Rolled Electrode Assembly Roll End Fixation

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Solution Overview

Problem

Nonaqueous electrolyte secondary batteries with rolled electrode assemblies face issues of electrode plate breakage due to stress from expansion and contraction during high-voltage charging and discharging, exacerbated by the concentration of stress at the roll ends and pressure from the outer can.

Innovation Solution

The battery design features a rolled electrode assembly where the separator is placed on the outermost periphery and fixed with adhesive tape, with an exposed portion of the negative electrode substrate without active material on the outermost periphery, and a negative electrode tab connected, ensuring that the adhesive tape does not overlap with the roll ends of either electrode plate, dispersing stress and preventing plate breakage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the separator extends over the roll end and is fixed with adhesive tape, then the roll end is secured and does not loosen, but stress concentrates at the roll end causing electrode plate breakage during high-voltage charging and discharging

Engineering Contradiction:

Improveroll end fixationVSAvoidelectrode plate integrity

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The invention extracts the harmful adhesive tape from the roll end area and replaces it with a protective insulating cover that wraps around the roll end. This removes the source of stress concentration while maintaining the fixation function through the cover's wrapping structure rather than adhesive bonding at the critical roll end location.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The insulating cover acts as an intermediary element between the separator and the external environment. Instead of using adhesive tape that directly bonds to the separator and creates stress points, the cover provides a protective layer that secures the roll end through its wrapping structure without concentrating stress on the electrode plates.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Quantity of substance

If the rolled electrode assembly expands during high-voltage charging, then the battery capacity increases, but the outer can pressures the adhesive tape and roll end area causing deformation and potential breakage

Engineering Contradiction:

Improvebattery capacityVSAvoidpressure on roll end

Core Design Contradiction:

Quantity of substanceVSStress or pressure

Solution Approach 1:

The insulating cover is installed beforehand on the roll end to provide cushioning protection. When the electrode assembly expands during high-voltage charging, the cover absorbs and distributes the external pressure from the outer can, preventing direct transmission of stress to the adhesive tape and roll end structures that could cause deformation or breakage.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The insulating cover functions as a flexible protective shell that wraps around the roll end. This flexible structure can accommodate the expansion of the electrode assembly during charging while maintaining protection against external pressure from the outer can, distributing forces evenly rather than creating concentrated stress points.

Inventive Principle:

Principle #30Flexible shells and thin films

3Use of energy by moving object

If high-voltage positive electrode plates are used to increase operating voltage, then energy density improves, but electrolyte decomposition accelerates causing rolled electrode assembly expansion and increased stress on roll end

Engineering Contradiction:

Improveoperating voltageVSAvoidelectrolyte decomposition

Core Design Contradiction:

Use of energy by moving objectVSObject-generated harmful factors

Solution Approach 1:

The invention converts the harmful effect of electrolyte decomposition and associated expansion into a manageable condition. By providing the insulating cover protection, the system can tolerate the expansion caused by high-voltage operation and electrolyte decomposition without suffering the previously fatal consequence of roll end breakage, thus enabling high-voltage operation to proceed safely.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The insulating cover is installed in advance to cushion against the anticipated expansion from electrolyte decomposition during high-voltage charging. This beforehand protection allows the battery to operate at high voltages where electrolyte decomposition is accelerated, as the cover prevents the expansion from translating into destructive stress on the roll end structures.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Data Source

PatentUS8597829B2Nonaqueous electrolyte secondary battery with rolled electrode assembly

Publication Date: 2013.12.03 PANASONIC ENERGY CO LTD

AI summary

The nonaqueous electrolyte secondary battery includes a rolled electrode assembly 14E formed by rolling a positive electrode plate 11 and a negative electrode plate 12 with a separator 13 interposed therebetween, the separator 13 is fixed on the outermost periphery of the rolled electrode assembly 14E with an adhesive tape for fixing a roll end 30e, an exposed portion of a negative electrode substrate 12c without an active material mixture layer 12b is placed on an outermost periphery side of the negative electrode plate 12, a negative electrode tab 12a is connected to the negative electrode substrate 12c on an outermost periphery side, and the adhesive tape 30e is not overlapped with a roll end 11d of the positive electrode plate 11 and a roll end 12d of the negative electrode substrate 12c. Thus the battery is seldom broken even when charging and discharging are repeatedly provided at high voltage.