Electrolyte adaptive to high-voltage and high-power sodium ion battery and application of electrolyte

Abstract

The invention discloses a sodium ion battery electrolyte adaptive to high voltage and high power and application thereof.The sodium ion battery electrolyte comprises a first additive a and a second additive b, the first additive a is one or more of chain sulfonyl oxygen structure compounds, and the second additive b is one or more of chain or cyclic compounds containing sodium cations and boron anions at the same time; the positive electrode powder satisfies the following formula relation: 2.63 < = 100 (A + B) C / 0.01 (10C + D) < = 42.86, 0.1% < = A < = 3%, 0.2% < = B < = 2.5%, 1% < = C < = 3%, and 1% < = D < = 25%, A is the mass percentage content of the first additive a in the electrolyte, B is the mass percentage content of the second additive b in the electrolyte, C is the mass percentage content of the binder in the positive electrode powder, and D is the molar percentage content of the Cu element in the transition metal element; and the problems of rapid capacity attenuation, cyclic diving, sodium precipitation under high magnification and the like of the sodium battery are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium ion battery electrolyte additives, and in particular to a sodium ion battery electrolyte adapted to high voltage and high power and applications thereof. Background Art

[0002] Sodium is abundant and evenly distributed in the Earth's crust, offering advantages in both resource abundance and low cost for the development of new sodium-ion battery energy storage systems. This can reduce the cost of raw materials by 30% to 40%. Lithium and sodium belong to the same main group, and sodium-ion batteries and lithium-ion batteries share similar operating principles and production processes. However, sodium-ion batteries have lower energy density than lithium-ion batteries. Developing new high-capacity cathode materials and increasing the battery's operating voltage can significantly improve their energy density. Furthermore, as large-scale energy storage devices carrying other renewable energy conversion needs to possess rapid and stable charge and discharge capabilities. Therefore, there is an urgent need to develop electrolytes capable of high-voltage, rapid charge and discharge to broaden the application prospects of sodium-ion batteries.

[0003] At high potentials, especially >4.0V, the structural stability of the positive electrode material is poor; at the same time, it will accelerate the oxidative decomposition of the electrolyte on the surface of the positive electrode material, causing a series of side reactions; in addition, under high rate and high temperature conditions, the electrochemical stability of the binder also faces huge challenges. The reduced adhesion and the increase in particle cracks in the positive electrode material will lead to the peeling and shedding of the active material, which will inevitably lead to rapid capacity decay, cycle diving, severe sodium precipitation at high rates and other battery failure problems. Therefore, the development of an electrolyte that can take into account both dense film formation and low interfacial ion conduction resistance is an important research direction for improving fast charging capabilities and high-voltage cycle life. In view of this, the present invention needs to develop an electrolyte that is suitable for high voltage and high power, which is conducive to reducing capacity decay and having high battery cycle performance. Summary of the Invention

[0004] The present invention addresses the problems of rapid capacity decay, cycle drop, and sodium precipitation at high rates in sodium ion batteries in the prior art. Disclosed are a sodium ion battery electrolyte suitable for high voltage and high power, and its application. By optimizing the composition and content ratio of the sodium ion battery electrolyte additive, the binder in the battery positive electrode powder, and the Cu element in the positive electrode active material, an electrolyte is provided that can achieve both dense film formation and low interfacial ion conduction resistance. At the same time, the interaction between the active particles and the binder is enhanced, and the peeling of the active particles at high rates and high temperatures is avoided. This improves the high voltage stability and high power performance of the battery cell, further improving the performance of the battery.

[0005] The present invention is achieved through the following technical solutions:

[0006] The present invention first provides a sodium ion battery electrolyte adapted for high voltage and high power, comprising a first additive a and a second additive b;

[0007] The first additive a is selected from one or more compounds having a chain sulfonyloxy structure and has the following structure:

[0008]

[0009] wherein R1 is selected from an alkali metal atom, a C1-C6 halogenated or non-halogenated hydrocarbon group; R2 is selected from a halogen atom, a C1-C6 halogenated or non-halogenated hydrocarbon group, a C1-C6 halogenated or non-halogenated hydrocarbonoxy group, a C1-C6 halogenated or non-halogenated ester group or acyloxy group, and a C1-C6 halogenated or non-halogenated sulfonyloxy group;

[0010] The second additive b is selected from one or more chain compounds or cyclic compounds containing both sodium cations and boron anions;

[0011] The boron-containing anion contains one or more of -BO and -BF groups:

[0012] Having one or more of the following structural formulas:

[0013] NaBOB, NaBF4;

[0014] wherein R3 to R6 are independently selected from a hydrogen atom, a halogen atom, a C1 to C5 non-halogenated or halogenated alkyl group, a C2 to C5 non-halogenated or halogenated alkenyl group, or R3 and R4 together serve as a connecting oxygen atom to form a carbon-oxygen double bond with the carbon atom connected to the ring, or R5 and R6 together serve as a connecting oxygen atom to form a carbon-oxygen double bond with the carbon atom connected to the ring;

[0015] When R3 and R4 serve together as connecting oxygen atoms to form a carbon-oxygen double bond with the carbon atoms connected to the ring, and R5 and R6 serve together as connecting oxygen atoms to form a carbon-oxygen double bond with the carbon atoms connected to the ring, the second additive b is NaDFOB;

[0016] R7 to R11 are each selected from a hydrogen atom, a halogen atom, a C1 to C5 non-halogenated or halogenated alkyl group, or a C2 to C5 non-halogenated or halogenated alkenyl group;

[0017] The amounts of the first additive a and the second additive b in the electrolyte satisfy the following formula: 2.63≤100(A+B)C / 0.01(10C+D)≤42.86, and 0.1%≤A≤3%, 0.2%≤B≤2.5%, 1%≤C≤3%, 1%≤D≤25%, wherein A is the mass percentage of the first additive a in the electrolyte, B is the mass percentage of the second additive b in the electrolyte, C is the mass percentage of the binder in the positive electrode powder in the battery, and D is the molar percentage of the Cu element in the positive electrode material of the battery to all transition metal elements.

[0018] The above design of the present invention solves the problems of rapid battery capacity decay, poor cycle performance, and poor performance at high voltage and high rate by optimizing the first additive a, the second additive b, the percentage of the binder in the positive electrode powder, and the molar percentage of the Cu element in all transition metal elements; by matching different types of electrolyte additives, combining the optimization and adjustment of the additive content and ratio, the electrolyte additives are decomposed to form more CEI interface films with lower solubility, and a dense and lower impedance S-rich interface film is constructed, which is beneficial to the Na in the CEI layer. + The first additive a is an electrolyte that can achieve both dense film formation and low interfacial ion conduction resistance. With the action of the second additive b at an appropriate content, the stability of the battery at high voltage can be further improved. The second additive b, as a salt-based boron-containing compound, has a high HOMO value and will preferentially decompose at the positive electrode to form a dense and strong intermediate phase rich in boron, thereby improving the oxidation stability at high voltage. The presence of Cu element regulates the electrolyte additive in Cu 2+ The degree of decomposition of the inorganic component-rich cross-linked polymer passivation layer under catalytic action is controlled by combining and regulating the molar ratio of the Cu element in the transition metal to balance the structural stability and energy density. At the same time, the passivation layer interacts with the relatively regulated binder to construct a suitable network cross-linking structure, avoid the peeling of the positive electrode active material, and improve the cycle stability of the passivation film; the binder ensures the uniform dispersion of the electrode components, fully exerts the role of binding the active material, conductive agent and current collector, and does not affect the overall energy density of the battery cell due to excessive content. At the same time, it strengthens the interaction between the inorganic / cross-linked organic mixed passivation layer and the conductive bonding network; through the above design, the high voltage stability of the battery is improved, and the interaction between the active particles and the binder is enhanced, avoiding the peeling of the active particles at high voltage, thereby improving the overall cycle performance, stability at high voltage and rate performance, effectively preventing the positive electrode material from structural collapse, active particle fragmentation, transition metal dissolution, etc. at high voltage, high power and high temperature, thereby avoiding the rapid decay of the battery cell capacity and improving the cycle performance of the battery; at the same time, through the synergistic effect of the additives, the ion conductivity of the electrolyte is improved, and the high power performance of the battery is improved.

[0019] As a further solution, we prefer that the single amount of each component satisfies at least one of the following: 0.2%≤A≤2%, 0.5%≤B≤1.5%, 1.5%≤C≤2%, and / or 5%≤D≤12%.

[0020] As a further solution, each component satisfies the formula relationship of 10≤100(A+B)C / 0.01(10C+D)≤15.

[0021] As a further solution, the performance is better when 3≤D / (A+B)≤6 and 1≤B / A≤1.5 are satisfied while satisfying 0.2%≤A≤2%, 0.5%≤B≤1.5%, 1.5%≤C≤2%, and 5%≤D≤12%.

[0022] At this time, the number of cycles in which the normal temperature cycle capacity decays to 80% of the battery is ≥800, the DCR increase when the normal temperature cycle capacity decays to 80% is ≤25.88%, and the capacity retention rate after 100 cycles of 3C charge and discharge cycles at room temperature is ≥95%.

[0023] As a further embodiment, the first additive a is preferably one of R2 which is a halogen atom, a C1-C6 halogenated hydrocarbon group, a C1-C6 halogenated hydrocarbonoxy group, a C1-C6 halogenated ester group or acyloxy group, and a C1-C6 halogenated sulfonyloxy group.

[0024] As a further solution, the first additive a is preferably a halogen atom, wherein R2 is one of C1 to C6 halogenated sulfonyloxy groups.

[0025] As a further embodiment, the first additive a is preferably such that R2 is a halogen atom.

[0026] As a further embodiment, the first additive a preferably has R2 as a fluorine atom.

[0027] As a further embodiment, the second additive b is selected from one or more chain compounds or cyclic compounds containing both sodium cations and boron anions;

[0028] Having one or more of the following structural formulas:

[0029] NaBOB, NaBF4.

[0030] As a further preferred solution, the second additive b is preferably NaBOB, wherein R3 and R6 are both hydrogen atoms, R4 and R5 are one of C1-C5 non-halogenated or halogenated alkyl groups, or C2-C5 non-halogenated or halogenated alkenyl groups, or R3 and R4 serve together as a connecting oxygen atom to form a carbon-oxygen double bond with the carbon atoms connected to the ring, and R5 and R6 serve together as a connecting oxygen atom to form a carbon-oxygen double bond with the carbon atoms connected to the ring.

[0031] As a further preferred embodiment, the second additive b is preferably NaDFOB.

[0032] As a further solution, a high-voltage resistant sodium ion battery electrolyte also includes sodium salt and an organic solvent.

[0033] As a further embodiment, the sodium salt is one or more of sodium hexafluorophosphate, sodium perchlorate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethylsulfonyl)imide, sodium difluorophosphate, sodium nitrate, sodium hexafluoroantimonate, sodium hexafluoroarsenate, sodium difluorobis(oxaloyl)phosphate, and sodium tetrafluorooxaloylphosphate.

[0034] As a further embodiment, the sodium salt is sodium hexafluorophosphate.

[0035] As a further solution, the organic solvent is one or more of an ether solvent, an ester solvent, and an ionic liquid.

[0036] As a further embodiment, the ether solvent is selected from one or more of ether solvents containing hydroxyl groups, ether solvents containing a single ether bond, and ether solvents containing complex functional groups.

[0037] As a further embodiment, the complex functional group is selected from one or more of C1-C10 alkoxy, alkenyl, and alkynyl groups.

[0038] As a further solution, the hydroxyl-containing ether solvent is selected from one or more of dipropylene glycol butyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, propylene glycol monomethyl ether, triethylene glycol monomethyl ether, and tetraethylene glycol dimethyl ether.

[0039] As a further solution, the ether solvent containing a single ether bond is selected from one or more of cyclopentyl methyl ether, ethyl ether, and propyl ether.

[0040] As a further solution, the ether solvent containing complex functional groups is selected from one or more of butynediol dipropoxy ether, propargyl ether, and propargyl ether.

[0041] As a further solution, the ester solvent is selected from one or more of linear ester solvents and cyclic carbonate solvents.

[0042] As a further embodiment, the linear ester is selected from one or more of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethyl vinyl carbonate, methyl acetate, and propyl acetate.

[0043] As a further embodiment, the cyclic carbonate is selected from one or more of ethylene carbonate, fluoroethylene carbonate, propylene carbonate, and 1,2-propylene glycol carbonate.

[0044] As a further embodiment, the source of copper element in the positive electrode material is not limited, and copper element can be introduced into the positive electrode material in any feasible manner according to needs. As some optional ways, copper element can be directly used as one of the structural components of the positive electrode active material, or can be introduced into the positive electrode material as a positive electrode additive in the form of a copper-containing additive, such as CuO and the like.

[0045] As a further embodiment, the positive electrode active material is a metal layered oxide, and the general formula of the metal layered oxide is Na x Mn y M z O2, where 0.95 < x ≤ 1.05, 0.01 ≤ y ≤ 0.6, y + z = 1, and M represents a transition metal element with an unfilled d electron orbital, specifically including one or more of scandium (Sc), yttrium (Y), lanthanide elements (from lanthanum (La) to lutetium (Lu)), titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo), tungsten (W), copper (Cu), technetium (Tc), rhenium (Re), iron (Fe), ruthenium (Ru), osmium (Os), cobalt (Co), rhodium (Rh), iridium (Ir), nickel (Ni), palladium (Pd), platinum (Pt), silver (Ag), gold (Au), zinc (Zn), cadmium (Cd), and mercury (Hg).

[0046] As a further embodiment, M in the positive electrode active material containing copper element includes Cu.

[0047] As a further embodiment, an oil-based binder is used as the binder, and the binder includes at least one of a thermoplastic resin, an acrylic resin, sodium carboxymethyl cellulose, and styrene-butadiene rubber.

[0048] As a further embodiment, the thermoplastic resin includes at least one of polyvinylidene fluoride, a copolymer of vinylidene fluoride, polytetrafluoroethylene, a copolymer of vinylidene fluoride - hexafluoropropylene, a copolymer of tetrafluoroethylene - hexafluoropropylene, a copolymer of tetrafluoroethylene - perfluoroalkyl vinyl ether, a copolymer of ethylene - tetrafluoroethylene, a copolymer of vinylidene fluoride - tetrafluoroethylene, a copolymer of vinylidene fluoride - trifluoroethylene, a copolymer of vinylidene fluoride - trichloroethylene, a copolymer of vinylidene fluoride - fluoroethylene, a copolymer of vinylidene fluoride - hexafluoropropylene - tetrafluoroethylene, thermoplastic polyimide, polyethylene, and polypropylene.

[0049] As a further solution, the acrylic resin includes at least one of vinyl acrylate resin, methyl acrylate resin, butyl acrylate resin, acrylic styrene resin, acrylate resin, acrylate copolymer resin, acrylic resin, and acrylic emulsion resin.

[0050] As a further solution, the binder is polyvinylidene fluoride (PVDF).

[0051] The present invention also provides a sodium ion battery, comprising the electrolyte, a positive electrode sheet containing the positive electrode material, a negative electrode sheet containing the negative electrode material, and a separator.

[0052] As a further solution, the sodium ion battery is manufactured by forming the positive electrode sheet, the negative electrode sheet, and the isolation membrane into an electrode assembly through a winding process or a lamination process, and the preferred solution is the winding process.

[0053] As a further solution, the positive electrode material includes a positive electrode active material NaCu 1 / 10 Ni 3 / 10 Fe 3 / 10 Mn 3 / 10 O2, the binder polyvinylidene fluoride (PVDF), and also includes conductive carbon black Super-P, conductive agent CNT, solvent and positive electrode current collector aluminum foil.

[0054] As a further solution, the negative electrode material includes one or more of hard carbon, conductive agent Super P, thickener CMC, binder SBR and negative electrode current collector aluminum foil.

[0055] As a further solution, the outer packaging of the sodium ion battery is a bag-type soft package or an aluminum shell or a steel shell.

[0056] As a further solution, the shape of the sodium ion battery is not limited and can be cylindrical, square or any other shape. A preferred solution is a cylindrical aluminum shell.

[0057] The characteristics and beneficial effects of the present invention are:

[0058] (1) The present invention provides an electrolyte for sodium ion batteries adapted to high voltage and high power, which is an electrolyte that can achieve both dense film formation and low interface ion conduction resistance. This technical solution significantly improves the performance and stability of sodium ion batteries under high voltage, high temperature, and high rate conditions, helps to build a stable interface film, and enhances the interaction between the overall active particles and the binder. Together, they effectively prevent the positive electrode material from undergoing structural collapse, active particle breakage, transition metal dissolution, and excessive side reactions under high voltage, high temperature, and high rate conditions, thereby reducing the rapid growth of the cycle DCR and improving the battery's cycle performance under high temperature and high voltage conditions.

[0059] On the one hand, by regulating the content of the first additive a, the second additive b, the binder and the Cu in the positive electrode material to 0.1%≤A≤3%, 0.2%≤B≤2.5%, 1%≤C≤3%, 1%≤D≤25%, the first additive a and the second additive b in the transition metal ion Cu 2+ The mixed passivation layer of inorganic / cross-linked organic components rich in inorganic components is decomposed under the catalytic action of the catalyst. The inorganic components of the passivation layer have lower solubility, are denser and more stable, and to a certain extent inhibit the dissolution of transition metals, effectively prevent the structural collapse and active particle breakage of the positive electrode material under high voltage and high temperature, thereby avoiding the rapid attenuation of the battery cell capacity and improving the cycle performance of the battery; the content of the binder is controlled to ensure the uniform dispersion of the various components of the electrode, give full play to the role of bonding active substances, conductive agents and current collectors, and strengthen the interaction between the inorganic / cross-linked organic mixed passivation layer and the conductive bonding network; the Cu element plays a role in stabilizing the structure of the positive electrode material within a suitable range, and works together with the first additive a and the second additive b to enhance the stability of the positive electrode active particles and the conductive bonding network, thereby avoiding the peeling of the positive electrode particles at higher voltages.

[0060] On the other hand, under the condition of satisfying the formula of 2.63≤100(A+B)C / 0.01(10C+D)≤42.86, the relationship between the mass percentage of additives, binders and Cu ions in the positive electrode powder is balanced, and the energy density and structural stability are balanced. + The migration rate can significantly reduce the growth of interfacial resistance (DCR) during the cycle, which can optimize the stability of the battery cell at high voltage, slow down the growth of cycle DCR, and further improve the cycle performance at high temperature and high voltage.

[0061] (2) The present invention provides a sodium ion battery electrolyte suitable for high voltage and high power, which accurately controls the Cu 2+ The mass percentage of the positive electrode powder and the ratio of the electrolyte additives improve the stability of the battery at high voltage, build a three-dimensional electronic conduction network, significantly improve the electron transmission efficiency of the electrode, and reduce the interface impedance. 2+ When the mass percentage of the positive electrode powder and the electrolyte reaches a certain ratio, satisfying 3≤D / (A+B)≤6, a better balance is formed, avoiding Cu 2+ The risk of metal dissolution caused by excessive Cu 2+ The catalytic capacity of the first additive a and the second additive b is enhanced at high voltage and high rate. When the amount of the second additive b is 1 to 2 times that of the first additive a, the impedance increase is effectively reduced by synergistically optimizing the ion transmission efficiency and the performance of the dense passivation film, further enhancing the overall performance of the sodium-ion battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 The capacity retention rate of Example 1 and Comparative Example 1 of the present invention at 25°C, 2-4.3V, 1C / 1C charge-discharge cycle DETAILED DESCRIPTION

[0063] To facilitate understanding of the present invention, the following will provide a more comprehensive description of an electrolyte suitable for high-voltage and high-power sodium ion batteries and its applications in combination with the specific details and embodiments of the present invention, but this does not limit the scope of the present invention.

[0064] The present invention first provides an electrolyte adapted for high-voltage and high-power sodium ion batteries, comprising a first additive a and a second additive b;

[0065] The first additive a is selected from one or more compounds having a chain sulfonyloxy structure and has the following structure:

[0066]

[0067] wherein R1 is selected from an alkali metal atom, a C1-C6 halogenated or non-halogenated hydrocarbon group; R2 is selected from a halogen atom, a C1-C6 halogenated or non-halogenated hydrocarbon group, a C1-C6 halogenated or non-halogenated hydrocarbonoxy group, a C1-C6 halogenated or non-halogenated ester group or acyloxy group, and a C1-C6 halogenated or non-halogenated sulfonyloxy group;

[0068] The second additive b is selected from one or more chain compounds or cyclic compounds containing both sodium cations and boron anions;

[0069] The boron-containing anion contains one or more of -BO and -BF groups:

[0070] Having one or more of the following structural formulas:

[0071] NaBOB, NaDFOB, NaBF4;

[0072] wherein R3 to R6 are independently selected from a hydrogen atom, a halogen atom, a C1 to C5 non-halogenated or halogenated alkyl group, a C2 to C5 non-halogenated or halogenated alkenyl group, or R3 and R4 together serve as a connecting oxygen atom to form a carbon-oxygen double bond with the carbon atom connected to the ring, or R5 and R6 together serve as a connecting oxygen atom to form a carbon-oxygen double bond with the carbon atom connected to the ring;

[0073] When R3 and R4 serve together as connecting oxygen atoms to form a carbon-oxygen double bond with the carbon atoms connected to the ring, and R5 and R6 serve together as connecting oxygen atoms to form a carbon-oxygen double bond with the carbon atoms connected to the ring, the second additive b is NaDFOB;

[0074] R7 to R11 are each selected from a hydrogen atom, a halogen atom, a C1 to C5 non-halogenated or halogenated alkyl group, or a C2 to C5 non-halogenated or halogenated alkenyl group;

[0075] The amounts of the first additive a and the second additive b in the electrolyte satisfy the following formula: 2.63≤100(A+B)C / 0.01(10C+D)≤42.86, and 0.1%≤A≤3%, 0.2%≤B≤2.5%, 1%≤C≤3%, 1%≤D≤25%, wherein A is the mass percentage of the first additive a in the electrolyte, B is the mass percentage of the second additive b in the electrolyte, C is the mass percentage of the binder in the positive electrode powder in the battery, and D is the molar percentage of the Cu element in the positive electrode material of the battery to all transition metal elements.

[0076] The above design of the present invention solves the problems of rapid battery capacity decay, poor cycle performance, and poor performance at high voltage and high rate by optimizing the first additive a, the second additive b, the percentage of the binder in the positive electrode powder, and the molar percentage of the Cu element in all transition metal elements; by matching different types of electrolyte additives and optimizing and adjusting the ratio of the additive content, the electrolyte additives are decomposed to form more CEI interface films with lower solubility, thereby constructing a dense and lower impedance S-rich interface film that is beneficial to the Na in the CEI layer. + The first additive a is an electrolyte that can achieve both dense film formation and low interfacial ion conduction resistance. With the action of the second additive b at an appropriate content, the stability of the battery at high voltage can be further improved. The second additive b, as a salt-based boron-containing compound, has a high HOMO value and will preferentially decompose at the positive electrode to form a dense and strong intermediate phase rich in boron, thereby improving the oxidation stability at high voltage. The presence of Cu element regulates the electrolyte additive in Cu 2+The degree of decomposition of the inorganic component-rich cross-linked polymer passivation layer under catalytic action is controlled by combining and regulating the molar ratio of the Cu element in the transition metal to balance the structural stability and energy density. At the same time, the passivation layer interacts with the relatively regulated binder to construct a suitable network cross-linking structure, avoid the peeling of the positive electrode active material, and improve the cycle stability of the passivation film; the binder ensures the uniform dispersion of the electrode components, fully plays the role of binding the active material, conductive agent and current collector, and does not affect the overall energy density of the battery cell due to excessive content. At the same time, it strengthens the interaction between the inorganic / cross-linked organic mixed passivation layer and the conductive bonding network; through the above design, the high voltage stability of the battery is improved, and the interaction between the active particles and the binder is enhanced, avoiding the peeling of the active particles at high voltage, and improving the overall cycle performance, stability at high voltage and rate performance, effectively preventing the positive electrode material from structural collapse, active particle fragmentation, transition metal dissolution, etc. at high voltage and high temperature, thereby avoiding the rapid decay of the battery cell capacity and improving the battery's room temperature cycle performance; at the same time, through the synergistic effect of the additives, the ion conductivity of the electrolyte is improved, and the high power performance of the battery is improved.

[0077] As a further preferred example, we prefer that the single amount of each component satisfies at least one of the following: 0.2%≤A≤2%, 0.5%≤B≤1.5%, 1.5%≤C≤2%, and / or 5%≤D≤12%.

[0078] Preferably, 0.2%≤A≤2%, and the mass content of the first electrolyte additive a is controlled within a suitable range, which is more inclined to decompose and form more CEI interface films with lower solubility, build a dense and lower impedance S-rich interface film, and is beneficial to the Na in the CEI layer. + conductivity.

[0079] Preferably, 0.5%≤B≤1.5%. Controlling the mass content of the second electrolyte additive b within an appropriate range is more conducive to improving stability under high voltage. The salt-based boron-containing additive has a higher HOMO value and will preferentially decompose at the positive electrode to form a dense and strong boron-rich intermediate phase, thereby improving the oxidation stability at high voltage.

[0080] Boron-containing salts are anionic salt compounds with boron atoms as coordination centers. They can form anionic complexes with large π conjugated structures by reacting with ligands such as alkoxy groups, and have the following characteristics: (1) The negative charge of the central boron atom is dispersed throughout the conjugated skeleton through the delocalization effect, significantly reducing the charge density of the anion; (2) The larger molecular size produces a steric effect, weakening the Coulomb interaction with sodium cations. The synergistic effect of these two aspects effectively improves the dissociation degree and solubility of the complex in organic solvents. It is worth noting that the electron-withdrawing group F, ketone group, etc. are introduced into the second additive b to further enhance the structural stability of the anion and promote the solvation of metal ions, thereby significantly optimizing the electrochemical performance of the electrolyte.

[0081] Preferably, 1.5%≤C≤2%, and the content of the binder is controlled within an appropriate range. Controlling the content of the binder within an appropriate range can ensure that the components of the electrode are evenly dispersed and give full play to the role of the binding active material, conductive agent and current collector, while not affecting the overall energy density of the battery cell due to excessive content. At the same time, it will strengthen the interaction between the inorganic / cross-linked organic mixed passivation layer and the conductive bonding network.

[0082] Preferably, 5%≤D≤12%, and the molar percentage of the Cu element in the positive electrode material is controlled within an appropriate range, which neither affects the role of the Cu element in stabilizing the structure of the positive electrode material, nor works together with the first additive a and the second additive b to enhance the stability of the positive electrode active particles and the conductive bonding network, thereby avoiding peeling of the positive electrode particles at higher voltages.

[0083] In a further preferred example, each component satisfies the formula relationship of 10≤100(A+B)C / 0.01(10C+D)≤15.

[0084] When the above range is met, the high voltage stability of the obtained battery cell is significantly improved. This is mainly because the synergistic relationship between the content of the first additive a, the content of the second additive b, the content of Cu and the content of the binder has a very significant impact on the interface stability and the stability between the positive electrode active particles. When the above relationship is not met, under high voltage and high temperature conditions, due to the poor interface stability and the stability between the positive electrode active particles, the dissolution of the transition metal and the decomposition of the electrolyte will be accelerated, and the cycle performance of the battery cell will be deteriorated, especially the cycle performance under high temperature and high voltage cycles, and may even lead to some safety problems.

[0085] As a further example, when the above conditions of 0.2% ≤ A ≤ 2%, 0.5% ≤ B ≤ 1.5%, 1.5% ≤ C ≤ 2%, and 5% ≤ D ≤ 12% are met, the performance is further improved when 3 ≤ D / (A + B) / C ≤ 6 and 1 ≤ B / A ≤ 1.5 are met. In this case, the number of cycles in which the normal temperature cycle capacity decays to 80% is ≥ 800, the DCR increase in which the normal temperature cycle capacity decays to 80% is ≤ 25.88%, and the capacity retention rate after 100 cycles of 3C charge and discharge at room temperature is ≥ 95%.

[0086] As a further preferred example, R1 in the first additive a provided by the present invention is preferably a sodium atom.

[0087] Sodium sulfonate salt as an electrolyte additive can effectively reduce the viscosity of the electrolyte, thereby reducing internal resistance, improving the charge and discharge efficiency of the battery, improving the ionic conductivity of the electrolyte, and thus improving the overall performance of the battery.

[0088] As an example, the first additive a is preferably one in which R2 is a halogen atom, a C1-C6 halogenated hydrocarbon group, a C1-C6 halogenated hydrocarbonoxy group, a C1-C6 halogenated ester group or acyloxy group, or a C1-C6 halogenated sulfonyloxy group.

[0089] As a further preferred example, the first additive a is preferably one in which R2 is a halogen atom, or a halogenated sulfonyloxy group with C1 to C6.

[0090] As a further preferred example, the first additive a preferably has R2 as a halogen atom.

[0091] As a further preferred example, the first additive a provided by the present invention is selected from One or more of .

[0092] As an example, the second additive b is selected from one or more chain compounds or cyclic compounds containing both sodium cations and boron anions;

[0093] Having one or more of the following structural formulas:

[0094] NaBOB, NaBF4.

[0095] As a further preferred example, the second additive b is preferably NaBOB, wherein R3 and R6 are both hydrogen atoms, R4 and R5 are one of C1-C5 non-halogenated or halogenated alkyl groups, or C2-C5 non-halogenated or halogenated alkenyl groups, or R3 and R4 serve together as a connecting oxygen atom to form a carbon-oxygen double bond with the carbon atoms connected to the ring, and R5 and R6 serve together as a connecting oxygen atom to form a carbon-oxygen double bond with the carbon atoms connected to the ring.

[0096] As a further preferred example, the second additive b is preferably NaDFOB.

[0097] As a further preferred example, the present invention also provides a second additive b selected from

[0098] One or more of .

[0099] As an example, a high-voltage resistant sodium ion battery electrolyte also includes sodium salt and an organic solvent.

[0100] Illustratively, the sodium salt is one or more of sodium hexafluorophosphate, sodium perchlorate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethylsulfonyl)imide, sodium difluorophosphate, sodium nitrate, sodium hexafluoroantimonate, sodium hexafluoroarsenate, sodium difluorobis(oxalophosphate), and sodium tetrafluorooxalophosphate.

[0101] As a preferred example, the sodium salt is sodium hexafluorophosphate (NaPF6).

[0102] Illustratively, the organic solvent is one or more of an ether solvent, an ester solvent, and an ionic liquid.

[0103] As an example, the ether solvent is selected from one or more of an ether solvent containing a hydroxyl group, an ether solvent containing a single ether bond, and an ether solvent containing a complex functional group;

[0104] The complex functional group is selected from one or more of C1-C10 alkoxy, alkenyl, and alkynyl groups;

[0105] The hydroxyl-containing ether solvent is selected from one or more of dipropylene glycol butyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, propylene glycol monomethyl ether, triethylene glycol monomethyl ether, and tetraethylene glycol dimethyl ether.

[0106] The ether solvent containing a single ether bond is selected from one or more of cyclopentyl methyl ether, ethyl ether, and propyl ether.

[0107] The ether solvent containing complex functional groups is selected from one or more of butynediol dipropoxy ether, propargyl ether, and propargyl ether;

[0108] Exemplarily, the ester solvent is selected from one or more of linear ester solvents and cyclic carbonate solvents.

[0109] The linear ester solvents are selected from one or more of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, vinyl acetate, methyl acetate, and propyl acetate.

[0110] The cyclic carbonate solvents are selected from one or more of ethylene carbonate, fluorinated ethylene carbonate, propylene carbonate, and 1,2-propylene glycol carbonate.

[0111] The source of copper element in the positive electrode material is not limited, and copper element can be introduced into the positive electrode material in any feasible way according to needs. As some optional ways, copper element can be directly used as one of the structural components of the positive electrode active material, or can be introduced into the positive electrode material as a positive electrode additive in the form of a copper-containing additive, such as CuO.

[0112] Exemplarily, the positive electrode active material is a metal layered oxide, and the general formula of the metal layered oxide is Na x Mn y M z O2, where 0.95 < x ≤ 1.05, 0.01 ≤ y ≤ 0.6, y + z = 1, and M represents a transition metal element with unfilled d electron orbitals, specifically including scandium (Sc), yttrium (Y), lanthanide elements (from lanthanum (La) to lutetium (Lu)), titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo), tungsten (W), copper (Cu), technetium (Tc), rhenium (Re), iron (Fe), ruthenium (Ru), osmium (Os), cobalt (Co), rhodium (Rh), iridium (Ir), nickel (Ni), palladium (Pd), platinum (Pt), copper (Cu), silver (Ag), gold (Au), zinc (Zn), cadmium (Cd), mercury (Hg), etc.

[0113] Exemplarily, M in the positive electrode active material includes Cu.

[0114] Exemplarily, an oil-based binder is used as the binder, and the binder includes at least one of a thermoplastic resin, an acrylic resin, sodium carboxymethyl cellulose, and styrene-butadiene rubber.

[0115] Illustratively, the thermoplastic resin includes at least one of polyvinylidene fluoride, a copolymer of vinylidene fluoride, polytetrafluoroethylene, a copolymer of vinylidene fluoride-hexafluoropropylene, a copolymer of tetrafluoroethylene-hexafluoropropylene, a copolymer of tetrafluoroethylene-perfluoroalkyl vinyl ether, a copolymer of ethylene-tetrafluoroethylene, a copolymer of vinylidene fluoride-tetrafluoroethylene, a copolymer of vinylidene fluoride-trifluoroethylene, a copolymer of vinylidene fluoride-trichloroethylene, a copolymer of vinylidene fluoride-fluoroethylene, a copolymer of vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene, thermoplastic polyimide, polyethylene, and polypropylene.

[0116] As an example, the acrylic resin includes at least one of vinyl acrylate resin, methyl acrylate resin, butyl acrylate resin, acrylic styrene resin, acrylate resin, acrylate copolymer resin, acrylic resin, and acrylic emulsion resin.

[0117] As a preferred example, the binder is polyvinylidene fluoride (PVDF).

[0118] The present invention also provides a sodium ion battery, comprising the electrolyte, a positive electrode sheet containing the positive electrode material, a negative electrode sheet containing the negative electrode material, and a separator.

[0119] The sodium ion battery is manufactured by winding the positive electrode sheet, the negative electrode sheet, and the separator into an electrode assembly through a winding process or a lamination process, and the preferred solution is the winding process.

[0120] The positive electrode sheet includes a positive electrode active material NaCu 1 / 10 Ni 3 / 10 Fe 3 / 10 Mn 3 / 10 O2, the binder polyvinylidene fluoride (PVDF), and also includes conductive carbon black Super-P, conductive agent CNT, solvent and positive electrode current collector aluminum foil.

[0121] The negative electrode sheet includes one or more of hard carbon, a conductive agent SuperP, a thickener CMC, a binder SBR and a negative electrode current collector aluminum foil.

[0122] The outer packaging of the sodium ion battery is a bag-type soft package or an aluminum shell or a steel shell.

[0123] The shape of the sodium ion battery is not limited and can be cylindrical, square or any other shape. The preferred embodiment is a cylindrical aluminum shell.

[0124] As a specific embodiment of the present invention, the following detailed cases are provided:

[0125] Example 1:

[0126] This embodiment provides a sodium ion battery, which includes a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte.

[0127] The positive electrode sheet includes a positive electrode active material NaCu 1 / 10 Ni 3 / 10 Fe 3 / 10 Mn 3 / 10 O2, conductive carbon black Super-P, conductive agent CNT, binder polyvinylidene fluoride (PVDF) and positive electrode current collector aluminum foil, the average pore radius distribution range of the positive electrode sheet is 6 μm;

[0128] The negative electrode sheet includes a negative electrode material layer and a negative electrode current collector aluminum foil, wherein the negative electrode material layer includes negative electrode active material hard carbon, conductive carbon black Super-P, binder styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC), and the average pore radius distribution range of the negative electrode sheet is 50 μm;

[0129] Preparation of the electrolyte: In an argon atmosphere, the environmental indicators of the glove box are H2O≤0.5ppm, O2≤0.5ppm, first, the solvents propylene carbonate (PC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a mass ratio of 30:50:20, and then 1M sodium salt NaPF6 is dissolved in the mixed solvent, and then the first additive a-1 and the second additive b-1 are added and stirred evenly to obtain an electrolyte; based on the total mass of the electrolyte, the mass content of the first additive a-1 is 1%, and the mass content of the second additive b-1 is 1%.

[0130] Preparation of the positive electrode sheet: the positive electrode active material NaCu 1 / 10 Ni 3 / 10 Fe 3 / 10 Mn 3 / 10 O2, conductive agent SuperP, conductive agent CNT, and binder PVDF are dissolved in solvent N-methyl-2-pyrrolidone (NMP) in a mass ratio of 96.5:1.5:0.5:1.5 (that is, the mass proportion of binder PVDF in the positive electrode powder is 1.5%). After stirring evenly, a positive electrode slurry is obtained with a slurry viscosity of 5000±1000mPa·s and a solid content of 65±0.5wt%. The obtained positive electrode slurry is then evenly coated on aluminum foil, and then dried, cold pressed, and cut to obtain positive electrode sheets.

[0131] Preparation of the negative electrode sheet: The negative electrode active material hard carbon, the conductive agent Super P, the thickener CMC, and the binder SBR are mixed in a mass ratio of 94:2:1.5:2.5, and deionized water is added and stirred uniformly to obtain a negative electrode slurry. The slurry viscosity is adjusted to 4500±500mPa·s and the solid content is 50±0.5wt%; the slurry is then coated on the negative electrode current collector aluminum foil, and then dried, cold pressed, and slit to obtain the negative electrode sheet.

[0132] Preparation of the sodium ion battery: The positive electrode sheet, the negative electrode sheet, and the separator are formed into an electrode assembly through a winding process or a lamination process. This embodiment adopts the winding process.

[0133] The outer packaging of the sodium ion battery can be a bag-type soft package or an aluminum shell, steel shell, etc. The shape of the sodium ion battery is not limited and can be cylindrical, square or any other shape. This embodiment uses a cylindrical aluminum shell.

[0134] Under the above conditions, the following tests were performed:

[0135] Normal temperature cycle test: At room temperature (25±2°C), charge and discharge cycles are performed at 1C / 1C with a voltage range of 2 to 4.3V. The number of cycles required for the capacity to decay to 80% is recorded.

[0136] Cycling DCR growth test: record the DCR at the beginning of normal temperature cycling and the DCR when the normal temperature cycling capacity decays to 80%;

[0137] 3C cycle test: At room temperature of 25±2℃, voltage range of 2~4.2V, 3C / 3C charge and discharge cycle for 100 cycles, and record the capacity retention rate;

[0138] Examples 2 to 28, Comparative Examples 1 to 11:

[0139] A sodium ion battery was prepared and tested in the same manner as in Example 1, with some parameters modified. The parameter modifications and results are listed in Table 1.

[0140] The test results obtained in Examples 1 to 28 and Comparative Examples 1 to 11 are shown in Table 1:

[0141] Table 1

[0142]

[0143]

[0144] From Examples 1 to 29 and Comparative Examples 1 to 11, it can be observed that:

[0145] When 0.1%≤A≤3%, 0.2%≤B≤2.5%, 1%≤C≤3%, 1%≤D≤25% are satisfied at the same time, and the formula relationship of 2.63≤100(A+B)C / 0.01(10C+D)≤42.86 is satisfied, the number of cycles in which the normal temperature cycle capacity decays to 80% in the battery is ≥740, the DCR increase in which the normal temperature cycle capacity decays to 80% is ≤29.05%, and the capacity retention rate after 100 cycles of 3C charge and discharge cycles is ≥91.34%. The above parameters can ensure the most basic performance of the sodium ion battery. Compared with the comparative example, to a certain extent, the capacity retention rate of the cycle is greatly improved, and the charge and discharge cycle retention rate at high rate is improved.

[0146] Comparative Examples 1 to 9 show the relevant performance when 0.1%≤A≤3%, 0.2%≤B≤2.5%, 1%≤C≤3%, and 1%≤D≤25% are not satisfied. Under these parameters, the most basic performance of the sodium ion battery cannot be guaranteed.

[0147] Specifically, such as Figure 1 As shown, Example 1 and Comparative Example 1 are shown. At room temperature 25±2°C, charge and discharge cycles are performed at 1C / 1C with a voltage range of 2 to 4.3V. The number of cycles required for the capacity to decay to 80% is recorded. Example 1 is 830 cycles, and Comparative Example 1 is 291 cycles.

[0148] Comparative Examples 1-2 and 3 are respectively the cases where only the first additive a and only the second additive b are added, and no additive is added. Comparative Examples 4-5 are the cases where the content of the first additive a or the second additive b is excessive.

[0149] This shows that the first additive and the second additive have a synergistic effect in the formation and stabilization of the inorganic component-rich cross-linked polymer passivation layer and in inhibiting the dissolution of transition metals. The lack of either additive will lead to the instability of the SEI film, which is not conducive to the construction of a dense and complete S-rich interface film and reduces the cycle life at high temperature. 2+ Under catalysis, the sulfur-containing first additive a and the boron-containing second additive b decompose on the positive electrode surface to produce sulfate (such as Na2SO4), sulfonate (such as NaSO3R), Na x B y O z and B x O y The composition is a low-impedance, highly stable dense inorganic / cross-linked organic mixed passivation layer, in which the dense inorganic layer is anchored to the surface of the positive electrode material through chemical bonds, thereby improving the high-voltage stability of the positive electrode interface, and the cross-linked polymer organic is anchored to the conductive network formed by the binder and the conductive agent in the form of mechanical interlocking, thereby improving the stability of the positive electrode active material and the conductive bonding network.

[0150] Comparative Examples 6 and 7 show the situation when the adhesive is insufficient or excessive. The adhesive is usually used to fix the active material, the conductive agent and the current collector, and at the same time form a stable cross-linked network structure with the interface film to promote ion transport. Therefore, if the adhesive is insufficient, it may affect the structural stability and the active material will fall off, which will directly reduce the battery capacity. At the same time, if the internal resistance is high, the battery heating will be more serious, the charge and discharge efficiency will be reduced, and the rate performance may also be affected. Excessive penetration of the electrolyte forms an overly thick SEI film, which consumes the sodium source, further increases the internal resistance, and affects the lifespan. The dense inorganic layer is anchored to the surface of the positive electrode material in the form of a chemical bond, thereby improving the high voltage stability of the positive electrode interface. The cross-linked polymer is organically anchored to the conductive network formed by the binder and the conductive agent in a mechanically interlocked form, thereby improving the stability of the positive electrode active material and the conductive bonding network, significantly improving the stability of the positive electrode active material and the conductive bonding network, avoiding the serious phenomenon of positive electrode particle shedding under high voltage, and alleviating the cycle diving.

[0151] Comparative Examples 8 and 9 show the cases where Cu is not present or is excessive. Cu, as an important catalyst for electrolyte additives, can form a composite passivation layer rich in inorganic components and cross-linked polymers. Not adding Cu is not conducive to the formation of the passivation layer, which may cause the positive electrode active material to peel off and reduce the stability of the passivation layer structure. Transition metal ion Cu 2+ The outermost electron has a special d9 configuration with an unpaired electron, which has the ability to switch between different oxidation states. Under high potential, it can catalyze the decomposition of the first sulfur-containing additive a and the second boron-containing additive b on the positive electrode surface to produce a composite passivation layer. Although the excess Cu enhances the structural strength, it also enhances the Cu 2+ It affects the catalytic ability of electrolyte additives but is not conducive to the transfer of electrons and ions, reduces the Na+ diffusion coefficient, increases transition metal dissolution and interface deterioration, and reduces rate performance.

[0152] In particular, in Comparative Examples 10 and 11, the single parameters all satisfy 0.1%≤A≤3%, 0.2%≤B≤2.5%, 1%≤C≤3%, and 1%≤D≤25%, but do not satisfy the formula relationship of 2.63≤100(A+B)C / 0.01(10C+D)≤42.86. The results are also poor, and the number of cycles in which the capacity decays to 80% in the battery is ≤390, the DCR increase in the normal temperature cycle capacity decay to 80% is ≥39.68%, and the capacity retention rate after 100 cycles of 3C charge and discharge cycles is ≤78.23%. This shows that even if the respective conditions are met individually, if 2.63≤100(A+B)C / 0.01(10C+D)≤42.86 is not satisfied, the performance requirements cannot be met.

[0153] By regulating the content of the first additive a, the second additive b, the binder, and Cu in the positive electrode material, the stability of the battery at high voltage can be optimized, and the performance of the battery at high temperature, high voltage, and high rate can be further improved;

[0154] Under this formula, the mass percentage C of the binder in the positive electrode powder is an important coefficient. It plays a core role in bonding the active material particles, conductive agent (such as carbon black) and current collector (aluminum foil) to form a stable electrode structure. Insufficient bonding force leads to the separation of active material particles and current collector, increased electrode brittleness, and easy cracking during coating. Excessive binder covers the surface of the active material, hindering electron / ion transmission. The binder is an electrochemically inert substance. If the proportion is too high, the proportion of active material will be diluted. At the same time, the positive electrode powder with too high a binder content will also make the pole piece too hard and prone to breakage during winding or stacking. The right amount of binder can ensure that the components of the electrode are evenly dispersed and give full play to the role of bonding active material, conductive agent and current collector, without affecting the overall energy density of the battery cell due to excessive content.

[0155] The binder and Cu ions both play a role in mechanical support and structural stability. At the same time, the Cu ions dissolved in Cu 2+ It can catalyze the decomposition of electrolyte additives to generate a composite passivation layer rich in inorganic components and cross-linked polymers. This formula shows that a high Cu content can improve structural stability, but it increases the Cu 2+ Dissolution risk requires more electrolyte additives and binders to inhibit dissolution and enhance electrode adhesion; low Cu content reduces the dissolution risk but sacrifices energy density, requiring a lower binder content to optimize conductivity.

[0156] Therefore, when the formula relationship of 2.63≤100(A+B)C / 0.01(10C+D)≤42.86 is satisfied, the relationship between the mass percentage of additives and binders in the positive electrode powder and Cu ions is balanced, and the energy density and structural stability performance are balanced.

[0157] As a further preferred example, according to Examples 1 to 29, 0.2%≤A≤2% is further preferred as the mass percentage of the first additive a, 0.5%≤B≤1.5% is preferred as the mass percentage of the second additive b, 1.5%≤C≤2% is preferred as the mass percentage of the binder in the battery to the positive electrode powder, and 5%≤D≤12% is preferred as the molar percentage of Cu element in the positive electrode material of the battery to all transition metal elements.

[0158] When 0.2%≤A≤2%, 0.5%≤B≤1.5%, 1.5%≤C≤2%, and 5%≤D≤12%, the performance of the sodium ion battery is further improved by optimizing the content range of each component.

[0159] As a further preferred example, when 0.2%≤A≤2%, 0.5%≤B≤1.5%, 1.5%≤C≤2%, and 5%≤D≤12% are satisfied, 10≤100(A+B)C / 0.01(10C+D)≤15 is preferably satisfied; the embodiments under this condition all meet the following conditions: the number of cycles in which the capacity of the battery decays to 80% is ≥790, the DCR increase in the normal temperature cycle capacity decay to 80% is ≤26%, and the capacity retention rate after 100 cycles of 3C charge and discharge cycles is ≥94.9%.

[0160] Therefore, while satisfying the mass percentage of different electrolyte additives and binders in the positive electrode powder and the molar percentage of Cu element in all transition metal elements within a certain range, calculating and further optimizing the 100(A+B)C / 0.01(10C+D) range has important practical significance for improving and optimizing the performance of sodium-ion batteries.

[0161] As a further example, when the above 0.2%≤A≤2%, 0.5%≤B≤1.5%, 1.5%≤C≤2%, and 5%≤D≤12% are satisfied, the performance is better when 3≤D / (A+B)≤6 and 1≤B / A≤1.5 are satisfied.

[0162] At this time, the number of cycles in which the normal temperature cycle capacity decays to 80% of the battery is ≥800, the DCR increase when the normal temperature cycle capacity decays to 80% is ≤25.88%, and the capacity retention rate after 100 cycles of 3C charge and discharge cycles at room temperature is ≥95%.

[0163] Examples 1, 12, 13, and 15 shown in the table are significantly better than Examples 9, 10, 11, and 14. This may be due to the ratio between Cu and electrolyte additives. Although a relatively excessive amount of Cu can enhance the stability of the electrode structure, it may also lead to the formation of Cu 2+ Dissolution is out of control. When the additive is relatively excessive, it may lead to excessively thick interfacial films and a surge in impedance. When a certain balance is reached between Cu and the electrolyte additive, the relevant performance can be stabilized. When the addition amount of electrolyte additive b is 1 to 2 times that of the first additive, the impedance growth rate is effectively reduced by synergistically optimizing ion transmission efficiency and dense passivation film performance, further enhancing the overall performance of the sodium-ion battery. Therefore, when 3≤D / (A+B)≤6 and 1≤B / A≤1.5 are met, the performance is relatively good.

[0164] Comparing Examples 1, 5, 6, 7, and 8 with Example 29, when R2 in the first additive a is a halogen, a C1-C6 halogenated hydrocarbon group, a C1-C6 halogenated hydrocarbonoxy group, a C1-C6 halogenated ester group or acyloxy group, or a C1-C6 halogenated sulfonyloxy group, it is superior to a C1-C6 non-halogenated hydrocarbon group. More preferably, comparing Examples 1 and 8 with Examples 5, 6, and 7, when R2 in the first additive a is a halogen or a C1-C6 halogenated sulfonyloxy group, the relevant performance is even better. It is further preferred that R2 is a halogen.

[0165] This may be because the highly electronegative halogen reduces the electron cloud density of oxygen atoms through a strong electron-withdrawing effect, making the molecules more likely to participate in the reaction on the electrode surface and promote the formation of a stable SEI film. The electronic effect of non-halogenated hydrocarbon oxygen groups, non-halogenated ester groups or acyloxy groups is weaker. It may also be related to the fact that the steric hindrance of halogen atoms is smaller, which promotes the dispersion of additives and their rapid migration to the electrode surface.

[0166] By comparison of Examples 1, 2, 3, and 4, when the second additive b is a five-membered cyclic compound or a chain compound containing B, the relevant performance is better than that of a six-membered cyclic compound containing B, more preferably a five-membered cyclic compound containing B, further preferably, the second additive b is such that R3 and R6 are both hydrogen, R4 and R5 are one of C1-C5 non-halogenated or halogenated alkyl, C2-C5 non-halogenated or halogenated alkenyl, or NaDFOB, further preferably NaDFOB.

[0167] This technical solution significantly improves the stability of sodium-ion batteries under high voltage, helps to build a stable interface film, and enhances the interaction between the overall active particles and the binder. Together, they effectively prevent the positive electrode material from undergoing structural collapse, active particle breakage, and transition metal dissolution under high voltage and high temperature, thereby avoiding the rapid attenuation of the battery cell capacity and improving the battery's room temperature cycle performance. At the same time, through the synergistic effect of the additives, the ion conductivity of the electrolyte is improved, thereby improving the battery's performance under high temperature, high voltage, and high power.

[0168] It should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A sodium ion battery electrolyte suitable for high voltage and high power, characterized in that: comprising a first additive a and a second additive b; The first additive a is selected from one or more compounds having a chain sulfonyloxy structure and has the following structure: wherein R1 is selected from an alkali metal atom, a C1-C6 halogenated or non-halogenated hydrocarbon group; R2 is selected from a halogen atom, a C1-C6 halogenated or non-halogenated hydrocarbon group, a C1-C6 halogenated or non-halogenated hydrocarbonoxy group, a C1-C6 halogenated or non-halogenated ester group or acyloxy group, and a C1-C6 halogenated or non-halogenated sulfonyloxy group; The second additive b is selected from one or more chain compounds or cyclic compounds containing both sodium cations and boron anions; Having one or more of the following structural formulas: NaBOB、NaBF4; wherein R3 to R6 are independently selected from a hydrogen atom, a halogen atom, a C1 to C5 non-halogenated or halogenated alkyl group, a C2 to C5 non-halogenated or halogenated alkenyl group, or R3 and R4 together serve as a connecting oxygen atom to form a carbon-oxygen double bond with the carbon atom connected to the ring, or R5 and R6 together serve as a connecting oxygen atom to form a carbon-oxygen double bond with the carbon atom connected to the ring; R7 to R11 are each selected from a hydrogen atom, a halogen atom, a C1 to C5 non-halogenated or halogenated alkyl group, or a C2 to C5 non-halogenated or halogenated alkenyl group; The amounts of the first additive a and the second additive b in the electrolyte satisfy the following formula: 2.63≤100(A+B)C / 0.01(10C+D)≤42.86, and 0.1%≤A≤3%, 0.2%≤B≤2.5%, 1%≤C≤3%, 1%≤D≤25%, wherein A is the mass percentage of the first additive a in the electrolyte, B is the mass percentage of the second additive b in the electrolyte, C is the mass percentage of the binder in the positive electrode powder in the battery, and D is the molar percentage of the Cu element in the positive electrode material of the battery to all transition metal elements.

2. The sodium ion battery electrolyte adapted for high voltage and high power according to claim 1, characterized in that: A, B, C, and D also satisfy at least one of the following: 0.2%≤A≤2%, 0.5%≤B≤1.5%, 1.5%≤C≤2%, and 5%≤D≤12%; Further preferably, the sodium ion battery electrolyte also satisfies 10≤100(A+B)C / 0.01(10C+D)≤15; Further preferably, the sodium ion battery electrolyte also satisfies 3≤D / (A+B)≤6 and 1≤B / A≤1.

5.

3. The sodium ion battery electrolyte adapted for high voltage and high power according to claim 1, characterized in that: The first additive a is preferably one in which R2 is a halogen atom, a C1-C6 halogenated hydrocarbon group, a C1-C6 halogenated hydrocarbonoxy group, a C1-C6 halogenated ester group or acyloxy group, or a C1-C6 halogenated sulfonyloxy group; Preferably, the first additive a is preferably one of R2 being a halogen atom, a C1 to C6 halogenated sulfonyloxy group; Preferably, the first additive a preferably has R2 as a halogen atom.

4. The sodium ion battery electrolyte adapted for high voltage and high power according to claim 1, characterized in that: The second additive b is selected from one or more chain compounds or cyclic compounds containing sodium cations and boron anions; and has one or more of the following structural formulas: NaBOB、NaBF4; Preferably, the second additive b is NaBOB, wherein R3 and R6 are both hydrogen atoms, and R4 and R5 are one of C1-C5 non-halogenated or halogenated alkyl groups, or C2-C5 non-halogenated or halogenated alkenyl groups; or R3 and R4 serve together as a connecting oxygen atom, forming a carbon-oxygen double bond with the carbon atoms connected to the ring, and R5 and R6 serve together as a connecting oxygen atom, forming a carbon-oxygen double bond with the carbon atoms connected to the ring; Preferably, the second additive b is NaDFOB.

5. The sodium ion battery electrolyte adapted for high voltage and high power according to claim 1, characterized in that: The first additive a is selected from One or more of; The second additive b is selected from One or more of .

6. The sodium ion battery electrolyte adapted for high voltage and high power according to claim 1, characterized in that: Also includes sodium salts and organic solvents.

7. The sodium ion battery electrolyte adapted for high voltage and high power according to claim 6, characterized in that: The sodium salt is one or more of sodium hexafluorophosphate, sodium perchlorate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethylsulfonyl)imide, sodium difluorophosphate, sodium nitrate, sodium hexafluoroantimonate, sodium hexafluoroarsenate, sodium difluorobis(oxalophosphate), and sodium tetrafluorooxalophosphate; Preferably, the sodium salt is sodium hexafluorophosphate.

8. The sodium ion battery electrolyte adapted for high voltage and high power according to claim 6, characterized in that: The organic solvent is one or more of an ether solvent, an ester solvent, and an ionic liquid; Preferably, the ether solvent is selected from one or more of ether solvents containing hydroxyl groups, ether solvents containing a single ether bond, and ether solvents containing complex functional groups; Preferably, the complex functional group is selected from one or more of C1-C10 alkoxy, alkenyl, and alkynyl groups; Preferably, the hydroxyl-containing ether solvent is selected from one or more of dipropylene glycol butyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, propylene glycol monomethyl ether, triethylene glycol monomethyl ether, and tetraethylene glycol dimethyl ether; Preferably, the ether solvent containing a single ether bond is selected from one or more of cyclopentyl methyl ether, ethyl ether, and propyl ether; Preferably, the ether solvent containing complex functional groups is selected from one or more of butynediol dipropoxy ether, propargyl ether, and propargyl ether; Preferably, the ester solvent is selected from one or more of linear ester solvents and cyclic carbonate solvents; Preferably, the linear ester is selected from one or more of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethyl vinyl carbonate, methyl acetate, and propyl acetate; Preferably, the cyclic carbonate is selected from one or more of ethylene carbonate, fluoroethylene carbonate, propylene carbonate, and 1,2-propylene glycol carbonate.

9. The sodium ion battery electrolyte adapted for high voltage and high power according to claim 6, characterized in that: The source of the copper element in the positive electrode material includes directly being one of the structural components of the positive electrode active material and / or being introduced into the positive electrode material as a positive electrode additive in the form of a copper-containing additive; Preferably, the positive electrode active material is a metal layered oxide, and the general formula of the metal layered oxide is Na x Mn y M z O2, where 0.95 < x ≤ 1.05, 0.01 ≤ y ≤ 0.6, y + z = 1, and M represents a transition metal element with an unfilled d electron orbital, specifically including scandium (Sc), yttrium (Y), lanthanide elements (from lanthanum (La) to lutetium (Lu)), titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo), tungsten (W), copper (Cu), technetium (Tc), rhenium (Re), iron (Fe), ruthenium (Ru), osmium (Os), cobalt (Co), rhodium (Rh), iridium (Ir), nickel (Ni), palladium (Pd), platinum (Pt), copper (Cu), silver (Ag), gold (Au), zinc (Zn), cadmium (Cd), mercury (Hg), or one or more of them; Preferably, M in the positive electrode active material comprises Cu; Preferably, the binder uses an oil-based binder, and the binder includes at least one of a thermoplastic resin, an acrylic resin, sodium carboxymethyl cellulose, and styrene butadiene rubber; Preferably, the thermoplastic resin includes at least one of polyvinylidene fluoride, a copolymer of vinylidene fluoride, polytetrafluoroethylene, a copolymer of vinylidene fluoride-hexafluoropropylene, a copolymer of tetrafluoroethylene-hexafluoropropylene, a copolymer of tetrafluoroethylene-perfluoroalkyl vinyl ether, a copolymer of ethylene-tetrafluoroethylene, a copolymer of vinylidene fluoride-tetrafluoroethylene, a copolymer of vinylidene fluoride-trifluoroethylene, a copolymer of vinylidene fluoride-trichloroethylene, a copolymer of vinylidene fluoride-fluoroethylene, a copolymer of vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene, thermoplastic polyimide, polyethylene and polypropylene; Preferably, the acrylic resin includes at least one of vinyl acrylate resin, methyl acrylate resin, butyl acrylate resin, acrylic styrene resin, acrylate resin, acrylate copolymer resin, acrylic resin, and acrylic emulsion resin; Preferably, the binder is polyvinylidene fluoride (PVDF).

10. A sodium ion battery, characterized in that: The invention comprises the sodium ion battery electrolyte adapted for high voltage and high power as described in any one of claims 1 to 9, and further comprises a positive electrode sheet, a negative electrode sheet and a separator.

Images