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CN118281342B - Electrolyte additive, electrolyte and battery - Google Patents

Electrolyte additive, electrolyte and battery Download PDF

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Publication number
CN118281342B
CN118281342B CN202410695816.4A CN202410695816A CN118281342B CN 118281342 B CN118281342 B CN 118281342B CN 202410695816 A CN202410695816 A CN 202410695816A CN 118281342 B CN118281342 B CN 118281342B
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additive
positive electrode
electrolyte
battery
active material
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CN118281342A (en
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饶婷
谢添
宋晓艺
胡蕙涓
杨海东
王文楷
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Guangzhou Tinci Materials Technology Co Ltd
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Guangzhou Tinci Materials Technology Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/054—Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • General Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Inorganic Chemistry (AREA)
  • Secondary Cells (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

The application discloses an electrolyte additive, an electrolyte and a battery, and relates to the field of batteries, wherein the electrolyte additive comprises a first additive, a second additive and a third additive, the first additive comprises a silane additive containing unsaturated bonds, the second additive comprises a compound shown in a formula 3, and the third additive comprises a compound shown in a formula 4: R 11-R16 is selected from any one of the alkyl groups of H, C 1-C4 and the alkenyl groups of C 2-C4; n=0 or1, a is selected from C or O, X is selected from o=s=o or c=o, R 17 and R 18 are selected from H, 、And

Description

Electrolyte additive, electrolyte and battery
Technical Field
The application belongs to the field of batteries, and particularly relates to an electrolyte additive, electrolyte and a battery.
Background
The secondary battery, which is one of the most remarkable inventions in the 20 th century, has advantages of high specific energy, long cycle life, no memory, low self-discharge rate, and the like, and is widely used in various fields such as clothing and eating houses in the human society. With the development of secondary battery technology and the demand for high energy density, the demand for secondary batteries is increasing, such as for good stability in high temperature environments.
However, in a high-temperature environment, the oxidation activity of the positive electrode active material is improved, the stability is reduced, and the electrolyte can accelerate oxidative decomposition, such as oxidation reaction between the electrolyte and the positive electrode active material. Electrolyte is continuously oxidized on the surface of the positive electrode and deposited on the surface of the positive electrode, so that the internal resistance of the positive electrode is continuously increased, and the poor rate performance and the poor cycle stability of the battery are caused.
Disclosure of Invention
The present application aims to solve at least one of the technical problems in the related art to some extent. To this end, an object of the present application is to propose an electrolyte additive, an electrolyte, and a battery, which can improve the cycle performance and rate performance of a secondary battery at high temperature by adding the electrolyte additive to the secondary battery.
The first aspect of the present application provides an electrolyte additive comprising a first additive, a second additive and a third additive, wherein the first additive comprises a silane-based additive containing an unsaturated bond, the second additive comprises a compound represented by formula 3, and the third additive comprises a compound represented by formula 4:
Wherein, R 11、R12、R13、R14、R15 and R 16 are each independently selected from any one of alkyl of H, C 1-C4 and alkenyl of C 2-C4;
n=0 or 1, a is selected from C or O, X is selected from o=s=o or c=o, R 17 and R 18 are each independently selected from H, 、AndR 17 and R 18 are not H at the same time, and at least one sulfur atom is contained in X, R 17 and R 18.
In the application, the first additive and the second additive can form a film on the positive electrode or the negative electrode of the battery in preference to solvent molecules, so as to protect the electrode: the first additive can not only form stable CEI at the positive electrode, but also generate copolymerization with the second additive, and form SEI with a reticular structure formed by staggered combination of silicon oxygen bonds and carbon oxygen silicon bonds on the surface of the negative electrode. However, both the first additive and the second additive contain double bonds, the formed CEI and SEI have larger impedance, and the multiplying power performance of the battery can be influenced, so that the third additive is introduced and can react with the double bonds of the first additive and the second additive, redundant double bonds in the CEI are consumed, the CEI film thickness of the positive electrode is reduced, and the thin CEI is favorable for reducing the internal resistance of the battery and improving the multiplying power performance of the battery. In conclusion, the electrolyte additive provided by the application has excellent cycle performance and rate performance at high temperature through the combined action of the three additives.
In some embodiments, the ratio of the mass of the first additive, the second additive, and the third additive is 1: (0.2-5): (0.2-5). Thus, the high temperature cycle performance and the rate performance of the battery can be improved.
In some embodiments, the first additive comprises at least one of the compounds represented by formulas 1 and 2:
Wherein, R 1、R2、R3、R4、R5 and R 6 are each independently selected from any one of C 1-C4 alkyl, C 2-C4 alkenyl and C 2-C4 alkynyl, and at least one of R 1、R2、R3、R4、R5 and R 6 is unsaturated alkyl;
r 7、R8、R9 and R 10 are each independently selected from any one of C 1-C4 alkyl, C 2-C4 alkenyl, C 2-C4 alkynyl and alkoxy, and at least one of R 7、R8、R9 and R 10 is an unsaturated hydrocarbon group. Thus, the high temperature cycle performance and the rate performance of the battery can be improved.
In some embodiments, the first additive comprises at least one of the following:
。
Thus, the high temperature cycle performance and the rate performance of the battery can be improved.
In some embodiments, the second additive comprises at least one of the following:
。
Thus, the high temperature cycle performance and the rate performance of the battery can be improved.
In some embodiments, the third additive comprises at least one of the following:
。
Thus, the high temperature cycle performance and the rate performance of the battery can be improved.
In a second aspect the application provides an electrolyte comprising the electrolyte additive of the first aspect. Thus, the electrolyte is added to the secondary battery, and the high-temperature cycle performance and rate performance of the battery can be improved.
In some embodiments, the first additive comprises 0.1% to 5% by mass based on the total mass of the electrolyte. Thus, the electrolyte is added to the secondary battery, and the high-temperature cycle performance and rate performance of the battery can be improved.
In some embodiments, the second additive comprises 0.1% to 5% by mass based on the total mass of the electrolyte. Thus, the electrolyte is added to the secondary battery, and the high-temperature cycle performance and rate performance of the battery can be improved.
In some embodiments, the third additive comprises 0.1% to 5% by mass based on the total mass of the electrolyte. Thus, the electrolyte is added to the secondary battery, and the high-temperature cycle performance and rate performance of the battery can be improved.
A third aspect of the application provides a battery comprising the electrolyte of the second aspect. Thus, the battery has excellent high-temperature cycle performance and rate performance.
In some embodiments, the battery includes a positive electrode sheet including a positive electrode active material including at least one of LiMn2O4、LiMnO2、Li2MnO4、Li1+aMn1-xMxO2 and Li 2Mn1-xO4, M is selected from at least one of Ni, co, mn, al, cr, mg, zr, mo, V, ti, B and F, 0.ltoreq.a < 0.2, 0.ltoreq.x <1; or alternatively
The positive electrode active material includes at least one of Nax1M1O2、Nax2M2[M3(CN)6]、NaFePO4、Na3V2(PO4)3、Na2M4P2O7、Na2Fe2(SO4)3 and Na 2M4(SO4)2·2H2 O, wherein: 0 < x1 is less than or equal to 1, M1 comprises at least one of Ni, co, mn, fe and Cu, 0 < x2 is less than 6, M2 comprises at least one of Ni, fe and Mn, M3 comprises at least one of Fe and Mn, and M4 comprises at least one of Fe, co, mn and Cu.
Additional aspects and advantages of the application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the application.
Detailed Description
The following detailed description of the embodiments of the application is intended to be illustrative of the application and is not to be taken as limiting the application.
The electrolyte additive is used in an amount of only a small part of the electrolyte in the secondary battery, but an appropriate amount of the additive is capable of forming SEI (Solid Electrolyte Interface, solid electrolyte interface film) on the surface of the negative active material and CEI (Cathode Electrolyte Interface, positive electrode-electrolyte interface film) on the surface of the positive active material. SEI and CEI are respectively formed on the surfaces of the anode active material and the cathode active material, so that the problem that side reactions occur after the active material is directly contacted with electrolyte is solved.
In a high-temperature environment, the cycle performance and the rate performance of the battery are easy to be obviously reduced, the oxidation activity of the positive electrode active material is improved, the stability is reduced, and the electrolyte can accelerate oxidative decomposition, such as oxidation reaction between the electrolyte and the positive electrode active material. Electrolyte is continuously oxidized on the surface of the positive electrode and deposited on the surface of the positive electrode, so that the internal resistance of the positive electrode is continuously increased, and the poor rate performance and the poor cycle stability of the battery are caused.
In view of this, the first aspect of the present application proposes an electrolyte additive comprising a first additive, a second additive and a third additive, wherein the first additive comprises a silane-based additive containing an unsaturated bond, the second additive comprises a compound represented by formula 3, and the third additive comprises a compound represented by formula 4:
Wherein, R 11、R12、R13、R14、R15 and R 16 are each independently selected from any one of alkyl of H, C 1-C4 and alkenyl of C 2-C4;
n=0 or 1, a is selected from C or O, X is selected from o=s=o or c=o, R 17 and R 18 are each independently selected from H, 、AndR 17 and R 18 are not H at the same time, and at least one sulfur atom is contained in X, R 17 and R 18.
In the application, under the high-temperature environment, the first additive and the second additive can form a film on the positive electrode or the negative electrode of the battery in preference to solvent molecules, so as to protect the electrode: the first additive can not only form stable CEI at the positive electrode, but also generate copolymerization with the second additive, and form SEI with a reticular structure formed by staggered combination of silicon oxygen bonds and carbon oxygen silicon bonds on the surface of the negative electrode. However, the first additive and the second additive both contain double bonds, the formed CEI and SEI have larger impedance, and the rate performance of the battery can be influenced, so that the third additive is introduced, can react with the double bonds of the first additive and the second additive, consumes redundant double bonds, and ensures that the CEI film thickness of the positive electrode is reduced, the thin CEI is favorable for reducing the internal resistance of the battery, and the rate performance of the battery is improved. In conclusion, the electrolyte additive provided by the application has excellent cycle performance and rate performance at high temperature through the combined action of the three additives.
It will be appreciated that when R 17 and R 18 are each independently selected from、AndIn any one of the above, the ring、AndThe connection position with the five-membered ring or six-membered ring shown in formula 4 may be any position.
In some embodiments, the ratio of the mass of the first additive, the second additive, and the third additive is 1: (0.2-5): (0.2-5). For example, the mass ratio of the three may be 1:0.2:0.2,1:0.2:1,1:0.2:5,1:1:1,1:5:1, and the like, thereby controlling the mass ratio of the first additive, the second additive and the third additive within the above range, fully playing the synergistic effect of the first additive, the second additive and the third additive, improving the cycle performance and the multiplying power performance of the battery at high temperature, improving the phenomenon of serious capacity loss of the battery, simultaneously being beneficial to reducing the positive electrode film impedance and the electrochemical impedance in the cycle process, being beneficial to reversibly embedding/extracting lithium ions in an electrode in the cycle process, and effectively improving the electrochemical performance of the battery.
In some embodiments, the first additive comprises at least one of the compounds represented by formulas 1 and 2:
Wherein, R 1、R2、R3、R4、R5 and R 6 are each independently selected from any one of C 1-C4 alkyl, C 2-C4 alkenyl and C 2-C4 alkynyl, and at least one of R 1、R2、R3、R4、R5 and R 6 is unsaturated alkyl;
r 7、R8、R9 and R 10 are each independently selected from any one of C 1-C4 alkyl, C 2-C4 alkenyl, C 2-C4 alkynyl and alkoxy, and at least one of R 7、R8、R9 and R 10 is an unsaturated hydrocarbon group. Thus, the high temperature cycle performance and the rate performance of the battery can be improved. The first additive and the second additive of the structural formula can form a film on the positive electrode or the negative electrode of the battery in preference to solvent molecules, and protect the electrode: the first additive can not only form stable CEI at the positive electrode, but also generate copolymerization with the second additive, and form SEI with a reticular structure formed by staggered combination of silicon oxygen bonds and carbon oxygen silicon bonds on the surface of the negative electrode. In addition, the first additive, the second additive and the third additive cooperate to provide the battery with excellent cycle performance and rate performance at high temperature.
It is to be understood that when R 1、R2、R3、R4、R5、R6、R7、R8、R9 and R 10 are each independently selected from the alkyl group of C 1-C4, the number of carbon atoms of the alkyl group is 1 to 4, for example, the number of carbon atoms may be 1, 2,3, 4, etc., and when R 1、R2、R3、R4、R5、R6、R7、R8、R9 and R 10 are each independently selected from the alkenyl group or the alkynyl group of C 2-C4, the number of carbon atoms of the alkenyl group or the alkynyl group is 2 to 4, for example, the number of carbon atoms may be 2,3, 4, etc.
In some embodiments of the application, the first additive comprises at least one of the following:
。
Specifically, the CAS number of formula 1-1 is 2627-95-4, the Chinese name is tetramethyl divinyl Disiloxane (DTMS), the CAS number of formula 1-2 is 55967-52-7, the CAS number of formula 1-3 is 1438-79-5, the CAS number of formula 2-1 is 78-08-0, the Chinese name is vinyltriethoxysilane, the CAS number of formula 2-2 is 18545-02-3, the Chinese name is triisobutoxyvinylsilane, the CAS number of formula 2-3 is 16546-47-7, the Chinese name is dimethylvinylmethoxysilane, the CAS number of formula 2-4 is 5507-44-8, the Chinese name is diethoxymethylvinylsilane, the CAS number of formula 2-5 is 5356-83-2, and the Chinese name is vinyldimethylethoxysilane.
The material is used as a first additive, the oxidation potential is lower than that of the electrolyte solvent, the material can be oxidized to form a film at the positive electrode in preference to solvent molecules, the positive electrode is protected, the cycle performance and the multiplying power performance of the battery are improved, in addition, the material can undergo oxidative polymerization reaction at the positive electrode during formation to form a compact surface film, the surface film has certain ion permeability, meanwhile, the electrolyte can be isolated from the positive electrode with strong oxidizing property, the side reaction of the solvent in the electrolyte and the positive electrode plate at high temperature is reduced, the capacity loss of the battery in the cycle process is reduced, and the cycle stability and the capacity retention rate are improved. Finally, the 3d empty orbit of the Si element hybridized with the Si-O bond of the substance can well accept electrons provided by HF, so that the substance can capture the HF in the electrolyte and prevent the HF from corroding the anode and the cathode in the circulating process, and the C=C bond in the substance can well form a compact passivation layer on the surface of the electrode through polymerization reaction. The material is used as a first additive, and after Li + is solvated, the material has smaller Li + bonding force and can be polymerized on the surface of a positive electrode better, so that the cycle performance and the rate performance of the secondary battery at high temperature are improved. However, the first additive alone does not solve the problem that the battery performance is reduced due to the fact that the negative electrode is susceptible to oxidation-reduction reaction with the electrolyte under high voltage. To solve this problem, a second additive is added, which can cooperate with the first additive to form a more stable and dense interfacial film at high voltage on the anode, thereby effectively protecting the anode.
In some embodiments of the application, the second additive comprises at least one of the following:
。
specifically, the CAS number of formula 3-1 is 4427-96-7, the Chinese name is ethylene carbonate (VEC), the CAS number of formula 3-2 is 952592-64-2, the CAS number of formula 3-3 is 790300-34-4, the CAS number of formula 3-4 is 952592-66-4, and the CAS number of formula 3-5 is 871235-96-0.
Specifically, under high temperature or high pressure conditions, the negative electrode is easy to generate serious reduction reaction to cause rapid increase of impedance, and easy to generate lithium precipitation phenomenon to cause short circuit of the battery, so that the safety is reduced, the formation of a stable interface film of the negative electrode is important, the second additive is a good negative electrode film forming additive, the LUMO energy of the substances is about-1.12V, the reduction potential is about 1.2V, electrochemical reduction reaction is generated on the surface of the negative electrode in preference to electrolyte in the formation process to form SEI, the co-intercalation and reduction decomposition of solvent molecules on the negative electrode are inhibited, the cycle performance and the high temperature performance of the battery are improved, but the SEI film formed by the second additive can generate stripping phenomenon at high temperature to influence the high temperature cycle performance of the battery. The first additive can form stable CEI at the positive electrode, can be copolymerized with a second additive composed of at least one of the substances, and the silicon oxygen group of the first additive can form a network group structure formed by staggered combination of silicon oxygen bonds and carbon oxygen silicon bonds on the surface of the negative electrode together with the second additive, namely after the second additive is added, the problem caused by reduction reaction of a conventional electrolyte which cannot be solved by independently using the first additive can be solved, and in addition, the first additive can also form an SEI film together with the second additive, so that the high-temperature stability of the SEI film is improved. However, the first additive and the second additive both contain a plurality of double bonds, so that the formed film has larger resistance, the SEI and CEI formed by the second additive are thicker, and the shuttling of active metal ions such as lithium ions is not favored due to the excessively thick interfacial film formed at the interface between the anode and the cathode, so that the cycle performance is degraded. To solve the problems associated with the combination of the first and second additives, a third additive is added.
In some embodiments of the application, the third additive comprises at least one of the following:
。
Specifically, the CAS of formula 4-1 is 2507955-35-1, the CAS of formula 4-2 is 2943046-27-1, the CAS of formula 4-3 is 2520352-94-5, the CAS of formula 4-4 is 2520352-90-1, and the CAS of formula 4-5 is 96633-53-3.
The first additive and the second additive have larger membrane resistance due to the plurality of double bonds, and the second additive participates in forming thicker SEI and CEI, and the interface membrane formed at the interface of the anode and the cathode is too thick, so that the shuttling of active metal ions such as lithium ions is not facilitated, and the cycle performance is degraded. The composition and thickness of SEI and CEI can be changed by adding a proper amount of third additive, so that the impedance of the pole piece is effectively reduced, and the improvement of the multiplying power performance and the cycle performance of the battery is realized. Specifically, the R-SO 2 -R groups contained in the substances can participate in film formation, and mainly can react with double bonds of the first additive and the second additive to consume redundant double bonds, SO that the SEI film thickness of the positive electrode and the SEI film thickness of the negative electrode are greatly reduced, and a thin CEI is beneficial to reducing the internal resistance of a battery and improving the rate performance of the battery. In addition, the third additive can be decomposed into a film at the positive electrode at high temperature or high pressure, so that the content of LiF is reduced, the interface lithium guiding performance is improved, and meanwhile, the decomposition of LiPF 6 and electrolyte on the surface of the positive electrode is inhibited. In summary, by simultaneously adding the first additive, the second additive, and the third additive containing the above substances to the electrolyte, the cycle performance and the rate performance of the secondary battery at high temperature can be improved.
In a second aspect the application provides an electrolyte comprising the electrolyte additive of the first aspect. Thus, the electrolyte is added to the secondary battery, and the high-temperature cycle performance and rate performance of the battery can be improved.
In some embodiments of the present application, the mass ratio of the first additive is 0.1% -5% based on the total mass of the electrolyte, that is, 0.1% -5% of the first additive is included in each gram of electrolyte, for example, 0.1%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5% or the like, so that when the electrolyte with the first additive content is added into the secondary battery, the first additive with the content undergoes oxidation polymerization reaction at the positive electrode to form a relatively compact surface film, and the cycle performance and the rate performance of the secondary battery at high temperature are improved; and is sufficient to co-act with the second additive and the third additive without affecting other battery properties due to excessive amounts of the first additive.
In some embodiments of the application, the second additive comprises 0.1% to 5% by mass based on the total mass of the electrolyte. Namely, each gram of electrolyte comprises 0.1% -5% of a second additive, for example, 0.1%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5% and the like, so that the electrolyte with the content of the second additive is added into a secondary battery, and in the formation process, the second additive is subjected to electrochemical reduction reaction on the surface of a negative electrode in preference to the electrolyte to form SEI (solid electrolyte interface), so that the cycle performance and the rate performance of the secondary battery at high temperature are improved; and is sufficient to co-act with the first additive and the third additive without affecting other battery properties due to excessive amounts of the second additive.
In some embodiments of the application, the third additive comprises 0.1% to 5% by mass based on the total mass of the electrolyte. Namely, each gram of electrolyte comprises 0.1% -5% of a third additive, for example, 0.1%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5% and the like, so that the electrolyte with the content of the third additive can react with double bonds in the first additive and the second additive to consume redundant double bonds, thereby effectively reducing the impedance of a pole piece and improving the multiplying power performance and the cycle performance; the amount is sufficient to co-act with the first additive and the second additive without causing excessive by-products during battery cycling due to excessive amounts of the third additive, thereby affecting the stability of the nonaqueous electrolyte.
When the first additive is applied in the electrolyte, CEI formed on the surface of the positive electrode is more suitable for a high-voltage environment, and is not easy to damage under high voltage, so that the capacity loss is reduced, and the cycle stability and the capacity retention rate are improved; when the second additive is applied in the electrolyte, SEI formed on the surface of the negative electrode is more suitable for a high-voltage environment, and the combination of the first additive and the second additive can improve the peeling phenomenon of SEI formed by the second additive at high temperature, so that the high-temperature cycling stability of the SEI is improved; the third additive can improve the phenomenon of large film resistance caused by the existence of double bonds in the structures of the first additive and the second additive, and can participate in forming low-impedance CEI and SEI with good stability simultaneously with the first additive and the second additive, thereby improving the cycle performance and the multiplying power performance of the battery.
In some embodiments of the present application, the electrolyte further includes a solvent, and the organic solvent is a solvent commonly used in electrolytes. Preferably, the organic solvent is at least one selected from carbonate compounds of C 3～C6, carboxylic acid ester compounds of C 3～C8, sulfone compounds and ether compounds. More preferably, the carbonate compound of C 3～C6 is at least one selected from ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, and ethyl propyl carbonate; the carboxylic ester compound of C 3～C8 is at least one selected from gamma-butyrolactone, methyl acetate, methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate, ethyl butyrate, propyl acetate and propyl propionate; the sulfone compound is selected from sulfolane; the ether compound is at least one selected from triglyme or tetraglyme; the content of the electrolyte is 50% -80%.
In some embodiments of the application, the electrolyte further comprises other additives, which may be selected as desired, such as, for example, vinylene Carbonate (VC), vinyl sulfate, fluoroethylene carbonate, 1, 3-propane sultone, 1, 3-propenesulfonic acid lactone, and the like.
In some embodiments of the application, the above-mentioned other additives are present in a mass ratio of 0.1% -5% based on the total mass of the electrolyte, i.e. 0.1% -5% of other additives are included per gram of electrolyte, and may specifically be selected from the range consisting of 0.1%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0% or any two thereof.
In some embodiments of the application, the electrolyte further comprises a lithium salt comprising at least one of lithium hexafluorophosphate, lithium bis (trifluoromethanesulfonyl) imide, lithium tetrafluoroborate, lithium bis (oxalato) borate, lithium difluorooxalato phosphate, lithium tetrafluorooxalato phosphate, lithium bis (trifluoromethanesulfonyl) imide.
In some embodiments of the application, the lithium salt may be present in a mass ratio of 12% to 18%, such as 12%,14%,15%,18%, etc., based on the total mass of the electrolyte.
A third aspect of the present application provides a battery. According to an embodiment of the application, the battery comprises the electrolyte according to the second aspect.
Thus, in a battery containing the electrolyte, by using the first additive, the second additive and the third additive simultaneously during battery formation and circulation, the first additive and the second additive can form a film on the positive electrode or the negative electrode of the battery in preference to solvent molecules, and the electrode is protected: the first additive can not only form stable CEI at the positive electrode, but also generate copolymerization with the second additive, and form SEI with a reticular structure formed by staggered combination of silicon oxygen bonds and carbon oxygen silicon bonds on the surface of the negative electrode. The sulfur-containing group of the third additive not only can react with the double bonds of the first additive and the second additive to consume redundant double bonds, but also participates in film formation together with the first additive and the second additive, and compared with the passivation film formed by the existing electrolyte, the formed SEI or CEI is thinner and more uniform, is a good lithium ion conductor, can effectively overcome the disadvantages of large CEI or SEI impedance and poor lithium ion conduction capability formed by a plurality of double bonds of the first additive and the second additive, and improves the rate performance of the battery. In conclusion, the electrolyte additive provided by the application has excellent cycle performance and rate performance at high temperature through the combined action of the three additives.
In some embodiments of the application, when the battery is a lithium ion battery, the battery comprises a positive electrode sheet comprising a positive electrode active material comprising at least one of LiMn2O4、LiMnO2、Li2MnO4、Li1+aMn1- xMxO2 and Li 2Mn1-xO4, M is selected from at least one of Ni, co, mn, al, cr, mg, zr, mo, V, ti, B and F, 0.ltoreq.a < 0.2, 0.ltoreq.x <1.
For example, the number of the cells to be processed, a is more than or equal to 0 and less than or equal to 0.19,0.05 a is more than or equal to 0.15,0.08 a is less than or equal to 0.15,0.08 of the type; x is more than or equal to 0 and less than or equal to 0.9, and 0.1 is more than or equal to 0 x is less than or equal to 0.8, x is less than or equal to 0.2 x is more than or equal to 0.7,0.3 and less than or equal to 0.6,0.4 x is more than or equal to 0.5, etc.
The positive electrode active material is a manganese-containing positive electrode active material, and the manganese-containing positive electrode active material has the outstanding advantages of high energy density caused by high voltage, wherein the working voltage of the lithium-rich manganese-based material can reach 4.8V, and the working voltage of the lithium iron manganese phosphate-based material can reach 3.6V, which is higher than 3.2V of the lithium iron phosphate-based material battery. However, the manganese dissolution in the manganese-containing positive electrode material causes the electrolyte system to face serious challenges in high-voltage and high-temperature environments, and the phenomena of short cycle life, poor charge and discharge capacity and the like appear.
The performance of the manganese-containing positive electrode battery is greatly dependent on the composition of an organic electrolyte and stable CEI and SEI formed by the reaction of the organic electrolyte on the surface of an electrode, and the electrolyte additive is used in the battery containing the manganese positive electrode active material, and the combined use of the first additive, the second additive and the third additive can not only improve the cycle performance and the multiplying power performance of the battery under high voltage and improve the phenomenon of serious capacity loss of the manganese-based positive electrode battery, but also be beneficial to reducing the positive electrode film impedance and the electrochemical charge transfer impedance of the material in the cycle process and being beneficial to reversibly embedding/extracting lithium ions in the electrode in the cycle process, thereby effectively improving the electrochemical performance of the manganese-containing positive electrode material.
In some embodiments of the present application, the positive electrode active material includes Li 1+aMn1-xMxO2, in the above lithium-rich manganese-based positive electrode material system, the layered lithium-rich manganese structure is easy to generate lattice oxygen escape to destroy the crystal structure under high voltage, so as to aggravate the dissolution of transition metal, and thus the phenomena of poor cycle performance, serious voltage decay, etc. are occurred, for the high voltage lithium-rich manganese system, it is crucial to form a stable and compact interface film, the common solvent system is easy to generate oxidative decomposition at the positive and negative electrodes under high voltage, while the additive of the present application can generate oxidation-reduction reaction preferentially at the positive and negative electrodes to form the interface film, prevent the electrolyte from reacting with the positive and negative electrodes, prevent the damage of the positive and negative electrodes and the decomposition of the electrolyte, and improve the cycle performance and the rate performance of the secondary battery under high temperature.
In some embodiments of the present application, when the battery is a sodium ion battery, the positive electrode active material may include at least one of the following materials:
Na xMO2, wherein M comprises at least one of Ti, V, mn, co, ni, fe, zn, V, zr, ce, cr, cu, 0< x.ltoreq.1.
Polyanionic compounds: at least one of NaFePO 4、Na3V2(PO4)3 (sodium vanadium phosphate, NVP for short), na 4Fe3(PO4)2(P2O7)、NaM'PO4 F (M' comprises at least one of V, fe, mn and Ni) and Na 3(VOy)2(PO4)2F3-2y (y is more than or equal to 0 and less than or equal to 1).
Prussian blue compounds: na aMebMe'c(CN)6, wherein Me and Me' each independently comprise at least one of Ni, cu, fe, mn, co, zn, 0 < a.ltoreq.2, 0 < b < 1,0 < c < 1.
In some embodiments of the application, the battery includes a positive electrode active material including at least one of NaX1M1O2、NaX2M2[M3(CN)6]、NaFePO4、Na3V2(PO4)3、Na2M4P2O7、Na2Fe2(SO4)3、Na2M4(SO4)2·2H2O, wherein 0< x1 is less than or equal to 1, M1 includes at least one of Ni, co, mn, fe and Cu, 0< x2 is less than 6, M2 includes at least one of Ni, fe and Mn, M3 includes at least one of Fe and Mn, and M4 includes at least one of Fe, co, mn and Cu. The positive electrode active material can better generate stable SEI by being matched with the electrolyte additive provided by the embodiment of the application, so that the battery has excellent cycle performance and rate performance at high temperature.
Typically, a battery includes a positive electrode tab, a negative electrode tab, an electrolyte, and a separator. During the charge and discharge of the battery, active ions are inserted and extracted back and forth between the positive electrode plate and the negative electrode plate. The electrolyte plays a role in ion conduction between the positive electrode plate and the negative electrode plate. The isolating film is arranged between the positive pole piece and the negative pole piece, and mainly plays a role in preventing the positive pole piece and the negative pole piece from being short-circuited, and meanwhile ions can pass through the isolating film.
The positive electrode plate comprises a positive electrode current collector and a positive electrode active material layer arranged on at least one side surface of the positive electrode current collector, and the positive electrode active material layer comprises the positive electrode active material.
In some embodiments of the application, the positive electrode current collector may include a metal foil or a composite positive electrode current collector. For example, aluminum foil may be used as the metal foil. The composite positive electrode current collector may include a polymer material base layer and a metal layer formed on at least one side surface of the polymer material base layer, for example, the composite positive electrode current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel alloy, etc.) on a polymer material base material such as a polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), etc. base material.
In some embodiments of the present application, the positive electrode active material layer may further optionally include a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
In some embodiments of the present application, the positive electrode active material layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluoroacrylate resin.
In some embodiments of the present application, the positive electrode sheet may be prepared by: dispersing the components for preparing the positive electrode plate, such as the positive electrode active material, the conductive agent and the binder, in a solvent (such as N-methyl pyrrolidone) to form positive electrode slurry; and (3) coating the positive electrode slurry on a positive electrode current collector, and obtaining a positive electrode plate after the procedures of drying, cold pressing and the like.
The negative electrode tab includes a negative electrode current collector and a negative electrode active material layer disposed on at least one side surface of the negative electrode current collector, the negative electrode active material layer including a negative electrode active material.
In some embodiments of the application, the negative electrode current collector may employ a metal foil or a composite current collector. For example, as the metal foil, copper foil may be used. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base material. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel alloy, etc.) on a polymer material substrate such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), etc.
In some embodiments of the present application, the anode active material may employ an anode active material for a battery, which is well known in the art. As an example, the anode active material may include at least one of the following materials: at least one of natural graphite, artificial graphite, soft carbon, hard carbon, mesophase carbon microspheres, nano carbon, simple substance silicon, silicon oxygen compound, silicon carbon compound, silicon alloy, simple substance tin, tin oxygen compound, tin carbon compound, tin alloy and lithium titanate.
In some embodiments of the application, the anode active material layer further optionally includes a binder. The binder may include at least one of Styrene Butadiene Rubber (SBR), polyacrylic acid (PAA), sodium Polyacrylate (PAAs), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium Alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).
In some embodiments of the present application, the anode active material layer may further optionally include a conductive agent. The conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
In some embodiments of the present application, the anode active material layer may optionally further include other auxiliary agents, such as a thickener (e.g., sodium carboxymethyl cellulose (CMC-Na)), and the like.
In some embodiments of the application, the negative electrode sheet may be prepared by: dispersing the above components for preparing the negative electrode sheet, such as a negative electrode active material, a conductive agent, a binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; and coating the negative electrode slurry on a negative electrode current collector, and obtaining a negative electrode plate after the procedures of drying, cold pressing and the like.
The type of the separator is not particularly limited, and any known porous separator having good chemical stability and mechanical stability can be used.
In some embodiments of the present application, the material of the isolation film may include at least one of glass fiber, non-woven fabric, polyolefin film, aromatic polyamide film, polytetrafluoroethylene film, and polyethersulfone film.
In some embodiments of the application, the thickness of the separator may be 10 μm to 12 μm, for example, 10 μm,11 μm,12 μm, etc.
It should be noted that the features and advantages described above for the electrolyte are equally applicable to the battery, and are not repeated here.
The following detailed description of embodiments of the invention is provided for the purpose of illustration only and is not to be construed as limiting the invention. In addition, all reagents employed in the examples below are commercially available or may be synthesized according to methods herein or known, and are readily available to those skilled in the art for reaction conditions not listed, if not explicitly stated.
Example 1
1. Preparation of positive electrode plate
Dispersing a positive electrode active material Li 1.2Ni0.13Co0.13Mn0.54O2, a conductive agent carbon black, a conductive agent carbon nano tube and a binder polyvinylidene fluoride in a solvent N-methyl pyrrolidone according to a mass ratio of 94.5:3.5:0.5:1.5 to obtain a positive electrode active material layer slurry; and uniformly coating the slurry of the positive electrode active material layer on the surface of an aluminum foil of a positive electrode current collector, and drying, rolling, baking, slitting and spot welding the tab to obtain a positive electrode plate, wherein the total thickness of the positive electrode plate is 90 mu m.
2. Preparation of negative electrode plate
Dispersing negative electrode active material graphite (purchased from Jiangxi purple), conductive agent carbon black, binder polyvinylidene fluoride and sodium carboxymethylcellulose in deionized water according to a mass ratio of 94.5:2:2:1.5, and uniformly stirring to obtain negative electrode active material layer slurry; and uniformly coating the slurry of the anode active material layer on the surface of the anode current collector copper foil, and drying, rolling, baking, slitting and spot-welding the electrode lugs to obtain an anode electrode plate, wherein the total thickness of the anode electrode plate is 128 mu m.
3. Preparation of electrolyte
In a high-purity argon glove box with the oxygen content and the water content not higher than 0.1ppm, ethylene Carbonate (EC), diethyl carbonate (DEC) and ethylmethyl carbonate (EMC) are mixed according to the mass ratio of EC: DEC: EMC=3:2:5, and then lithium hexafluorophosphate (LiPF 6) (10%) and lithium difluorosulfimide (LiSSI) (6%) with the total mass fraction of 16% are slowly added into the mixed solution. And mixing EC, DEC and EMC according to a mass ratio of 3:2:5, adding lithium salt, a first additive, a second additive, a third additive and other additives according to the molar concentration and mass fraction of each component after mixing, and uniformly mixing to obtain the electrolyte. The mass ratio of the first additive, the second additive, the third additive, and other additives based on the total mass of the electrolyte is shown with reference to table 1, and the other additives include PS (1, 3-propane sultone) accounting for 2% of the total mass of the electrolyte, PST (1, 3-propenesulfonlactone) accounting for 0.3% of the total mass of the electrolyte, and FEC (fluoroethylene carbonate) accounting for 5% of the total mass of the electrolyte.
4. Isolation film
A10 μm polyethylene film was used as a separator.
5. Secondary battery preparation
And stacking the positive electrode plate, the isolating film and the negative electrode plate in sequence, enabling the isolating film to be positioned between the positive electrode plate and the negative electrode plate to play a role in isolating the positive electrode from the negative electrode plate, winding to obtain a bare cell, welding the electrode lug, placing the bare cell in an outer package, injecting the prepared electrolyte into the dried cell, packaging, standing, forming, shaping and the like, and thus completing the preparation of the secondary battery.
It will be appreciated that, in the electrolyte, when the total amount of the additives (including the first additive, the second additive, the third additive and other additives in the embodiment of the present application) is changed, the content of the solvent is correspondingly changed, for example, the total amount of the additives is increased by 1%, the content of the corresponding solvent is reduced by 1%, but the ratio of EC, DEC, EMC to the solvent is still 3:2:5.
The secondary batteries of examples 2 to 26 and comparative examples 1 to 7 were produced in the same manner as in example 1, except that the additive composition in the electrolyte was different, as shown in table 1.
TABLE 1
Example 27
1. Preparation of positive electrode plate
Dispersing an anode active material Na [ Ni 0.33Fe0.33Mn0.33]O2, a conductive agent carbon black, a conductive agent carbon nano tube and a binder polyvinylidene fluoride in a mass ratio of 94.5:3.5:0.5:1.5 into a solvent N-methylpyrrolidone to obtain anode active material layer slurry; and uniformly coating the slurry of the positive electrode active material layer on the surface of an aluminum foil of a positive electrode current collector, and drying, rolling, baking, slitting and spot welding the tab to obtain a positive electrode plate, wherein the total thickness of the positive electrode plate is 90 mu m.
2. Preparation of negative electrode plate
Dispersing negative electrode active material graphite (purchased from Jiangxi purple), conductive agent carbon black, binder polyvinylidene fluoride and sodium carboxymethylcellulose in deionized water according to a mass ratio of 94.5:2:2:1.5, and uniformly stirring to obtain negative electrode active material layer slurry; and uniformly coating the slurry of the anode active material layer on the surface of the anode current collector copper foil, and drying, rolling, baking, slitting and spot-welding the electrode lugs to obtain an anode electrode plate, wherein the total thickness of the anode electrode plate is 128 mu m.
3. Preparation of electrolyte
In a high-purity argon glove box with the oxygen content and the water content not higher than 0.1ppm, ethylene Carbonate (EC), diethyl carbonate (DEC) and ethylmethyl carbonate (EMC) are mixed according to the mass ratio of EC: DEC: EMC=3:2:5, and then sodium hexafluorophosphate (NaPF 6) (10%) and sodium difluorosulfimide (NaFSI) (6%) with the total mass fraction of 16% are slowly added into the mixed solution. And mixing EC, DEC and EMC according to a mass ratio of 3:2:5, adding sodium salt, a first additive, a second additive, a third additive and other additives according to the molar concentration and mass fraction of each component after mixing, and uniformly mixing to obtain the electrolyte. The mass ratio of the first additive, the second additive, the third additive, and other additives based on the total mass of the electrolyte is shown with reference to table 1, and the other additives include PS (1, 3-propane sultone) accounting for 2% of the total mass of the electrolyte, PST (1, 3-propenesulfonlactone) accounting for 0.3% of the total mass of the electrolyte, and FEC (fluoroethylene carbonate) accounting for 5% of the total mass of the electrolyte.
4. Isolation film
A10 μm polyethylene film was used as a separator.
5. Secondary battery preparation
And stacking the positive electrode plate, the isolating film and the negative electrode plate in sequence, enabling the isolating film to be positioned between the positive electrode plate and the negative electrode plate to play a role in isolating the positive electrode from the negative electrode plate, winding to obtain a bare cell, welding the electrode lug, placing the bare cell in an outer package, injecting the prepared electrolyte into the dried cell, packaging, standing, forming, shaping and the like, and thus completing the preparation of the secondary battery.
The secondary batteries of examples 28 to 33 were produced in the same manner as in example 27 except that the additive composition in the electrolyte was different, as shown in Table 2.
TABLE 2
The secondary batteries obtained in examples 1 to 26 and comparative examples 1 to 7 were characterized for high-temperature cycle performance, rate performance and direct current internal resistance, and the characterization results are shown in table 3.
1. The cells were cycled 400 times at 25 ℃ for capacity retention testing:
at an ambient temperature of 25 ℃, 400 charge-discharge cycle tests are carried out on the lithium battery at a current of 1.0C, a test voltage window is 2.75V-4.6V, the discharge capacity of the 1 st cycle is recorded as C1, the discharge capacity of the 400 th cycle is recorded as C400, and the capacity retention rate eta 1=C400/C1×100% of the 400 th cycle at 45 ℃ is recorded as shown in table 3.
2. The battery was cycled 400 times at 45 ℃ for capacity retention testing:
At the ambient temperature of 45 ℃, the secondary battery is kept stand for 4h, then 400 charge-discharge cycle tests are carried out on the lithium battery under the current of 1.0C, the test voltage window is 2.75V-4.6V, the discharge capacity of the 1 st cycle is recorded as C1, the discharge capacity of the 400 th cycle is recorded as C400, and the capacity retention rate eta 2=C400/C1×100% of the 45 ℃ cycle for 400 weeks is recorded as shown in table 3.
3. The discharge capacities of 2c,3c,5c were tested at 25 ℃ respectively:
The battery was pre-cycled between 2.0V and 4.6V, charged and discharged 3 times at a rate of 0.1C, then charged and discharged 3 times at a rate of 0.2C, and after 0.2C cycling, charged and discharged 5 times with 2C,3C,5C, respectively, and the discharge capacities at each rate were recorded, C1, C2, C3, C4, C5, and the average value thereof was calculated.
C release= (C1+C2+C 3+ C4+ C5)/5, see table 3.
4. Secondary battery Direct Current Resistance (DCR) test:
DCR test before storage: charging the battery to 4.6V at a constant current of 1.0C and a constant voltage of 4.6V to a cut-off current of 0.05C at an ambient temperature of 25 ℃, then placing the battery on shelf for 30 min, then discharging 30 min (adjusted to 50% soc) at 1.0C, recording an end voltage V1, placing 1 on shelf for h, then discharging 10 s at 2.0C, recording an end voltage V2, dcr1= (V1-V2)/(2.0C-1.0C) before storage; 60. DCR test after 7 days of storage at c: charging the stored battery to 4.6V at a constant current of 1.0C and a constant voltage of 4.6V to an off current of 0.05C at an ambient temperature of 25 ℃, then resting the battery at 30 min, then discharging 30 min (adjusted to 50% soc) at 1.0C, recording an end voltage V3, resting at 1h, then discharging 10 s at 2.0C, recording an end voltage V4, dcr2= (V3-V4)/(2.0C-1.0C) before storage; the rate of increase η4= (DCR 2-DCR 1)/dcr1×100% of DCR, the results are shown in table 3.
TABLE 3 Table 3
As can be seen from Table 3, the capacity retention rate at 25℃and 400℃for examples 1 to 26 were both 80% or more, the 2C discharge capacity and the 3C discharge capacity were both 200mAh/g or more, the 5C discharge capacity was 175mAh/g or more, and the DCR growth rate was 11% or less, and compared with examples 1 to 26, the cycle performance and rate performance of the battery were significantly lower than those of examples 1 to 26, in which the first additive, the second additive and the third additive were not simultaneously added to comparative examples 1 to 7, and it was found that the electrolyte additive of the present application contained the first additive, the second additive and the third additive at the same time, and the cycle performance and rate performance of the battery at high temperature were excellent by the combined action of the three additives.
The secondary batteries obtained in examples 27 to 33 were characterized in terms of high-temperature cycle performance, rate performance and direct current internal resistance, and the characterization results are shown in table 4.
1. The cell was cycled 400 times at 25 ℃ and 45 ℃ for capacity retention testing:
and respectively placing the sodium ion batteries with the 2 upper clamping plates subjected to capacity division in a preset temperature environment, respectively charging the sodium ion batteries to an upper limit cutoff voltage by using constant current and constant voltage of 1C and 2C, wherein the cutoff current is 0.05C, then discharging the sodium ion batteries to a lower limit cutoff voltage by using constant current of 1C/1C, and recording the discharge capacity of the first circle and the discharge capacity of the last circle of the 2 batteries respectively in a circulation way, and calculating the capacity retention rate according to the following formula. Capacity retention = discharge capacity of last round/discharge capacity of first round x 100%. The capacity retention rates after 400 weeks of the sodium ion battery at normal temperature (25 ℃) and the high temperature (45 ℃) of the sodium ion battery at 1C and 1C were respectively tested under the charging and discharging conditions.
2. The discharge capacities of 2c,3c,5c were tested at 25 ℃ respectively:
The battery was pre-cycled between 1.5V-4.2V, charged and discharged 3 times at a rate of 0.1C, then charged and discharged 3 times at a rate of 0.2C, and after 0.2C cycling, charged and discharged 5 times with 2C,3C,5C, respectively, and the discharge capacities at each rate were recorded, C1, C2, C3, C4, C5, and the average value thereof was calculated.
C release= (C1+C2+C 3+ C4+ C5)/5, see table 4.
4. Secondary battery Direct Current Resistance (DCR) test:
DCR test before storage: charging the battery to 4.2V at a constant current of 1.0C and a constant voltage of 4.2V to a cut-off current of 0.05C at an ambient temperature of 25 ℃, then placing the battery on shelf of 30min, then discharging 30min (adjusted to 50% soc) at 1.0C, recording an end voltage V1, placing 1 on shelf of h, then discharging 10 s at 2.0C, recording an end voltage V2, dcr1= (V1-V2)/(2.0C-1.0C) before storage; 60. DCR test after 7 days of storage at c: charging the stored battery to 4.2V at a constant current of 1.0C and a constant voltage of 4.2V to a cut-off current of 0.05C at an ambient temperature of 25 ℃, then placing the battery at rest for 30min, then discharging 30min (adjusted to 50% soc) at 1.0C, recording an end voltage V3, placing 1 h, then discharging 10 s at 2.0C, recording an end voltage V4, dcr2= (V3-V4)/(2.0C-1.0C) before storage; the rate of increase η4= (DCR 2-DCR 1)/dcr1×100% of DCR and the results are shown in table 4.
TABLE 4 Table 4
As can be seen from table 4, in examples 27 to 33 of the present application, the sodium ion battery electrolyte additive contains the first additive, the second additive and the third additive at the same time, and the cycle performance and the rate performance of the battery at high temperature are excellent by the combined action of the three additives. Therefore, the electrolyte additive disclosed by the embodiment of the application is also suitable for sodium ion batteries, and can improve the cycle performance and the multiplying power performance of the sodium ion batteries at high temperature.
In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present application. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction.
While embodiments of the present application have been shown and described above, it will be understood that the above embodiments are illustrative and not to be construed as limiting the application, and that variations, modifications, alternatives and variations may be made to the above embodiments by one of ordinary skill in the art within the scope of the application.

Claims (4)

1. A battery, characterized by comprising an electrolyte and a positive electrode sheet, wherein the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer at least positioned on one side of the positive electrode current collector, the positive electrode active material layer comprises a positive electrode active material, and the positive electrode active material comprises a manganese-containing positive electrode active material; the electrolyte comprises an electrolyte additive comprising a first additive, a second additive and a third additive, wherein the first additive comprises a silane-based additive containing an unsaturated bond, the second additive comprises a compound shown in formula 3, and the third additive comprises a compound shown in formula 4:
Wherein, R 11、R12、R13、R14、R15 and R 16 are each independently selected from any one of alkyl of H, C 1-C4 and alkenyl of C 2-C4;
n=0 or 1, a is selected from C or O, X is selected from o=s=o or c=o, R 17 and R 18 are each independently selected from H, 、AndR 17 and R 18 are not H at the same time, and at least one sulfur atom is contained in X, R 17 and R 18;
The mass ratio of the first additive to the second additive to the third additive is 1: (0.2-5): (0.2-5);
the first additive comprises at least one of the following:
；
the second additive comprises at least one of the following:
；
the third additive comprises at least one of the following:
。
2. The battery of claim 1, wherein the first additive comprises at least one of the compounds represented by formulas 1 and 2:
Wherein, R 1、R2、R3、R4、R5 and R 6 are each independently selected from any one of C 1-C4 alkyl, C 2-C4 alkenyl and C 2-C4 alkynyl, and at least one of R 1、R2、R3、R4、R5 and R 6 is unsaturated alkyl;
r 7、R8、R9 and R 10 are each independently selected from any one of C 1-C4 alkyl, C 2-C4 alkenyl, C 2-C4 alkynyl and alkoxy, and at least one of R 7、R8、R9 and R 10 is an unsaturated hydrocarbon group.
3. The battery according to claim 1 or 2, wherein the mass ratio of the first additive is 0.1% to 5% based on the total mass of the electrolyte; and/or the number of the groups of groups,
The mass ratio of the second additive is 0.1% -5%; and/or the number of the groups of groups,
The mass ratio of the third additive is 0.1% -5%.
4. The battery according to claim 1 or 2, wherein the battery comprises a positive electrode sheet comprising a positive electrode active material comprising at least one of LiMn2O4、LiMnO2、Li2MnO4、Li1+aMn1-xMxO2 and Li 2Mn1-xO4, M being selected from at least one of Ni, co, mn, al, cr, mg, zr, mo, V, ti, B and F, 0.ltoreq.a < 0.2, 0.ltoreq.x <1; or alternatively
The positive electrode active material includes at least one of Nax1M1O2、Nax2M2[M3(CN)6]、NaFePO4、Na3V2(PO4)3、Na2M4P2O7、Na2Fe2(SO4)3 and Na 2M4(SO4)2·2H2 O, wherein: 0 < x1 is less than or equal to 1, M1 comprises at least one of Ni, co, mn, fe and Cu, 0 < x2 is less than 6, M2 comprises at least one of Ni, fe and Mn, M3 comprises at least one of Fe and Mn, and M4 comprises at least one of Fe, co, mn and Cu.
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