Electrolyte Composition for Overcharge Heat and SEI Stability
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Solution Overview
Problem
Large-capacity energy storage devices face safety issues due to poor heat dissipation during overcharging, leading to chemical reactions, cell failure, and potential fires, as existing electrolytes fail to effectively manage heat and maintain conductivity.
Innovation Solution
An electrolyte composition comprising a fluorinated solvent, cyclic carbonate, and lithium hexafluorophosphate, with specific mass percentages, is introduced to enhance oxidation resistance, reduce heat generation, and ensure sufficient lithium ion conductivity, while stabilizing the fluorinated solvent and forming a dense solid electrolyte interphase film to improve overcharging safety and charging/discharging cycle performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fluorinated solvent is introduced into the electrolyte to enhance oxidation resistance and reduce heat generation, then overcharging safety performance is improved, but the fluorinated solvent is prone to undergo reduction reaction at the cathode, affecting film formation and stability
Solution Approach 1:
The patent introduces cyclic carbonate as an intermediary substance that mediates between the fluorinated solvent and the cathode. The cyclic carbonate preferentially undergoes reduction reaction at the cathode to form a stable SEI film, preventing the fluorinated solvent from directly contacting and reacting with the cathode, thus maintaining both safety performance and solvent stability
Solution Approach 2:
The patent optimizes the concentration parameters of the electrolyte components, specifically controlling the fluorinated solvent content at 5-20% and cyclic carbonate content at 10-30%. By adjusting these parameter ranges, the electrolyte achieves optimal balance between oxidation resistance, heat generation reduction, and fluorinated solvent stability
2Reliability
If the content of cyclic carbonate is increased to form a dense SEI film and stabilize the cathode, then charging/discharging cycle performance is improved, but the film formation process may compete with fluorinated solvent, affecting overall performance
Solution Approach 1:
The patent applies partial action by controlling the cyclic carbonate content at 10-30%, which is sufficient to form the necessary SEI film and stabilize the cathode without excessive concentration that would cause harmful side reactions or competition with the fluorinated solvent. This optimized partial concentration achieves the desired film formation while maintaining system balance
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 proposed electrolyte composition effectively reduces heat accumulation, enhances overcharging safety, and improves the charging/discharging cycle performance of energy storage devices by stabilizing the fluorinated solvent and forming a protective film, thereby preventing cell failure and fires.
Implementation Method 1
reduce the heat generated by an oxidation reaction occurring in the electrolyte during an overcharging process
Implementation Method 2
reduce a content of Lewis acid formed by an reaction between the lithium hexafluorophosphate in the electrolyte and the water in the electrolyte
Implementation Method 3
using a characteristic that the cyclic carbonate can be ring-opened polymerized at a cathode to form a dense SEI film
Implementation Method 4
ensure that there is a sufficient conductivity of lithium ions in the electrolyte
Data Source
AI summary
The present disclosure provides an electrolyte and an energy storage device. The electrolyte includes, by mass of electrolyte, a fluorinated solvent with a mass percentage a, a cyclic carbonate with a mass percentage b, and a lithium hexafluorophosphate with a mass percentage c, wherein 1%≤a≤30%, 25%≤b≤45%, and 7%≤c≤10%.