Crosslinked Polymer Electrolyte for Safe High-Conductivity Li-Ion Cells
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Solution Overview
Problem
Conventional lithium-ion batteries face safety concerns due to flammable liquid electrolytes, which can lead to short-circuiting, overheating, and explosions, especially as energy density increases, necessitating the development of safer and more stable polymer electrolytes for improved cycling performance.
Innovation Solution
The use of crosslinked polymer electrolytes with additives containing element F and P, synthesized with crosslinkers having three or more polymerizable terminals, which enhance ionic conductivity and stability, forming a heterogeneous polymer network that improves cycling performance and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If liquid electrolyte is used in lithium-ion battery, then ionic conductivity is improved, but safety deteriorates due to flammability
Solution Approach 1:
The patent changes the physical state of the electrolyte from liquid to solid polymer form, fundamentally altering the parameters of the electrolyte system. This transformation maintains ionic conductivity through the polymer matrix while eliminating the flammability issue inherent in liquid electrolytes, thus resolving the contradiction between conductivity and safety
Solution Approach 2:
The patent employs composite materials by combining polymer electrolyte with specific additives (LiBF4, LiPF6, lithium difluorophosphate, lithium fluorophosphate) to create a heterogeneous polymer network. This composite approach enhances both the ionic conductivity and electrochemical stability, simultaneously addressing the conductivity and safety requirements
2Power
If energy density of lithium-ion battery is increased, then power output is improved, but safety deteriorates due to higher risk of failure
Solution Approach 1:
The patent converts the potential harm of high energy density (increased safety risk) into a benefit by using polymer electrolytes that inherently provide better safety. The solid polymer matrix with crosslinked structure contains potential failure modes, transforming the high-energy system into a safer configuration while maintaining power output
3Reliability
If polymer electrolyte is used instead of liquid electrolyte, then safety is improved, but ionic conductivity deteriorates
Solution Approach 1:
The patent modifies the parameters of polymer electrolyte by incorporating specific additives and creating a crosslinked heterogeneous network structure. These parameter changes optimize the polymer matrix to achieve sufficient ionic conductivity while maintaining the safety advantages of solid polymer electrolytes
Solution Approach 2:
The patent creates a composite polymer electrolyte system combining base polymer with functional additives (LiBF4, LiPF6, lithium difluorophosphate, lithium fluorophosphate). This composite structure provides pathways for ion transport, enhancing conductivity while the polymer matrix maintains safety, thus resolving the contradiction 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 crosslinked polymer electrolytes demonstrate increased cycle retention and ionic conductivity, leading to safer and longer-life lithium batteries with higher voltage stability, addressing the safety concerns and performance limitations of conventional lithium-ion batteries.
Implementation Method 1
a crosslinked polymer with a heterogeneous polymer network synthesized from one or more crosslinkers, wherein at least one crosslinker has three or more polymerizable terminals
Data Source
AI summary
A polymer electrolyte includes an additive and a crosslinked polymer with a heterogeneous polymer network synthesized from one or more crosslinkers, wherein at least one crosslinker has three or more polymerizable terminals. In another embodiment, the crosslinked polymer has a polymer network with topological defects. In some embodiments, the additive comprises element F and at least one of elements B and P. In some embodiments, the additive comprises F—B, F—P, F—P—O, F—P=O, or any combinations thereof. In one embodiment, the crosslinked polymer is not over-crosslinked. An electrochemical device with the crosslinked polymer as electrolyte exhibits an improved electrochemical and safety performance.