Conformable Polymer-Coated Lithium Metal Electrode for Dendrite Control
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Solution Overview
Problem
Lithium metal batteries face issues with poor cycle life, volumetric expansion, and safety concerns due to dendrite formation and flammable organic electrolytes, limiting their use as rechargeable batteries, especially when using elemental sulfur as the positive electrode.
Innovation Solution
The use of a lithium ion conductive conformable polymer, such as block or graft copolymers, that selectively allows lithium ion transport while blocking other ions and solvents, and adjusts to volume changes, acting as a solid electrolyte to prevent dendrite formation and the polysulfide shuttle effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If flammable organic electrolytes are used in lithium metal batteries, then high ionic conductivity is achieved, but safety concerns arise due to dendrite formation and potential violent combustion
Solution Approach 1:
The patent changes the physical state of the electrolyte from liquid to solid by using a polymer electrolyte membrane. This parameter change eliminates the flammability issue inherent in liquid organic electrolytes while maintaining ionic conductivity necessary for battery operation. The solid polymer electrolyte prevents dendrite formation through its mechanical properties and selective ion transport capability.
Solution Approach 2:
The polymer electrolyte membrane acts as an intermediary between the lithium metal electrodes, providing a controlled pathway for ion transport. This intermediary structure replaces the direct contact between liquid electrolyte and electrodes, thereby preventing uncontrolled dendrite growth and eliminating the combustion risk associated with flammable liquid electrolytes.
2Quantity of substance
If lithium metal batteries are manufactured by conventional methods, then high capacity is achieved, but poor cycle life and volumetric expansion occur
Solution Approach 1:
The patent changes the electrolyte from liquid to solid polymer form, which fundamentally alters the mechanical and electrochemical environment at the electrode-electrolyte interface. This parameter change prevents volumetric expansion during cycling by providing mechanical constraint and maintains stable lithium plating/stripping, thereby extending cycle life while preserving high lithium capacity.
Solution Approach 2:
The polymer electrolyte membrane provides locally optimized conditions at the electrode interface by enabling uniform lithium ion distribution during plating and stripping. This local quality control prevents localized stress concentration and volumetric expansion, thereby improving cycle life while maintaining high capacity utilization.
3Quantity of substance
If elemental sulfur is used as the positive electrode, then higher specific capacity is achieved, but the polysulfide shuttle effect reduces cycle life
Solution Approach 1:
The polymer electrolyte membrane acts as a physical barrier and selective mediator between the sulfur cathode and lithium anode. It allows lithium ion transport necessary for charge/discharge while blocking polysulfide species, thereby preventing the polysulfide shuttle effect that would otherwise dissolve active material and reduce cycle life, while maintaining the high specific capacity advantage of sulfur cathodes.
Solution Approach 2:
The polymer electrolyte membrane provides a controlled porous or semi-permeable structure that selectively permits lithium ion passage while restraining larger polysulfide molecules. This selective permeability enables the battery to achieve high specific capacity from sulfur while preventing polysulfide dissolution and shuttle effects that would degrade cycle life.
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
This approach enhances the safety and performance of lithium metal batteries by preventing dendrite formation and the polysulfide shuttle, leading to improved cycle life and safety, particularly in Li—S batteries.
Implementation Method 1
the lithium ion conductive conformable polymer being configured to selectively allow lithium ions to electrophorese through the polymer under an applied voltage
Implementation Method 2
the lithium ion conductive conformable polymer is a block or graft copolymer, with microphase separated first domains and second domains
Implementation Method 3
the first domains formed from first segments, the first segments configured to solvate lithium ions and to provide continuous conductive pathways for the transport of lithium ions
Implementation Method 4
a lithium ion conductive conformable polymer coats the outer face of the layer of lithium metal
Data Source
AI summary
A lithium metal electrode comprises a layer of lithium metal coating a conductive substrate, the layer of lithium metal having no more than five ppm of non-metallic elements by mass. The layer of lithium metal is in turn coated with a lithium ion conductive conformable polymer, thereby providing the negative electrode and the solid electrolyte for a rechargeable lithium metal battery that further includes a positive electrode. Optionally, the positive electrode includes elemental sulfur in a conductive matrix. The conformable polymer coated lithium metal electrode may be manufactured by a process involving electroplating lithium metal through a conformable polymer coated conductive substrate, for which the conformable polymer coated conductive substrate has been prepared by coating the conductive substrate in a solution of the conformable polymer followed by evaporating the solvent. Alternatively, a lithium metal electrode may be coated directly with conformable polymer. Rechargeable lithium batteries according to embodiments of the invention have improved cycle life and combustion resistance compared to lithium metal batteries manufactured by conventional methods.