LMR Cathode Composition for Lower Voltage Decay and Better Rate Capability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium and manganese-rich (LMR) positive electrode active materials face issues such as voltage decay during cycling, poor rate capability, and lower volumetric energy density, hindering their commercialization.
Innovation Solution
A positive electrode active material composition represented by Li1.1Mn0.52Ni0.38-xMxO2, where M is Co or Cr, and the average oxidation state of Ni ion is less than 2.15, with 0<x<0.06, is developed to mitigate these issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If LMR positive electrode active material is used to achieve high gravimetric energy density, then voltage decay during cycling occurs severely
Solution Approach 1:
The patent modifies the chemical composition parameters of the LMR material by controlling the average oxidation state of Ni ions to be less than 2.15 and adjusting the ratio of divalent to tetravalent metal ions to fall between 0.4 and 0.6. These parameter changes stabilize the crystal structure during cycling, reducing voltage decay while maintaining high gravimetric energy density.
Solution Approach 2:
The patent creates a composite material system combining multiple metal elements (Ni, Co, Mn, and other divalent/tetravalent metals) in specific ratios. This composite approach allows the material to benefit from the high capacity of Ni-rich compositions while the divalent/tetravalent metal ratio control provides structural stability, mitigating voltage decay during cycling.
2Use of energy by moving object
If LMR positive electrode active material is used to achieve high gravimetric energy density, then rate capability deteriorates
Solution Approach 1:
By optimizing the average oxidation state of Ni ions to be less than 2.15 and controlling the divalent/tetravalent metal ion ratio between 0.4 and 0.6, the patent improves the electronic conductivity and lithium ion diffusion kinetics of the material. These parameter changes enable faster charge-discharge rates while maintaining high gravimetric energy density.
3Use of energy by moving object
If LMR positive electrode active material is used to achieve high gravimetric energy density, then cycle performance deteriorates
Solution Approach 1:
The patent controls the average oxidation state of Ni ions to be less than 2.15 and adjusts the divalent/tetravalent metal ion ratio to between 0.4 and 0.6. These parameter changes prevent Jahn-Teller distortion and maintain structural integrity during repeated cycling, significantly improving cycle performance while preserving high gravimetric energy density.
Solution Approach 2:
The composite material system with controlled metal ion ratios provides enhanced structural stability during cycling. The balanced composition of divalent and tetravalent metals creates a more robust crystal structure that resists degradation over multiple charge-discharge cycles, improving long-term cycle performance.
4Use of energy by moving object
If LMR positive electrode active material is used to achieve high gravimetric energy density, then volumetric energy density decreases
Solution Approach 1:
By optimizing the average oxidation state of Ni ions to be less than 2.15 and controlling the divalent/tetravalent metal ion ratio between 0.4 and 0.6, the patent achieves a balance between gravimetric and volumetric energy density. These parameter changes prevent excessive volume expansion while maintaining high capacity, improving volumetric energy density without sacrificing gravimetric energy density.
Data Source
AI summary
A positive electrode active material includes a compound represented by formula 1:Li1.1Mn0.52Ni0.38-xMxO2(1)wherein:M is Co or Cr;2<average oxidation state of Ni ion<2.15; and0<x<0.06.