Li-Ion Electrolyte Additives for Low-Temp and High-Temp Cycling
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Solution Overview
Problem
Lithium-ion batteries face a significant challenge in maintaining performance at low temperatures, as high-impedance film-forming additives degrade low-temperature performance, while high-kinetic electrolytes compromise high-temperature cycle and storage performance.
Innovation Solution
An electrolyte composition including a compound of Formula I and an additive A, such as fluoroethylene carbonate, is developed, with specific weight ratios and concentrations to enhance both low-temperature and high-temperature performance, incorporating additional compounds like Formula II, III, and IV to further improve cycle and storage performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-impedance film-forming additives are used to improve cycle performance, then cycle performance is improved, but low-temperature performance deteriorates and impedance increases
Solution Approach 1:
The patent modifies the chemical structure of film-forming additives by introducing specific functional groups ( Formula I structure with R1-R8 substituents and X counterions) to change their film-forming characteristics. This structural parameter change enables the additive to form protective films while maintaining low-temperature ionic conductivity, thus improving cycle performance without sacrificing low-temperature performance
Solution Approach 2:
The patent combines multiple components including the compound of Formula I, lithium salts (LiPF6, LiBF4, LiClO4), and carbonate solvents (EC, PC, DMC, DEC) to create a composite electrolyte system. This composite approach synergistically improves cycle performance through film formation while maintaining low-temperature performance through the combined properties of different components
2Object-affected harmful factors
If high-kinetic electrolytes are used to improve low-temperature performance, then low-temperature performance is improved, but high-temperature cycle and storage performance deteriorates
Solution Approach 1:
The patent adjusts the kinetic parameters of the electrolyte by optimizing the compound structure of Formula I and controlling its concentration (0.01-16 wt%), creating a balanced kinetic profile that provides sufficient low-temperature reactivity while maintaining stability at high temperatures through the protective film formation mechanism
Solution Approach 2:
The film-forming additive (Formula I compound) performs preliminary action by forming a stable protective film on electrode surfaces during initial cycles. This pre-formed film acts as a barrier that prevents harmful reactions at high temperatures while allowing ionic transport at low temperatures, thus resolving the contradiction between low-temperature performance and high-temperature stability
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 composition effectively improves cycle and storage performance at high temperatures and low temperatures, reducing resistance and maintaining capacity retention, as demonstrated in lithium-ion battery tests.
Implementation Method 1
a common strategy is to use an additive capable of forming a film on the positive electrode and negative electrode
Implementation Method 2
a common method is to improve kinetics of electrolyte
Data Source
AI summary
An electrolyte, comprising a compound of Formula I and an additive A,R1, R2, R3, R4, R5, R6, R7 and R8 are each independently selected from: hydrogen, halo, —COOX, substituted or unsubstituted C1-8alkyl, substituted or unsubstituted C2-10alkenyl, substituted or unsubstituted C2-10alkynyl, substituted or unsubstituted C1-8alkoxy, or —Ra—S(═O)2—Rb, wherein Ra is selected from substituted or unsubstituted C1-8alkylene, Rb is selected from halo or substituted or unsubstituted C1-8alkyl, and at least one of R1, R2, R3, R4, R5, R6, R7 and R8 is —COOX. When substituted, the substituent is selected from cyano or halo; andX is selected from Li+, Na+, K+ or Rb+. The additive A is at least one selected from fluoroethylene carbonate, LiPO2F2, or vinylene carbonate.