Photo-Assisted Charge-Discharge Behavior of NMC622 Cathode.

Lithium ion batteries compared to other batteries (such as Ni-Cd, Lead-Acid, and Ni-MH) possess higher energy densities (100 – 150 Wh/kg), higher voltage, and lower maintenance [1]. Hybrid CNTs and graphene nanostructures applied in lithium ion batteries were directly grown by ambient pressure chemical vapor deposition (CVD); methane was introduced to form graphene on copper foils at 950 oC, then Fe catalysts were deposited on graphene/copper foils by e-beam evaporation, and ethylene was next introduced to grow pillar CNTs on graphene/copper foil at 750 oC [2]. To increase the accessibly specific surface area and the stability as well as conductivity between the carbon nanotube bundles as well as the nickel foam, three dimensional few layer graphene/multi-walled carbon nanotube architectures were fabricated on oxygen-plasma treated nickel foam coated with Fe catalysts by e-beam evaporation through a one-step ambient pressure CVD process using a mixture of acetylene and hydrogen [3]. N-doped multiwall carbon nanotubes prepared by a plasma enhanced chemical vapor deposition process contain wall defects through which lithium ions can diffuse so as to occupy a large portion of the interwall space as storage regions and then improve the Li storage capability [4]. N-doped graphene nanosheets prepared by heat treatment (800 oC and 2 h) of graphite oxide under an ammonia atmosphere exhibited a high reversible capacity due to N-doping inducing a large number of defects on the graphene layer as well as forming a disordered carbon structure (further enhancing Li intercalation properties) and enhanced cycling stability, which demonstrated the N-doped graphene nanosheets to be a promising candidate for anode materials of lithium ion batteries [5]. The effects of the electron-deficiency (making the defect graphenes have an electron-accepting tendency) of N-doped (pyridinic, pyrrolic, and graphitic) graphenes on their application in lithium ion batteries were investigated and the pyridinic graphene possessed the best as anode materials of lithium ion batteries, while graphitic graphene would be the weakest of the three defect structures [6]. To simultaneously synthesize carbon nanotubes and graphene on nickel foam without additional catalysts, it is tried to grow using one-step ambient pressure chemical vapor deposition (CVD) at different temperatures (700, 800, and 900 oC). Next, in order to add nitrogen-doped defects to the surface of carbon nanotube/graphene composites, it is modified by RF (radio frequency) nitrogen-plasma at different power levels (50, 100, and 150 W) and time periods (5, 15, and 30 min). Carbon nanotubes and graphene are simultaneously synthesized by CVD at 800 oC. Furthermore, the specific capacity (618.32 mAh/g) reached a maximum at the better nitrogen-plasma treatment conditions (power = 100 W and time = 15 min) due to the highest percentage of the pyridinic defect structure which is the most suitable for Li storage with a high storage capacity [6]. Moreover, it also shows higher electrochemical stability after carbon nanotube/graphene composites being treated by nitrogen-plasma.

Antimony oxychloride/graphene aerogel composite as anode material for sodium and lithium ion batteries

Lithium ion batteries have been popularly used as the rechargeable power sources in consumer electronics due to their high energy storage density since the first commercial lithium ion battery launched by Sony in 1991. Graphite is still commonly used as anode material for commercial Lithium ion batteries due to its low redox potential close to Li+/Li, good cycling stability, low cost, and environmental friendliness.[1] However, the performance of current lithium ion batteries, which use graphite as the anode material, cannot satisfy requirements of fast charge Lithium ion batteries. The volume expansion/contraction of the graphite associated with the lithium insertion and extraction process, which results in loss of inter-particle electronic contract, consequently, lead to poor cycling stability. Another consideration of graphite is their safety caused from lithium dendrite formation due to its low Lithium intercalation potential at about 0 V (vs. Li/Li+). [2] The search for new anode materials for lithium ion batteries has been an important way to satisfy the ever-growing demands for better performance with higher energy/power densities, improved safety and longer cycle life. Recently, Li2MnO3 was investigated as an anode material for lithium ion battery.[3] Li2MnO3 exhibits much higher capacity than conventional carbon-based materials and a very stable cycling performance. In this work, as-prepared Li2MnO3/graphene composite material shows the enhanced reversible specific capacity and the rate performance compared with that of pristine Li2MnO3 . It was found that the conductivity of Li2MnO3/graphene was significantly improved by forming a conductive graphene network throughout the insulating Li2MnO3.

Natural graphite (NG) has been attracted as a promising anode material for lithium ion batteries due to its appropriate charge/discharge profile, high reversible capacity and low cost. However, high irreversible capacity and low capacity retention at first cycle have influenced on its practical use. Although low cost is the main advantage of natural graphite, the material cost of natural graphite should be reduced further in order to be used for electric vehicles (EVs) and energy saving systems (ESS). Generally, pristine natural graphite contains various impurities such as Al, Fe, and Si. For commercial use, pristine natural graphite should be refined since the impurities would have a negative effect on both electrolyte and electrode of lithium ion batteries. The purity grade of natural graphite can be classified based on the purification process. As the requirement for high purity increases, more purification steps are needed, resulting in high manufacturing cost. Therefore, the main issue for the application of natural graphite as an anode active material is to use low-purity natural graphite with purification process as less as possible. In this regard, effect of Fe as impurity on the electrochemical performance of the low-purity natural graphite as anode active material for lithium ion batteries was investigated in this study. Natural graphite powders with 5 wt% Fe (05Fe) and 10 wt% (10Fe) were synthesized by combustion method from the raw materials of Fe(III)(NO3)3 9H2O (Alfa Aesar) and high-purity spherical natural graphite (POSCO CHEMTECH) by calcination at 500 °C in air atmosphere. The morphology of the natural graphite powders was observed by scanning electron microscopy (SEM, JSM-5900, JEOL, Japan). The particle size of each powder was measured by a dynamic light scattering method (ELS 6000 zeta potential and particle size analyzer, Otsuka Electronics, Japan). Powder X-ray diffraction (XRD, MAX-2500, RIGAKU, Japan) analysis was conducted using Cu Kα radiation with a wavelength λ = 1.5406 Å. The crystallite sizes (La and Lc) were calculated on the basis of the d002XRD lines by application of the Scherrer’s equation. The crystallinity of the natural graphite powders was investigated by Raman spectroscopy (LabRAM, Horiba Jobin-Yvon, Japan). The concentrations of impurities in the natural graphite were determined by an inductively coupled plasma atomic emission spectrophotometer (ICP-AES). A working electrode paste was fabricated from a mixture of natural graphite with a binder consisting of carboxymethylcellulose (CMC)/styrene-butadiene rubber (SBR) and carbon black (Super-p) as a conductive agent dissolved in D.I. water. The weight ratio of graphite to binder (CMC:SBR:Super-p=2:2:1) was 95:2:2:1. The prepared paste was coated onto 10㎛ Cu foil by using a doctor blade and then dried under vacuum at 120 °C for 12 h. Electrochemical performance was evaluated using CR2032 coin-type cells with a 20 μm thick Cellgard 2300 porous membrane separator and 1 M LiPF6-EC/DMC (1:1 in volume ratio) electrolyte. Lithium metal foil was used as a counter electrode. All of the samples studied in this work were treated by sphericalization and the sphericalized natural graphite maintained a spherical shape after the calcination process at 500 °C for 4 h. All the samples have both hexagonal and rhombohedral phases which are the typical structure of natural graphite. Fe2O3 peaks (JCPDS card #33-0664) were indexed at 2θ = 33.1°, 35.6°, 62.4°, and 63.9°, respectively. The most of Fe2O3particles were located on a surface of natural graphite, based on the EDX mapping and back-scattered electron (BSE) images. The irreversible capacity during the charge-discharge reactions increased with increasing the Fe content. However, the cycle retention of the 05Fe, 10Fe, and NG are comparable. Therefore, it may be possible to use unrefined natural graphite as an anode active material for lithium-ion rechargeable batteries.

The demand of rechargeable batteries had increased significantly every year during the last decade, driven for the needs associated with technological development (portability, high performance of electronic devices and vehicles). Lithium ion battery is a device of mayor consumption, and it is designed for energy storage and conversion based on intercalation electrodes. Nowadays the efforts are directed to the improvement and replacement of current battery components: anode, cathode (LiCoO2) electrolyte, with materials that have higher efficiency in terms of energy, power, cost, reliability, life time and safety. In recent years there has been significant interest in polyanion-based active materials as safe alternatives for the traditional oxide cathodes. For example, phosphate phases such as LiFePO4 [1], Li3V2(PO4)3, [2], Li2.5V2(PO4)3, [3], LiVOPO4, [4,5] and LiVP2O7[6] have all been proposed. Therefore, the search of new cathode materials is an important task for researchers in materials science. The possibility of using sodium directly in lithium ion cells allows the study of new compositions and structures. In this research work a series of four compounds with formula Na3V2-xAlx(PO4)2F3 (x= 0, 0.02, 0.05, 0.1) were prepared, characterized and applied as cathode materials in lithium ion batteries. These materials were synthesized by sol-gel Pechini method. Aqueous solutions containing appropriate amounts of NH4VO3, NH4H2PO4 and NaF were poured into a mixture of citric acid and ethylene glycol solution. Mixture was then heat treated under reflux at 80°C until gel formation. Fresh samples were heated at 300°C under air to eliminate volatile matter. Resulting powders were grinded and formed into pellets for reaction between 300 to 650°C under nitrogen atmosphere. Thermal stability of materials was evaluated by simultaneous termogravimetric and differential analysis (TGA-DTA). Morphological and microstructural characterization were carried out with field emission scanning electron microscopy (FESEM), textural analysis by N2 physisorption with BET method; chemical composition and crystallographic parameters were determined with Induced coupled plasma – optic emission spectroscopy (ICP-OES), energy dispersive X-ray spectroscopy (EDXS) and X-ray powder diffraction (XRD); the application of materials as cathodes in lithium ion batteries was evaluated through electrochemical charge discharge experiments. Electrodes were prepared using a mixture of each synthesized materials, conductive carbon and PVDF binder. CR2032 coin cells were assembled inside a glove box under Ar atmosphere, using LiPF6electrolyte and Li° as anode. Experiments were performed using a MacPile II by Biologic. Thermal analysis of sol-gel reaction products exhibited an exothermic even between 550 and 750°C attributed to the crystallization of the fluorophosphates. Results from XRD analysis showed that Al doped Na3V2(PO4)2F3 crystalline phase was formed at 650°C for 8h. According to cell parameters Na3V2(PO4)2F3 can incorporate aluminum content up to x=0.1, without the presence of secondary phases or structural transitions. Granular morphology and small particles size of about 40 to 100 nm were observed, this can be attributed to the effect of residual carbon within samples (8% by weight) since this inhibits particle grown and also allows contact among particles, improving electrical conductivity. Materials present average porous size of about 20nm, with surface area of 30m2/g. The sample with x=0.05 of Aluminum content, presents the best textural properties. This material also presents high specific charge/discharge capacity (123/101 mAh/g at a 4.4 V vs Li cell) and good capacity retention (82%), in comparison to the material without doping (128/63 mAh/g and 49% of capacity retention). Aluminum doping of Na3V2(PO4)2F3phase permitted the stabilization of the structure related to cycling processes. These results are promising for future application of the material in lithium and sodium ion batteries. Keywords: Pechini, cathodes, phosphates, lithium ion batteries References [1] A.K. Padhi, K.S. Nanjundaswamy, C. Masquelier, J.B. Goodenough, J. Electrochem. Soc. 144 (1997) 2581. [2] M.Y. Saidi, J. Barker, H. Huang, J.L. Swoyer, G. Adamson, Electrochem. Solid-State Lett. 5 (2002) A149. [3] C. Yin, H. Grondey, P. Strobel, L.F. Nazar, Chem. Mater. 16 (2004) 1456. [4] B.M. Azmi, T. Ishihara, H. Nishiguchi, Yusaku Takita, J. Power Sources 146 (1–2) (2005). [5] J. Gaubicher, T. Le Mercier, Y. Chabre, J. Angenault, M. Quarton, J. Electrochem. Soc. 146 (1999) 4375. [6] J. Barker, R.K.B. Gover, P. Burns, A. Bryan, Electrochem. Solid-State Lett. 8 (9) (2005) 446.

Binary cobalt-iron oxides magnetic nanocomposites embedded porous carbon lawn with inherent [sbnd]N doping as promising electrode material for supercapacitors and Li-ion batteries

The nanostructured Si/graphite composites embedded with the pyrolyzed polyethylene glycol was synthesized from coarse silicon and natural graphite by a facile and cost-effective approach. The Si/C nanocomposite showed the fluffy carbon-coated structure, which was confirmed by the SEM and TEM measurements. The as-obtained Si/C nanocomposite, employed as anode material in lithium-ion batteries, exhibited significantly enhanced rate capability and cycling stability. The improved electrochemical stability of the composite was evaluated by EIS and galvanostatically charge/discharge test. A reversible capacities as high as 85% and 91% of the initial charge capacities, could be maintained for the Si/C nanocomposite electrode after 40 cycles under the high current densities of 500 and 1,000 mA g−1, respectively. The relatively low cost and excellent electrochemical capability of the Si/C nanocomposite would well meet the challenge in rapid charge and discharge for large-size lithium-ion rechargeable batteries.

Biomass carbon micro/nano-structures derived from ramie fibers and corncobs as anode materials for lithium-ion and sodium-ion batteries

Recent progress in MXene-based materials for lithium-ion and lithium-sulphur batteries: A comprehensive review

Review: 154 refs.

Novel powder fabrication technologies provide opportunities to develop high-performance, low-cost cathode materials for rechargeable lithium-ion batteries. Among various energy storage technologies, rechargeable lithium-ion batteries have been considered as effective solution to the increasing need for high-energy density electrochemical power sources. Rechargeable lithium-ion batteries offer energy densities 2–3 times and power densities 5–6 times higher than conventional Ni-Cd and Ni-MH batteries, and as a result, they weigh less and take less space for a given energy delivery. However, the use of lithium-ion batteries in many large applications such as electric vehicles and storage devices for future power grids is hindered by the poor thermal stability, relatively high toxicity, and high cost of lithium cobalt oxide (LiCoO2) powders, which are currently used as the cathode material in commercial lithium-ion batteries. Recently, lithium iron phosphate (LiFePO4) powders have become a favorable cathode material for lithium-ion batteries because of their low cost, high discharge potential (around 3.4 V versus Li/Li+), large specific capacity (170 mAh/g), good thermal stability, and high abundance with the environmentally benign and safe nature. As a result, there is a huge demand for the production of high-performance LiFePO4 powders. However, LiFePO4 also has its own limitation such as low conductivity (∼10−9 S/cm), which results in poor rate capability. This can be addressed by modifying the powder structure using novel fabrication technologies. This paper presents an overview of recent advances in the fabrication of high-performance LiFePO4 powders for lithium-ion batteries. The LiFePO4 powder fabrication methods covered include: solid-state synthesis, mechanochemical activation, carbothermal reduction, microwave heating, hydrothermal synthesis, sol-gel synthesis, spray pyrolysis, co-precipitation, microemulsion drying, and others. The impacts of these fabrication methods on the structure and performance of LiFePO4 powders are discussed. In addition, the improvement of the conductivity of LiFePO4 powders through novel powder technologies is addressed.

Roll-to-roll solvent-free manufactured electrodes for fast-charging batteries

Silicon-carbon composite was prepared by the magnesiothermic reduction of mesoporous silica and subsequent impregnation with a carbon precursor. This was applied for use as an anode material for high-performance lithium-ion batteries. Well-ordered mesoporous silica(SBA-15) was employed as a starting material for the mesoporous silicon, and sucrose was used as a carbon source. It was found that complete removal of by-products (Mg2Si and Mg2SiO4) formed by side reactions of silica and magnesium during the magnesiothermic reduction, was a crucial factor for successful formation of mesoporous silicon. Successful formation of the silicon-carbon composite was well confirmed by appropriate characterization tools (e.g., N2 adsorption-desorption, small-angle X-ray scattering, X-ray diffraction, and thermogravimetric analyses). A lithium-ion battery was fabricated using the prepared silicon-carbon composite as the anode, and lithium foil as the counter-electrode. Electrochemical analysis revealed that the silicon-carbon composite showed better cycling stability than graphite, when used as the anode in the lithium-ion battery. This improvement could be due to the fact that carbon efficiently suppressed the change in volume of the silicon material caused by the charge-discharge cycle. This indicates that silicon-carbon composite, prepared via the magnesiothermic reduction and impregnation methods, could be an efficient anode material for lithium ion batteries.

Nitrogen-doped porous carbon nanosheets were prepared from eucalyptus tree leaves by simply mixing the leaf powders with KHCO3 and subsequent carbonisation. Porous carbon nanosheets with a high specific surface area of 2133 m2 g-1 were obtained and applied as electrode materials for supercapacitors and lithium ion batteries. For supercapacitor applications, the porous carbon nanosheet electrode exhibited a supercapacitance of 372 F g-1 at a current density of 500 mA g-1 in 1 m H2 SO4 aqueous electrolyte and excellent cycling stability over 15 000 cycles. In organic electrolyte, the nanosheet electrode showed a specific capacitance of 71 F g-1 at a current density of 2 Ag-1 and stable cycling performance. When applied as the anode material for lithium ion batteries, the as-prepared porous carbon nanosheets also demonstrated a high specific capacity of 819 mA h g-1 at a current density of 100 mA g-1 , good rate capability, and stable cycling performance. The outstanding electrochemical performances for both supercapacitors and lithium ion batteries are derived from the large specific surface area, porous nanosheet structure and nitrogen doping effects. The strategy developed in this paper provides a novel route to utilise biomass-derived materials for low-cost energy storage systems.

Advancement in mobile electronics is driving progress in lithium ion batteries. Recently, organic electrode materials have emerged as promising candidates for lithium ion batteries due to their high theoretical capacity, ease of synthesis, versatility of structure, and abundance. Polymerization is a strategy used to overcome the issues associated with small organic molecules for charge storage application. The focus of this review is on the most recent progress in the field of polymeric carbonyl materials for lithium ion batteries (LIBs) and sodium ion batteries (SIBs). Advantages of organic electrode materials, device architecture, and charge storage mechanism are discussed. Challenges associated with carbonyl-based electrodes and some recent solutions are outlined. Later, a comparison of theoretical capacity, practical capacity, and cyclic life are presented for different carbonyl systems. Capacity-fading phenomena and structural degradation during charging are discussed where necessary. Some key parameters for the design of flexible batteries are highlighted and an overview of some recent contributions of our group in this field are reported. Finally, some future prospects for researchers in this field are outlined.