Dual-Carbon Coated Cathode Material for Mn Leaching Control
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Solution Overview
Problem
Olivine-structured phosphate compounds in lithium-ion batteries suffer from low electronic conductivity, slow lithium-ion diffusion rates, and manganese leaching issues due to non-uniform carbon coating, hindering their large-scale application and performance.
Innovation Solution
A positive electrode material with a core layer of Li, Fe, Mn, PO4 ions and doping element A, coated with a shell layer of carbon particles, where the carbon coating is applied in two stages with distinct particle sizes to ensure uniformity and smoothness, enhancing conductivity and reducing manganese leaching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If carbon coating is applied to reduce manganese leaching, then cycling performance is improved, but the coating becomes non-uniform and uneven, failing to address manganese leaching and potentially impairing electrical conductivity
Solution Approach 1:
The patent divides the carbon coating process into two distinct stages: first carbon coating (0.5-2 wt%) and second carbon coating (2-5 wt%). This segmentation allows each stage to serve different purposes - the first stage provides initial coverage while the second stage ensures uniformity and smoothness, thereby resolving the contradiction between achieving sufficient coating for manganese protection and maintaining manufacturing precision
Solution Approach 2:
The first carbon coating is applied as a preliminary action before the second carbon coating. This preliminary coating establishes a base layer that prevents manganese leaching, while the subsequent second coating refines the surface uniformity and smoothness. This sequential preliminary action approach ensures both manganese protection and coating quality
2Use of energy by moving object
If manganese proportion is increased to enhance energy density, then energy density is improved, but manganese leaching occurs during material cycling
Solution Approach 1:
The patent creates a composite structure with a lithium iron manganese phosphate core layer containing high manganese content (0.7-1.0 wt%) for high energy density, surrounded by a carbon-containing protective shell layer (0.5-5 wt%) that prevents manganese leaching. This composite material approach allows the system to simultaneously achieve high energy density from the manganese-rich core and manganese retention through the protective carbon shell
3Ease of manufacture
If solid-phase dry technology is used for carbon coating, then the process is simple, but the carbon material cannot be uniformly coated onto the material surface
Solution Approach 1:
The patent optimizes multiple parameters of the solid-phase dry coating process including carbon particle size (0.5-5 μm), carbon content (0.5-5 wt%), coating temperature (500-800°C), and coating time (2-24 hours). By carefully controlling these parameters, the simple solid-phase dry process achieves both ease of manufacture and uniform carbon coating, resolving the contradiction between process simplicity and coating quality
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 solution results in a positive electrode material with improved electrical conductivity, high energy density, and reduced manganese leaching, ensuring high cyclic discharge efficiency and long battery life.
Implementation Method 1
subjecting the first positive electrode material and a first carbon particle to a secondary sintering treatment under the reducing atmosphere to obtain a second positive electrode material
Implementation Method 2
The doping element A can result in Li-site or M-site defects in the lattice of manganese iron phosphate, creating vacancies or altering interatomic bond lengths in the lattice of material, which facilitates Li-ion movement in the lattice
Data Source
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AI summary
A positive electrode material and a preparation method thereof, and a lithium-ion battery. The positive electrode material includes: a core layer including Li, Fe, Mn, PO4- ions, and doping element A; a shell layer, where at least a surface portion of the shell layer is coated on an outer surface of the core layer and the shell layer includes a first carbon particle and a second carbon particle; where the doping element A includes at least one element of Al, Mg, Ni, Co, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn and Y; a distance difference between the highest point and the lowest point in a single surface of the positive electrode material is not more than 1 nm, and the surface roughness of the positive electrode material is 0.8µm to 1.6µm. Through the two carbon coating processes, on the basis of ensuring the high capacity and high compaction of the positive electrode material, manganese leaching is greatly reduced, ensuring the cyclic discharge efficiency of the positive electrode material.