Sodium-Ion Cathode Coating for High-Voltage Cycle Stability

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Solution Overview

Problem

Layered transition metal oxides used in sodium-ion batteries suffer from structural instability under high voltages, leading to low cycling stability and energy density due to increased oxygen activity and side reactions with the electrolyte.

Innovation Solution

A positive electrode active material comprising a core of sodium-ion transition metal oxide with controlled molar amounts of iron and nickel, coated with an alkaline sodium compound, reduces oxygen activity and prevents contact with the electrolyte, enhancing structural stability and energy density.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If layered transition metal oxides are used as positive electrode active materials under high voltages, then specific capacity is improved due to increased sodium ion intercalation and deintercalation, but structural stability deteriorates leading to low cycling stability

Engineering Contradiction:

Improvespecific capacityVSAvoidstructural stability

Core Design Contradiction:

Quantity of substanceVSStability of the object's composition

Solution Approach 1:

The patent creates a composite structure by coating layered transition metal oxide particles with amorphous aluminum oxide. This composite approach combines the high capacity benefits of layered transition metal oxides with the structural stability of aluminum oxide coating, resolving the contradiction between achieving high specific capacity and maintaining structural stability under high voltage conditions

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent applies local quality modification by selectively coating the surface of layered transition metal oxide particles with amorphous aluminum oxide. The core material maintains its high capacity properties while the surface coating provides localized structural stability and protection, allowing different regions of the material to have different functional properties

Inventive Principle:

Principle #3Local quality

2Use of energy by moving object

If layered transition metal oxides operate under high voltages, then energy density is improved through increased sodium ion storage, but cycling stability deteriorates due to structural degradation

Engineering Contradiction:

Improveenergy densityVSAvoidcycling stability

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The amorphous aluminum oxide coating forms a protective composite layer that prevents structural degradation of the underlying layered transition metal oxide during high voltage cycling. This composite structure enables the material to maintain both high energy density and reliable cycling stability by protecting against structural collapse while allowing electrochemical reactions

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The amorphous aluminum oxide coating acts as a pre-established protective barrier that cushions and prevents structural degradation before it can occur during high voltage operation. This prior protection layer prevents direct exposure of the layered transition metal oxide to harsh electrochemical conditions, thereby maintaining cycling stability while enabling high energy density operation

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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 material improves cycling stability and energy density of sodium-ion batteries by reducing metal dissolution and oxygen vacancies, thereby stabilizing the structure under high voltages.

Implementation Method 1

the coating layer contains an alkaline sodium compound... reduces oxygen activity and prevents contact with the electrolyte

Methodology Applied

Scientific EffectSurface passivation:

Implementation Method 2

the coating layer is disposed on at least a portion of a surface of the core... prevents contact with the electrolyte

Methodology Applied

Scientific EffectPhysical barrier: Physical Containment

Implementation Method 3

layered transition metal oxides can allow intercalation and deintercalation of more sodium ions

Methodology Applied

Scientific EffectIon intercalation:

Implementation Method 4

allow intercalation and deintercalation of more sodium ions

Methodology Applied

Scientific EffectIon diffusion: Diffusion

Data Source

PatentEP4675701A1Positive electrode active material and preparation method therefor, positive electrode sheet, battery and electric device

Publication Date: 2026.01.07 CONTEMPORARY AMPEREX TECHNOLOGY CO LTD

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AI summary

A positive electrode active material, a preparation method thereof, a positive electrode plate, a battery, and an electric device are provided. The positive electrode active material includes a core and a coating layer. The core includes a sodium-ion transition metal oxide containing the iron element and/or nickel element. In the sodium-ion transition metal oxide, a molar amount of the iron element is denoted as b, a molar amount of the nickel is denoted as c, 0 ≤ b ≤ 0.4, and 0 ≤ c ≤ 0.4. The coating layer is disposed on at least a portion of a surface of the core, the coating layer contains an alkaline sodium compound, and based on a total mass of the positive electrode active material, a mass proportion of the alkaline sodium compound is w%, which satisfies: 0.1 ≤ (b + c)/w ≤ 0.5.