Li-Excess Disordered Rocksalt Cathodes for Stable High-Capacity Cycling
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Solution Overview
Problem
Existing disordered rocksalt cathode materials for lithium-ion batteries face challenges in achieving high specific capacity and energy while maintaining superior cycle life due to issues like oxygen redox, transition metal dissolution, and phase separation, which degrade the 3D percolating network and Li ion kinetics.
Innovation Solution
Development of Group I metal cation excess cathode materials with specific compositions and manufacturing processes, including ball milling and calcination, to enhance redox active transition metal content and improve cycling stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If high-valent transition metals are used as charge compensators to achieve high specific capacity, then the material-level specific capacity and energy increase, but the redox active transition metal content decreases
Solution Approach 1:
The patent changes the chemical composition parameters by using lower-valent transition metals (Mn3+, Fe2+, Co2+, Ni2+) instead of high-valent metals, and adjusts the Li excess stoichiometry to optimize the balance between capacity and redox activity. This parameter change allows maintaining high specific capacity while preserving sufficient redox active metal content for stable cycling.
2Speed
If Li-excess environments are created to form 3D percolating pathways for efficient Li ion transport, then Li ion kinetics improve, but oxygen redox activity increases leading to structural deterioration
Solution Approach 1:
The patent converts the harmful oxygen redox activity into a beneficial mechanism by utilizing transition metal redox couples (Mn3+/Mn4+, Fe2+/Fe3+, Co2+/Co3+) that operate at similar voltage ranges. This substitution maintains the electrochemical performance while avoiding the structural degradation caused by oxygen loss, effectively turning the problem of high Li-excess into a benefit for stabilizing the disordered rocksalt structure.
3Reliability
If transition metal dissolution and phase separation are suppressed to maintain 3D percolating network, then cycling stability improves, but capacity may be limited
Solution Approach 1:
The patent employs composite cathode materials with multi-element transition metal compositions (e.g., Li2Mn0.5Fe0.25Co0.25O2.96F0.04) that combine multiple redox-active metals with complementary properties. This composite approach enhances structural stability through synergistic effects, preventing dissolution and phase separation while maintaining high capacity through combined redox contributions from all metal centers.
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 new cathode materials exhibit high specific capacity and energy with improved cycle life, maintaining efficient Li ion transport and reducing reliance on oxygen redox, thus enhancing the performance of lithium-ion batteries.
Implementation Method 1
the Li-excess environments in DRX enable efficient Li ion transport in three-dimensional (3D) percolating pathways
Implementation Method 2
at least one of the at least two different non-Group I metal cations has a redox reaction within a voltage window of about 1.5 V to about 5.0 V vs Li/Li+
Implementation Method 3
including ball milling and calcination
Implementation Method 4
including ball milling and calcination
Data Source
AI summary
A Group I metal cation excess cathode material comprising a Group I metal cation, at least two different non-Group I metal cations, and at least one counterion is disclosed. It is disclosed that the Group I metal cation excess cathode material delivers high capacity, rate capability, as well as long cycle life upon extensive 1,000 cycles at various current densities.