Capacity Cycling Stability Research Articles

Enhanced Performance of Li-S Batteries By PANI Printing Method

Lithium-sulfur (Li-S) batteries have received considerable attention, since their theoretical energy density (2500Wh kg-1) is ~7 times larger than those of the current LIBs (~387Wh kg-1) utilizing the unparalleled theoretical capacity of sulfur (1,675 mAh g-1). The practical application of Li-S cell is still limited mainly due to the low conductivity of sulfur (~10-30 S cm-1), the volumetric expansion up to 80% during the discharge and the dissolution of polysulfides resulting shuttling effect in the charge-discharge process. In the present investigation, we develop a printing method for enhancing the lithium sulfur batteries. PANI layer coated sulfur electrode was demonstrated by a simple printing method. The role of printed layer is confirmed by in-situ UV/Vs test. The PANI layer avoids the chronic issues previously reported in lithium-sulfur batteries. In particular, the printing method is able to enhance the lithium-sulfur cell and the printed layer plays an important role as an electrolyte-blocking layer, preventing the dissolution of polysulfides. In the printed sulfur electrode, the capacity retention was 96.4% with 99.6% of average Coulombic efficiency (1C cycle), and 105% of the original capacity was still retained with 99.3% of average Coulombic efficiency (0.1C cycle). This effect induces the stable cycling capacity of sulfur electrode. The strategy employed in this work to produce a uniform PANI layer printed onto electrode surface is also applicable to all of other sulfur electrode to develop stable cell that avoid the shuttling effect.

PVP-assisted solvothermal synthesis of LiMn0.8Fe0.2PO4/C nanorods as cathode material for lithium ion batteries

LiMn0.8Fe0.2PO4/C rectangular prism nanorods with a short b-axis are successfully synthesized via solvothermal method by means of the in-situ polymerization of resorcinol–formaldehyde followed with further annealing process. In this process, PVP has significant effect on the nanorod morphology. Physicochemical characterizations and electrochemical measurements results demonstrate that the short b-axis of nanorod can contribute to shortening the lithium ion diffusion distance. Relatively thin and uniform carbon layers can improve the electronic conductivity. Furthermore, LiMn0.8Fe0.2PO4/C nanorod delivers a reversible discharge capacity of 140mAhg−1 at 0.1C, and remarkable rate capability is exhibited with 78.6% capacity retention at a 4C rate. Meanwhile, it shows stable cycling stability and capacity retention of 98.1% is still maintained after 100 cycles at 1C. The excellent electrochemical properties can be attributed to the structure superiority of nanorod.

Advanced Sodium Ion Battery Anode Constructed via Chemical Bonding between Phosphorus, Carbon Nanotube, and Cross-Linked Polymer Binder.

Maintaining structural stability is a great challenge for high-capacity conversion electrodes with large volume change but is necessary for the development of high-energy-density, long-cycling batteries. Here, we report a stable phosphorus anode for sodium ion batteries by the synergistic use of chemically bonded phosphorus-carbon nanotube (P-CNT) hybrid and cross-linked polymer binder. The P-CNT hybrid was synthesized through ball-milling of red phosphorus and carboxylic group functionalized carbon nanotubes. The P-O-C bonds formed in this process help maintain contact between phosphorus and CNTs, leading to a durable hybrid. In addition, cross-linked carboxymethyl cellulose-citric acid binder was used to form a robust electrode. As a result, this anode delivers a stable cycling capacity of 1586.2 mAh/g after 100 cycles, along with high initial Coulombic efficiency of 84.7% and subsequent cycling efficiency of ∼99%. The unique electrode framework through chemical bonding strategy reported here is potentially inspirable for other electrode materials with large volume change in use.

Enhanced lithium-ion storage performance from high aspect ratio Mn3O4 nanowires

Owing to the high-capacity, low-cost, and environmentally friendly, Mn3O4 has attracted more and more interest as a potential anode materials for lithium ion batteries (LIBs). In present work, we describe a facile route to synthesize one-dimensional (1D) Mn3O4 nanowires with high aspect ratio by using hydrothermal method. Such nanowires have potential application in LIBs by virtue of their advantageous structures feature. When applied as anodes materials, Mn3O4 nanowires exhibited a larger initial lithium storage capacity and stable cycling capacity. The good electrochemical performance could be attributed to the unique one dimensional nanostructure.

Self-organized sheaf-like Fe3O4/C hierarchical microrods with superior lithium storage properties.

Functional nanomaterials with three-dimensional hierarchical structures are of high interest for many practical applications including lithium-ion batteries (LIBs). In this work, self-organized sheaf-like Fe3O4/C microrods constructed by porous nanowires have been synthesized by a facile solvothermal method combined with a subsequent annealing treatment. The morphology of the building blocks could be easily tuned by varying the synthesis parameters. When applied as an anode material for LIBs, these sheaf-like Fe3O4/C porous microrods manifest superior electrochemical lithium storage properties in terms of high reversible capacity, stable cycling capacity retention and good rate capability.

Mechanistic and Structural Investigation of LixMnO2 Cathodes during Cycling in Li-Ion Batteries

Increasingly there is demand for clean energy sources and suitable batteries to store this energy. Manganese dioxide and lithiated variants are a promising alternative to conventional Li-ion cathodes due to their cost, abundance, safety and electrochemical performance. Cathodes which operate by a single-phase lithium insertion/extraction process can offer some intrinsic advantages over those with two-phase processes. In this work, in-situ and ex-situ synchrotron X-ray diffraction (XRD) is used to investigate the structural evolution and lithium insertion/extraction mechanism of various LixMnO2 cathodes. Li0.30MnO2 is found to cycle solely with a single-phase mechanism, in contrast to previous literature reports, with only subtle changes in the crystal structure. However, a better cycling discharge capacity is realised through a two-step lithiation synthesis, thermally lithiated Li0.08MnO2 which is then electrochemically lithiated to Li0.33MnO2. After an irreversible two-phase reaction early in the first discharge, this material cycles by a single-phase reaction with good structural reversibility and a stable unoptimised cycling capacity of 120 mAh/g. Comparing cathodes using a combination of in-situ and ex-situ synchrotron XRD data allows us to rationalise cathodic performance with structure and thereby directing research into promising candidates.

Mechanistic and structural investigation of LixMnO2 cathodes during cycling in Li-ion batteries

Increasingly there is demand for clean energy sources and suitable batteries to store this energy. Manganese dioxide and lithiated variants are a promising alternative to conventional Li-ion cathodes due to their cost, abundance, safety and electrochemical performance. Cathodes which operate by a single-phase lithium insertion/extraction process can offer some intrinsic advantages over those with two-phase processes. In this work, in-situ and ex-situ synchrotron X-ray diffraction (XRD) is used to investigate the structural evolution and lithium insertion/extraction mechanism of various LixMnO2 cathodes that have been derived from γ-MnO2. Li0.30MnO2 is found to cycle solely with a single-phase mechanism, in contrast to previous literature reports, with only subtle changes in the crystal structure. However, a better cycling discharge capacity is realised through a two-step lithiation synthesis, thermally lithiated Li0.08MnO2 which is then electrochemically lithiated to Li0.33MnO2. After an irreversible two-phase reaction early in the first discharge, this material cycles by a single-phase reaction with good structural reversibility and a stable unoptimised cycling capacity of 120 mAh/g. Comparing cathodes using a combination of in-situ and ex-situ synchrotron XRD data allows us to rationalise cathodic performance with structure and thereby directing research into promising candidates.

Tailoring Porosity in Carbon Nanospheres for Lithium–Sulfur Battery Cathodes

Porous hollow carbon spheres with different tailored pore structures have been designed as conducting frameworks for lithium-sulfur battery cathode materials that exhibit stable cycling capacity. By deliberately creating shell porosity and utilizing the interior void volume of the carbon spheres, sufficient space for sulfur storage as well as electrolyte pathways is guaranteed. The effect of different approaches to develop shell porosity is examined and compared in this study. The most highly optimized sulfur-porous carbon nanosphere composite, created using pore-formers to tailor shell porosity, exhibits excellent cycling performance and rate capability. Sulfur is primarily confined in 4-5 nm mesopores in the carbon shell and inner lining of the shells, which is beneficial for enhancing charge transfer and accommodating volume expansion of sulfur during redox cycling. Little capacity degradation (∼0.1% /cycle) is observed over 100 cycles for the optimized material.

Carbon Nanosheet Frameworks Derived from Peat Moss as High Performance Sodium Ion Battery Anodes

We demonstrate that peat moss, a wild plant that covers 3% of the earth's surface, serves as an ideal precursor to create sodium ion battery (NIB) anodes with some of the most attractive electrochemical properties ever reported for carbonaceous materials. By inheriting the unique cellular structure of peat moss leaves, the resultant materials are composed of three-dimensional macroporous interconnected networks of carbon nanosheets (as thin as 60 nm). The peat moss tissue is highly cross-linked, being rich in lignin and hemicellulose, suppressing the nucleation of equilibrium graphite even at 1100 °C. Rather, the carbons form highly ordered pseudographitic arrays with substantially larger intergraphene spacing (0.388 nm) than graphite (c/2 = 0.3354 nm). XRD analysis demonstrates that this allows for significant Na intercalation to occur even below 0.2 V vs Na/Na(+). By also incorporating a mild (300 °C) air activation step, we introduce hierarchical micro- and mesoporosity that tremendously improves the high rate performance through facile electrolyte access and further reduced Na ion diffusion distances. The optimized structures (carbonization at 1100 °C + activation) result in a stable cycling capacity of 298 mAh g(-1) (after 10 cycles, 50 mA g(-1)), with ∼150 mAh g(-1) of charge accumulating between 0.1 and 0.001 V with negligible voltage hysteresis in that region, nearly 100% cycling Coulombic efficiency, and superb cycling retention and high rate capacity (255 mAh g(-1) at the 210th cycle, stable capacity of 203 mAh g(-1) at 500 mA g(-1)).

Stable cycling and excess capacity of a nanostructured Sn electrode based on Sn(CH3COO)2 confined within a nanoporous carbon scaffold

A high capacity, electrochemically stable, nanostructured Sn electrode for Li ion battery anodes is described. This electrode utilizes a rigid, electrically conductive, nanoporous carbon aerogel scaffold by incorporating tin acetate, Sn(CH3COO)2, into the scaffold pore volume through melt infusion. Incorporation of the Sn(CH3COO)2 by melt infusion ensures a chemically stable contact with the scaffold. The mechanical rigidity of the pore volume confines the Sn to nanometer dimensions without sintering, leading to stable cycling. Separation of the synthesis of the scaffold from the loading with Sn(CH3COO)2 permits optimized division of the scaffold pore volume for expansion and electrolyte access during reaction with Li. Using this design, an electrode based on an aerogel with a 5 nm mode pore size was cycled over 300 times without degradation. In addition, after subtracting the contribution from the carbon scaffold, the capacity exceeded the theoretical capacity for Sn, due to an oxidation reaction occurring at 1.2 V. This excess capacity may be related to the solid–solid or solid–electrolyte interfaces in the electrode, possibly representing a new reversible Li ion reaction.

A Simple Fabrication of Interconnected CuO Nanotube Electrodes for High‐Performance Lithium‐Ion Batteries

Staying connected: Robust and interconnected CuO nanotube anodes were fabricated by a thermal oxidation process of spin-coated CuO nanowire networks. The CuO electrodes strongly adhered to the stainless steel foils and exhibited a high specific capacity (ca. 635 mAh g(-1)), a stable cycling (capacity retention of >99 % after 50 cycles), and excellent rate capabilities (315 mAh g(-1) at 20 C rate).

Nano‐Structured Phosphorus Composite as High‐Capacity Anode Materials for Lithium Batteries

More than LiP service: The adsorption of red phosphorus into porous carbon provides a composite anode material for lithium-ion batteries. The amorphous nano phosphorus, in the carbon matrix, shows highly reversible lithium storage with high coulombic efficiencies and stable cycling capacity of 750 mAh per gram composite.

Charge/discharge characteristics of sulfurized polyacrylonitrile composite with different sulfur content in carbonate based electrolyte for lithium batteries

The charge/discharge characteristics of sulfurized polyacrylonitrile composite (SPAN) cathodes with different sulfur content in conventional carbonate based electrolyte for rechargeable lithium batteries have been investigated. The good performance of SPAN in the carbonate based electrolyte indicates a material difference between SPAN and elemental sulfur/carbon composite materials. The SPAN with sulfur contents of 33.7%, 42.0% and 46.3% are prepared by control of heating time. The SPAN with sulfur content of 42.0% shows the best electrochemical performance, it can deliver stable cycling capacity over 700mAhg−1, and keep capacity retention over 97% after 80 cycles in the electrolyte of 1M LiPF6/EC+DEC. The average capacity degradation rate is less than 0.03% per cycle excluding the first discharge capacity. Prototype 100mAhLi/SPAN cell is assembled, showing energy density of 437Whkg−1 excluding the weight of package and capacity retention of 90.4% after 30 cycles at 100% depth of discharge. This study demonstrates that the sulfurized polyacrylonitrile composite in the electrolyte of 1M LiPF6/EC+DEC is a promising battery chemistry, which materials are abundant, of low cost and easily available, to fabricate Li/SPAN batteries, paving an alternative avenue to develop high performance lithium batteries for energy storage and vehicular application.

Amorphous Si/SiOx/SiO2 nanocomposites via facile scalable synthesis as anode materials for Li-ion batteries with long cycling life

Novel Si/SiOx/SiO2 nanocomposites were prepared via a facile and scalable wet synthesis. The amorphous structure, nanoscale particle size, and composition of the Si/SiOx/SiO2 material were characterized and its electrochemical performance as an anode for Li-ion batteries was evaluated. The material shows a stable cycling capacity of ∼600 mA h g−1 over 350 cycles with high coulombic efficiency of >99%.

Analysis of the synthesis process of sulphur–poly(acrylonitrile)-based cathode materials for lithium batteries

Li/S batteries have attracted great attention in the last twenty years, as they offer the advantage of high gravimetric energy densities over the current conventional Li-ion systems. Besides elemental sulphur based composites, sulphur–poly(acrylonitrile)-based materials are promising candidates for Li/S batteries. Though the structure of the sulphur–poly(acrylonitrile)-based material is still debated, the effects of the synthesis conditions on the material structure, and thus on the electrochemical performance, are undoubted. Here the synthesis process of sulphur–poly(acrylonitrile)-based material is probed by scanning electron microscopy (SEM), infrared spectroscopy (IR) and ultraviolet visible spectroscopy (UV-vis), and the relationships among the synthesis conditions, material structures, and electrochemical behaviours are clarified. Consequently, the optimized synthesis is determined, by which the prepared sulphur–poly(acrylonitrile)-based material delivers a high initial coulombic efficiency of 85.6%, a high stable cycling capacity of over 795 mA h g−1, and high capacity retention of over 98.1% after 50 cycles.

PVDF-HFP Membrane Prepared via TIPS Process as the Matrix of Gel Electrolyte for Lithium Ion Battery

Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) membranes used as the matrix for the gel electrolyte for a lithium battery were prepared via the thermally induced phase separation (TIPS) process using a diluent mixture of dibutyl phthalate (DBP) and di(2-ethylhexyl) phthalate (DEHP). With the assistance of the phase diagram, the membrane microstructure was controlled by only varying the DBP/DEHP ratio in the diluent mixture. The mechanism for the formation of different membrane microstructures was proposed. The effects of membrane microstructure on the membrane performance and the electrochemical properties of the resulting gel electrolyte were also investigated. In addition, a cycle test of a lithium-ion cell with the gel electrolyte based on the membrane prepared via liquid–liquid phase separation showed stable cycling capacity, thus presenting great promise for the use of this membrane as the gel electrolyte matrix for lithium batteries.

Synthesis and electrochemical evaluation of an amorphous titanium dioxide derived from a solid state precursor

Titanium oxides are an important class of lithium–ion battery electrodes owing to their good capacity and stability within the cell environment. Although most Ti(IV) oxides are poor electronic conductors, new methods developed to synthesize nanometer scale primary particles have achieved the higher rate capability needed for modern commercial applications. In this report, the anionic water stable titanium oxalate anion [TiO(C 2O 4) 2] 2− was isolated in high yield as the insoluble DABCO (1,4-diazabicyclo[2.2.2]octane) salt. Powder X-ray diffraction studies show that the titanium dioxide material isolated after annealing in air is initially amorphous, converts to N-doped anatase above 400 °C, then to rutile above 600 °C. Electrochemical studies indicate that the amorphous titanium dioxide phase within a carbon matrix has a stable cycling capacity of ∼350 mAh g −1. On crystallizing at 400 °C to a carbon-coated anatase the capacity drops to 210 mAh g −1, and finally upon carbon burn-off to 50 mAh g −1. Mixtures of the amorphous titanium dioxide and Li 4Ti 5O 12 showed a similar electrochemical profile and capacity to Li 4Ti 5O 12 but with the addition of a sloping region to the end of the discharge curve that could be advantageous for determining state-of-charge in systems using Li 4Ti 5O 12.

Charge/discharge characteristics of sulfur composite cathode materials in rechargeable lithium batteries

Abstract The charge and discharge characteristics of lithium batteries with sulfur composite cathodes have been investigated. The sulfur composites showed novel electrochemical characteristics. The analysis of the differential capacity indicated that the discharge process showed two voltage plateaus of 2.10 V and 1.88 V, and the charge process also presented two voltage plateaus of 2.22 V and 2.36 V. The overcharge test showed that the composite cannot be charged over 4.0 V, the voltage always stopped at about 3.9 V during charging, indicating that the composite presented the intrinsic safety for the overcharge of lithium batteries. The overcharge can cause serious safety problem for the conventional Li-ion batteries. The overcharge test also showed that the batteries with sulfur composite were destroyed when the upper cut-off voltage was over 3.6 V. However, the composite presented good reversible capacity after it was deep discharged even to 0 V. It showed stable cycleability and high cycling capacity of 1000 mAh g−1 when cycling between 0.1 V and 3.0 V, indicative of the different characteristic from the conventional oxide cathode materials. The prototype polymer battery with the composite cathode material presented the energy density of 246 Wh kg−1 and 401 Wh L−1.

Synthesis of PAN/SnCl2 composite as Li-ion battery anode material

A novel process was proposed to synthesize the pyrolytic polyacrylonitrile (PAN)/SnCl2 composite anode material for Li-ion batteries. The preparation started with the dissolution of PAN and SnCl2 in dimethylformamide (DMF), followed by drying of the solution and pyrolysis of the dried mixture of PAN and SnCl2 at 300 °C, leading to homogenous dispersal of SnCl2 in pyrolytic PAN, which becomes conducting polymer matrix. The composite presented stable cycling capacity of about 490 mAh/g. It is demonstrated that SnCl2, which has been considered to be an inactive electrode material, can become active by the proposed composite technique. This paves the promising way to prepare electrode materials for Li-ion batteries.