Polymer Electrolyte Cell Overcharge Safety
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Solution Overview
Problem
Existing polymer electrolyte secondary cells are not adequately safe against overcharging, as they can emit smoke or ignite due to the flammability of organic solvents when overcharged.
Innovation Solution
Incorporating a tertiary carboxylic acid ester, such as methyl trimethylacetate, and a polymerized monomer containing alkylene glycol (meth)acrylate and/or N,N-dialkyl (meth)acrylamide into the non-aqueous solvent and electrolyte, which prevents smoke emission and ignition during overcharging by enhancing safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If organic solvent is used in the polymer electrolyte, then high energy density and high capacity are achieved, but smoke emission and ignition occur during overcharging
Solution Approach 1:
The patent converts the harmful flammability of organic solvents into a beneficial safety feature by adding specific flame retardants (phosphorus-containing compounds and nitrogen-containing compounds) that activate during overcharging to suppress combustion while maintaining the energy storage function of the organic solvent
Solution Approach 2:
The patent introduces flame retardant compounds as intermediary substances that mediate between the organic solvent and oxygen during overcharging, preventing direct combustion while allowing controlled electrochemical reactions to proceed
2Reliability
If flame retardant additives are added to prevent smoke and ignition, then safety against overcharging is improved, but charge-discharge reaction efficiency may be reduced
Solution Approach 1:
The patent optimizes the concentration parameters of flame retardant additives (phosphorus-containing compounds at 0.01-5 wt% and nitrogen-containing compounds at 0.01-5 wt%) to achieve the minimum effective dosage that provides safety while minimizing interference with charge-discharge reactions
Solution Approach 2:
The patent creates local safety zones around electrode surfaces where flame retardant compounds concentrate during overcharging, providing targeted fire suppression at critical locations while leaving the bulk electrolyte functionally intact for efficient ion transport
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 combination effectively improves safety against overcharging by preventing smoke and ignition, with optimal concentrations of these components ensuring efficient charge-discharge reactions while maintaining cell performance.
Implementation Method 1
Popular polymer electrolytes consist of a polymer matrix and a non-aqueous electrolytic solution contained therein
Data Source
AI summary
A polymer electrolyte secondary cell with high safety against overcharging includes a positive electrode containing a positive electrode active material; a negative electrode containing a negative electrode active material; a polymer electrolyte containing a non-aqueous solvent, an electrolyte salt, and a polymer. The non-aqueous solvent contains a tertiary carboxylic acid ester shown in Formula 1 below. The polymer is formed from monomers containing alkylene glycol (meth)acrylate and/or N,N-dialkyl (meth)acrylamide.where R1 to R4 each denote a straight-chained or branched alkyl group having 4 or less carbon atoms and may be the same or different.