Lithium Secondary Battery Electrolyte and Formation for Swelling Control
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Solution Overview
Problem
Lithium secondary batteries using conventional carbonate-based organic solvents face issues with volatility and safety due to combustion at elevated temperatures, and eutectic mixtures, while improving safety, suffer from low lithium ion conductivity, degrading battery performance.
Innovation Solution
A lithium secondary battery using a eutectic mixture of succinonitrile and lithium salt as a solvent, with specific additives, and a novel formation step charging to 55%-65% SOC, followed by a degassing step to manage gas generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If formation step charges battery to 55%-65% SOC, then gas generation is increased, but swelling phenomenon is suppressed through subsequent degassing step
Solution Approach 1:
The patent performs a preliminary formation step at elevated temperature (40-60°C) charging to 55-65% SOC to generate gas proactively, followed by a degassing step to remove the gas before final assembly. This preliminary action prevents gas accumulation during later battery operation that would cause swelling, transforming a potential problem into a controlled process step.
Solution Approach 2:
The patent implements a rapid degassing step immediately after the formation step to quickly remove generated gas before it can cause swelling. By rushing through the gas removal process promptly, the patent prevents the harmful accumulation of gas that would otherwise lead to battery swelling and performance degradation.
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 battery achieves improved high-temperature stability, suppresses swelling, and maintains excellent initial capacity and cycle characteristics by using the eutectic mixture and optimized formation process.
Implementation Method 1
The eutectic mixture refers to a mixture of solid substances present in a liquid state in a particular eutectic temperature range, and has high stability characteristics due to a higher ignition point than conventional carbonate-based organic solvents.
Implementation Method 2
The lithium secondary battery manufactured by the method for manufacturing a lithium secondary battery according to the present invention generates a large amount of gas in the formation by applying a novel formation step including a process of charging a lithium secondary battery until a state of charge (SOC) reaches 55% to 65%
Data Source
AI summary
The present invention relates to: a lithium secondary battery including a positive electrode, a separator, and a negative electrode, the lithium secondary battery being injected with an electrolyte solution containing a eutectic mixture of succinonitrile and lithium salt as a solvent; and a method for manufacturing the lithium secondary battery.