Wound Secondary Battery Electrode Layout to Prevent Separator Stress

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Solution Overview

Problem

Secondary batteries face stress concentration on local portions of the separator due to external impacts, leading to potential breakage and short circuits at exposed current collector areas.

Innovation Solution

The secondary battery design includes a configuration where insulating members cover exposed portions of the positive electrode, with their ends and the ends of the positive electrode material layers shifted in the circumferential direction, reducing the number of stress concentration points and dispersing stress on the separator.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If insulating members are provided to cover exposed portions of the current collector, then internal short-circuit prevention is improved, but stress concentration on the separator occurs due to aligned step portions

Engineering Contradiction:

Improveinternal short-circuit preventionVSAvoidstress concentration on separator

Core Design Contradiction:

ReliabilityVSStress or pressure

Solution Approach 1:

The patent applies asymmetry by intentionally misaligning the ends of insulating members with the ends of positive electrode material layers in the circumferential direction. This asymmetric arrangement prevents the formation of aligned step portions that would concentrate stress on the separator, while still maintaining the insulating function to prevent internal short-circuits at exposed current collector portions.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent addresses the stress concentration problem by shifting the alignment issue from the thickness direction (where step portions would align) to the circumferential direction (where ends are misaligned). This dimensional shift allows the insulating members to maintain their protective function while eliminating the harmful stress concentration effect.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Ease of manufacture

If tape ends of insulating tape are arranged aligned in thickness direction, then manufacturing simplicity is improved, but two step portions align causing stress concentration

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidstress concentration at step portions

Core Design Contradiction:

Ease of manufactureVSStress or pressure

Solution Approach 1:

The patent introduces asymmetry in the circumferential direction by misaligning the ends of insulating members with the ends of electrode material layers. This asymmetric configuration prevents the formation of aligned step portions in the thickness direction, thereby eliminating stress concentration while remaining manufacturable through standard winding processes.

Inventive Principle:

Principle #4Asymmetry

Data Source

PatentUS20250392025A1Secondary battery

Publication Date: 2025.12.25 MURATA MFG CO LTD

AI summary

A secondary battery is provided and including a wound electrode assembly in which a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode are wound; and an electrolyte, the wound electrode assembly and the electrolyte being enclosed in an exterior body, at least the positive electrode including a wound current collector, a first positive electrode material layer and a second positive electrode material layer provided on both surfaces of the current collector, and a pair of exposed portions including a first exposed portion in which one surface of a local portion of the current collector is exposed and a second exposed portion in which the other surface facing the one surface in a thickness direction of the positive electrode is exposed.