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    Graphene: This could be a Free Energy Breakthrough: Update

    I thought our readers might be missing the battery stories.  They even copy each others headlines now days. The good news is a lot of people are researching chasing the holy grail of battery technology.

    Figure 1 NMR/Raman Spectra and Proposed Mechanism of the Reaction of Li2S6 and P2S5 at Different Ratios (A) The 31P NMR solution spectra of P2S5 and LSPS at different Li2S6/P2S5 ratios as labeled. (B) The proposed complexing mechanism of Li2S6 with P2S5, where nucleophilic attack of the polysulfide anions at the P=S bond leads to ionic polymerization of P2S5. (C and D) Solid-state Raman spectra of P2S5, Li2S6, and LSPS (C) at different Li2S6/P2S5 ratios as labeled. Gray regions indicate the S-S vibrations in Li2S6 and the green region indicates a shifted Li-S band. (D) Expanded Raman spectra of the two S-S bands in the region between 120 and 240 cm−1. The minor peaks in the 31P spectra in (A) are due to the trace impurities in commercial P2S5 and their reaction with Li2S6.

    Triple the range of electric vehicles.

    New research at the University of Waterloo could lead to the development of batteries that triple the range of electric vehicles.

    The breakthrough involves the use of negative electrodes made of lithium metal, a material with the potential to dramatically increase battery storage capacity.

    “This will mean cheap, safe, long-lasting batteries that give people much more range in their electric vehicles,” said Quanquan Pang, who led the research while he was a PhD candidate at Waterloo.

    The increased storage capacity, or energy density, could boost the distance electric vehicles are able to travel on a single charge, from about 200 kilometres to 600 kilometres.

    In creating the technology, Pang and fellow researchers, including supervisor Linda Nazar, a professor of chemistry and chemical engineering at Waterloo, had to overcome two challenges.

    The first challenge involved a risk of fires and explosions caused by microscopic structural changes to the lithium metal during repeated charge-discharge cycles.

    The second involved a reaction that creates corrosion and limits both how well the electrodes work and how long they last.

    Researchers solved both problems by adding a chemical compound made of phosphorus and sulfur elements to the electrolyte liquid that carries electrical charge within batteries.

    The compound reacts with the lithium metal electrode in an already assembled battery to spontaneously coat it with an extremely thin protective layer.

    “We wanted a simple, scalable way to protect the lithium metal,” said Pang, now a post-doctoral fellow at the Massachusetts Institute of Technology. “With this solution, we just add the compound and it works by itself.”

    The novel approach paves the way for electric vehicle batteries that enjoy the benefits of lithium metal electrodes – greater storage capacity and therefore greater driving range – without comprising safety or reducing lifespan.

    Reference: 

    A paper on the research was published today in the journal Joule.

    Link: http://www.cell.com/joule/fulltext/S2542-4351(17)30180-0

    An In Vivo Formed Solid Electrolyte Surface Layer Enables Stable Plating of Li Metal

    Quan Pang, Xiao Liang, Abhinandan Shyamsunder,Linda F. Nazar
    • A single-ion-conducting protective layer is created on the Li surface in vivo
    • Membrane lowers interface charge transfer resistance, Li plates underneath
    • Stable, dendrite-free Li plating in long-life symmetric cells up to 8 mA cm−2
    • Full cells using high-loading LTO electrodes demonstrate close to 99.99% CE at 5 C

    Context & Scale

    A stable Li metal anode is key to fulfilling the promises of Li-O2 and Li-S batteries and to increase the energy density of lithium transition metal oxide batteries in liquid electrolyte or solid-state configurations. However, on cycling, Li metal’s tendency to dendritic growth poses safety issues, and the loss of active lithium and accumulation of a high-impedance interphase leads to cell failure. Here, we describe a new strategy to stabilize Li plating by forming a micron-thick Li+-ion conductive solid electrolyte layer in vivo on the Li surface using an electrolyte additive. The glassy homogeneous layer reduces parasitic reactions and eliminates dendrite formation. We achieve a 50-fold lower interfacial charge transfer resistance in Li|Li symmetric cells with stable Li plating/stripping for 2,500 hr at 1 mA cm−2, and over 400 cycles at high rates in cells with an intercalation counter electrode at close to 100% coulombic efficiency with this unique, scalable method.

    Summary

    We describe an efficient yet facile strategy to stabilize Li plating by forming a single Li+-ion solid electrolyte layer in vivo on the Li surface using a rationally designed electrolyte additive. This amorphous, homogeneous layer not only reduces the direct contact and parasitic reactions of Li with the liquid electrolyte but also avoids ion depletion and electric field inhomogeneity at the vicinity of the Li surface, thus eliminating dendrite formation. This is evidenced by a 50-fold lower interfacial charge transfer resistance and an 8-fold longer Sand time in Li|Li symmetric cells. The protection layer maintains chemical and electrochemical stability over repeated plating/stripping cycles. We demonstrate stable Li plating/stripping for 2,500 hr at 1 mA cm−2 in symmetric cells, and efficient Li cycling at high current densities up to 8 mA cm−2. Over 400 cycles were achieved at 5-C rate in cells with a Li4Ti5O12 counter electrode at close to 100% coulombic efficiency.

    Angat Christmas Thank You
    Graphene: This could be a Free Energy Breakthrough: Update
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