Carbon-Coated Sodium Cathode Material for High-Rate Conductivity

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Solution Overview

Problem

The low electronic conductivity of Na3V2(PO4)2F3 material limits its ability to achieve cotransport of electrons and ions at high current density, affecting the full utilization of battery performance.

Innovation Solution

A carbon material with an ID/IG value of 0.9 to 1 is used to coat the surface of a core material, enhancing electronic conductivity and structural stability, thereby improving rate and cycle performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If carbon coating is applied to improve electronic conductivity, then electronic conductivity is improved, but the carbon structure becomes amorphous which limits the improvement

Engineering Contradiction:

Improveelectronic conductivityVSAvoidcarbon structure order

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent changes the key parameter of carbon structure by controlling the ID/IG ratio to be greater than 0.9, transforming the carbon coating from amorphous to highly ordered structure. This parameter change enables the carbon coating to provide both high electronic conductivity and structural stability, resolving the contradiction between improving conductivity and maintaining composition stability.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite material system consisting of Na3V2(PO4)2F3 core material combined with highly ordered carbon coating. This composite structure leverages the advantages of both materials: the core provides high voltage and ion diffusion capability, while the ordered carbon coating provides excellent electronic conductivity and structural stability, together resolving the conductivity limitation.

Inventive Principle:

Principle #40Composite materials

2Power

If high current density is used to achieve high rate performance, then power output is improved, but the low electronic conductivity limits the cotransport of electrons and ions

Engineering Contradiction:

Improverate performanceVSAvoidelectron-ion cotransport capability

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The composite material structure with highly ordered carbon coating provides excellent electronic conductivity that enables efficient electron transport even at high current densities. This resolves the contradiction by providing the necessary conductivity infrastructure to support high power output while maintaining effective electron-ion cotransport capability.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent applies high-quality ordered carbon coating locally on the surface of the core material, creating a specialized conductive interface layer. This local quality enhancement at the surface ensures optimal electron transport conditions exactly where needed for high rate performance, while the bulk material maintains its ion diffusion characteristics.

Inventive Principle:

Principle #3Local quality

3Ease of manufacture

If amorphous carbon coating is used, then preparation is simple, but the electronic conductivity improvement is limited

Engineering Contradiction:

Improvepreparation simplicityVSAvoidelectronic conductivity

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent maintains preparation simplicity while changing the carbon structure parameter by controlling the ID/IG ratio during the carbothermal reduction process. By adjusting process parameters such as carbon source selection and heating conditions, the method achieves highly ordered carbon structure without adding complex preparation steps, thus resolving the contradiction between ease of manufacture and electronic conductivity.

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 carbon-coated Na3V2(PO4)2F3 material achieves high rate performance and long cycle life by facilitating electron and ion transport, maintaining high specific capacity and energy density.

Implementation Method 1

a carbon material with a highly ordered atomic arrangement... effectively improve electronic conductivity... facilitating electron and ion transport

Methodology Applied

Scientific EffectElectron transport: Conduction (electrical)

Implementation Method 2

an ID/IG value of a Raman spectrum of the carbon material... a Raman shift of the D peak ranges from 1300 cm−1 to 1360 cm−1, and a Raman shift of the G peak ranges from 1580 cm−1 to 1600 cm−1

Methodology Applied

Scientific EffectRaman scattering: Scattering

Data Source

PatentUS20260022028A1Sodium battery positive electrode material and preparation method therefor, positive electrode sheet and sodium battery

Publication Date: 2026.01.22 BYD CO LTD

AI summary

Provided are sodium battery positive electrode materials and preparation methods therefor, positive electrode sheets and sodium batteries. The positive electrode materials may comprise a core and a coating layer coating the surface of the core, where the general molecular formula of the core comprises Na3V2-xMx(PO4)2F3, wherein M represents a doping element capable of replacing V, element M comprises at least one of Fe, Cr, Mn, Co, Ti, Ni, Cu, Zn, Mo, Nb, Zr, La and Ce, and 0≤x<0.2. The material for the coating layer comprises a carbon material, wherein the ID/IG value of a Raman spectrum of the carbon material is y, and 0.9≤y<1. ID/IG is the peak intensity ratio of peak D to peak G of the Raman spectrum of the carbon material, a Raman shift of peak D ranges from 1300 cm−1 to 1360 cm−1, and a Raman shift of peak G ranges from 1580 cm−1 to 1600 cm−1.