Fluorophosphate Electrolyte Additives for High-Voltage Battery Cycle Life
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Solution Overview
Problem
Nonaqueous-electrolyte secondary batteries face challenges in achieving high capacity, high-temperature storability, continuous-charge characteristics, and cycle performances, particularly under high-voltage conditions, with existing techniques showing limited improvements and poor cycle performances.
Innovation Solution
Incorporating a fluorophosphoric acid salt and an iron-group element into the nonaqueous electrolyte, specifically a monofluorophosphate and/or difluorophosphate, and an iron-group element in a specific concentration, to enhance cycle performances and output characteristics while maintaining high capacity and storability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a lithium fluorophosphate compound is added to inhibit self-discharge at high temperatures, then high-temperature storability is improved, but cycle performances deteriorate especially under high-voltage conditions
Solution Approach 1:
The patent changes the chemical composition parameters by introducing a specific fluorophosphoric acid salt (monofluorophosphate and/or difluorophosphate) with controlled concentration (0.01-5% by mass), which modifies the electrolyte's properties to simultaneously improve high-temperature storability and maintain cycle performances under high-voltage conditions
Solution Approach 2:
The patent creates a composite electrolyte system by combining fluorophosphoric acid salt with specific nonaqueous solvents (cyclic carbonate, chain carbonate, cyclic carboxylate) and lithium salts, forming a multi-component system where each component contributes to both thermal stability and electrochemical performance
2Power
If tetrafluoroboric acid salt is added to improve output characteristics, then low-temperature output characteristics are improved, but high-voltage cycle performances remain limited
Solution Approach 1:
The patent modifies the electrolyte composition by incorporating fluorophosphoric acid salt at optimized concentrations, which enhances both power output and high-voltage cycle stability through improved ionic conductivity and electrode interface stability
Solution Approach 2:
The fluorophosphoric acid salt acts as an intermediary substance that mediates between the electrode and electrolyte, forming protective films that enable both high power output and sustained cycle performance under high-voltage conditions
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 solution significantly improves cycle performances under high-voltage conditions and maintains high capacity and high-temperature storability, achieving better battery performance compared to existing techniques.
Implementation Method 1
a nonaqueous organic solvent is required to have a high permittivity for dissociating the lithium salt
Implementation Method 2
to show high ionic conductivity in a wide temperature range
Data Source
AI summary
The present invention provides a nonaqueous electrolyte mainly comprising a nonaqueous solvent and an electrolyte dissolved therein, wherein the nonaqueous electrolyte comprises at least one compound selected from the group consisting of saturated chain hydrocarbons, saturated cyclic hydrocarbons, aromatic compounds having a halogen atom, and ethers having a fluorine atom, and further comprises a monofluorophosphate and/or a difluorophosphate.