Block Polymer Protective Layer for Lithium Metal Dendrite Suppression
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Solution Overview
Problem
Lithium secondary batteries face challenges in controlling lithium metal deposition and suppressing dendrite formation due to the limitations of existing lithium-ion conductive protective films, which lead to deterioration in cycle characteristics and side reactions.
Innovation Solution
A lithium secondary battery with a negative electrode surface covered by a protective layer composed of a block polymer, where a first polymer segment with high mechanical strength and a second polymer segment with high lithium-ion conductivity are bound together, forming a stable and conductive film that inhibits dendrite growth and penetration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyethylene oxide (PEO) or polymethyl methacrylate (PMMA) are used as the lithium-ion conductive protective film, then lithium-ion conductivity is improved, but the film dissolves in liquid electrolyte and mechanical strength deteriorates with cycling
Solution Approach 1:
The protective film uses a composite structure combining a polymer coating layer with a porous inorganic layer. The polymer layer provides lithium-ion conductivity while the porous inorganic layer (containing alumina, silica, or titania particles) provides mechanical strength and prevents dissolution in liquid electrolyte, resolving the contradiction between conductivity and strength
2Strength
If polyvinylidene fluoride (PVdF) is used as the protective film, then mechanical strength is improved, but sufficient lithium-ion conductivity cannot be obtained
Solution Approach 1:
The composite protective film combines PVdF polymer with porous inorganic materials. The PVdF provides the necessary mechanical strength while the porous inorganic layer with high ion conductivity pathways ensures sufficient lithium-ion conductivity, resolving the contradiction between strength and conductivity
3Reliability
If the protective film strength is low, then lithium-ion conductivity is maintained, but dendrites penetrate the film causing side reactions and cycle characteristic deterioration
Solution Approach 1:
The porous inorganic layer embedded in the polymer coating acts as a physical barrier that prevents dendrite penetration while maintaining lithium-ion conductivity through its porous structure. This composite approach simultaneously addresses conductivity requirements and dendrite suppression needs
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 use of a block polymer protective layer enhances the mechanical strength and lithium-ion conductivity of the film, leading to improved cycle characteristics and reduced side reactions, resulting in a more stable and efficient lithium secondary battery.
Implementation Method 1
a non-aqueous electrolyte having lithium ion conductivity
Implementation Method 2
a positive electrode that absorbs lithium ions during discharge and releases the lithium ions during charge
Data Source
AI summary
A lithium secondary battery includes a positive electrode that absorbs lithium ions during discharge and releases the lithium ions during charge, a negative electrode at which a lithium metal deposits during charge and from which the lithium metal dissolves during discharge, and a non-aqueous electrolyte having lithium ion conductivity. The surface of the negative electrode is covered with a protective layer. The protective layer includes a block polymer in which a first polymer segment having a repeating structure of a monomer unit A and a second polymer segment having a repeating structure of a monomer unit B are bound together.