Polyanion-Coated Sodium Cathode Material for Air-Stable High Energy Density

Resolve Bottlenecks,
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 NaxNiaFebMncMdO2 with a polyanionic material coating, such as phosphate, NASICON, pyrophosphate, or fluorinated phosphate compounds, controlled within specific ranges to enhance stability and reduce contact areas with air and electrolyte, improving specific capacity and electrochemical performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If layered transition metal oxides are used as positive electrode material to achieve high energy density, then the energy density is improved, but the air stability deteriorates when stored in humid environments

Engineering Contradiction:

Improveenergy densityVSAvoidair stability

Core Design Contradiction:

Use of energy by moving objectVSStability of the object's composition

Solution Approach 1:

The patent uses a composite structure where layered transition metal oxide particles are coated with polyanionic material particles. This composite design allows the core material to maintain high energy density while the outer coating layer provides air stability and protects against humidity, effectively resolving the contradiction between energy density and air stability.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent applies a thin film coating of polyanionic material on the surface of the layered transition metal oxide particles. This thin film acts as a protective shell that maintains air stability without significantly increasing particle size or reducing the energy density of the core material.

Inventive Principle:

Principle #30Flexible shells and thin films

2Productivity

If the specific surface area of the positive electrode material is increased to improve contact with electrolyte, then the electrochemical performance is improved, but the contact area with air increases leading to increased hygroscopicity

Engineering Contradiction:

Improveelectrochemical performanceVSAvoidhygroscopicity

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The composite structure with polyanionic material coating allows the core material to maintain high specific surface area for good electrochemical performance while the outer coating layer provides a barrier against moisture absorption, thus resolving the contradiction between electrochemical performance and hygroscopicity.

Inventive Principle:

Principle #40Composite materials

3Stability of the object's composition

If a polyanionic material coating is applied to improve air stability, then the air stability is improved, but the contact area with electrolyte is reduced

Engineering Contradiction:

Improveair stabilityVSAvoidelectrochemical performance

Core Design Contradiction:

Stability of the object's compositionVSProductivity

Solution Approach 1:

The patent uses a thin film coating approach where the polyanionic material layer is sufficiently thin to provide air stability and moisture protection while remaining transparent or minimally obstructive to electrolyte penetration, thus maintaining electrochemical performance while improving air stability.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The composite design with optimized coating thickness and composition allows the polyanionic material layer to provide protective functions without creating a significant barrier to electrolyte access, balancing air stability with electrochemical performance.

Inventive Principle:

Principle #40Composite materials

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 material improves air stability, reduces gas production, and enhances specific discharge capacity, cycle performance, and energy density of sodium-ion secondary batteries.

Implementation Method 1

A surface of the matrix material includes a polyanionic material... the contact area between the positive electrode material and air is reduced, thereby reducing the hygroscopicity of the positive electrode material

Methodology Applied

Scientific EffectAdsorption: Adsorption

Implementation Method 2

sodium-ion secondary battery... electrochemical properties similar to those of lithium-ion batteries... specific discharge capacity, cycle performance

Methodology Applied

Scientific EffectElectrochemical reactions: Redox Reactions

Data Source

PatentUS20260045490A1Positive electrode material, positive electrode plate, sodium-ion secondary battery, and electrical device

Publication Date: 2026.02.12 NINGDE AMPEREX TECHNOLOGY LTD

AI summary

A positive electrode material includes a matrix material NaxNiaFebMncMdO2. A surface of the matrix material includes a polyanionic material. A 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%.