Silicon Anode Recess Structure to Prevent Current Collector Breakage

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Solution Overview

Problem

The negative electrode current collector in secondary batteries with silicon-containing compounds is prone to breakage and has insufficient accuracy and regularity of protrusions and recesses, leading to reduced electronic conductivity and deteriorated cycle characteristics, with potential Li metal precipitation at exposed portions.

Innovation Solution

A secondary battery design featuring a negative electrode active material layer with recessed portions and protruding portions on the surface facing the current collector, formed by laser ablation, ensuring a flat surface on the current collector boundary, enhancing energy density and cycle characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If protrusions and recesses are formed in the negative electrode current collector to improve energy density, then the energy density is improved, but the current collector is easily broken and electronic conductivity is lowered

Engineering Contradiction:

Improveenergy densityVSAvoidcurrent collector breakage resistance

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The invention extracts the protrusion and recess features from the current collector and relocates them solely to the negative electrode active material layer. This separation preserves the current collector's structural integrity while maintaining the energy density benefits of the protrusion-recess structure in the silicon-containing active material layer.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention applies local quality by creating protrusions and recesses specifically in the negative electrode active material layer where they are needed for volume expansion accommodation, while keeping the current collector surface flat to maintain its mechanical strength and electrical conductivity functions.

Inventive Principle:

Principle #3Local quality

2Ease of manufacture

If protrusions and recesses are formed by rolling with a cutter to improve structure design, then the structure is formed, but accuracy and regularity are insufficient and basis weight control is difficult

Engineering Contradiction:

Improvestructure formation capabilityVSAvoidprotrusion and recess accuracy

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The invention replaces the mechanical rolling cutter system with a laser processing system. Laser processing provides superior accuracy, regularity, and controllability in forming protrusions and recesses in the negative electrode active material layer, while avoiding the mechanical contact that causes basis weight control issues.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Strength

If the current collector is exposed in recessed portions, then structural support is provided, but Li metal precipitation occurs and cycle characteristic deteriorates

Engineering Contradiction:

Improvestructural supportVSAvoidcycle characteristic

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The invention extracts the recess formation from the current collector and places it only in the negative electrode active material layer. This prevents current collector exposure and subsequent Li metal precipitation, while still providing the necessary structural support through the protrusion and recess structure in the active material layer itself.

Inventive Principle:

Principle #2Taking out (Extraction)

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 design improves energy density and cycle retention by absorbing expansion and maintaining conductivity, reducing the risk of Li metal precipitation and collector breakage.

Implementation Method 1

a step of forming a recessed portion in the negative electrode active material layer, and the recessed portion is formed by laser ablation

Methodology Applied

Scientific EffectLaser ablation: Laser Ablation

Data Source

PatentUS20250372608A1Secondary battery and method of manufacturing secondary battery

Publication Date: 2025.12.04 MURATA MFG CO LTD

AI summary

A secondary battery using a negative electrode capable of improving a cycle characteristic, improving energy density, and improving safety of the secondary battery without provision of a recess or a protrusion in a negative electrode current collector. In the secondary battery, a negative electrode active material layer has a compound containing silicon. The negative electrode active material layer has a plurality of recessed portions in which a surface on an opposite side to a surface adjacent to the negative electrode current collector is recessed toward the negative electrode current collector side, and a protruding portion formed on both sides of the recessed portion.