LMFP Cathode Composition With Carbon Coating for Better Rate Performance
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Solution Overview
Problem
Lithium manganese iron phosphate positive electrode materials exhibit low ionic conductivity and electronic conductivity, leading to poor rate performance in lithium-ion batteries.
Innovation Solution
A positive electrode active material with high ionic and electronic conductivity is developed, composed of secondary particles with primary particles having a specific chemical composition and a carbon coating layer, optimized through a controlled preparation process involving grinding, granulation, and sintering under protective atmospheres.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium manganese iron phosphate is used as positive electrode active material, then energy density and discharge voltage are improved, but ionic conductivity and electronic conductivity are low, resulting in poor rate performance
Solution Approach 1:
The patent changes the chemical composition parameters by introducing doping elements (Al, Mg, Ni, Co, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn, or Y) at controlled concentrations (0 < x ≤ 0.5 and 0 < y ≤ 0.1 in the formula Li1+aFe1-x-yMnxAy(PO4)3) to optimize both energy density and conductivity. This compositional parameter adjustment resolves the contradiction by enhancing ionic and electronic conductivity while maintaining high energy density characteristics.
Solution Approach 2:
The patent creates a composite material structure by combining lithium manganese iron phosphate with doping elements to form a doped lithium manganese iron phosphate compound. This composite approach integrates the high energy density benefits of lithium manganese iron phosphate with the conductivity improvements provided by the doping elements, thereby resolving the contradiction between energy density and rate performance.
2Power
If lithium manganese iron phosphate is used as positive electrode active material, then discharge voltage is improved, but ionic conductivity and electronic conductivity are low
Solution Approach 1:
The patent adjusts the chemical composition parameters through doping with specific elements at controlled concentrations to simultaneously enhance discharge voltage and ionic/electronic conductivity. The doping parameters (x and y in the formula) are optimized to achieve both high power output and good conductivity.
Solution Approach 2:
The doping elements act as intermediaries that facilitate charge transport and improve conductivity while maintaining the high discharge voltage characteristics. These intermediary elements provide additional conduction pathways and improve the overall electrical properties of the material.
3Quantity of substance
If lithium manganese iron phosphate is used as positive electrode active material, then theoretical capacity is improved, but structure stability is insufficient leading to poor cycle life
Solution Approach 1:
The patent modifies the compositional parameters by introducing doping elements at optimized concentrations to strengthen the crystal structure while maintaining high theoretical capacity. The doping parameters are carefully controlled to enhance structure stability without significantly reducing capacity.
Solution Approach 2:
The patent creates a composite structure by doping lithium manganese iron phosphate with stabilizing elements that reinforce the crystal lattice. This composite material approach maintains the high capacity characteristics while improving structural stability and cycle life through the synergistic effects of the doping elements.
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 material significantly improves the rate performance of lithium-ion batteries by enhancing ionic and electronic conductivity, while maintaining high capacity and cycle performance.
Implementation Method 1
the positive electrode active material further includes a carbon coating layer covering a surface of the primary particles
Implementation Method 2
Granulating the second mixed slurry to obtain a third raw material having a median particle size of 3-4μm. (4) Sintering the third raw material under a protective atmosphere at a sintering temperature of 650-670°C for 6-8h
Data Source
Figure 1~3
AI summary
A positive electrode active material and a preparation method thereof. The positive electrode active material includes a secondary particle composed of primary particles; and the primary particle includes Li1+aFe1-x-yMnxAy(PO4), where -0.1≤a≤0.4, 0.5≤x≤0.7, 0≤y≤0.01, A includes at least one of Al, Mg, Ni, Co, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn, or Y, and the positive electrode active material has a crystallinity of not less than 98%. The positive electrode active material has high crystallinity, and the ionic conductivity and electronic conductivity thereof are high. Applying the positive electrode active material to a lithium-ion battery can significantly improve the rate performance of the battery.