Dual Anode-Protecting Layers for Lithium Metal Battery Stability
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Solution Overview
Problem
Lithium metal batteries face challenges with lithium metal dendrite formation and reactions between lithium metal and electrolyte, leading to internal short circuits and thermal runaway, which have hindered their commercialization due to safety and cycling stability issues.
Innovation Solution
A lithium metal secondary battery design incorporating a first anode-protecting layer of electron-conducting materials like graphene sheets and a second anode-protecting layer of high-elasticity elastomers, which together reduce dendrite formation and maintain a stable lithium ion interface, preventing unwanted reactions and ensuring uniform ion deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium metal is used as anode active material to achieve high capacity, then energy density is improved, but dendrite formation occurs leading to safety issues
Solution Approach 1:
A protective layer comprising a vacuum-evaporated thin film of a Li ion-conducting polymer is introduced as an intermediary between the lithium metal anode and the electrolyte. This intermediary layer enables lithium ion transfer while preventing direct contact between lithium metal and electrolyte, thereby eliminating dendrite formation and improving safety without sacrificing energy density.
2Use of energy by moving object
If lithium metal is used as anode active material to achieve high capacity, then energy density is improved, but cycling stability deteriorates due to dendrite formation
Solution Approach 1:
The Li ion-conducting polymer protective layer serves as a stable intermediary that maintains consistent lithium ion transfer during repeated charge-discharge cycles. This prevents dendrite formation and the associated capacity fade, thereby improving cycling stability while preserving the high energy density benefits of lithium metal.
3Reliability
If protective surface layer is applied to prevent dendrite formation, then safety is improved, but device complexity increases
Solution Approach 1:
A thin film of Li ion-conducting polymer is used as the protective layer, which is deposited by vacuum evaporation. This thin film approach provides effective dendrite prevention and safety improvement while minimizing the increase in device complexity and maintaining a relatively simple anode structure.
4Duration of action of stationary object
If vacuum-evaporated thin film of Li ion-conducting polymer is used to stabilize anode, then cycling stability is improved, but manufacturing complexity increases
Solution Approach 1:
The vacuum evaporation process deposits a thin film of Li ion-conducting polymer that can be applied directly to the anode structure. This thin film formation method improves cycling stability while keeping manufacturing relatively simple compared to multi-layer or complex coating processes.
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 dual anode-protecting layers significantly enhance the safety and cycling stability of lithium metal batteries by preventing dendrite formation and reducing the formation of 'dead lithium' particles, thereby improving the battery's capacity retention and cycle life.
Implementation Method 1
The surface layer is also electronically conductive so that the ions will be uniformly attracted back onto the metal anode during electrodeposition
Implementation Method 2
a vacuum-evaporated thin film of a Li ion-conducting polymer interposed between the Li metal anode and the electrolyte
Implementation Method 3
comprising an elastomer having a fully recoverable tensile elastic strain from 2% to 1,000%
Data Source
AI summary
The invention provides a method of improving the anode stability and cycle-life of a lithium metal secondary battery. The method comprises implementing two anode-protecting layers between an anode active material layer and an electrolyte/separator assembly. These two layers comprise (a) a first anode-protecting layer having a thickness from 1 nm to 100 μm, a specific surface area greater than 50 m2/g and comprising a thin layer of electron-conducting material selected from graphene sheets, carbon nanotubes, carbon nanofibers, carbon or graphite fibers, expanded graphite flakes, metal nanowires, conductive polymer fibers, or a combination thereof; and (b) a second anode-protecting layer having a thickness from 1 nm to 100 μm and comprising an elastomer having a fully recoverable tensile elastic strain from 2% to 1,000% (preferably >10%) and a lithium ion conductivity from 10−8 S/cm to 5×10−2 S/cm.