Crosslinked Block Copolymer Electrolyte for Lithium Batteries
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Solution Overview
Problem
Lithium batteries with metallic lithium anodes face issues with dendrite growth due to uneven lithium ion re-deposition, leading to mechanical instability and reduced performance, as existing solid polymer electrolytes either lack sufficient mechanical resistance or ionic conductivity.
Innovation Solution
A crosslinked block copolymer electrolyte with a diblock or triblock structure, featuring a polyethylene oxide chain and an anionic polymer grafted with lithium salt and cross-linkable polyfunctional monomers, enhancing both mechanical strength and ionic conductivity by allowing post-polymerization cross-linking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high molecular weight PEO is used to improve mechanical properties, then mechanical strength increases, but ionic conductivity decreases due to crystalline structure
Solution Approach 1:
The patent applies segmentation by creating a block copolymer structure with distinct micro-domains: crystalline PEO blocks (10-50 kDa) for mechanical strength and amorphous PEO blocks for ionic conductivity. This segmentation allows each block to fulfill its specific function without compromising the other, resolving the contradiction between mechanical strength and ionic conductivity.
Solution Approach 2:
The patent uses composite materials by combining PEO blocks with inorganic filler particles (such as Al2O3, SiO2, or TiO2) to create a composite electrolyte. The inorganic fillers enhance mechanical properties and thermal stability while the PEO matrix maintains ionic conductivity, thus resolving the contradiction between strength and conductivity.
2Reliability
If PEO is heated above melting point to increase ionic conductivity, then ionic conductivity increases, but dimensional stability is lost as PEO becomes viscous liquid
Solution Approach 1:
The patent exploits phase transitions by designing a block copolymer where PEO blocks undergo controlled crystallization at operating temperatures. The crystalline PEO domains provide dimensional stability while the amorphous domains maintain ionic conductivity. The block structure allows the material to utilize the solid-crystalline phase for stability and the liquid-amorphous phase for conductivity without requiring external heating.
Solution Approach 2:
The patent employs composite materials by incorporating inorganic fillers into the PEO matrix. These fillers provide thermal stability and maintain the electrolyte's dimensional integrity at elevated temperatures while the PEO phase transitions continue to facilitate ionic conduction, thus resolving the contradiction between conductivity and stability.
3Strength
If crosslinking is performed to improve mechanical strength, then mechanical resistance increases, but ionic conductivity decreases
Solution Approach 1:
The patent applies segmentation by localizing crosslinking to specific regions of the block copolymer structure. Crosslinks are formed primarily in the amorphous PEO blocks or at the interfaces between blocks, while the crystalline PEO blocks remain uncrosslinked to maintain their ability to provide mechanical strength and structural organization. This selective crosslinking preserves ionic conductivity pathways while enhancing mechanical resistance.
4Reliability
If additional lithium salt is added to improve ionic conductivity, then ionic conductivity increases, but mechanical properties deteriorate
Solution Approach 1:
The patent applies the taking out principle by extracting the lithium salt from the bulk polymer matrix and concentrating it in specific micro-domains, such as the amorphous PEO blocks or at the interface with inorganic fillers. This localized concentration of lithium salt enhances ionic conductivity in the conductive pathways while minimizing the disruption to the overall polymer matrix structure, thus preserving mechanical properties.
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 effectively inhibits dendrite growth, providing improved mechanical resistance and ionic conductivity, leading to enhanced battery performance and stability, with the potential for thinner, more durable electrolyte films that maintain high energy density.
Implementation Method 1
cross-linkable polyfunctional monomers having chemical functions R1 and/or R2 that did not participate in the initial polymerization reaction that can be post-reacted for cross-linking
Implementation Method 2
block A is an unsubstituted polyethylene oxide chain... improving the electrochemical performance by increasing the Li ions transport number
Data Source
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AI summary
A solid polymer electrolyte for a battery is disclosed. The solid polymer electrolyte includes solid polymer electrolyte including a diblock copolymer AB or a triblock copolymer of the BAB type, in which block A is an unsubstituted polyethylene oxide chain having a number- average molecular weight less than 80,000 g/mol; block B is an anionic polymer prepared from one or more monomers selected from vinyl monomers and derivatives thereof to which is grafted an anion of lithium salt, and a second monomer having cross-linking functions.