Electrospining Machine: Progress of electrospun pvdf-based polymers for lithium-ion battery separators

Background

Lithium-ion batteries (LIBs) (Table A1: all acronyms and their explanations) have the advantages of high energy density, long cycle life, and no memory effect, so they have been widely used in portable electronic products, new energy vehicles, civil airplanes, and other fields. In addition, as a new type of energy source, lithium-ion batteries also help alleviate the environmental pollution and energy crisis caused by the depletion of traditional energy sources, and realize the goal of carbon neutrality.

The main point of this paper

The role of diaphragm in lithium ion battery:

The diaphragm is a key component of lithium-ion batteries, which not only promotes the free flow of lithium ions and ensures electrochemical performance, but also serves as a physical isolation to avoid positive and negative electrode contact reaction

Limitations of commercial polyolefin diaphragms:

Commercial polyolefin diaphragms suffer from poor electrolyte wetting, electrolyte spillage and ignition during depressurization or puncture, and thermal runaway due to low melting point, all of which limit the development of high-performance lithium-ion batteries

PVDF's potential as a diaphragm material:

Polyvinylidene fluoride (PVDF) is a potential candidate as a polyolefin separator for lithium-ion batteries due to its non-toxicity, heat resistance, and high dielectric constant

Preparation method of PVDF-based diaphragm:

Methods for preparing lithium-ion battery separators include template synthesis, phase separation, and electrospinning. Electrospinning technology has become an important technology for the continuous preparation of nanofiber separators with large specific surface area and high porosity due to its advantages of simple operation, low cost and high efficiency

Advantages of electrospun PVDF-based diaphragms:

Electrospun PVDF-based diaphragms are characterized by controllable morphology, diverse structure, and excellent performance (e.g., thermal stability), which can solve the problems of poor wettability and low safety of commercial polyolefin separators for lithium-ion battery applications.

Application of base diaphragms in lithium-ion batteries: research progress, key parameters and challenges

Research hotspots of electrospun silk PVDF-based diaphragm

Application of electrospinning technology:

Electrospinning technology has become an important technology for the continuous preparation of nanofiber diaphragms with large specific surface area and high porosity due to its advantages of simple operation, low cost and high efficiency

Advantages of PVDF-based diaphragm:

Electrospun PVDF-based diaphragms are characterized by controllable morphology, diversified structure, and excellent performance (e.g., thermal stability), which can effectively solve the problems of poor wettability and low safety of commercial polyolefin diaphragms in LIB applications.

Key parameters affecting diaphragm performance

Electrospinning solution preparation process:

Conditions such as solvent selection, solution concentration, and liquid film evaporation time all have different degrees of influence on the structure and performance of PVDF membranes

Electrospinning process parameters:

Including voltage, working distance, supply rate, etc., these parameters have a significant effect on the diameter and morphology of nanofiber

Post-treatment methods:

Such as heat treatment, which plays an important role in the final structure and properties of the fibers, including the thermal stability and porosity of the fibers

Challenges for PVDF-based LIB diaphragms

Improving electrochemical properties:

Although electrospun PVDF-based diaphragms have made progress in improving the electrochemical properties of LIB, further research is needed to improve their ionic conductivity and electrochemical stability

Enhanced safety:

PVDF-based diaphragms need to improve their thermal stability and mechanical strength while maintaining high porosity and high ionic conductivity to enhance battery safety

Lack of systematic research:

There is a lack of systematic research on the effects of various factors during the electrospinning process and post-processing methods on the morphology, structure, and properties of electrospun PVDF-based diaphragms, which limits the further improvement of their properties and their application in LIBs

Summarize

Electrospun PVDF-based separators with high porosity, excellent wettability and thermal stability are expected to realize the goal of safe and high-performance LIB. This paper systematically summarizes the process and key parameter requirements for electrospun PVDF-based LIB separators. More importantly, this paper also reviews the effects of the electrospinning solution, process and post-treatment methods on the morphology, structure and properties of PVDF-based electrospun lithium-ion battery separators, covering the whole preparation process of PVDF-based electrospun lithium-ion battery separators. The research on electrospun polyvinylidene fluoride (PVDF) lithium-ion battery separators has achieved remarkable results.

In conclusion, the electrospun PVDF-based lithium-ion battery separator has a broad development space and application prospect, which will promote its further application and development in lithium-ion batteries and achieve safety and carbon neutrality.