Preparation of Expanded Graphite-based Composites by One Step Impregnation

A new method for preparing expanded graphite-based composites （EGCs） was developed.The obtained samples were characterized by scanning electron microscopy （SEM）,transmission electron microscope （TEM） and nitrogen adsorption.The experimental results indicated that the EGCs was not simply mechanical mixture of EG and activated carbon,instead the activated carbon was coated on the surface of interior and external pores of the EG in the form of thin carbon layer.The thickness of the activated carbon layer was nearly one hundred nanometers by calculation.It was shown that the higher the impregnation ratio and the activation temperature were,the easier the porosity development would be.And the BET surface area and the total pore volume were as high as 1978 m2/g and 0.9917 cm3/g respectively at 350℃ with an impregnation ratio of 0.9.

Electrolyte engineering and material modification for graphite-based lithium-ion batteries operated at low temperature

Graphite offers several advantages as an anode material,including its low cost,high theoretical capacity,extended lifespan,and low Li+-intercalation potential.However,the performance of graphite-based lithium-ion batteries(LIBs)is limited at low temperatures due to several critical challenges,such as the decreased ionic conductivity of liquid electrolyte,sluggish Li+desolvation process,poor Li+diffusivity across the interphase layer and bulk graphite materials.Various approaches have therefore been explored to address these challenges.On the basis of graphite anode and corresponding LIBs,this review herein offers a comprehensive analysis of the latest advances in electrolyte engineering and electrode modification.First,electrolyte engineering is discussed in detail,highlighting the design of new electrolyte formula with broad liquid temperature range,optimized solvation structure,and well-performed inorganic-rich solid electrolyte interface.The advances in material modification have been then depicted with the view of improving the solid bulk diffusion rate to show general strategies with excellent performance at low temperatures.Finally,the corresponding challenges and opportunities have also been outlined to shed light on viable strategies for developing efficient and reliable graphite anode and graphite-based LIBs under low-temperature scenarios.

Graphite-based solid lubricant for high-temperature lubrication

High-temperature solid lubricants play a significant role in the hot metal forming process.However,preparing high-temperature solid lubricant is formidably challenging due to the stern working conditions.Here we successfully develop a new type of eco-friendly high-temperature graphite-based solid lubricant by using amorphous silica dioxide,aluminum dihydrogen phosphate,and solid lubricant graphite.The solid lubricating coating exhibits excellent tribological properties with a very low friction coefficient and good wear protection for workpiece at high temperature under the air atmosphere.An array of analytical techniques reveals the existence of solid lubricant graphite in the lubricating coating after the high-temperature friction test.A synergistic effect between the protective surface film and the solid lubricant graphite is proposed to account for such superior lubricating performance.This work highlights the synergistic effect between the protection layer and the lubricant graphite and further provides the insight in designing the high-temperature solid lubricant.

Phase Transformation of Lithium-rich Oxide Cathode in Full Cell and its Suppression by Solid Electrolyte Interphase on Graphite Anode

Lithium-rich oxide is one of the most promising cathodes that meet high energy density requirement for batteries of the future, but its phase transformation from layer to spinel structure caused by the lattice instability presents severe challenge to cycling stability and the actually accessible capacity. The currently available approaches to suppress this undesired irreversible process often resort to limit the high voltages that lithium-rich oxide is exposed to. However, cycling stability thus improved is at the expense of the eventual energy output. In this work, we identified a new mechanism that is directly responsible for the lithium-rich oxide phase transformation and established a clear correlation between the successive consumption of Li+on anode due to incessant interphase repairing and the over-delithiation of lithium-rich oxide cathode. This new mechanism enables a simple but effective solution to the cathode degradation, in which an electrolyte additive is used to build a dense and protective interphase on anode with the intention to minimize Li depletion at cathode. The application of this new interphase effectively suppresses both electrolyte decomposition at anode and the phase transformation of lithium-rich oxide cathode, leading to high capacity and cycling stability.

Oxidation Behaviors of C-ZrB_2-SiC Composite at 2100℃ in Air and O_2

The oxidation behaviors of graphite and ZrB2-SiC modified graphite composite were investigated at 2100℃ in1X105 Pa air and 0.2X105 Pa O2. The oxidation tests were conducted in an induction heating furnace. The oxidation of these two materials followed the linear rate law. The determined radius loss rates of graphite and C-ZrB2-Si C at 2100℃ were 2.18X10-2and 1.05X10-2%/s in 1X105 Pa air, and 3.23X10 2 and 2.21X10 2%/s in 0.2X105 Pa O2, respectively. The incorporation of ZrB2 and SiC decreased remarkably the oxidation rate of graphite because the oxide scale formed on the sample surface during oxidation helps in reducing the exposed surface area of the underneath substrate. In two different atmospheres with the same oxygen partial pressure, both graphite and ZrB2-SiC experienced more severe oxidation at 2100℃ in0.2X105 Pa O2than in 1X105 Pa air. The oxidation rate-controlling step for graphite and ZrB2-SiC was proposed to be the inward diffusion of oxygen through the boundary layer and through the pores in the oxide scale, respectively. A model based on diffusion theory was established to discuss the effect of the total gas pressure on their oxidation behaviors.