Fluorinated Artificial Solid-Electrolyte-Interphase Layer for Long-Life Sodium Metal Batteries

Interfacial modulation with homogeneous gallium phosphide protective layer enables dendrite-free and superior stable sodium metal anode

Sodium metal is heralded as a premier anode candidate poised to supplant lithium in next-generation rechargeable batteries due to its abundant availability, cost-effectiveness, and superior energy density. Due to the highly reactive nature of metallic sodium, an unstable solid electrolyte interphase (SEI) forms spontaneously on the Na metal anode. This instability leads to non-uniform sodium deposition during cycling, promoting dendrite growth and the accumulation of "dead" sodium. As a result, the cycling lifespan is significantly reduced, creating further complications. Herein, a facile in situ artificial interfacial layer of gallium phosphide (GaP) has been successfully constructed on the surface of sodium metal via a one-step method. This novel GaP protective layer, uniformly and densely distributed, effectively mitigates the instability of the sodium metal anode during the stripping/deposition process, resulting in enhanced structural integrity and the absence of dendritic growth. The Na/GaP symmetric cell exhibits low polarization voltage and a decreased energy barrier for Na+ diffusion during cycling, enabling stable operation for over 1200 h at a current density of 0.5 mA cm-2 (1 mAh cm-2). The inhibitory effect of the GaP interfacial layer on dendrite formation and the uniform deposition enhancement during the stripping and deposition processes of sodium metal anode were verified through in situ optical microscopy, along with complementary ex situ scanning electron microscope (SEM) and x-ray photoelectron spectroscopy (XPS) characterizations. After 1100 cycles at a high current rate of 5 C, a full cell made with a Na3V2(PO4)3 (NVP) cathode and a Na/GaP anode exhibits a reversible capacity of 90 mAh g-1. The NVP||Na/GaP complete cell also produces a remarkable energy density of 352.2 Wh kg-1. This work offers unique insights for the facile construction of mono-component sodium metal anode interfacial coatings and their related applications.

Advanced Interphases Layers for Dendrite-Free Sodium Metal Anodes

Sodium (Na) metal anode is considered the cornerstone of next-generation energy storage technology, owing to its high theoretical capacity and cost-effectiveness. However, the development of Na metal batteries is hindered by the instability and nonuniformity of the solid electrolyte interphase (SEI) and notorious formation of Na dendrites. Recently, various advanced artificial interphase designs have been developed to control notorious dendrite growth and stabilize the SEI layer. In this Review, we provide a comprehensive overview of artificial interphase designs, focusing on inorganic interphase layer, organic interphase layer, and hybrid inorganic/organic interphase layer, all aimed at inhibiting the notorious Na dendrites growth. Finally, future interphase engineering strategies are also envisioned to offer new insights into the optimization of Na anodes.

FEMC-deuterogenic artificial solid electrolyte interphase boosts high-performance sodium-ion batteries

A NaF-rich composite artificial interphase is in-situ generated relying on a simple chemical reaction by regulating methyl 2,2,2-trifluoromethyl ester reactivity, which can promote rapid ion transport and effectively inhibit dendrite growth in carbonate electrolytes. The assembled NaF@Na‖Na3V2(PO4)3 full cell attains a long lifespan of 4000 cycles at 5C with 95% capacity retention, and a high specific capacity of 80.8 mAh g-1 at 30C.

Intermetallic Layers with Tuned Na Nucleation and Transport for Anode-Free Sodium Metal Batteries

Sodium metal batteries without pre-deposited Na (anode-free) and with a limited amount of Na metal (anode-less) have attracted increasing attention due to their competitive energy density and the high abundance of sodium. However, severe interfacial issues result in poor cycling stability and low Coulombic efficiency. Here, the lightweight interphase layers composed of intermetallic nanoparticles (Sn-Cu and Sn-Ni) are applied to improve Na plating/stripping behaviors. These layers provide uniform seeding sites with high sodiophilicity and support fast ion transport. A reversible Na plating/stripping behavior, featuring a high Coulombic efficiency of ∼99.95% with a minor standard deviation of 0.0013, for 500 cycles at 1 mA cm-2 and 1 mAh cm-2 is achieved on SnCu-coated Al. Consequently, the anode-free Na3V2(PO4)3 full cell with a high loading of 7.6 mg cm-2 exhibits a capacity retention of 90% after 200 cycles. This strategy provides an effective pathway toward anode-free sodium metal batteries.

Highly Effective Polyacrylonitrile-Rich Artificial Solid-Electrolyte-Interphase for Dendrite-Free Li-Metal/Solid-State Battery

Lithium metal anode batteries have attracted significant attention as a promising energy storage technology, offering a high theoretical specific capacity and a low electrochemical potential. Utilizing lithium metal as the anode material can substantially increase energy density compared with conventional lithium-ion batteries. However, the practical application of lithium metal anodes has encountered notable challenges, primarily due to the formation of dendritic structures during cycling. These dendrites pose safety risks and degrade battery performance. Addressing these challenges necessitates the development of a reliable and effective protection layer for lithium metal. This study presents a cost-effective and convenient method to spontaneously produce lithium metal protective layers by creating polymeric layers by using acrylonitrile (AN). This method remarkably extends 6× of the lifetime of lithium metal anodes under high current density (1 mA/cm2) cycling conditions. While the cycle life of bare lithium metal is approximately 150 h under high current cycling conditions, AN-treated lithium metal anodes exhibit an impressive longevity of over 900 h. The AN-treated lithium metal anodes are further integrated and tested with sulfide-based Li10GeP2S12 (LGPS) solid-state electrolytes to evaluate its interfacial stability at a solid-solid interface. The formation of the polyacrylonitrile (PAN)-rich ASEI, due to AN-treatment, effectively reduces and stabilizes the cell overpotential to only one-tenth of that with the interface without treatment. This strategy paves a route to enable a highly efficient and highly stable Li/LGPS solid-state battery interface.

A Critical Review on Room-Temperature Sodium-Sulfur Batteries: From Research Advances to Practical Perspectives

Room-temperature sodium-sulfur (RT-Na/S) batteries are promising alternatives for next-generation energy storage systems with high energy density and high power density. However, some notorious issues are hampering the practical application of RT-Na/S batteries. Besides, the working mechanism of RT-Na/S batteries under practical conditions such as high sulfur loading, lean electrolyte, and low capacity ratio between the negative and positive electrode (N/P ratio), is of essential importance for practical applications, yet the significance of these parameters has long been disregarded. Herein, it is comprehensively reviewed recent advances on Na metal anode, S cathode, electrolyte, and separator engineering for RT-Na/S batteries. The discrepancies between laboratory research and practical conditions are elaborately discussed, endeavors toward practical applications are highlighted, and suggestions for the practical values of the crucial parameters are rationally proposed. Furthermore, an empirical equation to estimate the actual energy density of RT-Na/S pouch cells under practical conditions is rationally proposed for the first time, making it possible to evaluate the gravimetric energy density of the cells under practical conditions. This review aims to reemphasize the vital importance of the crucial parameters for RT-Na/S batteries to bridge the gaps between laboratory research and practical applications.