Bipolar Battery Current Collector Isolation Layer Design
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Solution Overview
Problem
Resin current collectors used in bipolar lithium ion secondary batteries suffer from low lithium ion isolation performance, leading to absorption of lithium ions, which reduces battery capacity due to the presence of imide group-containing resins.
Innovation Solution
Incorporating a second electrically conductive layer with an isolation resin layer and a metal layer in the current collector, where the isolation resin layer is made from a substrate without imide groups and the metal layer is positioned to prevent lithium ion permeation, thereby enhancing lithium ion isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a resin current collector containing imide group-containing resin is used, then heat resistance and solvent resistance are improved, but lithium ion isolation performance deteriorates
Solution Approach 1:
The current collector is divided into multiple functional layers: a base layer providing heat and solvent resistance, and a separate isolation layer specifically designed to prevent lithium ion permeation. This segmentation allows each layer to optimize its specific function without compromise.
Solution Approach 2:
The current collector uses a composite structure combining imide group-containing resin (for heat/solvent resistance) with isolation resin and metal layers (for lithium ion isolation). This composite approach integrates multiple material properties to simultaneously achieve thermal stability and ion isolation.
2Strength
If imide group-containing resin is used in the current collector, then strength and solvent resistance are improved, but lithium ion absorption increases
Solution Approach 1:
An isolation layer made of isolation resin and metal is introduced as an intermediary between the imide group-containing resin and the lithium ions. This intermediary layer maintains the structural strength provided by the imide resin while preventing direct interaction between lithium ions and the resin that would cause absorption.
3Power
If connectors are used to connect batteries in series, then high output power is achieved, but electric resistance increases
Solution Approach 1:
The bipolar electrode structure merges the positive electrode, negative electrode, and current collector into a single integrated component. This eliminates the need for external connectors between battery cells, removing the source of electric resistance while maintaining high output power capability.
4Power
If connectors are used to connect batteries, then series connection is achieved, but space efficiency deteriorates
Solution Approach 1:
By integrating the current collector with both positive and negative electrodes in a bipolar configuration, the design eliminates separate connectors and interconnection components. This merging of functions significantly reduces the space required for connection hardware while maintaining series connection capability.
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
This configuration effectively prevents lithium ion absorption into the current collector, maintaining battery capacity and improving resistance to negative electrode potential, ensuring higher energy density and reduced risk of short circuits.
Implementation Method 1
the lithium ions enter inside the resin current collector included in the bipolar electrode and as a result, the lithium ions remain absorbed inside the current collector
Implementation Method 2
the resin having such characteristics, imide group-containing resin such as polyimide is preferable; however, it was also revealed that the lithium ions are absorbed inside the resin current collector significantly when using the imide group-containing resin
Implementation Method 3
the resin included in the resin current collector is preferably hardly deformed by heat treatment or pressure treatment when manufacturing a battery and hardly dissolved in a solvent in an electrolysis solution
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
A current collector (3) for a bipolar lithium ion secondary battery includes: a first electrically conductive layer (3A) in which electrically conductive filler is added to a substrate containing imide group-containing resin; and a second electrically conductive layer (3B) that functions to isolate lithium ions. The second electrically conductive layer (3B) includes an isolation resin layer (3a) and a metal layer (3b), the isolation resin layer (3a) having a constitution in which electrically conductive filler is added to a substrate containing resin not containing imide group. The first electrically conductive layer (3A) is located in a manner such that a positive electrode active material layer is closer thereto than the second electrically conductive layer (3B).