SiOx Anode with Amorphous Carbon Coating for Lithium Battery

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Solution Overview

Problem

Lithium secondary batteries face challenges with silicon-based anodes due to high volume expansion during lithium ion intercalation, leading to decreased capacity and potential separation from the current collector, while carbon-based anodes have limited capacity and reversibility.

Innovation Solution

An anode composed of SiOx (0<x≤1) and a carbon material with a surface coated with amorphous carbon, controlling the crystal orientation ratio between 0.07 and 0.17 to minimize thickness expansion and enhance initial discharge capacity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If a silicon-based material is used as the anode active material to increase capacity, then the charge and discharge capacity increases significantly, but the volume expansion during lithium ion intercalation causes capacity decrease and potential separation from current collector

Engineering Contradiction:

Improvecharge and discharge capacityVSAvoidcapacity retention and adhesion

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The silicon-based material particles are embedded within the carbon material matrix, forming a nested structure where the silicon particles are contained within the carbon framework. This nesting approach allows the silicon to expand and contract during lithium ion intercalation while being constrained by the carbon matrix, preventing separation from the current collector and maintaining capacity retention.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The invention uses a composite material system consisting of silicon-based material particles combined with carbon material. The silicon-based material provides high capacity, while the carbon material provides structural stability and prevents volume expansion. The composite structure synergistically combines the advantages of both materials to achieve high capacity with improved reliability.

Inventive Principle:

Principle #40Composite materials

2Reliability

If a carbon material is used as the anode active material to ensure small volume changes and excellent reversibility, then the stability and reversibility improve, but the capacity is limited and smaller than silicon-based materials

Engineering Contradiction:

Improvereversibility and volume stabilityVSAvoidcharge and discharge capacity

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The invention merges the carbon material with silicon-based material particles to create a composite anode structure. The carbon material provides the stable framework with excellent reversibility and small volume changes, while the silicon-based material particles dispersed within provide high capacity. This merging allows the anode to simultaneously achieve the stability of carbon and the high capacity of silicon.

Inventive Principle:

Principle #5Merging (Combining)

3Quantity of substance

If the silicon-based material undergoes volume expansion during lithium ion intercalation, then the capacity increases, but the thickness of the anode increases and may separate from the current collector

Engineering Contradiction:

ImprovecapacityVSAvoidthickness and adhesion

Core Design Contradiction:

Quantity of substanceVSLength of stationary object

Solution Approach 1:

The carbon material acts as a flexible shell or matrix that surrounds and constrains the silicon-based material particles. This carbon shell accommodates the volume expansion of silicon during lithium ion intercalation while maintaining the overall thickness of the anode and preventing separation from the current collector. The flexible carbon structure absorbs the expansion stress without causing delamination.

Inventive Principle:

Principle #30Flexible shells and thin films

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 solution stabilizes electrode density, improves initial discharge capacity, and reduces volume expansion, resulting in improved life characteristics and capacity retention of lithium secondary batteries.

Implementation Method 1

volume expansion of the silicon-based material during the intercalation of lithium ions is 3 times or more

Methodology Applied

Scientific EffectVolume expansion: Thermal Expansion

Implementation Method 2

during the intercalation of lithium ions

Methodology Applied

Scientific EffectIntercalation: Absorption (physical)

Implementation Method 3

silicon (Si) and tin (Sn), which exhibits a charge and discharge capacity higher than that of a carbon material and is electrochemically alloyable with lithium

Methodology Applied

Scientific EffectElectrochemical alloying: Chemical Bonding

Data Source

PatentEP2731179B1Anode comprising silicon-based material and carbon material, and lithium secondary battery comprising same

Publication Date: 2017.12.06 LG CHEM LTD

AI summary

The present invention relates to an anode comprising an anode active material which comprises SiOx (0<x≤1) and a carbon material having amorphous carbon coated on the surface thereof, and which has an orientation factor of 0.07 to 0.17. A lithium secondary battery comprising the anode of the present invention can have improved life span characteristics, low rate of change in thickness, and improved initial discharge capacity.