Polyanionic Coated Sodium-Ion Cathode for Air Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Layered transition metal oxides used in sodium-ion secondary batteries suffer from low air stability, leading to impaired electrochemical performance when stored in humid environments.
Innovation Solution
A positive electrode material comprising a matrix material Na x Ni a Fe b Mn c M d O 2 with a surface coating of polyanionic materials such as phosphate, NASICON, pyrophosphate, or fluorinated phosphate compounds, controlled within specific mass and pH ranges, enhances stability and reduces contact areas with air and electrolyte, improving specific capacity and electrochemical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If layered transition metal oxides are used as positive electrode material, then energy density is improved, but air stability deteriorates
Solution Approach 1:
The patent uses a composite structure where layered transition metal oxide core particles are coated with polyanionic material shell. This composite design allows the core to provide high energy density while the shell provides air stability, resolving the contradiction between energy density and stability.
Solution Approach 2:
The polyanionic material forms a thin film coating on the surface of the layered transition metal oxide particles. This thin film shell protects the core material from air exposure while maintaining the electrochemical performance, thus improving air stability without significantly compromising energy density.
2Stability of the object's composition
If polyanionic material coating is applied to matrix material surface, then air stability is improved, but specific surface area decreases
Solution Approach 1:
The patent employs a thin film coating of polyanionic material on the particle surface. The thin film provides adequate protection against air exposure while minimizing the reduction in specific surface area, thus balancing air stability improvement with surface area preservation.
Solution Approach 2:
The polyanionic material coating is applied selectively on the particle surface rather than bulk modification. This localized coating approach provides air stability where needed (at the surface) while preserving the bulk properties and specific surface area of the layered transition metal oxide.
3Stability of the object's composition
If coating rate of polyanionic material is increased, then air stability is improved, but electrochemical performance may deteriorate
Solution Approach 1:
The patent optimizes the coating rate parameter of polyanionic material to a specific range (5-30 wt%). This parameter optimization ensures sufficient air stability while maintaining adequate electrochemical performance by preventing excessive coating that would hinder ion and electron transport.
Solution Approach 2:
The polyanionic material coating provides protection primarily at the particle surface where air exposure occurs. The coating is designed to be thin enough to allow ion and electron transport while providing sufficient surface protection, achieving local quality enhancement without compromising overall electrochemical performance.
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 proposed electrode material improves air stability, reduces gas production, and enhances specific capacity and cycle performance of sodium-ion secondary batteries, achieving higher energy density and electrochemical efficiency.
Implementation Method 1
A surface of the matrix material includes a polyanionic material
Implementation Method 2
sodium-ion secondary battery
Data Source
Figure 1~2
Figure 3
AI summary
This application provides a positive electrode material, a positive electrode plate, a sodium-ion secondary battery, and an electrical device. The positive electrode material includes a matrix material NaxNiaFebMncMdO2. A surface of the matrix material includes a polyanionic material. The polyanionic material includes at least one of a phosphate compound, a NASICON compound, a pyrophosphate compound, or a fluorinated phosphate compound. In the matrix material NaxNiaFebMncMdO2, M includes at least one of Co, Mg, Ca, B, Al, Zr, Ti, W, Mo, Cr, Sr, Y, Cd, Sn, Sb, Ce, Li, K, Zn, La, F, Si, or P, 0.7 ≤ x < 1.0, 0.2 < a ≤ 0.5, 0.2 < b ≤ 0.5, 0.2 < c ≤ 0.7, 0 ≤ d ≤ 0.2, 0.7 ≤ x/(a + b + c + d) < 1.0. Based on a mass of the positive electrode material, a mass percent of the polyanionic material is 1% to 10%. The positive electrode material in the secondary battery provided herein satisfies the above characteristics, and can improve the electrochemical performance of the sodium-ion secondary battery.