Copolymer Polymer Electrolyte for Room-Temperature High-Voltage Batteries
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Solution Overview
Problem
Lithium secondary batteries face challenges due to the high crystallinity of polyethylene oxide (PEO) at room temperature, leading to low ionic conductivity and instability at higher voltages, which limits their application in high-voltage lithium battery applications.
Innovation Solution
A polymer electrolyte is developed using a copolymer with alkylene oxide repeating units in both the main and side chains, reducing crystallinity and incorporating ester groups and halogen atoms for improved oxidation resistance, allowing for enhanced ionic conductivity and stability at higher voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyethylene oxide (PEO) is used as polymer electrolyte, then ionic conductivity is improved at high temperature, but crystallinity increases at room temperature causing low ionic conductivity
Solution Approach 1:
The patent uses a copolymer combining PEO units with PPO (polypropylene oxide) units to create a composite polymer structure. The PPO units interrupt the crystalline packing of PEO, reducing overall crystallinity while maintaining ionic conductivity pathways. This composite approach allows the electrolyte to function at room temperature without requiring external heating.
Solution Approach 2:
The patent modifies the chemical composition parameters of the polymer by incorporating different mole ratios of PEO and PPO units. By adjusting these compositional parameters, the patent optimizes the balance between crystallinity and ionic conductivity, enabling room-temperature operation with sufficient ionic transport properties.
2Quantity of substance
If PEO is used for high-voltage lithium battery applications, then capacity is improved, but oxidation stability deteriorates at voltages above 3.8 V
Solution Approach 1:
The copolymer structure combines PEO segments (which provide ionic conductivity and lithium solvation) with PPO segments (which offer oxidation resistance). This composite material approach allows the electrolyte to withstand higher voltages without oxidation while maintaining adequate ionic transport for high-capacity battery operation.
Solution Approach 2:
The patent creates local regions with different chemical properties within the polymer chain. The PPO units provide localized oxidation resistance at the polymer-electrode interface, while the PEO units maintain ionic conductivity in the bulk. This spatial differentiation of functional properties allows simultaneous achievement of high voltage stability and high capacity.
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 exhibits improved ionic conductivity and high-voltage stability, enabling its use in lithium batteries without the need for additional heating, thus enhancing the performance and reliability of lithium secondary batteries.
Implementation Method 1
PEO has a low ionic conductivity due to high crystallinity at room temperature... The copolymer includes a first repeating unit and a second repeating unit... reducing crystallinity
Implementation Method 2
incorporating ester groups and halogen atoms for improved oxidation resistance... PEO is oxidized at a high voltage of about 3.8 V (vs. Li), but the copolymer maintains stability at higher voltages
Implementation Method 3
The polymer electrolyte exhibits improved ionic conductivity... The copolymer includes alkylene oxide repeating units in both the main and side chains, reducing crystallinity and incorporating ester groups and halogen atoms for improved oxidation resistance
Data Source
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AI summary
A polymer electrolyte including a copolymer represented by Formula 1; and a lithium salt: wherein, in Formula 1, R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, R15, R16, R17, L1, n1, x, y, and z are as disclosed herein.