SiOx Negative Electrode Composition for Stable Fast-Charging Cycles

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Solution Overview

Problem

Existing lithium ion secondary batteries using graphite as a negative electrode active material face challenges in further increasing energy density and suppressing the expansion and contraction of the negative electrode during charge and discharge, leading to reduced lifespan.

Innovation Solution

A negative electrode active material layer comprising a silicon-based material (SiOx) and carbon-based materials with specific particle size distributions, optimized by controlling the ratios of D10 and D90 values, is used to suppress expansion and contraction, enhancing electrical contact and conductivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If a silicon-based negative electrode active material is used to increase energy density, then capacity is improved, but expansion and contraction during charge and discharge increases leading to loss of contact between particles

Engineering Contradiction:

Improveenergy densityVSAvoidcontact stability between particles

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent uses a composite material system consisting of silicon-based active material particles (providing high capacity) combined with carbonaceous particles (providing structural stability and conductivity). This composite structure allows the silicon particles to expand and contract during lithium insertion/extraction while the carbon matrix maintains particle contact and provides mechanical support, thus resolving the contradiction between high energy density and contact stability.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent optimizes specific parameters including the particle size distribution (D10, D50, D90 values and their ratios), the ratio of silicon-based to carbonaceous particles (0.05 to 2.0 by mass), and the void fraction (0.3 to 0.6). By controlling these parameters, the electrode structure accommodates silicon expansion while maintaining particle contact and ensuring stable electrical conductivity throughout charge-discharge cycles.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If graphite is used as negative electrode active material, then safety and cycle stability are improved, but energy density cannot be further increased

Engineering Contradiction:

Improvecycle stabilityVSAvoidenergy density

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent creates a composite negative electrode containing both silicon-based active material particles (for high capacity and energy density) and carbonaceous particles (for structural stability and conductivity). This composite approach allows the electrode to achieve higher energy density than pure graphite while maintaining cycle stability through the carbon matrix that prevents particle disintegration.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent applies different materials with different properties to different functional requirements: silicon-based particles provide high lithium insertion/extraction capacity in specific regions, while carbonaceous particles provide structural framework and electrical conductivity throughout the electrode. This local differentiation of material properties enables simultaneous achievement of high energy density and stable cycling.

Inventive Principle:

Principle #3Local quality

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 results in a negative electrode that supports rapid charge and discharge capabilities while improving the lifespan and energy density of nonaqueous electrolyte secondary batteries.

Implementation Method 1

suppress the loss of contact between active material particles due to repeated expansion and contraction of the negative electrode during charge and discharge

Methodology Applied

Scientific EffectExpansion and contraction:

Implementation Method 2

a carbon-based active material (B), composed of secondary particles formed by aggregation of primary particles; and a carbon-based active material (C), composed of primary particles that do not form secondary particles

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Data Source

PatentEP4693461A1Negative electrode for nonaqueous electrolyte secondary battery, and nonaqueous electrolyte secondary battery using same

Publication Date: 2026.02.11 AESC JAPAN LTD

AI summary

An objective of the present invention is to suppress the expansion and contraction of a negative electrode active material layer when charging and discharging a nonaqueous electrolyte secondary battery, including lithium ion secondary batteries, when an Si-based negative electrode active material is used, to improve the lifespan (cycle characteristics) of the nonaqueous electrolyte secondary battery, and to improve rapid charging properties. The negative electrode active material contains: a silicon-based active material (A) containing SiOx (in the formula, x is a number satisfying 0.5≤x≤1.6); a carbon-based active material (B) composed of secondary particles formed by aggregating the primary particles; and a carbon-based active material (C) composed of primary particles that do not form the secondary particles. D10A is 3 µm or more, and if the maximum value of D10 among values of D10A, D10B, and D10C is defined as D10max, and the minimum value is defined as D10min, the value of D10max/D10min is 2.5 or less. If the maximum value of D90 among values of D90A, D90B, and D90c is defined as D90max, and the minimum value is defined as D90min, the value of D90 max/D90 min is 2.0 or less.