Reversible Fe3+/Fe2+ and Ti4+/Ti3+ redox couple in Fe-substituted LiTi2O4 ramsdellite and its electrochemical properties as electrode material in 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.

We have prepared ternary chalcostibite (CuSbS2) blocks by use of a facile one-pot solvothermal method at 180°C in anhydrous ethylenediamine containing copper(I) chloride, antimony trichloride, and powdered sulfur as reactants. Time-dependent experiments were performed to investigate the mechanism of growth and evolution of the morphology of CuSbS2, which was characterized by x-ray powder diffraction and field-emission scanning electron microscopy. The novel ternary CuSbS2 was also investigated as an electrode material for lithium ion batteries. Study of its electrochemical properties revealed a high initial lithium ion storage capacity of 877.6 mAh g−1, indicative of potential as an electrode material for lithium ion batteries. (a) SEM images of CuSbS2 blocks; (b) discharge and charge curves of CuSbS2 electrode between 0.01 and 3.0 V at a current density of 100 mA g−1. The ternary chalcostibite (CuSbS2) blocks were synthesized by use of a one-pot solvothermal method; a large quantity of coral structures was obtained. The novel ternary CuSbS2 was investigated as an electrode material for lithium ion batteries; a high initial lithium ion storage capacity of 877.6 mAh g−1, suggested possible use as a new, high-capacity electrode material for lithium ion batteries.

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

1. Introduction Currently, research on layered and rocksalt Li-rich materials is being actively conducted as a high-capacity positive electrode material for lithium ion batteries, and now it is widely accepted that large capacity originates from oxygen redox reaction.[1] Oxygen redox is proposed to be activated for oxygen ions with a Li-O-Li configuration.[2] It was also reported that oxygen redox is activated for Li-rich manganese spinel-type oxides, i.e., Li[Li x Mn2–x ]O4.[3] Nevertheless, its origin of activation of anionic redox for spinel-type oxides is not known. In this study, LiMg y Ni0.5-y Mn1.5O4, which is solid solution samples between LiNi0.5Mn1.5O4 and LiMg0.5Mn1.5O4, is targeted as positive electrode materials with anionic redox for spinel-type oxides. Mg ions have a high ionic bonding nature with oxygen, and thus better reversibility for anionic redox is anticipated.[1] We report the impact of Mg substitution on reversibility of Ni cationic and O anionic redox in the spinel framework structure, and the possibility of 5 V-class high-voltage electrode materials with excellent capacity retention is discussed. 2. Experimental LiMg y Ni0.5-y Mn1.5O4 (0 ≤ y ≤ 0.5) were synthesized from mixtures of Li2CO3, Mg(OH)2, Ni(OH)2 and Mn2O3 by two-step solid-state reaction at 950 oC for 6 h to 700 °C for 48 h in air atmosphere. Characterization of LiMg y Ni0.5-y Mn1.5O4 were conducted by X-ray diffraction (XRD) and scanning electron microscopy (SEM). For the evaluation of electrochemical properties, composite electrodes consisting of 80 wt% active material, 10 wt% AB, and 10 wt% PVdF, and were casted on aluminum foil. 1.0 M LiPF6 dissolved in ethylene carbonate (EC)/dimethyl carbonate (DMC) (3/7 by volume) solution was used as electrolyte. 3. Results and Discussion XRD patterns of LiMg y Ni0.5-y Mn1.5O4 (0 ≤ y ≤ 0.5) are assigned into the spinel structure with space group of Fd-3m. From SEM images, particle sizes of LiMg y Ni0.5-y Mn1.5O4 are estimated to be ~4 μm. No difference in particle sizes regardless of chemical compositions is observed. Figure 1 compares charge/discharge curves of LiMg y Ni0.5-y Mn1.5O4. After 5 cycles, the non Mg-substituted sample, LiNi0.5Mn1.5O4, delivers 135 mAh g−1 of the discharge capacity in a lithium cell when the cut-off voltage is set to 5.3 V. After 50 cycles test, discharge capacity of LiNi0.5Mn1.5O4 is decreased to 125 mAh g-1. On the other hand, significant improvement of cyclability is evidenced for the partially Mg-substituted samples. No capacity fading and no increase in polarization is observed for LiMg0.06Ni0.44Mn1.5O4 even charge to 5.3 V vs. Li for 50 cycles at a rate of 10 mA g-1. On the basis of these findings, Mg substitution is proposed to be effective to reduce electrolyte decomposition and improve structural stability upon high-voltage exposure. Nevertheless, the further enrichment of Mg ions in the structure results in loss of reversible capacity, and anionic redox seems to be inactive for LiMg0.5Mn1.5O4. From these results, factors affecting electrode performance of high voltage spinel with cationic/anionic redox will be discussed in detail.References(1) N. Yabuuchi, Chem. Rec., 19, 703 (2019).(2) D.-H. Seo, Nature Chem., 8, 692 (2016).(3) E. Iwata et al., and T. Ohzuku, Electrochemistry, 71,1187 (2003). Figure 1

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.

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.

LiNi0.8Mn0.1Co0.1O2 (NMC811) can deliver a high capacity of ∼200 mAh/g with an average discharge potential of ∼3.8 V (vs. Li+/Li), making it a promising positive electrode material for high energy density lithium ion batteries. However, electrochemical tests from half cells and full cells show poor cycling performance when charged to potentials above 4.2 V. The calendar and cycle lifetimes of cells are affected by the structural stability of the active electrode materials as well as the parasitic reactions that occur in lithium ion batteries. In order to explore the major failure mechanisms of the material, half cells (coin cells) with control electrolyte and full cells (pouch cells) with control electrolyte and with selected electrolyte additives were tested over four different potential ranges. Isothermal microcalorimetry was used to explore the parasitic reactions and their potential dependence. In-situ and ex-situ X-ray diffraction and scanning electron microscopy were used to investigate the structural and morphological degradation of the materials over cycling. It was found that the dramatic c-axis change of the active material during charge and discharge may not be the major problem for cells that are cycled to higher potentials. The parasitic reactions that arise from the interactions between the electrolyte and the highly reactive delithiated cathode surface at high potentials are suggested as the main reason for the failure of cells cycled above 4.2 V. It should be possible to further improve the performance of NMC811 at high potentials by modifying the cathode surface and/or identifying and using electrolyte blends which reduce parasitic reactions.

Recently, Prussian blue analogues (PBAs) have been reported to exhibit a low voltage charge/discharge behavior with high capacity (300–545 mAh/g) in lithium-ion secondary batteries (LIBs) [...]

Bimetallic coordination polymer composites: A new choice of electrode materials for lithium ion batteries

Graphene boosted pseudocapacitive lithium storage: A case of G-Fe2O3

Controlled synthesis of Li1.17Ni0.21Mn0.54Co0.08O2 as a cathode material for Li ion batteries

High Rate Li-Ion Batteries with Cation-Disordered Cathodes

Lithium-ion batteries have application in wide range of portable devices like cell phones, portable computers, camcorders, I-pods, peristaltic pumps, heart assist devices, oil and gas pipeline robots, seismic survey sensors, tactical communication radios and thermal imaging equipment, and satellite power sources.1,2 They are now projected to automotive industry for electric vehicles (EV’s) and hybrid electric vehicles.3 The common electrode materials of conventional lithium ion batteries are graphite (anode), and LiCoO2 or LiFePO4 (cathode). They have certain limitations such as low capacities, safety issues and cost which hinder their applications.2 RuO2 plays an important role in the family of metal oxides because of its interesting properties such as metallic conductivity, high chemical and thermal stability, catalytic activities, electrochemical redox properties, and field emitting behavior.4 It is one of the most successful electrode material for supercapacitors because of its wide potential window of highly reversible redox reactions, remarkably high specific capacitance, and a very long cycle life.5 In this material, conversion reaction using nanoparticles is also possible and high capacity of 1130 mAh g-1, corresponds to the storage of 5.6 moles of Li ions per mole of RuO2 and high coulombic efficiency (98%) has been observed.6But the material can withstand up to only three cycles due to a large volume expansion.We have improved the cycle life performance of RuO2 by directly depositing the material on stainless steel current collectors via low pressure chemical vapor deposition. RuO2 nano-architectures were characterized by powder x-ray diffraction and field emission scanning electron microscope. Galvanostatic charge-discharge experiments were performed versus lithium metal in the voltage range 4 - 0.1V. As deposited RuO2 nano-architectures were cycled well over 20 cycles at high capacity beyond the theoretical limit of 806 mAh g-1(Fig. 1). The origin of the extra capacity will be discussed. Acknowledgements:This work was supported by NSF PREM Award Number DMR-0934111 and NSF-EPSCoR Cooperative Agreement No EPS-1003897

New ramsdellites LiTi 2−yV yO 4 (0≤ y≤1): Synthesis, structure, magnetic properties and electrochemical performances as electrode materials for lithium batteries

A unique sandwich-structured C/Ge/graphene composite with germanium nanoparticles trapped between graphene sheets is prepared by a microwave-assisted solvothermal reaction followed by carbon coating and thermal reduction. The graphene sheets are found to be effective in hindering the growth and aggregation of GeO2 nanoparticles. More importantly, the graphene sheets, coupled with the carbon coating, can buffer the volume changes of germanium in electrochemical lithium reactions. The unique sandwich structure features a highly conductive network of carbon, which can improve both the conductivity and the structural stability of the electrode material, and exemplifies a promising strategy for the development of new high performance electrode materials for lithium ion batteries.