Gradient-Fluorine Lithium Manganate Cathode for Longer Cycle Life
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Solution Overview
Problem
Lithium manganese oxide cathode materials suffer from manganese dissolution during cycling, leading to reduced cycling life and stability, and existing fluorine doping techniques fail to achieve optimal improvement due to insufficient penetration depth.
Innovation Solution
A lithium manganese oxide cathode material with a chemical formula Li a Al b Mn 2-b-c B c O 4-d F d, where fluorine penetrates with a decreasing gradient distribution from the surface to the center, and a sphericity of 0.8 to 1 is maintained to reduce the (111) crystal plane proportion, combined with a two-stage low-temperature sintering process to enhance structural stability and electronic conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fluorine is doped into lithium manganese oxide to improve structural stability and reduce manganese dissolution, then cycling life is improved, but existing techniques only achieve surface coating with insufficient penetration depth
Solution Approach 1:
The patent implements a gradient distribution of fluorine concentration throughout the cathode material particles, with higher concentration at the surface and progressively lower concentration toward the center. This local variation in fluorine content optimizes both surface stability and bulk structural properties, resolving the contradiction between achieving sufficient penetration depth and maintaining surface effectiveness.
Solution Approach 2:
The patent changes the physical and chemical parameters of the sintering process, including using a two-stage sintering method with different temperature ranges (first stage: 600-800°C, second stage: 800-1000°C), controlling oxygen partial pressure, and adjusting sintering time. These parameter changes enable fluorine to penetrate deeper into the material bulk while maintaining appropriate surface concentration.
2Use of energy by moving object
If lithium cobalt oxide is used as cathode material to achieve high energy density, then battery performance is improved, but cost increases and safety risks arise due to thermal runaway
Solution Approach 1:
The patent substitutes expensive and safety-prone cobalt with abundant and safe manganese, creating a cost-effective and safer cathode material. While pure lithium manganese oxide has structural instability issues, the patent resolves this through fluorine doping and gradient distribution, achieving both safety and performance requirements.
Solution Approach 2:
The patent creates a composite structure by doping fluorine into lithium manganese oxide lattice and forming a gradient distribution profile. This composite approach combines the safety and cost advantages of manganese-based materials with the structural stability benefits of fluorine modification, eliminating the need for cobalt while maintaining high energy density.
3Ease of manufacture
If ternary materials like lithium nickel manganese cobalt oxide are used to reduce cost compared to lithium cobalt oxide, then manufacturing cost is reduced, but temperature sensitivity and capacity degradation occur
Solution Approach 1:
The patent extracts nickel from the cathode material composition, using only lithium, manganese, and fluorine. This eliminates the temperature sensitivity and capacity degradation issues associated with nickel-containing ternary materials while maintaining cost-effectiveness through manganese's abundance and stability.
Solution Approach 2:
The patent modifies the compositional parameters by introducing fluorine doping and creating a gradient distribution profile. This changes the material's thermal and electrochemical stability parameters, eliminating temperature sensitivity while maintaining low cost through manganese-based composition.
4Reliability
If lithium iron phosphate is used as cathode material to achieve excellent safety and low cost, then safety and cost are improved, but capacity is relatively low making it unsuitable for high-capacity batteries
Solution Approach 1:
Instead of using lithium iron phosphate's olivine structure with P-O bonds, the patent inverts to a spinel lithium manganese oxide structure with Mn-O bonds. This structural inversion enables higher capacity while maintaining safety through fluorine doping, which stabilizes the manganese-based spinel structure against degradation and manganese dissolution.
Solution Approach 2:
The patent creates a fluorine-doped lithium manganese oxide composite with gradient distribution. This composite structure combines the high capacity potential of manganese-based spinel materials with the safety and stability benefits of fluorine modification, achieving both high capacity and safety without being limited by lithium iron phosphate's lower capacity constraints.
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 gradient fluorine distribution and controlled sphericity significantly reduce manganese dissolution, enhancing cycling life and stability while maintaining high energy density and low production costs.
Implementation Method 1
the penetration of fluorine can alter an electronic band structure of the lithium manganese oxide cathode material, thereby improving the electronic conductivity and electrochemical reactivity
Implementation Method 2
The decreasing gradient distribution of fluorine from the surface to the center of the lithium manganese oxide cathode material particle can enhance a crystal structure of the lithium manganese oxide cathode material to some extent and mitigate the Jahn-Teller effect, thereby reducing the manganese dissolution caused by structural distortion
Implementation Method 3
a preparation method of the lithium manganese oxide cathode material, including the following steps: (1) weighing a lithium source, a manganese source, and a boron source according to a stoichiometric ratio
Data Source
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AI summary
Provided is a lithium manganese oxide cathode material with a chemical formula of LiaAlbMn2-b-cBcO4-dFd, where 0.96 ≤ a ≤ 1.15, 0 < b ≤ 0.3, 0 < c ≤ 0.03, and 0 < d <_ 0.03. A secondary particle of the lithium manganese oxide cathode material is spherical. A fluorine penetrates into the lithium manganese oxide cathode material, and a fluorine content presents a decreasing gradient distribution from a surface to a center of a lithium manganese oxide cathode material particle. The present disclosure also provides a preparation method of the lithium manganese oxide cathode material, including: mixing a lithium source, a manganese source, and a boron source, and conducting first sintering to produce a lithium manganese oxide cathode material precursor; and mixing the lithium manganese oxide cathode material precursor with an aluminum source and a fluorine source, and conducting second sintering to produce the lithium manganese oxide cathode material. The gradient distribution of fluorine in the lithium manganese oxide cathode material can be adjusted to enhance the stability of a crystal structure inside the lithium manganese oxide cathode material and prevent an internal structure of the lithium manganese oxide cathode material from collapsing during a charge-discharge process.