Fluorinated Spinel Cathode Composition for Higher Discharge Capacity
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Solution Overview
Problem
Existing positive electrode active materials for non-aqueous electrolyte secondary batteries do not achieve high discharge capacity.
Innovation Solution
A composite oxide with a crystal structure belonging to space group Fm-3m, represented by the formula LixTMtmMyO2-fFf, where Q=2×tm×{1−(1−f/2)5} < 1, is used as the positive electrode active material, ensuring one or more peaks appear in the dV/dq-SOC curve within the 10% to 40% state of charge (SOC) range, enhancing discharge capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional positive electrode active materials are used, then the battery structure is simple and easy to manufacture, but the discharge capacity is insufficient
Solution Approach 1:
The patent employs a composite oxide material with spinel structure containing multiple transition metals (Mn, Ni, Co, Zn) in specific ratios. This composite material approach enables achieving high discharge capacity (≥100 mAh/g) by combining the advantages of different metals while suppressing their individual drawbacks, such as Jahn-Teller distortion in Mn-rich materials and structural instability in Ni-rich materials.
Solution Approach 2:
The patent systematically optimizes compositional parameters (molar ratios of TM metals, lithium content x, oxygen deficiency f) and structural parameters (spinel crystal structure with specific space group Fd-3m). By controlling these parameters within specific ranges, the material achieves both high discharge capacity and structural stability, resolving the contradiction between performance improvement and material complexity.
2Quantity of substance
If high discharge capacity is achieved through optimized material composition, then energy storage performance improves, but manufacturing precision requirements increase
Solution Approach 1:
The patent defines specific ranges for compositional parameters (e.g., 0.6 ≤ x ≤ 1.4, 0.05 ≤ f ≤ 0.5, and specific TM metal ratios) that balance performance and manufacturability. These parameter specifications enable achieving high discharge capacity while maintaining reasonable manufacturing precision requirements through systematic optimization rather than extreme parameter values.
Solution Approach 2:
The patent introduces zinc ions at specific octahedral sites in the spinel structure to locally suppress Jahn-Teller distortion and enhance structural stability. This localized modification approach allows achieving high discharge capacity without requiring extreme precision in overall compositional control, as the zinc ions provide local structural reinforcement.
Data Source
AI summary
A positive electrode active material for nonaqueous electrolyte secondary batteries according to the present invention is a composite oxide which is represented by general formula LixTMtmMyO2-fFf and has a crystal structure that belongs to the space group Fm-3m; and in the general formula, TM represents a transition metal, M represents a non-transition metal, and if Q=2×tm×(1−(1−f/2)5), Q<1 is satisfied. With respect to a dV/dq-SOC curve showing the relationship between the state of charge SOC and dV/dq of a half cell that contains this composite oxide, the dV/dq-SOC curve being obtained by charging the half cell with a charging current of 0.1 C at 25° C. to an end voltage within the range of 4.7 V to 4.95 V, there is one or more peaks within the SOC range from 10% to 40%.