Macroporous Catalytic Carbon Nanotemplates for Sodium Metal Anodes

Abstract

Lithium and sodium metal have recently have been proposed as alternative negative electrode materials because of their low redox potentials (−3.04 and −2.71 V vs the standard hydrogen electrode, respectively) and high theoretical capacities (3860 and 1166 mA h g −1 , respectively) which are 10 and 3 times higher, respectively, than that (372 mA h g −1 ) of a graphite anode in a typical Li ion battery. [15,16] Nevertheless, these metal anodes have fatal problems such as low Coulombic efficiencies, infinite volume changes, and unpredictable metal electrodeposition (dendritic growth), which lead to capacity decay, cycling limitations, and safety hazards caused by the repeated electrochemical dissolution and deposition of metal. [17][18][19][20][21][22][23] To address these issues, several efforts have been made to introduce additives into electrolytes, [24][25][26][27][28][29][30] carbon-based templates, [31][32][33][34][35][36] or protective coating layers. [37][38][39][40] In particular, Zheng et al. reported a sophisticated electrode design with an interconnected hollow carbon nanosphere cover layer that allows a uniform Li ion flux at the electrode level, which leads to stability over 150 cycles. [34] Zhang et al. proposed a unique channel structure to provide a pathway that guides the Li deposition/dissolution process. It effectively mitigates electrode volume changes and alleviates the dendritic growth of Li metal. [35] In addition, a glyme-based electrolyte can suppress dendritic growth while improving the Coulombic efficiency without use of an additive or additional Na metal anode processing. [41][42][43][44] These results suggest that introducing a carbon-based catalytic template and glymebased electrolyte can alleviate the major shortcomings of metal anodes. Furthermore, nanostructured design of the template structure may provide significantly more active sites for metal deposition and dissolution. This can induce a uniform Na ion flux throughout the electrode, leading to high rate capabilities and stable cycling via obstruction of dendritic metal growth at high charge/discharge rates.In this study, we designed macroporous catalytic carbon nanotemplates (MC-CNTs) composed of hierarchically interconnected carbon nanofibers with various local microstructures synthesized from microbe-derived cellulose via simple heating at temperatures from 800 to 2400 °C. Carbon-based MC-CNT monoliths 1/2 in. in diameter were used as anode materials without metal substrates and binders. MC-CNT-800 and Because of its remarkably high theoretical capacity and favorable redox voltage (−2.71 V vs the standard hydrogen electrode), Na is a promising anode material for Na ion batteries. In this study, macroporous catalytic carbon nanotemplates (MC-CNTs) based on nanoweb-structured carbon nanofibers with various carbon microstructures are prepared from microbederived cellulose via simple heating at 800 or 2400 °C. MC-CNTs prepared at 800 °C have amorphous carbon structures with numerous topological defects, and exhibit a lower voltag...

Hierarchically Macroporous Graphitic Nanowebs Exhibiting Ultra-fast and Stable Charge Storage Performance

“…In our previous studies, it was found that BC pellicles can be carbonized by simple heating with maintaining its intrinsic pore structure [14,16,17]. And the carbonized BC pellicles were graphitized with further high-temperature heating by 2400°C [17]. Moreover, the carbonized/graphitized BC pellicles were free-standing, which can be used as an electrode material for energy storage without binder and substrate [14,17].…”

“…BC has a unique pore structure and properties compared to other types of cellulose in terms of its purity, high crystallinity, and high mechanical strength [15]. In our previous studies, it was found that BC pellicles can be carbonized by simple heating with maintaining its intrinsic pore structure [14,16,17]. And the carbonized BC pellicles were graphitized with further high-temperature heating by 2400°C [17].…”

“…And the carbonized BC pellicles were graphitized with further high-temperature heating by 2400°C [17]. Moreover, the carbonized/graphitized BC pellicles were free-standing, which can be used as an electrode material for energy storage without binder and substrate [14,17]. These material properties of BC could be fitted as an electrode for high-power supercapacitors.…”

Anode‐Free Sodium Metal Batteries Based on Nanohybrid Core–Shell Templates

“…Considering the price issue, sodium metal batteries (SMBs) based on abundant and ubiquitous sodium resources appear to be more suitable. Despite the apparent suitability, SMBs suffer from technological barriers similar to LMBs, which are induced by dendritic metal growth and mossy metal deposits . Therefore, several studies have been conducted to find a means to control undesirable metal growth .…”

“…In addition, it was confirmed that an ether‐based electrolyte system and/or additives can induce dendrite‐free cycling . Under an ether‐based electrolyte, the lithiophilic/sodiophilic sites of carbon‐based catalytic material (CCM) guide homogeneous metal nucleation, resulting in improved cycling performance . More functionalized CCMs, including a large number of catalytic sites, exhibited more efficient metal deposition/striping behaviors, leading to feasible electrochemical performance corresponding to a CE value of ≈99.9%.…”