Electrolyte Formulation for Lithium Ion Battery Temperature Trade-off
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Solution Overview
Problem
Lithium ion batteries face diminished power capability at low temperatures due to increased electrolyte viscosity, decreased conductivity, and reduced lithium ion diffusion, and existing solutions that improve low-temperature performance compromise high-temperature cycle life.
Innovation Solution
An electrolyte formulation incorporating a first lithium salt, an organic solvent other than carbonate, and additives such as fluorine-containing electron-rich species or lithium salts with oxidizing anions, which improve both low-temperature power performance and high-temperature cycle life by modifying the solid electrolyte interphase (SEI) and reducing reactivity at extreme temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If solvents with very low melting points are added to improve low temperature power capability, then viscosity decreases and power capability improves, but high temperature cycle life deteriorates
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by introducing fluorinated carbonates (F3OC(O)R) with specific molecular structures and ratios. This modifies the physical properties of the electrolyte to achieve low viscosity at low temperatures while maintaining stability at high temperatures, resolving the contradiction between power capability and cycle life
Solution Approach 2:
The patent creates a composite electrolyte system combining fluorinated carbonate esters with conventional carbonate solvents and lithium salts. This composite formulation synergistically combines the low-temperature fluidity of fluorinated compounds with the electrochemical stability of conventional components, achieving both improved power capability and maintained cycle life
2Reliability
If conventional electrolyte formulations are used to maintain high temperature cycle life, then stability is preserved, but low temperature power capability diminishes
Solution Approach 1:
The patent modifies key parameters of conventional electrolytes by incorporating fluorinated carbonate esters with specific molecular weights and fluorine substitution patterns. This changes the viscosity-temperature relationship and electrochemical window, enabling the electrolyte to maintain both high-temperature stability and low-temperature power capability
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The electrolyte formulation reduces direct current cell resistance at low temperatures and maintains or improves high-temperature cycle life, enhancing overall battery performance across a wide temperature range compared to conventional electrolytes.
Implementation Method 1
additives such as fluorine-containing electron-rich species or lithium salts with oxidizing anions, which improve both low-temperature power performance and high-temperature cycle life by modifying the solid electrolyte interphase (SEI)
Implementation Method 2
the power capability of lithium ion batteries is diminished at low temperature due to: (i) an increase in viscosity of the electrolyte resulting in slower lithium ion diffusion; (ii) a decrease in conductivity of the electrolyte
Implementation Method 3
an increase in viscosity of the electrolyte resulting in slower lithium ion diffusion; (iv) a decrease in the diffusion rate of lithium ions through the electrode materials, especially the anode
Data Source
AI summary
An electrolyte formulation including additive compounds, additive salts, or combinations thereof to improve both low temperature and high temperature performance of lithium ion batteries as compared to conventional electrolytes. Some of these embodiments further include solvents in the electrolyte solution.