Bipolar Battery Unit Cell Sealing and Current Collector Design
Solution Overview
Problem
Bipolar electrodes in secondary batteries face challenges in increasing capacity and preventing electrolyte leakage, while maintaining safety and uniform current transmission, due to the use of stainless steel current collectors and gaskets that are difficult to manufacture thinly.
Innovation Solution
A bipolar unit cell design with a laminate structure that includes a positive and negative electrode current collector, separator, and a sealing portion to contain a liquid or gel electrolyte, with a conductive layer on the current collectors to ensure uniform current transmission and prevent warpage, using conductive tape or sealant made of copper or carbon.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a gasket is used to seal the bipolar battery, then electrolyte leakage is prevented, but the thickness of the gasket cannot be made less than 1 mm, increasing empty space and reducing output-to-volume ratio
Solution Approach 1:
The sealing portion integrates both sealing and spacing functions into a single component. The sealing portion is formed by laminating insulation films with adhesive layers, creating a thin (50-200 μm) structure that simultaneously seals the electrolyte and maintains electrode spacing, eliminating the need for separate thick gaskets
Solution Approach 2:
The sealing portion uses flexible insulation films (PET, PI, or polyolefin) with thickness of 50-200 μm that can conform to the electrode surfaces while providing effective sealing. These thin films reduce the sealing layer thickness to less than 1 mm while maintaining leakage prevention, directly solving the contradiction between sealing reliability and volume efficiency
2Duration of action of stationary object
If stainless steel current collector is used in bipolar electrodes, then electrode durability is improved, but manufacturing flexibility is limited and capacity increase is difficult
Solution Approach 1:
The current collector material is changed from stainless steel to aluminum foil with thickness of 3-10 μm. This parameter change enables better flexibility, easier manufacturing, and improved capacity regulation while the aluminum material provides sufficient durability for the application
Solution Approach 2:
The patent uses thinner aluminum foil current collectors that are more easily manufactured and disposed of, replacing the durable but inflexible stainless steel. The aluminum foil can be easily formed and manufactured, providing manufacturing flexibility and capacity regulation capability
3Reliability
If bipolar electrodes are stacked without connection portions, then connection resistance is minimized, but capacity increase becomes difficult due to structural limitations
Solution Approach 1:
The bipolar electrode structure performs multiple functions: it provides electrical connection between cells through direct contact, serves as both positive and negative electrodes in different regions, and enables capacity scaling by simply stacking more units. The aluminum current collector with conductive layers provides universal electrical connectivity without additional connection portions
Data Source
Figure 1~2
Figure 3~4
AI summary
According to an embodiments of the present disclosure, provided is a bipolar unit cell comprising: a laminate which includes a positive electrode current collector, a positive electrode material layer formed on one surface of the positive electrode current collector, a negative electrode current collector, a negative electrode material layer formed on one surface of the negative electrode current collector, and a separator, and in which the positive electrode material layer and the negative electrode material layer are stacked so as to face each other while interposing a separator between them, and a sealing portion that is attached form the other surface of the positive current collector to the other surface of the negative current collector to integrally form the laminate and seal the inside, wherein a conductive layer is formed on the outside of at least one of the positive electrode current collector and the negative electrode current collector, and a bipolar battery having a structure in which two or more of the bipolar unit cells are stacked.