Scandium-Substituted Y2Ti2O5S2 Cathode for High Capacity
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Solution Overview
Problem
Lithium batteries require high-capacity active materials with improved thermal stability and reduced potential to enhance battery performance and safety, as existing materials like Y2Ti2O5S2 have low theoretical capacity due to yttrium's large atomic weight and high potential.
Innovation Solution
A battery active material with a Ruddlesden-Popper structure represented by the formula Y2−xScxTi2O5S2, where 0<x<2, is developed by substituting yttrium with scandium, which has a lower atomic weight and smaller ionic radius, resulting in a higher capacity and lower potential.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Y2Ti2O5S2 crystal phase is used as battery active material, then thermal stability is improved, but theoretical capacity per unit weight is low due to yttrium's large atomic weight
Solution Approach 1:
The invention changes the compositional parameters of the crystal phase by substituting yttrium with scandium in the Y2Ti2O5S2 structure. This parameter change (composition modification) reduces the average atomic weight while maintaining the thermally stable Ruddlesden-Popper crystal structure, thereby improving theoretical capacity per unit weight while preserving thermal stability.
Solution Approach 2:
The invention creates a composite crystal phase by combining scandium and yttrium in a specific ratio within the Ruddlesden-Popper structure (Y2-xScxTi2O5S2). This composite approach allows the material to inherit the thermal stability from the original Y2Ti2O5S2 structure while gaining the lower atomic weight benefit from scandium substitution, thus resolving the contradiction between thermal stability and capacity.
2Reliability
If Y2Ti2O5S2 crystal phase is used as battery active material, then thermal stability is improved, but potential is high which limits battery performance
Solution Approach 1:
The invention changes the electrochemical potential parameter by substituting yttrium with scandium. Scandium has a smaller ionic radius and different electronegativity compared to yttrium, which modifies the electronic structure and reduces the electrochemical potential of the crystal phase. This allows achieving lower potential while maintaining the thermally stable Ruddlesden-Popper structure.
3Quantity of substance
If yttrium is substituted with scandium to increase capacity, then theoretical capacity per unit weight is improved, but crystal structure stability may be compromised
Solution Approach 1:
The invention applies local quality by performing partial substitution of yttrium with scandium rather than complete replacement. By controlling the substitution ratio (x in Y2-xScxTi2O5S2 where 0 < x ≤ 2), the material maintains the fundamental Ruddlesden-Popper crystal structure stability while achieving the desired capacity improvement through localized compositional modification.
Solution Approach 2:
The invention carefully adjusts the compositional parameter x to optimize the balance between capacity and structural stability. The substitution ratio is controlled within a specific range (0 < x ≤ 2) to ensure that the crystal structure remains stable while achieving sufficient capacity improvement, demonstrating precise parameter control.
Data Source
AI summary
A battery active material includes a crystal phase that is represented by a formula Y2−xScxTi2O5S2 (where 0<x<2), and has a Ruddlesden-Popper structure.