Ferritic Stainless Steel Current Collector for Sulfide Solid-State Batteries
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Solution Overview
Problem
Austenitic stainless steels used as current collectors in sulfide-based solid-state batteries face issues with work hardening, increased manufacturing costs, and insufficient sulfidation resistance and adhesion due to reactions with sulfide-based solid electrolytes, leading to battery performance and safety concerns.
Innovation Solution
A ferritic stainless steel sheet with a chemical composition of 16% or more Cr, featuring a stable and dense Fe and Cr oxide film and an uneven surface structure, is developed to enhance sulfidation resistance and adhesion. The manufacturing method involves removing the oxide film, etching in an active potential region, and immersing or electrolyzing in an oxidizing solution to form a stable Cr oxide film and improve surface topography.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If austenitic stainless steel is used as current collector, then sulfidation resistance is improved, but work hardening occurs during rolling requiring increased number of rolling passes and intermediate annealing
Solution Approach 1:
The invention changes the material parameter from austenitic stainless steel to ferritic stainless steel with specific composition (16-32% Cr, 0.03-1.00% C, 0.01-2.00% Si, 0.01-1.00% Mn). This parameter change resolves the contradiction by providing a material that is both rollable without severe work hardening and resistant to sulfidation through high Cr content forming protective oxide films.
2Productivity
If ferritic stainless steel is used to avoid work hardening, then productivity is improved, but sulfidation resistance becomes insufficient
Solution Approach 1:
The invention adjusts the chemical composition parameters of ferritic stainless steel, specifically setting Cr content at 16-32% to form protective oxide films that provide sulfidation resistance, while maintaining the ferritic structure for good rollability. This parameter optimization resolves the contradiction between productivity and reliability.
3Ease of manufacture
If ferritic stainless steel is used, then manufacturing cost is reduced, but adhesion between current collector and sulfide-based solid electrolyte deteriorates
Solution Approach 1:
The invention optimizes the surface composition parameters by controlling Cr content (16-32%) and performing surface treatment to form a Cr-rich oxide film. This parameter change improves adhesion between the ferritic stainless steel and sulfide-based solid electrolyte while maintaining the cost advantages of ferritic steel.
4Reliability
If Cr content is increased to improve sulfidation resistance, then sulfidation resistance is improved, but manufacturing cost increases
Solution Approach 1:
The invention sets the Cr content within the optimized range of 16-32%, which is sufficient to form protective oxide films for sulfidation resistance but not excessively high to cause unnecessary cost increase. This parameter optimization balances reliability and manufacturing cost.
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 ferritic stainless steel sheet exhibits excellent sulfidation resistance and adhesion, extending battery life and ensuring safety by suppressing sulfurization and enhancing the interface between the steel and sulfide-based solid electrolyte.
Implementation Method 1
immersing or electrolyzing in an oxidizing solution and in a passive potential region of the ferritic stainless steel sheet to form a stable and dense Fe and Cr oxide film
Implementation Method 2
immersing or electrolyzing in an oxidizing solution and in a passive potential region of the ferritic stainless steel sheet
Data Source
AI summary
Provided is a ferritic stainless steel sheet for current collectors for sulfide-based solid-state batteries, which has excellent sulfidation resistance and adhesiveness. The ferritic stainless steel sheet has a component composition containing Cr in an amount of 16% by mass or more, wherein the surface of the ferritic stainless steel sheet has an uneven structure having recessed portions and projecting portions, the average height of the projecting portions is 20 to 50 nm inclusive, the average distance between the projecting portions is 20 to 200 nm inclusive, and the [Cr]/[Fe], i.e., the ratio of the atom concentration of Cr that is present in a form other than the metal form to the atom concentration of Fe that is present in a form other than the metal form, on the surface of the ferritic stainless steel sheet is 1.0 or more.