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CN-115347234-B - Lithium battery electrolyte containing nitrate ions

CN115347234BCN 115347234 BCN115347234 BCN 115347234BCN-115347234-B

Abstract

The invention provides a lithium battery electrolyte containing nitrate ions, which comprises an organic solvent, an electrolyte and an additive, wherein the organic solvent is organic carbonate, the electrolyte is lithium salt, the concentration of the electrolyte is 0.5-5 mol/L based on the volume of the organic solvent, the additive is an ionic liquid, the cation of the ionic liquid is one or more of pyrrolidine cations, pyridine cations, imidazole cations and quaternary ammonium salt cations, the anion of the ionic liquid is nitrate anions, and the mass content of the ionic liquid in the lithium battery electrolyte is 0.5-5%. The anions of the ionic liquid can then be reduced and decomposed in preference to lithium salts to form a stable, highly conductive solid electrolyte layer (SEI) rich in LiN 3 、LiN x O y and lithium oxide.

Inventors

  • YAN FENG
  • MA XINYU
  • YU JIANGTAO

Assignees

  • 苏州大学

Dates

Publication Date
20260505
Application Date
20220906

Claims (7)

  1. 1. The lithium battery electrolyte containing nitrate ions comprises an organic solvent, electrolyte and an additive, wherein the organic solvent is organic carbonate, the electrolyte is lithium salt, and the concentration of the electrolyte is 0.5-5 mol/L based on the volume of the organic solvent, and the lithium battery electrolyte is characterized in that the additive is an ionic liquid, the cation of the ionic liquid is one or more of pyrrolidine cations, pyridine cations, imidazole cations and quaternary ammonium salt cations, the anion of the ionic liquid is nitrate anions, and the mass content of the ionic liquid in the lithium battery electrolyte is 0.5-5%; when the voltage is more than or equal to 4V, the cation of the ionic liquid is Or/and (or) Wherein R 1 and R 2 are each independently an alkyl chain; When the voltage is less than or equal to 4V, the cation of the ionic liquid is selected from Wherein R 1 、R 2 、R 3 and R 4 are independently of each other an alkyl chain; The organic solvent is one or more selected from ethylene carbonate, propylene carbonate, methyl ethyl carbonate, dimethyl carbonate and diethyl carbonate; The electrolyte is one or more of lithium hexafluorophosphate, lithium bisoxalato borate, lithium difluorooxalato borate, lithium bisfluorosulfonyl imide and lithium bistrifluoromethylsulfonyl imide.
  2. 2. The lithium battery electrolyte containing nitrate ions according to claim 1, wherein the addition amount of the ionic liquid is 2%.
  3. 3. The lithium battery electrolyte containing nitrate ions according to claim 1, wherein R 1 has 1 to 6 carbon atoms and R 2 has 8 to 14 carbon atoms.
  4. 4. The lithium battery electrolyte containing nitrate ions according to claim 1, wherein R 1 has 1 to 3 carbon atoms and R 2 has 10 to 12 carbon atoms.
  5. 5. The lithium battery electrolyte containing nitrate ions according to claim 1, wherein the number of carbon atoms of R 1 is 1-6, the number of carbon atoms of R 2 is 8-14, and the number of carbon atoms of R 11 、R 12 、R 13 and R 14 are 6-14 independently of each other.
  6. 6. The lithium battery electrolyte containing nitrate ions according to claim 5, wherein the number of carbon atoms of R 1 is 1-3, the number of carbon atoms of R 2 is 10-12, and the number of carbon atoms of R 11 、R 12 、R 13 and R 14 are 8-10 independently of each other.
  7. 7. The lithium battery electrolyte containing nitrate ions according to claim 1, wherein the organic solvent is a mixture of ethylene carbonate, dimethyl carbonate and ethylmethyl carbonate in a volume ratio of 1:1:1.

Description

Lithium battery electrolyte containing nitrate ions Technical Field The invention belongs to the field of lithium battery electrolyte, relates to lithium battery electrolyte, and in particular relates to lithium battery electrolyte containing nitrate ions. Background With the continuous update of modern electric vehicles and portable electronic devices, the demand for high energy density batteries is becoming more and more urgent. Among them, lithium batteries are widely used in daily life of people because of their higher energy density. But when lithium metal comes into contact with the electrolyte, the electrolyte will decompose due to the low electrode potential of the lithium anode, forming a solid electrolyte layer (SEI) in the electrode/electrolyte interface, allowing lithium ions to pass and preventing electron transport. The SEI formed by electrolyte decomposition is a heterogeneous structure composed of organic oligomers and inorganic substances, with poor ductility and thermodynamic instability. These disadvantages will result in the SEI failing to accommodate the dynamic changes of the electrode during battery charging and discharging, which in turn results in continuous decomposition of the electrolyte and the appearance of dendritic lithium dendrites, resulting in low Coulombic Efficiency (CE) of the battery, rapid capacity decay. Meanwhile, unstable SEI has poor Li + conductivity, which hinders the transport and desolvation process of Li + in the SEI layer. Lithium nitrate (LiNO 3) is widely used as an inorganic additive in diethyl ether electrolytes. In addition, li 3 N and Li 2 O, which have high Li + conductivities, promote diffusion kinetics transport of Li + in SEI, however, carbonate organic solvents such as Ethylene Carbonate (EC), dimethyl carbonate (DMC), ethyl Methyl Carbonate (EMC), etc. can match most high-voltage cathode materials and achieve high energy density LMB (lithium metal batteries). LiNO 3 is very low in carbonate organic solvents, compared to the narrow electrochemical window of ether electrolytes (< 4V vs Li/Li +). In the prior art, researchers increase the solubility of LiNO 3 in carbonate electrolyte by adding a cosolvent and the like, but the introduced cosolvent can influence the cycle performance of the battery, so that the energy density of the battery is reduced, and the cycle of the battery is shortened. Disclosure of Invention In order to solve the technical problems, the invention aims to provide a lithium battery electrolyte containing nitrate ions. In order to achieve the technical aim, the invention provides a lithium battery electrolyte containing nitrate ions, which comprises an organic solvent, an electrolyte and an additive, wherein the organic solvent is organic carbonate, the electrolyte is lithium salt, the concentration of the electrolyte is 0.5-5 mol/L based on the volume of the organic solvent, the additive is an ionic liquid, the cation of the ionic liquid is one or more of pyrrolidine cations, pyridine cations, imidazole cations and quaternary ammonium cations, the anion of the ionic liquid is nitrate anions, and the mass content of the ionic liquid in the lithium battery electrolyte is 0.5-5%. The concentration of the electrolyte may be selected according to actual needs, but a concentration of 1mol/L is generally used. Optimally, the addition amount of the ionic liquid is 2%. When the voltage is more than or equal to 4V (high voltage, namely the charge cut-off voltage of the lithium battery), the cation of the ionic liquid isOr/and (or)Wherein R 1 and R 2 are each independently an alkyl chain. Preferably, the number of carbon atoms of R 1 is 1-6, the number of carbon atoms of R 2 is 8-14, preferably, the number of carbon atoms of R 1 is 1-3, and the number of carbon atoms of R 2 is 10-12. When the voltage is less than or equal to 4V, the cation of the ionic liquid is selected fromWherein R 1、R2、R3 and R 4 are independently of each other an alkyl chain. Preferably, the number of carbon atoms of R 1 is 1-6, the number of carbon atoms of R 2 is 8-14, the number of carbon atoms of R 11、R12、R13 and R 14 are 6-14 independently of each other, preferably the number of carbon atoms of R 1 is 1-3, the number of carbon atoms of R 2 is 10-12, and the number of carbon atoms of R 11、R12、R13 and R 14 are 8-10 independently of each other. it should be noted that the alkyl chain is not too short, the ionic liquid is not easily dissolved in the electrolyte when too short, and the alkyl chain is not too long, and the ionic liquid is unstable under high pressure when too long. In order to make the ionic liquid perform a good function in the lithium battery electrolyte, R 1 in pyrrolidine, pyridine and imidazole cations have 1-6 carbon atoms, R 2 has 8-14 carbon atoms, R 11、R12、R13、R14 in quaternary ammonium salt cations have 6-14 carbon atoms, preferably, pyrrolidine, the carbon number of R 1 in the pyridine and imidazole cations is 1-3, the carbon numb