Polyanionic Cathode Composition for Sodium-Ion Capacity and Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current sodium-ion battery positive electrode materials exhibit limitations such as poorer stability and lower specific capacity, hindering the performance of sodium-ion secondary batteries.
Innovation Solution
A polyanionic compound with the chemical formula Na2+xMn1−yMySi2−zM′zO6−tNkXpYq is developed, featuring a novel composition and structure, which includes doping with elements like Ni, Fe, Cu, Zn, Mg, Al, Ge, Sn, Ti, S, Se, F, and Cl, resulting in improved structural stability and high sodium content, enhancing specific capacity and cycling stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional positive electrode materials (oxides, fluorides, sulfides, phosphates, pyrophosphates) are used, then manufacturing cost is reduced and safety is improved, but specific capacity and cycling stability deteriorate
Solution Approach 1:
The patent uses composite materials by combining multiple elements (Mn, Ni, Fe, Cu, Zn, Mg, Al, Ge, Sn, Ti, S, Se, F, Cl) to form a polyanionic compound with formula Na2+xMn1−yMySi2−zM′zO6−tNkXpYq. This composite approach creates a material that simultaneously achieves high specific capacity (200-400 mAh/g) and excellent cycling stability (retention rate >80% after 500 cycles), resolving the contradiction between capacity and stability in conventional materials.
Solution Approach 2:
The patent applies local quality by strategically doping specific elements at specific sites within the crystal structure. The formula Na2+xMn1−yMySi2−zM′zO6−tNkXpYq shows that different elements (M, M′, X, Y) are incorporated at different positions to locally enhance properties: Mn provides capacity, while doped elements like Ni, Fe, and Ge locally strengthen structural stability, achieving both high capacity and stability simultaneously.
2Reliability
If polyanionic compound with doping elements is used, then specific capacity and cycling stability are improved, but structural complexity increases
Solution Approach 1:
The patent uses parameter changes by systematically varying the doping ratios of multiple elements in the formula Na2+xMn1−yMySi2−zM′zO6−tNkXpYq. By optimizing parameters such as the total doping amount (y+z), individual element ratios, and oxidation states, the patent achieves high cycling stability (>80% retention after 500 cycles) while managing structural complexity through controlled compositional variation rather than uncontrolled complexity.
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 polyanionic compound provides secondary batteries with improved specific capacity and excellent cycling stability, maintaining structural integrity during sodium ion intercalation and deintercalation, thereby increasing capacity extraction and retention.
Implementation Method 1
the polyanionic compound provides secondary batteries with improved specific capacity and excellent cycling stability, maintaining structural integrity during sodium ion intercalation and deintercalation
Data Source
AI summary
A polyanionic compound has the following chemical formula: Na2+xMn1−yMySi2−zM′zO6−tNkXpYq(1), where in formula (1), M is selected from Ni, Fe, Cu, Zn, Mg, Al, or a combination thereof, M′ is selected from Ge, Sn, Ti, or a combination thereof, X is selected from S, Se, or a combination thereof, and Y is selected from F, Cl, or a combination thereof, where −0.2<x<0.2, 0≤y<0.1, 0≤z<0.1, 0≤t≤0.5, 0≤2t/3, 0≤p≤t, 0≤q≤t/2, and k+½p+ 3/2q=t.