Abstract
Surface coating modification on a polyethylene separator serves as a promising way to meet the high requirements of thermal dimensional stability and excellent electrolyte wettability for lithium ion batteries (LIBs). In this paper, we report a new type of surface modified separator by coating polyvinylidene fluoride (PVDF) organic particles on traditional microporous polyethylene (PE) separators. The PE separator coated by PVDF particles (PE-PVDF separator) has higher porosity (61.4%), better electrolyte wettability (the contact angle to water was 3.28° ± 0.21°) and superior ionic conductivity (1.53 mS/cm) compared with the bare PE separator (51.2%, 111.3° ± 0.12°, 0.55 mS/cm). On one hand, the PVDF organic polymer has excellent organic electrolyte compatibility. On the other hand, the PVDF particles contain sub-micro spheres, of which the separator can possess a large specific surface area to absorb additional electrolyte. As a result, LIBs assembled using the PE-PVDF separator showed better electrochemical performances. For example, the button cell using a PE-PVDF as the separator had a higher capacity retention rate (70.01% capacity retention after 200 cycles at 0.5 C) than the bare PE separator (62.5% capacity retention after 200 cycles at 0.5 C). Moreover, the rate capability of LIBs was greatly improved as well—especially at larger current densities such as 2 C and 5 C.
Highlights
Lithium ion batteries (LIBs), which possess several advantages such as high specific energy, low self-discharge, good cycling performance, no memory effect and green environmental protection, are becoming very promising efficient secondary batteries and the fastest developing chemical energy storage power supply [1,2]
The porosity of the bare PE separator and the PE-polyvinylidene fluoride (PVDF) separator were investigated by measuring the weight change of an original separator and one after full saturation in n-hexadecane for 6 h, and calculated with
SEM was used to evaluate the morphologies of the bare PE and PE-PVDF separators, as shown in Materials 2019, 12, x FOR PEER REVIEW
Summary
Lithium ion batteries (LIBs), which possess several advantages such as high specific energy, low self-discharge, good cycling performance, no memory effect and green environmental protection, are becoming very promising efficient secondary batteries and the fastest developing chemical energy storage power supply [1,2]. As an important polymer material for LIBs, PVDF is often used as the binder for anode and cathode preparations It is becoming a good organic coating choice for traditional polyolefin separators as well due to its special functional group structure [16]. Researched a porous PVDF separator prepared by electrospinning Their results showed that PVDF separators had high porosity and ionic conductivity; when the average fiber diameter was 0.45 to. PVDF particles improve organic compatibility between the organic PVDF polymer and the electrolyte, but possess a larger specific surface area to retain additional electrolyte as well It can significantly improve electrolyte retention of the separator and the lithium ionic conductivity, which helps to improve electrochemical performances-especially the capacity retention and C rate capacity
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
