Paving New Road to Next-Generation 3D Electrode Synthesis Technology
Professor Choi Won-joon’s group developed a technology for synthesizing binder-free Li-ion battery anode.
The proposed design strategy for transition metal oxide multi-optimization was published in ACS Nano, a renowned international journal.

▲ Professor Choi Won-joon (left, corresponding author) and M.S. student Kim Woo-sung in the School of Mechanical Engineering.

Professor Choi Won-joon’s group in the School of Mechanical Engineering (first author: M.S. student Kim Woo-sung) developed a technology for synthesizing a transition metal oxide-based binder-free anode. Electrothermal waves were used to synthesize cobalt oxide-based nanoarrays on a nickel current collector in the form of 3D foams within several seconds. The electrode had a high grain boundary density and few oxygen vacancies, exhibiting an excellent high-rate capacity at a high current density. Furthermore, the research group investigated the mechanism behind the performance of the battery by varying the physicochemical structure of the electrode through an electrothermal process, and proposed a novel transition metal oxide design strategy for high-capacity lithium secondary batteries based on the mechanism.

* Article Title : Precisely Tunable Synthesis of Binder-Free Cobalt Oxide-Based Li-Ion Battery Anode Using Scalable Electrothermal Waves
* Authors : Woosung Kim, Dongjoon Shin, Byungseok Seo, Seunghoon Chae, Eunmi Jo, and Wonjoon Choi
* DOI : 10.1021/acsnano.2c08115


The results of the study were published online in ACS Nano (IF=18.027), an internationally renowned journal, on September 21.

Recently, a binder-free electrode, fabricated using only an active material in the electrode, has emerged as a new type of next-generation anode for lithium secondary batteries. Transition metal oxides, with their high theoretical capacity, are used as the active material, but more research on improving their properties is required due to their low electric conductivity and drastic volumetric expansion during charge-discharge cycles. However, in a binder-free electrode, in which an active material and a current collector are physically in contact with each other, it is very difficult to independently control the physicochemical properties of only the active material through the existing synthesis processes.

▲ Strategy for synthesizing and designing cobalt oxide-based binder-free anode by using an electrothermal process.

Therefore, Professor Choi’s group employed an electrothermal process, instead of the conventional processes, to synthesize cobalt-oxide-based nickel foam electrodes, and successfully controlled both the structural and chemical properties of the cobalt oxides. In an electrothermal process, a current is applied to both ends of a conductive substrate to induce a temperature rise through internal resistance, and this enables one to synthesize a material within just a few seconds. Significantly, the process can be used to achieve various structural differences by varying the power and durations of the applied current, allowing for multi-optimization of the target materials. The research group confirmed through various analytical methods that the cobalt oxides synthesized by the electrothermal process have a higher grain boundary density and much fewer oxygen vacancies, than the cobalt oxides synthesized by the conventional annealing process.

In addition, the research group observed how the properties of the cobalt oxides varied depending on the cycles of the electrothermal process, and found that a reduction reaction and particle agglomeration of the cobalt oxides are caused by the energy remaining after the applied energy is consumed by heat transfer and as internal energy. In addition, the research group found that the same amount of oxygen vacancies was retained, even after the electrothermal process was repeated, showing that the structural properties and chemical properties of a transition metal oxide can be independently controlled through the electrothermal process. Furthermore, the research group observed the effects of the properties of the active material on battery performance. The results showed not only that capacity can be significantly improved by increasing the grain boundary density, but also that longer battery lifetimes can be secured by maintaining the oxygen vacancies at an optimal level to prevent the irregular volumetric expansion of the cobalt oxides during charge-discharge cycles.

Professor Choi’s group simultaneously optimized the structural and chemical properties of the transition metal oxide-based binder-free anode by means of the electrothermal process, and demonstrated the excellent battery performance of the electrode, showing that the electrode may be used in actual target applications. The research group expect that their electrothermal process-based synthesis and design strategy can be used to investigate battery mechanisms and perform the multi-optimization of high-performance electrodes, helping to overcome the limitations of anode performance.