Application In Lithium-ion Battery Anodes Research Articles

Catalytic Graphitization of Pyrolysis Oil for Anode Application in Lithium-ion Batteries

Graphite demand is increasing rapidly due to the popularity of electric vehicles (EVs) and mobile devices. Lithium-ion batteries (LIBs) are the power source of EVs and mobile devices and the...

Preparation of porous silicon by vacuum sublimation dealloying method

Porous silicon has many potential applications in lithium-ion battery anodes and medical sensors, owing to its high specific capacity and photoluminescence properties. In this work, porous silicon is prepared with vacuum sublimation dealloying method by heating Mg2Si precursor to 750 °C and holding it for 1 h under vacuum. The relationship between pressure and temperature, as well as the characteristics of the longitudinal section of condensation products show that the sublimation process of Mg in Mg2Si precursor can be divided into three stages. The aperture distribution curves of the Brunauer-Emmett-Teller (BET) and Mercury Intrusion Porosimetry (MIP) of porous silicon show that the pore size of mesopores is between 3.1 ± 0.2 and 6.3 ± 0.2 nm, and that of macropores is between 351.6 ± 1 and 2101.7 ± 1 nm. The prepared porous silicon has pores with frost flower shaped and shrub-shaped structures in the interior and polygonal contoured pores on the surface. This paper aims to investigate the reaction mechanism of vacuum sublimation dealloying method and provide a foundation for optimizing the performance of porous silicon in applications such as lithium-ion battery anodes and hydrogen generating materials by studying its unique pore structure.

Activation of 2D MoS2 electrodes induced by high-rate lithiation processes

The energy storage processes of a 2D MoS 2 electrode evolve over cycling from battery (I) to pseudocapacitive (II) and to double layer capacitive (III) processes. Physical activation processes (1 and 2) are at the origin. • 2D MoS 2 nanosheets are synthesized by a scalable liquid-phase exfoliation method. • 2D MoS 2 film electrodes were produced by a scalable spray deposition technique. • Conversion processes of nanostructured 2D MoS 2 electrodes are reversible. • High-rate lithiation processes induced activation of 2D MoS 2 electrodes. • Activation induced a conversion-to-capacitive type electrode transformation. • Activated 2D MoS 2 electrodes have superior cycling stability and rate performance. MoS 2 is a highly promising material for application in lithium-ion battery anodes due to its high theoretical capacity and low cost. However, problems with a fast capacity decay over cycling, especially at the first cycles, and poor rate performance have deterred its practical implementation. Herein, electrodes comprised solely of few-layers 2D MoS 2 nanosheets have been manufactured by scalable liquid-phase exfoliation and spray deposition methods. The long-standing controversy questioning the reversibility of conversion processes of MoS 2 -based electrodes was addressed. Raman studies revealed that, in 2D MoS 2 electrodes, conversion processes are indeed reversible, where nanostructure played a key role. Cycling of the electrodes at high current rates revealed an intriguing phenomenon consisting of a continuously increasing capacity after ca. 100–200 cycles. This phenomenon was comprehensively addressed by a variety of electrochemical and microscopy methods that revealed underlying physical activation mechanisms that involved a range of profound electrode structural changes. Activation mechanisms delivered a capacitive electrode of a superior rate performance and cycling stability, as compared to the corresponding pristine electrodes, and to MoS 2 electrodes previously reported. Herein, we have devised a methodology to overcome the problem of cycling stability of 2D MoS 2 electrodes. Moreover, activation of electrodes constitutes a methodology that could be applied to enhance the energy storage performance of electrodes based on other 2D nanomaterials, or combinations thereof, strategically combining chemistries to engineer electrodes of superior energy storage properties.

Electrochemical characterizations of carbon decorated tin doped lithium titanate for lithium-ion battery anode applications

Lithium titanate (Li4Ti5O12) anode materials are widely popular because of their exceptional structural properties that could offer extremely long life and high current rate with safe operation. In-depth research works have been going on to mitigate the limiting factors like poor conduction and diffusion of lithium titanate for the electrode applications in the lithium-ion battery. Elemental doping and surface coating were found to be promising methods to overcome these challenges and enhance the capacity for widespread application. Herein, ex-situ carbon-coated tin (Sn4+) doped lithium titanate was synthesized via conventional solid-state synthesis. Its electrochemical performances were analyzed and compared with its pristine phase by making half cells with lithium. The results were highly promising as the Li4Sn0.05Ti4.95O12 with 5 wt% carbon coating exhibited significantly reduced cell impedance (Rct = 49.48 Ω), enhanced electrode lithium-ion diffusion coefficient (D = 2.40×10−11 cm2 s−1), and superior specific capacity (Q = 173.1 mAh/g at 0.1 C) over pristine lithium titanate (Rct = 274.2 Ω, D = 2.71×10−12 cm2 s−1, and Q = 145 mAh/g). The cell could also run for 1000 cycles with minimum capacity fade (82 % retention) at a 1 C rate.

A simple way for preparing CoFe2O4-based composite with improved lithium storage

In order to achieve the application of emerging electrode materials in lithium-ion batteries, developing simple preparation process is as important as improving their performance. However, most of the emerging anode materials lack simple preparation methods in spite of high performance. Herein, we demonstrate a simple way to prepare high-performance CoFe2O4-based composite anodes for lithium-ion batteries. This composite (CoFe2O4/CoxFey@C) consists of porous clustered CoFe2O4/CoxFey hybrid nanoparticles coated by a thin carbon. The results indicate that the synergistic effects of the CoxFey nanoparticles, carbon coating and porous structure contribute to good electrochemical kinetics and superior cycling durability of the CoFe2O4/CoxFey@C composite. Consequently, it exhibits outstanding lithium storage performance, revealing 684.6 mA h g−1 at 200 mA g−1 after 250 cycles as well as 518.7 mA h g−1 at 1000 mA g−1 after 800 cycles. Moreover, the CoFe2O4/CoxFey@C composite has longer cyclic lifespan than the most of reported CoFe2O4/C composites besides the simple preparation process and adequate capacities, therefore showing significant advantages in application in lithium-ion battery anodes.

Green molten salt modification of cobalt oxide for lithium ion battery anode application

The clean and low-cost preparation of advanced materials for green energy storage applications is a critical step towards sustainable development. Here, the rapid modification of CoO in molten salt is proposed as a low-cost approach for the scalable preparation of Co-based oxides with enhanced Li-storage performance. The phase evolution of CoO upon molten salt treatment is investigated by X-ray diffraction (XRD), electron microscopy, N2 adsorption–desorption and Raman spectroscopy. The molten salt treatment of CoO under dry and humid Ar atmosphere leads to the formation of dual-phase structured CoO/Co3O4 and Li0.065Co0.935O, respectively. High resolution transmission electron microscopy and fast Fourier transform analysis of samples after Li insertion and extraction process confirm the formation of nanostructured Co-Li2O. The Co phase formed from CoO/Co3O4 and Li0.065Co0.935O is found to have hexagonal close packed (hcp) and face central cubic (fcc) structure, respectively. The Li-storage performances of these materials are correlated to their structural/microstructural characteristics. This article presents a simple, scalable and environmentally-friendly approach for modification of Co-oxide materials for lithium ion battery anode applications.

Efficient fluidization intensification process to fabricate in-situ dispersed (SiO + G)/CNTs composites for high-performance lithium-ion battery anode applications

An efficient fluidization process intensification method was proposed to prepare carbon nanotube (CNT)-enhanced high-performance SiO anodes for lithium-ion batteries. The introduction of graphite particles decreased bonding among SiO particles, inhibiting agglomerate growth and enhancing fluidization. The (SiO+G)/CNTs composites were synthesized by fluidized bed chemical vapor deposition with the CNTs grown in- situ, which ensured uniform dispersion and superior anchoring of the CNTs. The in- situ-grown CNTs and stacked graphite ensured excellent structural stability and conductivity. The synthesized (SiO+G)/CNTs delivered a stable reversible capacity of 466 mAh g−1 after 125 cycles and a capacity of ∼200mAhg−1 at 2Ag−1. The charging results indicated that the 3D network structure comprising CNTs and graphite not only effectively buffered the electrode expansion but also greatly improved mechanical flexibility.

Selective formation of pyridinic-type nitrogen-doped graphene and its application in lithium-ion battery anodes.

We report a high-yield single-step method for synthesizing nitrogen-doped graphene nanostripes (N-GNSPs) with an unprecedentedly high percentage of pyridinic-type doping (>86% of the nitrogen sites), and investigate the performance of the resulting N-GNSPs as a lithium-ion battery (LIB) anode material. The as-grown N-GNSPs are compared with undoped GNSPs using scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), helium ion-beam microscopy (HIM), and electrochemical methods. As an anode material we find that pyridinic-type N-GNSPs perform similarly to undoped GNSPs, suggesting that pyridinic sites alone are not responsible for the enhanced performance of nitrogen-doped graphene observed in previous studies, which contradicts common conjectures. In addition, post-mortem XPS measurements of nitrogen-doped graphene cycled as a lithium-ion battery anode are conducted for the first time, which reveal direct evidence for irreversible chemical changes at the nitrogen sites during cycling. These findings therefore provide new insights into the mechanistic models of doped graphene as LIB anodes, which are important in improving the anode designs for better LIB performance.

Conversion of Ti2AlC to C-K2Ti4O9 via a KOH assisted hydrothermal treatment and its application in lithium-ion battery anodes

Herein, we demonstrate the synthesis and electrochemical performance of MAX phase (Ti2AlC) derived C-K2Ti4O9 nanocomposites by one-step KOH assisted hydrothermal treatment. The MAX phase derived C-K2Ti4O9 nanocomposites was measured around 2 μm × 200 nm (length × wide) in micrometer scale and presented layered-structure obviously. Potassium titanate and disordered carbon are attained during the transition state of Ti2CTx MXene. With the help of intermediate product, the Ti2AlC can be converted to potassium titanate thoroughly. Due to the layered structure of potassium titanate and disordered carbon, the composites exhibit excellent electrochemical properties as anode materials in lithium-ion batteries (LIBs). The C-K2Ti4O9 delivered high reversible capacity of 314 mAh g−1 at 100 mA g−1 and superior rate performance.

Facile, Green, Low-Cost Fabrication of Silicon/Carbon Nanocomposites for Lithium-Ion Battery Anode Applications

Hybrid Si/C materials have attracted huge attentions during the past 20 years. The attempts include core/shell, yolk/shell, nanotubes, nanowires and etc. However, the cost of the synthesis of these materials are high and requires complex methods and sufficient time. Therefore, the researchers switched to micron-size silicon as starting material and tried to fabricate composites of silicon with other conductive materials. It was proven that silicon, with more than 300% volume change during charge/discharge process, and low conductivity, cannot satisfy the needs, individually. Among the conductive materials, graphite (Gr) was the first choice. However, the Si/Gr composites did not deliver significant capacity in the first experiments. Here, we looked at the problem again and proposed a new method to elaborate the capacity of Si/Gr composites. This approach is based on size reduction and uniform mixing of silicon and graphite at first stage, followed by conformal carbon coating and creating empty voids inside the composite at the last step. The obtained results are comparable to previous experiments and the whole synthesis can be done with minimum cost in reasonable time.

Agar templated electrodeposition of binary zinc-cobalt alloy and formation of zinc-cobalt-carbon nanocomposite for application in secondary lithium batteries

Thin layer electrodeposition of binary Zn-Co alloy on Cu substrate is carried out using different concentrations of agar, namely, 0.0029 M, 0.0074 M, and 0.0148 M as a template for application in lithium-ion battery anodes. The concentration of agar highly influences the morphology of the deposited films and the formation of nanoflake structures over their surfaces. The optimal agar templated electrode shows good morphological characteristics with a well-defined nanoflake structure, as confirmed by texture coefficient (Tc) values calculated from X-ray diffraction (XRD) results and by field emission scanning electron microscopy (FE-SEM) images. Zn-Co-C nanocomposite electrodes are prepared by subjecting the electrodeposited materials to a calcination step to decompose the agar into C; the resulting electrode shows the initial specific capacity of 827 mAh g−1 and 92% capacity retention after 100 cycles (vs. 20th discharge capacity) whereas Zn-Co alloy electrode shows 829 mAh g−1, with 62% capacity retention after 100 cycles. The chemical compositions of the electrodeposited films are further confirmed by X-ray photoelectron spectroscopy (XPS). Electrochemical studies including charge–discharge cycles and electrochemical impedance spectroscopy (EIS) provide information regarding the lithiation and delithiation processes, and electrode/electrolyte interactions before and after cycling in the prepared electrodes.

Facile synthesis of symmetric bundle-like Sb2S3 micron-structures and their application in lithium-ion battery anodes.

A novel two-step oxidation-sulfuration route is developed to fabricate the symmetric bundle-like Sb2S3 micron-structure, in which hundreds of one-dimensional Sb2S3 nanowires are tied. As an anode material for lithium-ion batteries, the bundle-like Sb2S3 delivers a discharge capacity of 548 mA h g(-1) after 100 cycles, much higher than the rod-like one.

Few-layer MoS2-anchored graphene aerogel paper for free-standing electrode materials.

To reduce the reliance on polymeric binders, conductive additives, and metallic current collectors during the electrode preparation process, as well as to assess the true performance of lithium ion battery (LIB) anodes, a free-standing electrode has to be meticulously designed. Graphene aerogel is a popular scaffolding material that has been widely used with embedded nanoparticles for application in LIB anodes. However, the current graphene aerogel/nanoparticle composite systems still involve decomposition into powder and the addition of additives during electrode preparation because of the thick aerogel structure. To further enhance the capacity of the system, MoS2 was anchored onto a graphene aerogel paper and the composite was used directly as an LIB anode. The resultant additive-free MoS2/graphene aerogel paper composite exhibited long cyclic performance with 101.1% retention after 700 cycles, which demonstrates the importance of free-standing electrodes in enhancing cyclic stability.

Size-Controlled Synthesis of Copper Oxide Particles on Reduced Graphene Oxide for Lithium-Ion Battery Anode Applications.

Copper oxide/reduced graphene oxide (rGO) hybrids have been successfully synthesized by attaching copper ions onto the functional groups of GO by means of a solution process, which causes precipitation and agglomeration of copper oxides during subsequent thermal reduction of the GO. The resulting copper oxide/rGO hybrid exhibited improved electrochemical performance compared to monolithic CuO, which is presumed to be due to rGO acting as a mechanical support that buffers the volume change in copper oxides that occurs as a result of the conversion reaction during charge/discharge cycling. Furthermore, it was found that the size of the copper oxide particles can be optimized by adjusting the annealing time, with a hybrid annealed for 30 min achieving a reversible capacity of 544 mA h g(-1) and an initial coulombic efficiency of 62.7%.

A dealloying approach to synthesizing micro-sized porous tin (Sn) from immiscible alloy systems for potential lithium-ion battery anode applications

Dealloying is a useful approach to producing micro/nanoporous metallic materials and has been applied to the synthesis of porous noble metals such as Au, Ag, Pt and Pd from various forms of precursor materials (e.g. amorphous, solid solution, or intermetallic compound). This study shows that dealloying can also be used to fabricate porous non-noble metals like tin (Sn) from immiscible Al–Sn alloys of Al80Sn20, Al65Sn35 and Al50Sn50 (in at.% throughout the paper). The as-dealloyed porous Sn samples showed a three-dimensionally continuous porous structure throughout each sample and sufficient mechanical integrity for assembly in lithium ion battery cells as anodes. The average pore size depends on the size of the Al phase in each precursor alloy and falls in the range of 1.58 ± 0.26 to 4.09 ± 0.85 μm with respect to the three precursor alloys used. The resulting porous Sn structures can be controlled through changing the microstructure of the precursor alloy. The as-dealloyed porous Sn anode showed an outstanding initial charging-discharging capacity and a high coulombic efficiency in lithium ion battery performance tests.

SnS2–graphene nanocomposites as anodes of lithium-ion batteries

SnS2–graphene nanocomposites are synthesized by a hydrothermal method, and their application as anodes of lithium-ion batteries has been investigated. SnS2 nanosheets are uniformly coating on the surface of graphene. SnS2–graphene nanocomposites exhibit high cyclability and capacity. The reversible capacity is 766 mAh/g at 0.2C rate and maintains at 570 mAh/g after 30 cycles. Such a high performance can be attributed to high electron and Li-ion conductivity, large surface area, good mechanical flexibility of graphene nanosheets and the synergetic effect between graphene and SnS2 nanostructures. The present results indicate that SnS2–graphene nanocomposites have potential applications in lithium-ion battery anodes.

Uniformly loading NiO nanowalls on graphene and their extremely high capacity and cyclability as anodes of lithium-ion batteries

NiO nanowalls/graphene nanosheets (NiO/GNSs) nanocomposites are synthesized by a hydrothermal method, and their application as anodes of lithium-ion batteries has been investigated. NiO nanowalls were uniformly coated over the surface of graphene. NiO/GNSs nanocomposites exhibit extremely high cyclability and capacity. The reversible capacity is 844.9mAhg−1 at 0.1C rate (10h per half cycle) and fades merely 7.1% after 50 cycles. The present results indicate that NiO/GNS nanocomposites have potential applications in lithium-ion battery anodes.

Facile synthesis of carbon nanotubes supported NiO nanocomposite and its high performance as lithium-ion battery anode

NiO nanocrystals anchored on carbon nanotubes (CNTs) were fabricated via a polyvinylpyrrolidone assisted co-precipitation route. At a current density of 100mAg−1, the composite anode delivers an initial reversible capacity of 962mAhg−1 and retains the capacity to 601mAhg−1 after 50 cycles. In contrast, the reversible capacity of the pure NiO particles faded to 380mAhg−1 immediately and then gradually decreased to 278mAhg−1 after 50 cycles. The significantly improved electrochemical performance of the NiO/CNT nanocomposite is attributed to the formation of conductive networks by CNTs, and large surface areas of NiO nanoparticles grown on CNTs which stabilizes these nanoparticles against agglomeration and reduces the diffusion length for lithium-ions. The present results indicate that NiO/CNT nanocomposite has potential applications in lithium-ion battery anodes.

Structural and electrochemical properties of SnO 2/nanocarbon families as lithium-ion battery anodes

Hybrid SnO 2/nanocarbon families (graphene nanosheets (GNSs), single-wall carbon nanotubes (SWCNTs), multi-wall carbon nanotubes (MWCNTs) and carbon nanospheres (CNSs)) have been synthesized by a similar wet chemical method. SnO 2 nanoparticles are uniformly loaded on the surface of the nanocarbon families. As lithium battery anodes, their electrochemical properties of the reaction of lithium are investigated under the same conditions. To compare between them, SnO 2/GNSs have the largest capacity; SnO 2/GNSs and SnO 2/SWCNTs have high cyclability; and SnO 2/MWCNTs can maintain the capacity at high current density. Such behaviors are ascribed to their surface-to-volume ratio, structure flexibility, ion mobility and electron conductivity. The present results are the bases for their practical applications in lithium-ion battery anodes.

Development of Petroleum-Based Carbon Composite Materials Containing Graphite/silicon Particles and Their Application to Lithium Ion Battery Anodes

ABSTRACT: Herein, a novel preparation method of highly homogeneous carbon-silicon composite materials waspresented. In contrast to conventional solvent evaporation method, a milled silicon-graphite or itsoxidized material were directly reacted with petroleum-derived pitch precursor. After thermal reactionunder high pressure, pitch-graphite-silicon composite was prepared. Carbon-graphite-silicon compositewere prepared by an air-oxidization and following carbonization. From energy dispersive spectroscopy,it was observed that small Si particles were highly embedded within carbon, which was confirmedby disappearance of Si peaks in Raman spectra. Furthermore, X-ray diffraction and Raman spectrarevealed that carbon crystallinity decreased when the strongly oxidized silicon-graphite was added,which was probably due to oxygen-induced cross-linking. From the anode application in lithiumion batteries, carbon-graphite-silicon composite anode displayed a high capacity (565 mAh g − 1 ), agood initial efficiency (68%) and an good cyclability (88% retention at 50 cycles), which wereattributed to the high dispersion of Si particles within cabon. In case of the strongly oxidized silicon-graphite addtion, a decrease of reversible capacity was observed due to its low crystallinity.Keywords : Pitch-graphite-Si composite, Petroleum pitch, Anode in lithium ion batteries