Silicon-Graphene Composite Electrode for Lithium Battery

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Solution Overview

Problem

Silicon-based negative electrodes in lithium batteries face issues with volume expansion leading to electrical isolation and electrolyte decomposition, resulting in reduced battery efficiency and lifespan due to the lack of effective solutions for managing volume expansion and side reactions.

Innovation Solution

A composite material is developed comprising a carbonaceous material with silicon structures coated on it, and a graphene layer on the silicon structures, where the silicon oxide layer acts as a seed for forming graphene, anchoring the silicon structures without using a binder, thereby preventing delamination and volume expansion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If silicon is used as negative electrode material, then theoretical capacity is high and cost is low, but volume expansion occurs during discharge leading to electrical isolation and electrolyte decomposition

Engineering Contradiction:

Improvetheoretical capacityVSAvoidelectrical isolation

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent employs a multi-layer nested structure where silicon structures are embedded within a carbonaceous material matrix, which is further coated with a graphene layer. This nested configuration allows silicon to expand and contract during charge-discharge cycles while remaining mechanically connected to the conductive network, preventing electrical isolation despite volume changes.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The patent creates a composite structure combining silicon, carbonaceous material, and graphene. The silicon provides high capacity, the carbonaceous material provides structural stability and conductivity, and the graphene coating enhances electrical conductivity and prevents electrolyte decomposition. This composite approach resolves the contradiction by combining materials with complementary properties.

Inventive Principle:

Principle #40Composite materials

2Stability of the object's composition

If volume expansion of silicon is reduced, then pulverization phenomenon decreases, but battery charging/discharging efficiency remains unsatisfactory with available silicon materials

Engineering Contradiction:

Improvepulverization resistanceVSAvoidcharging/discharging efficiency

Core Design Contradiction:

Stability of the object's compositionVSProductivity

Solution Approach 1:

The patent uses a graphene layer as a flexible thin film coating on the silicon structures. Graphene's exceptional mechanical flexibility allows it to accommodate silicon's volume expansion and contraction during charge-discharge cycles without cracking or delaminating, maintaining both structural stability and electrical conductivity for high charging/discharging efficiency.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The carbonaceous material acts as an intermediary between silicon and the external environment. It provides a compliant interface that mediates the mechanical stress of volume expansion, preventing direct contact between expanding silicon and rigid structures that would cause pulverization, while maintaining electrical pathways for efficient charge transfer.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 composite material enhances the conductivity and capacity of the battery, reduces volume expansion, and improves the battery's flexibility and lifespan by acting as a protective layer against electrolyte reactions, without the need for additional binders or conducting agents.

Implementation Method 1

a graphene layer, which comprises graphene and is disposed on the plurality of silicon structures

Methodology Applied

Scientific EffectChemical vapor deposition: Chemical Vapour Deposition

Implementation Method 2

a graphene layer, which comprises graphene and is disposed on the plurality of silicon structures, wherein a silicon structure of the plurality of silicon structures includes silicon, and a silicon oxide of the formula SiOx which is disposed on a surface of the silicon

Methodology Applied

Scientific EffectPhysical constraint: Physical Containment

Data Source

PatentUS9917298B2Composite, method of preparing the same, electrode including the composite, and lithium battery including the electrode

Publication Date: 2018.03.13 SAMSUNG ELECTRONICS CO LTD

AI summary

A composite includes a carbonaceous material; a plurality of silicon structures disposed on the carbonaceous material; and a graphene layer, which comprises graphene and is disposed on the plurality of silicon structures, wherein a silicon structure of the plurality of silicon structures includes silicon and a silicon oxide of the formula SiOx which is disposed on a surface of the silicon, wherein 0<x<2. Also a method of preparing the composite, an electrode including the composite, and a lithium battery including the electrode.