Construction of oxygen vacancy-rich ZnO@carbon nanofiber aerogels as a free-standing anode for superior lithium storage.

The development of next-generation high-capacity freestanding materials as electrodes in lithium-ion batteries (LIBs) has significant potential. Here, oxygen vacancy-rich ZnO (Ov-ZnO) deposited on carbonized bacterial cellulose (CBC) aerogels is developed via in-situ uniformly growing ZIF-8-NH2 particles on CBC aerogels, followed by the hydrazine reduction and pyrolysis. The CBC serves as a free-standing skeleton to disperse and support ZIF-8-NH2 derived ZnO while the introduction of oxygen vacancies can effectively promote the internal ion/electron transfer. As a result, the obtained free-standing aerogels (Ov-ZnO@CBC) displays a reversible capacity of 710 mAh g-1 at 1 A g-1 after 1000 cycles, which is superior to ZnO@CBC without hydrazine reduction treatment. Furthermore, the assembled Li free-standing full cell using the Ov-ZnO@CBC composite as the anode and BC@LiFePO4 (BC@LFP) as the cathode exhibits an outstanding cycling performance of 150 mAh g-1 after 100 cycles at 0.1 A g-1, displaying satisfactory lithium-ion storage capability. It is noteworthy that both Ov-ZnO@CBC and BC@LFP are obtained in the form of a free-standing aerogel. This work offers a strategy to prepare high-capacity and long-cycle self-supporting aerogel-based electrodes for flexible LIBs.

Tailoring the morphology and electrochemical properties of Co-ZIF-L derived CoNi layered double hydroxides via Ni2+ etching towards high-performance supercapacitors.

The metal ion etching induced transformation of zeolitic imidazolate frameworks (ZIFs) to layered double hydroxides (LDHs) is closely related to the etching conditions. Here, by tuning the Ni2+ etching conditions (e.g., initial Ni2+ concentration and etching time), Co-ZIF-L templated CoNi-LDH with diverse morphologies and tailorable compositions are obtained and their resultant electrochemical properties are optimized. Mechanism study reveals that the etching conditions significantly affect the disassembling rate of Co-ZIF-L as well as the formation rate of CoNi-LDH, leading to the morphological and compositional variance of etched samples, which further results in their distinct electrochemical activities. The resultant asymmetric supercapacitor assembled with Co-ZIF-L derived CoNi-LDH and activated carbon can achieve a maximum energy density of 77.3 Wh/kg at a power density of 700 W/kg with the capacity retention of 85.7 % after 2000 cycles, superior or comparable to other advanced CoNi-LDH based supercapacitors.

Self-templated transformation of Co-ZIF-L into hierarchical porous CoS2/Co-Ni LDHs with improved electrochemical activities.

CoS2/Co-Ni layered double hydroxides (LDHs) with a rational tailored pore structure are developed by partial sulfurization of Co-ZIF-L and subsequent Ni2+ etching for the transformation of zeolitic imidazolate frameworks (ZIFs) to layered double hydroxides. The as-synthesized CoS2/Co-Ni LDHs maintain the leaf-like structure and have rich hierarchical pores. More importantly, CoS2 nanoparticles are uniformly embedded among Co-Ni LDH layers, facilitating mass diffusion and favorably exposing more active sites. Benefiting from these desirable compositional and structural features, a remarkable specific capacitance (capacity) of 1784 F/g (223 mAh/g) at 1 A/g is delivered by CoS2/Co-Ni LDHs. Furthermore, the as-assembled CoS2/Co-Ni LDH//activated carbon as the asymmetric supercapacitor device also exhibits a high energy density of 125 Wh/kg at a power density of 800 W/kg and a superb capacitance retention of 98 % after 5000 cycles, outperforming many Co-Ni LDH based electrode materials reported in the literature.

Lignocellulose hydrogels fabricated from corncob residues through a green solvent system.

It is still a challenge to find an effective solvent system that can simultaneously dissolve the cellulose and lignin in biomass residues to fabricate lignocellulose hydrogels (LHs). Herein, corncob residues from furfural production were pretreated with alkaline peroxide to regulate the lignin content. The lignin/cellulose composites with various lignin content were then dissolved and regenerated by a green and facile ZnCl2/CaCl2 solvent system. The inorganic salt solvents were served as linkers and flexible LHs were obtained. Substrate material containing 10.75% lignin shows the best compressive stress (76.71 kPa). Inspired by its superior ionic conductivity, the hydrogels were assembled into a solid-state electrolyte for a zinc-ion hybrid supercapacitor. This research develops a feasible, simple, and low-cost route for lignin-containing hydrogel preparation and offers insights into the high-value application of agro-industrial lignocellulosic wastes.