Fluorinated Spinel Cathode Material for Higher-Voltage Li-Ion Batteries
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Solution Overview
Problem
Existing non-aqueous electrolyte secondary batteries do not achieve high discharge voltages with existing positive electrode active materials.
Innovation Solution
A composite oxide with a crystal structure belonging to the space group Fm-3m, represented by the formula LixTMtmMyO2-fFf, is used as the positive electrode active material, where Q=2×tm×{1−(1−f/2)5} ≥ 1, and the dV/dq-SOC curve exhibits one or more peaks between 40% and 70% SOC during charging, ensuring high discharge voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional positive electrode active materials are used, then the battery structure is simple and easy to manufacture, but the discharge voltage is low and energy density is insufficient
Solution Approach 1:
The patent employs a composite oxide material with spinel structure containing multiple transition metals (Mn, Ni, Co, Zn) and fluorine substitution. This composite material approach enables achieving high discharge voltage (above 3.5V) and high capacity (above 100 mAh/g) by combining the advantages of different metals while using fluorine to stabilize the structure and prevent Jahn-Teller distortion.
Solution Approach 2:
The patent systematically optimizes compositional parameters including the ratio of transition metals (Mn:Ni:Co:Zn), fluorine content (f in LixTMtmMyO2-fFf), and lithium content (x). By controlling these parameters within specific ranges, the material achieves both high discharge voltage and structural stability, resolving the contradiction between performance improvement and material complexity.
2Quantity of substance
If high capacity materials are used to increase energy density, then the discharge capacity increases, but the discharge voltage decreases
Solution Approach 1:
The spinel composite oxide combines Mn3O4 (providing high capacity) with Ni, Co, and Zn compounds (providing high voltage stability). The synergistic effect of these components enables simultaneous achievement of high discharge capacity (above 100 mAh/g) and high discharge voltage (above 3.5V), directly resolving the voltage-capacity trade-off.
Solution Approach 2:
Different transition metal elements are distributed in specific crystallographic sites within the spinel structure, with each element contributing its unique properties: Mn provides high capacity through multi-electron redox, while Ni, Co, and Zn stabilize the structure and maintain high voltage. This local differentiation of functional roles enables simultaneous optimization of voltage and capacity.
3Stability of the object's composition
If fluorine substitution is increased to stabilize the crystal structure, then the structural stability improves, but the oxygen content decreases which may affect capacity
Solution Approach 1:
The patent precisely controls the fluorine substitution parameter (f in LixTMtmMyO2-fFf) within an optimal range. This controlled substitution stabilizes the spinel structure by preventing Jahn-Teller distortion and maintaining cubic symmetry, while the parameter optimization ensures sufficient oxygen content remains to support high discharge capacity (above 100 mAh/g).
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 composite oxide material achieves a higher discharge voltage and capacity compared to conventional materials, with discharge capacities exceeding 100 mAh/g and discharge voltages above 3.5 V, enhancing the performance of non-aqueous electrolyte secondary batteries.
Implementation Method 1
performs charging and discharging by moving lithium ions and the like between the positive electrode and the negative electrode
Implementation Method 2
one or more peaks in an SOC range of greater than or equal to 40% and less than or equal to 70% appear in a dV/dq-SOC curve showing a relationship between a state of charge SOC of the half-cell and dV/dq
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 40% to 70%.