Solid-State Sulfide Cathode Structure for Polysulfide Stability
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Solution Overview
Problem
Lithium secondary batteries with sulfur-based cathodes face issues such as polysulfide side reactions, ion and electron transfer path disconnection, and solid electrolyte defects leading to reduced lifespan and safety concerns due to the risk of short circuits and fires.
Innovation Solution
An all-solid secondary battery design featuring a lithium-containing sulfide-based cathode active material, a solid electrolyte layer, and an inactive member to prevent side reactions, disconnection of ion and electron transfer paths, and defects, with a specific ratio of initial charge capacities between the cathode and anode active materials to manage volume changes and enhance stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If sulfur-based material is used as cathode active material to increase capacity, then battery capacity increases, but polysulfide side reactions occur that degrade lifespan characteristics
Solution Approach 1:
A lithium phosphate layer is formed on the surface of the sulfur-based cathode active material to act as an intermediary barrier. This layer prevents direct contact between polysulfides and the electrolyte, blocking the harmful side reactions while allowing lithium ion transport, thus maintaining both high capacity and extended lifespan
2Quantity of substance
If volume of sulfur-based material is increased during initial discharging, then charge capacity increases, but transfer path of ions and/or electrons may be disconnected causing deterioration
Solution Approach 1:
A flexible aluminum foil layer is introduced as a structural component that can accommodate volume changes of the sulfur-based material during charging/discharging cycles. This thin film maintains continuous electrical contact and prevents disconnection of electron transfer paths even when the cathode material expands or contracts
Solution Approach 2:
The cathode structure is designed as a composite combining sulfur-based active material with conductive carbon matrix and protective coatings. This composite structure ensures both high charge capacity and maintained electrical conductivity throughout volume changes by providing alternative electron pathways
3Productivity
If defects occur in solid electrolyte layer during manufacturing and/or charging/discharging, then production efficiency is maintained, but cracks occur and grow leading to short circuit
Solution Approach 1:
A protective buffer layer is introduced between the solid electrolyte and electrode materials to prevent stress concentration and crack initiation during manufacturing and operation. This cushioning layer absorbs mechanical stresses and prevents defect propagation, maintaining both manufacturing feasibility and long-term reliability
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 effectively suppresses side reactions, maintains ion and electron transfer integrity, and reduces the risk of short circuits, thereby improving the battery's cycle characteristics and safety by preventing defects in the solid electrolyte layer during manufacturing and charging/discharging.
Implementation Method 1
All-solid batteries using a solid electrolyte instead of an electrolyte have been proposed... a solid electrolyte layer disposed between the cathode layer and the anode layer
Implementation Method 2
a cathode active material layer disposed on one side or two sides of the cathode current collector, the cathode active material layer includes a lithium-containing sulfide-based cathode active material... capable of intercalating and deintercalating lithium ions
Implementation Method 3
Lithium secondary batteries produce electrical energy through oxidation and reduction reactions if lithium ions are intercalated/deintercalated into/from a cathode and anode
Data Source
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AI summary
Provided is an all-solid secondary battery including a cathode layer, an anode layer, and a solid electrolyte layer disposed between the cathode layer and the anode layer, wherein the cathode layer includes a cathode current collector and a cathode active material layer disposed on one side or two sides of the cathode current collector, the cathode active material layer includes a lithium-containing sulfide-based cathode active material, the lithium-containing sulfide-based cathode active material includes Li2S, a Li2S-containing composite, or a combination thereof, the all-solid secondary battery includes a first inactive member disposed on one side of the cathode layer, the anode layer includes an anode current collector and a first anode active material layer disposed on one side of the anode current collector.