Concept: Nickel-metal hydride battery
Porous SnO(2)/graphene composite thin films are prepared as anodes for lithium ion batteries by the electrostatic spray deposition technique. Reticular-structured SnO(2) is formed on both the nickel foam substrate and the surface of graphene sheets according to the scanning electron microscopy (SEM) results. Such an assembly mode of graphene and SnO(2) is highly beneficial to the electrochemical performance improvement by increasing the electrical conductivity and releasing the volume change of the anode. The novel engineered anode possesses 2134.3 mA h g(-1) of initial discharge capacity and good capacity retention of 551.0 mA h g(-1) up to the 100th cycle at a current density of 200 mA g(-1). This anode also exhibits excellent rate capability, with a reversible capacity of 507.7 mA h g(-1) after 100 cycles at a current density of 800 mA g(-1). The results demonstrate that such a film-type hybrid anode shows great potential for application in high-energy lithium-ion batteries.
A Si/graphene composite is drop-casted on an ultrathin-graphite foam (UGF) with three dimensional conductive network. The Si/graphene/UGF composite presents excellent stability and relatively high overall capacity when tested as an anode for rechargeable lithium ion batteries.
Down to the wire: Three-dimensional interconnected Si-based nanowires are produced through the combination of thermal decomposition of SiO and a metal-catalyzed nanowire growth process. This low-cost and scalable approach provides a promising candidate for high-capacity anodes in lithium-ion batteries.
Spinel-type LiNi0.5Mn1.5O4 porous nanorods assembled with nanoparticles have been prepared and investigated as high-rate and long-life cathode materials for rechargeable lithium-ion batteries. One dimensional porous nanostructures of LiNi0.5Mn1.5O4 with ordered P4332 phase were obtained through solid-state Li and Ni implantation of porous Mn2O3 nanorods that resulted from thermal decomposition of the chain-like MnC2O4 precursor. The fabricated LiNi0.5Mn1.5O4 delivered specific capacities of 140 and 109 mAh g-1 at 1 C and 20 C rate, respectively. At 5 C cycling rate, a capacity retention of 91% was sustained after 500 cycles, with extremely low capacity fade (< 1%) during the initial 300 cycles. The remarkable performance was attributed to the porous 1D nanostructures that can accommodate strain relaxation by slippage at the subunits wall boundaries and provide short Li-ion diffusion distance along the confined dimension.
On page 6111, X. Chen and co-workers report for the first time a protocol to grow ultralong TiO2 -based nanotubes from tiny TiO2 nanoparticles by a stirring hydrothermal method. The study confirms that the mechanical-force-driven stirring process is the reason for the lengthening of the nanotubes. This protocol to synthesize elongated nanostructures can be extended to other nanostructured systems, opening up new opportunities for manufacturing advanced functional materials for high-performance energy-storage devices.
With the increased need for high-rate Li-ion batteries, it has become apparent that new electrode materials with enhanced Li-ion transport should be designed. Interfaces, such as twin boundaries (TBs), offer new opportunities to navigate the ionic transport within nanoscale materials. Here, we demonstrate the effects of TBs on the Li-ion transport properties in single crystalline SnO2 nanowires. It is shown that the TB-assisted lithiation pathways are remarkably different from the previously reported lithiation behavior in SnO2 nanowires without TBs. Our in situ transmission electron microscopy (TEM) study combined with direct atomic-scale imaging of the initial lithiation stage of the TB-SnO2 nanowires prove that the lithium ions prefer to intercalate in the vicinity of the (10-1) TB, which acts as conduit for lithium ion diffusion inside the nanowires. The DFT modeling shows that it is energetically preferred for lithium ions to accumulate near the TB compared to perfect neighboring lattice area. These findings may lead to design of new electrode materials incorporating TBs as efficient lithium pathways, and eventually the development of next generation rechargeable batteries surpassing the rate performance of the current commercial Li-ion batteries.
In rechargeable lithium-ion batteries, understanding the atomic-scale mechanism of Li-induced structural evolution occurring at the host electrode materials provides essential knowledge for design of new high performance electrodes. Here, we report a new crystalline-crystalline phase transition mechanism in single-crystal Zn-Sb intermetallic nanowires upon lithiation. Using in situ transmission electron microscopy, we observed that stacks of atomic planes in an intermediate hexagonal (h-)LiZnSb phase are “shuffled” to accommodate the geometrical confinement stress arising from lamellar nanodomains intercalated by lithium ions. Such atomic rearrangement arises from the anisotropic lithium diffusion and is accompanied by appearance of partial dislocations. This transient structure mediates further phase transition from h-LiZnSb to cubic (c-)Li2ZnSb that is associated with a nearly “zero-strain” coherent interface viewed along the h/c directions. This study provides new mechanistic insights into complex electrochemically driven crystalline-crystalline phase transitions in lithium-ion battery electrodes and represents a noble example of atomic-level structural and interfacial rearrangements.
A stirring hydrothermal process that enables the formation of elongated bending TiO2 -based nanotubes is presented. By making use of its bending nature, the elongated TiO2 (B) nanotubular cross-linked network anode electrode can cycle over 10000 times in half cells while retaining a relatively high capacity (114 mAh g(-1) ) at ultra-high rate of 25 C (8.4 A/g).
The performance of battery materials is largely governed by structural and chemical evolutions during electrochemical reactions. Therefore, resolving spatially dependent reaction pathways could enlighten mechanistic understanding, and enable rational design for rechargeable battery materials. Here, we present a phase evolution panorama via spectroscopic and three-dimensional imaging at multiple states of charge for an anode material (that is, nickel oxide nanosheets) in lithium-ion batteries. We reconstruct the three-dimensional lithiation/delithiation fronts and find that, in a fully electrolyte immersion environment, phase conversion can nucleate from spatially distant locations on the same slab of material. In addition, the architecture of a lithiated nickel oxide is a bent porous metallic framework. Furthermore, anode-electrolyte interphase is found to be dynamically evolving upon charging and discharging. The present study has implications for resolving the inhomogeneity of the general electrochemically driven phase transition (for example, intercalation reactions) and for the origin of inhomogeneous charge distribution in large-format battery electrodes.
Nano-structured silicon anodes are attractive alternatives to graphitic carbons in rechargeable Li-ion batteries, owing to their extremely high capacities. Despite their advantages, numerous issues remain to be addressed, the most basic being to understand the complex kinetics and thermodynamics that control the reactions and structural rearrangements. Elucidating this necessitates real-time in situ metrologies, which are highly challenging, if the whole electrode structure is studied at an atomistic level for multiple cycles under realistic cycling conditions. Here we report that Si nanowires grown on a conducting carbon-fibre support provide a robust model battery system that can be studied by (7)Li in situ NMR spectroscopy. The method allows the (de)alloying reactions of the amorphous silicides to be followed in the 2nd cycle and beyond. In combination with density-functional theory calculations, the results provide insight into the amorphous and amorphous-to-crystalline lithium-silicide transformations, particularly those at low voltages, which are highly relevant to practical cycling strategies.