Sodium Secondary Battery Electrode Conductivity and Density Optimization

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Solution Overview

Problem

Sodium secondary batteries with sodium-containing transition metal compounds and conductive materials often exhibit low charge-discharge efficiency and rapid deterioration in charge-discharge cycle characteristics, leading to reduced battery life and capacity.

Innovation Solution

A sodium secondary battery electrode with a current collector and an electrode mixture containing a sodium-containing transition metal compound, a conductive carbon material with a BET specific surface area of 10 m^2/g or more, and a binder with a structural unit derived from vinylidene halide, achieving conductivity of 5.0×10−3 S/cm or more and density of 1.6 g/cm3 or more.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conductive material is added to improve conductivity, then conductivity is improved, but charge-discharge efficiency deteriorates

Engineering Contradiction:

Improvecharge-discharge efficiencyVSAvoidconductivity

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent changes the physical parameters of the conductive material by specifying a minimum BET specific surface area of 10 m²/g, which fundamentally alters how the conductive material interacts with the electrolyte and active material, thereby improving charge-discharge efficiency while maintaining adequate conductivity

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite electrode mixture where carbon materials with specific surface area properties work synergistically with the sodium-containing transition metal compound and binder, achieving both good conductivity and high charge-discharge efficiency through the composite effect

Inventive Principle:

Principle #40Composite materials

2Quantity of substance

If the electrode mixture density is increased, then energy density is improved, but charge-discharge cycle characteristic deteriorates

Engineering Contradiction:

Improveenergy densityVSAvoidcharge-discharge cycle characteristic

Core Design Contradiction:

Quantity of substanceVSDuration of action of stationary object

Solution Approach 1:

The patent specifies a minimum density of 1.6 g/cm³ for the electrode mixture, optimizing the packing density and porosity balance to achieve high energy density while preventing structural degradation during cycling, thus maintaining good cycle characteristics

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The composite electrode mixture with optimized composition ratios achieves both high density and good cycle stability through the synergistic interaction of components, where the carbon material and binder work together to maintain structural integrity during repeated expansion and contraction

Inventive Principle:

Principle #40Composite materials

Data Source

PatentUS9972842B2Sodium secondary battery electrode and sodium secondary battery

Publication Date: 2018.05.15 TOYOTA JIDOSHA KK

AI summary

A sodium secondary battery electrode having an collector and an electrode mixture containing an electrode active material, a conductive material, and a binder, and wherein: the electrode active material has a sodium-containing transition metal compound, the conductivity of the electrode mixture is 5.0×10−3 S/cm or more, and the density of the electrode mixture is 1.6 g/cm3 or more.