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Dai Y.,Shanghai Institute of Space Power Sources | Dai Y.,Shanghai University | Cai S.,Shanghai Institute of Space Power Sources | Cai S.,Shanghai University | And 7 more authors.
Journal of Materials Chemistry A | Year: 2014

Li/CFx primary possesses the highest energy density of 2180 W h kg-1 among all primary lithium batteries. However, a key limitation for the utility of this type of battery is in its poor rate capability because the cathode material, CFx, is an intrinsically poor electronic conductor. Here, we report on our development of a controlled process of surface de-fluorination under mild hydrothermal conditions to modify the highly fluorinated CFx. The modified CFx, consisting of an in situ generated shell component of F-graphene layers, possesses good electronic conductivity and removes the transporting barrier for lithium ions, yielding a high-capacity performance and an excellent rate-capability. Indeed, a capacity of 500 mA h g-1 and a maximum power density of 44 800 W kg-1 can be realized at the ultrafast rate of 30 C (24 A g-1), which is over one order of magnitude higher than that of the state-of-the-art primary lithium-ion batteries. © The Royal Society of Chemistry 2014. Source

Luo Y.,Harbin Institute of Technology | Luo Y.,Power-battery | Luo Y.,Shanghai Engineering Center for Power and Energy Storage Systems | Lu T.,Harbin Institute of Technology | And 9 more authors.
Journal of Power Sources | Year: 2016

A new electrolyte based on fluorinated 3-(1,1,2,2-tetrafluoroethoxy)-1,1,2,2-tetrafluoropropane (F-EPE) solvent is studied in LiNi0.5Mn1.5O4/Li cells. The electrochemical stability of the electrolyte with 10% F-EPE is carried out by linear sweep voltammetry and electrochemical floating test. These results indicate that the electrolyte with F-EPE has an oxidation potential of more than 5.2 V vs. Li+/Li, which is higher than that without F-EPE and enlarges the oxidative window of electrolyte. A thin and uniform SEI layer is formed on the surface of LiNi0.5Mn1.5O4 cathode by using electrolyte with F-EPE, leads to an improvement in the electrochemical performance, validated by charge-discharge tests, EIS, SEM, TEM, and XPS analysis. © 2016 Published by Elsevier B.V. Source

With rapidly growing application of lithium-ion batteries in electric vehicles and renewable energy storage, there is an increasing demand on high performance batteries in terms of energy density and power density. For anode materials, the traditional graphitized carbon materials cannot meet these requirements, novel high-capacity anode materials are being widely investigated, including Si-based materials. Among them, SiOx is considered to be a promising anode material for the practical use because it can deliver a high capacity and at thesame time produce relatively lower volume change upon cycling compared to pure silicon. This paper summarizes the published works on SiOx-based anode materials. The basic electrochemical performance, structure model, electrochemical reaction mechanism and synthesis methods of SiOx powders are systematically reviewed. Methods used to improve electrochemical performance are classified and introduced, emphasized on those of SiO and amorphous SiO2. These works suggested that the oxygen content, disproportionation level and surface state of SiOx have significant influence on the electrochemical performance of SiOx. The interface clusters mixture (ICM) structural model can be used to better understand the nature of the electrochemical reaction processes of SiOx. Introduction of second phase (carbon, metals, metal oxides, etc.), preparation of porous structure, surface modification and optimization of binder and electrolyte are proved to be effective methods to improve the coulombic efficiency and cycling performance of SiOx electrode. Batteries with optimized SiOx-based material showed good cycling stability with 90% capacity retention after 600 cycles. SiOx-based composite is one of the best promising anode materials for lithium-ion batteries with high energy density. ©, 2015, Chinese Academy of Sciences. All right reserved. Source

Yang W.,Shanghai Institute of Space Power Sources | Yang W.,Shanghai Engineering Center for Power and Energy Storage Systems | Dai Y.,Shanghai Institute of Space Power Sources | Dai Y.,Shanghai Engineering Center for Power and Energy Storage Systems | And 9 more authors.
Journal of Power Sources | Year: 2014

We report the application of free-standing, lightweight, and flexible graphene/Au composite paper (GACP), as a current collector for CFx cathode. At a high discharge current density of 4000 mA g-1 (5C), the capacity of the CF1.0 loaded on GACP current collector is 653 mAh g-1, while CF1.0 loaded on Al foil failed at 800 mA g -1 (1C). Using GACP, both excellent rate capability and specific capacity can be achieved simultaneously, owing to its undulant surface structure and flexible contact with the CFx composite active layer. Our results provide a new strategy to design both high power and energy densities CFx cathode. © 2014 Published by Elsevier B.V. All rights reserved. Source

Dai Y.,Shanghai Institute of Space Power Sources | Dai Y.,Shanghai Engineering Center for Power and Energy Storage Systems | Cai S.,Shanghai Institute of Space Power Sources | Cai S.,Shanghai Engineering Center for Power and Energy Storage Systems | And 10 more authors.
Carbon | Year: 2012

Self-binding noble metal (Pt, Au, and Ag)/graphene composite papers as large as 13 cm in diameter were fabricated using a flow-directed method where in situ reduced graphene served as a "binder". The papers were characterized by X-ray diffraction, scanning and transmission electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. This approach yielded well dispersed metals with various nanostructures both on and between the graphene layers to form papers with good conductivity and flexiblility. The 300 °C-annealed Ag/graphene papers were evaluated as binder-free anodes for lithium ion batteries, delivering a reversible charge capacity of 689 mAh/g at a current density of 20 mA/g. © 2012 Elsevier Ltd. All rights reserved. Source

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