Solid Polymer Electrolyte for Lithium Ion Battery Safety
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current lithium-ion batteries with silicon anodes and sulfur cathodes face issues such as rapid capacity fading, poor cycle life, and safety concerns due to the 'shuttle effect' of polysulfides and large volume changes in silicon, leading to inefficiencies and potential hazards from volatile organic solvents.
Innovation Solution
A solid polymer electrolyte composed of functionalized poly(ethylene glycol), a lithium salt, an ionic liquid, and graphene oxide is used to provide superior battery performance by facilitating Li-ion transport, preventing polysulfide dissolution, and forming a stable solid electrolyte interface, while also addressing safety concerns by eliminating flammable organic solvents and accommodating electrode volume changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If liquid electrolytes are used in lithium-ion batteries, then ionic conductivity is maintained, but polysulfide dissolution and shuttle effect occur leading to rapid capacity fading
Solution Approach 1:
The patent changes the physical state of the electrolyte from liquid to solid by using a polymer electrolyte membrane. This parameter change prevents polysulfide dissolution while maintaining ionic conductivity, thereby eliminating the shuttle effect and improving cycle life without significant capacity fading.
Solution Approach 2:
The polymer electrolyte membrane acts as an intermediary between the electrodes, selectively allowing lithium ion transport while blocking polysulfide species. This mediator function prevents direct contact between polysulfides and the electrolyte, stopping the harmful shuttle effect.
2Quantity of substance
If silicon anodes are used to increase capacity, then energy density improves, but large volume change causes fractures and SEI layer instability
Solution Approach 1:
The patent employs a flexible polymer electrolyte membrane that can accommodate the large volume changes of silicon anodes during lithiation and delithiation. The membrane's flexibility prevents fracture of the silicon structure and maintains stable contact, avoiding SEI layer breakdown while preserving high capacity.
Solution Approach 2:
The polymer electrolyte membrane provides beforehand cushioning by absorbing and distributing the mechanical stress generated during silicon volume expansion. This pre-established protective mechanism prevents structural failure before it occurs, maintaining electrode integrity throughout cycling.
3Quantity of substance
If sulfur cathodes are used to increase capacity, then energy density improves, but electronic conductivity remains low leading to inefficiencies
Solution Approach 1:
The patent creates a composite structure where sulfur is integrated with conductive materials within the polymer electrolyte membrane architecture. This composite approach maintains the high capacity of sulfur while improving electronic conductivity through the conductive network, reducing energy losses.
4Productivity
If volatile organic solvent electrolytes are used, then ionic conductivity is maintained, but safety hazards increase due to flammability
Solution Approach 1:
The patent changes the chemical composition and physical state of the electrolyte from volatile organic liquid to non-volatile solid polymer. This parameter change eliminates flammability and volatility while maintaining ionic conductivity through the polymer matrix, thereby removing safety hazards associated with traditional electrolytes.
Solution Approach 2:
The polymer electrolyte membrane creates an inert environment within the battery by replacing flammable organic solvents with a non-flammable solid polymer matrix. This inert environment prevents combustion reactions even under thermal runaway conditions, significantly improving battery safety.
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 enhances the energy density and cycle life of lithium-ion batteries, improves safety by eliminating volatile solvents, and maintains high ionic conductivity, effectively addressing the limitations of silicon anode and sulfur cathode chemistries.
Implementation Method 1
facilitating Li-ion transport
Implementation Method 2
forming a stable solid electrolyte interface
Data Source
AI summary
Features for rechargeable lithium ion batteries, the batteries optionally employing vertically aligned carbon nanotube scaffolding, are described. Methods of manufacture and a solid polymer electrolyte are described for 3-dimensional battery architectures using the vertically aligned carbon nanotubes. Poly(ethylene)oxide bis(azide) and graphene poly(lactic acid) composite coatings are also described for use in such batteries or others.