Crystalline Silicon Anode Structure for Stable Solid-State Capacity

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Solution Overview

Problem

Conventional lithium-ion batteries with liquid electrolytes have low energy density and are prone to stability issues due to the use of silicon anodes, which expand and contract significantly, leading to particle cracking and reduced capacity, while solid-state batteries with silicon anodes face challenges in achieving the theoretical maximum capacity and require post-processing that decreases energy density.

Innovation Solution

A silicon anode composed of 99 wt% crystalline Si, with a plate-like shape and controlled surface roughness, is used in a solid-state battery, eliminating the need for a binder and ensuring efficient lithium ion insertion and removal, and incorporating a sulfide-based solid electrolyte to enhance mechanical and electrochemical stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If silicon is used as an anode material to increase theoretical maximum capacity, then energy density is improved, but volume expansion reaches approximately 280% causing particle cracking and reduced lifespan

Engineering Contradiction:

Improveenergy densityVSAvoidlifespan

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent applies a thin film coating on silicon particles that acts as a flexible protective shell. This coating allows the silicon to expand and contract during lithium insertion/extraction cycles without cracking, thereby maintaining particle integrity and extending battery lifespan while preserving the high capacity benefits of silicon.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The patent creates a composite structure by combining silicon particles with a coating material. This composite approach allows the silicon to provide high capacity while the coating material provides structural stability and crack prevention, resolving the contradiction between energy density and lifespan.

Inventive Principle:

Principle #40Composite materials

2Reliability

If post-processing coating is applied to silicon particles to extend lifespan, then reliability is improved, but weight and volume increase causing energy capacity and density to decrease

Engineering Contradiction:

ImprovelifespanVSAvoidenergy density

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent uses an ultrathin film coating that provides sufficient protection against particle cracking while minimizing the added weight and volume. This thin film approach extends lifespan without significantly compromising energy density, unlike thicker conventional coatings.

Inventive Principle:

Principle #30Flexible shells and thin films

3Quantity of substance

If conventional silicon anode with liquid electrolyte is used, then theoretical maximum capacity can be achieved, but silicon particles crack and fall apart over long period causing electrons to no longer be transferred

Engineering Contradiction:

ImprovecapacityVSAvoidcycle stability

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The thin film coating acts as a protective barrier that prevents particle cracking during repeated expansion and contraction cycles. This maintains particle integrity and ensures continuous electron transfer pathways, thereby improving cycle stability while preserving high capacity.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The coating film serves as an intermediary layer between the silicon particles and the external environment. It mediates the mechanical stress during volume changes and protects the silicon particles from direct damage, enabling long-term operational stability.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Reliability

If silicon anode is used in solid-state battery, then safety from external shocks is improved, but maximum capacity reported is only approximately 4 mAh/cm2 at room temperature

Engineering Contradiction:

ImprovesafetyVSAvoidcapacity

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The thin film coating enables the silicon anode to maintain structural integrity during volume changes in solid-state batteries. This allows the battery to achieve higher capacities by using silicon's full theoretical capacity without the particle cracking issues that previously limited performance.

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 silicon anode achieves a capacity of 10 mAh/cm2 or more, maintains mechanical stability, and increases energy density without binders, while the solid electrolyte absorbs volume changes, resulting in improved cycle life and efficiency.

Implementation Method 1

the silicon anode expands and contracts as lithium is repeatedly inserted and removed, and the maximum volume expansion reaches approximately 280%

Methodology Applied

Scientific EffectVolume expansion/contraction: Thermal Expansion

Implementation Method 2

as lithium is repeatedly inserted and removed

Methodology Applied

Scientific EffectIon insertion/removal: Diffusion

Data Source

PatentUS20250336960A1Silicon anode for solid-state battery and solid-state battery comprising the same

Publication Date: 2025.10.30 SEOUL NATIONAL UNIVERSITY R&DB FOUNDATION

AI summary

The present invention relates to a silicon anode for a solid-state battery including Si atoms of 99 wt % or more and composed of crystalline Si.