Li-ion Storage Performance Research Articles

A three-dimensional TiO2-Graphene architecture with superior Li ion and Na ion storage performance

In this work, a three-dimensional TiO2-graphene composite with large specific surface area is designed by freeze drying. In this architecture, primary TiO2 nanoparticles (less than 10 nm in size) are wrapped with graphene homogeneously, forming spherical secondary particles (≈100 nm), and the spherical TiO2 particles further agglomerate into platelet-like particles with several micrometers in size. The TiO2-graphene composite delivers high de-lithiation and de-sodiation capacities of 312 mAh g−1 and 280 mAh g−1 at 17 mA g−1 as negative electrode materials in lithium and sodium cells, respectively, and excellent cycling performance with negligible capacity loss after 500 cycles at a specific current of 85 mA g−1. When coupled with an activated carbon positive electrode, it demonstrates high capacitance and long cycle life in sodium ion capacitors (81% after 2000 cycles at 1 A g−1) and lithium ion capacitors (95% after 5000 cycles at 1 A g−1). Its superior performance benefits from the designed 3D architecture, which combines the advantages of small primary particle size, a homogeneous carbon coating and an adequate contact area with the liquid electrolyte. The storage mechanisms of the superior TiO2-graphene composite in lithium and sodium cells are investigated by operando X-ray diffraction studies.

Co0.85Se@N-doped reduced graphene oxide hybrid polyhedron-in-polyhedron structure assembled from metal-organic framework with enhanced performance for Li-ion storage

Structure control is widely admitted as a feasible strategy to restrain volume change and enhance electrical conductivity for chalcogenide anode materials. Herein, three-dimensionally hierarchical structure Co0.85Se@N-doped graphene hybrid is well-designed and synthesized by a facile hydrothermal strategy and post-calcination. It is noted that, owing to the nanoscale Kirkendall effect, the Co0.85Se nanograins derived from uniform zeolitic imidazolate framework (ZIF-67) precursor are incorporated into a polyhedron-in-polyhedron structure, which is consisted of in-situ formed amorphous carbon and interconnected pliable graphene nanosheets with enormous N-doping atoms. This unique dual-carbon protecting layers are beneficial to mitigate the volume expansion with high integrity, and facilitate the fast Li/electron transport with improved conductivity simultaneously, thus resulting in the superior Li-storage performance. As expected, the framework-controlled Co0.85Se@N-doped rGO composite demonstrates an outstanding cycling stability (787.7 mA h g−1 after 1000 cycles at 2 A g−1) and remarkable rate capability (400.8 mA h g−1 at ultrahigh rate of 10 A g−1). This work presents an enlightened strategy to design chalcogenide anode with desired nano-/microstructure by structure control and kinetic increase.

Three-Dimensional Carbon Framework Anchored Polyoxometalate as a High-Performance Anode for Lithium-Ion Batteries.

Recently, it has become very important to develop cost-effective anode materials for the large-scale use of lithium-ion batteries (LIBs). Polyoxometalates (POMs) have been considered as one of the most promising alternatives for LIB electrodes owing to their reversible multi-electron-transfer capacity. Herein, Keggin-type [PMo12 O40 ]3- (donated as PMo12 ) clusters are anchored onto a 3D microporous carbon framework derived from ZIF-8 through electrostatic interactions. The PMo12 clusters can be immobilized steadily and uniformly on the carbon framework, which provides enhanced electrical conductivity and high stability. Compared with PMo12 itself, the as-prepared novel 3D Carbon-PMo12 composite displays a significantly improved Li-ion storage performance as an LIB anode, with excellent reversible specific capacity and rate capacity, as well as high cycling performance (discharge capacity of 985 mA h g-1 after 200 cycles), which are superior to other POM-based anode materials reported so far. The high performance of the Carbon-PMo12 composite can be attributed to the 3D conductive network with fast electron transport, high ratio of pseudocapacitive contribution, and evenly distributed PMo12 clusters with reversible 24-electron transfer capacity. This work offers a facile way to explore novel LIB anodes consisting of electroactive molecule clusters.

The effect of strain on the Li-storage performance of V2C and Nb2C: From first-principles study

Upon using 2-dimensional (2D) materials as electrodes for Li-ion batteries, strain will be produced due to mechanical factors and Li-intercalation reactions, which changes the intrinsic Li-ion storage performance of the 2D electrodes. In this paper, we investigate the effect of strain on the Li-storage performance of 2D MXenes V2C and Nb2C from density functional theory calculations. The Li-adsorption energies, Li-ion migration energy barriers at lithiated/delithiated states are calculated under varied external strain conditions ranging from −5% to 5%. It is found that, at low Li-ion adsorption concentration, compressive strain is beneficial for both Li-ion adsorption and diffusion, while at high Li-ion adsorption concentrations Li-ion adsorption becomes not favored on V2C but favored on Nb2C under compressive strain. Tensile strain is in favor of Li-vacancy diffusion at high Li-ion adsorption concentrations.

Tuning particle and phase formation of Sn/carbon nanofibers composite towards stable lithium-ion storage

Sn is an attractive anodic material for lithium-ion batteries. High-temperature reduction is large-scale technique since most elemental Sn exists in the form of oxides. However, it is still a challenge to fabricate high performance Sn-based anodes with well-dispersed Sn nanoparticles in conductive matrix due to low melting point of Sn and tendency of particle agglomeration. Herein, we systematically investigate the influences of reduction conditions on particle and phase formation of Sn/carbon nanofibers (CNF) from electrospun SnO2/polyacrylonitrile. It is shown that the SnO2 can be reduced to Sn with slight aggregation at low temperature of 500 °C in a reducing atmosphere, but the composites possess poor electronic conductivity. As raising temperature, the grain size of Sn increases accordingly leading to sluggish Li+ internal diffusion dynamics. While in an inert atmosphere, the SnO2 cannot be reduced completely at low temperature until 650 °C. By optimal control, the Sn/CNF–N2-700 calcined at 700 °C in N2 atmosphere presents the best electrochemical Li-ion storage performance among these samples, which delivers a reversible capacity of 932.2 mAh g−1 at 100 mA g−1 and stable cycling life with 760.3 mAh g−1 retention after 200 cycles. This study may provide optimization guidance for industrial manufacture of Sn-based materials.

A Redox-Active 2D Metal-Organic Framework for Efficient Lithium Storage with Extraordinary High Capacity.

Metal-organic framework cathodes usually exhibit low capacity and poor electrochemical performance for Li-ion storage owing to intrinsic low conductivity and inferior redox activity. Now a redox-active 2D copper-benzoquinoid (Cu-THQ) MOF has been synthesized by a simple solvothermal method. The abundant porosity and intrinsic redox character endow the 2D Cu-THQ MOF with promising electrochemical activity. Superior performance is achieved as a Li-ion battery cathode with a high reversible capacity (387 mA h g-1 ), large specific energy density (775 Wh kg-1 ), and good cycling stability. The reaction mechanism is unveiled by comprehensive spectroscopic techniques: a three-electron redox reaction per coordination unit and one-electron redox reaction per copper ion mechanism is demonstrated. This elucidatory understanding sheds new light on future rational design of high-performance MOF-based cathode materials for efficient energy storage and conversion.

Towards optimized Li-ion storage performance: Insight on the oxygen species evolution of hard carbon by H2 reduction

With high capacity and good rate performance, hard carbon is a promising anode material for lithium ion batteries. However, they are suffering from low coulombic efficiency and poor cycling stability, due to the residue oxygen functional groups in the as-prepared material. Thus, the mild thermal reduction in H2 atmosphere is employed to further remove the oxygen while maintaining the pristine morphology. However, the chemical evolution of oxygen species in the reduction process, as well as their effect on the lithium ion storage performance is still unclear. In this contribution, the structural evolution of oxygen functional groups from 300 to 700 °C is studied by XPS and TPR-MS, and the mechanism is further proposed combining with DFT calculation. The electrochemical results verify that the adsorption-desorption between Li-ions and quinone/C–O groups is irreversible while the behavior of CO is reversible, which has great effect on the specific capacity, columbic efficiency and cycling stability of LIB. This work will provide chemical fundamental for designing high-performance hard carbon anode materials for advanced batteries.

Enhanced Li Ion Storage Performances of Carbon Black by Introducing Organosulfur Groups on Surface

Enhanced Li Ion Storage Performances of Carbon Black by Introducing Organosulfur Groups on Surface

A Comparative Investigation on Lithium Storage Performance of Carbon Microsphere Originated from Agriculture Bio-waste Materials: Sunflower Stalk and Walnut Shell

With the aggravation of environmental pollution and the reduction of fossil fuels, the need of developing green and environmentally sustainable energy materials is becoming urgent. Novel porous carbon microsphere materials derived from waste biomass sunflower steam and walnut shell were prepared based on acidolysis-hydrothermal method, and the morphology, structure and electrochemical performance of the products were characterized by scanning electron microscope, transmission electron microscopy, Raman, X-ray diffraction measurements, nitrogen adsorption, X-ray photoelectron spectroscopy, galvanostatic charge–discharge, cyclic voltammograms and electrochemical impedance spectroscopy. Different electrochemical performance for Li-ion storage was demonstrated owing to the variation of physical property and electrode interface behavior. As an anode material for lithium-ion batteries, the carbon material derived from walnut shell exhibits higher initial coulombic efficiency, cycling stability and rate performance. It can retain charge capacity of 235.3 mAh g−1 after 50 cycles, which is obviously higher than that of carbon microsphere from sunflower steam, 145.9 mAh g−1, and the capacity retention of walnut shell material is 2.5 times that of sunflower steam. It is believed that the superior electrochemical performance may be attributed to the higher graphitization degree and larger pore path of walnut shell-derived carbon materials with average particle size of 3–5 μm, and higher conductivity of SEI film formed on the surface of electrode, which can enhance the conductivity of bulk material and accelerate the migration of lithium ion through bulk material and electrode/electrolyte interface.

Enhanced Li-ion storage performance of novel tube-in-tube structured nanofibers with hollow metal oxide nanospheres covered with a graphitic carbon layer.

One-dimensional (1D) nanofibers constructed with structurally stable nano-architecture and highly conductive carbon components can be employed to develop enhanced anodic materials for lithium-ion batteries. However, achieving an intricate combination of well-designed 1D-nanostructural materials and conductive carbon components for excellent lithium-ion storage capacity is a key challenge. In this study, novel and unique tube-in-tube structured nanofibers consisting of hollow metal oxide (CoFe2O4) nanospheres covered with a graphitic carbon (GC) layer were feasibly and successfully synthesized. A facile pitch solution infiltration method was applied to provide electrical conductivity in the tube-in-tube structure. Generally, mesophase pitch with liquid characteristics uniformly infiltrates the porous nanocrystals and transforms into graphitic layers around metallic CoFe2 alloys during the reduction process. The oxidation process that follows produces the hollow CoFe2O4 nanosphere by the nanoscale Kirkendall effect and the GC layer by selective decomposition of amorphous carbon layers. Hollow CoFe2O4 nanospheres comprising tube-in-tube structured nanofibers and GC layers are formed by pitch-derived carbon; these have improved structural stability and electrical conductivity resulting in excellent cycling and characteristics. Tube-in-tube structured nanofibers consisting of hollow CoFe2O4@GC nanospheres showed excellent long-cycle performance (682 mA h g-1 for the 1400th cycle at a high current density of 3.0 A g-1) and excellent rate capability (355 mA h g-1) even at an extremely high current density of 50 A g-1.

The conversion reaction mechanism of bimetallic Ni–Fe hydroxycarbonate and its encapsulation in carbon nanospheres for achieving excellent Li-ion storage performance

The search for promising anode materials with optimum compositions for use in lithium ion batteries (LIBs) is still underway.

Reversible, stable Li-ion storage in 2 D single crystal orthorhombic α–MoO3 anodes

Engineering two dimensional (2D) materials at atomic level is a key factor to achieve enhanced electrochemical Li-ion storage properties. This work demonstrates that single crystals of orthorhombic α–MoO3 phase can preferentially grow with a 2D nanoarchitecture via a ball-milling process, followed by heat treatment at elevated temperature. Detailed FE-SEM and TEM micrographs proved the 2D architecture of α–MoO3 nanoparticles and Raman spectroscopy evidenced the active vibration modes that correspond to the orthorhombic α-MoO3 phase. Single crystalline MoO3 belts depicted high intensity of (0 2 0) and (0 4 0) indexed planes indicating a preferential arrangement. As Li-ion host anode, the 2D α–MoO3 nanostructure delivered high reversible specific discharge capacity of ~540 mA h g−1 at 0.2 C-rate with 99.9% coulombic efficiency as well as 63% capacity retention after 200 charge-discharge cycles. An excellent reversible Li-ion storage performance (high capacity, longer cycle life and good rate capability) was attributed to the 2D α–MoO3 arrangement consists of MoO6 octahedron by corner sharing chains.

Coupling Topological Insulator SnSb2 Te4 Nanodots with Highly Doped Graphene for High-Rate Energy Storage.

Topological insulators have spurred worldwide interest, but their advantageous properties have scarcely been explored in terms of electrochemical energy storage, and their high-rate capability and long-term cycling stability still remain a significant challenge to harvest. p-Type topological insulator SnSb2 Te4 nanodots anchoring on few-layered graphene (SnSb2 Te4 /G) are synthesized as a stable anode for high-rate lithium-ion batteries and potassium-ion batteries through a ball-milling method. These SnSb2 Te4 /G composite electrodes show ultralong cycle lifespan (478 mAh g-1 at 1 A g-1 after 1000 cycles) and excellent rate capability (remaining 373 mAh g-1 even at 10 A g-1 ) in Li-ion storage owing to the rapid ion transport accelerated by the PN heterojunction, virtual electron highways provided by the conductive topological surface state, and extraordinary pseudocapacitive contribution, whose excellent phase reversibility is confirmed by synchrotron in situ X-ray powder diffraction. Surprisingly, durable lifespan even at practical levels of mass loading (>10 mg cm-2 ) for Li-ion storage and excellent K-ion storage performance are also observed. This work provides new insights for designing high-rate electrode materials by boosting conductive topological surfaces, atomic doping, and the interface interaction.

A Benign Sol-Gel Route Towards Porous Carbon Coated Sb Nanoparticles: A High-Performance Li-Ion Batteries Anode

Rechargeable batteries have wide applications ranging from portable electronics to hybrid electric vehicles owing to an incessant demand for improved capacity and longer lifetime. Metal-based anodes (Sb, Sn, Si, Ge, etc.) can offer high specific capacity albeit with rapid fade due to inherent volume expansion associated with the active phase impedes their commercialization and rapid growth. In the present work, a novel polymer-derived porous carbon coated antimony nanoparticles (Sb@C) based core-shell architecture is proposed for Li-ion batteries anode, wherein a thin conductive carbon shell over Sb nanoparticles (SbNPs) is developed using polymeric diol-aldehyde reactions via a sol-gel route. The core-shell architecture of Sb@C affords a carbon coating act as a buffer and prevents the structural disintegration of SbNPs during Li-ion alloying/de-alloying reactions while improving the rate capability and capacity fade. The structure and morphology of the as-synthesized Sb@C core/shell architecture were studied by XRD, FESEM, and TEM analyses confirmed the formation of thin carbon coating (~100 nm) on to the SbNPs. Preliminary electrochemical results demonstrate that Sb@C anode can deliver a discharge and charge capacity of ~730 mAhg-1 and ~490 mAhg-1 respectively, at a constant current density of ~100 mAg-1 at first cycle. Electrochemical impedance spectroscopy (EIS) results indicate that Sb@C shows lower charge transfer rate (Rct) and improved Li-ion storage performance than the bare SbNPs. Figure 1

Facilely transforming bulk materials to SnO/pristine graphene 2D-2D heterostructures for stable and fast lithium storage

Two-dimensional (2D) nano-structured tin monoxide (SnO) offers fascinating possibilities as anode material for lithium ion batteries (LIBs). 2D architectures of SnO are highly desirable to access advanced lithium storage properties however their application is impeded by the lack of synthetic method. In this study, we report a scalable synthetic route to facilely deriving SnO/pristine-graphene (p-G) 2D-2D heterostructure from bulk SnO and graphite. A “top-down” synthetic method was found effective in transforming SnO micro-sized particles into nanosheets down to a few nanometers in thickness. Assembled with pristine graphene (p-G), the SnO nanosheets were used to build a SnO/p-G heterostructure that delivers remarkable Li-ion storage performances: reversible capacities of 633.9 mAh g−1 after 100 cycles at 0.05 A g−1, and excellent cycling stabilities (0.027% capacity fade per cycle at 1 A g−1 after 700 cycles) were obtained. In comparison, raw SnO exhibited severe SEI over-growth and continuous capacity decay from the on-set at 0.05 A g−1. The structural advantages of 2D-2D heterostructure were elucidated to understand its exceptional lithium storage properties. This study demonstrates a facile and scalable strategy for producing 2D-2D heterostructures from low-cost bulk materials for LIBs application.

Ferrocene as a Novel Additive to Enhance the Lithium-Ion Storage Capability of SnO2/Graphene Composite

Improving the reversibility of conversion reaction is a promising way to enhance the lithium-ion storage capability of SnO2-based anodes. Herein, we report ferrocene as a novel additive to improve the Li-ion storage performance of the SnO2/graphene (SnO2/G) composite. Through a simple mixing method, ferrocene can be uniformly dispersed into the SnO2/G electrode. It is found that the ferrocene additive can effectively suppress the agglomeration of Sn/SnO2 and retain the nanoscale Sn/Li2O interface. Furthermore, metallic Fe is formed from ferrocene in the discharge process and acts as a catalyst to promote the reversible conversion between Sn/Li2O and SnO2. As a result, the SnO2/G electrode with the addition of 10 wt % ferrocene (10%Fc-SnO2/G) exhibits a superior Li-ion storage performance. It displays a reversible capacity of up to 1084.5 mAh g-1 at 0.1 A g-1 after 150 cycles with a good rate capability (752 mAh g-1 at 1 A g-1). In addition, the 10%Fc-SnO2/G electrode can retain a capacity of 787.2 mAh g-1 at 0.5 A g-1 after 220 cycles. This work demonstrates the promising additive of ferrocene in enhancing the reversible capacity of SnO2-based anodes for lithium-ion batteries.

A Facile Synthesis of MoS2/g-C3N4 Composite as an Anode Material with Improved Lithium Storage Capacity.

The demand for well-designed nanostructured composites with enhanced electrochemical performance for lithium-ion batteries electrode materials has been emerging. In order to improve the electrochemical performance of MoS2-based anode materials, MoS2 nanosheets integrated with g-C3N4 (MoS2/g-C3N4 composite) was synthesized by a facile heating treatment from the precursors of thiourea and sodium molybdate at 550 °C under N2 gas flow. The structure and composition of MoS2/g-C3N4 were confirmed by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, infrared spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis and elemental analysis. The lithium storage capability of the MoS2/g-C3N4 composite was evaluated, indicating high capacity and stable cycling performance at 1 C (A·g−1) with a reversible capacity of 1204 mA·h·g−1 for 200 cycles. This result is believed the role of g-C3N4 as a supporting material to accommodate the volume change and improve charge transport for nanostructured MoS2. Additionally, the contribution of the pseudocapacitive effect was also calculated to further clarify the enhancement in Li-ion storage performance of the composite.

MnO−carbon-reduced graphene oxide composite with superior anode Li-ion storage performances

Manganous oxide (MnO)-based composites have motivated extensive researches as an anode electrode for lithium-ion storage due to the high theoretical capacity. Whereas, low cycling stability is the pivotal problem that retards the application of materials. Herein, a hydrothermal-annealing strategy is exploited to obtain the composite materials. The MnO nanoparticles (5–20 nm) wrapped by carbon shells to form core-shell structure are supported on the surface of reduced graphene oxide (rGO) sheets. The rGO flakes in electrode materials possess higher electrical conductivity, and improve the electro-conductibility and structural stability during charging-discharging process. Used as anode for lithium-ion batteries, the composite exhibits large reversible specific capacity (866 mA h g−1 at 0.2 C after 230 cycles) as well as a good cyclicity with a coulombic efficiency of 96%. The hydrothermal-annealing synthetic pathway opens up possibilities for designing and preparing novel electrode materials of lithium or other metallic ion batteries.

MoO2 and graphene heterostructure as promising flexible anodes for lithium-ion batteries

Two-dimensional van der Waals heterostructures hold great promise to create lithium-ion batteries with large energy density, large power density, and long cycle life. In this work, we investigate the MoO2/graphene heterostructure as anodes for lithium-ion batteries by first principles calculations. It is found that the MoO2/graphene heterostructure possesses enhanced electrical conductivity, high theoretical specific capacity (1411 mAh∙g−1), and small diffusion barriers (77 meV). Meanwhile, the flexibility of graphene eliminates the irreversible deformation of MoO2 during the charge-discharge process. These characteristics render the MoO2/graphene heterostructure a stable and efficient Li ion storage performance.

Germanium Nanoparticle-Dispersed Reduced Graphene Oxide Balls Synthesized by Spray Pyrolysis for Li-Ion Battery Anode

Simple fabrication of a powdered Ge-reduced graphene oxide (Ge-rGO) composite via spray pyrolysis and reduction is introduced herein. Successful incorporation of the rGO nanosheets with Ge hindered the aggregation of Ge and conferred enhanced structural stability to the composite by alleviating the mechanical stress associated with drastic volume changes during repeated cycling. The Li-ion storage performance of Ge-rGO was compared with that of powdered Ge metal. The reversible discharge capacity of Ge-rGO at the 200th cycle was 748 mA h g−1 at a current density of 1.0 A g−1 and Ge-rGO showed a capacity of 375 mA h g−1 even at a high current density of 5.0 A g−1. The excellent performance of Ge-rGO is attributed to the structural robustness, enhanced electrical conductivity, and formation of open channels between the rGO nanosheets, which facilitated electrolyte penetration for improved Li-ion diffusion. Key words: Lithium ion batteries, Germanium, Graphene, Carbon composite, Spray pyrolysis