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CN-122000472-A - Electrolyte based on propylene carbonate and application

CN122000472ACN 122000472 ACN122000472 ACN 122000472ACN-122000472-A

Abstract

The application provides an electrolyte based on propylene carbonate and application thereof, and belongs to the technical field of lithium ion batteries. The electrolyte comprises lithium salt, a nonaqueous organic solvent taking propylene carbonate as a main body and an additive, wherein the additive is a cyclic thiourethane type heterocyclic compound or an N-carbamate-3-sulfonyloxy substituted pyrrolidine compound, and the mass percentage of the additive in the electrolyte is not less than 2%. The electrolyte is a propylene carbonate system, the additive reacts at the interface of graphite before the solvent and forms a compact and stable interface film, the interface film is mainly composed of inorganic salt components such as sulfate/sulfite and the like and is constructed along with nitrogen-containing organic residues, so that the co-intercalation side reaction of propylene carbonate is inhibited, the damage of a graphite structure is reduced, the cycle stability and the long-term service life of a secondary battery are improved, and the electrolyte is applied to the secondary batteries such as lithium batteries and the like, and well solves the problems that the graphite is easily peeled off and cannot be recycled due to the co-intercalation of propylene carbonate on a graphite negative electrode.

Inventors

  • FAN XIULIN
  • LIU MENGYUAN
  • HUA JUNYI
  • LI LONG
  • CHEN LIXIN

Assignees

  • 浙江大学

Dates

Publication Date
20260508
Application Date
20260409

Claims (9)

  1. 1. An electrolyte based on propylene carbonate comprises lithium salt, a nonaqueous organic solvent taking propylene carbonate as a main body and an additive, and is characterized in that the mass percentage of the additive in the electrolyte is not less than 2 percent, the additive is a cyclic thiourethane heterocyclic compound or an N-carbamate-3-sulfonyloxy substituted pyrrolidine compound, The structural formula of the cyclic thiourethane type heterocyclic compound is as follows: , Wherein, R 1 and R 2 are selected from H atom, halogenated alkyl, halogen atom and halogenated phenyl, and R 3 is selected from any one of alkyl, branched alkyl, halogenated alkyl, phenyl, halogenated phenyl and alkenyl; The structural formula of the N-carbamate-3-sulfonyloxy substituted pyrrolidine compound is as follows: , Wherein R 4 is selected from any one of alkyl, branched alkyl, halogenated alkyl, phenyl, halogenated phenyl and alkenyl, and R 5 is selected from any one of alkyl, branched alkyl, halogenated alkyl, phenyl, halogenated phenyl and alkenyl.
  2. 2. The propylene carbonate-based electrolyte according to claim 1, wherein the halogen in the haloalkyl group, halogen atom or halophenyl group is F, cl or Br.
  3. 3. A propylene carbonate-based electrolyte according to claim 1, wherein the additive is t-butyl 1,2, 3-oxathiazolidine-3-carboxylate 2, 2-dioxide, 5- (trifluoromethyl) -1,2, 3-oxathiazolidine-3-carboxylate t-butyl 2, 2-dioxide, (S) -4- (2, 5-difluorophenyl) -1,2, 3-oxathiazolidine-3-carboxylate t-butyl 2, 2-dioxide, (S) -4- (3, 4-difluorophenyl) -1,2, 3-oxathiazolidine-3-carboxylate t-butyl 2, 2-dioxide, 4- (4-bromobenzyl) -1,2, 3-oxathiazolidine-3-carboxylate t-butyl 2, 2-dioxide, (S) -4- (2-t-butoxy-2-oxoethyl) -1,2, 3-oxathiazolidine-3-carboxylate t-butyl 2, 2-dioxide, (R) -3- (t-butoxycarbonyl) -1,2, 3-oxathiazolidine-3-carboxylate, R) -1,2, 3-oxathiazolidine-carboxylate, R) -2, 2-dioxide, 4- (4-bromobenzyl) -1,2, 3-oxathiazolidine-carboxylate, 3-tert-butyl 2, 2-oxide, (S) -4- (2-t-butoxy-2-oxo-ethyl) -1,2, 3-oxathiazolidine-carboxylate, 3-butyl carboxylate, R-3-2, 3-butoxycarbonyl At least one of 1- (tert-butoxycarbonyl) -3- (trifluoromethanesulfonyl) pyrrolidine, methyl 3- (methylsulfonyloxy) pyrrolidine-1-carboxylate, and tert-butyl 3- [ (4-chlorophenyl) sulfonyl ] pyrrolidine-1-carboxylate.
  4. 4. The propylene carbonate-based electrolyte as claimed in claim 1, wherein the mass percentage of the additive in the electrolyte is 2-10%.
  5. 5. The electrolyte of claim 1, wherein the lithium salt is any one of lithium bis (fluorosulfonyl) imide, lithium bis (trifluoromethylsulfonyl) imide, lithium bis (oxalato) borate, lithium difluoro (oxalato) borate, lithium hexafluorophosphate, lithium tetrafluoroborate, and organic anion lithium salt.
  6. 6. The propylene carbonate-based electrolyte as claimed in claim 1, wherein the lithium salt concentration is 0.2-3.0 mol/L.
  7. 7. The propylene carbonate-based electrolyte of claim 1, further comprising a carbonate co-solvent selected from the group consisting of dimethyl carbonate, diethyl carbonate and ethylmethyl carbonate.
  8. 8. The method for preparing the electrolyte solution for the secondary battery, which is characterized in that the secondary battery comprises a positive electrode and a negative electrode, wherein an active material of the positive electrode is at least one of a layered oxide positive electrode material, a spinel positive electrode material or an olivine positive electrode material, and an active material of the negative electrode is artificial graphite, natural graphite or composite graphite.
  9. 9. An electrical device comprising the secondary battery in the application of claim 8.

Description

Electrolyte based on propylene carbonate and application Technical Field The application relates to an electrolyte based on propylene carbonate and application thereof, and belongs to the technical field of lithium ion batteries. Background Lithium Ion Batteries (LIBs) have become the energy storage device of choice for electric vehicles and portable electronic devices because of their high specific energy, low self-discharge, good cycle characteristics, no memory effect, and environmental friendliness. Graphite is the most widely used commercial anode material at present because of higher theoretical specific capacity (372 mAh/g), lower working potential (0.1V-0.2V vs. Li/Li +) and good structural stability. However, the interfacial stability of graphite is highly dependent on the solid electrolyte interfacial film (SEI) formed by the electrolyte at the first turn. The existing commercial electrolyte mostly adopts a Ethylene Carbonate (EC) system, and EC can be reduced preferentially on the surface of graphite and form relatively stable SEI, so that reversible lithium intercalation is realized. However, the problems of high EC melting point, limited stability at high voltages, etc., limit the further applications of batteries in wide temperature ranges and high nickel positive electrode systems. Propylene Carbonate (PC) has a wide liquid phase temperature range and good compatibility with high nickel anodes, and is considered as an important candidate solvent for achieving a wide temperature range electrolyte. However, PC is often difficult to form an effective SEI on a graphite negative electrode, and co-intercalation with lithium ions is easy to occur and the peeling and damage of a graphite layer are initiated, resulting in a significant drop in first-cycle efficiency and cycle life. To solve the PC co-intercalation problem, the prior art attempts to regulate the interface by adjusting electrolyte salt concentration, introducing co-solvents or using additives. Although the above strategy improves PC to some extent the compatibility with graphite, the following drawbacks still exist: 1) The SEI quality is poor, and in the SEI film generated by reduction of the existing additive, the content of inorganic components (such as LiF, li 2 O and the like) with high ionic conductivity and high strength is low, and the SEI film consumes more rapidly in the circulating process. 2) The structural design is single, the reaction sites of most additive molecules are limited, and a multi-component and multifunctional composite SEI structure is difficult to construct in the reduction process. Disclosure of Invention In order to solve the defects existing in the prior art, particularly to the specific problem that Propylene Carbonate (PC) is easy to co-embed on a graphite negative electrode and causes structural stripping, the first aspect of the applicant aims to provide an electrolyte based on propylene carbonate, which not only can further enrich the composition and structural characteristics of SEI, but also can realize negative electrode stabilization, and well solves the problems that propylene carbonate is easy to co-embed on the graphite negative electrode and causes graphite stripping and cycle performance reduction. Specifically, the application is realized by the following scheme: The electrolyte comprises lithium salt, a solvent and an additive, wherein the solvent is a nonaqueous organic solvent taking propylene carbonate as a main body, the additive is a cyclic thiourethane heterocyclic compound or an N-carbamate-3-sulfonyloxy substituted pyrrolidine compound, and the mass percentage of the additive in the electrolyte is not less than 2%. The structural formula of the cyclic thiourethane type heterocyclic compound is as follows: 。 Wherein R 1 and R 2 are selected from any one of H atom, halogenated alkyl group, halogen atom and halogenated phenyl group, and R 3 is selected from any one of alkyl group, branched alkyl group, halogenated alkyl group, phenyl group, halogenated phenyl group and alkenyl group. The structural formula of the N-carbamate-3-sulfonyloxy substituted pyrrolidine compound is as follows: 。 Wherein R 4 is selected from any one of alkyl, branched alkyl, halogenated alkyl, phenyl, halogenated phenyl and alkenyl, and R 5 is selected from any one of alkyl, branched alkyl, halogenated alkyl, phenyl, halogenated phenyl and alkenyl. The application designs and develops an additive which has multiple polar bonds and can generate multiple reaction sites in the reduction process aiming at a solvent system taking propylene carbonate as a main body, wherein the additive is a nitrogen-containing heterocycle which has a cyclic sulfur-containing skeleton and multiple polar bonds, a carbamate connecting unit (-N-C (=O) -O-R) is introduced into the nitrogen-containing heterocycle, a C-O bond site which can trigger cracking is reserved, and the sulfur-containing polar bonds are cooperated with carbamate gro