Aoxuan Wang

Processable and Moldable Sodium Metal Anodes

Sodium-ion batteries are similar in concept and function to lithium-ion batteries, but their development and commercialization lag far behind. One obstacle is the lack of a standard reference electrode. Unlike Li foil reference electrodes, sodium is not easily processable or moldable and it deforms easily. Herein we fabricate a processable and moldable composite Na metal anode made from Na and reduced graphene oxide (r-GO). With only 4.5 % percent r-GO, the composite anodes had improved hardness, strength, and stability to corrosion compared to Na metal, and can be engineered to various shapes and sizes. The plating/stripping cycling of the composite anode was significantly extended in both ether and carbonate electrolytes giving less dendrite formation. We used the composite anode in both Na-O2 and Na-Na3 V2 (PO4 )3 full cells.

Porous Al Current Collector for Dendrite-Free Na Metal Anodes

Na-based batteries are proposed as promising energy storage candidates for beyond Li-ion technology due to the higher natural earth of Na metal. For its high capacity and low potential, Na metal may carve itself a niche when directly used as anodes. Similar to or even more problematic than Li, however, uneven plating/stripping of Na leads to dendrite formation. As the plating substrates, current collectors have a paramount influence on the Na plating/stripping behaviors. Here we propose porous Al current collectors as the plating substrate to suppress Na dendrites. Al does not alloy with Na. It is advantageous over Cu current collectors in terms of cost and weight. The interconnected porous structure can increase available surface for Na to nucleate and decrease the Na+ flux distribution, leading to homogeneous plating. The Na metal anodes can run for over 1000 cycles on porous Al with a low and stable voltage hysteresis and their average plating/stripping Coulombic efficiency was above 99.9%, which is greatly improved compared to planar Al. We used the porous Al for Na-O2, Na-Na3V2(PO4)3 cells with low Na amount and anode free Na-TiS2 batteries and anticipate that using this strategy can be combined with further electrolyte and cathodes to develop high performance Na-based batteries.

Bending‐Tolerant Anodes for Lithium‐Metal Batteries

Bendable energy-storage systems with high energy density are demanded for conformal electronics. Lithium-metal batteries including lithium-sulfur and lithium-oxygen cells have much higher theoretical energy density than lithium-ion batteries. Reckoned as the ideal anode, however, Li has many challenges when directly used, especially its tendency to form dendrite. Under bending conditions, the Li-dendrite growth can be further aggravated due to bending-induced local plastic deformation and Li-filaments pulverization. Here, the Li-metal anodes are made bending tolerant by integrating Li into bendable scaffolds such as reduced graphene oxide (r-GO) films. In the composites, the bending stress is largely dissipated by the scaffolds. The scaffolds have increased available surface for homogeneous Li plating and minimize volume fluctuation of Li electrodes during cycling. Significantly improved cycling performance under bending conditions is achieved. With the bending-tolerant r-GO/Li-metal anode, bendable lithium-sulfur and lithium-oxygen batteries with long cycling stability are realized. A bendable integrated solar cell-battery system charged by light with stable output and a series connected bendable battery pack with higher voltage is also demonstrated. It is anticipated that this bending-tolerant anode can be combined with further electrolytes and cathodes to develop new bendable energy systems.

Controlling Nucleation in Lithium Metal Anodes

Rechargeable batteries are regarded as the most promising candidates for practical applications in portable electronic devices and electric vehicles. In recent decades, lithium metal batteries (LMBs) have been extensively studied due to their ultrahigh energy densities. However, short lifespan and poor safety caused by uncontrollable dendrite growth hinder their commercial applications. Besides, a clear understanding of Li nucleation and growth has not yet been obtained. In this Review, the failure mechanisms of Li metal anodes are ascribed to high reactivity of lithium, virtually infinite volume changes, and notorious dendrite growth. The principles of Li deposition nucleation and early dendrite growth are discussed and summarized. Correspondingly, four rational strategies of controlling nucleation are proposed to guide Li nucleation and growth. Finally, perspectives for understanding the Li metal deposition process and realizing safe and high-energy rechargeable LMBs are given.