Pre-Lithiated Cathode Coating for First-Cycle Efficiency Stability
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Solution Overview
Problem
Existing lithium ion batteries face issues with low first-cycle Coulombic efficiency due to solid-electrolyte interphase (SEI) formation on silicon-based anodes, which consumes significant lithium ions, and previous attempts to use sacrificial lithium sources at the cathode have been hindered by reactivity with electrolytic components and poor reversibility.
Innovation Solution
A cathode configuration is developed with a lithium mixed metal oxide core coated by a sacrificial lithium source, such as lithium peroxide, and optionally an active cathode catalyst, protected by a passivating layer to mitigate performance degradation from impurities and electrolytic components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sacrificial lithium source is added to the cathode to provide extra lithium ions to the anode, then the first-cycle Coulombic efficiency is improved, but the sacrificial lithium source reacts with electrolytic components causing performance degradation
Solution Approach 1:
A passivating layer is applied to the sacrificial lithium source before it contacts the electrolyte, preventing harmful reactions in advance. This coating acts as a protective barrier that blocks direct interaction between the reactive lithium source and electrolytic components while still allowing lithium ion release when needed.
Solution Approach 2:
The passivating layer serves as an intermediary between the sacrificial lithium source and the electrolyte. It mediates the interaction by allowing beneficial lithium ion transfer while blocking harmful chemical reactions, thus protecting the system without preventing the desired function.
2Quantity of substance
If a sacrificial lithium source is used to compensate for anode lithium ion loss, then capacity is improved, but reversibility deteriorates due to poor cycling performance
Solution Approach 1:
The passivating layer prevents premature or irreversible reactions between the sacrificial lithium source and the electrolyte or moisture, preserving the lithium source for controlled, reversible release during battery cycling. This preliminary protection ensures the lithium source remains available for beneficial reactions.
Solution Approach 2:
The passivating layer creates an inert protective environment around the sacrificial lithium source, isolating it from reactive species in the electrolyte and moisture. This inert barrier allows the lithium source to remain stable and reversible until intentionally activated during normal battery operation.
3Ease of manufacture
If the sacrificial lithium source is exposed to air and moisture, then lithium hydroxide and lithium carbonate are generated, but electrochemical performance deteriorates due to inactive residues
Solution Approach 1:
The passivating layer is applied during manufacturing to prevent unwanted reactions with air and moisture before the battery is sealed. This preliminary protective action prevents the formation of inactive residues like lithium hydroxide and lithium carbonate that would degrade electrochemical performance.
Solution Approach 2:
The passivating layer extracts or removes the harmful reactivity of the sacrificial lithium source from the system environment. By taking out the problematic interaction between the lithium source and atmospheric moisture/air, the layer prevents residue formation while maintaining manufacturing simplicity.
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 first-cycle efficiency and stability of lithium ion batteries by providing additional lithium ions to the anode while protecting the sacrificial source, maintaining performance over multiple cycles.
Implementation Method 1
a cathode catalyst (CC), such as a Li-based active CC (ACC), may further be incorporated to both lower the potential and increase the rate of decomposition of the sacrificial Li source
Implementation Method 2
protected by a passivating layer to mitigate performance degradation from impurities and electrolytic components
Data Source
AI summary
Methods and systems are provided for a cathode material for lithium ion batteries. In one example, the cathode material may include a lithium mixed metal oxide core and a surface coating surrounding the core. Optionally, a passivating layer may continuously surround the surface coating. In some examples, the surface coating or surface layer may include a sacrificial lithium source, a lithium-based active cathode catalyst, or a combination thereof. In other examples, methods are provided for manufacturing the cathode material for use in a lithium ion battery.