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Herein we report a simple and scalable route to synthesize porous cobalt/cobalt oxide - carbon sphere composites as anode material for rechargeable lithium-ion batteries. It involves the impregnation of starch-derived hydrochar spheres with a cobalt salt, followed by a heat treatment (700 °C) under inert atmosphere. The obtained high surface area (∼670 m 2  g −1 ), submicron spheres (∼300 nm diameter) with high-degree of microporosity (81%) consist of an amorphous carbon matrix with embedded Co/CoO nanoparticles (∼6 nm sized), having a total cobalt content of 6.2 wt%. The hybrid sphere anodes demonstrated superior specific capacity, rate performance and cycling stability. Discharge capacities of 520 and 310 mA h g −1 are observed at charge-discharge rates of 0.1 and 1C respectively. No significant capacity fading is identified on prolonged cycling at various current densities. The electrode also demonstratedexcellent structural stability during extended charge-discharge processes. [ABSTRACT FROM AUTHOR]

The remarkable achievement by Fujishima and Honda (1972) in the photo-electrochemical water splitting results in the extensive use of TiO 2 nanomaterials for environmental purification and energy storage/conversion applications. Though there are many advantages for the TiO 2 compared to other semiconductor photocatalysts, its band gap of 3.2 eV restrains application to the UV-region of the electromagnetic spectrum ( λ ≤ 387.5 nm). As a result, development of visible-light active titanium dioxide is one of the key challenges in the field of semiconductor photocatalysis. In this review, advances in the strategies for the visible light activation, origin of visible-light activity, and electronic structure of various visible-light active TiO 2 photocatalysts are discussed in detail. It has also been shown that if appropriate models are used, the theoretical insights can successfully be employed to develop novel catalysts to enhance the photocatalytic performance in the visible region. Recent developments in theory and experiments in visible-light induced water splitting, degradation of environmental pollutants, water and air purification and antibacterial applications are also reviewed. Various strategies to identify appropriate dopants for improved visible-light absorption and electron–hole separation to enhance the photocatalytic activity are discussed in detail, and a number of recommendations are also presented. [ABSTRACT FROM AUTHOR]

Porous carbon microsheet anodes with Li-ion storage capacity exceeding the theoretical limit are for the first time derived from waste packing-peanuts. Crystallinity, surface area, and porosity of these 1 μm thick carbon sheets were tuned by varying the processing temperature. Anodes composed of the carbon sheets outperformed the electrochemical properties of commercial graphitic anode in Li-ion batteries. At a current density of 0.1 C, carbon microsheet anodes exhibited a specific capacity of 420 mAh/g, which is slightly higher than the theoretical capacity of graphite (372 mAh/g) in Li-ion half-cell configurations. At a higher rate of 1 C, carbon sheets retained 4-fold higher specific capacity (220 mAh/g) compared to those of commercial graphitic anode. After 100 charge-discharge cycles at current densities of 0.1 and 0.2 C, optimized carbon sheet anodes retained stable specific capacities of 460 and 370 mAh/g, respectively. Spectroscopic and microscopic investigations proved the structural integrity of these high-performance carbon anodes during numerous charge-discharge cycles. Considerably higher electrochemical performance of the porous carbon microsheets are endorsed to their disorderness that facilitate to store more Li-ions than the theoretical limit, and porous 2-D microstructure enabling fast solid-state Li-ion diffusion and superior interfacial kinetics. The work demonstrated here illustrates an inexpensive and environmentally benign method for the upcycling of packaging materials into functional carbon materials for electrochemical energy storage. [ABSTRACT FROM AUTHOR]

An ordered network of interconnected tin oxide (SnO2) nanoparticles with a unique 3D architecture and an excellent lithium-ion (Li-ion) storage performance is derived for the first time through hydrolysis and thermal self-assembly of the solid alkoxide precursor. Mesoporous anodes composed of these ≈9 nm-sized SnO2 particles exhibit substantially higher specific capacities, rate performance, coulombic efficiency, and cycling stabilities compared with disordered nanoparticles and commercial SnO2. A discharge capacity of 778 mAh g-1, which is very close to the theoretical limit of 781 mAh g-1, is achieved at a current density of 0.1 C. Even at high rates of 2 C (1.5 A g-1) and 6 C (4.7 A g-1), these ordered SnO2 nanoparticles retain stable specific capacities of 430 and 300 mAh g-1, respectively, after 100 cycles. Interconnection between individual nanoparticles and structural integrity of the SnO2 electrodes are preserved through numerous charge-discharge process cycles. The significantly better electrochemical performance of ordered SnO2 nanoparticles with a tap density of 1.60 g cm-3 is attributed to the superior electrode/electrolyte contact, Li-ion diffusion, absence of particle agglomeration, and improved strain relaxation (due to tiny space available for the local expansion). This comprehensive study demonstrates the necessity of mesoporosity and interconnection between individual nanoparticles for improving the Li-ion storage electrochemical performance of SnO2 anodes. [ABSTRACT FROM AUTHOR]

Highly visible-Iight-active S,N-codoped anatase–rutile heterojunctions are reported for the first time. The formation of heterojunctions at a relatively low temperature and visible-light activity are achieved through thiourea modification of the peroxo–titania complex. FT-IR spectroscopic studies indicated the formation of a Ti4+–thiourea complex upon reaction between peroxo–titania complex and thiourea. Decomposition of the Ti4+–thiourea complex and formation of visible-light-active S,N-codoped TiO2 heterojunctions are confirmed using X-ray diffraction, Raman spectroscopy, transmission electron microscopy, and UV/vis spectroscopic studies. Existence of sulfur as sulfate ions (S6+) and nitrogen as lattice (N–Ti–N) and interstitial (Ti–N–O) species in heterojunctions are identified using X-ray photoelectron spectroscopy (XPS) and FT-IR spectroscopic techniques. UV–vis and valence band XPS studies of these S,N-codoped heterojunctions proved the fact that the formation of isolated S 3p, N 2p, and Π* N–O states between the valence and conduction bands are responsible for the visible-light absorption. Titanium dioxide obtained from the peroxo–titania complex exists as pure anatase up to a calcination temperature as high as 900 °C. Whereas, thiourea-modified samples are converted to S,N-codoped anatase–rutile heterojunctions at a temperature as low as 500 °C. The most active S,N-codoped heterojunction 0.2 TU-TiO2 calcined at 600 °C exhibits a 2-foId and 8-fold increase in visible-light photocatalytic activities in contrast to the control sample and the commercial photocatalyst Degussa P-25, respectively. It is proposed that the efficient electron–hole separation due to anatase to rutile electron transfer is responsible for the superior visible-light-induced photocatalytic activities of S,N-codoped heterojunctions. [ABSTRACT FROM AUTHOR]

The effect of 1,3-dioxolane (DOL) based electrolyte solutions(DOL/LiTFSIand DOL/LiTFSI-LiNO3) on the electrochemical performanceand surface chemistry of silicon nanowire (SiNW) anodes was systematicallyinvestigated. SiNWs exhibited an exceptional electrochemical performancein DOL solutions in contrast to standard alkyl carbonate solutions(EC-DMC/LiPF6). Reduced irreversible capacity losses, enhancedand stable reversible capacities over prolonged cycling, and lowerimpedance were identified with DOL solutions. After 1000 charge–dischargecycles (at 60 °C and a 6 C rate), SiNWs in DOL/LiTFSI-LiNO3solution exhibited a reversible capacity of 1275 mAh/g, whereasonly 575 and 20 mAh/g were identified in DOL/LiTFSI and EC-DMC solutions,respectively. Transmission electron microscopy (TEM) studies demonstratedthe complete and uniform lithiation of SiNWs in DOL-based electrolytesolutions and incomplete, nonuniform lithiation in EC-DMC solutions.In addition, the formation of compact and uniform surface films onSiNWs cycled in DOL-based electrolyte solutions was identified byscanning electron microscopic (SEM) imaging, while the surface filmsformed in EC-DMC based solutions were thick and nonuniform. X-rayphotoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR)spectroscopy were employed to analyze the surface chemistry of SiNWscycled in EC-DMC and DOL based electrolyte solutions. The distinctivesurface chemistry of SiNWs cycled in DOL based electrolyte solutionswas found to be responsible for their enhanced electrochemical performances. [ABSTRACT FROM AUTHOR]

An ordered 3D network of interconnected SnO2 nanoparticles is reported by Vilas G. Pol and co‐workers in article number 1401289. Superior Li‐ion storage of these ordered SnO2 nanoparticles is attributed to the enhanced electrode/electrolyte contact, Li‐ion diffusion, the absence of particle agglomeration, and improved strain relaxation. This work proves the necessity of mesoporosity and interconnected microstructure for stable electrochemical performance of SnO2 anodes. [ABSTRACT FROM AUTHOR]

A high reversible Li-ion storage capacity (200 mAh/g) with C/10 rate and good rate capability is achieved in reduced graphene oxide (rGO) wrapped anatase mesoporous TiO 2 nanofiber anodes fabricated by electrospinning. X-ray analysis of rGO wrapped TiO 2 nanofibers confirmed the crystalline anatase structure of TiO 2 , while Raman spectroscopy established high frequency shift caused by the interaction of TiO 2 with 2–4 layers of rGO. FT-IR analysis of rGO wrapped TiO 2 nanofibers revealed disappearance of C C, C O, and C OH stretching frequencies suggesting the successful reduction of GO to graphene, further confirmed by X-ray Photoelectron spectroscopy. The BET surface area of TiO 2 nanofibers (54 m 2 g − 1 ) increased to 105 m 2 g − 1 after wrapping rGO leading to mesoporous structure with pore diameters 5–20 nm, complementary observations with scanning and transmission electron microscopies. The oxidation/reduction peaks revealed lithium insertion and lithium extraction mechanism, from 1D TiO 2 fibers with superior electrode/electrolyte contacts, with shorter Li-ion diffusion length and improved ionic conductivity. Successful anchoring of rGO on TiO 2 nanofiber with Ti 3 + -C bonds energetically favors the electrochemical reaction yielding high rate and specific TiO 2 capacity as a promising anode of lithium ion battery. [ABSTRACT FROM AUTHOR]

• Defect engineered hexagonal boron nitride (hBN) anode to overcome the safety and performance limitations of current generation Li-ion batteries. • Reversible LiF formation catalyzed by defects in hBN to enable the pseudocapacitive type Li-ion storage on the hBN surface. • Non-flammability and excellent thermal tolerance of hBN allows a high specific capacity (880 mAh/g @ 25 mA/g), rate performance (480 mAh/g @ 5 A/g) and stable cycling (5000 cycles) at 60 °C. • The power and energy density are 3–4 times improved in the full cell with the defective hBN anode. The mass market adoption of electric vehicles has increased the risk of safety concerns, such as overheating and flammability. Rational design of fire-safe and high-capacity anodes with thermal tolerance, capable of fast-charging and long cycle-life, is crucial for the development of next generation Li-ion batteries operating under extreme conditions. Here we report a defect engineered hexagonal boron nitride (hBN) anode to mediate the safety dilemma. We demonstrate that the defects generated via cryomilling catalyze the reversible LiF formation and enable the pseudocapacitive type Li-ion storage on hBN. The non-flammability and excellent thermal tolerance of hBN allows high specific capacity (880 mAh/g @ 25 mA/g), rate performance (480 mAh/g @ 5 A/g) and stable cycling (5000 cycles) at 60 °C. The Li-ion full-cell with the defective hBN anode and the conventional cathode (LiNiMnCoO 2) delivers significantly higher energy (400 Wh kg−1) and power density (1 kW kg−1) when compared to graphite/LiNiMnCoO 2 full-cells (121 Wh kg−1 and 250 W kg−1). First-principles calculations confirm that nitrogen antisite (N B V N) defects are responsible for the electrochemical activation of otherwise inactive hBN. The strategy of defect-induced electrochemical activation opens up new avenues in the design of high-performance electrode materials for numerous secondary batteries. [ABSTRACT FROM AUTHOR]

Secondary lithium-ion batteries are restricted in large-scale applications including power grids and long driving electric vehicles owing to the low specific capacity of conventional intercalation anodes possessing sluggish Li-ion diffusion kinetics. Herein, we demonstrate an unusual pseudocapacitive lithium-ion storage on defective Co3O4 nanosheet anodes for high-performance rechargeable batteries. Cobalt-oxide nanosheets presented here composed of various defects including vacancies, dislocations and grain boundaries. Unique 2D holey microstructure enabled efficient charge transport as well as provided room for volume expansions associated with lithiation-delithiation process. These defective anodes exhibited outstanding pseudocapacitance (up to 87%), reversible capacities (1490 mAh gâ€"1 @ 25 mA gâ€"1), rate capability (592 mAh gâ€"1 @ 30 A gâ€"1), stable cycling (85% after 500 cycles @ 1 A gâ€"1) and columbic efficiency (∼100%). Exceptional Li-ion storage phenomena in defective Co3O4 nanosheets is accredited to the pseudocapacitive nature of conversion reaction resulting from ultrafast Li-ion diffusion through various crystal defects. The demonstrated approach of defect-induced pseudocapacitance can also be protracted for various low-cost and/or eco-friendly transition metal-oxides for next-generation rechargeable batteries. [ABSTRACT FROM AUTHOR]

Although secondary Li-ion batteries are widely used for electrochemical energy storage, low energy (100–300 Wh kg−1) and power density (250–400 W kg−1) are limiting their applications in several areas including long-range electric vehicles. Herein, we demonstrate high energy (400 Wh kg−1) and power density (1 kW kg−1) Li-ion batteries (considering the weight of both electrodes) based on extremely pseudocapacitive interface engineered CoO@3D-NRGO hybrid anodes. These values are 2.8 and 2.3-fold higher respectively compared to graphite‖LiNiMnCoO 2 full-cells under similar experimental conditions. Three-dimensional anode architecture presented here composed of ultrafine CoO nanoparticles (∼10 nm) chemically bonded to nitrogen-doped reduced graphene-oxide. This hybrid anode demonstrated excellent pseudocapacitance (∼92%), specific capacity (1429 mAh g−1 @ 25 mA g−1), rate performance (906 mAh g−1 @ 5 A g−1), and cycling stability (990 mAh g−1 after 7500 cycles @ 5 A g−1). Outstanding electrochemical performance of CoO@3D-NRGO‖LiNiMnCoO 2 full-cells is credited to the extreme pseudocapacitance of CoO@3D-NRGO anode resulting from Li 2 O/Co/NRGO nanointerfaces and Co–O–C bonds. The demonstrated strategy of interfacial engineering can also be extended for other environmental friendly/inexpensive transition metal oxide (Fe 2 O 3 , MnO 2 etc.) anodes for high energy/power density and ultra-long-life Li-ion batteries. Image 1 • Extremely pseudocapacitive CoO@3D-NRGO hybrid Li-ion battery anodes are developed. • Li-ion battery exhibited high energy (400 Wh kg−1) and power density (1 kW kg−1). • These values are 2.8 and 2.3-fold higher compared to graphite anode based system. • Li 2 O/Co/NRGO nanointerfaces and Co–O–C bonds caused extreme pseudocapacitance. • This strategy provides new opportunities to design advanced Li-ion batteries. [ABSTRACT FROM AUTHOR]

Sodium-ion batteries are considered a promising alternative to lithium-ion batteries due to its low cost and potential applications for large-scale energy storage. In this work, we focus on improving the Na-ion storage electrochemical performance of TiO 2 anodes by using diglyme-based electrolyte solutions. Significantly better performances are observed for the first time in diglyme-based electrolyte solution, as compared to conventional carbonate electrolyte solutions with and without additives such as fluoroethylene carbonate (FEC) and vinylene (VC). The best TiO 2 electrode demonstrated a high specific capacity of 248 mA h g−1 at 25 mA g−1 current density, ∼100% coulombic efficiency, superior pseudocapacitive Na-ion storage, and good capacity retention on extended galvanostatic charge-discharge cycles. A full-cell assembled with TiO 2 anode, Na 3 V 2 (PO 4) 3 cathode and NaPF 6 -diglyme electrolyte solution demonstrated an energy density as high as 440 W h kg−1. Superior electrochemical performance of TiO 2 anodes in diglyme-based electrolyte is credited to the enhanced passivation and Na-ion conducting properties of polyether-based solid electrolyte interfaces (SEI) compared to polycarbonate-based counterparts. Carbon coating also resulted in the reduced decomposition of both diglyme and carbonate based electrolyte solutions. These results potentially encourage the use of ether-based electrolyte solutions for further improving the electrochemical performance and commercialization of rechargeable Na-ion batteries. Image 1 • Novel application of diglyme-based electrolyte for TiO 2 and C@TiO 2 nanosheets. • Enhanced electrochemical performance in diglyme as compared to carbonate-based ones. • Na-ion full cells are built with C@TiO 2 , diglyme and Na 3 V 2 (PO 4) 3. • Full cells show high energy density (440 W h kg−1) and electrochemical stability. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fast-charging and ultralong-life Mg-Na hybrid battery is presented. • Hierarchical TiO 2- B nanosheet cathode exhibited outstanding pseudocapacitance. • In-situ XRD measurements revealed unique Mg-Na dual-ion storage mechanism. • This strategy present new opportunities to design advanced Mg-Na hybrid batteries. Despite of their inexpensive and sustainable characteristics, practical application of Mg-Na hybrid batteries are limited due to the lack of high performance dual-ion compatible cathode materials. This is mainly due to the increased size of Na-ions and improved electrostatic repulsion resulting from the high charge density of Mg-ions. Herein, we report for the first time a fast charging and ultralong-life Mg-Na hybrid battery based on an extremely pseudocapacitive hierarchical bronze TiO 2 (TiO 2 -B) nanosheet cathode. This two dimensional cathode exhibited outstanding pseudocapacitance (up to 94%), specific capacities (195 mAh/g @ 25 mA/g), rate performance (140 mAh/g @ 1A/g), cycling stability (∼76% after 6000 cycles @ 1A/g), coulombic efficiency (∼100%) and fast-charging (∼8 min). These performances are vastly superior to the previously reported metal oxide type Mg-Na hybrid battery cathodes. Mechanistic investigations revealed Mg-Na dual-ion intercalation pseudocapacitance with no significant structural changes. Exceptional electrochemical performance of the TiO 2 -B nanosheet cathode is credited to the dominant pseudocapacitive Mg-Na dual-ion diffusion through the nanointerfaces resulting from the hierarchical microstructure of TiO 2 -B nanosheets. High surface area, ultrathin nature and mesoporous structure are also contributed as secondary factors by facilitating superior contact with the electrolyte solution. The demonstrated method of nanointerfaces induced pseudocapacitive Mg-Na dual-ion intercalation provides new opportunities for the development of high-performance Mg-Na hybrid batteries. [ABSTRACT FROM AUTHOR]

[Display omitted] • A multifunctional UiO-66 modified PVDF-HFP separator is presented. • UiO-66 significantly improves the dimensional thermal stability of the separator. • UiO-66 selectively transports Na-ion inducing a high ionic conductivity. • A quasi-solid-state Na-ion hybrid capacitor based on the separator is fabricated. • The device demonstrates excellent electrochemical performance. The practical application of sodium-ion hybrid capacitors is limited by their low energy densities resulted from the kinetics mismatch between cathodes and anodes, and the fire safety related to the flammable electrolyte-separator system. Hence, we report a rational design of metal–organic frameworks (MOFs, UiO-66) modified PVDF-HFP separator. High tensile strength and dimensional thermal stability of the separator reduce the risk of electrode short circuit caused by the separator deformation. MCC test demonstrates a reduction of 75% in peak heat release rate (pHRR), indicating an enhanced fire-resistant property of the separator. This is due to the transformation of UiO-66 into ZrO 2 accompanied by the consumption of oxygen and the formation of the barrier char that suppresses further heat release. Quasi-solid-state electrolyte prepared based on this separator presents an enhanced ionic conductivity of 2.44 mS cm−1 and Na-ion transference number of 0.55, which are related to the high porosity (>70%) and electrolyte uptake (~320%) of the separator. Moreover, the open metal sites of UiO-66 can capture PF 6 –and consequently liberate the Na+ for faster migration, thus reducing the kinetics mismatch between cathodes and anodes. Such multifunctional separator enables the quasi-solid-state Na-ion hybrid capacitor to achieve high energy density (182 Wh kg−1 @31 W kg−1) and power density (5280 W kg−1 @22 Wh kg−1), as well as excellent cyclic stability (10,000 cycles @1000 mA g−1). [ABSTRACT FROM AUTHOR]

Although Mg–Li hybrid batteries are proposed as an alternative to Mg-batteries, the lack of dual-ion compatible cathodes are limiting their practical application. Herein, we report a high-rate and ultralong-life Mg–Li hybrid battery based on a dual-phase TiO 2 cathode. Highly pseudocapacitive hierarchical two-dimensional TiO 2 consists of anatase (60%) and bronze (40%) nanocrystallites forming interfaces due to crystal structure mismatch. This dual-phase hierarchical cathode exhibits excellent pseudocapacitance (up to 92%), specific capacities (235 mAh/g @ 25 mA/g), rate performance (120 mAh/g @ 1A/g) cycling stability (~87% after 3000 cycles @ 1A/g) and coulombic efficiency (~100%). These results are vastly superior to the previously reported values for TiO 2 based Mg–Li hybrid battery cathodes. Only minimal structural changes are observed during the charge-discharge of two-dimensional TiO 2 electrode. Outstanding electrochemical performance of dual-phase TiO 2 nanosheet cathode is attributed to the superior pseudocapacitive Mg/Li-ion diffusion through nanointerfaces between anatase and bronze crystallites. While other structural features such as 2D-morphology, ultrathin nature, mesoporosity, and high surface area act as secondary factors. The demonstrated approach for efficient pseudocapacitive Mg/Li-ion intercalation enhanced by nanointerfaces can be further exploited in the development of other high performance electrodes for advanced Mg–Li hybrid batteries. [Display omitted] • High-rate and ultralong-life Mg–Li hybrid battery is presented. • Dual-phase TiO 2 nanosheet cathode exhibited outstanding Mg/Li-ion storage. • Anatase-bronze nanointerfaces caused excellent pseudocapacitance. • This tactic provides new opportunities to design advanced Mg–Li hybrid batteries. [ABSTRACT FROM AUTHOR]