively prepared to produce soft-pack batteries, including the following steps:

[0149] 1) Mix the positive electrode active material sodium iron pyrophosphate with conductive carbon black and PVDF in a ratio of 96%:2%:2% and disperse them evenly to obtain a positive electrode slurry. Apply the slurry on the aluminum foil current collector and adjust the positive electrode surface density to 2.0g / cm 3 Roll pressing is performed to prepare a positive electrode sheet;

[0150] 2) Mix hard carbon, SBR, CMC, and conductive carbon black in a ratio of 94%:3%:2%:1% and evenly disperse in water to produce a negative electrode slurry. Apply this slurry to an aluminum foil current collector, roll-press, and dry to produce a negative electrode sheet.

[0151] 3) Cutting the separator and the positive and negative electrode sheets, laminating them, and encapsulating them with aluminum-plastic film to form a dry battery cell. After baking, the electrolyte is added, and then the cell is processed into a composition and capacity.

[0152] The electrolytes provided in Example 16 and Comparative Examples 4-5 were respectively prepared and soft-pack batteries were made, including the following steps:

[0153] 1) Mix the positive electrode active material lithium iron phosphate with conductive carbon black and PVDF in a ratio of 96%:2%:2% and disperse them evenly to obtain a positive electrode slurry. Apply the slurry on the aluminum foil current collector and adjust the positive electrode surface density to 2.0g / cm 3 Roll pressing is performed to prepare a positive electrode sheet;

[0154] 2) Graphite, SBR, CMC, and conductive carbon black were mixed in a ratio of 94%:3%:2%:1% and evenly dispersed in water to produce a negative electrode slurry. This slurry was coated onto an aluminum foil current collector, roll-pressed, and dried to produce a negative electrode sheet.

[0155] 3) Cutting the separator and the positive and negative electrode sheets, laminating them, and encapsulating them with aluminum-plastic film to form a dry battery cell. After baking, the electrolyte is added, and then the cell is processed into a composition and capacity.

[0156] The following properties of the above batteries were tested.

[0157] ASafety performance test

[0158] The assembled soft-pack battery was adjusted to 100 SOC and tested using an accelerating rate calorimeter (ARC). The test method is a conventional test method in the art and is not particularly limited thereto. The self-heating starting temperature, thermal runaway starting temperature, and thermal runaway maximum temperature were directly read from the accelerating rate calorimeter, and the results are recorded in Table 1.

[0159] B Capacity Test and Cycle Performance Test

[0160] The assembled soft-pack batteries were tested on an electrochemical test cabinet. The voltage setting range for Examples 1-15 and Comparative Examples 1-3 was 2-3.4 V, and the voltage setting range for Example 16 and Comparative Examples 4-5 was 2.5-3.65 V. The current density was 1.5 A / g. The discharge capacity can be read directly from the test cabinet. The capacity retention rate after 500 cycles = (discharge capacity after 500 cycles / initial discharge capacity) × 100%, and the energy efficiency after 500 cycles = (discharge energy after 500 cycles / initial discharge energy) × 100%. The results are recorded in Table 2.

[0161] C Flame retardant performance test

[0162] In a fume hood, 0.02 g of glass fiber was weighed and placed in a beaker. 0.25 mL of the sodium ion electrolyte or lithium ion electrolyte described in Examples 1-16 and Comparative Examples 1-5 was added dropwise. The electrolyte was ignited for the same time using a cigarette lighter. The time from the start of combustion to the extinction of the flame was recorded. This was repeated three times, and the average value was taken to obtain the self-extinguishing time. The SET value was calculated from the self-extinguishing time, where SET value = self-extinguishing time / electrolyte mass. The results of the self-extinguishing time and SET value are recorded in Table 2.

[0163] Table 1

[0164]

[0165]

[0166] Table 2

[0167]

[0168] As can be seen from Table 1, the self-heating starting temperature (153.2° C.) and the thermal runaway starting temperature (262.4° C.) of the sodium ion soft-pack battery in Example 1 are higher than those in Examples 4-5 and Comparative Examples 1-3, further illustrating that the safety performance of the sodium ion battery can be improved by synergistically combining a halogen main salt and a borate derivative auxiliary salt doped with an organic acid ligand; and by regulating the molar ratio of the halogen main salt and the borate derivative auxiliary salt doped with an organic acid ligand within a preferred range, it is also beneficial to improve the safety performance of the sodium ion battery.

[0169] The self-heating starting temperature (153.2°C) and thermal runaway starting temperature (262.4°C) of the sodium ion soft pack battery in Example 1 are higher than those in Examples 13-14, further indicating that the safety performance of sodium ion batteries can be further improved by adding phosphazene additives to the electrolyte.

[0170] The self-heating starting temperature (132.5°C) and the thermal runaway starting temperature (213.6°C) of the lithium-ion soft-pack battery in Example 16 are higher than those in Comparative Examples 4-5, further indicating that the safety performance of lithium-ion batteries can be improved by synergistically combining a halogen main salt and a borate derivative auxiliary salt doped with an organic acid ligand.

[0171] As can be seen from Table 2, Example 1 contains NaBOB (C8H6O4) 0.5 The sodium ion battery containing the phosphazene additive PFPN at a current density of 1.5A / g still has a discharge capacity of 1.45Ah / g after 500 cycles, a capacity retention rate of 97.2%, and an energy efficiency of 95.9%. The sodium ion battery performance of Example 1 is better than that of Examples 4-5 and Comparative Examples 1-3. It can be seen from the electrolyte ignition experiment that compared with the electrolytes described in Examples 4-5 and Comparative Examples 1-3, the self-extinguishing time of Example 1 is shorter and the flame retardant effect is better. Therefore, it is further explained that the synergistic combination of the halogen main salt and the borate derivative auxiliary salt doped with the organic acid ligand can help improve the capacity retention rate, cycle stability and flame retardancy of the sodium ion battery; and by regulating the molar ratio of the halogen main salt and the borate derivative auxiliary salt doped with the organic acid ligand within a preferred range, it can help improve the capacity retention rate, cycle stability and flame retardancy of the sodium ion battery.

[0172] Example 1 contains NaBOB (C8H6O4) 0.5 The sodium ion battery containing the phosphazene additive PFPN at a current density of 1.5 A / g still has a discharge capacity of 1.45 Ah / g after 500 cycles, a capacity retention rate of 97.2%, and an energy efficiency of 95.9%, which are higher than those of Examples 13-14. This further demonstrates that the addition of phosphazene additives to the electrolyte can help improve the capacity retention rate, cycle stability, and flame retardancy of the sodium ion battery.

[0173] Example 16 contains LiBOB (C8H6O4) 0.5 The sodium ion battery containing the phosphazene additive PFPN at a current density of 1.5 A / g still achieved a discharge capacity of 1.59 Ah / g after 500 cycles, with a capacity retention rate of 95.2% and an energy efficiency of 93%. The performance of the lithium ion battery of this embodiment is significantly superior to that of Comparative Examples 4-5. The electrolyte ignition experiment shows that compared with the electrolytes of Comparative Examples 4-5, Example 16 has a shorter self-extinguishing time and better flame retardant effect. Therefore, it is further demonstrated that the synergistic combination of a halogen main salt and a borate derivative auxiliary salt doped with an organic acid ligand helps to improve the capacity retention rate, cycle stability and flame retardancy of lithium ion batteries.

[0174] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An electrolyte, characterized in that The electrolyte includes an electrolyte salt; The electrolyte salt includes a halogen main salt and an auxiliary salt; The auxiliary salt includes a borate derivative doped with an organic acid ligand.

2. The electrolyte according to claim 1, characterized in that The molar ratio of the halogen main salt to the auxiliary salt is (7-9.5):(0.5-3).

3. The electrolyte according to claim 1 or 2, characterized in that The organic acid ligand includes one or more of oxalic acid, malonic acid, succinic acid, o- / m- / terephthalic acid, cis- / fumaric acid, tartaric acid, cyclohexanedicarboxylic acid, dimercaptosuccinic acid, 1,5-naphthalene disulfonic acid or aspartic acid; And / or, the halogen main salt includes one or more of hexafluorophosphate, perchlorate, bisfluorosulfonyl imide salt or bistrifluoromethylsulfonyl imide salt.

4. The electrolyte according to any one of claims 1 to 3, characterized in that The electrolyte further includes an ester solvent and / or a phosphazene additive; Wherein, the ester solvent includes one or more of polycarbonate, ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate or diethyl carbonate; And / or, the phosphazene additive includes one or more of ethoxypentafluorocyclotriphosphazene, methoxypentafluorocyclotriphosphazene, hexafluorocyclotriphosphazene or phenoxycyclotriphosphazene.

5. The electrolyte according to claim 4, characterized in that The molar ratio of the electrolyte salt, the ester solvent and the phosphazene additive is 1:(3-8):(1-6).

6. The electrolyte according to any one of claims 1 to 5, characterized in that The organic acid ligand-doped borate derivative is prepared by a method comprising the following steps: After mixing an organic acid ligand, a metal hydroxide and boric acid, a first reaction and a second reaction are sequentially performed to obtain a borate derivative doped with the organic acid ligand; The reaction temperature of the first reaction is lower than the reaction temperature of the second reaction.

7. The electrolyte according to claim 6, characterized in that The molar ratio of the organic acid ligand, the metal hydroxide and the boric acid is (1-3):1:1; and / or, the reaction temperature of the first reaction is 100° C.-120° C., and the reaction time is 4 h-8 h; And / or, the reaction temperature of the second reaction is 200° C.-300° C., and the reaction time is 4 h-8 h.

8. The electrolyte according to any one of claims 1 to 7, characterized in that The electrolyte is a lithium salt electrolyte, the cation in the halogen-based main salt is a lithium ion, and the auxiliary salt includes LiBOB doped with an organic acid ligand; And / or, the electrolyte is a sodium salt electrolyte, the cations in the halogen-based main salt are sodium ions, and the auxiliary salt includes NaBOB doped with an organic acid ligand.

9. A battery, characterized in that: The battery comprises the electrolyte according to any one of claims 1 to 8.

10. A battery pack, characterized in that: The battery pack includes the battery according to claim 9.

11. An electronic device, characterized in that: The electronic device includes the battery according to claim 9 or the battery pack according to claim 10.

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