Fluorinated Rock-Salt Cathode Material for Higher Battery Capacity
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Solution Overview
Problem
Existing lithium ion secondary batteries face limitations in achieving high energy density and capacity, despite advancements in positive electrode active materials, as the effects of capacity improvement are insufficient.
Innovation Solution
A lithium metal composite oxide with a rock salt structure belonging to the Fm-3m space group is used, featuring vacancies that allow lithium ions to move easily, combined with the introduction of fluorine atoms to stabilize the Li-excess state and increase discharge potential, resulting in a positive electrode active material with enhanced capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a Li-excess type lithium metal composite oxide based on rock salt structured LixMn1-xO2 is used to achieve high energy density, then the energy density increases, but the capacity improvement effects are insufficient
Solution Approach 1:
The patent applies local quality by creating oxygen vacancies at specific lattice positions within the rock salt structure. These vacancies are not uniformly distributed but are strategically positioned to optimize lithium ion transport pathways while maintaining structural stability. The vacancies create localized regions of enhanced ion conductivity without compromising the overall structural integrity, thereby improving capacity while maintaining high energy density.
Solution Approach 2:
The patent utilizes parameter changes by controlling the oxygen vacancy concentration and distribution within the lithium metal composite oxide. By adjusting the oxidation state of manganese and controlling synthesis conditions, the patent optimizes the number and positioning of oxygen vacancies. This parameter optimization enables the material to achieve both high energy density from the Li-excess composition and improved capacity through enhanced lithium ion mobility provided by the vacancies.
2Quantity of substance
If cobalt is replaced with nickel to achieve high capacity, then the capacity increases, but the structural stability deteriorates
Solution Approach 1:
The patent employs composite materials by combining nickel-rich lithium metal composite oxide with a rock salt structured lithium manganese oxide matrix containing oxygen vacancies. This composite structure allows the nickel component to provide high capacity while the rock salt matrix with oxygen vacancies provides structural stability and pathways for lithium ion transport. The oxygen vacancies act as structural stabilizers that prevent excessive lattice distortion caused by high nickel content, thereby maintaining both high capacity and structural integrity.
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 enables the realization of a secondary battery with improved energy density and capacity, as demonstrated by increased initial discharge capacity and stable voltage distribution, effectively addressing the limitations of previous technologies.
Implementation Method 1
the crystal structure has a vacancy to which no lithium or metal atom is disposed
Data Source
AI summary
A positive electrode active material for a secondary battery has a lithium metal composite oxide having a crystal structure based on a rock salt structure belonging to a space group Fm-3m, and the crystal structure has a vacancy to which no lithium or metal atom is disposed. For the lithium metal composite oxide, for example, a composite oxide represented by a composition formula LiaMnbMcO2-dFd (where M is at least one metal element excluding Li and Mn, 0<a≤1.4, 0.4≤b≤0.95, 0≤c≤0.2, 0≤d≤0.66, and 1.75≤a+b+c<2 are satisfied) can be used.