Conductive-Coated Separator for Uniform Lithium Metal Deposition
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Solution Overview
Problem
Lithium metal secondary batteries face issues with lithium dendrite formation leading to short circuits and reduced negative electrode active material density due to the accumulation of a solid electrolyte interphase layer during repeated charge and discharge cycles.
Innovation Solution
A porous conductive coat layer with specific electrical conductivity and surface resistivity is stacked on the surface of a porous membrane separator, positioned on the negative electrode side, to promote uniform lithium deposition and prevent dendrite growth, ensuring a compact and dense active material layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional separator is used in lithium metal secondary batteries, then the battery structure is simple, but lithium dendrites form during repeated charge and discharge cycles, leading to short circuits and reduced active material density
Solution Approach 1:
The separator is constructed as a composite structure combining an alumina base layer with a porous conductive coat layer containing lithium oxide. This composite design provides both mechanical separation function and electrochemical activity, enabling the separator to prevent short circuits while promoting uniform lithium deposition and suppressing dendrite formation through the conductive layer's interaction with lithium ions
Solution Approach 2:
The porous conductive coat layer with controlled porosity (30-70%) allows efficient lithium ion transport while maintaining structural integrity. The porous structure provides multiple pathways for lithium deposition, reducing current density concentration and preventing dendrite formation, thereby improving reliability without significantly increasing device complexity
2Quantity of substance
If lithium metal is used as negative electrode active material to increase capacity, then battery capacity increases, but solid electrolyte interphase layer accumulates during repeated cycles, promoting lithium dendrite formation
Solution Approach 1:
The porous conductive coat layer containing lithium oxide acts as an intermediary between the lithium metal negative electrode and the electrolyte. This intermediate layer modifies the deposition interface, promoting uniform lithium nucleation and growth while suppressing dendrite formation, thereby maintaining high capacity with improved reliability over repeated cycles
Solution Approach 2:
The separator's conductive coat layer changes the electrochemical parameters at the lithium deposition interface by introducing lithium oxide. This modifies the local electric field distribution and nucleation conditions, transforming the deposition process from dendritic growth to uniform layer formation, thus maintaining both high capacity and reliability
3Reliability
If lithium dendrites form during charging, then the battery may short circuit, but also the density of lithium layer on negative electrode decreases, causing excessive expansion
Solution Approach 1:
The porous conductive coat layer creates a more uniform potential distribution across the lithium deposition surface by providing multiple conductive pathways. This equipotential effect promotes uniform current density distribution, preventing localized dendrite formation and ensuring dense, compact lithium layer deposition, thereby simultaneously improving reliability and maintaining negative electrode density
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 reduces the likelihood of short circuits and maintains a compact negative electrode active material layer density even after repeated charge and discharge cycles, enhancing energy efficiency and battery stability.
Implementation Method 1
the electrical conductivity of the porous conductive coat layer is within a range of 1.0×101 to 1.0×105 S/cm, and in which the surface resistivity of the porous conductive coat layer is 200 Ω/cm2 or less
Implementation Method 2
in which lithium is deposited on the negative electrode current collector during charging and dissolved during discharging
Data Source
AI summary
The lithium metal secondary battery of the present invention includes an electrode stack formed by stacking a positive electrode and a negative electrode having a negative electrode current collector with a separator interposed therebetween, and an electrolyte solution, in which lithium is deposited on the negative electrode current collector during charging and dissolved during discharging; the separator includes a porous membrane and a porous conductive coat layer stacked on at least part of the surface of the porous membrane on the side of the negative electrode, in which the electrical conductivity of the porous conductive coat layer is within the range of 1.0×101 to 1.0×105 S/cm, and the surface resistivity of the porous conductive coat layer is 200 Ω/cm2 or less.