A Highly Dispersed Cobalt Electrocatalyst with Electron-Deficient Centers Induced by Boron toward Enhanced Adsorption and Electrocatalysis for Room-Temperature Sodium-Sulfur Batteries.

As vitally prospective candidates for next-generation energy storage systems, room-temperature sodium-sulfur (RT-Na/S) batteries continue to face obstacles in practical implementation due to the severe shuttle effect of sodium polysulfides and sluggish S conversion kinetics. Herein, the study proposes a novel approach involving the design of a B, N co-doped carbon nanotube loaded with highly dispersed and electron-deficient cobalt (Co@BNC) as a highly conductive host for S, aiming to enhance adsorption and catalyze redox reactions. Crucially, the pivotal roles of the carbon substrate in prompting the electrocatalytic activity of Co are elucidated. The experiments and density functional theory (DFT) calculations both demonstrate that after B doping, stronger chemical adsorption toward polysulfides (NaPSs), lower polarization, faster S conversion kinetics, and more complete S transformation are achieved. Therefore, the as-assembled RT-Na/S batteries with S/Co@BNC deliver a high reversible capacity of 626 mAh g-1 over 100 cycles at 0.1 C and excellent durability (416 mAh g-1 over 600 cycles at 0.5 C). Even at 2 C, the capacity retention remains at 61.8%, exhibiting an outstanding rate performance. This work offers a systematic way to develop a novel Co electrocatalyst for RT-Na/S batteries, which can also be effectively applied to other transition metallic electrocatalysts.

Highly graphited carbon-coated FeTiO3 nanosheets in situ derived from MXene: an efficient bifunctional catalyst for Zn-air batteries.

Developing high-efficiency and low-cost catalysts for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is of great significance for the commercialization of rechargeable metal-air batteries. Herein, we demonstrated the construction of graphited carbon-coated FeTiO3 (FeTiO3@C) via in situ annealing Ti3C2Tx nanosheets in a rusted-reactor and its efficient bifunctional activity for rechargeable Zn-air batteries (RZABs). The electron-transport dynamics of FeTiO3@C can be improved by using highly conductive graphited carbon derived from Ti3C2Tx. The FeTiO3@C catalyst annealed at 500 °C exhibits excellent OER and ORR activities. Specifically, FeTiO3@C shows a low overpotential of 323 mV at 10 mA cm-2 and a small Tafel slope of 53 mV dec-1 towards the alkaline OER. During the OER process, FeTiO3@C can be partially converted into highly active iron oxyhydroxide via in situ electrochemical reconstruction, which serves as the active species. After being assembled to RZABs, it shows an open-circuit potential of 1.33 V, a high trip efficiency of 63.4% and long-time cycling stability. This work can provide a new avenue for developing bifunctional electrocatalysts for RZABs used in portable devices.

Constructing a Stable Si-N-Enriched Interface Boosts Lithium Storage Kinetics in a Silicon-Based Anode.

The stable operation of a SiOx anode largely depends on the intrinsic chemistry of the electrode/electrolyte interface; however, an unstable interface structure and undesirable parasitic reactions with the electrolyte of the SiOx anode often result in the formation of a fragile solid-electrolyte interphase (SEI) and serious capacity decay during the lithiation/delithiation process. Herein, a Si-N-enriched N-doped carbon coating is constructed on the surface of SiOx yolk-shell nanospheres (abbreviated as SiOx@NC) to optimize the SEI film. The two-dimensional covalently bound Si-N interface, on one hand, can suppress the interfacial reactivity of the SiOx anode to enable the formation of a thin SEI film with accelerated diffusion kinetics of ions and, on the other hand, acts as a Li+ conductor during the delithiation process, allowing Li+ to diffuse rapidly in the SiOx matrix, thereby improving the long-term cycling stability and rapid charge/discharge capability of the SiOx anode. A series of characterizations show that the interface charge-transfer barrier and the Li+ diffusion energy barrier through the SEI film are the main factors that determine the interfacial electrochemical behavior and lithium storage performance. This work clarifies the relationship between the SEI characteristics and the interfacial transfer dynamics and aims to offer a more basic basis for the screening of other electrode materials.