Substituted Lithium Manganese Phosphate Cathode Core-Shell Design
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Solution Overview
Problem
Lithium manganese phosphate cathode materials face challenges with slow kinetics and energy density loss due to the iron plateau in discharge curves, making them unsuitable for high-energy battery applications.
Innovation Solution
Substituted lithium manganese metal phosphate compounds of the formula LiFe x Mn 1-x-y M y PO 4, where M is a divalent metal like Zn, Ca, or Mg, with specific doping levels, enhance energy density and charge/discharge kinetics by incorporating electrochemically inactive metals, and a carbon matrix for improved conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If iron substitution is increased to improve electrical properties, then electrochemical activity improves, but energy density decreases due to the iron plateau in discharge curves
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the core contains high-iron-content LiFe1-xMxPO4 for electrochemical activity and the shell contains low-iron-content LiFe1-yMyPO4 for energy density, allowing each region to optimize its function locally
Solution Approach 2:
The patent uses composite materials by combining two different lithium phosphate phases with different iron contents into a single cathode material system, where the composite structure achieves both high electrochemical activity and high energy density
2Quantity of substance
If manganese content is increased to improve energy density, then capacity increases, but charging and discharging kinetics become slower
Solution Approach 1:
The patent applies local quality by concentrating high manganese content in the core region for energy density while the shell region has optimized composition for kinetics, allowing each region to specialize in its function
Solution Approach 2:
The patent segments the cathode material into core and shell regions with different compositions, where the core provides capacity and the shell provides kinetic performance
3Speed
If divalent metal substitution is increased to improve kinetics, then charge/discharge speed improves, but structural stability may be compromised
Solution Approach 1:
The patent applies parameter changes by precisely controlling the divalent metal content parameter (x and y values) within optimal ranges to achieve kinetic improvement while maintaining structural stability through parameter optimization
Data Source
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AI summary
The invention relates to a substituted lithium-manganese metal phosphate of formula LiFexMn1-x-yMyPO4, in which M is a bivalent from the group Sn, Pb, Zn, Mg, Ca, Sr, Ba, Co, Ti and Cd, and x < 1, y < 0,3 and x + y < 1. The invention also relates to a method for the production thereof and to the use thereof as a cathode material in a secondary lithium ion battery.