Bipolar Electrode Adhesive Layer for Conductivity and Bond Strength
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Solution Overview
Problem
Conventional bipolar batteries face a challenge in achieving both favorable bonding strength and conductivity due to the use of carbon black as a conductive auxiliary agent, which necessitates a high amount to reduce resistance but compromises bonding strength.
Innovation Solution
A power storage device with bipolar electrodes using a conductive adhesive layer containing spherical conductive auxiliary agents with controlled particle size distribution, ensuring a specific addition ratio and particle size relationship to maintain bonding strength while reducing internal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large amount of carbon black is included in the conductive adhesive to reduce resistance, then conductivity is improved, but bonding strength decreases
Solution Approach 1:
The patent changes the particle size parameter of the conductive auxiliary agent from conventional small particles to large particles (0.5-5.0 μm). This parameter change allows achieving sufficient conductivity with a smaller addition ratio (0.1-1.0% by volume), thereby maintaining bonding strength while improving conductivity. The large particles create efficient conduction paths with fewer particles required.
Solution Approach 2:
The patent uses a composite conductive auxiliary agent consisting of a core particle (organic or inorganic) coated with a conductive material layer. This composite structure combines the advantages of the core material (providing structural integrity and dispersion) with the conductive coating (providing electrical conductivity), achieving both good conductivity and bonding strength.
2Reliability
If the addition ratio of conductive auxiliary agent is increased to improve conductivity, then resistance is reduced, but bonding strength and gas generation issues worsen
Solution Approach 1:
By changing the particle size parameter to larger dimensions (0.5-5.0 μm), the patent reduces the total number of particles needed for conduction, lowering the addition ratio to 0.1-1.0% by volume. This reduced amount minimizes gas generation during manufacturing while achieving sufficient conductivity through efficient particle-to-particle contact paths.
3Ease of manufacture
If conventional conductive adhesive is used, then manufacturing is simple, but air entrapment and resistance increase at larger electrode sizes
Solution Approach 1:
The patent changes the particle size parameter to larger dimensions (0.5-5.0 μm), which reduces the number of particles required for conduction. This results in fewer particles to pack and less air entrapment during the lamination process, maintaining good conductivity even in large-sized electrodes while keeping the manufacturing process simple.
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
The solution provides bipolar electrodes with enhanced bonding strength and conductivity, minimizing air entrapment and resistance increases, even at larger sizes, and reduces gas generation during manufacturing.
Implementation Method 1
the conductive auxiliary agent is a spherical particle having a spherical core and a conductive film covering the core
Implementation Method 2
a conductive adhesive layer positioned between the first current collector foil and the second current collector foil and bonded to the first current collector foil and the second current collector foil
Data Source
Figure 1
Figure 2
Figure 3(a)~3(b)
AI summary
A power storage device includes a plurality of bipolar electrodes, each of the plurality of bipolar electrodes including a first current collector foil and a second current collector foil overlapping each other, a conductive adhesive layer positioned between the first current collector foil and the second current collector foil and bonded to the first current collector foil and the second current collector foil, a first active material layer positioned on a surface of the first current collector foil, and a second active material layer positioned on a surface of the second current collector foil. The conductive adhesive layer includes an adhesive and a conductive auxiliary agent dispersed in the adhesive, the conductive auxiliary agent is a spherical particle having a spherical core and a conductive film covering the core, an addition ratio of the conductive auxiliary agent in the conductive adhesive layer is 0.1% by volume or more and 1.0% by volume or less, and a first value obtained by adding twice a standard deviation of a particle size of the conductive auxiliary agent to an average particle size of the conductive auxiliary agent is greater than or equal to a thickness of the conductive adhesive layer.