Synergistic Manipulation of Na⁺ Flux and Surface‐Preferred Effect Enabling High‐Areal‐Capacity and Dendrite‐Free Sodium Metal Battery

Abstract

The propensity of sodium anode to form uniform electrodeposit is bound up with the nature of electrode surface and regulation of Na-ion flux, as well as distribution of electronic field, which is quite crucial for high-areal-capacity sodium metal batteries (SMBs). Herein, a novel metallic sodium/sodium-tin alloy foil anode (Na/NaSn) with 3D interpenetrated network and porous structure is prepared through facile alloy reaction. The strong sodiophilic properties of sodium-tin alloy can lower the nucleation energy, resulting in smaller depositing potential and strong adsorption of Na + , while synergistic effect of porous skeleton and additional potential difference (≈0.1 V) between Na and Na-Sn alloy (Na 15 Sn 4 ) can alleviate volume expansion, redistribute the Na-ion flux and regulate electronic field, which favors and improves homogeneous Na deposition. The as-fabricated Na/NaSn electrode can endow excellent plating/stripping reversibility at high areal capacity (over 1600 h for 4 mAh cm −2 at 1 mA cm −2 and 2 mAh cm −2 at 2 mA cm −2 ), fast electrochemical kinetics (500 h under 4 mAh cm −2 at 4 mA cm −2 ) and superior rate performances. A novel strategy in the design of high-performance Na anodes for large-scale energy storage is provided.

Toward High Temperature Sodium Metal Batteries via Regulating the Electrolyte/Electrode Interfacial Chemistries

“…Here, the (100) crystal planes of both electrodes were chosen for their predominant exposure to the electrolyte due to low surface energy. 34,35 At the potential of zero charge (PZC), where no surface charge density was applied (0 μC/cm 2 ), the electrolyte composition near the electrode surfaces roughly resembles that in the bulk. However, one prominent observation is that the relative density of HTCN molecules experienced an obvious spike at near 3 Å to the NVPOF (100) surface, indicative of their accumulation at the NVPOF surface.…”

“…Since the study on the Na + solvation structure from the bulk electrolyte fails to probe the electrolyte/electrode interfacial structures (Figure S18), we here refer to the electric double layer (EDL) structure on the electrode surfaces, whose existence, though in nanometer thickness, largely influences the SEI/CEI formation process with enrichment or depletion of certain species. , With the initial model system shown in Figure S19 (see the Supporting Information for simulation methods and details), we were able to investigate the interfacial electrolyte component by analyzing the number density profiles ⟨ρ­(z)⟩ of each individual species as a function of distance from the electrodes (Na (100) and NVPOF (100) planes, respectively) (Figure a–c). Here, the (100) crystal planes of both electrodes were chosen for their predominant exposure to the electrolyte due to low surface energy. , At the potential of zero charge (PZC), where no surface charge density was applied (0 μC/cm 2 ), the electrolyte composition near the electrode surfaces roughly resembles that in the bulk. However, one prominent observation is that the relative density of HTCN molecules experienced an obvious spike at near 3 Å to the NVPOF (100) surface, indicative of their accumulation at the NVPOF surface.…”

Sodium–gallium alloy layer for fast and reversible sodium deposition

“…These beneficial characteristics of the alloy layer afford a uniform plating with no growth of dendrites and a flat morphology for metal ions. 39 Ga metal has a low melt temperature (30 • C), and can easily alloy with Na metal. Nevertheless, there is so far no report about employing a Na-Ga alloy layer to enhance the interface stability of the Na anode.…”

“…And the higher inertness of alloy layer compared with the pure metals alone favors reducing the parasitic reactions with organic electrolytes. These beneficial characteristics of the alloy layer afford a uniform plating with no growth of dendrites and a flat morphology for metal ions 39 . Ga metal has a low melt temperature (30°C), and can easily alloy with Na metal.…”

Sodium titanate nanowires for Na+‐based hybrid energy storage with high power density

“…To date, a wide range of anode materials have been synthesized and investigated to promote the practical application of SIBs, yet few of them can ideally meet the desired performance 3,4 . Alloy anode materials are impeded by the slow reaction kinetics and serious volume change during the insertion/extraction process of sodium ions 5–7 . Sodium metal anode with an ultrahigh theoretical capacity of 1166 mAh g −1 is impeded by the growth of metallic Na dendrites and unstable solid‐electrolyte interphase 8,9 .…”