Cyano-Containing Polymer Solid Electrolyte for Battery Safety
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Solution Overview
Problem
Existing solid electrolytes, particularly those using polyethylene oxide and cyano-containing dielectrics, face challenges with insufficient ionic conductivity, high contact resistance, and inertness to electrochemically active materials, limiting their practical application in secondary batteries.
Innovation Solution
A cyano-containing organic solid electrolyte is developed through the polymerization or copolymerization of specific monomers (CH2═CHCOO—(CH2)2—CN and CH2═C(CH3)COO—(CH2)2—CN) without hydroxyl groups, doped with an inorganic ion salt, to achieve high ionic conductivity and inertness to electrochemically active materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If polyethylene oxide is used as solid electrolyte, then moldability is improved, but ionic conductivity is insufficient and contact resistance with electrodes is high
Solution Approach 1:
The patent changes the chemical composition parameters by introducing cyano-containing groups and fluorinated groups into the polymer structure. These compositional changes increase dielectric constant and improve ionic conductivity while maintaining the solid electrolyte form factor, thus resolving the contradiction between ease of manufacture and reliability.
Solution Approach 2:
The patent uses composite materials by combining cyano-containing polymer segments with fluorinated polymer segments in a block copolymer structure. This composite approach allows the material to simultaneously achieve high dielectric constant (from cyano groups) and good electrochemical stability (from fluorinated groups), improving ionic conductivity while maintaining manufacturability.
2Reliability
If cyano-containing dielectrics are used as solid electrolyte, then ionic conductivity is improved, but inertness to electrochemically active material deteriorates due to gas evolution from hydroxyl groups
Solution Approach 1:
The patent extracts or removes the problematic hydroxyl groups from the polymer structure by using cyano-containing monomers that do not contain hydroxyl groups. This eliminates the source of gas evolution (alcoholate reaction with lithium ions) while preserving the high ionic conductivity provided by cyano groups, thus resolving the contradiction between reliability and harmful factors.
Solution Approach 2:
The patent converts the potential harm of cyano groups (which can lead to gas evolution when hydroxyl groups are present) into a benefit by using cyano-containing monomers without hydroxyl groups. The cyano groups provide high dielectric constant and ionic conductivity, while the absence of hydroxyl groups eliminates gas evolution, turning a potentially harmful combination into a beneficial one.
3Ease of manufacture
If conventional dielectrics like polyvinylidene fluoride are used, then moldability is improved, but ionic conductivity is insufficient due to low permittivity
Solution Approach 1:
The patent changes the dielectric parameter by introducing cyano-containing groups with high dipole moments into the polymer structure. This increases the dielectric constant from typical values (9.2 for PVDF) to much higher values, enabling sufficient ionic conductivity while maintaining the solid electrolyte form and manufacturability.
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 resulting electrolyte exhibits high ionic conductivity and inertness, reducing the risk of gas evolution in secondary batteries, with improved electrostatic energy relaxation and ion mobility, leading to enhanced battery performance and safety.
Implementation Method 1
The polymer has a very high relative permittivity and is effective in relaxing the electrostatic energy of inorganic ions
Implementation Method 2
a polymer obtained by polymerization or copolymerization of a monomer having the following formula (1) and/or a monomer having the following formula (2), the polymer being doped with an inorganic ion salt
Data Source
AI summary
An organic solid electrolyte comprises a polymer obtained by (co)polymerization of cyanoethyl acrylate and/or cyanoethyl methacrylate, the polymer being doped with an inorganic ion salt. The electrolyte has a high ionic conductivity and is based on a hydroxyl-free polymer so that it may be used to construct a secondary battery which eliminates the risk of gas evolution.