Pre-Lithiated Cathode Coating for First-Cycle Efficiency
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Solution Overview
Problem
Lithium ion batteries face challenges with low first-cycle Coulombic efficiency due to solid-electrolyte interphase formation on silicon-based anodes, and existing sacrificial lithium sources suffer from performance degradation and reversibility issues.
Innovation Solution
A cathode material configuration using lithium mixed metal oxide core particles coated with a sacrificial lithium source, such as lithium peroxide, and an active cathode catalyst, optionally with a passivating layer to protect from impurities and electrolytic components, is developed to enhance lithium ion availability and battery performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sacrificial lithium source is added to the cathode to provide extra lithium ions during initial charging, then the first-cycle Coulombic efficiency is improved, but the cathode material undergoes structural changes and performance degradation
Solution Approach 1:
The cathode is segmented into multiple functional components: a core positive electrode active material, a sacrificial lithium source coating, and a cathode catalyst coating. This segmentation allows each component to perform its specific function independently - the core provides stable structure, the sacrificial source provides lithium ions, and the catalyst facilitates decomposition - thereby improving first-cycle Coulombic efficiency while maintaining overall cathode stability
Solution Approach 2:
The sacrificial lithium source is pre-coated onto the cathode material surface before battery assembly. This preliminary action ensures that lithium ions are readily available during the first charge cycle to compensate for anode SEI formation, improving first-cycle Coulombic efficiency without requiring structural changes to the core cathode material
2Speed
If a cathode catalyst is used to lower the potential and increase the rate of decomposition of the sacrificial lithium source, then the lithium ion release rate is improved, but the voltage profile of the catalyst changes indicating structural modification
Solution Approach 1:
The cathode catalyst is applied as a thin surface coating (1-10 nm) on the cathode particles. This local quality approach concentrates the catalytic activity at the surface where the sacrificial lithium source decomposes, accelerating lithium ion release without requiring bulk structural changes to the catalyst that would compromise its stability and voltage profile
3Quantity of substance
If high nickel content positive electrode active materials are used to achieve high energy density, then the capacity is improved, but the cathode becomes more susceptible to degradation and safety issues
Solution Approach 1:
The cathode is designed as a composite structure combining high nickel content positive electrode active material (providing high capacity) with a sacrificial lithium source coating and cathode catalyst coating. This composite structure allows the core to deliver high energy density while the coatings provide protective and functional properties that enhance stability and safety, mitigating the inherent vulnerabilities of high nickel materials
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 improves the first-cycle efficiency and cycling stability of lithium ion batteries by providing a controlled release of lithium ions and protecting the cathode from degradation, leading to increased capacity and safety.
Implementation Method 1
a sacrificial Li source may be added to the cathode such that an increased amount of Li ions may flow to the anode during initial charging
Implementation Method 2
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 3
The SEI may prove detrimental to electrochemical performance as the formation process results in significant Li ion consumption
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.