Electrolyte additives for high-temperature lithium battery stability
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Solution Overview
Problem
Non-aqueous electrolyte lithium batteries experience significant deterioration in battery characteristics and short battery lifetime due to electrolyte decomposition at high temperatures, particularly above 60°C, which necessitates cooling mechanisms and affects their cycle and output characteristics.
Innovation Solution
An electrolyte for non-aqueous electrolyte batteries comprising lithium hexafluorophosphate, a phosphorus-containing acidic compound (such as HPF6) within specific concentration ranges, and difluorophosphate, which improves cycle characteristics under high temperature environments by forming protective coating films on electrodes, reducing degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cooling mechanisms are provided to maintain battery temperature at 60°C or lower, then battery characteristics are maintained, but energy consumption increases
Solution Approach 1:
The patent converts the harmful effect of high temperature (which causes electrolyte decomposition and battery deterioration) into a beneficial outcome by using the phosphorus-containing compound and difluorophosphate combination to form stable coating films that protect the electrodes. This allows the battery to operate reliably at high temperatures without requiring active cooling, thereby eliminating the energy consumption associated with cooling mechanisms while maintaining battery characteristics.
2Power
If fluorine-containing electrolyte compound is dissolved in cyclic carbonate or chain carbonate to achieve high battery voltage and capacity, then battery voltage and capacity are improved, but electrolyte decomposition occurs at high temperature
Solution Approach 1:
The patent introduces phosphorus-containing compound (HPF6) and difluorophosphate as intermediary substances that mediate between the fluorine-containing electrolyte compound and the electrode surfaces. These intermediaries form protective coating films that prevent direct contact and decomposition reactions between the electrolyte and electrodes at high temperatures, thereby maintaining electrolyte stability while preserving the high voltage and capacity characteristics provided by the fluorine-containing compound.
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 maintains high discharge capacity and improves cycle characteristics even after repeated charge/discharge cycles under high temperature conditions, potentially eliminating the need for cooling mechanisms by reducing energy consumption and extending battery life.
Implementation Method 1
there occurs reaction of lithium difluorophosphate with electrode surfaces during initial charge/discharge cycles such that good coating films are formed on positive and negative electrodes
Implementation Method 2
non-aqueous electrolyte lithium batteries including lithium ion batteries, lithium batteries and lithium ion capacitors
Data Source
AI summary
An electrolyte for a non-aqueous electrolyte battery includes a non-aqueous organic solvent and at least lithium hexafluorophosphate as a solute, characterized by further including 10 to 1000 mass ppm of a phosphorus-containing acidic compound and 0.01 to 10.0 mass% of a difluorophosphate. The phosphorus-containing acidic compound is preferably at least one selected from the group consisting of HPF6, HPO2F2, H2PO3F and H3PO4. By the use of such an electrolyte, it is possible to provide the non-aqueous electrolyte lithium battery capable of maintaining high discharge capacity even after repeated charge/discharge cycles under a high temperature environment.