# Electochemically Engineered Mesoporous Sn-Oxide Rods for Anode Materials in Lithium-Ion Batteries
## 4 Conclusions  
In this study, core-shell structures consisting of a Sn rod core and a mesoporous Sn-oxide shell were fabricated using a facile electrochemical method and evaluated as anode materials for lithium-ion batteries (LIBs). Comprehensive results highlighted the influence of processing parameters on the resulting morphology and electrochemical performance of these materials. The experimental findings are summarized as follows:  
1. Dendritic Sn, composed of primary and secondary rods, was successfully fabricated via single electrodeposition. Under constant-current conditions, the diameter of the secondary Sn rods increased linearly with rising current density, but at current densities above 4 A/cm\({}^{2}\) and a deposition time of 10 s, agglomeration between the secondary rods was observed. In contrast, under constant-voltage conditions, highly uniform secondary rods were formed without agglomeration, even when a larger amount of Sn was deposited than under constant-current conditions, where the aggregated structure appeared.
2. The Sn micro rods were anodized to form core-shell structures, where the surface of the Sn rods was covered with mesoporous Sn-oxide. A uniformly distributed porous Sn-oxide layer was successfully formed across the entire surface at anodization above 6 V. As the anodization voltage increased, the pore size increased, while pore wall thickness decreased.
3. The core-shell anodes were evaluated for LIB application. During the first cathodic scan (lithiation) of the cyclic voltammetry experiment, Li\({}_{2}\)O formation was observed at approximately 0.5-0.8 V vs. Li\({}^{+}\)/Li. This Li\({}_{2}\)O was partially decomposed in the subsequent anodic scan, contributing to the reversible capacity. At higher anodization voltages, the Li\({}_{2}\)O-related signal became more pronounced, indicating an increased Li\({}_{2}\)O contribution to the reversible capacity.  
Figure 11: Surface morphology of the anodes: Sn rod anode (**a**) before and (**b**) after cycling. Core-shell anode anodized at 10 V (**c**) before and (**d**) after cycling. The inset figures in (**c,d**) are magnified images.  
The initial charge-discharge tests of the core-shell anodes exhibited specific capacities comparable to or exceeding that of the Sn rod anode. Higher anodization voltages resulted in higher specific capacities. The core-shell anodes also demonstrated slower capacity fade than the Sn rod anode, with higher discharge capacity retention at increased anodization voltage. Despite these promising results, significant initial irreversible capacity loss and cycle degradation remain challenges that must be addressed for commercial viability.  
Data curation, [PERSON]-J.L. and [PERSON]-[PERSON]; formal analysis, W.-J.L.; funding acquisition, H.-C.S.; investigation, W.-J.L. and [PERSON]-[PERSON]; methodology, W.-J.L.; supervision, H.-[PERSON]; validation, W.-J.L., [PERSON] and [PERSON]-[PERSON]; writing--original draft, W.-J.L.; writing--review & editing, H.-C.S. All authors have read and agreed to the published version of the manuscript.  
This work was supported by the National Research Foundation of the Ministry of Science and ICT (RS-2025-00512708) and by the Korea Institute of Energy Technology Evaluation and Planning (KETEP) and the MOTIE of the Republic of Korea (No. 20224000000400).  
Not applicable.  
The data that support the findings of this study are available from the corresponding author upon request.  
The authors declare no conflicts of interest.