Lithium-Rich Manganese Cathode Co-Doping for High-Voltage Stability
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Solution Overview
Problem
Lithium-rich manganese-based materials exhibit poor rate performance, instability, and low electronic and ionic conductivity due to oxygen vacancies and side reactions at high voltages, leading to reduced efficiency and cycle life.
Innovation Solution
A modified lithium-rich manganese-based material is developed by co-doping with specific anion and cation elements and coating with a fast ionic conductor material, such as LATP, to stabilize the crystal structure, reduce oxygen loss, and enhance ionic conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium-rich manganese-based material is used as positive electrode material, then high energy density and high discharge specific capacity are achieved, but poor rate performance and low ionic conductivity occur
Solution Approach 1:
A fast ionic conductor coating layer is introduced as an intermediary between the lithium-rich manganese-based material and the electrolyte. This coating layer mediates the interaction by providing high ionic conductivity pathways while isolating the bulk material from direct contact with the electrolyte, thus improving rate performance without sacrificing energy density
Solution Approach 2:
The ionic conductivity parameter of the positive electrode material is changed by applying a fast ionic conductor coating with significantly higher ionic conductivity than the bulk material. This parameter change enables faster lithium ion transport at the surface, improving rate performance while maintaining the high capacity characteristics of the lithium-rich manganese-based material
2Use of energy by moving object
If high voltage charging state above 4.5 V is achieved in the first cycle, then high energy density is obtained, but oxygen loss and crystal structure instability occur
Solution Approach 1:
The fast ionic conductor coating is applied in advance to prevent oxygen loss and crystal structure instability before they can occur during high voltage charging. The coating acts as a protective barrier that preemptively counteracts the harmful effects of high voltage operation, allowing the material to reach high energy density states without suffering from oxygen evolution or structural degradation
Solution Approach 2:
The fast ionic conductor coating creates an inert environment around the lithium-rich manganese-based material, isolating it from the electrolyte and preventing side reactions. This inert barrier allows the material to operate at high voltages above 4.5 V without experiencing oxygen loss or crystal structure rearrangement, thereby maintaining both high energy density and cycle stability
3Use of energy by moving object
If lithium-rich manganese-based material operates at high voltage, then high energy density is achieved, but side reactions with electrolytic solution increase
Solution Approach 1:
The fast ionic conductor coating serves as an intermediary layer that allows lithium ion transport while blocking direct contact between the lithium-rich manganese-based material and the electrolyte. This mediator enables high voltage operation for high energy density while preventing harmful side reactions with the electrolytic solution
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 modified material improves first efficiency, cycle stability, and rate performance by inhibiting oxygen loss, stabilizing the crystal structure, and reducing side reactions, while maintaining high energy density.
Implementation Method 1
anion doping mainly replaces sites of oxygen in the lithium-rich manganese-based positive electrode material, which can inhibit excessive oxidation of lattice oxygen at a high potential and alleviate loss of the lattice oxygen
Implementation Method 2
Cation doping mainly replaces sites of transition metal in the lithium-rich manganese-based material, which can stabilize the crystal structure, improve the formation energy of the oxygen vacancies, and inhibit the transformation of the material to a spinel structure
Implementation Method 3
The fast ionic conductor material, as the so-called coating layer in this field, can effectively improve the ionic conductivity of the lithium-rich manganese-based material, improve the transmission rate of lithium ions
Implementation Method 4
the fast ion conductor material has stable properties, which effectively reduces the side reactions between the material and the electrolytic solution under the condition of high potential
Data Source
AI summary
A modified lithium-rich manganese-based material, a modification method of a lithium-rich manganese-based material, a secondary battery and an electrical device are provided. The modified lithium-rich manganese-based material includes a lithium-rich manganese-based material co-doped with anion and cation and a fast ionic conductor material. The lithium-rich manganese-based material has a chemical formula of xLi2MnO3·(1−x)LiNiyCozMnaO2, where 0<x<1, 0≤y≤1, 0≤z≤1, and y+z+a=1. A doped cationic element M1 is selected from at least one of a group consisting of Na, Fe, Nb, Ti, Mg, Al, Cr, and Er, and a doped anionic element M2 is selected from at least one of a group consisting of F, Cl, Br, I, S, B, P, N, Se, and Te. The first efficiency, cycle stability, thermal stability, rate performance and capacity of the material are improved.