Search

CN-122025820-A - Low-concentration safe lithium ion battery electrolyte and lithium ion battery

CN122025820ACN 122025820 ACN122025820 ACN 122025820ACN-122025820-A

Abstract

The invention relates to the technical field of lithium ion batteries, and discloses a low-concentration safe lithium ion battery electrolyte and a lithium ion battery, wherein the electrolyte consists of lithium salt, a carbonate main solvent, a diluent and a fluorinated phosphite additive, the total concentration of the lithium salt is 0.5-0.8 mol/L, the carbonate main solvent accounts for 50-70%, the diluent accounts for 15-20%, and the fluorinated phosphite additive accounts for 10-15%. According to the invention, the fluorinated phosphite additive is introduced, so that the use amount of lithium salt is reduced, and meanwhile, the stability of an electrolyte system can be maintained, thereby effectively reducing the cost of lithium salt, being beneficial to improving the cycle stability of a lithium ion battery, having higher voltage stability, and being capable of stably operating under a high-nickel positive electrode system, and further improving the energy density of the lithium ion battery.

Inventors

  • LI CHUNZHONG
  • CHEN LONG
  • JI YUN

Assignees

  • 华东理工大学

Dates

Publication Date
20260512
Application Date
20260407

Claims (8)

  1. 1. The low-concentration safe lithium ion battery electrolyte is characterized by comprising a lithium salt, a carbonate main solvent, a diluent and a fluorinated phosphite ester additive, wherein the total concentration of the lithium salt is 0.5-0.8 mol/L, the carbonate main solvent accounts for 50-70%, the diluent accounts for 15-20%, and the fluorinated phosphite ester additive accounts for 10-15%.
  2. 2. The low concentration safety lithium ion battery electrolyte of claim 1 wherein the lithium salt comprises at least one of lithium hexafluorophosphate, lithium bis-fluorosulfonyl imide, lithium trifluoromethylsulfonyl imide, lithium bis-oxalato borate, and lithium difluoro-oxalato borate.
  3. 3. The low concentration safety lithium ion battery electrolyte of claim 1, wherein the carbonate-based main solvent comprises at least one of ethylene carbonate, dimethyl carbonate, diethyl carbonate, methylethyl carbonate, propylene carbonate, fluoroethylene carbonate, and bis (2, 2-trifluoroethyl) carbonate.
  4. 4. The low-concentration safe lithium ion battery electrolyte as claimed in claim 1, wherein, the diluent comprises 1, 2-tetrafluoroethyl-2, 2-trifluoroethyl ether 1, 2-tetrafluoroethyl-2, 3-tetrafluoropropyl ether at least one of fluorobenzene, 3-fluorotoluene and 1,3, 5-trifluorobenzene.
  5. 5. The low-concentration safe lithium ion battery electrolyte as claimed in claim 1, wherein, the fluorinated phosphite additives include tris (2, 2-trifluoroethyl) phosphite, tris (1, 3-hexafluoroisopropyl) phosphite at least one of tris (2, 3-tetrafluoropropyl) phosphite and tris (2, 3-pentafluoropropyl) phosphite.
  6. 6. The lithium ion battery is characterized by comprising a positive electrode, a negative electrode, a diaphragm and the low-concentration safe lithium ion battery electrolyte as claimed in any one of claims 1-5.
  7. 7. The lithium ion battery of claim 6, wherein the positive electrode active material of the positive electrode comprises at least one of lithium cobaltate, lithium manganate, lithium iron phosphate, and ternary lithium material comprising at least one of LiNi 0.8 Mn 0.1 Co 0.1 O 2 、LiNi 0.6 Mn 0.2 Co 0.2 O 2 、LiNi 0.5 Mn 0.3 Co 0.2 O 2 and LiNi 0.3 Mn 0.3 Co 0.3 O 2 .
  8. 8. The lithium ion battery of claim 6, wherein the negative electrode active material of the negative electrode comprises at least one of natural graphite, mesophase carbon microspheres, KS-6, KS-4, and lithium metal negative electrodes.

Description

Low-concentration safe lithium ion battery electrolyte and lithium ion battery Technical Field The invention relates to the technical field of lithium ion batteries, in particular to a low-concentration safe lithium ion battery electrolyte and a lithium ion battery. Background The electrolyte plays a critical role in ion transport and internal circuit conduction of the lithium ion battery. In the development of electrolytes, low cost and high safety are two major core dimensions of the design. Conventional commercial lithium ion battery electrolytes typically require maintaining an overall salt concentration of at least 1 mol/L to ensure adequate ionic conductivity to achieve satisfactory electrochemical performance. However, in such conventional systems, although the electrolyte occupies about 7% of the electrolyte cost, the use of the Low Concentration Electrolyte (LCEs) can significantly reduce the cost and bring about the advantages of a wider wide temperature operating range, the low concentration electrolyte also faces a serious technical bottleneck. Specifically, a decrease in salt concentration not only directly results in a decrease in ionic conductivity, but also initiates a solvent-dominated solvated structure. The structure is unfavorable for constructing a stable interfacial film rich in inorganic components, and a solvent is easy to decompose on the surface of a negative electrode (particularly a graphite negative electrode), so that a solid electrolyte interfacial film with loose and unstable structure is formed, and the cycle stability and the rate performance of a battery are obviously reduced. In addition, the traditional electrolyte system is easy to generate oxidative decomposition under the high-voltage condition, so that the problem of unstable interfaces is further aggravated, and meanwhile, the inflammable characteristic of the electrolyte can bring potential safety hazards. For improving the safety, it is generally necessary to introduce flame retardant additives, such as phosphorus-containing compounds, but the existing phosphate additives can enhance the interaction between lithium ions and solvents due to the strong lithium ion solvating capability, so that the lithium ions are more difficult to desolvate, and the transmission process of the lithium ions at the electrode interface is affected. On the other hand, active species such as hydrogen radicals (H) or hydroxyl radicals (OH) are generated during combustion, and these radicals further promote the combustion chain reaction. While some additives can inhibit combustion to some extent, they tend to have an adverse effect on electrochemical performance. Thus, there is a difficult reconciliation between cost, safety and electrochemical performance in the prior art. On the one hand, the cost needs to be reduced and the temperature application range needs to be widened by reducing the salt concentration, and on the other hand, the problems of conductivity reduction, unstable interface and safety caused by the problems need to be avoided. How to maintain low salt concentration to reduce cost, inhibit the flammability of electrolyte and improve interface stability and dynamic performance, thereby realizing a low concentration electrolyte system with high safety and long cycle life is still an important technical problem to be solved currently. Disclosure of Invention The invention aims to solve the defects in the prior art, and provides a low-concentration safe lithium ion battery electrolyte and a lithium ion battery. In order to achieve the above purpose, the present invention adopts the following technical scheme: The low-concentration safe lithium ion battery electrolyte consists of lithium salt, a main solvent of carbonate, a diluent and a fluorinated phosphite ester additive, wherein the total concentration of the lithium salt is 0.5-0.8 mol/L, the main solvent of carbonate accounts for 50-70%, the diluent accounts for 15-20%, and the fluorinated phosphite ester additive accounts for 10-15%. Preferably, the lithium salt includes at least one of lithium hexafluorophosphate, lithium difluorosulfonimide, lithium trifluoromethylsulfonimide, lithium bisoxalato borate and lithium difluorooxalato borate. Preferably, the carbonate-based main solvent includes at least one of ethylene carbonate, dimethyl carbonate, diethyl carbonate, methylethyl carbonate, propylene carbonate, fluoroethylene carbonate, and bis (2, 2-trifluoroethyl) carbonate. Preferably, the method comprises the steps of, the diluent comprises 1, 2-tetrafluoroethyl-2, 2-trifluoroethyl ether 1, 2-tetrafluoroethyl-2, 3-tetrafluoropropyl ether at least one of fluorobenzene, 3-fluorotoluene and 1,3, 5-trifluorobenzene. Preferably, the method comprises the steps of, the fluorinated phosphite additives include tris (2, 2-trifluoroethyl) phosphite, tris (1, 3-hexafluoroisopropyl) phosphite at least one of tris (2, 3-tetrafluoropropyl) phosphite and tris (2, 3-pentafluoropropyl)