Search

P2-type Na x Ni 1/3 Mn 2/3 O 2 is considered as one of the promising cathodes for sodium-ion batteries due to its low cost, low toxicity and high operating voltage. However, this material suffers the serious capacity decay and poor stability during cycling. Here, we performed the in-situ X-ray diffraction measurement to investigate the relationship among the voltage window, crystal structure evolution and capacity decay. Based on the finding that the capacity decay is mainly caused by the formation of oxygen anion group [O 2 ] x −(0＜ x ＜4), we controlled the voltage in 2.6–3.8 V to avoid the oxygen reaction and the capacity retention of the material has been improved from ∼14% (for 100 cycles) to 94.5% (for 500 cycles). Image 1 • The inferior capacity retention (only ∼14% for 100 cycles) was improved to 94.5% (for 500 cycles) by optimizing the voltage window. • The formation of oxygen anion group under high voltage is the main cause to the capacity decay. [ABSTRACT FROM AUTHOR]

Based on the ultra-fast faradaic surface induced reversible redox reactions, pseudocapacitance behavior with rapid electrochemical kinetics can boost the high power density of lithium ion battery. In this work, a three-dimensional (3D) interconnected porous reduced graphene oxide network incorporated with homogeneously dispersed ultra-fine α-Fe 2 O 3 nanoparticles (denoted α-Fe 2 O 3 @3DrGO) is subtly synthesised through a facial hydrothermal self-assembly process. Such desirable hierarchical structure delivers an ever-increasing pseudocapacitance storage as anode, achieving an unprecedented rate capacity (921.6, and 812.4 mA h g−1 at 1 and 5 A g−1) and a superior cycle performance with ultra-high capacity (1198.6 mA h g−1 at 1 A g−1 over 200 cycles), which is almost the best result reported so far. Even at a high current density of 5 A g−1, it still maintains the excellent cycle stability with a capacity of 396.6 mA h g−1 after 2000 cycles. Such outstanding electrochemical performance may be ascribed to the synergy of the robust structure, porous surface morphology as well as accompanying dominated pseudocapacitance behavior. We hope this work can provide a novel strategy for realizing high rate and stable cycle performances in lithium storage. The robust α-Fe2O3@3D porous reduced graphene oxide aerogel exhibits both remarkable rate performance and superior cycling performance, manifesting the potential application of ferrites oxide in advanced lithium-ion batteries. Image 1 • The robust 3D porous α-Fe 2 O 3 @3DrGO aerogel is synthesised through a facial hydrothermal self-assembly process. • The α-Fe 2 O 3 @3DrGO shows unprecedented rate and cycle performance (812.4 mA h g−1at 5 A g−1, 1198.6 mA h g−1at 1 A g−1for 200 cycles). • The α-Fe 2 O 3 @3DrGO electrode reveals an ever- increasing surface-induced psedocapacitive lithium storage behavior. [ABSTRACT FROM AUTHOR]

Rate performance is also a key parameter for silicon to replace graphite serving as anode materials for lithium-ion batteries (LIBs), except for its high theoretical specific capacity. Herein, we fabricated the B-doped Si flakes with high-rate performance from low-cost industrial Si-Ca alloy and B 2 O 3 via a facile molten-salt chemical exfoliation. The layered structure shortens diffusion ways of lithium ions. Moreover, B atoms in Si contribute to the increasement of the conductivity and the expansion of lattices. Benefiting from the doped and layered structure, the B-doped Si flakes electrode exhibits a specific capacity of ~800 mAh g−1 at 2 A g−1 with an initial coulombic efficiency of 81.5% and maintains 85% after 200 cycles. The reversible capacities of ~1250, ~1000 and ~842 mAh g−1 can be delivered at 0.4, 1, and 2 A g−1, respectively. The rational design of a special doped layered structure may propose a strategy for other materials. [Display omitted] • The boron-doped silicon flakes are synthesized in molten CaCl 2 -NaCl. • The Si-B composite shows layer-by-layer B-doped Si structure. • The Si-B composite shows excellent rate capability for lithium storage. [ABSTRACT FROM AUTHOR]

The application of Sn-based materials and transition metal oxides (TMOs) with high theoretical capacities as anodes for lithium ion batteries is severely limited for the low cycle lifespan due to huge volume changes. Combining the Sn-based or TMO materials with one-dimensional (1D) carbon nanofibers as a lithium storage anode is one of the effective means to improve the cycle stability, rate performance, initial coulombic efficiency and electrical conductivity of lithium ion batteries. In this work, a novel Sn particles coated composite of SnO x /ZnO and N-doped carbon nanofibers (Sn/SnO x /ZnO@N-CNFs) with high reversibility and long-life lithium storage boosted by pseudocapacitance behavior was fabricated using a simple electrospinning technique and subsequent calcining process. The high theoretical capacity of SnO 2 , high Li ion diffusion coefficient of ZnO, as well as stable cycle performance and great conductivity of N-CNFs were integrated into the composite by the synergistic effect, which delivers a high reversible capacity of 588.7 mAh/g after 100 cycles at a current density of 0.5 A/g. More importantly, in the case of great rate performance and cycle stability at high current density, the Sn/SnO x /ZnO@N-CNFs electrode is endowed with significantly improved initial coulombic efficiency and prominent advantage in electrical conductivity. The comprehensive performance, facile material fabrication method and enhanced pseudocapacitive lithium storage for Sn particles coated SnO x /ZnO and N-doped carbon nanofibers hybrid could contribute to the practical application of the updated energy storage devices. Sn coated SnO x /ZnO@N-CNF composites were fabricated by electrospinning technique and subsequent calcining process. The Sn/SnO x /ZnO-1@N-CNF electrode shows remarkable rate performance, great cycle stability, improved initial coulombic efficiency, boosted electrical conductivity and enhanced pseudocapacitive lithium storage in advanced lithium-ion batteries. Image 1 • The Sn coated SnO x /ZnO@N-CNF composites was fabricated using a facile electrospinning technique and subsequent calcining process. • The Sn/SnO x /ZnO@N-CNF electrode deliver a high reversible capacity of 588.7 mAh/g after 100 cycles at the current density of 0.5 A/g, with excellent rate performance, great electrical conductivity and high coulombic efficiency. • The high reversibility and long-life lithium storage of the Sn/SnO x /ZnO@N-CNF electrode is boosted by pseudocapacitance behavior. [ABSTRACT FROM AUTHOR]

Sub-valent silicon oxide (SiO x) is a promising next-generation anode material in lithium-ion batteries. However, SiO x still suffers large volume expansion during the lithiation, resulting in deteriorated battery performance. Herein, we report a low-cost and easy-to-scale-up method to prepare a SiO x -based anode (named as SiO x @G-Ni) by drop-casting the slurry of asphalt, micron-sized SiO x powder, nickel salt and carbon nanotubes onto a Cu foil and subsequent thermal pyrolysis. The obtained electrode consists of a rigid graphenic carbon network that is embedded with micron-sized SiO x , nickel nanoparticles and carbon nanotubes. The SiO x @G-Ni electrode delivers a specific charge capacity of 1061 mA h g −1 at 0.08 A g−1, and a capacity retention rate of 86.7 % after cycled 500 times at 1.6 A g−1. The full battery SiO x @G-Ni||LiCoO 2 reaches a capacity retention rate of 79.3 % after 250 cycles at 0.5 C. The method employed in this work could be used for the preparation of the SiO x -based anode for high-performance lithium-ion batteries. • Preparation of binder-free micron-sized SiO x electrodes by drop-casting method. • Utilize the catalytic effect of nickel particles to form a multilayer graphenic network. • The SiOx@G-Ni electrode delivers great half-cell and full-cell cycle performance. [ABSTRACT FROM AUTHOR]

Highlights: • The dehydrogenation properties of NaAlH4 are enhanced significantly by adding TiN. • The onset dehydrogenation temperature of 2%TiN–NaAlH4 is lowered to 130.0°C. • Approximately 5.44wt.% of hydrogen can be released from 2%TiN–NaAlH4 at 190.0°C. • TiN–NaAlH4 system indicates an excellent reversibility according to HP-DSC. [ABSTRACT FROM AUTHOR]

Abstract: Cu2S nanosheets and hexagonal nanoplates have been synthesized, respectively on either side of a copper substrate via a facile one-step hydrothermal process using ethylenediamine (en) and distilled water as co-solvent and cetyltrimethylammonium bromide (CTAB) as surfactant. X-ray diffraction (XRD), field emission scanning electron microscope (SEM), transmission electron microscope (TEM), selected area electron diffraction (SAED) and UV–vis spectra were used to characterize the obtained products. A reasonable formation mechanism of Cu2S nanostructures was proposed based on the experimental results. [Copyright &y& Elsevier]