Fast-charging high-energy lithium-ion batteries via implantation of amorphous silicon nanolayer in edge-plane activated graphite anodes

As fast-charging lithium-ion batteries turn into increasingly important components in forthcoming applications, various strategies have been devoted to the development of high-rate anodes. However, despite vigorous efforts, the low initial Coulombic efficiency and poor volumetric energy density with insufficient electrode conditions remain critical challenges that have to be addressed. Herein, we demonstrate a hybrid anode via incorporation of a uniformly implanted amorphous silicon nanolayer and edge-site-activated graphite. This architecture succeeds in improving lithium ion transport and minimizing initial capacity losses even with increase in energy density. As a result, the hybrid anode exhibits an exceptional initial Coulombic efficiency (93.8%) and predominant fast-charging behavior with industrial electrode conditions. As a result, a full-cell demonstrates a higher energy density (>= 1060 Wh l(-1)) without any trace of lithium plating at a harsh charging current density (10.2 mA cm(-2)) and 1.5 times faster charging than that of conventional graphite

Conductive Cellulose Composites with Low Percolation Threshold for 3D Printed Electronics

We are reporting a 3D printable composite paste having strong thixotropic rheology. The composite has been designed and investigated with highly conductive silver nanowires. The optimized electrical percolation threshold from both simulation and experiment is shown from 0.7 vol. % of silver nanowires which is significantly lower than other composites using conductive nano-materials. Reliable conductivity of 1.19 × 102 S/cm has been achieved from the demonstrated 3D printable composite with 1.9 vol. % loading of silver nanowires. Utilizing the high conductivity of the printable composites, 3D printing of designed battery electrode pastes is demonstrated. Rheology study shows superior printability of the electrode pastes aided by the cellulose\u27s strong thixotropic rheology. The designed anode, electrolyte, and cathode pastes are sequentially printed to form a three-layered lithium battery for the demonstration of a charging profile. This study opens opportunities of 3D printable conductive materials to create printed electronics with the next generation additive manufacturing process

Raman spectroscopic and structural studies of heat-treated graphites for lithium-ion batteries

Standard graphite TIMREX(R) SLX 50 was oxidised at 500-800 °C under air atmosphere in a muffle and a rotary furnace. Scanning Electron Microscopy (SEM), Raman spectroscopy, and X-Ray Powder Diffraction (XRD) were used to study the changes in surface morphology and crystallinity. The results show a slight increase of the La value and a decrease of the rhombohedral fraction with increased heat-treatment temperature (HTT). XRD measurements show no significant change in La values within the bulk of graphite samples. Above 700 °C SEM images of graphite reveals holes and cavities, whereas heat-treatment temperatures below 700 °C do not significantly affect graphite materials parameters

High-performance, nano-structured LiMnPO4 synthesized via a polyol method

A novel polyol synthesis was adopted to synthesize nano-structured LiMnPO4. This route yields well-crystallized nanoparticles with platelet morphology that are only similar to 30 nm thick oriented in the b direction. The obtained material presented a good rate behavior and a very long cyclic life both at room temperature (RT) and 50 degrees C. The sample exhibited a specific capacity of 145 mAh g(-1) at C/20, 141 mAh g(-1) at C/10 rate and 113 mAh g(-1) 1C rate. This represents is the highest performance results reported to date for this material. The high rate performance is ascribed to the platelet shape of the LiMnPO4 as it minimizes the paths for Li diffusion. At elevated temperature (50 degrees C) this material demonstrated improved reversible capacity of 159 mAh g(-1) at C/10 and 138 at 1C. The electrode retained 95% of its capacity, over 200 cycles, both at RT and 50 degrees C. This electrochemical stability is ascribed to the structural strength of the P-O bond and the stability of the electrolyte-LiMnPO4 interface. It allows us to conclude that the impact of a possible Jahn-Teller distortion is not critical. These excellent results clarified some ambiguities on LiMnPO4 as cathode materials. and demonstrate its promise for its practical application. (C) 2008 Elsevier B.V. All rights reserved

A short review on surface chemical aspects of Li batteries: A key for a good performance

We review herein several important aspects of surface chemistry in Li-ion batteries, and discuss the use of ionic liquids (ILs) for rechargeable Li batteries. We explored the suitability of ILs for 5 V cathodes and Li-graphite anodes. Some advantages of the use of ILs to attenuate the thermal behavior of delithiated cathode materials are demonstrated. We also report briefly on a comparative study of the following cathode materials: LiNi0.5Mn0.5O2; LiNi0.33Mn0.33Co0.33O2; LiNi0.4Mn0.4Co0.2O2; LiNi0.8Co0.15Al0.05O2 and LiMnPO4, in standard electrolyte solutions based on mixtures of alkyl carbonates and LiPF6. We also discuss aging, rate capability, cycle life and surface chemistry of these cathode materials. The techniques applied included electrochemical measurements, e.g., XRD, HRTEM, Raman spectroscopy, XPS and FRIR spectroscopy. We found that ILs based on cyclic quaternary alkyl ammonium cations may provide much better electrolyte solutions for 5 V cathodes than standard electrolyte solutions. while being quite suitable for Li-graphite electrodes. All the lithiated transition metal oxides studied (as mentioned above) develop unique surface chemistry during aging and cycling due to the acid-base and nucleophilic reactions of their surface oxygen anions. LiMn0.33Ni0.33Co0.33O2 has the highest rate capability compared to all the other above-mentioned cathode materials. Cathodes comprising nanometric size carbon-coated LiMnPO4 produced by HPL demonstrate a better rate capability than LiNi0.5Mn0.5O2 and LiNi0.8Co0.15Al0.05O2 cathodes. The former material seems to be the least surface reactive with alkyl carbonates/LiPF6 solutions, among all the cathode materials explored herein. (C) 2008 Elsevier B.V. All rights reserved