In this study, we have prepared Sn-added SiOx using a mechanical milling method and investigated the effect of Sn addition on the anode properties of SiOx for lithium-ion batteries.
A charge–discharge cycle test with a charge limit of 1000 mAh g−1 shows that the SiOx electrode causes a capacity fading loss by 170 cycles. Conversely, it is confirmed that the SiOx electrodes with the addition of 1 or 3 wt% of Sn maintain a discharge capacity of up to 250 or 360 cycles, respectively, and the charge–discharge cycle life is extended depending on the amount added. Furthermore, the test is conducted by reducing the lithium-insertion amount from 1000 to 750 mAh g−1 to observe the effect of Sn addition. Resultantly, the difference in cycle life is more pronounced, and the discharge capacity of the 3 wt% Sn-added SiOx is maintained for up to 540 cycles. When the amount of Sn added is as small as 1 wt%, the lithium insertion reaction is locally concentrated because of insufficient electronic conductivity, and Li3.75Si, with a large volume change, is formed. Resultantly, this electrode causes the disintegration of the electrode and a decrease in capacity. However, in the SiOx electrode with 3 wt% of Sn, the reactivity of the lithium ions in the SiO2 matrix is enhanced by the improvement in the electronic conductivity. Thus, the entire active material layer reacts easily and uniformly with the lithium ions. Resultantly, the structure is such that the stress of Si is less likely to concentrate, the damage to the electrodes is reduced, and the electrode disintegration can be suppressed, which is the reason for the enhanced cycle life.
For polymer electrolyte fuel cell cathodes, highly durable supports are required to prevent catalyst degradation in supports. In this study, as model Pt catalysts, 2–10 wt% Pt was deposited on Magnéli-phase niobium-doped macroporous Ti4O7 (Nb–Ti4O7) mounted on glassy carbon rods using the coaxial arc plasma deposition method. The morphologies of 2, 5, and 10 wt% Pt catalysts showed the hemisphere fine particles, islands with ca. 1.4 nm diameter and ca. 2.4 nm thickness, and films with ca. 3.3 nm thickness, respectively. During start/stop accelerated durability tests (ADTs) of 5000 cycles following the Fuel Cell Commercialization Conference of Japan protocol, Pt was slightly agglomerated; consequently, the morphologies of the 2, 5, and 10 wt% Pt catalysts were island-like with 3.5 nm thickness, chain bead-like with 4 nm thickness, and film-like with 4 nm thickness, respectively. This slight agglomeration led to good durability during the ADTs. Herein, the oxygen reduction reaction (ORR) mass activity (MA) values at 0.9 V vs. reversible hydrogen electrode (RHE) of the 2, 5, and 10 wt% Pt catalysts were 79, 60, and after 5000 cycles ADT, respectively, which had declining ratios after 5000 cycles were 32 %, 17 %, and 0 %, respectively. The island-like and film-like Pt/Nb–Ti4O7 presented activity and durability comparable to a Pt/C catalyst, which was (0.9 V vs. RHE) with a 12 % of declining ratio after the ADTs. The durability of the MA suggested that the different affinity caused by different crystal faces led to the slight agglomeration of 2, 5, and 10 wt%_Pt/Nb–Ti4O7 catalysts. These catalysts showed electrochemical surface areas (ECSAs) of 36, 27, and 29 m2 g−1 after the ADTs, with declining ratios as low as 20 %, 6 %, and 0 %, respectively. All Pt/Nb–Ti4O7 catalysts showed higher durability of the ECSAs than the Pt/C catalyst, which was 68 m2 g−1 with a 30 % declining ratio after the ADT. Different from common Pt nanoparticle catalysts, which agglomerate into large spherical Pt particles, the slight agglomeration was caused by the interconnection of the deposits and supplemented by a limited increase in the diameter or thickness. The island-like morphology of Pt with a limited thickness presented both high durability and activity among the Pt/Oxide catalysts.
The anodic dissolution (electropolishing) of pure metallic nickel and cobalt in choline chloride-propylene glycol eutectic mixture at a mole ratio of 1 : 3 by holding the voltage at 0.9 V for 40 min at 25 °C. The electrochemical study was further studied by recording a steady-state in the form of I-t profile for both metals. Mass transport is the cause of electropolishing and has been proved from the obtained steady-state. The process of electropolishing makes the metallic surface to be resistive to degradation by corrosion. For characterization of the prepared electropolished surface, two microscopic techniques were used; namely, scanning electron and atomic force microscopies. The SEM images have exhibited relatively high-quality electropolished surfaces in both cases of the surface. The Ra from the AFM are 198.8 and 132.6 nm for polished surfaces of nickel and cobalt, respectively and Ra are 200.1 and 102.2 nm for unpolished regions of nickel and cobalt, respectively.