Doped Vanadium Sulfide Cathode Composition for High-Capacity Cycling
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Solution Overview
Problem
Lithium ion secondary batteries face challenges in achieving high initial capacity and improved electrochemical performance due to limitations in cathode active materials, particularly low electronic conductivity and reversibility of metal polysulfides, and the need for increased sulfur content which reduces conductivity.
Innovation Solution
Incorporating specific foreign elements such as Nb, Ti, Zr, Mo, Sc, Li, B, N, O, F, Mg, S, Cl, Ca, Br, Sr, I, Fe, Co, Ni, Zn, Y, Mo, Tc, and Cd into vanadium sulfide to enhance structural stability and electronic conductivity, thereby stabilizing the structure and improving cycle and electrochemical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If sulfur content is increased to achieve high capacity, then capacity is improved, but electronic conductivity decreases
Solution Approach 1:
The patent changes the compositional parameters by incorporating foreign elements (M1: Nb, Ti, Zr, Mo, Sc, or Y; M2: Li, B, N, O, F, Mg, S, Cl, Ca, Br, Sr, Sc, I, Fe, Co, Ni, Zn, Y, Mo, Tc, or Cd) into the vanadium sulfide structure with specific molar ratios (M1/V: 0.05-1.5, M2/V: 0.05-1.5, S/V: 3.0-10.0). This parameter modification allows the material to achieve high sulfur content while maintaining improved electronic conductivity through the dopant elements.
Solution Approach 2:
The patent creates a composite material system by incorporating multiple foreign elements into the vanadium sulfide lattice. The foreign element-containing vanadium sulfide (V(M1xM2(1-x))ySz) forms a composite structure where the foreign elements work synergistically to provide both high capacity (through high sulfur content) and good conductivity (through the conductive foreign element network).
2Reliability
If foreign element is added to improve electronic conductivity, then electronic conductivity is improved, but electrode density decreases
Solution Approach 1:
The patent applies local quality by incorporating foreign elements at specific local positions within the vanadium sulfide crystal structure. The foreign elements are distributed at controlled concentrations (M1/V and M2/V ratios of 0.05-1.5) to provide localized conductivity enhancement without uniformly increasing the overall electrode volume or decreasing density.
Solution Approach 2:
The patent optimizes the compositional parameters to balance conductivity and density. By controlling the foreign element content within specific molar ratio ranges and maintaining S/V ratios of 3.0-10.0, the material achieves improved conductivity while preventing excessive volume expansion that would reduce electrode density.
3Stability of the object's composition
If structural stability is improved by foreign element incorporation, then cycle performance is improved, but initial capacity may be reduced
Solution Approach 1:
The patent optimizes the compositional parameters to balance structural stability and capacity. By controlling the foreign element ratios (M1/V and M2/V both at 0.05-1.5) and sulfur content (S/V at 3.0-10.0), the material achieves sufficient structural stability for good cycle performance while maintaining high initial capacity through the high sulfur content.
Solution Approach 2:
The patent creates a composite structure where foreign elements are incorporated into the vanadium sulfide lattice to provide structural stability. The multi-element composite (containing V, S, M1, and M2) creates a robust structure that maintains both stability and high capacity, as the foreign elements reinforce the lattice while the high sulfur content provides the capacity.
Data Source
AI summary
A foreign element-containing vanadium sulfide contains, as constituent elements, vanadium, sulfur, and a foreign element, wherein the compositional ratio of the foreign element to the vanadium (M1/V) is in the range of 0.05 to 1.5 in terms of molar ratio; the compositional ratio of the sulfur to the vanadium (S/V) is in the range of 3.0 to 10.0 in terms of molar ratio; and the foreign element includes at least one member selected from the group consisting of Nb, Ti, Zr, Mo, Sc, and Y, or includes at least one member selected from the group consisting of Li, B, N, O, F, Mg, S, Cl, Ca, Br, Sr, Sc, I, Fe, Co, Ni, Zn, Y, Mo, Tc, and Cd. The foreign element-containing vanadium sulfide is an electrode active material for a lithium ion secondary battery that exhibits satisfactorily high initial capacity and that provides improved electrochemical performance or cycle performance.