Graded Multi-Shell LMFP Cathode for Conductivity and Thermal Stability
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Solution Overview
Problem
Lithium manganese iron phosphate cathode materials exhibit poor electrical conductivity and incomplete electrochemical performance due to their inherent insulating nature, limiting their application in lithium-ion batteries.
Innovation Solution
A lithium-containing multi-phosphate cathode material is developed, comprising a single-core multi-shell structure with a core of lithium iron phosphate or lithium manganese iron phosphate and multiple layers of lithium manganese iron phosphate coating, where the manganese content and particle size progressively increase and decrease radially, respectively, accompanied by a carbon coating layer to enhance conductivity and compactness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If lithium manganese iron phosphate is used as cathode material, then voltage plateau and thermal stability are improved, but electrical conductivity deteriorates
Solution Approach 1:
The patent uses composite materials by combining lithium manganese iron phosphate with carbon coating and multi-layer phosphate coatings. The carbon coating layer provides conductive pathways while the phosphate layers maintain structural stability, creating a composite structure that simultaneously improves conductivity and preserves thermal stability.
Solution Approach 2:
The patent applies local quality by creating a multi-layer coating structure where different layers have different compositions and functions. The carbon coating provides conductivity at the surface, while inner phosphate layers provide structural stability, allowing each region to optimize its local properties for specific functions.
2Reliability
If carbon coating is applied to improve electrical conductivity, then conductivity is enhanced, but electrochemical performance remains insufficient
Solution Approach 1:
The patent creates a composite coating structure combining carbon with multiple phosphate layers. This composite approach provides both the conductivity enhancement from carbon and the electrochemical performance improvement from the phosphate layers, achieving both goals simultaneously rather than sequentially.
Solution Approach 2:
The patent implements a nested multi-layer structure where carbon coating is embedded within multiple phosphate coating layers. This nested arrangement allows the carbon to provide conductivity while being protected and supplemented by the phosphate layers, creating a hierarchical structure that delivers both conductivity and electrochemical performance.
3Manufacturing precision
If multi-layer coating structure is used to improve compactness, then compactness is enhanced, but electrochemical performance is still not fully exhibited
Solution Approach 1:
The patent uses a nested multi-layer coating structure where multiple phosphate layers with different compositions are arranged concentrically. This nested design achieves compactness through layered arrangement while the gradient composition from inner to outer layers optimizes electrochemical performance by providing different functional properties at different depths.
Solution Approach 2:
The patent applies local quality by varying the composition of phosphate layers at different positions. Inner layers have different Mn/Fe ratios compared to outer layers, allowing each layer to optimize its local properties for specific functions such as structural stability, conductivity, or electrochemical activity, thereby achieving both compactness and enhanced performance.
Data Source
AI summary
The present application belongs to battery materials, and in particular, to a lithium-containing multi-phosphate cathode material and a preparation method therefor, and a secondary battery. The lithium-containing multi-phosphate cathode material includes a single-core multi-shell lithium manganese iron phosphate composite material, the composite material includes a core of lithium iron phosphate or lithium manganese iron phosphate, N lithium manganese iron phosphate coating layers coated on an outer surface of the core, and a carbon coating layer coated on an outermost layer of the composite material; N is an integer greater than or equal to 1; a manganese content in the N lithium manganese iron phosphate coating layers successively increases in a radially outward direction, and a particle size of the lithium manganese iron phosphate particles in the N lithium manganese iron phosphate coating layers successively decreases in the radially outward direction.