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Novel Method for Synthesis of High Nickel Cobalt Aluminum Hydroxide By Engineered Two Step Co-Precipitation Method
Kitae Kim, Minah Cha, Jangsuk Hyun, Tae-Hwan Yu, Wooyoung Yang, Jeong-Ju Cho
Battery Materials R&D Team, Samsung Fine Chemicals, Suwon, Gyeonggi-do 443-803, S.Korea
Abstract
NCA is a promising cathode material for high energy lithium ion battery in electric vehicles and hybrid electric vehicles because of high power. It overcomes imperfections such as cycle life, rate capability, and low thermal stability with higher specific capacity compared to Ni-rich cathode materials.1-3 For NCA preparation, there are various methods, but specifically, solid-state reaction of metal oxide and liquid phase synthesis of metal salts using continuous stirred tank reactor have been used. 4-6 However, the former method is not suitable for commercialization due to homogeneous mixture problems and economic issue. Furthermore, although using the overflow continuous reactor is a good method to control particle growth and to get spherical particles,7 it has broad particle distribution. Also, it is hard to synthesize the NCA hydroxide with desired target size and high tap density which would affect volumetric capacity because the addition of Al precursors during the precipitation of transition metal may have an effect on the chemical condition for nucleation and growth of formation of NCA(OH)2 precursors, especially pH and concentration of solution during synthesis.7
In this study, the coprecipitation method using engineered reactor was used in order to overcome the problems of non-uniform dispersal of Al in transition metal and broad size distribution of products. The method for making NCA hydroxide with desired size and tap density was demonstrated as shown in fig 1. NCA hydroxide, which is NC hydroxide with Al affixed on the surface, synthesized by this method has high tap density (over 2.0g/cc). The control of supersaturation during nucleation and crystal growth of Al on the NC hydroxide allows control of Al formation with a few hundred nanometers. This method also allows control for various sizes homogeneously. Through the calcination process with atmosphere control, the Al was well diffused and distributed to the core of the final product, LNCAO2 cathode material. The NCA cathode material has good cycle characteristics because Al, which acts as a ‘pillar’ in the interslab space, can suppress the crystallographic phase and decrease the irreversible capacity4. And it has been investigated by atomic scale probe. The revolutionary method described here is also being used to incorporate other various metal ion sources into transition metal ions to improve electrochemical performance and safety characteristics of high nickel containing cathode materials. Furthermore, this method is useful for triple layer and core-shell cathode material application.
References
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7. Yoon et al., Electrochem. Solid-State Let., 12, A211 (2009).