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CN-122000455-A - Sodium ion battery electrolyte and sodium ion battery

CN122000455ACN 122000455 ACN122000455 ACN 122000455ACN-122000455-A

Abstract

The invention relates to a high-stability sodium ion battery electrolyte and a sodium ion full battery using the same. The additive comprises a negative electrode side additive and a positive electrode side additive, wherein the negative electrode side additive and the positive electrode side additive form a composite additive, the positive electrode side additive can effectively inhibit the oxidative decomposition of electrolyte on the surface of a high-voltage positive electrode at the positive electrode side, and the negative electrode side additive in the composite additive can effectively inhibit the reductive decomposition of the positive electrode side additive and a solvent on the low-potential negative electrode side at the negative electrode side. The negative electrode side additive is a special structure additive, and the cyclic structure of the negative electrode side additive contains-SO 3 and C=C functional groups. The positive electrode side additive is a special structure additive, and the structure of the positive electrode side additive comprises at least 2-C.ident.N functional groups. After the electrolyte containing the composite additive is applied to the sodium ion full battery, the irreversible capacity loss of the battery can be obviously reduced, and the cycle life of the battery can be obviously prolonged.

Inventors

  • ZHENG QIONG
  • JIANG MINGQIN
  • QIU YANLING
  • LI XIANFENG

Assignees

  • 中国科学院大连化学物理研究所

Dates

Publication Date
20260508
Application Date
20241104

Claims (10)

  1. 1. The sodium ion battery electrolyte comprises an organic solvent, sodium salt and an additive, and is characterized in that the additive is a composite additive and comprises a negative electrode side functional additive and a positive electrode side functional additive; the negative electrode side functional additive comprises one or more than two of structural compounds shown in a formula 1a or a formula 1 b; R in formula 1a is C 1-10 straight-chain alkyl (preferably C 1-6 straight-chain alkyl, more preferably C 1-4 straight-chain alkyl), and two R 1 in formula 1b are each independently C 1-10 alkyl (preferably C 1-6 alkyl, more preferably C 1-4 alkyl); the positive electrode side functional additive comprises one or more than two of structural compounds shown in a formula 2; R 2 in formula 2 is C 1-10 alkyl (preferably C 1-6 alkyl, more preferably C 1-4 alkyl).
  2. 2. The sodium ion battery electrolyte of claim 1, wherein: The organic solvent comprises one or more than two of cyclic carbonate, chain carbonate and dimethyl ether; the cyclic carbonate is selected from one or two of ethylene carbonate and propylene carbonate; the chain carbonic ester is selected from one or more than two of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, dipropyl carbonate and methyl propyl carbonate; the dimethyl ether is selected from one or more of dimethyl ether, diethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether.
  3. 3. The sodium ion battery electrolyte according to claim 1 or 2, characterized in that: The sodium salt is one or more than two of sodium hexafluorophosphate, sodium perchlorate, sodium trifluoromethanesulfonate, sodium bistrifluoromethane sulfonyl imide and sodium bistrifluorosulfonyl imide, and the concentration of the sodium salt in the electrolyte is 0.2-3mol L -1 , preferably 0.5-1.5mol L -1 , more preferably 0.8-1.0mol L -1 .
  4. 4. The sodium ion battery electrolyte of claim 1, wherein: The final mass percentage of the negative side functional additive in the electrolyte is 0.5-10%, preferably 1-5%, more preferably 2-3%.
  5. 5. The electrolyte for sodium ion battery according to claim 1, wherein the final mass percentage of the positive electrode side functional additive in the electrolyte is 0.5-10%, preferably 1-5%, more preferably 2-3%.
  6. 6. A sodium ion battery is characterized in that the electrolyte adopted is the electrolyte according to any one of claims 1 to 5.
  7. 7. The battery of claim 6, wherein the positive electrode active material of the sodium ion battery is a polyanion type compound, and the positive electrode active material comprises Na 3 V 2 (PO 4 ) 2 F 3 、Na 3 V 2 (PO 4 ) 2 O 2 F、Na 3 V 2 (PO 4 ) 3 、Na 4 VMn(PO 4 ) 3 、Na 4 FeMn(PO 4 ) 3 、Na 3 TiMn(PO 4 ) 3 、Na 4 MnCr(PO 4 ) 3 、Na 3 Fe 2 (SO 4 ) 3 、NaFePO 4 、Na 2 FeP 2 O 7 、Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 、Na 4 Fe x Mn y (PO 4 ) 2 P 2 O 7 、Na 3 NiZr(PO 4 ) 3 、Na 2 FePO 4 F、Na 2 FeSiO 4 、 and manganese-rich composite phosphate positive electrode Na 4 M 3 (PO 4 ) 2 P 2 O 7 (M is a combination of more than or equal to 3 high-abundance elements, the high-abundance elements can be a combination of two or more of Mn, fe, cr, V and the like, wherein M is mainly Mn, the molar ratio of Mn in the high-abundance elements is x, and 50 percent less than or equal to x <100 percent, and the total molar ratio of other elements is 3-x).
  8. 8. The battery of claim 7, wherein the negative electrode material of the sodium ion battery is a carbon-based material comprising one or two of hard carbon and soft carbon, and the separator is one or two of a glass fiber film and a celgard film, preferably a celgard film.
  9. 9. The battery according to claim 6,7 or 8, wherein the polyanion positive electrode and the negative electrode of the sodium ion battery are sequentially arranged in the electrolyte through a separator, and the electrolyte according to any one of claims 1 to 5 is used as a sodium ion full battery electrolyte.
  10. 10. The battery according to claim 9, wherein the full battery voltage ranges from 2 to 4.5V, preferably from 2 to 4.3V, and the positive electrode potential is equal to or higher than 4.5V vs. Na/Na + , and the negative electrode potential is equal to or lower than 0.1V vs. Na/Na + , respectively, and both the positive electrode and the negative electrode can be stably operated at the potentials, so that the full battery can be stably operated within the selected voltage range of the full battery.

Description

Sodium ion battery electrolyte and sodium ion battery Technical Field The invention relates to the field of batteries, and discloses sodium ion battery electrolyte and a sodium ion battery. Background The sodium ion battery has the advantages of rich sodium resources, low cost, high cost performance and the like, and has wide application prospect in medium-low speed electric vehicles and large-scale energy storage, but is limited by lower energy density and power density. Therefore, it is necessary to design a positive electrode material with high operating voltage and high energy density and a negative electrode material with low operating voltage and high energy density. However, the electrolyte is extremely susceptible to oxidative decomposition on the surface of a high-voltage positive electrode (> 4.0v vs. Na/Na +) and reductive decomposition on the surface of a low-operating-voltage negative electrode (< 1.0v vs. Na/Na +), and the oxidative/reductive decomposition consumes active Na + to cause rapid attenuation of the full battery capacity, so that the full battery has low energy density and poor cycle life. Disclosure of Invention In order to solve the problems, the research shows that the high-pressure-resistant sodium ion battery electrolyte is designed by introducing a special structural function additive as a positive electrode side function additive and matching with a negative electrode side function additive. The carbon chain end of the positive electrode side functional additive contains at least one-C (identical to) N functional group, under the premise that one-C (identical to) N functional group participates in a sodium ion solvation structure (the modified solvation structure reduces coordination number of a solvent and Na +, under the drive of voltage in a charge-discharge process, components in an electrolyte shuttle between positive and negative electrode surfaces in a Na + solvation structure form of an additive-Na + -solvent-anion, the reduction of the coordination number of the solvent reduces the frequency and probability of the electrolyte on the positive electrode surface of high voltage (> 4.0V vs. Na/Na +), so that the oxidative decomposition of the electrolyte solvent on the positive electrode surface of high voltage is weakened, and the other electrolyte solvent preferentially adsorbs and contacts with the positive electrode of high voltage on the positive electrode surface, and then preferential oxidative decomposition occurs, so that stable CEI rich in nitride is constructed, and the oxidative decomposition of the electrolyte on the positive electrode surface of high voltage can be effectively inhibited. However, in the early study of the invention, the electrolyte solution scheme only comprising the positive electrode side functional additive is introduced into a full battery with a positive electrode of Na 3V2(PO4)2F3 and a negative electrode of hard carbon, and the reversible cycle capacity and the cycle life of the full battery are greatly reduced, because the positive electrode side functional additive undergoes a severe reduction reaction at the negative electrode side, and the reversible cycle capacity and the cycle life of the battery are greatly reduced due to the consumption of bulk phase Na +. Therefore, the invention further researches and provides one or more negative side functional additives, and further discloses a full-battery-adaptive high-stability sodium ion battery electrolyte and a sodium ion full battery. Specifically, the sodium ion battery electrolyte comprises an organic solvent, sodium salt and an additive, wherein the additive is a composite additive and comprises a negative electrode side functional additive and a positive electrode side functional additive; the negative electrode side functional additive includes one or more of structural compounds represented by formula 1a or formula 1b, preferably structural compound (propenyl-1, 3-sultone (PES)) represented by formula 1 c; R in formula 1a is C 1-10 straight-chain alkyl (preferably C 1-6 straight-chain alkyl, more preferably C 1-4 straight-chain alkyl), and two R 1 in formula 1b are each independently C 1-10 alkyl (preferably C 1-6 alkyl, more preferably C 1-4 alkyl); The positive electrode side functional additive includes one or more of the structural compounds shown in formula 2, preferably a structural compound shown in formula 2a (succinonitrile (SN)); R 2 in formula 2 is C 1-10 alkyl (preferably C 1-6 alkyl, more preferably C 1-4 alkyl). The invention discovers that after the additive is applied, the reversible cycle capacity of the battery is obviously improved, and the cycle life is obviously prolonged. Preferably, the final mass percentage of the positive electrode side functional additive in the electrolyte is 0.5 to 10%, preferably 1 to 5%, more preferably 2 to 3%. Preferably, the negative-side functional additive is present in the electrolyte in an amount of 0.5 to 10%, preferably