Polyolefin Nanofilament Separator for Lithium Dendrite Control
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Solution Overview
Problem
Existing battery separators face challenges in achieving low internal resistance, good ionic conductivity, and preventing lithium metal dendrite formation, while also being cost-effective and easy to manufacture, especially for lithium-ion batteries.
Innovation Solution
A battery separator comprising a porous sheet of polyolefin filaments with an average diameter of less than 1 μm, produced using a process involving infrared radiation heating under reduced pressure and pressure difference, which results in continuous, high-strength nanofilaments with minimal resin lumps and uniform diameter distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If electro-spinning method is used to create nanoscale fibers, then fiber fineness is improved, but process complexity and cost increase due to solvent requirements and high voltage equipment
Solution Approach 1:
The invention extracts and eliminates the solvent from the electro-spinning process, using only molten polymer and high voltage to create nanofibers. This removes the need for solvent handling, drying chambers, and solvent recovery systems, dramatically simplifying the process while maintaining nanoscale fiber production capability
Solution Approach 2:
The invention introduces a charged droplet intermediary that carries molten polymer through the high voltage field without requiring solvent. The charged droplet acts as a mediator between the polymer melt and the collecting surface, enabling fiber formation through electrostatic forces alone
2Manufacturing precision
If electro-spinning method is used, then fiber fineness is improved, but production cost increases due to solvent and equipment requirements
Solution Approach 1:
By removing solvent from the process, the invention eliminates costs associated with solvent purchase, handling safety infrastructure, drying energy, and solvent recovery systems, significantly reducing production costs while maintaining nanoscale fiber quality
Solution Approach 2:
The invention uses inexpensive molten polymer directly without requiring expensive solvent systems or complex equipment, making the process economically viable for mass production of nanofiber separators
3Ease of manufacture
If conventional fiber methods are used, then manufacturing is simpler, but fiber diameter is too large and resin lumps are generated
Solution Approach 1:
The invention changes the fundamental parameters of fiber formation by using electrostatic forces instead of mechanical cutting or thermal melting. This allows continuous fiber production at nanoscale diameters without the resin lumps that occur in conventional methods, while maintaining manufacturing simplicity
4Strength
If laser heating is used for filament drawing, then fiber strength is improved, but equipment complexity and cost increase
Solution Approach 1:
The invention removes the laser heating step from the filament drawing process, relying instead on the natural alignment of polymer chains during electro-spinning. This eliminates expensive laser equipment while producing fibers with sufficient strength for battery separator applications
Solution Approach 2:
The polymer chains self-align and self-organize during the electro-spinning process without external heating, creating strong fibers through inherent molecular orientation rather than thermally-induced alignment
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 provides a high-performance battery separator with low internal resistance, enhanced ionic conductivity, and improved safety by preventing lithium dendrite formation, while being cost-effective and easier to manufacture, suitable for both large and small lithium-ion batteries.
Implementation Method 1
good ionic conductivity
Implementation Method 2
infrared radiation heating
Implementation Method 3
pressure difference
Data Source
AI summary
Disclosed is a highly safe battery separator, in particular a separator for a lithium ion secondary battery, which reduces internal resistance, achieves good ionic conductivity, prevents passing of electrode active materials, and also prevents electrical short circuit by controlling deposition of lithium metal (dendrite). Also disclosed is a means for stably producing the battery separator with high productivity. Specifically disclosed are: a battery separator which is composed of a porous polyolefin sheet that is formed from a group of polyolefin nanofilaments that have an average filament diameter of less than 1 μm and a filament size distribution of 0.2 or less; and a means for producing the battery separator.