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Although Mg–Li dual metal-ion batteries are proposed as a superior system that unite safety of Mg-batteries and performance of Li-ion based systems, its practical implantation is limited due to the lack of reliable high-performance cathodes. Herein, we report a high-performance Mg–Li dual metal-ion battery system based on highly pseudocapacitive hierarchical TiO2-B nanosheet assembled spheres (NS) cathode. This 2D cathode displayed exceptional pseudocapacitance (a maximum of 93%) specific capacity (303 mAh g −1 at 25 mA g−1), rate performance (210 mAh g −1 at 1 A g−1), consistent cycling (retain ∼100% capacity for 3000 cycles at 1 A g−1), Coulombic efficiency (nearly 100%) and fast-charging (∼12.1 min). These properties are remarkably dominant to the existing Mg-Li dual metal-ion battery cathodes. Spectroscopic and microscopic mechanistic studies confirmed negligible structural changes during charge-discharge cycles of the TiO2-B nanosheet assembled spheres electrodes. Exceptional electrochemical properties of the 2D electrode is ascribed to remarkable pseudocapacitive Mg–Li dual metal-ion diffusion via the numerous nanointerfaces of TiO2-B caused by its hierarchical microstrucrure. Large surface area, nanosheet morphology, mesoporous structure and ultrathin nature also acted as secondary factors facilitating improved electrode-electrolyte contact. Demonstrated approach of pseudocapacitive type Mg-Li dual metal-ion intercalation through hierarchical nanointerfaces may be further utilized for the designing of numerous top-notch electrode materials for futuristic Mg–Li dual metal-ion batteries. [ABSTRACT FROM AUTHOR]

Disordered carbon is the state of the art anode material for Na‐ion batteries due to their increased interlayer spacing and good electronic conductivity. However, its practical application is hindered by average specific capacity, poor rate performance, low coulombic efficiency and limited cycling stability. Herein, we report the superior pseudocapacitance enhanced Na‐ion storage of in situ surface functionalized carbon nanosheets. Anodes composed of ultrathin (~15 nm) carbon nanosheets demonstrated excellent reversible specific capacity (375 mAh/g at 25 mA/g), rate performance (150 mAh/g at 2 A/g), long‐term cycling performance (1000 cycles at 1 A/g) and coulombic efficiency (~100 %). Considerably higher pseudocapacitance (up to ~78 %) is also identified in this case compared to amorphous carbon particles. Spectroscopic and electrochemical studies proved Na‐ion intercalation in to the disordered carbon and pseudocapacitive storage driven by oxygen‐containing surface functional groups. Outstanding electrochemical performance is credited to the synergy between diffusion limited intercalation and pseudocapacitive surface Na‐ion storage. The demonstrated synthetic method of in situ functionalized carbon nanosheets is inexpensive and scalable. The strategy of functional group and morphology induced pseudocapacitive Na‐ion storage offer new prospects to design high‐performance Na‐ion battery electrodes. [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]

Despite the proposed safety, performance, and cost advantages, practical implementation of Mg−Li hybrid batteries is limited due to the unavailability of reliable cathodes compatible with the dual‐ion system. Herein, a high‐performance Mg−Li dual ion battery based upon cobalt‐doped TiO2 cathode was developed. Extremely pseudocapacitance‐type Ti1‐xCoxO2‐y nanosheets consist of an optimum 3.57 % Co‐atoms. This defective cathode delivered exceptional pseudocapacitance (maximum of 93 %), specific capacities (386 mAh g−1 at 25 mA g−1), rate performance (191 mAh g−1 at 1 A g−1), cyclability (3000 cycles at 1 A g−1), and coulombic efficiency (≈100 %) and fast charging (≈11 min). This performance was superior to the TiO2‐based Mg−Li dual‐ion battery cathodes reported earlier. Mechanistic studies revealed dual‐ion intercalation pseudocapacitance with negligible structural changes. Excellent electrochemical performance of the cation‐doped TiO2 cathode was credited to the rapid pseudocapacitance‐type Mg/Li‐ion diffusion through the disorder generated by lattice distortions and oxygen vacancies. Ultrathin nature, large surface area, 2D morphology, and mesoporosity also contributed as secondary factors facilitating superior electrode‐electrolyte interfacial kinetics. The demonstrated method of pseudocapacitance‐type Mg−Li dual‐ion intercalation by introducing lattice distortions/oxygen vacancies through selective doping can be utilized for the development of several other potential electrodes for high‐performance Mg−Li dual‐ion batteries. [ABSTRACT FROM AUTHOR]

Although lithium-sulfur (Li-S) batteries are one of the promising candidates for nextgeneration energy storage, their practical implementation is limited by rapid capacity fading due to lithium polysulfide (LiPSs) formation and the low electronic conductivity of sulfur. Herein, we report a high-performance lithium-sulfur battery based on multidimensional cathode architecture consisting of nanosulfur, graphene nanoplatelets (2D) and multiwalled carbon nanotubes (1D). The ultrasonic synthesis method results in the generation of sulfur nanoparticles and their intercalation into the multilayered graphene nanoplatelets. The optimized multidimensional graphene-sulfur-CNT hybrid cathode (GNS58-CNT10) demonstrated a high specific capacity (1067 mAh g-1 @ 50 mA g-1), rate performance (539 @ 1 A g-1), coulombic efficiency (~95%) and cycling stability (726 mAh g-1 after 100 cycles @ 200 mA g-1) compared to the reference cathode. Superior electrochemical performances are credited to the encapsulation of nanosulfur between the individual layers of graphene nanoplatelets with high electronic conductivity, and effective polysulfide trapping byMWCNT bundles. [ABSTRACT FROM AUTHOR]

High-performance anodes for rechargeable Li-ion batteries are produced by nanostructuring of transition metal oxides on a conductive support. Here, we demonstrate a hybrid material of MnO2 directly grown onto fabrics of carbon nanotube fibres, which exhibits notable specific capacities over 1100 and 500 mA h g−1 at discharge current densities of 25 mA g−1 and 5 A g−1, respectively, with a coulombic efficiency of 97.5%. Combined with 97% capacity retention after 1500 cycles at a current density of 5 A g−1, both capacity and stability are significantly above literature data. Detailed investigations involving electrochemical and in situ synchrotron X-ray scattering studies reveal that during galvanostatic cycling, MnO2 undergoes an irreversible phase transition to LiMnO2, which stores lithium through an intercalation process, followed by a conversion mechanism and pseudocapacitive processes. This mechanism is further confirmed by Raman spectroscopy and X-ray photoelectron spectroscopy. The fraction of pseudocapacitive charge storage ranges from 27% to 83%, for current densities from 25 mA g−1 to 5 A g−1. The firm attachment of the active material to the built-in current collector makes the electrodes flexible and mechanically robust, and ensures that the low charge transfer resistance and the high electrode surface area remain after irreversible phase transition of the active material and extensive cycling. [ABSTRACT FROM AUTHOR]

Uniform colloidal building-blocks enable the creation of more stable, structurally sophisticated materials. Here we describe a simple polymer-mediated approach to generate grams of monodisperse, single-crystal α-Mn2O3 nanocrystals bound by {111} facets. The technique is inspired in part by biomineralization, where organisms use macromolecular matrices or compartments to trigger the oriented nucleation and growth of crystalline phases. Polyvinylpyrrolidone (PVP) behaves as a polymeric nano-reactor by coordinating to the manganese (Mn) precursor while recruiting the NOx oxidizing agent from solution to drive the co-precipitation of the manganese oxide. PVP also serves as a molecular template to guide the nucleation of trigonal bipyramids composed of Mn3O4. The porosity of the Mn3O4 particles indicates that they form non-classically via oriented attachment instead of atom-by-atom. The particles are further oxidized and transform into single-crystal α-Mn2O3 octahedra. This co-precipitation approach is advantageous because it can generate large amounts of monodisperse nanocrystals at low economic cost. α-Mn2O3 is an alternative lithium ion battery (LIB) anode material that is earth abundant and has ∼2.7 times higher capacity than conventional graphite anodes. We assembled the monodisperse α-Mn2O3 octahedra into LIB anodes to examine their performance in a realistic device. The α-Mn2O3 octahedra exhibit good rate performance, cycling stability, coulombic efficiency and morphology retention during extended lithiation–delithiation cycles compared to previous reports for this material. We attribute the improved electrochemical performance of the α-Mn2O3 octahedra to the lack of agglomeration in the uniformly distributed electrode and improved lithiation of single crystalline α-Mn2O3 nanoparticles. [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]

Amorphous and turbostratic porous carbon spheres are synthesized through a template-free spray pyrolysis method. Anodes composed of these non-graphitic carbon spheres outperformed the commercial graphitic carbon anodes in rechargeable Li-ion batteries. A discharge capacity of 378 mA h g−1, which is equivalent to the theoretical limit of 372 mA h g−1, is achieved at a current density of 0.1 C (37.2 mA g−1). At a higher charge–discharge rate of 1 C, electrochemically most active turbostratic carbon spheres exhibited a reversible specific capacity of 270 mA h g−1, which is 4-fold higher compared to those of commercial graphitic carbon anodes. After 100 charge–discharge cycles at current densities of 0.1 C and 1 C, carbon spheres retained stable specific capacities of 365 and 250 mA h g−1, respectively. Spectroscopic and microscopic investigation of porous carbon anodes after 100 galvanostatic cycles illustrated an excellent structural stability of turbostratic carbon spheres during the lithiation–delithiation process. The notably higher electrochemical performance of carbon spheres is explained by their disordered crystal structure and porosity, which resulted in lower impedance and superior rate performance. This study demonstrates porous turbostratic carbon spheres having a higher charge potential and sloping profile as promising anodes for rechargeable Li-ion batteries. [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]

A new method was developed to synthesize nanosheet-assembled TiO2–B microflowers for Li-ion batteries. Significantly higher electrochemical performance of these microflowers compared to other TiO2–B nanostructures was attributed to their hierarchical microstructure and exposed (1 1̅ 0) facets of the individual nanosheets. [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]

A lithium–sulfur (Li–S) battery is one of the post‐lithium‐ion battery chemistry candidates due to the high theoretical capacity of the sulfur cathode (1672 mAh g−1). However, low electronic conductivity of sulfur and severe capacity fading during the charge–discharge process limit the commercial realization of Li–S batteries. The origin of capacity fading is mainly due to the polysulfide shuttling effect, resulting from the dissolution of sulfur in the electrolyte solution. Herein, atomic layer deposition (ALD) (6–8 Å thickness) of alumina is presented as a strategy to suppress capacity degradation on the 2D graphene–sulfur hybrid electrode. Low‐temperature ALD prevents sulfur sublimation from the composite electrode. Despite the insulating property of alumina, atomic layer coating maintains good electrical conductivity, thereby yielding lower charge transfer resistance. Alumina‐coated graphene–sulfur hybrid electrodes (AGS) exhibit a high specific capacity of 960 mAh g−1 at a current density of 50 mA g−1 and retain 519 mAh g−1 after 100 galvanostatic cycles. Superior electrochemical performance is credited to the combination of the high electronic conductivity of multilayered graphene platelets and low charge transfer resistance, resulting from effective polysulfide blocking by the atomic scale Al2O3 coating. [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]

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]

Despite the proposed safety, performance, and cost advantages, practical implementation of Mg-Li hybrid batteries is limited due to the unavailability of reliable cathodes compatible with the dual-ion system. Herein, a high-performance Mg-Li dual ion battery based upon cobalt-doped TiO 2 cathode was developed. Extremely pseudocapacitance-type Ti 1-x Co x O 2-y nanosheets consist of an optimum 3.57 % Co-atoms. This defective cathode delivered exceptional pseudocapacitance (maximum of 93 %), specific capacities (386 mAh g -1 at 25 mA g -1 ), rate performance (191 mAh g -1 at 1 A g -1 ), cyclability (3000 cycles at 1 A g -1 ), and coulombic efficiency (≈100 %) and fast charging (≈11 min). This performance was superior to the TiO 2 -based Mg-Li dual-ion battery cathodes reported earlier. Mechanistic studies revealed dual-ion intercalation pseudocapacitance with negligible structural changes. Excellent electrochemical performance of the cation-doped TiO 2 cathode was credited to the rapid pseudocapacitance-type Mg/Li-ion diffusion through the disorder generated by lattice distortions and oxygen vacancies. Ultrathin nature, large surface area, 2D morphology, and mesoporosity also contributed as secondary factors facilitating superior electrode-electrolyte interfacial kinetics. The demonstrated method of pseudocapacitance-type Mg-Li dual-ion intercalation by introducing lattice distortions/oxygen vacancies through selective doping can be utilized for the development of several other potential electrodes for high-performance Mg-Li dual-ion batteries., (© 2022 Wiley-VCH GmbH.)

Sodium-ion hybrid capacitors are known for their high power densities and superior cycle life compared to Na-ion batteries. However, low energy densities (<100 Wh kg -1 ) due to the lack of high-capacity (>150 mAh g -1 ) anodes capable of fast charging are delaying their practical implementation. Herein, we report a high-performance Na-ion hybrid capacitor based on an interface-engineered hierarchical TiO 2 nanosheet anode consisting of bronze (∼15%) and anatase (∼85%) crystallites (∼10 nm). This pseudocapacitive dual-phase anode demonstrated exceptional specific capacity of 289 mAh g -1 at 0.025 A g -1 and excellent rate capability (110 mAh g -1 at 1.0 A g -1 ). The Na-ion hybrid capacitor integrating a dual-phase hierarchical TiO 2 nanosheet anode and an activated carbon cathode exhibited a high energy density of 200 Wh kg -1 (based on the total mass of active materials in both electrodes) and power density of 6191 W kg -1 . These values are in the energy and power density range of Li-ion batteries (100-300 Wh kg -1 ) and supercapacitors (5000-15 000 W kg -1 ), respectively. Furthermore, exceptional capacity retention of 80% is observed after 5000 charge-discharge cycles. Outstanding electrochemical performance of the demonstrated Na-ion hybrid capacitor is credited to the enhanced pseudocapacitive Na-ion intercalation of the two-dimensional TiO 2 anode resulting from nanointerfaces between bronze and anatase crystallites. Mechanistic investigations evidenced Na-ion storage through intercalation pseudocapacitance with minimal structural changes. This approach of nanointerface-induced pseudocapacitance presents great opportunities toward developing advanced electrode materials for next-generation Na-ion hybrid capacitors.

A two-dimensional electrode architecture of ∼25 nm sized Co nanoparticles chemically bonded to ∼100 nm thick amorphous porous carbon nanosheets (Co@PCNS) through interfacial Co-C bonds is reported for the first time. This unique 2D hybrid architecture incorporating multiple Li-ion storage mechanisms exhibited outstanding specific capacity, rate performance, and cycling stabilities compared to nanostructured Co 3 O 4 electrodes and Co-based composites reported earlier. A high discharge capacity of 900 mAh/g is achieved at a charge-discharge rate of 0.1C (50 mA/g). Even at high rates of 8C (4 A/g) and 16C (8 A/g), Co@PCNS demonstrated specific capacities of 620 and 510 mAh/g, respectively. Integrity of interfacial Co-C bonds, Co nanoparticles, and 90% of the initial capacity are preserved after 1000 charge-discharge cycles. Implementation of Co nanoparticles instead of Co 3 O 4 restricted Li 2 O formation during the charge-discharge process. In situ formed Co-C bonds during the pyrolysis steps improve interfacial charge transfer, and eliminate particle agglomeration, identified as the key factors responsible for the exceptional electrochemical performance of Co@PCNS. Moreover, the nanoporous microstructure and 2D morphology of carbon nanosheets facilitate superior contact with the electrolyte solution and improved strain relaxation. This study summarizes design principles for fabricating high-performance transition-metal-based Li-ion battery hybrid anodes.

Fluorocarbon (C x F y ) anode materials were developed for lithium- and sodium-ion batteries through a facile one-step carbonization of a single precursor, polyvinylidene fluoride (PVDF). Interconnected carbon network structures were produced with doped fluorine in high-temperature carbonization at 500-800 °C. The fluorocarbon anodes derived from the PVDF precursor showed higher reversible discharge capacities of 735 mAh g -1 and 269 mAh g -1 in lithium- and sodium-ion batteries, respectively, compared to the commercial graphitic carbon. After 100 charge/discharge cycles, the fluorocarbon showed retentions of 91.3% and 97.5% in lithium (at 1C) and sodium (at 200 mA g -1 ) intercalation systems, respectively. The effects of carbonization temperature on the electrochemical properties of alkali metal ion storage were thoroughly investigated and documented. The specific capacities in lithium- and sodium-ion batteries were dependent on the fluorine content, indicating that the highly electronegative fluorine facilitates the insertion/extraction of lithium and sodium ions in rechargeable batteries.

The conversion of allergic pollen grains into carbon microstructures was carried out through a facile, one-step, solid-state pyrolysis process in an inert atmosphere. The as-prepared carbonaceous particles were further air activated at 300 °C and then evaluated as lithium ion battery anodes at room (25 °C) and elevated (50 °C) temperatures. The distinct morphologies of bee pollens and cattail pollens are resembled on the final architecture of produced carbons. Scanning Electron Microscopy images shows that activated bee pollen carbon (ABP) is comprised of spiky, brain-like, and tiny spheres; while activated cattail pollen carbon (ACP) resembles deflated spheres. Structural analysis through X-ray diffraction and Raman spectroscopy confirmed their amorphous nature. X-ray photoelectron spectroscopy analysis of ABP and ACP confirmed that both samples contain high levels of oxygen and small amount of nitrogen contents. At C/10 rate, ACP electrode delivered high specific lithium storage reversible capacities (590 mAh/g at 50 °C and 382 mAh/g at 25 °C) and also exhibited excellent high rate capabilities. Through electrochemical impedance spectroscopy studies, improved performance of ACP is attributed to its lower charge transfer resistance than ABP. Current studies demonstrate that morphologically distinct renewable pollens could produce carbon architectures for anode applications in energy storage devices.

Ultrasmooth submicrometer carbon spheres are demonstrated as an efficient additive for improving the tribological performance of lubricating oils. Carbon spheres with ultrasmooth surfaces are fabricated by ultrasound assisted polymerization of resorcinol and formaldehyde followed by controlled heat treatment. The tribological behavior of the new lubricant mixture is investigated in the boundary and mixed lubrication regimes using a pin-on-disk apparatus and cylinder-on-disk tribometer, respectively. The new lubricant composition containing 3 wt % carbon spheres suspended in a reference SAE 5W30 engine oil exhibited a substantial reduction in friction and wear (10-25%) compared to the neat oil, without change in the viscosity. Microscopic and spectroscopic investigation of the carbon spheres after the tribological experiments illustrated their excellent mechanical and chemical stability. The significantly better tribological performance of the hybrid lubricant is attributed to the perfectly spherical shape and ultrasmooth surface of carbon sphere additive filling the gap between surfaces and acting as a nanoscale ball bearing.

Although Li-ion batteries have attracted significant interest due to their higher energy density, lack of high rate performance electrode materials and intrinsic safety issues challenge their commercial applications. Herein, we demonstrate a simple photocatalytic reduction method that simultaneously reduces graphene oxide (GO) and anchors (010)-faceted mesoporous bronze-phase titania (TiO2-B) nanosheets to reduced graphene oxide (RGO) through Ti(3+)-C bonds. Formation of Ti(3+)-C bonds during the photocatalytic reduction process was identified using electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS) techniques. When cycled between 1-3 V (vs Li(+/0)), these chemically bonded TiO2-B/RGO hybrid nanostructures show significantly higher Li-ion storage capacities and rate capability compared to bare TiO2-B nanosheets and a physically mixed TiO2-B/RGO composite. In addition, 80% of the initial specific (gravimetric) capacity was retained even after 1000 charge-discharge cycles at a high rate of 40C. The improved electrochemical performance of TiO2-B/RGO nanoarchitectures is attributed to the presence of exposed (010) facets, mesoporosity, and efficient interfacial charge transfer between RGO monolayers and TiO2-B nanosheets.

Visible-light-induced antibacterial activity of carbon-doped anatase-brookite titania nano-heterojunction photocatalysts are reported for the first time. These heterostructures were prepared using a novel low temperature (100 °C) nonhydrothermal low power microwave (300 W) assisted method. Formation of interband C 2p states was found to be responsible for the band gap narrowing of the carbon doped heterojunctions. The most active photocatalyst obtained after 60 min of microwave irradiation exhibits a 2-fold higher visible-light induced photocatalytic activity in contrast to the standard commercial photocatalyst Evonik-Degussa P-25. Staphylococcus aureus inactivation rate constant for carbon-doped nano-heterojunctions and the standard photocatalyst was 0.0023 and -0.0081 min(-1), respectively. It is proposed that the photoexcited electrons (from the C 2p level) are effectively transferred from the conduction band of brookite to that of anatase causing efficient electron-hole separation, which is found to be responsible for the superior visible-light induced photocatalytic and antibacterial activities of carbon-doped anatase-brookite nano-heterojunctions.

Polyether solvents are considered interesting and important candidates for Li-O2 battery systems. Discharge of Li-O2 battery systems forms Li oxides. Their mechanism of formation is complex. The stability of most relevant polar aprotic solvents toward these Li oxides is questionable. Specially high surface area carbon electrodes were developed for the present work. In this study, several spectroscopic tools and in situ measurements using electrochemical quartz crystal microbalance (EQCM) were employed to explore the discharge-charge processes and related side reactions in Li-O2 battery systems containing electrolyte solutions based on triglyme/lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) electrolyte solutions. The systematic mechanism of lithium oxides formation was monitored. A combination of Fourier transform infrared (FTIR), NMR, and matrix-assisted laser desorption/ionization (MALDI) measurements in conjunction with electrochemical studies demonstrated the intrinsic instability and incompatibility of polyether solvents for Li-air batteries.

Magnesium-doped ZnO (ZMO) nanoparticles were synthesized through an oxalate coprecipitation method. Crystallization of ZMO upon thermal decomposition of the oxalate precursors was investigated using differential scanning calorimetry (DSC) and X-ray diffraction (XRD) techniques. XRD studies point toward a significant c-axis compression and reduced crystallite sizes for ZMO samples in contrast to undoped ZnO, which was further confirmed by HRSEM studies. X-ray photoelectron spectroscopy (XPS), UV/vis spectroscopy and photoluminescence (PL) spectroscopy were employed to establish the electronic and optical properties of these nanoparticles. (XPS) studies confirmed the substitution of Zn(2+) by Mg(2+), crystallization of MgO secondary phase, and increased Zn-O bond strengths in Mg-doped ZnO samples. Textural properties of these ZMO samples obtained at various calcination temperatures were superior in comparison to the undoped ZnO. In addition to this, ZMO samples exhibited a blue-shift in the near band edge photoluminescence (PL) emission, decrease of PL intensities and superior sunlight-induced photocatalytic decomposition of methylene blue in contrast to undoped ZnO. The most active photocatalyst 0.1-MgZnO obtained after calcination at 600 °C showed a 2-fold increase in photocatalytic activity compared to the undoped ZnO. Band gap widening, superior textural properties and efficient electron-hole separation were identified as the factors responsible for the enhanced sunlight-driven photocatalytic activities of Mg-doped ZnO nanoparticles.