Silicon Composite Anode Coating for Stable Solid-State Battery Interfaces

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Solution Overview

Problem

All-solid-state batteries face issues with interfacial resistance and capacity fade due to the volume change of silicon-based negative electrode active materials during charging and discharging, leading to poor durability and output characteristics.

Innovation Solution

A composite anode active material with a core-shell structure is developed, where the ratio of the Young's modulus of the solid electrolyte to the thickness of the coating layer and the thickness of the coating layer to the particle diameter of the negative electrode active material are adjusted within specific ranges to minimize interfacial cracks and improve lithium-ion conductivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If silicon-based negative electrode active material is used to achieve high energy density, then capacity is improved, but volume change during charging and discharging causes interfacial cracks and capacity fade

Engineering Contradiction:

ImprovecapacityVSAvoiddurability

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

A coating layer containing solid electrolyte is formed on the surface of the silicon-based negative electrode active material before battery operation. This coating layer acts as a cushioning layer that accommodates the volume expansion and contraction of silicon during charging and discharging cycles, preventing interfacial cracks from forming between the active material and the solid electrolyte layer, thereby maintaining both high capacity and long-term durability

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The invention creates a composite structure consisting of silicon-based negative electrode active material particles coated with a solid electrolyte-containing coating layer. This composite structure combines the high capacity benefits of silicon with the protective and conductive properties of the solid electrolyte coating, enabling simultaneous achievement of high energy density and improved reliability through the synergistic interaction between the two materials

Inventive Principle:

Principle #40Composite materials

2Reliability

If coating layer thickness is increased to prevent interfacial cracks, then durability is improved, but interfacial resistance increases and capacity development rate decreases

Engineering Contradiction:

ImprovedurabilityVSAvoidcapacity development rate

Core Design Contradiction:

ReliabilityVSPower

Solution Approach 1:

The invention optimizes the thickness of the coating layer containing solid electrolyte to a specific range that balances two competing requirements: sufficient thickness to prevent interfacial cracks and maintain durability, yet thin enough to minimize interfacial resistance and maintain high capacity development rate. This parameter optimization enables the coating to provide protective function without sacrificing electrical performance

Inventive Principle:

Principle #35Parameter changes

3Reliability

If solid electrolyte coating is applied to silicon surface, then interfacial contact is maintained during volume change, but manufacturing precision is required to control coating thickness and composition

Engineering Contradiction:

Improveinterfacial contactVSAvoidcoating thickness control

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The invention uses a coating layer containing solid electrolyte as an intermediary substance between the silicon-based active material and the solid electrolyte layer. This intermediary coating can be applied using conventional coating methods and provides a buffer zone that maintains interfacial contact during silicon volume changes, reducing the need for extremely precise control of coating thickness while still achieving reliable interfacial contact

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 solution effectively prevents interfacial resistance increases and enhances coating uniformity, thereby improving the durability and output characteristics of the battery.

Implementation Method 1

silicon exhibits a volume change of nearly 400% during the charging and discharging process

Methodology Applied

Scientific EffectVolume expansion and contraction: Thermal Expansion

Implementation Method 2

solid electrolyte having high lithium-ion conductivity

Methodology Applied

Scientific EffectLithium-ion conductivity: Conduction (electrical)

Data Source

PatentUS20260074196A1Composite anode active material for all-solid-state-battery and manufacturing method thereof

Publication Date: 2026.03.12 HYUNDAI MOTOR CO LTD

AI summary

An embodiment composite negative electrode active material for an all-solid-state battery includes a negative electrode active material including a silicon-based active material and a coating layer including a solid electrolyte and coating a portion of a surface of the negative electrode active material, wherein a ratio (E/T) of a Young's modulus (E) of the solid electrolyte to a thickness (T) of the coating layer satisfies 0.02<E/T<0.06.