All-Solid Battery Electrode Primer Layer Adhesion
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Solution Overview
Problem
All-solid state secondary batteries face challenges in maintaining adhesiveness between the current collector and the electrode active material layer due to repeated expansion and contraction during charging and discharging, leading to peeling issues and difficulties in achieving desired cycle characteristics, discharge load characteristics, and vibration resistance.
Innovation Solution
Incorporating a primer layer between the current collector and the electrode active material layer with a specific binder distribution, where the binder content increases sequentially from the current collector side towards the electrode active material layer, and using an inorganic solid electrolyte with ion conductivity from Group 1 or Group 2 metals, along with a binder system comprising different resin types.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a conventional electrode structure without a primer layer is used, then the device complexity is reduced, but the adhesiveness between current collector and electrode active material layer deteriorates due to repeated expansion and contraction during charging and discharging
Solution Approach 1:
A primer layer is introduced as an intermediary between the current collector and the electrode active material layer. This primer layer includes a binder that forms a crosslinked structure, acting as a mediator that maintains adhesiveness during repeated expansion and contraction of the active material during charging and discharging cycles.
Solution Approach 2:
The primer layer utilizes composite material structure where a binder containing specific functional groups (such as carboxyl groups) forms a crosslinked network. This crosslinked composite structure provides enhanced mechanical strength and adhesion stability, preventing peeling between the current collector and electrode active material layer while accommodating volume changes.
2Strength
If the binder content is uniformly distributed in the primer layer, then the manufacturing process is simplified, but the adhesiveness and stability under vibration and discharge load conditions deteriorate
Solution Approach 1:
The binder in the primer layer is distributed with non-uniform concentration, creating local quality variations. The binder content is higher in regions experiencing greater stress during vibration and discharge load, providing enhanced local adhesion strength where needed most, while maintaining overall structural integrity.
3Reliability
If an organic electrolytic solution is used, then the ease of manufacture is improved, but safety and reliability deteriorate due to liquid leakage and short-circuit risks
Solution Approach 1:
The electrolyte is changed from liquid organic electrolytic solution to solid inorganic solid electrolyte, representing a fundamental parameter change from liquid to solid state. This eliminates liquid leakage risks and short-circuit concerns associated with organic electrolytes, significantly improving safety and reliability, although it requires adjustments in manufacturing processes for handling and assembly.
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 enhances the adhesiveness and stability of the electrode structure, resulting in improved cycle characteristics, discharge load characteristics, and vibration resistance, ensuring the battery maintains performance under various conditions.
Implementation Method 1
an inorganic solid electrolyte having ion conductivity of a metal belonging to Group 1 or Group 2 in the periodic table
Implementation Method 2
the sulfur atom included in the inorganic solid electrolyte and a carbon-carbon double bond of the diene polymer form a crosslinked structure such that the peel strength (binding properties between the current collector and the electrode active material layer) is excellent
Data Source
AI summary
Provided are an electrode sheet for an all-solid state secondary battery and an all-solid state secondary battery including the electrode sheet. The electrode sheet includes a current collector, a primer layer, and an electrode active material layer in this order,in which the electrode active material layer includes an inorganic solid electrolyte having ion conductivity of a metal belonging to Group 1 or Group 2 in the periodic table, an active material, and a binder a1,the primer layer includes the binder a1 and a binder a2, andin a case where the primer layer is equally divided into six sub-layers in a thickness direction and the six sub-layers are set as a first sub-layer to a sixth sub-layer in order from the electrode active material layer side toward the current collector side, a relationship between a ratio B1 of a content of a1 to a total content of a1 and a2 in the first sub-layer and a ratio B6 of a content of a1 to a total content of a1 and a2 in the sixth sub-layer satisfies B1>B6.