Stacked Lithium Battery Fabrication via Unidirectional Folding

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Solution Overview

Problem

Conventional methods for fabricating stacked lithium secondary batteries face issues such as electrode damage during folding, complex folding processes, loose fastening of the separator, reduced cycle life, and potential electrical shorts, especially with larger electrode surfaces requiring extensive facilities and space.

Innovation Solution

The method involves adhering anode and cathode plates in a neighboring manner on a separator, folding in a fixed one-direction to prevent electrical shorts, and using a separator configuration with a connected double-layered film to ensure tight fastening and efficient packaging, reducing the facility size and folding complexity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If electrode plates are adhered with predetermined intervals to allow insertion, then damage to electrodes during folding is prevented, but the length of separator required increases, requiring larger facility and working space

Engineering Contradiction:

Improveelectrode damage preventionVSAvoidfacility size

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The separator is divided into multiple sections, each adhering to one electrode plate. This segmentation allows the separator to be shorter in total length while still providing adequate spacing and protection for each electrode plate during the folding process.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The separator extends beyond the electrode plates in the width direction rather than requiring excessive length. This dimensional change allows the separator to provide sufficient coverage and protection while reducing the overall facility space required.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Shape

If separator is folded in zig-zag fashion to create stacked structure, then anode and cathode plates are alternatively stacked, but tight fastening of separator becomes difficult, causing gaps that deteriorate cycle life and charge/discharge characteristics

Engineering Contradiction:

Improvestacked structureVSAvoidcycle life

Core Design Contradiction:

ShapeVSReliability

Solution Approach 1:

Instead of folding the separator in a zig-zag pattern, the invention inverts the approach by folding the electrode plates in a regular alternating pattern while the separator extends linearly. This inversion eliminates the gaps caused by zig-zag folding and ensures tight fastening throughout the stacked structure.

Inventive Principle:

Principle #13The other way round (Inversion)

3Ease of manufacture

If cathode and anode plates are arranged in neighboring fashion on separator, then folding in fixed one-direction simplifies the process, but electrical short between neighboring plates may occur

Engineering Contradiction:

Improvefolding process simplicityVSAvoidelectrical short

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The separator serves as an intermediary barrier between the cathode and anode plates. By extending the separator beyond the electrode plates in the width direction and folding it to cover the electrode surfaces, it provides reliable electrical insulation that prevents shorts while allowing the simplified fixed-direction folding process.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Use of energy by moving object

If larger electrode surface area is used to increase capacity, then energy density improves, but probability of gap formation between electrodes and separator increases, making uniform electrical property fabrication difficult

Engineering Contradiction:

Improveenergy densityVSAvoiduniform electrical property

Core Design Contradiction:

Use of energy by moving objectVSManufacturing precision

Solution Approach 1:

The separator is designed with different functional zones: a central region adhering to each electrode plate and extended regions covering the electrode surfaces. This local quality differentiation ensures that larger electrodes maintain uniform electrical properties by providing adequate coverage and preventing gaps at critical areas.

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS8067112B2Stacked lithium secondary battery and its fabrication utilizing a folded configuration

Publication Date: 2011.11.29 ENERLAND

AI summary

There is provided a stacked lithium secondary battery in which a plurality of cathode plates and a plurality of anode plates are alternatively facing each other, and its fabrication method. The method comprises adhering a plurality of anode plates to a portion of one surface of a separator onto which the anode plates are neighboring one another, adhering a plurality of cathode plates to a portion of the other surface of the separator onto which the cathode plates are neighboring one another, covering either the cathode or anode plates with the separator by folding the portion to which no electrode plate is adhered, successively folding the separator in a fixed one-direction along folding lines formed between the electrode plates to obtain a stacked body, and housing the obtained stacked body within a pouch, followed by injection of an electrolyte solution and packaging. The method simplifies the folding process by a fixed one-directional folding rather than a zig-zag folding, and reduces the scale of a facility required for the adhesion process by minimizing the length occupied by the electrode plates. Further, the separator can be tightly fastened such that the charge/discharge characteristics and cycle life of the battery can be enhanced, compared to a zig-zag folding.