Lithium intercalation/de-intercalation behavior of a composite Sn/C thin film fabricated by magnetron sputtering

A tin film of 320 nm in thickness on Cu foil and its composite film with graphite of-50 nm in thickness on it were fabricated by magnetron sputtering. The surface morphology, composition, surface distributions of alloy elements, and lithium intercalation/de-intercalation behaviors of the fabricated films were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, electron probe microanalyzer （EPMA）, X-ray photoelectron spectroscopy （XPS）, inductively coupled plasma atomic emission spectrometry （ICP）, cyclic voltammetry （CV）, and galvanostatic charge/discharge （GC） measurements. It is found that the lithium intercalation/de-intercalation behavior of the Sn film can be significantly improved by its composite with graphite. With cycling, the discharge capacity of the Sn film without composite changes from 570 mAh/g of the 2nd cycle to 270 mAh/g of the 20th cycle, and its efficiency for the discharge and charge is between 90% and 95%. Nevertheless, the discharge capacity of the composite Sn/C film changes from 575 mAh/g of the 2nd cycle to 515 mAh/g of the 20th cycle, and its efficiency for the discharge and charge is between 95% and 100%. The performance improvement of tin by its composite with graphite is ascribed to the retardation of the bulk tin cracking from volume change during lithium intercalation and de-intercalation, which leads to the pulverization of tin.

Tailoring lithium intercalation pathway in 2D van der Waals heterostructure for high-speed edge-contacted floating-gate transistor and artificial synapses

Local phase transition in transition metal dichalcogenides (TMDCs) by lithiumintercalation enables the fabrication of high-quality contact interfaces in twodimensional(2D) electronic devices. However, controlling the intercalation oflithium is hitherto challenging in vertically stacked van der Waalsheterostructures (vdWHs) due to the random diffusion of lithium ions in thehetero-interface, which hinders their application for contact engineering of 2DvdWHs devices. Herein, a strategy to restrict the lithium intercalation pathwayin vdWHs is developed by using surface-permeation assisted intercalationwhile sealing all edges, based on which a high-performance edge-contact MoS_(2)vdWHs floating-gate transistor is demonstrated. Our method avoids intercalationfrom edges that are prone to be random but intentionally promotes lithiumintercalation from the top surface. The derived MoS_(2) floating-gatetransistor exhibits improved interface quality and significantly reduced subthresholdswing (SS) from >600 to 100 mV dec^(–1). In addition, ultrafast program/erase performance together with well-distinguished 32 memory statesare demonstrated, making it a promising candidate for low-power artificialsynapses. The study on controlling the lithium intercalation pathways in 2DvdWHs offers a viable route toward high-performance 2D electronics for memoryand neuromorphic computing purposes.

Curie and Pauli Spins in Lithium Intercalated MCMB

The ESR signal of lithium intercalated MCMB can be well simulated by combination of a Lorentz curve and a Gauss curve. The ESR intensity of the Lorentz component is essentially independent of temperature while the Gauss component shows a linear change with the reciprocal of temperature, indicative of Pauli spin and Curie spin, respectively. The former is probably associated with the ordered (graphitized) structures while the latter with the disordered structures in the sample.

The Discharge and Charge Behavior of the Pb-Birnessite in LiOH Aqueous Solution

The Pb-birnessite was prepared by ion exchange from K-birnessite, which was synthesized by calcination of KMnO4. Measure methods of SEM (scanning electron microscopy), XRD (X-ray diffraction), TGA (thermogravimetric analyse), AAS (atomic absorption spectrometry), slow-scanning cyclic voltammetry and galvanostatic step discharge/charge are applied. Potentiostatic step method is used for the determination of a chemical diffusion coefficientD is Li+. XRD patterns indicate the Pb-birnessite has layered structure. Slow-scanning voltammograms show the occurrence of a single-phase redox reaction. The galvanostatic discharge/charge curves indicate the Pb-birnessite has better rechargeability at a high discharge/charge rate. Li+ can reversibly intercalate into and de-intercalate from the Pb-birnessite during discharge and charge. Pb between the layers stabilized the layered structure and prevented partially the conversion to spinel-like structures. The average value of the chemical diffusion coefficientD of Li+ intercalated into the Pb-birnessite is 8.24×10?11 cm2·s?1. Key words Birnessite - Pb2+-doped - single-phase redox reaction - Lithium intercalation CLC number O 646.54 Foundation item: Supported by the National Natural Science Foundation of China (20077020)Biography: ZHU Xin-gong (1979-), male, Master, research direction: electrochemistry.

New Superionic Memory Devices Can Provide Clues to the Human Memory Structure and to Consciousness

Since the work of Penrose and Hameroff the possibility is discussed that the location of human memory and consciousness could be connected with tubulin microtubules. If one would use superionic nano-materials rolled up to microtubules with an electrolyte inside the formed channels mediating fast ionic exchange of protons respectively lithium ions, it seems to be possible to write into such materials whole image arrays (pictures) under the action of the complex electromagnetic spectrum that composes these images. The same material and architecture may be recommended for super-computers. Especially microtubules with a protofilament number of 13 are the most important to note. We connected such microtubules before with Fibonacci nets composed of 13 sub-cells that were helically rolled up to deliver suitable channels. Our recent Fibonacci analysis of Wadsley-Roth shear phases such as niobium tungsten oxide , exhibiting channels for ultra-fast lithium-ion diffusion, suggests to use these materials, besides super-battery main application, in form of nanorods or microtubules as effectively working superionic memory devices for computers that work ultra-fast with the complex effectiveness of human brains. Finally, we pose the question, whether dark matter, ever connected with ultrafast movement of ordinary matter, may be responsible for synchronization between interactions of human brains and consciousness.

Lithium-assisted exfoliation of pristine graphite for few-layer graphene nanosheets

A lithium-assisted approach has been developed for the exfoliation of pristine graphite, which allows the large-scale preparation of few-layer graphene nanosheets. The process involves an unexpected physical insertion and exfoliafion, and the graphene nanosheets prepared by this method reveal undisturbed sp2-hybridized structures. A possible two-step mechanism, which involves the negative charge being trapped around the edges of the graphite layers and a subsequent lithiation process, is proposed to explain the insertion of lithium inside the graphite interlayers. If necessary, the present exfoliation can be repeated and thinner （single or 2-3 layer） graphene can be achieved on a large scale. This simple process provides an efficient process for the exfoliation of pristine graphite, which might promote the future applications of graphene.