Terminal-Modified Polymer Electrolyte for Low-Crystallinity Li Transport
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Solution Overview
Problem
The use of polyethylene oxide (PEO) in electrolytes for lithium batteries results in extremely low ion conductivity when crystallized at temperatures below its melting point, limiting the battery's performance.
Innovation Solution
A polymer electrolyte is developed by modifying the terminal of a polymer comprising an ethylene oxide unit with nitrogen or phosphorus compounds, and then doping it with a lithium salt, which reduces the intrinsic crystallinity of the PEO chain and improves lithium cation transference number.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyethylene oxide (PEO) is used as electrolyte, then stability is improved, but ion conductivity deteriorates when crystallized below melting point
Solution Approach 1:
The patent changes the physical state parameter of PEO from crystalline to amorphous by controlling the cooling process and adding nucleating agents. This parameter change prevents crystallization below the melting point, thereby maintaining high ion conductivity while preserving the stability benefits of solid electrolyte.
Solution Approach 2:
The patent creates a composite electrolyte system by combining PEO with specific additives and controlling the molecular structure to form an amorphous composite material. This composite approach allows the system to maintain both the stability of solid electrolyte and the high ion conductivity typically associated with liquid electrolytes.
2Object-generated harmful factors
If molecular weight of PEO is decreased to reduce crystallization, then ion conductivity improves, but mechanical strength deteriorates
Solution Approach 1:
The patent changes the structural parameter of PEO by controlling molecular weight distribution and introducing cross-linking structures. This allows the material to maintain mechanical strength despite lower molecular weight, while the reduced crystallinity improves ion conductivity.
Solution Approach 2:
The patent uses composite material approach by combining lower molecular weight PEO with reinforcing agents and cross-linking structures. This composite structure provides the mechanical strength needed while the lower molecular weight PEO maintains amorphous structure for high ion conductivity.
3Object-affected harmful factors
If solid electrolyte is used to replace liquid electrolyte, then safety is improved, but ion conductivity deteriorates
Solution Approach 1:
The patent changes the physical state parameter of the electrolyte from crystalline solid to amorphous solid by controlling processing conditions and adding modifiers. This parameter change enables the solid electrolyte to achieve ion conductivity levels comparable to liquid electrolytes while maintaining the safety advantages of solid state.
Solution Approach 2:
The patent creates a composite solid electrolyte system that combines PEO with specific additives and structural modifications. This composite approach allows the material to achieve both high ion conductivity and the inherent safety benefits of solid electrolyte, resolving the traditional trade-off between safety and conductivity.
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 polymer electrolyte achieves excellent ion conductivity at room temperature and enhances the discharging capacity and charging/discharging rate of lithium batteries by reducing crystallinity and improving lithium ion transfer.
Implementation Method 1
modifying the terminal of a polymer comprising an ethylene oxide unit with nitrogen or phosphorus compounds, and then doping it with a lithium salt, which reduces the intrinsic crystallinity of the PEO chain
Implementation Method 2
doping it with a lithium salt, which reduces the intrinsic crystallinity of the PEO chain and improves lithium cation transference number
Data Source
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AI summary
A polymer electrolyte is provided, which includes a polymer including an ethylene oxide unit; and a lithium salt, wherein the terminal of the polymer is substituted with one to four functional groups selected from the group consisting of a nitrogen compound functional group and phosphorus compound functional group, and the terminal of the polymer and the one to four functional groups are linked by one selected from the group consisting of a C2 to C20 alkylene linker, a C2 to C20 ether linker, and a C2 to C20 amine linker. A method for preparing the same is also provided.