Solid-State Battery Interface Mixed Layer for Low-Resistance Bonding
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Solution Overview
Problem
All-solid secondary batteries face issues with interfacial resistance and material damage due to nonuniform pressure during the pressing process, which affects the bonding between the negative electrode layer and the solid electrolyte layer, potentially leading to reduced safety and performance.
Innovation Solution
A mixed layer with a thickness of 2 μm or less is formed between the negative electrode layer and the solid electrolyte layer, comprising both negative electrode layer material and solid electrolyte layer material, with specific thickness and volume ratios to enhance interfacial contact and reduce resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a pressing process is applied to improve interfacial bonding between the negative electrode layer and the solid electrolyte layer, then interfacial bonding is improved, but the negative electrode layer material or the solid electrolyte material may be damaged due to nonuniform pressing force
Solution Approach 1:
A mixed layer is formed in advance between the negative electrode layer and the solid electrolyte layer before the pressing process. This mixed layer acts as a buffer that distributes the pressing force uniformly, preventing material damage while still achieving good interfacial bonding. The mixed layer is created by partially mixing the negative electrode layer material and solid electrolyte layer material, which prepares the interface for subsequent pressing without causing damage.
2Reliability
If the negative electrode layer and solid electrolyte layer are directly bonded, then the structure is simple, but the interfacial resistance is high and interfacial bonding is poor
Solution Approach 1:
A mixed layer is introduced as an intermediary between the negative electrode layer and the solid electrolyte layer. This mixed layer contains both negative electrode layer material and solid electrolyte layer material, creating a gradient interface that reduces interfacial resistance and improves bonding. The mixed layer acts as a transition zone that facilitates better electrical and mechanical contact between the two distinct layers.
3Strength
If the mixed layer thickness is increased to improve interfacial contact, then interfacial bonding is improved, but the output characteristics may be reduced due to increased resistance
Solution Approach 1:
The thickness of the mixed layer is precisely controlled within a specific range (1 nm to 100 nm, preferably 1 nm to 10 nm). This parameter optimization ensures that the mixed layer is thin enough to maintain low resistance and good output characteristics, while still being thick enough to provide sufficient interfacial bonding and contact area. The specific thickness range balances the competing requirements of bonding strength and electrical conductivity.
Data Source
AI summary
Provided are an all-solid secondary battery and a method of preparing the same, wherein the all-solid secondary battery includes a positive electrode layer, a negative electrode layer, and a solid electrolyte layer arranged between the positive electrode layer and the negative electrode layer, wherein a mixed layer having a thickness of 2 μm or less is included between the negative electrode layer and the solid electrolyte layer, the mixed layer includes a negative electrode layer material and a solid electrolyte layer material, a thickness ratio of the negative electrode layer to the mixed layer is 2:1 to 50:1, and a mixing volume ratio of the negative electrode layer to the solid electrolyte in the mixed layer is 2:1 to 1:1.