Silicon Shell Anode with Metal Silicide Core for Lithium Battery

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Solution Overview

Problem

Silicon anode active materials in lithium secondary batteries face issues with unstable solid electrolyte interface formation and rapid volume expansion during charging/discharging, leading to deteriorated electrochemical characteristics and shortened lifespan due to side reactions and internal stress.

Innovation Solution

A composite anode active material is developed, comprising a metal silicide core, a silicon shell, and a metal nitride and carbon material dispersed on the silicon shell, which suppresses side reactions with the electrolyte and mitigates volume expansion by providing a conductive pathway and physical binding, thereby improving electrochemical characteristics and durability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If a silicon material is used as an anode active material, then energy density is improved, but the material is pulverized due to rapid volume expansion during charging/discharging

Engineering Contradiction:

Improveenergy densityVSAvoidstructural integrity

Core Design Contradiction:

Use of energy by moving objectVSStrength

Solution Approach 1:

The silicon anode is divided into multiple small particles rather than using a single large piece. This segmentation allows each particle to independently expand and contract during lithium insertion/extraction, reducing internal stress and preventing pulverization while maintaining high energy density

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A carbon coating layer is applied on the surface of silicon particles to form a flexible shell structure. This shell accommodates volume changes during charging/discharging cycles, prevents direct contact between silicon and electrolyte, and maintains structural integrity while allowing lithium ion transport

Inventive Principle:

Principle #30Flexible shells and thin films

2Use of energy by moving object

If a silicon material is used as an anode active material, then energy density is improved, but side reactions with electrolyte occur forming unstable SEI layer

Engineering Contradiction:

Improveenergy densityVSAvoidelectrochemical stability

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

A carbon coating layer is introduced as an intermediary between silicon and electrolyte. This layer prevents direct contact and side reactions between silicon surface and electrolyte, forming a stable protective barrier that eliminates unstable SEI formation while allowing lithium ion diffusion

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The anode is designed as a composite structure combining silicon core with carbon shell and metal nitride coating. This composite material approach leverages the high capacity of silicon while the carbon and metal nitride components provide stability, preventing side reactions and improving electrochemical reliability

Inventive Principle:

Principle #40Composite materials

3Strength

If internal stress is reduced to prevent pulverization, then structural integrity is improved, but volume change during intercalation/deintercalation is not addressed

Engineering Contradiction:

Improvestructural integrityVSAvoidvolume change

Core Design Contradiction:

StrengthVSVolume of moving object

Solution Approach 1:

The carbon coating layer acts as a flexible shell that can expand and contract with the silicon core during lithium insertion/extraction. This flexible structure accommodates volume changes while maintaining structural integrity, preventing pulverization without restricting necessary volume expansion

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

Dividing silicon into multiple small particles reduces the overall volume change impact on the electrode structure. Each particle undergoes smaller individual volume changes, and the segmented structure allows for better stress distribution and accommodation during cycling

Inventive Principle:

Principle #1Segmentation

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 anode active material reduces volume change and side reactions, enhancing the lifespan and rate capabilities of lithium secondary batteries by maintaining stable electrical contact and preventing silicon particle pulverization.

Implementation Method 1

a metal nitride and a carbon material that are dispersed in at least one surface of the silicon shell

Methodology Applied

Scientific EffectSurface passivation: Adsorption

Implementation Method 2

volume change caused by intercalation/deintercalation of lithium ions is decreased

Methodology Applied

Scientific EffectVolume expansion mitigation: Composite Materials

Implementation Method 3

a metal silicide core, a silicon shell, and a metal nitride and a carbon material that are dispersed in at least one surface of the silicon shell

Methodology Applied

Scientific EffectPhysical bonding: Chemical Bonding

Data Source

PatentUS10164252B2Composite anode active material, method of preparing the same, and anode and lithium secondary battery including the composite anode active material

Publication Date: 2018.12.25 SAMSUNG ELECTRONICS CO LTD

AI summary

A composite anode active material includes a metal silicide core, a silicon shell, and a metal nitride and a carbon material that are dispersed in at least one surface of the silicon shell.