Cu-Fluorine Rock Salt Cathode Composition for Higher Discharge Voltage
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Solution Overview
Problem
Lithium metal composite oxides with a rock salt structure, as described in existing patents, tend to have low average discharge voltage and wide voltage distribution, limiting the achievement of high capacity in secondary batteries.
Innovation Solution
Incorporating copper (Cu) and a transition metal element other than lithium and copper, such as manganese, into the lithium metal composite oxide with a rock salt structure, along with fluorine substitution for oxygen, to enhance the average discharge voltage and stabilize the lithium-excessive state, thereby increasing the usable capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium metal composite oxide with rock salt structure is used to achieve high capacity, then the energy density can be improved, but the average discharge voltage becomes low and voltage distribution becomes wide
Solution Approach 1:
The patent changes the chemical composition parameters by introducing copper (with 0.01 ≤ Cu/(Cu+M1) ≤ 0.50) and fluorine (with 0.05 ≤ F/O ≤ 0.50) into the lithium metal composite oxide structure. This compositional modification adjusts the electronic and electrochemical properties, raising the average discharge voltage from the typical low range to 3.0 V or higher while preserving the high capacity characteristics of the lithium-excessive rock salt structure material.
Solution Approach 2:
The patent creates a composite material system by combining lithium metal oxide with copper and fluorine elements in a specific composition ratio. The resulting composite oxide (Li1+x-yCu yM1zFwO2-a) integrates multiple functional elements: lithium provides high capacity, copper enhances voltage, and fluorine stabilizes the structure. This composite approach allows simultaneous achievement of high capacity and high average discharge voltage.
2Quantity of substance
If lithium metal composite oxide with rock salt structure is used, then high capacity can be achieved, but the voltage distribution becomes wide reducing usable capacity
Solution Approach 1:
The patent modifies the compositional parameters by controlling the ratios of copper and fluorine within specific ranges. This parameter optimization narrows the voltage distribution by creating a more uniform electrochemical environment throughout the material structure, ensuring that the majority of capacity operates within a concentrated voltage range rather than being spread widely.
Solution Approach 2:
The patent converts the inherent structural characteristics of the lithium-excessive rock salt phase, which originally cause wide voltage distribution, into beneficial features. By introducing copper and fluorine, the material's natural voltage spread is harnessed and redistributed to create a more favorable voltage profile that maintains high capacity while concentrating the voltage output in a more useful range.
Data Source
AI summary
A positive electrode active material for a secondary battery includes a lithium metal composite oxide having a crystal structure based on a rock salt structure belonging to a space group Fm-3m, wherein the lithium metal composite oxide includes Cu and a transition metal element M1 other than Li and Cu. The lithium metal composite oxide is preferably represented by a composition formula LiaMnbCucA2dO2-eFe (where A2 is at least one element excluding Li, Mn, Cu, O, and F, and 0<a≤1.35, 0.4≤b≤0.9, 0<c≤0.2, 0≤d≤0.2, 0≤e≤0.66, 1.75≤a+b+c+d≤2 are satisfied).