Lithium Metal Polymer Battery Block Copolymer Electrolyte
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Solution Overview
Problem
Lithium Metal Polymer (LMP) batteries face limitations in energy density and cycling stability due to the crystalline structure of poly(ethylene oxide) (PEO)-based solid polymer electrolytes, which restricts ionic conductivity and mechanical strength, leading to salt depletion, increased resistance, and dendrite formation.
Innovation Solution
A high energy density LMP battery is developed using a positive electrode with a high Li+ ion insertion/deinsertion potential, combined with a block copolymer electrolyte that includes a diblock or triblock copolymer with an unsubstituted polyoxyethylene chain and an anionic polymer capable of being prepared from lithium sulfonyl(trifluoromethylsulfonyl)imide, along with reinforcing agents like cellulose nanofibrils or ceramic nanoparticles, to enhance mechanical strength and ionic conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PEO-based solid polymer electrolyte is used, then ionic conductivity is improved, but mechanical strength deteriorates at operating temperatures
Solution Approach 1:
The patent uses a block copolymer consisting of a PEO block and a glassy polymer block. The PEO block provides ionic conductivity while the glassy polymer block provides mechanical strength. This composite structure at the molecular level allows both functions to coexist within a single material system, resolving the contradiction between ionic conductivity and mechanical strength.
2Strength
If crystalline structure of PEO is maintained, then mechanical strength is improved, but ionic conductivity deteriorates
Solution Approach 1:
The patent segments the polymer chain into distinct blocks: a PEO block responsible for ionic conductivity and a glassy polymer block responsible for mechanical strength. This segmentation allows each block to perform its specific function without interfering with the other, enabling the material to achieve both high ionic conductivity and mechanical strength simultaneously.
3Use of energy by moving object
If high potential positive electrode active material is used, then energy density is improved, but electrochemical stability deteriorates
Solution Approach 1:
The block copolymer electrolyte acts as a stable interface material between the high potential cathode and lithium anode. The glassy polymer block provides electrochemical stability while the PEO block enables ionic transport, allowing the system to utilize high potential materials for increased energy density without sacrificing stability.
4Strength
If PEO molecular weight is increased, then mechanical properties are improved, but ionic conductivity deteriorates
Solution Approach 1:
Instead of increasing PEO molecular weight which would improve mechanics but reduce conductivity, the patent segments the polymer into separate blocks. The glassy polymer block is specifically designed to provide mechanical properties, while the PEO block maintains optimal molecular weight for ionic conductivity. This segmentation eliminates the trade-off present in homopolymer systems.
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 solution achieves improved power density and cycling stability, allowing the battery to perform many cycles at high voltages without capacity drop, while preventing dendrite nucleation and maintaining electrochemical stability.
Implementation Method 1
The conductivity of the ions is ensured by the dissolving of the lithium salt in the poly(ethylene oxide)
Implementation Method 2
the lithium salt is dissolved in a PEO polymer matrix
Data Source
AI summary
The present invention relates to a high energy density lithium metal polymer (LMP) battery comprising a positive electrode that includes a high potential positive electrode active material and a block copolymer of AB or BAB type, A being an ethylene oxide block and B being an anionic polymer block based on lithium bis(trifluoromethylsulfonyl)imide.