Sn@Ni3Sn4embedded nanocable-like carbon hybrids for stable lithium-ion batteries

Metallic Sn@Ni₃Sn₄embedded nanocable-like carbon hybrids have been successfully prepared by a novel gas-phase process, and exhibit a long cycle life (360 mA h g⁻¹at 1 A g⁻¹after 1500 cycles) in lithium-ion batteries.

Porous nitrogen-doped carbon microspheres derived from microporous polymeric organic frameworks for high performance electric double-layer capacitors

This research presents a simple and efficient method to synthesize porous nitrogen-doped carbon microspheres (PNCM) by the carbonization of microporous poly(terephthalaldehyde-pyrrole) organic frameworks (PtpOF). The common KOH activation process is used to tune the porous texture of the PNCM and produce an activated-PNCM (A-PNCM). The PNCM and A-PNCM with specific surface area of 921 and 1303 m(2)  g(-1) , respectively, are demonstrated as promising candidates for EDLCs. At a current density of 0.5 A g(-1) , the specific capacitances of the PNCM and A-PNCM are 248 and 282 F g(-1) , respectively. At the relatively high current density of 20 A g(-1) , the capacitance remaining is 95 and 154 F g(-1) , respectively. Capacity retention of the A-PNCM is more than 92% after 10000 charge/discharge cycles at a current density of 2 A g(-1) .

A novel hollowed CoO-in-CoSnO₃ nanostructure with enhanced lithium storage capabilities

The search for well-defined porous/hollowed metal oxide nanocomposites for high performance energy storage is promising. Herein, atomic layer deposition (ALD) has been utilized for the construction of a novel hollowed wire-in-tube nanostructure of CoO-in-CoSnO3, for which Co2(OH)2CO3 nanowires are first obtained by a hydrothermal method and then deposited with ALD SnO2. After a proper thermal treatment, a CoO wire-void-CoSnO3 tube was formed with the decomposition of Co2(OH)2CO3 and its simultaneous reaction with the outer SnO2 layer. In this unique wire-in-tube structure, both CoO and CoSnO3 are promising materials for lithium ion battery anodes with high theoretical capacities, and the porous + hollow feature is essential for better electrode/electrolyte contact, shorter ion diffusion path and better structure stability. After a further facile carbon coating, the hollowed wire-in-tube structure delivered an improved capacity of 1162.1 mA h g(-1), which is much higher than that of the bare CoO nanowire. Enhanced rate capability and cycling stability have also been demonstrated with the structure, showing its promising application for the anode material of lithium ion battery. The work also demonstrated an effective way of using ALD SnO2 for electrochemical energy storage that ALD SnO2 plays a key role in the structure formation and also serves as both active material and surface coating.

Multifunctional electroactive heteroatom-doped carbon aerogels

The design and synthesis of highly active, durable, and cheap nanomaterials for various renewable energy storage and conversion applications is extremely desirable but remains challenging. Here, a green and efficient strategy to produce CoOx nanoparticles and surface N-co-doped carbon aerogels (Co-N-CAs) is reported by multicomponent surface self-assembly of commercially melamine sponge (CMS). In the methodology, the CMS simultaneously function as green N precursor for surface N doping and 3D support. The resulting Co-N-CAs exhibit 3D hierarchical, interconnected macro- and bimodal meso-porosity (6.3 nm and <4 nm), high surface area (1383 m(2) g(-1)), and highly dispersed, semi-exposured CoOx nanoparticles (diameter of 12.5 nm). The surface doping of N, semi-exposured configuration of CoOx nanoparticles and the penetrated complementary pores (<4 nm) in the carbon walls provide highly accessibility between electroactive components and electrolytes to improve reactivity. With their tailored architecture, the Co-N-CAs show superior electrocatalytic oxygen reduction (ORR) activities comparable to the commercially Pt/C catalysts, high specific capacitance (433 F g(-1)), excellent lithium storage (938 mAh g(-1)), and outstanding durability, making them very promising for advanced energy conversion and storage. In addition, the presented strategy can be extended to fabricate other metal oxide- and N-co-doped carbon aerogels for diverse energy-related applications.

Facile synthesis of highly porous Ni-Sn intermetallic microcages with excellent electrochemical performance for lithium and sodium storage

Highly porous Ni3Sn2 microcages composed of tiny nanoparticles were synthesized by a facile template-free solvothermal method (based on Ostwald ripening and etching mechanism) for use as anode materials for high-capacity and high-rate-capability Li-ion and Na-ion batteries. The Ni3Sn2 porous microcages exhibit highly stable and substantial discharge capacities of the amount to 700 mA h g(-1) after 400 cycles at 0.2C and 530 mA h g(-1) after 1000 cycles at 1C for Li-ion battery anode. For Na-ions storage performance, a reversible capacity of approximate 270 mA h g(-1) is stably maintained at 1C during the first 300 cycles.

Understanding side reactions in K-O2 batteries for improved cycle life

Superoxide based metal-air (or metal-oxygen) batteries, including potassium and sodium-oxygen batteries, have emerged as promising alternative chemistries in the metal-air battery family because of much improved round-trip efficiencies (>90%). In order to improve the cycle life of these batteries, it is crucial to understand and control the side reactions between the electrodes and the electrolyte. For potassium-oxygen batteries using ether-based electrolytes, the side reactions on the potassium anode have been identified as the main cause of battery failure. The composition of the side products formed on the anode, including some reaction intermediates, have been identified and quantified. Combined experimental studies and density functional theory (DFT) calculations show the side reactions are likely driven by the interaction of potassium with ether molecules and the crossover of oxygen from the cathode. To inhibit these side reactions, the incorporation of a polymeric potassium ion selective membrane (Nafion-K(+)) as a battery separator is demonstrated that significantly improves the battery cycle life. The K-O2 battery with the Nafion-K(+) separator can be discharged and charged for more than 40 cycles without increases in charging overpotential.

Controllable synthesis of yolk-shell-structured metal oxides with seven to ten components for finding materials with superior lithium storage properties

A new concept for discovering multicomponent nanostructured materials with good electrochemical properties is proposed. Yolk-shell-structured transition metal oxide powders with seven to ten components and simple crystal structures are prepared by continuous spray pyrolysis. The multicomponent yolk-shell powders with complex compositions show excellent Li(+) storage properties for lithium ion batteries.

Hierarchical Li1.2 Ni0.2 Mn0.6 O2 nanoplates with exposed {010} planes as high-performance cathode material for lithium-ion batteries

Hierarchical Li1.2 Ni0.2 Mn0.6 O2 nanoplates with exposed {010} planes are designed and synthesized. In combination with the advantages from the hierarchical archi-tecture and the exposed electrochemically active {010} planes of layered materials, this material satisfies both efficient ion and electron transport and thus shows superior rate capability and excellent cycling stability.

MOF-derived porous ZnO/ZnFe₂O₄/C octahedra with hollow interiors for high-rate lithium-ion batteries

Novel porous ZnO/ZnFe2O4/C octahedra with hollow interiors are fabricated by a facile self-sacrificing template method involving the refluxing synthesis of hollow, metal-organic framework octahedra in solution and subsequent thermal annealing in N2 . When evaluated as an anode material for lithium-ion batteries, these porous hollow ZnO/ZnFe2O4/C octahedra exhibit significantly enhanced electrochemical performances with high rate capability, high capacity, and excellent cycling stability.

Synthesis and extreme rate capability of Si-Al-C-N functionalized carbon nanotube spray-on coatings as Li-ion battery electrode

Silicon-based precursor derived glass-ceramics or PDCs have proven to be an attractive alternative anode material for Li ion batteries. Main challenges associated with PDC anodes are their low electrical conductivity, first cycle loss, and meager C-rate performance. Here, we show that thermal conversion of single source aluminum-modified polysilazane on the surfaces of carbon nanotubes (CNTs) results in a robust Si-Al-C-N/CNT shell/core composite that offers extreme C-rate capability as battery electrode. Addition of Al to the molecular network of Si-C-N improved electrical conductivity of Si-C-N by 4 orders of magnitude, while interfacing with CNTs showed 7-fold enhancement. Further, we present a convenient spray-coating technique for PDC composite electrode preparation that eliminates polymeric binder and conductive agent there-by reducing processing steps and eradicating foreign material in the electrode. The Si-Al-C-N/CNT electrode showed stable charge capacity of 577 mAh g(-1) at 100 mA g(-1) and a remarkable 400 mAh g(-1) at 10,000 mA g(-1), which is the highest reported value for a silazane derived glass-ceramic or nanocomposite electrode. Under symmetric cycling conditions, a high charge capacity of ∼350 mA g(-1) at 1600 mA g(-1) was continuously observed for over 1000 cycles.

Carbon-encapsulated pyrite as stable and earth-abundant high energy cathode material for rechargeable lithium batteries

Cathode materials consisting of porous pyrite nano-octahedra encapsulated by uniform carbon nanocages exhibit very high energy density, superior rate capability (reversible capabilities of 439, 340, and 256 mA h g(-1) at 1C, 2.5C, and 5C, respectively) and stable cycling performance (ca. 10% capacity loss after 50 cycles at 0.5C with a capacity retention of 495 mA h g(-1) ).

A promising Na3V2(PO4)3 cathode for use in the construction of high energy batteries

High-energy batteries need significant cathodes which can simultaneously provide large specific capacities and high discharge plateaus. NASICON-structured Na3V2(PO4)3 (NVP) has been utilised as a promising cathode to meet this requirement and be used in the construction of high energy batteries. For a hybrid-ion battery by employing metallic lithium as an anode, NVP exhibits an initial specific capacity of 170 mA h g(-1) in the voltage range of 1.6-4.8 V with a long discharge plateau around 3.7 V. Three Na(2) sites for NVP are found capable to be utilised through the application of a wide voltage window but only two of them are able to undergo ions exchange to produce a NaLi2V2(PO4)3 phase. However, a hybrid-ion migration mechanism is suggested to exist to describe the whole ion transport in which the effects of a Na-ion "barrier" results in a lowered ion diffusion rate and observed specific capacity.

A XANES study of LiVPO4F: a factor analysis approach

Evolving factor analysis (EFA) of X-ray absorption near-edge spectroscopy (XANES) data is shown to be a useful tool to understand the phase relationships and compositional ranges of stability in the LiVPO4F-VPO4F system. EFA was used to calculate the concentration of phases versus state-of-charge in a lithium-ion battery and true XANES spectra. The results of EFA showed that, indeed, three phases were present during cycling of a LiVPO4F∥Li cell: LiVPO4F, LixVPO4F, and VPO4F. In contrast to what was reported by others, the second phase was not a fixed composition with x = 0.67, but, instead, existed over a range of lithium stoichiometry, x = 0.25 to 0.80. EFA results also showed that the reactions leading to these phases are reversible.

Free-standing nitrogen-doped graphene paper as electrodes for high-performance lithium/dissolved polysulfide batteries

Free-standing N-doped graphene papers (NGP), generated by pyrolysis of polydiallyldimethylammonium chloride, were successfully used as binder-free electrodes for the state-of-the-art Li/polysulfide-catholyte batteries. They exhibited high specific capacities of approximately 1000 mA h g(-1) (based on S) after 100 cycles and coulombic efficiencies great than 98%, significantly better than undoped graphene paper (GP). These NGP were characterized with XRD, X-ray photoelectron spectroscopy, thermogravimetric analysis, AFM, electron microscopy, and Raman and impedance spectroscopy before and after cycling. Spectroscopic evidence suggested stronger binding of sulfide to NGP relative to GP, and modelling results from DFT calculation, substantiated with experimental data, indicated that pyrrolic and pyridinic N atoms interacted more strongly with Li polysulfides than quaternary N atoms. Thus, more favorable partition of polysulfides between the electrode and the electrolyte and the corresponding effect on the morphology of the passivation layer were the causes of the beneficial effect of N doping.

Rapid continuous synthesis of spherical reduced graphene ball-nickel oxide composite for lithium ion batteries

In this study, we synthesized a powder consisting of core-shell-structured Ni/NiO nanocluster-decorated graphene (Ni/NiO-graphene) by a simple process for use as an anodic material for lithium-ion batteries. First, a crumpled graphene powder consisting of uniformly distributed Ni nanoclusters was prepared by one-pot spray pyrolysis. This powder was subsequently transformed into the Ni/NiO-graphene composite by annealing at 300°C in air. The Ni/NiO-graphene composite powder exhibited better electrochemical properties than those of the hollow-structured NiO-Ni composite and pure NiO powders. The initial discharge and charge capacities of the Ni/NiO-graphene composite powder were 1156 and 845 mA h g⁻¹, respectively, and the corresponding initial coulombic efficiency was 73%. The discharge capacities of the Ni/NiO-graphene, NiO-Ni, and pure NiO powders after 300 cycles were 863, 647, and 439 mA h g⁻¹, respectively. The high stability of the Ni/NiO-graphene composite powder, attributable to the unique structure of its particles, resulted in it exhibiting long-term cycling stability even at a current density of 1500 mA g⁻¹, as well as good rate performance. The structural stability of the Ni/NiO-graphene composite powder particles during cycling lowered the charge transfer resistance and improved the Li-ion diffusion rate.

Electrochemical properties of cobalt hydroxychloride microspheres as a new anode material for Li-ion batteries

The use of cobalt hydroxychloride [Co2(OH)3Cl] as an anode material for lithium ion batteries (LIBs) is investigated using spherical shape and ultrafine nanocrystals directly formed by spray pyrolysis from spray solution of cobalt chloride salt. Dot-mapping images of the resulting powders reveal a uniform distribution of Co, O, and Cl throughout the powder. The Co2(OH)3Cl powder prepared directly by spray pyrolysis exhibits a high thermal stability at temperatures below 220 °C, as well as having superior electrochemical properties compared with those of the CoCl2(H2O)2 and CoO powders prepared by the same process. The initial discharge capacities of the Co2(OH)3Cl and CoO powders at a constant current density of 1000 mA g(-1) are found to be 1570 and 1142 mA h g(-1), respectively, and their initial Coulombic efficiencies are 72 and 70%. The discharge capacities of the Co2(OH)3Cl and CoO powders after 100 cycles are 955 and 632 mA h g(-1), respectively. The Co2(OH)3Cl powders have a high discharge capacity of 609 mA h g(-1) even after 1000 cycles at a high current density of 5000 mA g(-1).

Woven structured triboelectric nanogenerator for wearable devices

To date, quite a few wearable electronics have entered the market, which are changing the life pattern of consumers. However, the limited lifetime and energy storage capacity have made rechargeable batteries the bottleneck in wearable technology, especially with the increase of number of wearable devices and their large distribution. To solve this problem, we demonstrate a woven-structured triboelectric nanogenerator (W-TENG) using commodity nylon fabric, polyester fabric, and conductive silver fiber fabric. With the advantage of being flexible, washable, breathable, wearable, and able to be triggered by a freestanding triboelectric layer, this W-TENG can move freely without any constraint and is suitable for wearable electronics. To demonstrate the potential applications of the W-TENG, the W-TENG is integrated into shoes, coats, and trousers to harvest different kinds of mechanical energy from human motion. This work presents a new approach in applying triboelectric nanogenerator to wearable devices.

Fabrication of 3D hierarchical MoS₂/polyaniline and MoS₂/C architectures for lithium-ion battery applications

In this work, three-dimensional (3D) hierarchical MoS2/polyaniline (PANI) nanoflowers were successfully fabricated via a simple hydrothermal method. The crystal structure and morphology of the MoS2/PANI nanoflowers were characterized by SEM, TEM, XRD, XPS, and FT-IR spectra, revealing that the nanoflowers were composed of ultrathin nanoplates which consisted of few-layered MoS2 nanosheets with enlarged interlayer distance of the (002) plane and PANI. The excellent electrochemical performance of the 3D hierarchical MoS2/PANI nanoflowers was demonstrated. Further 3D hierarchical MoS2/C nanoflowers can be prepared conveniently by annealing the MoS2/PANI sample in a N2 atmosphere at 500 °C for 4 h. The obtained MoS2/C sample exhibited more excellent electrochemical performance due to its excellent electronic conductivity resulting from the close integration of MoS2 nanosheets with carbon matrix. High reversible capacity of 888.1 mAh g(-1) with the Coulombic efficiency maintained at above 90% from the first cycle were achieved at a current density of 100 mA g(-1). Even at a current density of 1000 mA g(-1), the reversible capacity of the MoS2/C sample could be retained at 511 mAh g(-1). The excellent electrochemical performance of these two samples could be attributed to the combined action of enlarged interlayer distance of the ultrathin MoS2 nanosheets, 3D architectures, hierarchical structures, and conductive material. Thus, these 3D hierarchical nanoflowers are competent as promising anode materials for high-performance lithium-ion batteries.

Surface-enhanced redox chemistry of polysulphides on a metallic and polar host for lithium-sulphur batteries

The lithium-sulphur battery relies on the reversible conversion between sulphur and Li2S and is highly appealing for energy storage owing to its low cost and high energy density. Porous carbons are typically used as sulfur hosts, but they do not adsorb the hydrophilic polysulphide intermediates or adhere well to Li2S, resulting in pronounced capacity fading. Here we report a different strategy based on an inherently polar, high surface area metallic oxide cathode host and show that it mitigates polysulphide dissolution by forming an excellent interface with Li2S. Complementary physical and electrochemical probes demonstrate strong polysulphide/Li2S binding with this 'sulphiphilic' host and provide experimental evidence for surface-mediated redox chemistry. In a lithium-sulphur cell, Ti4O7/S cathodes provide a discharge capacity of 1,070 mAh g(-1) at intermediate rates and a doubling in capacity retention with respect to a typical conductive carbon electrode, at practical sulphur mass fractions up to 70 wt%. Stable cycling performance is demonstrated at high rates over 500 cycles.

Elastic a-silicon nanoparticle backboned graphene hybrid as a self-compacting anode for high-rate lithium ion batteries

Although various Si-based graphene nanocomposites provide enhanced electrochemical performance, these candidates still yield low initial coloumbic efficiency, electrical disconnection, and fracture due to huge volume changes after extended cycles lead to severe capacity fading and increase in internal impedance. Therefore, an innovative structure to solve these problems is needed. In this study, an amorphous (a) silicon nanoparticle backboned graphene nanocomposite (a-SBG) for high-power lithium ion battery anodes was prepared. The a-SBG provides ideal electrode structures-a uniform distribution of amorphous silicon nanoparticle islands (particle size <10 nm) on both sides of graphene sheets-which address the improved kinetics and cycling stability issues of the silicon anodes. a-Si in the composite shows elastic behavior during lithium alloying and dealloying: the pristine particle size is restored after cycling, and the electrode thickness decreases during the cycles as a result of self-compacting. This noble architecture facilitates superior electrochemical performance in Li ion cells, with a specific energy of 468 W h kg(-1) and 288 W h kg(-1) under a specific power of 7 kW kg(-1) and 11 kW kg(-1), respectively.

Encapsulating MWNTs into hollow porous carbon nanotubes: a tube-in-tube carbon nanostructure for high-performance lithium-sulfur batteries

A tube-in-tube carbon nanostructure (TTCN) with multi-walled carbon nanotubes (MWNTs) confined within hollow porous carbon nanotubes is synthesized for Li-S batteries. The structure is designed to enhance the electrical conductivity, hamper the dissolution of lithium polysulfide, and provide large pore volume for sulfur impregnation. As a cathode material for Li-S batteries, the S-TTCN composite with 71 wt% sulfur content delivers high reversible capacity, good cycling performance as well as excellent rate capabilities.

Probing thermally induced decomposition of delithiated Li(1.2-x)Ni(0.15)Mn(0.55)Co(0.1)O2 by in situ high-energy X-ray diffraction

Safety of lithium-ion batteries has been a major barrier to large-scale applications. For better understanding the failure mechanism of battery materials under thermal abuse, the decomposition of a delithiated high energy cathode material, Li1.2-xNi0.15Mn0.55Co0.1O2, in the stainless-steel high pressure capsules was investigated by in situ high energy X-ray diffraction. The data revealed that the thermally induced decomposition of the delithiated transition metal (TM) oxide was strongly influenced by the presence of electrolyte components. When there was no electrolyte, the layered structure for the delithiated TM oxide was changed to a disordered Li1-xM2O4-type spinel, which started at ca. 266 °C. The disordered Li1-xM2O4-type spinel was decomposed to a disordered M3O4-type spinel phase, which started at ca. 327 °C. In the presence of organic solvent, the layered structure was decomposed to a disordered M3O4-type spinel phase, and the onset temperature of the decomposition was ca. 216 °C. When the LiPF6 salt was also present, the onset temperature of the decomposition was changed to ca. 249 °C with the formation of MnF2 phase. The results suggest that a proper optimization of the electrolyte component, that is, the organic solvent and the lithium salt, can alter the decomposition pathway of delithiated cathodes, leading to improved safety of lithium-ion batteries.

A Stable, Magnetic, and Metallic Li3O4 Compound as a Discharge Product in a Li-Air Battery

The Li-air battery with the specific energy exceeding that of a Li ion battery has been aimed as the next-generation battery. The improvement of the performance of the Li-air battery needs a full resolution of the actual discharge products. Li2O2 has been long recognized as the main discharge product, with which, however, there are obvious failures on the understanding of various experimental observations (e.g., magnetism, oxygen K-edge spectrum, etc.) on discharge products. There is a possibility of the existence of other Li-O compounds unknown thus far. Here, a hitherto unknown Li3O4 compound as a discharge product of the Li-air battery was predicted through first-principles swarm structure searching calculations. The new compound has a unique structure featuring the mixture of superoxide O2(-) and peroxide O2(2-), the first such example in the Li-O system. The existence of superoxide O2(-) creates magnetism and hole-doped metallicity. Findings of Li3O4 gave rise to direct explanations of the unresolved experimental magnetism, triple peaks of oxygen K-edge spectra, and the Raman peak at 1125 cm(-1) of the discharge products. Our work enables an opportunity for the performance of capacity, charge overpotential, and round-trip efficiency of the Li-air battery.

Exceptional performance of a high voltage spinel LiNi0.5Mn1.5O4 cathode in all one dimensional architectures with an anatase TiO2 anode by electrospinning

We report for the first time the synthesis and extraordinary performance of a high voltage spinel LiNi(0.5)Mn(1.5)O4 fiber cathode in all one dimensional (1D) architecture. Structural and morphological features are analyzed by various characterization techniques. Li-insertion/extraction properties are evaluated in a half-cell assembly (Li/LiNi(0.5)Mn(1.5)O4) and subsequently in full-cell configuration with an anatase TiO2 fiber anode. In both half- and full-cell assemblies, gelled polyvinylidene fluoride-co-hexafluoropropylene (PVdF-HFP) is used as the separator-cum-electrolyte. All the one dimensional components used for fabricating Li-ion cells are prepared by a simple and scalable electrospinning technique. The full-cell, LiNi(0.5)Mn(1.5)O4/gelled PVdF-HFP/TiO2 delivered the reversible capacity of ∼ 102 mA h g(-1) at 0.1 C rate with an operating potential of ∼ 2.8 V. Excellent rate capability and stable cycling profiles are noted for such a full-cell assembly with a capacity retention of ∼ 86% after 400 cycles.

Radiation induced physicochemical changes in FAP (fluoro alkyl phosphate) based imidazolium ionic liquids and their mechanistic pathways: influence of hydroxyl group functionalization of the cation

Future applications of ionic liquids (ILs) in a variety of areas, especially those having high radiation fields such as the nuclear fuel cycle and in space technology, are under serious consideration nowadays. For such applications to be possible, however, radiation stability of the ILs is an important issue that needs to be addressed. We envisaged that the ultra-hydrophobic, bulky and hydrolytically stable FAP (tris(perfluoroalkyl)trifluorophosphate) anion might shield the radiolytically vulnerable imidazolium cations from degradation and our result shows that these anions indeed enhance their radiolytic stability. However, introduction of a hydroxyl group into the alkyl side chain of the imidazolium moiety resulted in significant changes in the physical properties of the IL with respect to onset temperatures, conductivity and the electrochemical window. Furthermore, a nonlinear trend in absorbance with an increase in radiation dose accompanied by NMR (nuclear magnetic resonance) and mass spectrometry studies clearly demonstrated that the presence of the hydroxyl group promotes various degradation channels. Interestingly, a perturbation of the hydrogen bond between the hydroxyl group (present in the side chain of the cation) and the fluorine atom of the anion (OHF) was evident in the case of irradiated hydroxyl functionalized FAP ILs. Besides, the hydrogen gas yields of the ILs were determined and found to be comparable to those of a radiolytically stable aromatic compound, benzene. Finally, through transient spectroscopic studies we could delineate the mechanism of the radiation induced changes in the physicochemical properties of the non-hydroxyl and hydroxyl containing FAP ILs. We have clearly demonstrated that a simple functionalization of the molecular structure of the FAP based imidazolium ILs might cause marked differences in the reactivity, reaction center and the nature of the radiolytic products, which eventually lead to significant changes in their physicochemical properties.

Additive-free hollow-structured Co3O4 nanoparticle Li-ion battery: the origins of irreversible capacity loss

Origins of the irreversible capacity loss were addressed through probing changes in the electronic and structural properties of hollow-structured Co3O4 nanoparticles (NPs) during lithiation and delithiation using electrochemical Co3O4 transistor devices that function as a Co3O4 Li-ion battery. Additive-free Co3O4 NPs were assembled into a Li-ion battery, allowing us to isolate and explore the effects of the Co and Li2O formation/decomposition conversion reactions on the electrical and structural degradation within Co3O4 NP films. NP films ranging between a single monolayer and multilayered film hundreds of nanometers thick prepared with blade-coating and electrophoretic deposition methods, respectively, were embedded in the transistor devices for in situ conduction measurements as a function of battery cycles. During battery operation, the electronic and structural properties of Co3O4 NP films in the bulk, Co3O4/electrolyte, and Co3O4/current collector interfaces were spatially mapped to address the origin of the initial irreversible capacity loss from the first lithiation process. Further, change in carrier injection/extraction between the current collector and the Co3O4 NPs was explored using a modified electrochemical transistor device with multiple voltage probes along the electrical channel.

Ge/C nanowires as high-capacity and long-life anode materials for Li-ion batteries

Germanium-based materials (Ge and GeOx) have recently demonstrated excellent lithium-ion storage ability and are being considered as the most promising candidates to substitute commercial carbon-based anodes of lithium-ion batteries. Nevertheless, practical implementation of Ge-based materials to lithium-ion batteries is greatly hampered by the poor cyclability that resulted from the huge volume variation during lithiation/delithiation processes. Herein, uniform carbon-encapsulated Ge and GeOx nanowires were synthesized by a one-step controlled pyrolysis of organic-inorganic hybrid GeOx/ethylenediamine (GeOx/EDA) nanowires in H2/Ar and Ar atmospheres, respectively. The as-obtained Ge/C and GeOx/C nanowires possess well-defined 0D-in-1D morphology and homogeneous carbon encapsulation, which exhibit excellent Li storage properties including high specific capacities (approximate 1200 and 1000 mA h g(-1) at 0.2C for Ge/C and GeOx/C, respectively). The Ge/C nanowires, in particular, demonstrate superior rate capability with excellent capacity retention and stability (producing high stable discharge capacities of about 770 mA h g(-1) after 500 cycles at 10C), making them promising candidates for future electrodes for high-power Li-ion batteries. The improved electrochemical performance arises from synergistic effects of 0D-in-1D morphology and uniform carbon coating, which could effectively accommodate the huge volume change of Ge/GeOx during cycling and maintain perfect electrical conductivity throughout the electrode.

Selective formation of carbon-coated, metastable amorphous ZnSnO₃ nanocubes containing mesopores for use as high-capacity lithium-ion battery

Mesoporous and amorphous ZnSnO3 nanocubes of ~37 nm size coated with a thin porous carbon layer have been prepared using monodisperse ZnSn(OH)6 as the active precursor and low-temperature synthesized polydopamine as the carbon precursor. The small single nanocubes cross-link with each other to form a continuous conductive framework and interconnected porous channels with macropores of 74 nm width. Because of its multi-featured nanostructure, this material exhibits greatly enhanced integration of reversible alloying/de-alloying (i.e., transformation of Li(4.4)Sn and LiZn to Sn and Zn) and conversion (i.e., oxidation of Sn and Zn to ZnSnO3) reaction processes with an extremely high capacity of 1060 mA h g(-1) for up to 100 cycles. A high reversible capacity of 650 and 380 mA h g(-1) can also be delivered at rates of 2 and 3 A g(-1), respectively. This excellent electrochemical performance is attributed to the small particle size, well-developed mesoporosity, the amorphous nature of the ZnSnO3 and the continuous conductive framework produced by the interconnected carbon layers.

Co@Co₃O₄ core-shell three-dimensional nano-network for high-performance electrochemical energy storage

An alternative routine is presented by constructing a novel architecture, conductive metal/transition oxide (Co@Co3O4) core-shell three-dimensional nano-network (3DN) by surface oxidating Co 3DN in situ, for high-performance electrochemical capacitors. It is found that the Co@Co3O4 core-shell 3DN consists of petal-like nanosheets with thickness of <10 nm interconnected forming a 3D porous nanostructure, which preserves the original morphology of Co 3DN well. X-ray photoelectron spectroscopy by polishing the specimen layer by layer reveals that the Co@Co3O4 nano-network is core-shell-like structure. In the application of electrochemical capacitors, the electrodes exhibit a high specific capacitance of 1049 F g(-1) at scan rate of 2 mV/s with capacitance retention of ~52.05% (546 F g(-1) at scan rate of 100 mV) and relative high areal mass density of 850 F g(-1) at areal mass of 3.52 mg/cm(2). It is believed that the good electrochemical behaviors mainly originate from its extremely high specific surface area and underneath core-Co "conductive network". The high specific surface area enables more electroactive sites for efficient Faradaic redox reactions and thus enhances ion and electron diffusion. The underneath core-Co "conductive network" enables an ultrafast electron transport.