Calcium-Conductive Coating for Silicon-Silicate Anode Capacity Retention

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Solution Overview

Problem

Lithium silicate-based negative electrodes in non-aqueous electrolyte secondary batteries are prone to dissolution in decomposition products, leading to increased surface area and severe capacity deterioration due to repeated charge-discharge cycles.

Innovation Solution

Incorporating composite particles with a silicate phase and silicon phases dispersed within, and a calcium-containing conductive layer on the surface to stabilize the electrolyte decomposition products and reduce contact between the silicate phase and decomposition products, thereby suppressing capacity reduction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If lithium silicate is used as negative electrode active material, then high theoretical capacity density is achieved, but severe capacity deterioration occurs due to dissolution in electrolyte decomposition products

Engineering Contradiction:

Improvecapacity densityVSAvoidcapacity retention

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

A calcium-containing coating layer is introduced as an intermediary between the lithium silicate particles and the electrolyte decomposition products. This coating layer selectively reacts with and stabilizes the decomposition products (such as HF), preventing them from dissolving the lithium silicate. The calcium component acts as a mediator that sacrifices itself to protect the active material, thereby resolving the contradiction between maintaining high capacity density and preventing capacity deterioration.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The chemical composition of the particle surface is changed by coating lithium silicate particles with calcium-containing materials. This parameter change transforms the surface chemistry from being vulnerable to acid dissolution to being protected by calcium's high reactivity with decomposition products. The coating layer changes the interaction parameters between the active material and electrolyte byproducts, preventing harmful dissolution while maintaining electrochemical performance.

Inventive Principle:

Principle #35Parameter changes

2Area of stationary object

If lithium silicate dissolves in decomposition products, then surface area of lithium silicate phase increases, but side reaction progress is facilitated leading to severe capacity deterioration

Engineering Contradiction:

Improvesurface areaVSAvoidside reaction

Core Design Contradiction:

Area of stationary objectVSObject-generated harmful factors

Solution Approach 1:

The high reactivity of lithium silicate that causes harmful dissolution is converted into a benefit through the calcium-containing coating layer. The coating layer is designed to be even more reactive toward decomposition products than lithium silicate, so it preferentially reacts with and stabilizes these products. This converts the potential harm of high reactivity into a protective mechanism where the coating layer acts as a sacrificial barrier, preventing the dissolution of lithium silicate while utilizing the same chemical reactivity principle.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Reliability

If calcium-containing conductive layer is added to protect silicate phase, then capacity deterioration is suppressed, but device complexity increases

Engineering Contradiction:

Improvecharge-discharge cycle characteristicsVSAvoidcomposite structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

A thin film coating layer containing calcium is applied to the surface of lithium silicate particles. This thin film serves multiple functions: it protects the underlying active material from dissolution, provides conductive pathways, and stabilizes electrolyte decomposition products. By using a thin film rather than a thick coating or complex multi-layer structure, the solution maintains particle integrity and electrochemical performance while minimizing the added complexity. The flexible nature of the coating allows it to accommodate volume changes during charge-discharge cycles.

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 calcium-containing conductive layer effectively stabilizes electrolyte decomposition products, reducing the surface area of the silicate phase and minimizing capacity deterioration, thus enhancing the charge-discharge cycle characteristics of the battery.

Implementation Method 1

the calcium-containing conductive layer effectively stabilizes electrolyte decomposition products, reducing the surface area of the silicate phase

Methodology Applied

Scientific EffectChemical reaction: Reaction (physics)

Data Source

PatentUS20230307612A1Negative electrode material for non-aqueous electrolyte secondary battery, and non-aqueous electrolyte secondary battery

Publication Date: 2023.09.28 PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD

AI summary

A negative electrode material for a non-aqueous electrolyte secondary battery includes composite particles, and a conductive layer disposed on a surface of each of the composite particles. The composite particles each have a silicate phase, and silicon phases dispersed in the silicate phase. The conductive layer contains a calcium component.