Coated Sodium-Ion Cathode Material for Stable Cycle Performance
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Solution Overview
Problem
Lithium-ion batteries face challenges due to the scarcity of lithium resources, rising prices, and poor cycle performance of sodium-ion batteries resulting from the instability of their positive electrode active materials.
Innovation Solution
A positive electrode active material is developed with a core composed of NaxRy(PO4)z(P2O7)k coated with a first layer of MaOb and optionally a second layer of carbon, where M includes elements like Ca, Bi, Ba, Ti, Al, Nb, Mg, Fe, Cu, Zn, Mn, or Co, to enhance environmental stability and reduce side reactions with moisture and electrolyte.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sodium-ion battery uses an existing positive electrode active material, then it can implement charging and discharging by using a deintercalation process of sodium ions, but the stability of the positive electrode active material is poor resulting in low cycle performance
Solution Approach 1:
The patent applies composite materials by creating a core-shell structure where the core is NaxRy(PO4)z(P2O7)k and the shell is MaOb coating layer. This composite structure combines the high capacity characteristics of the polyanionic phosphate core with the stability and protection provided by the oxide shell, resolving the contradiction between achieving good cycle performance and maintaining material stability.
Solution Approach 2:
The patent uses a thin film coating approach by forming a MaOb coating layer on the surface of the positive electrode active material core. This thin film shell provides protection against moisture and electrolyte while maintaining the electrochemical performance, thereby improving both stability and cycle performance without significantly increasing material volume.
2Productivity
If the positive electrode active material is exposed to air and electrolyte, then it can undergo electrochemical reactions, but side reactions with moisture and electrolyte occur reducing material stability
Solution Approach 1:
The MaOb coating layer serves as an intermediary between the positive electrode active material core and the external environment (moisture and electrolyte). It acts as a protective barrier that prevents harmful side reactions while allowing ionic transport, thus protecting the core material from degradation without completely isolating it from necessary electrochemical interactions.
Solution Approach 2:
The MaOb coating layer creates an inert protective environment around the reactive NaxRy(PO4)z(P2O7)k core, shielding it from harmful interactions with moisture and electrolyte. This inert shell allows the core to maintain its electrochemical activity while being protected from degradation by external harmful factors.
3Stability of the object's composition
If a coating layer is added to improve stability, then environmental stability and moisture resistance improve, but the complexity of material preparation increases
Solution Approach 1:
The patent applies preliminary action by forming the MaOb coating layer on the positive electrode active material core before the material is fully assembled into the battery. This pre-coating approach ensures that the material is stabilized against environmental factors and moisture from the outset, preventing degradation before the material is put into service.
Solution Approach 2:
The patent merges the coating process with the material synthesis process by forming the MaOb coating layer during or after the core material formation. This integration combines what could be separate steps into a unified process, reducing overall preparation complexity while still achieving the protective function.
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 coating improves the cycle performance and maintains high first-cycle Coulombic efficiency of sodium-ion batteries by reducing contact with moisture and electrolyte, stabilizing the interface, and enhancing conductivity.
Implementation Method 1
The first coating layer including MaOb is formed on the at least a part of the core including NaxRy(PO4)z(P2O7)k... The first coating layer may reduce contact between the core and H2O, CO2, and the like in air, to improve environmental stability and moisture resistance of the material
Implementation Method 2
the first coating layer may reduce a side reaction between a surface of the core and an electrolyte solution, stabilize an interface between the positive electrode active material and the electrolyte solution, and improve stability of the material
Data Source
AI summary
A positive electrode active material, a method for preparing a positive electrode active material, a positive electrode plate, a battery, and a power consuming apparatus. The positive electrode active material includes a core and a first coating layer. The core includes NaxRy(PO4)z(P2O7)k. 1≤x≤7. 1≤y≤4. 1≤z≤4. 1≤k≤4. R includes at least one of Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Sn, Hf, Ta, W, or Pb. The first coating layer is formed on at least a part of the core. The first coating layer includes MaOb. M includes at least one of Ca, Bi, Ba, Ti, Al, Nb, Mg, Fe, Cu, Zn, Mn, Ni, or Co. 1≤a≤7. 1≤b≤12.