Formation of Nanodimensional NiCoO2 Encapsulated in Porous Nitrogen-Doped Carbon Submicrospheres from a Bimetallic (Ni, Co) Organic Framework toward Efficient Lithium Storage.

Recently, rock-salt NiCoO2 (NCO) with desirable electronic conductivity has drawn enormous interest worldwide for energy-related applications. However, the intrinsically sluggish kinetics and electrode aggregation/volumetric change/pulverization during Li-insertion/-extraction processes hugely limit its applications in Li-ion batteries (LIBs). In the contribution, we first devise a bottom-up method for scalable fabrication of the nanodimensional NCO particles encapsulated in porous nitrogen-doped carbon submicrospheres (NCS), which are derived from a bimetal (Ni, Co) metal-organic framework. The porous NCS, as a flexible conductive skeleton, can buffer distinct volume expansion as an efficient buffering phase, restrain agglomeration of nanoscaled NCO, and enhance electronic conductivity and wettability of the electrode. Benefiting from the synergistic functions between the nanodimensional NCO and porous NCS, the obtained NCO@NCS anode (∼74.5 wt % NCO) is endowed with remarkable high-rate reversible capacity (∼403.0 mAh g-1 at 1.0 A g-1) and cycling behaviors (∼371.4 mAh g-1 after being cycled for 1000 times at 1.0 A g-1) along with a high lithium diffusion coefficient and remarkable pseudocapacitive contribution. Furthermore, the NCO@NCS-based full LIBs exhibit competitive lithium-storage properties in terms of energy density (∼217.0 Wh kg-1) and cyclic stability. Furthermore, we believe that the methodology is highly promising in versatile design and construction of binary metal oxide/carbon hybrid anodes for advanced LIBs.

A two-dimensional assembly of ultrafine cobalt oxide nanocrystallites anchored on single-layer Ti3C2Tx nanosheets with enhanced lithium storage for Li-ion batteries.

Recently, Ti-based MXenes were expected to compete with graphene and other carbonaceous materials towards Li-ion batteries (LIBs) due to their two-dimensional (2D) open structure, cost efficiency, superior conductivity and low Li+ diffusion barrier. However, the relatively moderate capacity and aggregation tendency hamper their practical applications in next-generation LIBs. Herein, we explore for the first time a scalable bottom-up approach to fabricate a series of Co3O4@single-layer Ti3C2Tx (s-Ti3C2Tx) hybrids, where numerous homogeneous Co3O4 nanocrystallites (NCs), serving both as a spacer and electroactive phase, are anchored uniformly on the surface of s-Ti3C2Tx nanosheets (NSs) through the Co-O-Ti interfacial bonds. Furthermore, detailed experimental analyses clearly shed light upon the formation mechanism of the hybrid Co3O4@s-Ti3C2Tx NSs. Thanks to the structural and compositional merits, the 2D Co3O4@s-Ti3C2Tx NSs even exhibit a remarkable high-rate capacity of ∼223 mA h g-1 at an ultra-high current density of 10 A g-1, and a long-span cycle life with a high reversible capacity of 550 mA h g-1 at 1 A g-1 after 700 consecutive cycles. Corresponding density functional theory calculation further confirms that the Co-O-Ti interfacial function leads to an even higher pseudocapacitive contribution and faster lithium storage behavior due to the enhanced interfacial electron transfer.

Ultralong Layered NaCrO2 Nanowires: A Competitive Wide-Temperature-Operating Cathode for Extraordinary High-Rate Sodium-Ion Batteries.

The development of high-rate cathodes particularly with remarkable wide-temperature-tolerance sodium-storage capability plays a significant role in commercial applications of sodium-ion batteries (SIBs). Herein, we devise a scaled-up electrospinning avenue to fabricate nanocrystal-constructed ultralong layered NaCrO2 nanowires (NWs) toward SIBs as a wide-temperature-operating cathode. The resultant one-dimensional (1D) NaCrO2 nanoarchitecture is endowed with orientated and shortened electronic/ionic transport and remarkable structural tolerance to stress change over sodiation-desodiation processes. Benefiting from these structural superiorities, the NaCrO2 NWs are featured with prominent Na+-storage behaviors in the wide-operating-temperature range from -15 to 55 °C. Promisingly, the NaCrO2 NWs exhibit extraordinary high-rate capacities of ∼108.8 and ∼87.2 mAh g-1 at 10 and 50 C rates at 25 °C, and even 94.6 (55 °C) and ∼60.1 (-15 °C) mAh g-1 at 10 C, along with outstanding cyclic stabilities with capacity retentions of ∼80.6% (-15 °C), 88.4% (25 °C), and ∼86.9% (55 °C). The overall performance of our NaCrO2 is superior to other reported NaCrO2-based cathodes, even with conductive nanocarbon coating. Encouragingly, a competitive energy density of ∼161 Wh kg-1 can be obtained by the NaCrO2 NWs-based full cell. Therefore, our NaCrO2 NWs can be highly anticipated as advanced cathode for commercial wide-temperature-tolerance SIBs.