Monocrystalline Sodium-Ion Cathode for Fragmentation-Resistant Cycling
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Solution Overview
Problem
Sodium-ion batteries face challenges with poor cycle performance and low energy density due to factors like particle fragmentation, anisotropic volume expansion, and chemical interactions with the electrolyte, leading to instability and reduced electrochemical performance.
Innovation Solution
A mono-crystalline cathode material with a specific chemical composition (Na1+aNi1−x−y−zMnxFeyMzO2) is developed, featuring a stable crystal structure and morphology, which prevents particle fragmentation and reduces contact with the electrolyte, enhancing high-temperature and high-voltage cycle performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If transition metal oxides with high specific capacity are used as cathode materials, then the energy density is improved, but the cycle performance deteriorates due to particle fragmentation and structural instability
Solution Approach 1:
The patent changes the crystal structure parameter from polycrystalline to mono-crystalline, and optimizes the chemical composition parameters (Ni:Mn:Fe ratio) to achieve a balance between high capacity and structural stability during cycling
Solution Approach 2:
The patent creates a composite cathode material combining multiple transition metals (Ni, Mn, Fe) in specific ratios within a mono-crystalline structure, leveraging the high capacity of Ni while the stability of Mn and Fe prevents fragmentation
2Quantity of substance
If the amount of sodium removal from the cathode material is increased, then the capacity is improved, but the structural stability deteriorates leading to atomic rearrangement and phase change
Solution Approach 1:
The patent introduces different metal elements at specific lattice positions to create local structural reinforcement zones that prevent atomic rearrangement during extensive sodium removal
Solution Approach 2:
The mono-crystalline structure with optimized composition serves as a pre-established stable framework that cushions against structural collapse during high-level sodium extraction
3Use of energy by moving object
If the cathode material is desalted, then the oxidation property is enhanced, but the chemical stability deteriorates leading to interaction with electrolyte and dissolution of transition metals
Solution Approach 1:
The stable mono-crystalline structure acts as an intermediary framework that allows oxidation reactions to proceed while preventing direct contact and dissolution of transition metals with the electrolyte
4Ease of manufacture
If polycrystalline cathode materials are used, then the manufacturing process is simpler, but the electrochemical performance deteriorates due to connection structures between particles causing stress and current density increase
Solution Approach 1:
The patent segments the cathode material into individual mono-crystalline particles that do not form harmful connection structures, eliminating the stress concentration points present in polycrystalline aggregates
Data Source
AI summary
The present invention related to the technical field of sodium ion batteries, and particularly related to a mono-crystalline cathode material for sodium-ion battery and a preparation method and battery thereof. The mono-crystalline cathode material for sodium-ion battery has a chemical composition formula of Na1+aNi1−x−y−zMnxFeyMzO2, wherein −0.40≤a≤0.25, 0.08≤x≤0.5, 0.05≤y≤0.5, 0≤z≤0.26, the M is one or a combination of two or more selected from the group consisting of Ti, Zn, Co, Mn, Al, Zr, Y, Ca, Li, Rb, Cs, W, Ce, Mo, Ba, Mg, Ta, Nb, V, Sc, Sr, B, F, P or Cu elements. The mono-crystalline cathode material for sodium-ion battery has a specific chemical composition, a mono crystal morphology and good structural stability and integrity. Particle fragmentation can not be produced in the cyclic process, and meanwhile, the cyclic stability of the sodium-ion battery can be improved.