Doped Lithium-Rich Cathode Material Against Layered-to-Spinel Transition
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Solution Overview
Problem
Layered lithium and manganese-rich oxides (LMR) used in electrochemical cells suffer from voltage decay, low coulombic efficiency, and irreversible capacity loss due to an irreversible phase transition from a layered structure to a spinel structure during lithium removal, impeding lithium ion diffusion.
Innovation Solution
Doping LMR with alkali metals and/or alkaline earth metals to inhibit the formation of spinel phases by replacing lithium ions in the layered structure, maintaining the layered structure and enhancing electrochemical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If LMR undergoes phase transition from layered structure to spinel structure during charging, then lithium ions can be removed, but electrochemical performance degrades due to poor spinel phase performance and impeded lithium ion diffusion
Solution Approach 1:
The patent applies preliminary anti-action by doping LMR with alkali metals and alkaline earth metals before electrochemical cycling begins. These dopant elements preemptively occupy sites that would otherwise facilitate the harmful layered-to-spinel phase transformation during charging, thereby preventing the performance degradation that would normally occur when lithium ions are removed.
Solution Approach 2:
The patent changes the chemical composition parameters of LMR by introducing dopant elements (alkali metals and alkaline earth metals) at controlled concentrations. This parameter change modifies the crystal structure stability, raising the voltage threshold required for phase transformation and thereby maintaining the layered structure during electrochemical cycling, which preserves lithium ion diffusion pathways and electrochemical performance.
2Quantity of substance
If LMR is used as positive electrode material, then high capacity (>250 mAh/g) and thermal stability are achieved, but voltage decay and irreversible capacity loss occur after repeated cycling
Solution Approach 1:
The patent applies preliminary action by incorporating dopant elements into the LMR crystal structure before the material is put into service. This preliminary doping action creates a more stable crystal structure that resists phase transformations during cycling, thereby preventing voltage decay and irreversible capacity loss that would otherwise accumulate over repeated charge-discharge cycles.
Solution Approach 2:
The patent creates a composite material by combining LMR with dopant elements (alkali metals and alkaline earth metals). This composite structure leverages the high capacity and thermal stability of LMR while the dopant elements provide structural stabilization, resulting in a material that maintains both high capacity and improved cycle stability through synergistic effects.
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 doped-LMR materials exhibit improved capacity retention and electrochemical performance by preventing phase transformation during cycling, thus maintaining high capacity and efficiency.
Implementation Method 1
Doping LMR with alkali metals and/or alkaline earth metals to inhibit the formation of spinel phases by replacing lithium ions in the layered structure
Implementation Method 2
The doped-LMR materials exhibit improved capacity retention and electrochemical performance by preventing phase transformation during cycling, thus maintaining high capacity and efficiency
Data Source
AI summary
A positive electrode material including a layered lithium- and manganese-rich nickel oxide (LMR) doped with an alkali metal and/or an alkaline earth metal. The positive electrode material may be manufactured by preparing a mixture comprising a transition metal carbonate, a dopant metal carbonate, and a lithium source, and then calcining the mixture to form the alkali metal and/or alkaline earth metal-doped LMR.