Abstract
This paper considered the electrochemical behavior of new electrospun separators for lithium-ion batteries on the basis of nano- and microfibers of polyvinylidene fluoride (PVDF) and its polymer composition, with polytetrafluoroethylene (PTFE) having advanced electroconductive properties over conventionally used separators based on polypropylene (PP) and glass-fibers (GF). Such advancement is associated with the low density of electrospun material leading to lower mechanical strengths. However, its use in the electrochemical systems with middle-voltage anode materials where dendrite growth is excluded is very prospective. The performance at the operation of the separators were investigated in the three-electrode-containing laboratory half-cells having Li4Ti5O12 as the electrode under investigation. Galvanostatic charge and discharge tests of cells were conducted under variation of the experimental conditions: the current varied in the range 0.1 C–1 C, and 1C cycling was conducted over 100 cycles. The working electrode and separator characteristics at cycling were monitored by the electrochemical impedance spectroscopy (EIS) method. The gradual decrease of Li4Ti5O12 transport characteristics at cycling was noticed for all the types of separators. However, the least degradation rate was associated with the PVDF and the PTFE-based separator. This fact is explained by the better conductivity of an electrospun separator compared to others, with therefore a better current distribution on the electrode surface and a lower concentration perturbation in the electrode.
Highlights
Lithium-ion batteries are widely used to power portable electronic devices, aerospace systems and more recently, electric vehicles and stationary energy storage systems, due to their high specific energy and power, their significant working resource and wide range of operating conditions
Some structural features of the electrospun polyvinylidene fluoride (PVDF)|PTFE and the conventional PP-based separators were thoroughly considered in our previous work [7]
The glass fiber-based separator that we studied had a rather large thickness of 112 μm and a surface density of 35–40 g·m−2 and at the same time, a low strength in comparison with the separators based on PVDF|PTFE and PP
Summary
Lithium-ion batteries are widely used to power portable electronic devices, aerospace systems and more recently, electric vehicles and stationary energy storage systems, due to their high specific energy and power, their significant working resource and wide range of operating conditions. The main components of a lithium-ion battery are the active materials of electrodes, electrolyte and the separator. Significant efforts have been applied to improve separators: the goals are to reduce the thickness of the separator, to increase the wettability of the electrolyte solutions, to increase the mechanical strength and to provide a programmable behavior of the separator in the emergency operation of the battery, for example, blocking ion exchange at rapid heating. One of the significant characteristics of lithium-ion batteries is their ability for long-term cycling whilst maintaining a stable capacity and a shape of charge–discharge. The improved cycling behavior of a LiMn2 O4 -electrode [1] in a half-cell with a metal Li counter electrode and a 1M
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