Positive-Electrode Active Material for Stable Lithium-Ion Diffusion
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Solution Overview
Problem
Current positive-electrode active materials for batteries face challenges in achieving high capacity due to limitations in lithium ion diffusion, oxidation-reduction reactions, and structural stability, particularly with the rock-salt-type crystal structure being unable to maintain stability after lithium abstraction.
Innovation Solution
A positive-electrode active material with a crystal structure belonging to the space group FM3-M, represented by the composition LixMeyOαFβ, where Me includes various elements, and a lithium ion conductor is used to enhance lithium ion diffusion and maintain structural stability, with the lithium ion conductor present in limited amounts to prevent interface resistance increases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a rock-salt-type crystal structure is used for high capacity, then lithium ion diffusion is improved, but structural stability deteriorates after lithium abstraction
Solution Approach 1:
The patent uses a composite material system consisting of Li2MO3F compound with rock-salt-type crystal structure combined with lithium ion conductor. The Li2MO3F provides high lithium ion diffusion capability while the lithium ion conductor maintains structural stability during lithium abstraction, resolving the contradiction between diffusion performance and structural stability.
Solution Approach 2:
The patent optimizes the composition parameters of Li2MO3F by controlling the ratio of Li to (M+O+F) within specific ranges (Li/(M+O+F) = 1.7-2.2). This parameter optimization ensures the rock-salt-type structure maintains both high lithium ion diffusion and structural stability, transforming the trade-off into a balanced performance through precise compositional control.
2Stability of the object's composition
If lithium ion conductor is added to maintain structural stability, then structural stability is improved, but interface resistance increases
Solution Approach 1:
The patent applies local quality by selectively placing lithium ion conductor at specific locations (surface or interface regions) rather than uniformly throughout the material. This localized application provides structural stability where needed while minimizing the increase in interface resistance, as the lithium ion conductor is positioned to stabilize the crystal structure without creating excessive interfacial barriers to ion transport.
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
This configuration allows for higher-capacity batteries by stabilizing the crystal structure and improving lithium ion diffusion, resulting in increased discharge capacity and reduced interface resistance.
Implementation Method 1
a lithium ion conductor is used to enhance lithium ion diffusion
Implementation Method 2
stabilizing the crystal structure and improving lithium ion diffusion, resulting in increased discharge capacity and reduced interface resistance
Data Source
AI summary
A positive-electrode active material contains a compound that has a crystal structure belonging to a space group FM3-M and that is represented by the composition formula (1) and a lithium ion conductor,LixMeyOαFβ (1)wherein Me denotes one or two or more elements selected from the group consisting of Mn, Co, Ni, Fe, Al, B, Ce, Si, Zr, Nb, Pr, Ti, W, Ge, Mo, Sn, Bi, Cu, Mg, Ca, Ba, Sr, Y, Zn, Ga, Er, La, Sm, Yb, V, and Cr, and the following conditions are satisfied.1.7≤x≤2.2 0.8≤y≤1.3 1≤α≤2.5 0.5≤β≤2