All-Solid Battery Composite Electrolyte for Defect Reduction
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Solution Overview
Problem
All-solid secondary batteries with sulfide-based solid electrolytes face physical defects during the pressing process, leading to potential short-circuits and reduced battery capacity due to the brittleness of the sulfide-based solid electrolyte and step differences between layers.
Innovation Solution
The battery design incorporates a composite structure with a composite solid electrolyte and an insulating member, where the composite solid electrolyte is placed centrally and the insulating member surrounds the outer surfaces of the second solid electrolyte layer, reducing interfacial resistance and preventing physical defects and short-circuits by enhancing bonding strength and adhesiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sulfide-based solid electrolyte is used in an all-solid secondary battery, then the energy density and safety are improved compared to lithium-ion batteries with electrolytic solutions, but physical defects and short-circuits occur during the pressing process due to the brittleness of the sulfide-based solid electrolyte and step differences between layers
Solution Approach 1:
The solid electrolyte system is segmented into multiple layers: a first solid electrolyte layer adjacent to the cathode, a second solid electrolyte layer adjacent to the anode, and a composite solid electrolyte layer positioned between them. This segmentation allows each layer to serve specific functions - the outer layers provide interface stability while the composite layer enhances bonding strength and reduces interfacial resistance, thereby preventing physical defects during pressing while maintaining safety.
Solution Approach 2:
A composite solid electrolyte layer is introduced between the first and second solid electrolyte layers. This composite material combines the advantages of different solid electrolyte materials to achieve both high bonding strength with electrodes (preventing physical defects during pressing) and low interfacial resistance (maintaining electrical performance and safety). The composite structure resolves the contradiction between manufacturing precision and reliability.
2Quantity of substance
If a sulfide-based solid electrolyte is used, then the energy density is improved, but the brittleness of the electrolyte leads to short-circuits and reduced battery capacity
Solution Approach 1:
The composite solid electrolyte layer combines materials with complementary properties - maintaining the high ionic conductivity needed for energy density while incorporating phases that resist brittleness and dendrite growth. This composite approach preserves battery capacity by preventing short-circuits during cycling, thus resolving the contradiction between energy density and reliability.
Solution Approach 2:
The multi-layer solid electrolyte structure with the composite layer in between acts as a cushioning layer that prevents direct contact between the brittle outer solid electrolyte layers and the electrodes. This beforehand cushioning prevents crack propagation and short-circuit formation during battery operation, preserving battery capacity while maintaining high energy density.
3Device complexity
If a simple solid electrolyte structure is used, then the device complexity is reduced, but interfacial resistance increases and bonding strength decreases leading to physical defects
Solution Approach 1:
The solid electrolyte system is divided into three functional layers: first solid electrolyte layer (cathode interface), composite solid electrolyte layer (intermediate), and second solid electrolyte layer (anode interface). This segmentation allows optimization of bonding strength at each interface without significantly increasing overall device complexity, as the layers are stacked in a straightforward configuration that maintains manufacturing simplicity while enhancing interfacial properties.
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
This configuration effectively reduces physical defects and short-circuits, improving the cycle characteristics and energy density of the battery by maintaining bonding strength and preventing lithium dendrite growth, thus enhancing the overall performance and safety of the all-solid secondary battery.
Implementation Method 1
the composite solid electrolyte is on a central portion of the second solid electrolyte layer and includes an ion conductor and a lithium salt
Implementation Method 2
the insulating member is on peripheral portions of the second solid electrolyte layer and is adjacent to or around one or more outer surfaces of the composite solid electrolyte
Data Source
AI summary
An all-solid secondary battery includes: a cathode layer; an anode layer; a first solid electrolyte layer adjacent to the cathode layer; and a second solid electrolyte layer adjacent to the anode layer. The cathode layer includes a cathode current collector and a cathode active material layer on the cathode current collector. The anode layer includes an anode current collector and a first anode active material layer or a third anode active material layer on the anode current collector. A composite solid electrolyte and an insulating member are located between the first solid electrolyte layer and the second solid electrolyte layer, wherein the composite solid electrolyte is on a central portion of the second solid electrolyte layer and includes an ion conductor and a lithium salt, and the insulating member is on peripheral portions of the second solid electrolyte layer and is around outer surfaces of the composite solid electrolyte.