Composite Cathode Coating for All-Solid-State Battery Interfacial Resistance

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Solution Overview

Problem

All-solid-state secondary batteries with sulfide-based solid electrolytes face issues such as increased interfacial resistance due to reactions at the cathode active material and electrolyte interface, leading to decreased lithium ion conductivity and battery performance, particularly under high load conditions.

Innovation Solution

A composite cathode active material is developed, comprising core particles coated with a first lithium-containing compound like lithium zirconium oxide and a second lithium-containing compound like lithium germanium oxide, which suppresses reactions and enhances lithium ion conductivity, thereby improving battery characteristics and productivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a sulfide-based solid electrolyte is used in all-solid-state secondary batteries, then high lithium ion conductivity is achieved, but interfacial reactions between the electrolyte and cathode active material increase, leading to increased interfacial resistance and decreased battery performance

Engineering Contradiction:

Improvelithium ion conductivityVSAvoidinterfacial resistance

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

An amorphous carbon film is introduced as an intermediary layer between the sulfide-based solid electrolyte and the cathode active material. This carbon coating prevents direct contact and harmful reactions at the interface while maintaining lithium ion conductivity, thereby reducing interfacial resistance and improving battery performance under high load conditions.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention uses a composite structure combining the sulfide-based solid electrolyte with a carbon-coated cathode active material. This composite approach leverages the high lithium ion conductivity of the sulfide electrolyte while the carbon coating provides chemical stability and reduces interfacial reactions, achieving both high conductivity and low interfacial resistance.

Inventive Principle:

Principle #40Composite materials

2Reliability

If complicated film formation methods such as blasting, aerosol deposition, cold spraying, sputtering, CVD, or spraying are used to coat amorphous carbon film, then the cathode active material characteristics are improved, but productivity decreases due to complex processes

Engineering Contradiction:

Improvebattery characteristicsVSAvoidmanufacturing efficiency

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The invention employs a simple and cost-effective carbon coating method that can be integrated into existing manufacturing processes, avoiding the need for complex and expensive equipment such as sputtering or CVD systems. This approach maintains high battery characteristics while significantly improving productivity and reducing manufacturing complexity.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The invention optimizes the carbon coating parameters such as coating thickness, carbon source, and deposition conditions to achieve effective protection against interfacial reactions without requiring complicated processes. By carefully controlling these parameters, high battery performance is achieved through a simplified manufacturing approach that enhances productivity.

Inventive Principle:

Principle #35Parameter changes

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 cathode active material effectively reduces interfacial resistance and enhances the lithium ion transfer path between the cathode and electrolyte, leading to improved discharge capacity, rate characteristics, and cycle lifespan of the all-solid-state secondary battery.

Implementation Method 1

a first coating layer; and a second coating layer, wherein the core particle comprises a cathode active material, the first and second coating layers cover a surface of the core particle

Methodology Applied

Scientific EffectSurface coating: Coatings

Implementation Method 2

enhances the lithium ion transfer path between the cathode and electrolyte, leading to improved discharge capacity, rate characteristics, and cycle lifespan

Methodology Applied

Scientific EffectIon conduction: Conduction (electrical)

Data Source

PatentUS11217785B2Composite cathode active material and secondary battery including the same

Publication Date: 2022.01.04 SAMSUNG ELECTRONICS CO LTD

AI summary

A composite cathode active material including: a core particle; a first coating layer; and a second coating layer; wherein the core particle includes a cathode active material, the first and second coating layers cover a surface of the core particle, the first coating layer includes a first lithium-containing compound, wherein the first lithium-containing compound includes zirconium, niobium, titanium, aluminum, or a combination thereof, the second coating layer includes a second lithium-containing compound, wherein the second lithium-containing compound includes germanium, niobium, gallium, or a combination thereof, and the first lithium-containing compound is different from the second lithium-containing compound.