Cylindrical Separator Minimizes Internal Resistance

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Solution Overview

Problem

Existing electrochemical cell separators that are thicker than necessary to prevent short circuits increase internal resistance, leading to decreased cell performance, particularly in cross-strip configurations where overlapping portions are more prevalent, complicating manufacturing and reducing discharge performance.

Innovation Solution

A cylindrical separator is formed from a single continuous sheet, with opposing longitudinal edges meeting without overlap to minimize thick overlapping portions, reducing internal resistance and improving discharge performance by maintaining continuity and minimizing seams that could cause short circuits.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a thicker separator is used to prevent short circuits, then reliability is improved, but internal resistance increases and discharge performance deteriorates

Engineering Contradiction:

Improveshort circuit preventionVSAvoidinternal resistance

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The separator is divided into two distinct plies: a first ply formed by rolling one end of the separator sheet and a second ply formed by rolling the other end. This segmentation allows each ply to be optimized independently, with the first ply providing short circuit prevention and the second ply providing reinforcement without excessive thickness, thus resolving the contradiction between reliability and energy loss.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the separator have different thicknesses and structures. The first ply has a thickness optimized for preventing short circuits, while the second ply provides additional reinforcement. This local differentiation allows the separator to provide maximum protection where needed while minimizing overall thickness and internal resistance, resolving the contradiction between reliability and energy loss.

Inventive Principle:

Principle #3Local quality

2Ease of manufacture

If overlapping portions are used in cross-strip separator configurations, then manufacturing is simplified, but thick overlapping portions increase internal resistance and reduce discharge performance

Engineering Contradiction:

Improveseparator constructionVSAvoiddischarge performance

Core Design Contradiction:

Ease of manufactureVSLoss of energy

Solution Approach 1:

The separator is segmented into two non-overlapping plies, each formed from opposite ends of the separator sheet. This eliminates the thick overlapping portions found in traditional cross-strip configurations while maintaining the structural integrity and ease of manufacture through the systematic two-ply construction method.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of forming the separator by overlapping strips in the traditional cross-strip configuration, this invention inverts the approach by forming two separate plies from opposite ends of a continuous separator sheet that meet without overlapping. This inversion eliminates the harmful thick overlapping portions while maintaining manufacturing simplicity.

Inventive Principle:

Principle #13The other way round (Inversion)

3Adaptability or versatility

If multiple seams are present in the separator, then manufacturing flexibility is improved, but the risk of short circuits through seams increases

Engineering Contradiction:

Improvemanufacturing flexibilityVSAvoidshort circuit risk

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The invention extracts and eliminates the problematic multiple seams from the separator structure. By forming the separator from a single continuous sheet rolled into two plies without overlapping, the design removes the seams that could potentially cause short circuits, while maintaining manufacturing flexibility through the continuous sheet formation process.

Inventive Principle:

Principle #2Taking out (Extraction)

4Reliability

If the separator occupies more volume, then short circuit prevention is improved, but the volume available for active material decreases

Engineering Contradiction:

Improveshort circuit preventionVSAvoidactive material volume

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The separator utilizes a thin-film construction with two plies of controlled thickness. The first ply provides essential short circuit prevention, while the second ply adds reinforcement. This thin-film approach maximizes the protective function of the separator while minimizing the volume consumed, leaving maximum space for active material in the electrochemical cell.

Inventive Principle:

Principle #30Flexible shells and thin films

Data Source

PatentUS11108116B2Electrochemical cell separator

Publication Date: 2021.08.31 ENERGIZER BRANDS LLC

AI summary

The discharge performance of a primary, bobbin-style electrochemical cell is improved by incorporating a separator formed from a continuous separator sheet defining a two-layer cylindrical sidewall and a closed bottom end between the included electrochemical cell cathode and anode. A first layer of the cylindrical separator is formed by rolling a first end of a continuous separator sheet into a cylinder having a central axis parallel with a longitudinal axis of the continuous separator sheet, and then rolling a second end of the continuous separator sheet around the exterior of the first cylindrical layer to form a second cylindrical layer. The closed bottom end is formed by a portion of the continuous separator sheet located between the rolled portion of the first end and the rolled portion of the second end.