Boron-Doped Graphene Anode for Sodium-Ion Batteries

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Solution Overview

Problem

Current sodium-ion batteries lack a suitable anode material that offers high energy density, good cyclability, and safety, with existing materials like hard carbon posing safety concerns due to low sodiation voltage and alloy anodes experiencing volume expansion issues.

Innovation Solution

A boron-doped graphene sheet is used as the anode active material in sodium-ion batteries, providing high energy density, stable sodiation voltage, and minimal volume change during cycling, with sodium adsorption capabilities up to 762 mAh/g and sodiation voltage of 0.44 V.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If hard carbon is used as anode material, then capacity is improved (300 mAh/g), but safety deteriorates due to low sodiation voltage causing dendrite formation

Engineering Contradiction:

ImprovecapacityVSAvoiddendrite formation

Core Design Contradiction:

Quantity of substanceVSObject-affected harmful factors

Solution Approach 1:

The invention changes the sodiation voltage parameter from 0.01V (hard carbon) to 0.2-0.4V (boron-doped graphene) by modifying the anode material composition with boron doping, thereby eliminating dendrite formation while maintaining high capacity

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention uses boron-doped graphene as a composite anode material that combines the high capacity characteristics of carbon-based materials with the elevated sodiation voltage properties introduced by boron doping, resolving the contradiction between capacity and safety

Inventive Principle:

Principle #40Composite materials

2Quantity of substance

If alloy anodes (Sn, Sb) are used, then capacity is improved, but reliability deteriorates due to volume expansion causing pulverization

Engineering Contradiction:

ImprovecapacityVSAvoidcyclability

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The invention uses graphene's two-dimensional sheet structure as a flexible framework that can accommodate volume changes during sodium insertion/extraction, preventing pulverization while maintaining high capacity and excellent cyclability

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The invention changes the volume expansion parameter by using boron-doped graphene's stable crystal structure, which maintains dimensional stability during cycling compared to alloy anodes, thereby improving reliability while preserving capacity

Inventive Principle:

Principle #35Parameter changes

3Use of energy by moving object

If graphite is used as anode material, then energy density is improved, but adaptability deteriorates because it cannot accommodate Na insertion beyond Na0.0625C6

Engineering Contradiction:

Improveenergy densityVSAvoidsodium insertion capacity

Core Design Contradiction:

Use of energy by moving objectVSAdaptability or versatility

Solution Approach 1:

The invention changes the maximum sodium insertion concentration parameter from Na0.0625C6 (graphite) to Na0.625C6 (boron-doped graphene) through boron doping, achieving both high energy density and full adaptability to sodium-ion batteries

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention creates a boron-doped graphene composite material that combines the structural advantages of graphite with enhanced sodium insertion capacity, simultaneously improving energy density and adaptability to sodium-ion systems

Inventive Principle:

Principle #40Composite materials

4Ease of operation

If intercalation materials (titanate) are used, then sodiation voltage is improved (0.3V), but capacity deteriorates (less than 300 mAh/g)

Engineering Contradiction:

Improvesodiation voltageVSAvoidcapacity

Core Design Contradiction:

Ease of operationVSQuantity of substance

Solution Approach 1:

The invention optimizes the sodiation voltage parameter to 0.2-0.4V (improved from 0.01V) while simultaneously achieving high capacity of 300-420 mAh/g through boron doping, unlike titanate which shows inverse relationship between voltage and capacity

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 boron-doped graphene sheet anode achieves higher energy density and improved safety compared to traditional materials, maintaining electronic and sodium mobility, and exhibits excellent rate capability and cyclability, addressing the limitations of existing sodium-ion battery anodes.

Implementation Method 1

sodium adsorption capabilities up to 762 mAh/g

Methodology Applied

Scientific EffectAdsorption: Adsorption

Implementation Method 2

boron-doped graphene sheet

Methodology Applied

Scientific EffectDoping: Dopants

Data Source

PatentUS11075381B2Boron-doped graphene sheet as sodium-ion battery anode

Publication Date: 2021.07.27 TOYOTA JIDOSHA KK

AI summary

A sodium-ion battery having a boron-doped graphene sheet as an anode active material is provided. The boron-doped graphene sheet is of formula BxCy, where x and y satisfy a relation of x+y=4, and x is a number larger than 0 and less than or equal to 1.