Sonochemistry-enabled uniform coupling of SnO2 nanocrystals with graphene sheets as anode materials for lithium-ion batteries

Interphase stabilized electrospun SnO2 fibers as alloy anode via restricted cycling for Li-ion capacitors with high energy and wide temperature operation

The second-generation supercapacitor comprises the hybridized energy storage mechanism of Lithium-ion batteries and electrical double-layer capacitors, i.e, Lithium-ion capacitors (LICs). The electrospun SnO₂ nanofibers are synthesized by a simple electrospinning technique and are directly used as anode material for LICs with activated carbon (AC) as a cathode. However, before the assembly, the battery-type electrode SnO₂ is electrochemically pre-lithiated (Li_xSn + Li₂O), and AC loading is balanced with respect to its half-cell performance. First, the SnO₂ is tested in the half-cell assembly with a limited potential window of 0.005 to 1 V vs. Li to avoid the conversion reaction of Sn⁰ to SnO_x. Also, the limited potential window allows only the reversible alloy/de-alloying process. Finally, the assembled LIC, AC/(Li_xSn + Li₂O), displayed a maximum energy density of 185.88 Wh kg^-1 with ultra-long cyclic durability of over 20,000 cycles. Further, the LIC is also exposed to various temperature conditions (-10, 0, 25, & 50 °C) to study the feasibility of using them in different environmental conditions.

Cellulose sulfate lithium as a conductive binder for LiFePO4 cathode with long cycle life

Polysaccharides can be potential binders for lithium-ion batteries due to their strong adhesion through numerous hydroxyl groups. As a novel waterborne lithiated polysaccharide derivative, cellulose sulfate lithium (CSL) is successfully synthesized and used as the binder for LiFePO₄ (LFP) cathode. The chemical structure of CSL is verified by FTIR-ATR, XRD, C¹³-NMR, GPC, EA, ICP and TGA. Compared to LFP cathode using polyvinylidene difluoride binder, electrochemical measurements show that the LFP cathode using CSL (LFP-CSL) has lower polarization and better rate performance owing to higher lithium-ion conductivity of CSL. The result of morphological analysis indicates that CSL binder can maintain an integrated LFP cathode structure during hundreds of cycles. As a result, the LFP-CSL cathode exhibits a discharge capacity of 133.4 mAh g^-1 and maintains remarkable cycle stability with retention of 93.1 % after 300 cycles at 1C. These findings provide novel insights into the rational design of the binders for the LFP cathode.

Three-Dimensional SnO2 Nanoparticles Synthesized by Joule Heating as Anode Materials for Lithium Ion Batteries

Tin dioxide (SnO2) is a promising material for use as anodes because of its high theoretical capacity (1,494 mAh g−1). However, a critical limitation is the large change in volume during repeated cycling by pulverization of SnO2, which results in capacity fading. In this study, we enhanced cycle life and reduced capacity fading by introducing the use of three-dimensional SnO2 nanoparticles on carbon nanofibers (CNFs) as an anode material, which is fabricated by simple carbothermal shock through the Joule heating method. Our observations show that the SnO2 nanoparticles are about 50 nm in diameter and are uniformly distributed on CNF, and that the strong connections between SnO2 nanoparticles and CNF are sustained even after repeated cycling. This structural advantage provides high reversible capacity and enhanced cycle performance for over 100 cycles. This study provides insight into the fabrication of anode materials that have strong electric connections between active materials and conductive materials due to the Joule heating method for high-performance lithium ion batteries.

Sonochemical catalysis as a unique strategy for the fabrication of nano-/micro-structured inorganics

Ultrasound-assisted approaches, as an important trend in material synthesis, have emerged for designing and creating nano-/micro-structures. This review simply presents the basic principles of ultrasound irradiation including acoustic cavitation, sonochemical effects, physical and/or mechanical effects, and on the basis of the latest progress, it newly summarizes sonochemical catalysis for the fabrication of nano-structured or micro-structured inorganic materials such as metals, alloys, metal compounds, non-metal materials, and inorganic composites, where the theories or mechanisms of catalytic synthetic routes, and the morphologies, structures, sizes, properties and applications of products are described in detail. In the review, a few technological potentials and probable challenges of sonochemical catalysis are also highlighted for the future advance of synthesis methods. Therefore, sonochemical catalysis or ultrasound-assisted synthesis will serve as a unique strategy to reveal its great significance in material fabrication.

Advances in the Applications of Graphene-Based Nanocomposites in Clean Energy Materials

Extensive use of fossil fuels can lead to energy depletion and serious environmental pollution. Therefore, it is necessary to solve these problems by developing clean energy. Graphene materials own the advantages of high electrocatalytic activity, high conductivity, excellent mechanical strength, strong flexibility, large specific surface area and light weight, thus giving the potential to store electric charge, ions or hydrogen. Graphene-based nanocomposites have become new research hotspots in the field of energy storage and conversion, such as in fuel cells, lithium-ion batteries, solar cells and thermoelectric conversion. Graphene as a catalyst carrier of hydrogen fuel cells has been further modified to obtain higher and more uniform metal dispersion, hence improving the electrocatalyst activity. Moreover, it can complement the network of electroactive materials to buffer the change of electrode volume and prevent the breakage and aggregation of electrode materials, and graphene oxide is also used as a cheap and sustainable proton exchange membrane. In lithium-ion batteries, substituting heteroatoms for carbon atoms in graphene composite electrodes can produce defects on the graphitized surface which have a good reversible specific capacity and increased energy and power densities. In solar cells, the performance of the interface and junction is enhanced by using a few layers of graphene-based composites and more electron-hole pairs are collected; therefore, the conversion efficiency is increased. Graphene has a high Seebeck coefficient, and therefore, it is a potential thermoelectric material. In this paper, we review the latest progress in the synthesis, characterization, evaluation and properties of graphene-based composites and their practical applications in fuel cells, lithium-ion batteries, solar cells and thermoelectric conversion.