Journal of Power Sources 450 (2020) 227625 Available online 1 January 2020 0378-7753/© 2019 Elsevier B.V. All rights reserved. Crucial role of thioacetamide for ZrO 2 coating on the fragile surface of Ni-rich layered cathode in lithium ion batteries Van-Chuong Ho a , Seonghun Jeong a , Taeeun Yim b , Junyoung Mun a, * a Department of Energy and Chemical Engineering, Incheon National University, 12-1, Songdo-dong, Yeonsu-gu, Incheon, 22012, Republic of Korea b Department of Chemistry, Research Institute of Basic Sciences, College of Natural Science, Incheon National University, 12-1, Songdo-dong, Yeonsu-gu, Incheon, 22012, Republic of Korea HIGHLIGHTS G R A P H I C A L ABSTRACT � A homogeneous coating of Zr 2 O 3 on Ni- rich layered oxide improves performance. � A facile stirring in H 2 O with Zr(SO 4 ) 2 and thioacetamide is developed for coating. � Thioacetamide helps to deliver a ho- mogeneous ZrO 2 coating. � Thioacetamide supports to preserve the fragile surface of Ni-rich layered oxide. A R T I C L E INFO Keywords: Thioacetamide Ni-rich layered cathode ZrO 2 coating Homogeneous coating pH condition for coating ABSTRACT Thioacetamide (TA) is essentially introduced to form a ZrO 2 -coating in a facile method via washing with a Zr (SO 4 ) 2 aqueous solution. This method is specially applied for a Ni-rich layered oxide LiNi 0.82 Co 0.09 Mn 0.09 O 2 (NCM82), the surface of which is chemically fragile due to unstable Ni 3þ ions. Under acidic conditions due to sulfate anions, TA plays a pivotal role in preserving the fragile surface of the Ni-rich layered oxide and leads to a homogeneous coating. With the TA-supported ZrO 2 coated sample, the cyclability reaches 89.4% showing a high capacity of 174.0 mAh g 1 at 0.3 C after 100 cycles, whereas the conventional ZrO 2 -coated sample without TA, which is generally known to be excellent for other positive electrode materials, is a low value of 64.2% with 125.7 mAh g 1 under the same condition. The TA-supported ZrO 2 -coated layer is notably homogeneous and has a thickness of approximately 5.75 nm. In addition, the TA-supported ZrO 2 -coated cathode material also displays a greatly enhanced rate capability of 116.8 mAh g 1 under a current density of 3.0 C. The structure of the ZrO 2 - coated cathode particle prevents unfavorable side reactions on the surface, and therefore, no micro-cracking into the grain boundary occurs after charging/discharging. The titration method demonstrates the removal of a large amount of lithium impurities from the surface of the active material. 1. Introduction To address the concerns of global warming and environmental threats, rechargeable batteries with a high energy density are required for highly effcient energy circulation systems, including electric vehi- cles and energy storage systems [1–3]. To this end, the lithium ion * Corresponding author. E-mail address: jymun@inu.ac.kr (J. Mun). Contents lists available at ScienceDirect Journal of Power Sources journal homepage: www.elsevier.com/locate/jpowsour https://doi.org/10.1016/j.jpowsour.2019.227625 Received 25 September 2019; Received in revised form 5 December 2019; Accepted 15 December 2019