Electrochemical Properties of Cus Cathode Material for Lithium Rechargeable Batteries Prepared By Spray Pyrolysis
Authors: Kalimuldina Gulnur , Taniguchi Izumi 
Published: February 2020

Increased demand in society for the replacement of the conventional petroleum-based energy sources by renewable energy requires development of an advanced energy storage systems. Lithium-ion batteries (LIBs) are one of the most attractive options and dominate consumer market nowadays; however, they still need to be improved significantly to fulfill the requirements of the electrical grid applications, electric vehicles (EVs) and hybrid electric vehicles(HEVs) [1].
Recently, CuS is gaining attention as a prospective transition metal cathode material due to its high theoretical capacity of 560 mAh g-1 and high electronic conductivity (10-3 S cm-1). The main hindrance of CuS is the severe capacity decay coming from the dissolution of Li2S species in the electrolyte formed during reduction reaction with Li, which cause short lifetime [2].
In our approach, we prepared CuS by one-step synthesis method of spray pyrolysis. It is known that S has theoretical specific capacity of 1675 mAh g-1 with opportunity for providing a high energy density around 2500 W h kg-1 on a weight basis assuming a complete reaction with lithium [3]. Despite these advantages, Li-S batteries suffer from several issues that impede their practical applications such as high resistance and shuttle effect triggering poor cycle life and low active mass utilization [4]. we investigated improvements of the electrochemical properties of CuS.
The precursor solution was prepared by dissolving accurate amount of copper (II) nitrate trihydrate (Cu (NO3)2·3H2O) and thiourea (CS (NH2)2) in distilled water with different Cu/S molar ratios, which was sprayed inside a laminar flow reactor using an ultrasonic nebulizer. The resulting samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (FE-SEM), auger electron spectroscopy (AES) and inductively coupled plasma-optical emission spectroscopy (ICP-OES) to study their physical properties, such as crystal structure, chemical composition, surface and interior morphologies. Furthermore, their electrochemical properties have been investigated using CR2032 coint-type cells. The cathode electrode was prepared by mixing as-prepared CuS, polyvinylidene fluoride (PVdF) and acetylene black (AB) in the 80:10:10 wt. % ratio. The coin-type cells were assembled with 1 M lithium bis(trifluoromethane sulfonamide)(LiTFSI) in 1:1 w/w in 1,3-dioxolane (DOL)/ dimethoxyethane (DME) electrolyte and lithium metal foil used as a reference electrode in an argon-filled glove box (99.9995% purity). The cell testing was performed in the voltage range between 1.0-3.0 V and 1C was used as 560 mA g-1. The as-prepared CuS sample exhibited promising results with stable capacity retention up to 100 cycles at 1C rate. The mechanism associated with the improved electrochemical performance will be discussed in the presentation.

References

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