Box-Behnken design for the synthesis optimization of mesoporous sulfur-doped carbon-based materials from birch waste: Promising candidates for environmental and energy storage application

The development of biomass-based carbon materials has accelerated the research interest in environmental (e.g., adsorbents for wastewater decontamination) and energy applications (e.g., batteries). In this paper, we developed a series of carbon materials (CMs) using a sulfur doping strategy to improve the physicochemical, adsorptive and energy storage properties of the aforementioned CMs. CMs were prepared and optimized using an experimental design denoted as the Box-Behnken design approach with three independent factors (i.e., the temperature of pyrolysis, zinc chloride: biomass ratio and sulfur: biomass ratio), and the responses were evaluated, namely the Specific Surface Area (SBET), mesopore area (AMeso) and micropore area (AMicro) with the help of Nitrogen Physisorption. According to the statistical analysis, under the studied conditions, the responses were mainly influenced by the pyrolysis temperature and ZnCl2 ratio, while the sulfur content did not give rise to any remarkable differences in the selected responses. The physicochemical characterization of the CMs suggested that very high Specific Surface Areas ranging from 1069 to 1925 m2 g−1 were obtained. The sulfur doping resulted in up to 7.33 wt% of sulfur in the CM structure, which yielded CMs with more defects and hydrophilic surfaces. When tested as adsorbents, CMs exhibited a very high adsorption capacity (190 – 356 mg g−1), and as anodes, they demonstrated a competitive Lithium Ion Battery (LIB) storage capacity, at least during the first five cycles (306 mAhg−1 at 1 C for CM9). However, further studies on long-term cyclability are required to prove the CM materials suitability in LIBs. This work extends our understanding of how pyrolysis and sulfur doping of biomass feedstock affects carbon materials' usability, final characteristics and potential to use in wastewater decontamination by adsorption and as anodes in LIBs

Amorphous Vanadium Oxide Thin Films as Stable Performing Cathodes of Lithium and Sodium-Ion Batteries

Abstract Herein, we report additive- and binder-free pristine amorphous vanadium oxide (a-VOx) for Li- and Na-ion battery application. Thin films of a-VOx with a thickness of about 650 nm are grown onto stainless steel substrate from crystalline V2O5 target using pulsed laser deposition (PLD) technique. Under varying oxygen partial pressure (pO2) environment of 0, 6, 13 and 30 Pa, films bear O/V atomic ratios 0.76, 2.13, 2.25 and 2.0, respectively. The films deposited at 6‑30 Pa have a more atomic percentage of V5+ than that of V4+ with a tendency of later state increased as pO2 rises. Amorphous VOx films obtained at moderate pO2 levels are found superior to other counterparts for cathode application in Li- and Na-ion batteries with reversible capacities as high as 300 and 164 mAh g−1 at 0.1 C current rate, respectively. At the end of the 100th cycle, 90% capacity retention is noticed in both cases. The observed cycling trend suggests that more is the (V5+) stoichiometric nature of a-VOx better is the electrochemistry

Electrospun Fe2O3-carbon composite nanofibers as durable anode materials for lithium ion batteries

Combination of metal oxides and carbon has been a favourable practice for their application in high-rate energy storage mesoscopic electrodes. We report quasi 1D Fe2O3-carbon composite nanofibers obtained by the electrospinning method, and evaluate them as the anode for Li ion storage. In the half-cell configuration, the anode exhibits a reversible capacity of 820 mA h g-1 at a current rate of 0.2C up to 100 cycles. At a higher current density of 5C, the cells still exhibit a specific capacity of 262 mAh g-1. Compared to pure electrospun Fe2O3 nanofibers, the capacity retention of Fe2O3-C composite nanofiber electrode is drastically improved. The good electrochemical performance is associated with the homogenous dispersed Fe2O3 nanocrystals on the carbon nanofiber support. Such structure prevents the aggregation of active materials, maintains the structure integrity and thus enhances the electronic conductivity during lithium insertion and extraction.ASTAR (Agency for Sci., Tech. and Research, S’pore)ASTAR (Agency for Sci., Tech. and Research, S’pore)Accepted versio

Citric acid assisted solid state synthesis of V2O3, V2O3/C and V2O3/graphene composites for Li‐ion battery anode applications

A series of V2O3, V2O3/C and V2O3/G composite powders are prepared by simply annealing the reaction mixture containing ammonium metavanadate (0.1 M), reduced graphene oxide (rGO, 0.1 M) and citric acid (CA, 0.0, 0.1, 0.3 and 0.5 M) at 500 °C for 8 h under Ar flow. A variety of characterization techniques are used to investigate the structural, physiochemical features and electrochemical performance of the powders. The reaction mixture without rGO led to the formation of V2O3 at 0.1 M of CA and V2O3/C at 0.3 and 0.5 M of CA. As anodes of lithium‐ion coin cell batteries, V2O3, V2O3/C and V2O3/G composite electrodes exhibit an increase in capacity with increasing concentrations of CA. The increase in capacity is mainly attributed to the carbonization of CA and the declining crystallinity of V2O3. V2O3/C and V2O3/G prepared at 0.5 M of CA outperformed all other control compounds. The V2O3/C and V2O3/G delivered reversible capacities of 585 and 420 mAh g−1 respectively, during the first cycle with a current density of 50 mA g−1. The respective capacities after few initial cycles continuously increased to 608 and 463 mAh g−1 at the end of the 100th cycle.MOE (Min. of Education, S’pore

An insight into the electrochemical activity of Al-doped V2O3

We design Al-doped V2O3 (AlxV2O3) compounds as cathodes of aluminium battery. A citric acid-assisted simple solid-state synthesis is used to produce AlxV2O3 compounds by heating, at different temperature, a reaction mixture of NH4VO3, Al(NO3)3centerdot9H2O and citric acid under Ar flow. Al-doping in-between layers and at lattice sites of V2O3 is confirmed by structural, vibrational and chemical analyses. The doped compounds obtained at 600 °C and 800 °C are confirmed as Al0.56V2O3 and Al0.53V2O3 corresponding to theoretical capacities 488 and 490 mAh g−1, respectively, for the extraction of doped Al by considering three electron transfer (Al/Al3+). The as-synthesized AlxV2O3 compounds are tested as cathodes in aluminium battery with 1.0 M AlCl3:[EMIM]Cl electrolyte. The electrodes of Al0.56V2O3 and Al0.53V2O3 exhibited the first charge capacity of 415 and 385 mAh g−1, respectively. The electrochemical extraction of doped Al is confirmed by comparisons with bare V2O3 control cathodes and post-cycling structural studies. The extraction of doped Al from AlxV2O3 indicates its promising use in high capacity cathode for Al-ion battery.NRF (Natl Research Foundation, S’pore)Published versio

Graphenothermal reduction synthesis of 'exfoliated graphene oxide/iron (II) oxide' composite for anode application in lithium ion batteries

10.1016/j.jpowsour.2015.05.075Journal of Power Sources293253-26

Synthesis of Nickel Fumarate and Its Electrochemical Properties for Li-Ion Batteries

Metal–organic frameworks (MOFs) have found a potential application in various domains such as gas storage/separation, drug delivery, catalysis, etc. Recently, they have found considerable attention for energy storage applications such as Li- and Na-ion batteries. However, the development of MOFs is plagued by their limited energy density that arises from high molecular weight and low volumetric density. The choice of ligand plays a crucial role in determining the performance of the MOFs. Here, we report a nickel-based one-dimensional metal-organic framework, NiC4H2O4, built from bidentate fumarate ligands for anode application in Li-ion batteries. The material was obtained by a simple chimie douce precipitation method using nickel acetate and fumaric acid. Moreover, a composite material of the MOF with reduced graphene oxide (rGO) was prepared to enhance the lithium storage performance as the rGO can enhance the electronic conductivity. Electrochemical lithium storage in the framework and the effect of rGO on the performance have been investigated by cyclic voltammetry, galvanostatic charge–discharge measurements, and EIS studies. The pristine nickel formate encounters serious capacity fading while the rGO composite offers good cycling stability with high reversible capacities of over 800 mAh g−1

Fe2Mo3O8/exfoliated graphene oxide : solid-state synthesis, characterization and anodic application in Li-ion batteries

An Fe2Mo3O8/exfoliated graphene oxide (EG) composite with unique morphology is synthesized by a novel solid-state reduction method. Graphene oxide (GO), FeC2O4·2H2O and MoO3 are heated together at 750 °C for 8 h under an Ar atmosphere to obtain Fe2Mo3O8/EG as the resultant material. The morphology of the as-synthesized Fe2Mo3O8/EG powder as observed in electron micrographs confirmed the presence of layer-like EG and densely populated Fe2Mo3O8 hexagonal platelets. Thermogravimetric analysis showed that Fe2Mo3O8 and EG are in the composite at 98 and 2 wt%, respectively. The structural analysis of the as-synthesized Fe2Mo3O8/EG confirmed that Fe2Mo3O8 platelets are crystallized in the hcp crystal system. Raman scattering analysis further confirmed the presence of Fe2Mo3O8 and EG in the as-synthesized Fe2Mo3O8/EG composite. X-ray photoelectron spectroscopy confirmed that Fe and Mo elements are in the II and IV oxidation states in the as-synthesized Fe2Mo3O8/EG composite, which when tested as an anode material of a half-cell Li-ion battery, exhibited a high reversible capacity of 945 mA h g−1 at 50 mA g−1 current rate. This work paves the way to synthesize other graphene–metal oxide composites (with unique metal oxide morphologies) for their use as anode materials in Li-ion batteries.MOE (Min. of Education, S’pore

Sustainable Biomass-Derived Carbon Electrodes for Potassium and Aluminum Batteries : Conceptualizing the Key Parameters for Improved Performance

The development of sustainable, safe, low-cost, high energy and density power-density energy storage devices is most needed to electrify our modern needs to reach a carbon-neutral society by ~2050. Batteries are the backbones of future sustainable energy sources for both stationary off-grid and mobile plug-in electric vehicle applications. Biomass-derived carbon materials are extensively researched as efficient and sustainable electrode/anode candidates for lithium/ sodium-ion chemistries due to their well-developed tailored textures (closed pores and defects) and large microcrystalline interlayer spacing and therefore opens-up their potential applications in sustainable potassium and aluminum batteries. The main purpose of this perspective is to brief the use of biomass residues for the preparation of carbon electrodes for potassium and aluminum batteries annexed to the biomass-derived carbon physicochemical structures and their aligned electrochemical properties. In addition, we presented an outlook as well as some challenges faced in this promising area of research. We believe that this review enlightens the readers with useful insights and a reasonable understanding of issues and challenges faced in the preparation, physicochemical properties and application of biomass-derived carbon materials as anodes and cathode candidates for potassium and aluminum batteries, respectively. In addition, this review can further help material scientists to seek out novel electrode materials from different types of biomasses, which opens up new avenues in the fabrication/development of next-generation sustainable and high-energy density batteries.peerReviewe