Lithium Polysalt Binders for Electrode Adhesion and Capacity Loss
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Solution Overview
Problem
Lithium-ion batteries experience high irreversible capacity loss and capacity fade due to the use of conventional polymeric binders in electrodes, leading to reduced performance and safety concerns.
Innovation Solution
The development of novel electrode compositions using lithium polyacrylate and other lithium polysalt binders, such as poly(ethylene-alt-maleic acid) lithium salt and poly(methyl vinyl ether-maleic acid) lithium salt, which provide improved adhesion and conductivity, reducing irreversible capacity loss and capacity fade.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polymeric binders (polyvinylidene fluoride, aromatic and aliphatic polyimides, polyacrylates) are used in electrode compositions, then the electrode structure is maintained and adhesion is provided, but irreversible capacity loss is unacceptably large (300 mAh/g or more)
Solution Approach 1:
The invention changes the chemical composition parameter of the binder from conventional polymeric binders to lithium polysalt binders (lithium polyacrylate, poly(ethylene-alt-maleic acid) lithium salt, poly(methyl vinyl ether-maleic acid) lithium salt). This parameter change fundamentally alters the binder's interaction with lithium ions, reducing irreversible capacity loss from 300 mAh/g or more to significantly lower values while maintaining electrode structural integrity.
2Duration of action of stationary object
If conventional polymeric binders are used, then electrode assembly is simplified, but capacity fade increases after multiple cycles due to morphology changes and insulating layer buildup
Solution Approach 1:
The invention changes the binder composition from conventional polymeric binders to lithium polysalt binders, which fundamentally alter the electrochemical behavior during cycling. This parameter change prevents capacity fade by avoiding insulating layer buildup and morphology degradation, extending the electrode's operational lifetime through multiple charge-discharge cycles.
3Reliability
If excess lithium ions are present in the positive electrode to enable initial charging, then complete lithiation of the negative electrode is achieved, but irreversible capacity loss occurs as lithium ions cannot migrate back to the positive electrode
Solution Approach 1:
The lithium polysalt binder acts as an intermediary that facilitates reversible lithium ion migration between electrodes. The binder's lithium ions serve as a reservoir that can reversibly exchange with lithium ions from the electrolyte, enabling complete lithiation of the negative electrode during charging while ensuring lithium ions can migrate back to the positive electrode during discharge, eliminating irreversible capacity loss.
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 use of these novel binders results in electrodes with significantly reduced irreversible capacity loss and improved cycle life, enhancing the performance and safety of lithium-ion cells.
Implementation Method 1
The mixed ingredients are prepared as a dispersion in a solvent for the polymeric binder, and coated onto a metal foil substrate, or current collector. The resulting composite electrode contains the powdered active ingredient in the binder adhered to the metal substrate.
Implementation Method 2
During the initial cycling reaction of the cells (charging), lithium transfers from the positive electrode to the negative electrode until the negative electrode has reached its capacity of absorbing lithium ions.
Implementation Method 3
Upon the first discharge, the lithium ions migrate from the lithiated negative electrode back to the positive electrode.
Data Source
AI summary
Provided are electrode compositions for lithium-ion electrochemical cells that include novel binders. The novel binders include lithium polysalts of carboxylic and sulfonic acids, lithium salts of copolymers of acids, lithium polysulfonate fluoropolymers, a cured phenolic resin, cured glucose, and combinations thereof.