Pore-graded and conductor- and binder-free FeS 2 films deposited by spray pyrolysis for high-performance lithium-ion bat
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Pore-graded and conductor- and binder-free FeS2 films deposited by spray pyrolysis for high-performance lithium-ion batteries Shadi Al Khateeb1,a)
Taylor D. Sparks2
1
Department of Materials Engineering, Faculty of Engineering, Al-Balqa Applied University, Al-Salt 19117, Jordan; and Department of Materials Science and Engineering, University of Utah, Salt Lake City, Utah 84112, USA 2 Department of Materials Science and Engineering, University of Utah, Salt Lake City, Utah 84112, USA a) Address all correspondence to this author. e-mail: [email protected], [email protected] Received: 25 April 2019; accepted: 30 May 2019
Porosity-graded, conductor- and binder-free porous FeS2 films through the entire thickness were deposited by spray pyrolysis. The film layers deposited at 15 versus 10 L/min are grown in different modes. The film layer deposited at 15 L/min showed Frank–van der Merwe layer-like growth mode whereas the one deposited at 10 L/min showed island growth mode. These growth modes lead to the formation of large pores on the electrolyte side and small ones on the substrate side of the film deposited using 15 and 10 L/min, sequentially. The porosity-graded films showed discharge capacities at C/10 of 879 mA h/g and 754 mA h/g for the 5th and 20th cycles, respectively. Such capacity values are superior to the literature findings for FeS2 powders and nongraded films mixed with conductor and binder additions.
Introduction Advances in materials have often been led by the development of new synthetic methods that provide control over size, morphology, and structure. The preparation of materials in a scalable and continuous manner is critical when development moves beyond lab-scale quantities. The ease and scalability for preparing materials have been a driving force for the development of new methodologies for several decades [1]. In this respect, the development of aerosol syntheses has been particularly successful [2]. Spray pyrolysis (also known as droplet deposition) is defined as the aerosol process that atomizes a solution (by a nebulizer, e.g., pneumatic, ultrasonic, or electrostatic) and heats the droplets to produce solid products [3]. Spray pyrolysis involves the deposition of evaporating droplets containing reactants onto surfaces by a carrier gas, followed by further solvent evaporation and chemical reaction on the surface [2]. It is a simple, inexpensive, nonvacuum technique and one-step process with low waste production [4], and it has a relatively high deposition rate in a nonvacuum environment and can be easily scaled up to mass production [5]. Of the various nebulizer technologies, the use of ultrasonic nebulizers has been favored because of the narrow
ª Materials Research Society 2019
distribution and the small size of the produced droplets, has the advantage of being highly scalable and continuous [6, 7], and is the one adapted in this work. Since the pioneering work by Chamberlin and Skarman in 1966 [8] on cadmium sulfide films for solar cell applications, many studies used spray pyrolysis f
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