Buffered Negative Electrode-Electrolyte Assembly for Interface Stability
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Solution Overview
Problem
The detachment of the solid electrolyte from the negative electrode in solid-state lithium batteries contributes to battery failure, particularly due to the loss of contact caused by lithium deposition during cycling.
Innovation Solution
A buffered negative electrode-electrolyte assembly is introduced, comprising a porous negative electrode, a solid-state electrolyte, and a buffer layer with specific electronic and ionic insulating properties, which adheres to both and prevents lithium deposition at the interface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a solid-state electrolyte is used in a lithium battery, then safety and energy density are improved, but detachment from the negative electrode occurs during cycling leading to battery failure
Solution Approach 1:
A buffer layer comprising metal nitride, metal oxide, or metal carbide is introduced as an intermediary between the solid-state electrolyte and the negative electrode. This buffer layer prevents direct contact between the electrolyte and electrode, thereby preventing lithium deposition and detachment issues while maintaining the benefits of solid-state electrolytes.
Solution Approach 2:
The buffer layer is disposed between the solid-state electrolyte and negative electrode before battery assembly and cycling. This preliminary placement prevents lithium deposition and maintains contact stability throughout the battery's operational life, addressing the detachment problem before it can occur.
2Quantity of substance
If lithium metal or alloy is used as negative electrode, then specific capacity and energy density are improved, but volume expansion occurs during cycling causing loss of contact
Solution Approach 1:
The buffer layer acts as a compliant intermediary that can accommodate the volume expansion of lithium metal or alloy electrodes during cycling. This intermediary layer maintains electrical contact and prevents detachment despite the significant volume changes that occur during charge-discharge cycles.
Solution Approach 2:
The buffer layer materials (metal nitride, oxide, or carbide) are selected to have physical and chemical properties that change in response to the electrode's volume expansion, maintaining contact stability while allowing the high-capacity lithium metal or alloy electrode to function at its full potential.
3Device complexity
If solid-state electrolyte directly contacts negative electrode, then device complexity is reduced, but lithium deposition occurs at the interface causing failure
Solution Approach 1:
A thin buffer layer of metal nitride, oxide, or carbide is introduced between the solid-state electrolyte and negative electrode. This minimal addition prevents lithium deposition and interface reactions while maintaining the overall simplicity of the solid-state battery structure and avoiding significant increases in device complexity.
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 buffer layer maintains contact between the solid-state electrolyte and the negative electrode, preventing detachment and enhancing the battery's cycling stability and performance.
Implementation Method 1
the buffer composition has an electronic conductivity that is less than or equal to 1×10−2 times an electronic conductivity of the solid-state electrolyte
Implementation Method 2
the buffer composition has an ionic conductivity less than or equal to 1×10−6 times an ionic conductivity of the solid-state electrolyte
Data Source
AI summary
A buffered negative electrode-electrolyte assembly includes: a porous negative electrode comprising a metal, a transition metal nitride, or a combination thereof; a solid-state electrolyte; and a buffer layer between the porous negative electrode and the solid-state electrolyte. The buffer layer comprising a buffer composition according to Formula (1) MmNnZzHhXx. The buffer composition has an electronic conductivity that is less than or equal to 1×10−2 times an electronic conductivity of the solid-state electrolyte, and the buffer composition has an ionic conductivity less than or equal to 1×10−6 times an ionic conductivity of the solid-state electrolyte.