(Invited) Low-Cobalt and Cobalt-Free Cathodes for Next-Generation Lithium-Ion Batteries

Abstract

Lithium-ion batteries have become an integral part of our daily life with an exponential growth in portable electronics during the past couple of decades. They are now being intensively developed for the electrification of the transportation sector. They also have the potential to penetrate into the utility industry for the grid storage of electricity produced from renewable sources like solar and wind. As we move from small batteries used in portable devices to large batteries used in electric vehicles and grid storage, cost becomes a major factor in addition to other factors like cycle life, safety, energy density, charge-discharge rate, and environmental impact. Lithium-ion batteries for portable devices and electric vehicles currently employ layered LiNi 1-x-y Mn x Co y O 2 cathodes with a significant amount of cobalt. Unfortunately, cobalt has limited abundance and is expensive, which could pose serious problems for a widespread deployment of lithium-ion batteries for electric vehicles and grid storage. Therefore, it is critical to develop cathodes with low-cobalt content or no-cobalt. Accordingly, the presentation will focus on the design and development of low-cobalt and cobalt-free layered oxide cathodes for next-generation lithium-ion batteries. Layered LiNi 1-x-y Mn x Co y O 2 cathodes with cobalt content as low as 6% for M in LiMO 2 or no cobalt are synthesized with a desired optimum particle size by a coprecipitation of the hydroxide precursors employing a tank reactor. The hydroxide precursors are then fired at desired temperatures with lithium hydroxide with or without appropriate dopants to obtain the layered LiMO 2 oxides. After an in-depth characterization, the oxide cathodes are evaluated by pairing with graphite anodes in full lithium-ion cells. Both the oxide cathodes and graphite anodes are characterized with a suite of analytical techniques before and after cycling the full cells for thousands of cycles to develop a fundamental understanding of the factors that lead to performance degradation. The analytical techniques include in-situ X-ray diffraction, X-ray photoelectron spectroscopy, time of flight secondary ion mass spectrometry, scanning electron microscopy, and high-resolution transmission electron microscopy. Extensive data on cathode compositions, such as LiNi 0.94 Co 0.06 O 2 and LiNiO 2 with and without doping will be presented. Furthermore, the thermal stability and air-stability of the samples and the effects of doping on them will be discussed. Stabilized cathode compositions with capacities as high as 220 mA h g -1 and long cycle life will be presented.