The Effects of Combustion Fuels (Urea and Ethylene Glycol) on the Electrochemical Performance of LMNCA
Authors: Nkosi Funeka Phumzile , Palaniyandy Nithyadharseni , Raju Kumar , Billing Caren , Ozoemena Kenneth I. 
Published: February 2020

The commercialization of rechargeable lithium-ion batteries in 1991 by Sony Corporation revolutionized the portable electronics industry [1]. Lithium-ion batteries are used in a variety of electronic devices such as cell phones, laptops, and cameras. Recently, lithium-ion batteries have also revolutionized the automobile industry; they are found in electric vehicles such as the Tesla and Nissan Leaf. However, the commercially available cathode materials such as LiCoO2 (LCO) limit their application in electric vehicles. This is because LCO is expensive, toxic and has a low practical capacity (130-140 mAh/g) and poor thermal stability. Intensive efforts have been made in the development of lithium-manganese rich nickel, manganese, cobalt oxide (LMR-NMC) as alternative cathode materials for electric vehicles due to their high voltage and reversible capacity of >200 mAh/g compared to the commercial LCO cathode material [2].

LMR-NMC cathode materials are based on the composite ‘layered-layered’ xLi2MnO3 ·(1-x)LiMO2 (M=Mn, Co, Ni) or Li1+yM1-yO2 (M =Co, Mn, Ni) structure which is an integration of layered LiMO2 (M= Co, Mn, Ni) with a hexagonal unit cell of R-3
m space group and layered Li2MnO3 with a monoclinic unit cell of C2/m space group [1-3]. However, these types of materials are plagued by a series of problems that limit their commercialization. When the LMR-NMC is charged to high potentials (> 4.4 V vs Li), the Li2MnO3 component is activated by the simultaneous removal of lithium and oxygen from the structure. This activation leads to high first-cycle irreversible capacity and voltage fade [4,5]. Additionally, these materials exhibit a low rate capability and capacity fade [6,7]. These problems are closely related to the structure, stoichiometry, and morphology which are greatly influenced by the synthesis methods and conditions [8,9]. Therefore, there is a need for continued investigation of synthesis methods to be able to overcome the hurdles associated with this material.

In this work, Li1.2Mn0.52Co0.13Ni0.13Al0.02O2 (LMNCA) cathode was successfully prepared using combustion method with urea and ethylene glycol (EG) as fuels. The effect of the fuel on the physical (FE-SEM, BET), structural (PXRD) and electrochemical (CV, GC, and EIS) properties of the samples were evaluated. The results revealed that the LMNCA from urea (LMNCA-urea) sample exhibits a highly ordered crystalline ‘layered-layered’ structure, narrow particle size distribution and high surface area compared to LMNCA from EG (LMNCA-EG). The LMNCA-urea resulted in enhanced capacity, cycle performance, and rate capability. This presentation will discuss in detail the different physical and electrochemical properties of the LMNCA due to the use of urea and EG as combustion fuels.

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