Gel-Forming Battery Electrolyte for Thermal Runaway Isolation
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Solution Overview
Problem
Rechargeable lithium batteries face ignition and explosion risks at high temperatures due to increased electrical resistance, which can lead to overheating and spread of heat among adjacent cells.
Innovation Solution
An electrolyte for rechargeable lithium batteries containing a first additive that gels at high temperatures and a second additive that binds to the positive electrode transition metal oxide, increasing viscosity and reducing ionic conductivity to disconnect the cell from surroundings, thereby suppressing ignition and explosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the battery operates at relatively high temperature, then the energy density and charging rate are improved, but the electrical resistance increases leading to ignition and explosion risks
Solution Approach 1:
The patent changes the physical state parameter of the electrolyte by adding gel-forming additives (polyacrylonitrile and carboxymethyl cellulose) that transform the electrolyte from liquid to gel state at high temperatures, fundamentally altering its flow properties and ionic conductivity to prevent thermal runaway
Solution Approach 2:
The gel-forming additives act as intermediary substances between the electrolyte and the electrode assembly, modifying the electrolyte's behavior at high temperatures to prevent direct thermal contact and heat transfer that would lead to ignition and explosion
2Reliability
If the viscosity of the electrolyte increases rapidly, then the ionic conductivity decreases to disconnect the cell, but the battery performance and charging rate are reduced
Solution Approach 1:
The patent creates a dynamic system where the electrolyte's viscosity and ionic conductivity are not fixed but change in response to temperature conditions - remaining liquid and conductive during normal operation, then transforming to gel state with reduced conductivity when thermal runaway is detected, providing adaptive safety control
Solution Approach 2:
The gel-forming additives are pre-incorporated into the electrolyte formulation at low concentrations, preparing the system in advance so that upon heating, the gelation occurs rapidly and automatically without requiring external intervention or additional components
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 effectively prevents temperature increase and reduces the risk of ignition and explosion in lithium battery cells, even if an adjacent cell ignites or explodes, by rapidly increasing viscosity and disconnecting the cell.
Implementation Method 1
a first additive represented by Chemical Formula 1... may rapidly increase the viscosity of the electrolyte... at relatively high temperatures
Implementation Method 2
a second additive represented by Chemical Formula 2... may delay structural collapse of the positive electrode surface at relatively high temperatures
Data Source
Figure 1
AI summary
An electrolyte for a rechargeable lithium battery and a rechargeable lithium battery including the same are provided. The electrolyte includes a non-aqueous organic solvent; a lithium salt; a first additive represented by Chemical Formula 1. and a second additive represented by Chemical Formula 2.