Sodium-Ion Battery Coating Reduces Interface Impedance

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Solution Overview

Problem

Sodium-ion batteries face high interface impedance and alkaline materials that attack positive electrode adhesives, leading to poor rate capability and processing difficulties.

Innovation Solution

A positive electrode material with a sodium-ion layered oxide core coated by a spinel-type lithium salt layer, providing a three-dimensional diffusion channel and reducing alkalinity to enhance ion diffusion and adhesive stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If a layered positive electrode material is used in sodium-ion batteries, then high theoretical capacity and abundant sodium resources are achieved, but the interface impedance becomes relatively high resulting in poor rate capability

Engineering Contradiction:

Improvetheoretical capacityVSAvoidrate capability

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent applies local quality by coating only the surface of the layered positive electrode material with spinel-type lithium salt, rather than changing the bulk material properties. This surface modification locally enhances ion diffusion pathways at the critical electrode-electrolyte interface while preserving the high capacity bulk structure, thereby improving rate capability without sacrificing theoretical capacity

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent creates a composite material system combining layered positive electrode material (core) with spinel-type lithium salt (coating layer). This composite structure leverages the high capacity of the layered material and the superior ion conductivity of the spinel coating, achieving both high theoretical capacity and improved rate capability through synergistic material combination

Inventive Principle:

Principle #40Composite materials

2Quantity of substance

If layered positive electrode material is used, then high theoretical capacity is achieved, but the material is highly alkaline causing attack on positive electrode adhesives such as PVDF leading to gelation and processing difficulty

Engineering Contradiction:

Improvetheoretical capacityVSAvoidprocessing ease

Core Design Contradiction:

Quantity of substanceVSEase of manufacture

Solution Approach 1:

The spinel-type lithium salt coating acts as an intermediary layer between the highly alkaline layered positive electrode material and the PVDF adhesive. This intermediate coating reduces the direct contact and chemical interaction between the alkaline material and the adhesive, preventing gelation and processing difficulties while allowing the high capacity material to be effectively manufactured and processed

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If the coating layer thickness is increased to reduce interface impedance, then rate capability improves, but the thickness control becomes more difficult and may affect battery assembly

Engineering Contradiction:

Improverate capabilityVSAvoidcoating thickness control

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent optimizes the coating layer thickness to a specific range (50-500 nm) to balance rate capability improvement with manufacturing feasibility. This parameter optimization ensures sufficient coating to reduce interface impedance and improve ion diffusion, while maintaining thin enough thickness to be achievable through conventional coating processes and to avoid interference with battery assembly operations

Inventive Principle:

Principle #35Parameter changes

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 layer improves sodium-ion battery rate capability and cycle stability by reducing interface impedance and adhesive attack, while forming a dense SEI film for enhanced performance.

Implementation Method 1

the spinel-type lithium salt in the coating layer may provide a three-dimensional channel for sodium ion diffusion at the interface between the positive electrode material and the electrolyte, increasing the diffusion path and improving the diffusion rate

Methodology Applied

Scientific EffectIon diffusion: Diffusion

Implementation Method 2

the coating layer tightly coats the layered positive electrode material, which may reduce the contact interface between the layered positive electrode material and an electrolyte, alleviating the dissolution of metal ions, and improving the cycle performance of the battery

Methodology Applied

Scientific EffectSurface coating protection: Coatings

Implementation Method 3

allow the deintercalation of lithium ions from the positive electrode preceding over sodium ions during the formation process and to form a film at the negative electrode, forming a dense SEI film composed of lithium salt

Methodology Applied

Scientific EffectIon deintercalation and film formation: Electrolysis

Data Source

PatentEP4685866A1Positive electrode material, secondary battery and electric device

Publication Date: 2026.01.28 SUNWODA MOBILITY ENERGY TECHNOLOGY CO LTD

Figure 1

AI summary

A positive electrode material, a secondary battery and an electric device. The positive electrode material comprises an inner core and a coating layer arranged on a surface of the inner core, wherein the inner core comprises a sodium-ion layered oxide, and the coating layer comprises a spinel-type lithium salt. The spinel-type lithium salt is used for tightly coating the layered positive electrode material, thereby solving the problems of the interface impedance of the positive electrode materials of the existing sodium-ion battery being relatively large, and a positive electrode adhesive being prone to being attacked.