Sodium ion battery, battery module, battery pack and electric device

Abstract

The invention provides a sodium ion battery, which comprises a positive pole piece, a negative pole piece and an electrolyte, the negative pole piece comprises a negative current collector and a priming coat formed on the surface of the negative current collector, the electrolyte comprises a first sodium salt, the first sodium salt comprises at least one of a sulfur-containing organic sodium salt and a boron-containing organic sodium salt, the sodium ion battery meets the following relational expression: 0.84 < = Y-0.01 X < = 5.84, Xg / m < 2 > is the surface density of the bottom coating, and Y% is the mass content of the first sodium salt based on the total mass of the electrolyte.

Description

Sodium ion batteries, battery modules, battery packs and electrical devices Technical Field

[0001] The present application relates to the technical field of sodium ion batteries, and in particular to a sodium ion battery, a battery module, a battery pack, and an electrical device. Background Art

[0002] Currently, lithium-ion batteries occupy a core position in power batteries. However, they also face significant challenges, such as the increasing scarcity of lithium resources, rising prices of upstream materials, lagging recycling technology development, and low recycling rates for old batteries. Sodium-ion batteries can utilize the intercalation and deintercalation process of sodium ions between the positive and negative electrodes to achieve charging and discharging. Moreover, sodium resources are far more abundant and widely distributed than lithium, and their cost is much lower than lithium. Therefore, sodium-ion batteries have become a new generation of electrochemical systems with great potential to replace lithium-ion batteries. However, the sodium-ion batteries currently being widely studied have poor high-temperature cycling performance and are accompanied by severe high-temperature gas production, which seriously limits their widespread use.

[0003] Summary of the Invention

[0004] In view of the problems existing in the background technology, the present application provides a sodium ion battery, which aims to improve the high-temperature cycle performance of the sodium ion battery and improve the high-temperature gas production phenomenon of the sodium ion battery.

[0005] To achieve the above-mentioned object, the present application provides a sodium ion battery, comprising a positive electrode sheet, a negative electrode sheet, and an electrolyte, wherein the negative electrode sheet comprises a negative electrode current collector and a primer layer formed on the surface of the negative electrode current collector, and the electrolyte comprises a first sodium salt, wherein the first sodium salt comprises at least one of a sulfur-containing organic sodium salt and a boron-containing organic sodium salt.

[0006] Sodium ion batteries satisfy the following relationship: 0.84≤Y-0.01X≤5.84,

[0007] Where X g / m 2 is the areal density of the primer layer, and Y% is the mass content of the first sodium salt based on the total mass of the electrolyte.

[0008] The surface density of the bottom coating of the sodium ion battery provided in this application is X g / m 2 The relationship between the mass content Y% of the first sodium salt and the content of the first sodium salt satisfies 0.84≤Y-0.01X≤5.84. By regulating the surface density of the primer layer and the mass content of the first sodium salt, the high-temperature cycle performance of the sodium-ion battery is improved, the high-temperature gas production phenomenon of the sodium-ion battery is improved, and the electrochemical performance and safety performance of the sodium-ion battery at high temperatures are improved.

[0009] In any embodiment, the anion of the sulfur-containing organic sodium salt comprises at least one of the structures shown in Formula I and Formula II,

[0010]

[0011] Wherein R1 and R2 are each independently selected from at least one of fluorine, substituted or unsubstituted C1-C6 alkyl, and R3 is a substituted or unsubstituted C1-C6 alkyl.

[0012] In any embodiment, the sulfur-containing organic sodium salt comprises one or more of sodium trifluoromethanesulfonate, sodium bis(fluoromethylsulfonyl)imide, sodium bis(trifluoromethylsulfonyl)imide, and sodium (fluorosulfonyl)(trifluoromethylsulfonyl)imide.

[0013] Selecting suitable sulfur-containing organic sodium salts can improve the high-temperature cycle performance of sodium-ion batteries and improve the high-temperature gas production phenomenon of sodium-ion batteries.

[0014] In any embodiment, the sulfur-containing organic sodium salt comprises one or more of sodium trifluoromethanesulfonate, sodium bis(fluoromethylsulfonyl)imide, and sodium bis(trifluoromethylsulfonyl)imide.

[0015] Selecting suitable sulfur-containing organic sodium salts can further improve the high-temperature cycle performance of sodium-ion batteries and further improve the high-temperature gas production phenomenon of sodium-ion batteries.

[0016] In any embodiment, the boron-containing organic sodium salt comprises one or more of sodium tetraphenylborate, sodium bis(salicylate-2-)borate, sodium salicylatebenzeneborate, sodium difluorooxalatoborate, and sodium bisoxalatoborate.

[0017] Selecting suitable boron-containing organic sodium salts can improve the high-temperature cycle performance of sodium-ion batteries and improve the high-temperature gas production phenomenon of sodium-ion batteries.

[0018] In any embodiment, the boron-containing organic sodium salt comprises one or both of sodium difluorooxalatoborate and sodium bisoxalatoborate.

[0019] Selecting a suitable boron-containing organic sodium salt can improve the initial coulombic efficiency and room temperature cycle performance of sodium ion batteries. At the same time, sodium ion batteries have excellent high-temperature cycle performance and low high-temperature gas production.

[0020] In any embodiment, the surface density of the primer layer is X g / cm 2 5g / cm 2 ~50g / cm 2 .

[0021] By controlling the surface density of the base coating within an appropriate range, the sodium-ion battery has excellent high-temperature cycle performance, first coulombic efficiency and room-temperature cycle performance. The high-temperature gas production and room-temperature gas production of the sodium-ion battery are small, which broadens the operating temperature of the sodium-ion battery.

[0022] In any embodiment, the primer layer comprises one or more of superconductive carbon black, Ketjen black, acetylene black, carbon nanotubes, and graphene.

[0023] In any embodiment, the electrolyte further includes a second sodium salt, and the second sodium salt includes at least one of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium hexafluoroarsenate, sodium perchlorate, and sodium trifluoroacetate.

[0024] The electrolyte also contains a second sodium salt, which can improve the first coulombic efficiency, room temperature cycle performance and high temperature cycle performance of the sodium ion battery, and reduce the room temperature and high temperature gas production of the sodium ion battery.

[0025] In any embodiment, the sodium ion battery satisfies the following relationship: Y+Z≥3 or / and Z / Y≥1.21, wherein Y% is the mass content of the first sodium salt, and Z% is the mass content of the second sodium salt, based on the total mass of the electrolyte.

[0026] By regulating the mass content of the first sodium salt and the mass content of the second sodium salt so that the two satisfy the relationship Y+Z≥3 or / and Z / Y≥1.21, the first coulombic efficiency, room temperature cycle performance and high temperature cycle performance of the sodium ion battery can be improved.

[0027] In any embodiment, the mass content of the second sodium salt is 1% to 40% based on the total mass of the electrolyte.

[0028] Controlling the mass content of the second sodium salt within an appropriate range can improve the initial coulombic efficiency, room temperature cycle performance and high temperature cycle performance of the sodium ion battery, and reduce the high temperature gas production performance of the sodium ion battery.

[0029] In any embodiment, the mass content of the second sodium salt is 7% to 35% based on the total mass of the electrolyte.

[0030] Controlling the mass content of the second sodium salt within an appropriate range can improve the initial coulombic efficiency of the sodium ion battery, while enabling the battery to have excellent high-temperature cycle performance and room-temperature cycle performance, and allowing the battery to have less high-temperature gas production.

[0031] In any embodiment, the electrolyte further comprises a solvent, and the mass content of the solvent is 50% to 98% based on the total mass of the electrolyte.

[0032] Controlling the mass content of the solvent within an appropriate range can improve the initial coulombic efficiency, room temperature cycle performance and high temperature cycle performance of the sodium ion battery, and reduce the high temperature gas production of the sodium ion battery.

[0033] In some embodiments, the mass content of the solvent is 50% to 90% based on the total mass of the electrolyte.

[0034] Controlling the mass content of the solvent within an appropriate range can improve the initial coulombic efficiency and high-temperature cycle performance of the sodium-ion battery, while also enabling the sodium-ion battery to have excellent room-temperature cycle performance and low high-temperature gas production.

[0035] In any embodiment, the solvent comprises an ether solvent, which can be selected from at least one of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol ethyl formate, ethylene glycol dibutyl ether, 1,3-dioxolane, 1,4-dioxane, tetrahydrofuran, methyltetrahydrofuran, 1,1,2,2-tetrafluoroethyl methyl ether, 2,2,3,3-tetrafluoropropyl methyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, bis-(2,2,2-trifluoroethyl) ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, methyl nonafluorobutyl ether, bis-(1,1,2,2-tetrafluoroethyl) ether, and difluoromethyl-2,2,2-trifluoroethyl ether.

[0036] Ether solvents can improve the first coulombic efficiency, room temperature cycle performance and high temperature cycle performance of sodium ion batteries, reduce the room temperature and high temperature gas production phenomena of sodium ion batteries, improve the electrochemical properties and safety performance of sodium ions, and broaden the operating temperature of sodium ion batteries.

[0037] In any embodiment, the sodium ion battery is a negative electrode-less sodium battery.

[0038] A second aspect of the present application provides a battery module, comprising the sodium ion battery of the first aspect.

[0039] A third aspect of the present application provides a battery pack comprising the sodium ion battery of the first aspect or the battery module of the second aspect.

[0040] A fourth aspect of the present application provides an electrical device comprising at least one of the sodium ion battery of the first aspect, the battery module of the second aspect, or the battery pack of the third aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] FIG1 is a schematic diagram of a sodium ion battery according to one embodiment of the present application;

[0042] FIG2 is an exploded view of the sodium ion battery according to one embodiment of the present application shown in FIG1 ;

[0043] FIG3 is a schematic diagram of a battery module according to an embodiment of the present application;

[0044] FIG4 is a schematic diagram of a battery pack according to an embodiment of the present application;

[0045] FIG5 is an exploded view of the battery pack according to an embodiment of the present application shown in FIG4 ;

[0046] FIG6 is a schematic diagram of an electrical device using a sodium ion battery as a power source according to an embodiment of the present application.

[0047] Reference numerals:

[0048] 1. Battery pack; 2. Upper box; 3. Lower box; 4. Battery module; 5. Sodium-ion battery; 5. Casing; 5. Electrode assembly; 5. Cover. DETAILED DESCRIPTION

[0049] Below, the embodiments of the positive electrode active material and its manufacturing method, positive electrode sheet, secondary battery, battery module, battery pack and electrical device of the present application are specifically disclosed in detail with appropriate reference to the drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0050] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0051] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0052] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0053] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0054] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0055] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0056] Under high temperature conditions, the inorganic components in the solid electrolyte interface (SEI) of sodium-ion batteries will dissolve, making the SEI film porous. The electrolyte will continue to decompose on the surface of the negative electrode, and the SEI film will continue to decompose and regenerate, constantly consuming the limited sodium resources within the sodium-ion battery, resulting in greater self-discharge and poor cycle performance. At the same time, under high temperature conditions, the positive and negative electrodes of the sodium-ion battery will chemically react with the electrolyte, releasing heat and generating gas, causing the battery to expand in volume. In severe cases, it may also cause an internal short circuit in the battery, reducing the safety performance of the sodium-ion battery and severely limiting its application.

[0057] [Sodium-ion battery]

[0058] Based on this, the present application provides a sodium ion battery, comprising a positive electrode sheet, a negative electrode sheet, and an electrolyte, wherein the negative electrode sheet comprises a negative electrode current collector and a primer layer formed on the surface of the negative electrode current collector, and the electrolyte comprises a first sodium salt, wherein the first sodium salt comprises at least one of a sulfur-containing organic sodium salt and a boron-containing organic sodium salt.

[0059] Sodium ion batteries satisfy the following relationship: 0.84≤Y-0.01X≤5.84,

[0060] Where X g / m 2is the areal density of the primer layer, and Y% is the mass content of the first sodium salt based on the total mass of the electrolyte.

[0061] As used herein, the term "sodium-ion battery" refers to a battery that utilizes the transfer of sodium ions between a positive and negative electrode. The negative electrode of a sodium-ion battery can be made of any material. Examples of sodium-ion batteries include, but are not limited to, sodium metal batteries and cathode-free sodium metal batteries.

[0062] In this article, the term “electrolyte” refers to the carrier for ion transport in sodium ion batteries, including liquid electrolyte, solid electrolyte or quasi-solid electrolyte.

[0063] As used herein, the term "organic sodium salt" refers to a salt containing the reaction product of an organic acid and an inorganic base.

[0064] As used herein, the term "sulfur-containing organic sodium salt" refers to an organic sodium salt containing sulfur.

[0065] As used herein, the term "boron-containing organic sodium salt" refers to an organic sodium salt containing the boron element.

[0066] In this article, the term "anode-free sodium battery" refers to a sodium-ion battery that uses a current collector as the anode during assembly. During the charging process, sodium ions are deposited on the current collector to form the anode of the sodium-ion battery.

[0067] In some embodiments, the negative electrode plate is a negative electrode plate of a sodium battery without a negative electrode. During the first charge process, the electrolyte components first undergo reduction decomposition on the primer layer on the surface of the current collector, and some decomposition products are deposited on the primer layer to form SEI. Subsequently, the sodium ions in the electrolyte are desolvated at the interface between the negative electrode and the electrolyte, and pass through the SEI to be deposited on the primer layer. The primer layer can effectively reduce the overpotential of sodium metal deposition, inhibit the formation of sodium dendrites, and is beneficial to improving the cycle performance of the sodium ion battery. During the discharge process, metallic sodium can be converted into sodium ions and return to the positive electrode to achieve cyclic charge and discharge. The anions in the sulfur-containing organic sodium salt or the boron-containing organic sodium salt have a strong binding force with the sodium ions, and are more likely to participate in the solvation structure of the electrolyte. They are easily deposited with sodium ions and contact the negative electrode surface, and are reduced on the negative electrode surface to form SEI mainly composed of sulfides and borides, which greatly improves the structural stability and uniformity of the SEI on the sodium metal surface. On the one hand, SEI containing a large amount of sulfide and boride is not easy to undergo secondary decomposition and regeneration, which reduces the consumption of sodium inside the battery and improves the high-temperature cycle performance of sodium-ion batteries. On the other hand, SEI with stable structure and uniform distribution can reduce the direct contact between the electrolyte and sodium metal, reduce the side reactions between the electrolyte and sodium metal, inhibit the generation of hydrogen in sodium-ion batteries during high-temperature cycles, and improve the high-temperature gas production phenomenon of sodium-ion batteries.

[0068] The applicant unexpectedly found that the surface density of the bottom coating of the sodium ion battery is X g / m 2 The mass content Y% of the sulfur-containing organic sodium salt or the boron-containing organic sodium salt based on the total mass of the electrolyte is controlled within the numerical range of 0.84≤Y-0.01X≤5.84. The synergistic cooperation between the primer layer and the electrolyte can improve the stability and uniformity of the SEI, thereby improving the high-temperature cycle performance of the sodium-ion battery, improving the high-temperature gas production phenomenon of the sodium-ion battery, and improving the electrochemical performance and safety performance of the sodium-ion battery at high temperatures.

[0069] In some embodiments, the anion of the sulfur-containing organic sodium salt comprises at least one of the structures shown in Formula I and Formula II.

[0070]

[0071] Wherein R1 and R2 are each independently selected from at least one of fluorine, substituted or unsubstituted C1-C6 alkyl, and R3 is a substituted or unsubstituted C1-C6 alkyl.

[0072] As used herein, the term "C1-C6 alkyl" refers to a straight or branched hydrocarbon chain radical consisting solely of carbon and hydrogen atoms, with no unsaturation present in the radical, having from one to six carbon atoms, and attached to the remainder of the molecule by a single bond.

[0073] As used herein, the term "substituted" refers to a compound or chemical moiety in which at least one hydrogen atom is replaced by another chemical moiety, wherein the substituents are each independently selected from the group consisting of hydroxyl, thiol, amino, cyano, nitro, aldehyde, halogen, alkenyl, alkynyl, aryl, heteroaryl, C1-C6 alkyl, and C1-C6 alkoxy.

[0074] In some embodiments, R1 and R2 are each independently selected from fluorine, C1-C3 fluoroalkane.

[0075] In some embodiments, R3 is selected from C1-C3 fluoroalkanes.

[0076] As used herein, the term "C1-C3 fluoroalkane" refers to an alkane having one to three carbon atoms substituted with at least one fluorine.

[0077] In some embodiments, the sulfur-containing organic sodium salt comprises one or more of sodium trifluoromethanesulfonate, sodium bis(fluoromethylsulfonyl)imide, sodium bis(trifluoromethylsulfonyl)imide, and sodium (fluorosulfonyl)(trifluoromethylsulfonyl)imide.

[0078] Selecting suitable sulfur-containing organic sodium salts can improve the high-temperature cycle performance of sodium-ion batteries and improve the high-temperature gas production phenomenon of sodium-ion batteries.

[0079] In some embodiments, the sulfur-containing organic sodium salt comprises one or more of sodium trifluoromethanesulfonate, sodium bis(fluoromethylsulfonyl)imide, and sodium bis(trifluoromethylsulfonyl)imide.

[0080] Selecting suitable sulfur-containing organic sodium salts can further improve the high-temperature cycle performance of sodium-ion batteries and further improve the high-temperature gas production phenomenon of sodium-ion batteries.

[0081] In some embodiments, the boron-containing organic sodium salt comprises one or more of sodium tetraphenylborate, sodium bis(salicylate-2-)borate, sodium salicylatebenzene borate, sodium difluorooxalatoborate, and sodium bisoxalatoborate.

[0082] Selecting suitable boron-containing organic sodium salts can improve the high-temperature cycle performance of sodium-ion batteries and improve the high-temperature gas production phenomenon of sodium-ion batteries.

[0083] In some embodiments, the boron-containing organic sodium salt comprises one or both of sodium difluorooxalatoborate and sodium bisoxalatoborate.

[0084] Selecting a suitable boron-containing organic sodium salt can improve the initial coulombic efficiency and room temperature cycle performance of sodium ion batteries. At the same time, sodium ion batteries have excellent high-temperature cycle performance and low high-temperature gas production.

[0085] In some embodiments, the basecoat layer has an areal density of X g / cm 2 5g / cm 2 ~50g / cm 2 .

[0086] In some embodiments, the basecoat layer has an areal density of X g / cm 2 5g / cm 2 ~10g / cm 2 、10g / cm 2 ~20g / cm 2 , 20g / cm 2 ~30g / cm 2 、30g / cm 2 ~40g / cm 2 , 40g / cm 2 ~50g / cm 2 , 5g / cm 2 ~15g / cm 2 、15g / cm 2 ~25g / cm 2 , 25g / cm 2 ~35g / cm 2 、35g / cm 2 ~45g / cm 2 , 45g / cm 2 ~50g / cm2 、10g / cm 2 ~30g / cm 2 、10g / cm 2 ~40g / cm 2 Any one of .

[0087] A suitable range of undercoat surface density can optimize the sodium metal deposition effect and improve the coulombic efficiency and cycle performance of sodium-ion batteries. At the same time, a suitable range of undercoat surface density can also increase the energy density of sodium-ion batteries and meet the use requirements of sodium-ion batteries.

[0088] In summary, the appropriate range of the undercoat surface density enables the sodium-ion battery to have excellent high-temperature cycle performance, first coulombic efficiency, room-temperature cycle performance, and low high-temperature gas production and room-temperature gas production.

[0089] In some embodiments, the primer layer comprises one or more of superconductive carbon black, Ketjen black, acetylene black, carbon nanotubes, and graphene.

[0090] In some embodiments, the primer layer comprises at least one of mesocarbon microbeads, graphite, natural graphite, expanded graphite, artificial graphite, glassy carbon, carbon-carbon composites, carbon fibers, hard carbon, porous carbon, highly oriented graphite, three-dimensional graphite, and carbon black.

[0091] The carbon material in the undercoat layer can inhibit the formation of sodium dendrites, which is beneficial to improving the cycle performance of sodium ion batteries.

[0092] In some embodiments, the primer layer comprises a polymeric binder.

[0093] In some embodiments, the polymer binder is at least one of sodium cellulose, sodium carboxymethyl cellulose, hydroxypropyl cellulose, sodium hydroxymethyl cellulose, potassium hydroxymethyl cellulose, diacetyl cellulose, polyacrylic acid, sodium alginate, styrene-butadiene rubber, acrylic butadiene rubber, polypyrrole, polyaniline, epoxy resin and guardo gum.

[0094] In some embodiments, the negative electrode current collector includes at least one of a metal foil, a metal foam current collector, a metal mesh current collector, a carbon felt current collector, a carbon cloth current collector, a carbon paper current collector, and a composite current collector.

[0095] In some embodiments, the metal foil material may be copper foil, aluminum foil, stainless steel foil, iron foil, zinc foil, titanium foil, and the metal foam current collector may be copper foam, aluminum foam, zinc foam, etc. The metal mesh current collector may be copper mesh or aluminum mesh. The composite current collector includes a polymer base film and metal foil materials formed on both sides of the polymer base film. The composite current collector may be a "sandwich" structure, with the polymer base film located in the middle and metal foil materials provided on both sides. The polymer base film may be one of polyamide, polyterephthalate, polyimide, polyethylene, polypropylene, polystyrene, polyvinyl chloride, acrylonitrile-butadiene-styrene copolymer, polybutylene terephthalate, poly(p-phenylene terephthalamide), polypropylene, polyoxymethylene, epoxy resin, phenolic resin, polytetrafluoroethylene, polyvinylidene fluoride, silicone rubber, and polycarbonate.

[0096] In some embodiments, the electrolyte further comprises a second sodium salt, and the second sodium salt comprises at least one of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium hexafluoroarsenate, sodium perchlorate, and sodium trifluoroacetate.

[0097] The binding force between the anions and sodium ions in the second sodium salt is weaker than that in the first sodium salt, but it facilitates the rapid deposition and stripping of sodium metal, improving the battery's kinetic performance. Especially in anode-free batteries, the second sodium salt can effectively guarantee the battery's capacity and cycle performance. The second sodium salt can effectively optimize the deposition and stripping of sodium metal and can be used to improve the cycle performance of sodium-ion batteries. At the same time, the appropriate sodium salt concentration gives the electrolyte an appropriate viscosity and excellent ionic conductivity, improving the overall electrochemical performance of the sodium-ion battery.

[0098] In some embodiments, the sodium ion battery satisfies the following relationship: Y+Z≥3 and / or Z / Y≥1.21,

[0099] Wherein, Y% is the mass content of the first sodium salt, based on the total mass of the electrolyte; Z% is the mass content of the second sodium salt, based on the total mass of the electrolyte.

[0100] As described above, the first sodium salt comprises a sulfur-containing organic sodium salt or a boron-containing organic sodium salt, which readily participates in the formation of a structurally stable and uniformly distributed SEI, thereby improving the high-temperature cycling performance of the sodium-ion battery and reducing high-temperature gassing. The second sodium salt is used to optimize the deposition and stripping of sodium metal, thereby improving the cycling performance of the sodium-ion battery.

[0101] The applicant unexpectedly discovered that by controlling the mass content Y% of the first sodium salt based on the total mass of the electrolyte and the mass content Y% of the second sodium salt based on the total mass of the electrolyte within the numerical range of Y+Z≥3 and / or Z / Y≥1.21, the first sodium salt can synergize with the effect of facilitating the formation of a stable SEI and the effect of the second sodium salt on the efficient deposition and stripping of metallic sodium to improve the first coulombic efficiency, room temperature cycle performance and high temperature cycle performance of the sodium ion battery, thereby improving the electrochemical performance of the sodium ion battery.

[0102] In some embodiments, the mass content of the second sodium salt is 1% to 40% based on the total mass of the electrolyte.

[0103] In some embodiments, the mass content of the second sodium salt is any one of 1% to 10%, 10% to 20%, 20% to 30%, 30% to 40%, 7% to 35%, 10% to 35%, and 10% to 40%, based on the total mass of the electrolyte.

[0104] The second sodium salt with an appropriate mass content can, on the one hand, optimize the deposition and stripping of sodium metal and improve the cycle performance of sodium-ion batteries; on the other hand, it can make the electrolyte have appropriate viscosity and excellent ionic conductivity, thereby improving the electrochemical performance of sodium-ion batteries.

[0105] In summary, the second sodium salt with an appropriate mass content can improve the first coulombic efficiency, room temperature cycle performance and high temperature cycle performance of sodium ion batteries, and reduce the high temperature gas production performance of sodium ion batteries.

[0106] In some embodiments, the electrolyte further comprises a solvent, and the mass content of the solvent is 50% to 98% based on the total mass of the electrolyte.

[0107] In some embodiments, the electrolyte further comprises a solvent, and the mass content of the solvent is any one of 50% to 60%, 60% to 70%, 70% to 80%, 80% to 90%, 90% to 95%, 50% to 70%, 50% to 80%, 50% to 90%, 50% to 85%, and 60% to 85%, based on the total mass of the electrolyte.

[0108] A solvent with an appropriate mass content can improve the initial coulombic efficiency, room temperature cycle performance and high temperature cycle performance of sodium ion batteries, and reduce the high temperature gas production performance of sodium ion batteries.

[0109] In some embodiments, the solvent comprises an ether solvent, which can be selected from at least one of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol ethyl formate, ethylene glycol dibutyl ether, 1,3-dioxolane, 1,4-dioxane, tetrahydrofuran, methyltetrahydrofuran, 1,1,2,2-tetrafluoroethyl methyl ether, 2,2,3,3-tetrafluoropropyl methyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, bis-(2,2,2-trifluoroethyl) ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, methyl nonafluorobutyl ether, bis-(1,1,2,2-tetrafluoroethyl) ether, and difluoromethyl-2,2,2-trifluoroethyl ether.

[0110] In some embodiments, the solvent comprises at least one of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol ethyl formate, ethylene glycol dibutyl ether, 1,3-dioxolane, 1,4-dioxane, tetrahydrofuran, and methyltetrahydrofuran.

[0111] The molecules of ether solvents can construct a stable electrode / electrolyte interface on the surface of the bottom coating of sodium ion batteries, form a stable SEI, reduce electrochemical polarization, improve the coulombic efficiency, room temperature cycle performance and high temperature cycle performance of sodium ion batteries, reduce the room temperature and high temperature gas production of sodium ion batteries, and broaden the operating temperature of sodium ion batteries.

[0112] In some embodiments, the solvent comprises an ester solvent, which can be selected from at least one of vinylene carbonate, ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0113] In some embodiments, the electrolyte may further optionally include additional additives that can improve certain properties of the sodium ion battery, such as additives that improve the overcharge performance of the sodium ion battery, additives that improve the thermal stability of the electrolyte, and the like.

[0114] In some embodiments, the sodium ion battery is an anode-less sodium battery.

[0115] In anode-free sodium batteries, the metallic sodium on the negative electrode is generated during subsequent cycles. Sodium-ion batteries have no voltage before the first charge, allowing them to be stored for long periods without self-discharge. Even if the battery is short-circuited, no current is generated, resulting in extremely high safety. Because the negative electrode current collector surface is devoid of negative electrode active material and only uses the negative electrode current collector, the battery can achieve a higher energy density.

[0116] [Positive electrode]

[0117] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer formed on at least a portion of the surface of the positive electrode current collector, the positive electrode active material layer includes a positive electrode active material, and the positive electrode active material may include at least one of a layered transition metal oxide, a polyanionic compound, and a Prussian blue compound.

[0118] The transition metal in the layered transition metal oxide can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. Optionally, the layered transition metal oxide is, for example, NaxMO2, wherein M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr, and Cu, and 0<x≤1.

[0119] Polyanionic compounds can be metal ions, transition metal ions and tetrahedral (YO4) n- A class of compounds with anionic units. The metal ion can be selected from sodium ion, lithium ion, potassium ion, and zinc ion; the transition metal can be selected from at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be selected from at least one of P, S, and Si; n represents (YO4) n- valence.

[0120] Prussian blue compounds can be compounds containing sodium ions, transition metal ions, and cyanide ions (CN-). The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. Prussian blue compounds are, for example, Na a Me b Me' c (CN)6, wherein Me and Me' are each independently at least one of Ni, Cu, Fe, Mn, Co and Zn, 0<a≤2, 0<b<1, 0<c<1.

[0121] The positive electrode active material layer may further include a conductive agent to improve the conductivity of the positive electrode. The conductive agent may be selected from one or more of Super P, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphite, graphene, and carbon nanofibers.

[0122] The positive electrode active material layer may further include a binder to firmly bond the positive electrode active material and optional conductive agent to the positive electrode current collector. The binder may be at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), polyvinyl alcohol (PVA), ethylene-vinyl acetate copolymer (EVA), styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), sodium alginate (SA), polymethacrylic acid (PMA), and carboxymethyl chitosan (CMCS).

[0123] The positive electrode current collector can be a conductive carbon sheet, metal foil, carbon-coated metal foil, porous metal plate, or a composite current collector. The conductive carbon material of the conductive carbon sheet can be selected from one or more of Super P, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphite, graphene, and carbon nanofibers. The metal material of the metal foil, carbon-coated metal foil, and porous metal plate can each be independently selected from at least one of copper, aluminum, nickel, and stainless steel. The composite current collector can be a composite of metal foil and a polymer-based film.

[0124] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0125] [Isolation film]

[0126] In some embodiments, the sodium ion battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0127] In some embodiments, the material of the separator can be selected from at least one of polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester, and natural fibers. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0128] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0129] In some embodiments, the sodium ion battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0130] In some embodiments, the outer packaging of the sodium ion battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the sodium ion battery can also be a soft shell, such as a pouch-type soft shell. The soft shell can be made of plastic, and examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0131] The present application has no particular limitation on the shape of the sodium ion battery, which may be cylindrical, square, or any other shape. For example, FIG1 shows a sodium ion battery 5 having a square structure as an example.

[0132] In some embodiments, referring to FIG2 , the outer packaging may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can be formed into an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the sodium ion battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0133] In some embodiments, sodium ion batteries can be assembled into a battery module. The number of sodium ion batteries contained in the battery module can be one or more. The specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0134] FIG3 illustrates an exemplary battery module 4. Referring to FIG3 , within the battery module 4, multiple sodium-ion batteries 5 may be arranged sequentially along the length of the battery module 4. Alternatively, the arrangement may be arranged in any other manner. Furthermore, the multiple sodium-ion batteries 5 may be secured using fasteners.

[0135] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of sodium ion batteries 5 are received in the receiving space.

[0136] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0137] Figures 4 and 5 illustrate an example battery pack 1. Referring to Figures 4 and 5 , the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box comprises an upper case 2 and a lower case 3. The upper case 2 can be placed over the lower case 3 to form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0138] In addition, the present application also provides an electrical device, which includes at least one of the sodium ion battery, battery module, or battery pack provided in the present application. The sodium ion battery, battery module, or battery pack can be used as a power source for the electrical device, and can also be used as an energy storage unit for the electrical device. The electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as 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., but is not limited thereto.

[0139] As the electrical device, a sodium ion battery, a battery module or a battery pack can be selected according to its usage requirements.

[0140] Figure 6 shows an example of an electric device. This device can be a pure electric vehicle, hybrid electric vehicle, or plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the sodium-ion battery in this device, a battery pack or battery module can be used.

[0141] Another example device may be a mobile phone, a tablet computer, a laptop computer, etc. Such a device is generally required to be lightweight and thin, and may use a sodium ion battery as a power source.

[0142] Example

[0143] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0144] 1. Preparation method

[0145] Example 1

[0146] 1) Preparation of electrolyte

[0147] In a dry argon atmosphere glove box, 82 g of solvent ethylene glycol dimethyl ether, 3 g of the first sodium salt sodium bis(fluoromethylsulfonyl)imide (NaFSI), and 15 g of the second sodium salt sodium hexafluorophosphate (NaPF6) were mixed, wherein, based on the total mass of the electrolyte, the mass content of sodium bis(fluoromethylsulfonyl)imide was 3%, the mass content of sodium hexafluorophosphate was 15%, and the mass content of ethylene glycol dimethyl ether was 82%.

[0148] 2) Preparation of positive electrode sheet

[0149] The positive electrode active material Na3V2(PO4)3, the binder polyvinylidene fluoride (PVDF), and the conductive agent conductive carbon black (Super-P) are mixed in N-methylpyrrolidone (NMP) solvent in a mass ratio of 96%:2%:2% to prepare the positive electrode slurry. The positive electrode slurry is coated on the surface of aluminum foil by an extrusion coating machine according to the mass requirement of the positive electrode active material per unit area and dried. The coated electrode is then pressed by a cold press at a pressure of 2.5g / cm 3 The designed compaction is cold pressed to prepare the final positive electrode sheet.

[0150] 3) Preparation of negative electrode sheet

[0151] Add carbon nanotubes and sodium alginate into water and stir to form a uniform slurry. The slurry is coated on the negative electrode current collector aluminum foil, dried and cut to obtain a negative electrode sheet without a negative electrode structure. The surface density of the carbon nanotube base coating is 20g / m 2 .

[0152] 4) Isolation film

[0153] Polyethylene film (PE film) is used as the separator.

[0154] 5) Battery Preparation

[0155] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator placed between the positive and negative electrode sheets to serve as an isolation layer. The electrolyte is then added to form a button battery.

[0156] Examples 2 to 8

[0157] The batteries of Examples 2 to 8 were prepared similarly to the battery of Example 1, except that the mass content of sodium bis(fluoromethylsulfonyl)imide in the electrolyte and / or the surface density of the primer layer were adjusted. The specific adjustment parameters are shown in Table 1 below.

[0158] Examples 9 to 15

[0159] The batteries of Examples 9 to 15 were prepared similarly to the battery of Example 1, except that the 3% by mass content of sodium bis(fluoromethylsulfonyl)imide was replaced by 1.5% by mass of sodium bis(fluoromethylsulfonyl)imide and 1.5% by mass of sodium difluorooxalatoborate (NaDFOB), 3% by mass of sodium (fluorosulfonyl)(trifluoromethylsulfonyl)imide, 3% by mass of sodium trifluoromethanesulfonate (NaOTf), 3% by mass of sodium bis(trifluoromethylsulfonyl)imide (NaTFSI), 3% by mass of sodium salicylatebenzene borate (NaBDSB), 3% by mass of sodium difluorooxalatoborate, and 3% by mass of sodium bis(oxalatoborate) (NaBOB), respectively. The specific adjustment parameters are shown in Table 1 below.

[0160] Examples 16 to 19

[0161] The battery preparation methods of Examples 16 to 19 are similar to those of Example 1, but the surface density of the primer layer is adjusted. The specific adjustment parameters are shown in Table 1 below.

[0162] Examples 20-21

[0163] The battery preparation method of Examples 20 to 21 is similar to that of Example 1, but the mass contents of sodium bis(fluoromethylsulfonyl)imide and sodium hexafluorophosphate are adjusted, and the surface density of the carbon base coating is adjusted to 40 g / m 2 The specific adjustment parameters are shown in Table 1 below.

[0164] Examples 22 to 25

[0165] The battery preparation methods of Examples 22 to 25 are similar to those of Example 1, except that sodium bis(fluoromethylsulfonyl)imide is replaced by boron hexafluorophosphate (NaBF4), sodium hexafluoroarsenate (NaAsF6), sodium perchlorate (NaClO 4) , sodium trifluoroacetate (CF3COONa), and the specific adjustment parameters are shown in Table 1 below.

[0166] Examples 26 to 34

[0167] The battery preparation methods of Examples 26 to 34 are similar to those of Example 1, except that the mass content of sodium hexafluorophosphate and / or the mass content of sodium bis(fluoromethylsulfonyl)imide are adjusted. The specific adjustment parameters are shown in Table 1 below.

[0168] Examples 35-36

[0169] The battery preparation methods of Examples 35 to 36 are similar to those of Example 1, except that ethylene glycol dimethyl ether is replaced by dimethyl carbonate and tetrahydrofuran, respectively. The specific adjustment parameters are shown in Table 1 below.

[0170] Comparative Example 1

[0171] Comparative Example 1 is similar to the battery preparation method of Example 1, but the preparation method of the negative electrode sheet is adjusted: carbon nanotubes and sodium alginate are added to water and stirred into a uniform slurry, the slurry is coated on the negative electrode current collector aluminum foil, and then dried and cut to obtain a carbon nanotube primer layer, wherein the surface density of the carbon nanotube primer layer is 20g / m 2; The negative electrode active material hard carbon, the conductive agent acetylene black, the binder styrene-butadiene rubber (SBCs), and the thickener hydroxymethyl cellulose (CMC) are fully stirred and mixed in an appropriate amount of deionized water in a weight ratio of 90:5:4:1 to form a uniform negative electrode slurry; the negative electrode slurry is coated on the carbon nanotube base coating, dried at 100°C, and pressed to obtain a negative electrode sheet, and sodium bis(fluoromethylsulfonyl)imide is replaced with sodium hexafluorophosphate. The specific adjustment parameters are shown in Table 1 below.

[0172] Comparative Example 2

[0173] The battery preparation method of Comparative Example 2 is similar to that of Example 1, except that sodium bis(fluoromethylsulfonyl)imide is replaced with sodium hexafluorophosphate, and the negative electrode is replaced with aluminum foil without a carbon nanotube primer layer. The specific adjustment parameters are shown in Table 1 below.

[0174] Comparative Example 3

[0175] The battery preparation method of Comparative Example 3 is similar to that of Comparative Example 2, except that ethylene glycol dimethyl ether is replaced with dimethyl carbonate. The specific adjustment parameters are shown in Table 1 below.

[0176] Comparative Example 4

[0177] The battery preparation method of Comparative Example 4 is similar to that of Example 1, except that the negative electrode plate is replaced with aluminum foil without a carbon nanotube primer layer. The specific adjustment parameters are shown in Table 1 below.

[0178] Comparative Example 5

[0179] The battery preparation method of Comparative Example 5 is similar to that of Example 1, except that sodium bis(fluoromethylsulfonyl)imide is replaced by sodium hexafluorophosphate. The specific adjustment parameters are shown in Table 1 below.

[0180] Comparative Examples 6-7

[0181] The battery preparation methods of Comparative Examples 6 to 7 are similar to those of Example 1, except that sodium bis(fluoromethylsulfonyl)imide is replaced by sodium fluorosulfonate and sodium tetrafluoroborate, respectively. The specific adjustment parameters are shown in Table 1 below.

[0182] Comparative Examples 8 to 11

[0183] The battery preparation methods of Comparative Examples 8 to 11 are similar to those of Example 1, but Y-0.01X is adjusted by adjusting the mass content of sodium bis(fluoromethylsulfonyl)imide in the electrolyte and / or the surface density of the primer layer. The specific adjustment parameters are shown in Table 1 below.

[0184] 2. Test Method

[0185] 1. Battery

[0186] 1) First Coulombic efficiency test

[0187] At 25°C and normal pressure (0.1MPa), the battery was charged to 3.5V at a constant current rate of 0.1C. The charging capacity at this time was recorded as the first charging capacity of the battery. After that, it was allowed to stand for 5 minutes, and then discharged at a constant current rate of 0.1C to 3.2V. It was allowed to stand for 5 minutes. The discharge capacity at this time was recorded as the first discharge capacity of the battery. The first coulombic efficiency of the battery (%) = first discharge capacity / first charging capacity × 100%.

[0188] 2) Normal temperature cycle performance

[0189] At 25°C and normal pressure (0.1MPa), the battery is charged at a constant current of 0.5C to a voltage of 3.5V, and then discharged at a constant current of 1C to a voltage of 3.2V. This is considered one charge-discharge cycle. With the initial discharge capacity as 100%, the charge-discharge cycle is repeated 500 times. The test is stopped and the cycle capacity retention rate is recorded. The room temperature capacity retention rate is used as an indicator to evaluate the room temperature cycle performance of the battery.

[0190] 3) High temperature cycle performance

[0191] At 60°C and atmospheric pressure (0.1MPa), the battery was charged at a constant current of 0.5C to a voltage of 3.5V, then discharged at a constant current of 1C to a voltage of 3.2V. This constituted one charge-discharge cycle. The charge-discharge cycle was repeated 500 times, with the initial discharge capacity set as 100%. The test was then stopped and the cycle capacity retention rate was recorded. The high-temperature capacity retention rate was used as an indicator to evaluate the battery's high-temperature cycle performance.

[0192] 4) Gas production performance at room temperature

[0193] At room temperature (25°C), charge the battery at a constant current of 0.5C to 3.5V. After the battery is fully charged, use the water displacement method to test the initial volume of the battery. After the battery is stored at room temperature for 24 days, remove the battery. Use the water displacement method to test the battery volume at room temperature. Calculate the battery volume expansion rate based on the battery volume measured before storage. The volume expansion rate (%) of the battery after 24 days of storage at 25°C = (battery volume measured after storage / battery volume measured before storage) - 1.

[0194] 5) High temperature gas production performance

[0195] At room temperature (25°C), charge the battery to 3.5V at a constant current of 0.5C. After the battery is fully charged, the initial volume of the battery is tested by the drainage method. After the battery is stored in an oven at 60°C for 24 days, take out the battery. Let it stand for 60 minutes at room temperature. Test the battery volume by the drainage method within 60 minutes after cooling to room temperature. Calculate the battery volume expansion rate based on the battery volume tested before storage. The volume expansion rate (%) of the battery after storage at 60°C for 24 days = (battery volume measured after storage / battery volume measured before storage) - 1.

[0196] 3. Analysis of test results of various embodiments and comparative examples

[0197] Batteries of various examples and comparative examples were prepared according to the above methods, and various performance parameters were measured. The results are shown in Table 1 below.

[0198]

[0199]

[0200]

[0201] According to the above results, the sodium ion batteries in Examples 1 to 36 include a positive electrode sheet, a negative electrode sheet, and an electrolyte. The negative electrode sheet includes a negative electrode current collector of aluminum foil and a carbon nanotube primer layer formed on the surface of the aluminum foil. The electrolyte includes a first sodium salt, and the first sodium salt includes at least one of a sulfur-containing organic sodium salt and a boron-containing organic sodium salt. The surface density of the carbon coating is X g / m 2 The mass content Y% of the first sodium salt based on the total mass of the electrolyte satisfies the following relationship: 0.84≤Y-0.01X≤5.84. From the comparison of Examples 1 to 5, 9 to 15 with Comparative Examples 1 to 2, 4 to 9, Examples 6 to 8 with Comparative Examples 10 to 11, and Example 35 with Comparative Example 3, it can be seen that by controlling the surface density X g / m 2 The mass content Y% of the first sodium salt based on the total mass of the electrolyte satisfies the relationship of 0.84≤Y-0.01X≤5.84, which can improve the high-temperature cycle retention rate of the sodium-ion battery, reduce the high-temperature thickness expansion rate of the sodium-ion battery, significantly improve the high-temperature cycle performance of the sodium-ion battery, reduce the high-temperature gas production of the sodium-ion battery, and improve the electrochemical performance and safety performance of the sodium-ion battery under high-temperature conditions. At the same time, the sodium-ion battery has good first coulombic efficiency, room-temperature cycle performance and low room-temperature gas production, which broadens the operating temperature of the sodium-ion battery.

[0202] As can be seen from Examples 1 to 15, the first sodium salt is sodium bis(fluoromethylsulfonyl)imide, sodium bis(fluoromethylsulfonyl)imide and sodium difluorooxalatoborate, sodium (fluorosulfonyl)(trifluoromethylsulfonyl)imide, sodium trifluoromethylsulfonate, sodium bis(trifluoromethylsulfonyl)imide, sodium salicylate benzenediol borate, sodium difluorooxalatoborate, or sodium bis(oxalatoborate). As can be seen from the comparison of Examples 1 to 5 and 9 to 15 with Comparative Examples 6 to 7, the first sodium salt comprises at least one of a sulfur-containing organic sodium salt and a boron-containing organic sodium salt, which can significantly improve the high-temperature cycle performance of sodium ion batteries and reduce the high-temperature gassing phenomenon of sodium ion batteries.

[0203] From the comparison of Examples 1, 11-12 with Example 10, it can be seen that the first sodium salt is sodium trifluoromethanesulfonate, sodium bis(fluoromethylsulfonyl)imide or sodium bis(trifluoromethylsulfonyl)imide, which can further improve the high-temperature cycle performance of the sodium ion battery and reduce the high-temperature gas production of the sodium ion battery. From the comparison of Examples 14-15 with Example 13, it can be seen that the first sodium salt is sodium difluorooxalatoborate or sodium bisoxalatoborate, which can improve the first coulombic efficiency and room-temperature cycle performance of the sodium ion battery, and the sodium ion battery has excellent high-temperature cycle performance and low high-temperature gas production.

[0204] As can be seen from Examples 1, 16 to 19, the surface density of the primer layer is 5 g / cm 2 ~50g / cm 2 Sodium-ion batteries have excellent high-temperature cycle performance, first coulombic efficiency and room-temperature cycle performance. At the same time, sodium-ion batteries have low high-temperature gas production and room-temperature gas production, which broadens the operating temperature of sodium-ion batteries.

[0205] From the comparison between Example 20 and Example 21, it can be seen that the inclusion of the second sodium salt in the electrolyte can improve the initial coulombic efficiency, room temperature cycle performance and high temperature cycle performance of the sodium ion battery, and reduce the room temperature and high temperature gas production phenomena of the sodium ion battery.

[0206] As can be seen from Examples 1 and 22 to 25, the second sodium salt is sodium hexafluorophosphate, sodium tetrafluoroborate, sodium hexafluoroarsenate, sodium perchlorate or sodium trifluoroacetate, and the sodium ion battery has excellent high-temperature cycle performance, first coulombic efficiency and room-temperature cycle performance. At the same time, the sodium ion battery has low room-temperature gas production and high-temperature gas production, which broadens the operating temperature of the sodium ion battery.

[0207] From the comparison of Examples 1 to 5, 26 to 27, and 30 to 34 with Examples 28 to 29, it can be seen that the mass content Y% of the first sodium salt based on the total mass of the electrolyte and the mass content Z% of the second sodium salt based on the total mass of the electrolyte satisfy the following relationship: Y + Z ≥ 3, which can improve the initial coulombic efficiency, room temperature cycle performance, and high temperature cycle performance of the sodium ion battery. From the comparison of Examples 1 to 5, 27, and 30 to 34 with Examples 26 and 28 to 29, it can be seen that the mass content Y% of the first sodium salt based on the total mass of the electrolyte and the mass content Z% of the second sodium salt based on the total mass of the electrolyte satisfy the following relationship: Z / Y ≥ 1.21, which can improve the initial coulombic efficiency, room temperature cycle performance, and high temperature cycle performance of the sodium ion battery. From the comparison of Examples 1 to 5, 27, 30 to 34 with Examples 26, 28 to 29, it can be seen that the mass content Y% of the first sodium salt based on the total mass of the electrolyte and the mass content Z% of the second sodium salt based on the total mass of the electrolyte satisfy the following relationship: Y+Z≥3 and Z / Y≥1.21, which can improve the first coulombic efficiency of the sodium ion battery, the room temperature cycle performance and the high temperature cycle performance of the sodium ion battery.

[0208] From the comparison of Examples 1 to 5, 26 to 28, and 30 to 34 with Example 29, it can be seen that the mass content of the second sodium salt is 1% to 40%, based on the total mass of the electrolyte, which can improve the initial coulombic efficiency, room temperature cycle performance, and high temperature cycle performance of the sodium ion battery, and reduce the high temperature gas production performance of the sodium ion battery. From the comparison of Examples 1 to 5, 31 to 33 with Examples 26 to 30 and 34, it can be seen that the mass content of the second sodium salt is 7% to 35%, based on the total mass of the electrolyte, which can improve the initial coulombic efficiency of the sodium ion battery, while making the battery have excellent high temperature cycle performance and room temperature cycle performance, and have low high temperature gas production.

[0209] From the comparison of Examples 1 to 5, 26 to 28, and 30 to 34 with Example 29, it can be seen that the mass content of the solvent is 50% to 98%, based on the total mass of the electrolyte, which can improve the first coulombic efficiency, room temperature cycle performance, and high temperature cycle performance of the sodium ion battery, and reduce the high temperature gas production performance of the sodium ion battery. From the comparison of Examples 1 to 5, 31 to 34 with Examples 26 to 30, it can be seen that the mass content of the solvent is 50% to 90%, based on the total mass of the electrolyte, which can improve the first coulombic efficiency and high temperature cycle performance of the sodium ion battery, and at the same time, the sodium ion battery has excellent room temperature cycle performance and low high temperature gas production.

[0210] From the comparison of Examples 1 and 36 with Example 35, it can be seen that ether solvents can improve the first coulombic efficiency, room temperature cycle performance and high temperature cycle performance of sodium ion batteries, reduce the room temperature and high temperature gas production phenomena of sodium ion batteries, improve the electrochemical properties and safety performance of sodium ions, and broaden the operating temperature of sodium ion batteries.

Claims

1. A sodium ion battery comprising a positive electrode sheet, a negative electrode sheet and an electrolyte, characterized in that: The negative electrode plate includes a negative electrode current collector and a primer layer formed on the surface of the negative electrode current collector. The electrolyte includes a first sodium salt, and the first sodium salt includes at least one of a sulfur-containing organic sodium salt and a boron-containing organic sodium salt. The sodium ion battery satisfies the following relationship: 0.84≤Y-0.01X≤5.84, Where X g / m 2 is the areal density of the primer layer, and Y% is the mass content of the first sodium salt, based on the total mass of the electrolyte.

2. The sodium ion battery according to claim 1, characterized in that The anion of the sulfur-containing organic sodium salt comprises at least one of the structures shown in Formula I and Formula II, Wherein R1 and R2 are each independently selected from at least one of fluorine, substituted or unsubstituted C1-C6 alkyl, and R3 is a substituted or unsubstituted C1-C6 alkyl.

3. The sodium ion battery according to claim 1 or 2, wherein the sulfur-containing organic sodium salt comprises one or more of sodium trifluoromethanesulfonate, sodium bis(fluoromethylsulfonyl)imide, sodium bis(trifluoromethylsulfonyl)imide, and sodium (fluorosulfonyl)(trifluoromethylsulfonyl)imide, and can be selected from one or more of sodium trifluoromethanesulfonate, sodium bis(fluoromethylsulfonyl)imide, and sodium bis(trifluoromethylsulfonyl)imide.

4. The sodium ion battery according to any one of claims 1 to 3, wherein the boron-containing organic sodium salt comprises one or more of sodium tetraphenylborate, sodium bis(salicylate-2-)borate, sodium salicylate benzenediol borate, sodium difluorooxalatoborate, and sodium bisoxalatoborate, and may be one or two of sodium difluorooxalatoborate and sodium bisoxalatoborate.

5. The sodium ion battery according to any one of claims 1 to 4, characterized in that The surface density of the primer layer is X g / cm 2 5g / cm 2 ~50g / cm 2 .

6. The sodium ion battery according to any one of claims 1 to 5, characterized in that The primer layer contains one or more of superconductive carbon black, Ketjen black, acetylene black, carbon nanotubes, and graphene.

7. The sodium ion battery according to any one of claims 1 to 6, characterized in that The electrolyte further includes a second sodium salt, which includes at least one of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium hexafluoroarsenate, sodium perchlorate, and sodium trifluoroacetate.

8. The sodium ion battery according to claim 7, characterized in that The sodium ion battery satisfies the following relationship: Y+Z≥3 and / or Z / Y≥1.21, Wherein, Y% is the mass content of the first sodium salt, based on the total mass of the electrolyte; Z% is the mass content of the second sodium salt, based on the total mass of the electrolyte.

9. The sodium ion battery according to claim 7 or 8, characterized in that Based on the total mass of the electrolyte, the mass content of the second sodium salt is 1% to 40%, and can be optionally 7% to 35%.

10. The sodium ion battery according to any one of claims 1 to 9, characterized in that The electrolyte further comprises a solvent. Based on the total mass of the electrolyte, the mass content of the solvent is 50% to 98%, and optionally 50% to 90%.

11. The sodium ion battery according to claim 10, characterized in that The solvent includes an ether solvent, which can be selected from at least one of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol ethyl formate, ethylene glycol dibutyl ether, 1,3-dioxolane, 1,4-dioxane, tetrahydrofuran, methyltetrahydrofuran, 1,1,2,2-tetrafluoroethyl methyl ether, 2,2,3,3-tetrafluoropropyl methyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, bis-(2,2,2-trifluoroethyl) ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, methyl nonafluorobutyl ether, bis-(1,1,2,2-tetrafluoroethyl) ether, and difluoromethyl-2,2,2-trifluoroethyl ether.

12. The sodium ion battery according to any one of claims 1 to 11, characterized in that The sodium ion battery is a negative electrode-free sodium battery.

13. A battery module, characterized in that: A sodium ion battery comprising the sodium ion battery according to any one of claims 1 to 12.

14. A battery pack, characterized in that: The invention comprises at least one of the sodium ion battery according to any one of claims 1 to 12 and the battery module according to claim 13.

15. An electrical device, characterized in that: The invention comprises at least one selected from the sodium ion battery according to any one of claims 1 to 12, the battery module according to claim 13, and the battery pack according to claim 14.

Images