Research Center. His current research is focused mainly on Li-ion (electrode materials with high capacity and high structural stability) and metal air batteries and redox fl ow batteries for energy storage.

This work has been performed to determine the critical size of the GeO2 nanoparticle for lithium battery anode applications and identify its quantum confinement and its related effects on the electrochemical performance. GeO2 nanoparticles with different sizes of ∼ 2, ∼ 6, ∼ 10, and ∼ 35 nm were prepared by adjusting the reaction rate, controlling the reaction temperature and reactant concentration, and using different solvents. Among the different sizes of the GeO2 nanoparticles, the ∼ 6 nm sized GeO2 showed the best electrochemical performance. Unexpectedly smaller particles of the ∼ 2 nm sized GeO2 showed the inferior electrochemical performances compared to those of the ∼ 6 nm sized one. This was due to the low electrical conductivity of the ∼ 2 nm sized GeO2 caused by its quantum confinement effect, which is also related to the increase in the charge transfer resistance. Those characteristics of the smaller nanoparticles led to poor electrochemical performances, and their relationships were discussed.

Porous strategies based on nanoengineering successfully mitigate several problems related to volume expansion of alloying anodes. However, practical application of porous alloying anodes is challenging because of limitations such as calendering incompatibility, low mass loading, and excessive usage of nonactive materials, all of which cause a lower volumetric energy density in comparison with conventional graphite anodes. In particular, during calendering, porous structures in alloying‐based composites easily collapse under high pressure, attenuating the porous characteristics. Herein, this work proposes a calendering‐compatible macroporous architecture for a Si–graphite anode to maximize the volumetric energy density. The anode is composed of an elastic outermost carbon covering, a nonfilling porous structure, and a graphite core. Owing to the lubricative properties of the elastic carbon covering, the macroporous structure coated by the brittle Si nanolayer can withstand high pressure and maintain its porous architecture during electrode calendering. Scalable methods using mechanical agitation and chemical vapor deposition are adopted. The as‐prepared composite exhibits excellent electrochemical stability of >3.6 mAh cm−2, with mitigated electrode expansion. Furthermore, full‐cell evaluation shows that the composite achieves higher energy density (932 Wh L−1) and higher specific energy (333 Wh kg−1) with stable cycling than has been reported in previous studies.

Despite the advantage of high capacity, the practical use of the silicon anode is still hindered by large volume expansion during the severe pulverization lithiation process, which results in electrical contact loss and rapid capacity fading. Here, a combined electrochemical and computational study on the factor for accommodating volume expansion of silicon-based anodes is shown. 1D silicon-based nanostructures with different internal spaces to explore the effect of spatial ratio of voids and their distribution degree inside the fibers on structural stability are designed. Notably, lotus-root-type silicon nanowires with locally distributed void spaces can improve capacity retention and structural integrity with minimum silicon pulverization during lithium insertion and extraction. The findings of this study indicate that the distribution of buffer spaces, electrochemical surface area, as well as Li diffusion property significantly influence cycle performance and rate capability of the battery, which can be extended to other silicon-based anodes to overcome large volume expansion.

Practical applications of high gravimetric and volumetric capacity anodes for next-generation lithium-ion batteries have attracted unprecedented attentions, but still faced challenges by their severe volume changes, rendering low Coulombic efficiency and fast capacity fading. Nano and void-engineering strategies had been extensively applied to overcome the large volume fluctuations causing the continuous irreversible reactions upon cycling, but they showed intrinsic limit in fabrication of practical electrode condition. Achieving high electrode density is particularly paramount factor in terms of the commercial feasibility, which is mainly dominated by the true density and tapping density of active material. Herein, based on finite element method calculation, micron-sized double passivation layered Si/C design is introduced with restrictive lithiation state, which can withstand the induced stress from Li insertion upon repeated cycling. Such design takes advantage in structural integrity during long-term cycling even at high gravimetric capacity (1400 mAh g −1). In 1 Ah pouch-type full-cell evaluation with high mass loading and electrode density (≈3.75 mAh cm −2 and ≈1.65 g cm −3), it demonstrates superior cycle stability without rapid capacity drop during 800 cycles.