Gradient-Coated Silicon Active Material for Capacity Retention

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Solution Overview

Problem

Silicon compounds used as negative electrode materials in lithium ion secondary batteries are susceptible to erosion during battery operation, leading to a decrease in capacity retention rate.

Innovation Solution

A lithium silicate composite particle with a first coating containing an oxide of a first element other than a non-metal element and carbon atoms is developed, where the element ratio of the first element to carbon atoms varies across the coating thickness to enhance chemical stability and electrical conductivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If a silicon compound is used as the active material particles to increase capacity, then the capacity of the electrochemical device is improved, but the capacity retention rate decreases due to erosion by side reactions

Engineering Contradiction:

ImprovecapacityVSAvoidcapacity retention rate

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

A first coating layer containing an oxide of a first element (such as aluminum oxide, titanium oxide, or silicon oxide) is introduced as an intermediary between the silicon-based active material particles and the electrolyte. This coating layer acts as a protective barrier that suppresses erosion by side reactions while allowing lithium ion transport, thereby maintaining both high capacity and good capacity retention rate

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The active material particles are designed as composite structures consisting of a silicon-based core (providing high capacity) surrounded by a protective coating layer (providing stability). The coating layer contains a mixture of oxide particles and carbon, creating a composite material that combines the benefits of high capacity with improved structural stability and resistance to side reactions

Inventive Principle:

Principle #40Composite materials

2Reliability

If a coating layer is formed on the active material particles to suppress erosion, then the capacity retention rate is improved, but the electrical conductivity may decrease

Engineering Contradiction:

Improvecapacity retention rateVSAvoidelectrical conductivity

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The coating layer is designed with non-uniform composition and structure: the inner portion contains a higher concentration of oxide for protection, while the outer portion contains more carbon for electrical conductivity. This local variation in composition allows the coating to simultaneously provide erosion resistance and maintain electrical conductivity without compromising either property

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The coating layer's composition parameters are optimized by controlling the ratio of oxide to carbon and adjusting the thickness of the coating. By changing these parameters, the coating can be tuned to provide the right balance between protection (requiring thicker, oxide-rich layers) and conductivity (requiring thinner, carbon-rich layers), allowing simultaneous improvement of both capacity retention and electrical conductivity

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 solution increases the capacity retention rate of electrochemical devices by suppressing erosion and improving electrical conductivity of the active material particles.

Implementation Method 1

silicon compounds are more susceptible to erosion by side reactions during battery operation than when using a carbon material as the negative electrode material

Methodology Applied

Scientific EffectErosion resistance:

Implementation Method 2

the first coating includes an oxide of a first element other than a non-metal element, and includes a carbon atom

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Data Source

PatentUS12500228B2Active material particles, electrochemical element, method for producing said active material particles, method for producing said electrochemical element, and electrochemical device

Publication Date: 2025.12.16 PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD

AI summary

An active material particle include a lithium silicate composite particle including a lithium silicate phase, and silicon particles dispersed in the lithium silicate phase, and a first coating that covers at least a portion of a surface of the lithium silicate composite particle; wherein the first coating includes an oxide of a first element other than a non-metal element, and a carbon atom, the first coating has a thickness T1A, an element ratio Rb of the first element relative to the carbon atom at a position of 0.25T1A of the first coating from the surface of the lithium silicate composite particle, and an element ratio Rt of the first element relative to the carbon atom at a position of 0.75T1A of the first coating from the surface of the lithium silicate composite particle satisfy Rb>Rt.