Lithium Manganese Oxide Cathode with (440) Planes for High Diffusivity
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Solution Overview
Problem
Conventional lithium manganese oxides with a spinel structure face challenges in the 3V region due to low lithium ion diffusivity, short cycle lifespan, and poor capacity, making their utilization difficult, especially when (111) planes are predominantly formed instead of the higher diffusivity (440) planes.
Innovation Solution
A cathode active material with a lithium manganese-based oxide having a specific spinel structure where (440) planes are predominantly formed, combined with a first carbonaceous material and a second carbonaceous material of smaller particle diameter, enhancing lithium ion diffusivity and capacity, and synthesized using high energy milling to achieve a core-shell phase transition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If spinel lithium manganese oxide is synthesized using general solid state reaction method, then (111) planes with lower surface energy are predominantly formed, but lithium ion diffusivity is relatively low
Solution Approach 1:
The patent applies high energy milling to change the crystallographic orientation parameters of spinel lithium manganese oxide, transforming the predominant plane from (111) to (440). This parameter change in crystal structure orientation directly improves lithium ion diffusivity while maintaining structural stability, resolving the contradiction between surface energy stability and ion transport speed.
Solution Approach 2:
High energy milling introduces mechanical vibration and impact to the crystal structure during synthesis, which reorients the crystal planes to predominantly expose (440) planes. This mechanical action overcomes the natural tendency to form (111) planes and creates the desired high-diffusivity structure.
2Quantity of substance
If spinel lithium manganese oxide is used in the 3V region, then capacity variation occurs, but cycle lifespan is significantly deteriorated due to phase transition and manganese elution
Solution Approach 1:
The patent changes the crystal structure parameter by inducing a core-shell phase transition through high energy milling, creating a stable tetragonal phase structure in the 3V region. This parameter change prevents Jahn-Teller distortion and manganese elution, thereby maintaining both capacity and cycle lifespan during charge-discharge cycles.
Solution Approach 2:
The patent creates a composite structure with core-shell phase transition, where the milled material forms a stable tetragonal phase shell around the spinel core. This composite architecture prevents direct contact between manganese and electrolyte, reducing elution and improving reliability while maintaining capacity.
3Reliability
If LiCoO2 is used as cathode active material, then long cycle lifespan and high charge-discharge efficiency are achieved, but structural stability is low and cost is high due to limited cobalt availability
Solution Approach 1:
The patent replaces expensive cobalt-based materials with cheaper spinel lithium manganese oxide. While conventional spinel has short cycle lifespan, the high energy milling treatment extends its life by creating a stable tetragonal phase structure, making it a cost-effective alternative that maintains reliability.
Solution Approach 2:
The patent changes the crystal structure parameters of lithium manganese oxide through high energy milling, transforming it from a conventional spinel structure with low structural stability to a modified structure with enhanced stability and long cycle lifespan, matching or exceeding LiCoO2 performance.
4Quantity of substance
If LiNiO2-based cathode active material is used, then high discharge capacity is achieved, but rapid phase transition occurs in crystal structure and safety is sharply reduced when exposed to air and moisture
Solution Approach 1:
The patent uses lithium manganese oxide as a safer alternative to LiNiO2. While conventional spinel has capacity limitations, the high energy milling treatment enhances capacity while maintaining the inherent thermal and chemical stability of manganese-based materials, providing both high capacity and safety.
Solution Approach 2:
The patent converts the potential harm of manganese elution and phase transition in the 3V region into a benefit by using high energy milling to create a stable tetragonal phase structure. This transformation allows the material to operate safely in the 3V region with enhanced capacity and stability.
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 exhibits improved lithium ion diffusivity, leading to enhanced C-rate and capacity properties, resulting in a lithium secondary battery with increased lifespan and capacity in the 3V region, outperforming conventional materials in both cubic and tetragonal crystal structures.
Implementation Method 1
synthesized using high energy milling to achieve a core-shell phase transition
Implementation Method 2
synthesized using high energy milling to achieve a core-shell phase transition
Implementation Method 3
provide excellent capacity and long cycle lifespan, resulting in improved lithium ion diffusivity
Data Source
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AI summary
Disclosed is a cathode active material including a lithium manganese-based oxide. The lithium manganese-based oxide has a spinel structure represented by Formula 1 below and high lithium ion diffusivity since (440) planes are predominantly formed in a crystal structure thereof. Li1+xMyMn2-x-yO4-zQz (1) In Formula 1, 0≤x≤0.3, 0≤y≤1, and 0≤z≤1, M includes at least one element selected from the group consisting of Al, Mg, Ni, Co, Fe, Cr, V, Ti, Cu, B, Ca, Zn, Zr, Nb, Mo, Sr, Sb, W, Ti, and Bi, and Q includes at least one element selected from the group consisting ofN, F, S, and Cl.