Polymeric Chelating Agent for Lithium Ion Battery Separators
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Solution Overview
Problem
Lithium ion batteries face accelerated capacity fading and durability issues due to the dissolution of transition metal cations from the positive electrode, which migrate to the negative electrode and cause 'poisoning', leading to reduced battery life, especially at elevated temperatures.
Innovation Solution
Incorporating a polymeric chelating agent, specifically a poly(undecylenyl-macrocycle), into the lithium ion battery separator or positive electrode to trap unwanted metal cations, preventing their migration and maintaining lithium ion passage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional separator is used, then lithium ion passage is maintained, but transition metal cations dissolve and migrate causing capacity fading
Solution Approach 1:
A polymeric chelating agent is introduced as an intermediary substance between the positive and negative electrodes. This agent selectively binds to transition metal cations (such as Mn²⁺, Co²⁺, Ni²⁺) that dissolve from the positive electrode, preventing their migration to the negative electrode. The chelating agent acts as a mediator that captures harmful cations while allowing lithium ions to pass through, thereby resolving the contradiction between maintaining ion transport and preventing cation dissolution.
Solution Approach 2:
The invention converts the harmful effect of transition metal cation dissolution into a beneficial outcome by using the chelating agent to selectively bind these cations. Instead of allowing the cations to migrate and poison the negative electrode (harmful effect), the chelating agent captures them and transports them to the positive electrode where they are redeposited (beneficial effect). This transforms the capacity-fading mechanism into a protective cycle that actually removes harmful cations from the electrolyte.
2Reliability
If the separator structure is modified to prevent cation migration, then durability improves, but lithium ion flow may be blocked
Solution Approach 1:
The polymeric chelating agent is incorporated into the separator at specific locations and concentrations to provide selective cation binding. The separator maintains its overall porous structure for lithium ion transport, but localized regions contain the chelating polymer that selectively interacts with transition metal cations. This local modification allows the separator to simultaneously maintain high lithium ion conductivity while providing targeted protection against cation dissolution.
Solution Approach 2:
The invention changes the chemical parameters of the separator by incorporating functional groups with high affinity for transition metal cations. The chelating polymer introduces specific chemical properties (chelation capability) to the separator material, enabling it to selectively bind cations based on their chemical characteristics rather than physically blocking them. This parameter change allows differentiation between lithium ions (which pass through) and transition metal cations (which are bound).
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 polymeric chelating agent effectively immobilizes transition metal cations, enhancing battery durability and maintaining lithium ion flow, thereby reducing capacity fading and extending battery life even at elevated temperatures.
Implementation Method 1
The polymeric chelating agent includes a poly(undecylenyl-macrocycle), where the macrocycle is a chelating agent
Data Source
AI summary
A lithium ion battery separator includes a porous film of a polymeric chelating agent. The polymeric chelating agent includes a poly(undecylenyl-macrocycle), where the macrocycle is a chelating agent. A positive electrode includes a structure and a coating formed on a surface of the structure. The structure includes a lithium transition metal based active material, a binder, and a conductive carbon; and the coating includes a poly(undecylenyl-macrocycle), where the macrocycle is a chelating agent. The separator and/or positive electrode are suitable for use in a lithium ion battery.