Supplemental Lithium Stabilizes Li-Ion Batteries
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Solution Overview
Problem
Lithium ion batteries face significant capacity fading due to irreversible changes in the positive electrode active material, leading to reduced cycling performance and stability, especially at high voltages, where the positive electrode's ability to incorporate lithium is compromised, resulting in decreased energy and power delivery over time.
Innovation Solution
Incorporating supplemental lithium into the negative electrode, either through elemental lithium, a sacrificial lithium source, or preloading lithium into the negative electrode active material, which stabilizes the positive electrode active material and reduces transition metal dissolution into the electrolyte, thereby maintaining high specific capacities and cycling stability over numerous cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If lithium ion batteries operate at high voltages to increase energy density, then power delivery is improved, but the positive electrode active material undergoes irreversible changes leading to capacity fading and reduced cycling stability
Solution Approach 1:
The patent applies preliminary action by pre-loading the negative electrode with supplemental lithium before the battery enters service. This preliminary lithium is deposited during manufacturing or initial cycles, creating a reservoir that compensates for future lithium loss from positive electrode degradation. The supplemental lithium is introduced in advance to prevent capacity fading before it occurs during normal operation.
Solution Approach 2:
The patent changes the lithium content parameter in the negative electrode by adding supplemental lithium beyond what would be present from standard balancing. This parameter change creates a lithium excess condition that stabilizes the positive electrode and maintains capacity over extended cycling at high voltages, directly addressing the reliability issue while preserving power delivery capability.
2Quantity of substance
If the positive electrode is designed for high capacity to increase energy density, then energy storage is improved, but the positive electrode's ability to incorporate lithium reversibly deteriorates over time
Solution Approach 1:
The supplemental lithium in the negative electrode serves a self-service function by automatically compensating for lithium loss from the positive electrode over time. As the positive electrode degrades and loses lithium during cycling, the supplemental lithium reservoir releases lithium to maintain charge balance, effectively self-healing the system without external intervention and maintaining stable lithium incorporation capability.
3Device complexity
If conventional lithium ion battery design is used to maintain simplicity, then device complexity is low, but capacity fading occurs due to irreversible positive electrode changes
Solution Approach 1:
The patent merges the supplemental lithium source directly into the negative electrode structure, combining the functions of the negative electrode active material and the lithium reservoir into a single integrated component. This merging approach maintains simplicity in the overall battery structure while achieving the productivity benefit of enhanced cycling performance through the combined lithium storage and stabilization functions.
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 addition of supplemental lithium significantly enhances the cycling stability and specific discharge capacity of lithium ion batteries, maintaining at least 92.5% of the initial capacity after 200 cycles at room temperature and 75% after 175 cycles at elevated temperatures, with minimal capacity fade even at high voltage operations.
Implementation Method 1
a negative electrode material that intercalates lithium or alloys with lithium
Implementation Method 2
a negative electrode material that intercalates lithium or alloys with lithium
Implementation Method 3
an electrolyte comprising lithium ions
Data Source
AI summary
Supplemental lithium can be used to stabilize lithium ion batteries with lithium rich metal oxides as the positive electrode active material. Dramatic improvements in the specific capacity at long cycling have been obtained. The supplemental lithium can be provided with the negative electrode, or alternatively as a sacrificial material that is subsequently driven into the negative electrode active material. The supplemental lithium can be provided to the negative electrode active material prior to assembly of the battery using electrochemical deposition. The positive electrode active materials can comprise a layered-layered structure comprising manganese as well as nickel and/or cobalt.