Defluorinated Fluoropolymer SEI Layer for Lithium Anode Dendrite Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium-ion batteries face issues with 'mossy' lithium structures and lithium dendrite growth due to large volume changes and high reactivity, leading to reduced cycle efficiency and application limitations.
Innovation Solution
The method involves applying a fluoropolymer film to a lithium-based host material, followed by defluorination through heating to create a solid electrolyte interface (SEI) layer with defluorinated fluoropolymers and at least 5 wt.% LiF, which suppresses dendrite growth and provides mechanical protection, allowing for the use of lithium anodes in non-inert environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium metal electrode is used to achieve high energy density, then energy density is improved, but lithium dendrite growth and mossy structure formation occur reducing cycle efficiency
Solution Approach 1:
A fluoropolymer coating is applied as an intermediary layer between the lithium metal electrode and the electrolyte. This coating acts as a mediator that prevents direct harmful interactions while allowing beneficial lithium ion transport, thereby suppressing dendrite growth and improving cycle efficiency without sacrificing the high energy density benefits of lithium metal
Solution Approach 2:
The fluoropolymer coating changes the interfacial parameters at the lithium electrode surface by forming a solid electrolyte interface layer with specific composition (at least 5 wt% LiF). This parameter change in the interface properties suppresses dendrite formation while maintaining high ionic conductivity for lithium ions, enabling both high energy density and improved cycle efficiency
2Use of energy by moving object
If lithium metal electrode is used, then high reactivity and energy density are achieved, but mossy lithium structures form reducing battery performance
Solution Approach 1:
The fluoropolymer coating serves as a protective intermediary that stabilizes the lithium metal structure by preventing direct exposure to the electrolyte environment. This intermediary layer suppresses the formation of mossy lithium structures while allowing the high reactivity of lithium to be harnessed for high energy density
Solution Approach 2:
The fluoropolymer coating is applied in advance before battery assembly and operation. This preliminary action creates a pre-formed solid electrolyte interface layer that proactively prevents mossy structure formation from the outset, rather than attempting to address the problem after it occurs
3Reliability
If fluoropolymer film is applied to lithium-based host material, then SEI layer with LiF is formed suppressing dendrite growth, but additional manufacturing steps are required
Solution Approach 1:
The fluoropolymer coating process utilizes plasma treatment or electron beam irradiation to induce defluorination and form LiF-containing SEI layers. These parameter changes in the coating process enable dendrite suppression through chemical modification of the fluoropolymer surface, achieving reliable dendrite suppression while keeping the manufacturing process relatively simple
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 SEI layer effectively prevents lithium dendrite growth and 'mossy' structure formation, enhancing the mechanical protection and cycle efficiency of lithium anodes, enabling their use in various applications including hybrid-electric vehicles.
Implementation Method 1
defluorinating the fluoropolymer film by heating to produce a lithium electrode having a solid electrolyte interface (SEI) layer including defluorinated fluoropolymers and at least about 5 wt. % LiF
Implementation Method 2
The methods can further include removing a natural passivation layer from the exposed surface of the lithium-based host material onto which the fluoropolymer film is subsequently applied
Data Source
AI summary
Methods for manufacturing electrodes include applying a fluoropolymer film to a lithium-based host material, defluorinating the fluoropolymer film by heating to produce a lithium electrode having a solid electrolyte interface (SEI) layer including defluorinated fluoropolymers and at least about 5 wt. % LiF. The fluoropolymers can include one or more of fluorinated ethylenepropylene, perfluoroalkoxy alkanes, vinylidenefluoride, and copolymers of perfluoromethylvinylether and tetrafluoroethylene. The fluoropolymers can include one or more fluorinated monomers, including hexafluoropropylene, tetrafluoroethylene, ethylene-tetrafluoroethylene, perfluoroethers, and vinylidene fluoride. The —CF3 functional groups of the defluorinated fluoropolymers can be about 3 wt. % to about 10 wt. % of the SEI layer. The SEI layer can include about 30 wt. % to about 50 wt. % LiF. The method can include assembling a battery cell by disposing a battery separator between a cathode and the electrode, and disposing the battery separator, the cathode, and the electrode in an electrolyte.