All-Solid Secondary Battery Cathode for Dendrite-Safe High-Rate Cycling
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Solution Overview
Problem
Lithium-based secondary batteries face challenges such as the formation of lithium dendrites and dead lithium during charging, leading to reduced reversibility of electrode reactions, increased risk of short circuits, and accelerated battery degradation due to volume changes in the anode.
Innovation Solution
An all-solid secondary battery design is proposed, featuring a cathode with a composite cathode active material comprising M2S and molybdenum sulfide (Mo6S8), along with a carbonaceous material and a solid electrolyte, which improves impedance characteristics and reduces internal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium metal is utilized in the anode to increase capacity, then the battery capacity is improved, but lithium dendrites and dead lithium form during charging, leading to reduced reversibility and increased short circuit risk
Solution Approach 1:
A solid electrolyte layer is introduced as an intermediary between the lithium metal anode and cathode. This solid electrolyte acts as a mediator that allows ionic conduction while physically blocking the growth of lithium dendrites and preventing direct electrical contact that would cause short circuits, thereby maintaining battery capacity while improving reversibility and safety
Solution Approach 2:
The electrolyte is changed from liquid to solid state, fundamentally altering the physical parameters of the battery system. This parameter change (phase transition from liquid to solid) enables the electrolyte to mechanically suppress lithium dendrite growth while maintaining ionic conductivity, resolving the contradiction between capacity and reliability
2Quantity of substance
If lithium metal is utilized in the anode, then capacity is increased, but the risk of short circuit between lithium metal and cathode increases due to dendrite growth and molten lithium elution
Solution Approach 1:
The solid electrolyte serves as a protective intermediary layer that physically separates the lithium metal anode from the cathode. It blocks the harmful effects of dendrite penetration and molten lithium elution while maintaining necessary ionic transport, thus preserving capacity while eliminating short circuit risks
Solution Approach 2:
The solid electrolyte provides beforehand cushioning by preemptively blocking the pathways through which lithium dendrites and molten lithium could cause short circuits. This preventive measure is built into the battery structure before operation, cushioning against potential harmful effects
3Quantity of substance
If the anode thickness is increased to store more lithium, then capacity is improved, but degradation is accelerated due to significant volume changes during charging and discharge
Solution Approach 1:
The solid electrolyte changes the mechanical constraint parameters of the system, providing rigid support that constrains the anode volume changes during cycling. This allows thicker anodes to be used for higher capacity while the solid electrolyte's mechanical properties prevent the excessive expansion and contraction that would otherwise accelerate degradation
Solution Approach 2:
The solid electrolyte provides localized mechanical support and constraint at the electrode-electrolyte interface, creating a stable local environment that prevents harmful volume changes of the thick anode during charging and discharging, thereby extending battery lifespan
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 improved battery design enhances high-rate capability and lifespan by suppressing irregular lithium plating, reducing the risk of short circuits, and mitigating volume changes in the anode, thereby extending the battery's cycling performance and safety.
Implementation Method 1
a solid electrolyte layer between the cathode layer and the anode layer
Implementation Method 2
the cathode active material layer includes a composite cathode active material, a carbonaceous material, and a solid electrolyte
Data Source
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AI summary
An all solid secondary battery and a method of preparing the same are provided. The all solid secondary battery includes a cathode layer, an anode layer, and a solid electrolyte layer between the cathode layer and the anode layer, wherein the cathode layer includes a cathode current collector and a cathode active material layer on one side or both sides (e.g., opposite sides) of the cathode current collector, wherein the cathode active material layer includes a composite cathode active material, a carbonaceous material, and a solid electrolyte, and the composite cathode active material including a composite including M2S and molybdenum sulfide (MoeSs) wherein M is alkali metal, the alkali metal is lithium (Li) or sodium (Na), and the anode layer includes an anode current collector and a first anode active material layer on one side of the anode current collector.