Improved electrochemical properties of LiNi 0.8 Co 0.15 Al 0.05 O 2 cathode materials synthesized using micelle structur
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ORIGINAL PAPER
Improved electrochemical properties of LiNi0.8Co0.15Al0.05O2 cathode materials synthesized using micelle structures Sang-Hyun Moon 1 & Eun-Soo Kim 1 & Ji-Eun Lee 1 & Yeon-Kyung Shin 1 & Min-Cheol Kim 1 & Kyung-Won Park 1 Received: 10 September 2019 / Revised: 13 April 2020 / Accepted: 27 May 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Although LiNi0.8Co0.15Al0.05O2 (NCA) has various merits such as a high discharge capacity of ~ 195 mAh gā1, improved stability, and low cost, intergranular cracks in the NCA structure can suppress the electronic/ionic motion in the cathode. Thus, in this study, to minimize crack portions in the NCA cathode, we synthesized dense NCA cathode materials using micelle structures controlled with pluronic acid (F127) and polyvinyl alcohol (PVA) as polymer templates and evaluated the electrochemical performance in LIBs using coin-type cells. We found that all the as-prepared samples showed the LiNiO2-based structures doped with Co and Al. With an increasing amount of PVA, the 1st particles can be more agglomerated during heating and thus increase the size of the 2nd particles. Consequently, a significantly dense NCA structure consisting of less cracked 2nd particles can be prepared in the presence of F127 and PVA. In particular, the NCA cathode prepared with an optimal ratio of F127 to PVA exhibited the best electrochemical properties, i.e., high capacity and superior cycle life. Keywords LiNi0.8Co0.15Al0.05O2 . Micelle structure . Cathode . Li-ion batteries
Introduction Lithium-ion batteries (LIBs) are electrochemical power sources, with high energy densities and excellent cycling properties, that can store electrical energy using electrochemical reactions of lithium ions at the cathode and anode [1ā4]. In particular, cathode materials (LiCoO2 , LiNiO 2 , and LiMn2O4) consisting of 3d transition metals (Co, Ni, and Mn) exhibit high electrochemical potentials with respect to Li + /Li and electrochemical reduction reactions during discharging [5ā9]. The required characteristics of cathode materials for LIBs are high specific/volumetric capacity, high electronic/ionic conductivity, stability, and safety. Especially, high volumetric capacity and improved cycling efficiency in active materials can result from a lightweight Sang-Hyun Moon and Eun-Soo Kim contributed equally to this work. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10008-020-04680-5) contains supplementary material, which is available to authorized users. * Kyung-Won Park [email protected] 1
Department of Chemical Engineering, Soongsil University, Seoul 06987, Republic of Korea
dense electrode structure and minimizing irreversible phase transition, respectively. Among these cathode materials, LiNiO2 has a higher actual capacity than that of LiCoO2 as a representative cathode. However, an exchange of a lithium ion site with Ni2+ can induce a link between NiO 2 layers and form a threedimensional structure, interfering the diffusion of
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