High-tap-density silicon nanomaterials are highly desirable as anodes for lithium ion batteries, due to their small surface area and minimum first-cycle loss. However, this material poses formidable challenges to polymeric binder design. Binders adhere on to the small surface area to sustain the drastic volume changes during cycling; also the low porosities and small pore size resulting from this material are detrimental to lithium ion transport. This study introduces a new binder, poly(1-pyrenemethyl methacrylate-co-methacrylic acid) (PPyMAA), for a high-tap-density nanosilicon electrode cycled in a stable manner with a first cycle efficiency of 82%—a value that is further improved to 87% when combined with graphite material. Incorporating the MAA acid functionalities does not change the lowest unoccupied molecular orbital (LUMO) features or lower the adhesion performance of the PPy homopolymer. Our single-molecule force microscopy measurement of PPyMAA reveals similar adhesion strength between polymer binder and anode surface when compared with conventional polymer such as homopolyacrylic acid (PAA), while being electronically conductive. The combined conductivity and adhesion afforded by the MAA and pyrene copolymer results in good cycling performance for the high-tap-density Si electrode.

ABSTRACTthat was removed from a tested high-power Li-ion cell, which suffered substantial power and capacity loss, showed that the state of charge (SOC) of oxide particles on the cathode surface was highly non-uniform despite deep discharge of the Li-ion cell at the end of the test. In-situ monitoring of the SOC of selected oxide particles in the composite cathode in a sealed spectro-electrochemical cell revealed that the rate at which particles charge and discharge varied with time and location. The inconsistent kinetic behavior of individual oxide particles was attributed to degradation of the electronically conducting matrix in the composite cathode upon testing. These local micro-phenomena are responsible for the overall impedance rise of the cathode and contribute to the mechanism of lithium-ion cell failure. * r_kostecki@lbl.gov 2

PAPER Jinglei Lei et al.A one-step, cost-eff ective green method to in situ fabricate Ni(OH) 2 hexagonal platelets on Ni foam as binder-free supercapacitor electrode materials Nickel hydroxide (Ni(OH) 2 ) is considered to be a promising alternative to the expensive and toxic RuO 2 electrode material for high-performance supercapacitors; however, the fabrication method and electrochemical performance of suitable Ni(OH) 2 structures are unsatisfactory. In the present work, a facile, cost-effective green method is developed to in situ fabricate Ni(OH) 2 hexagonal platelets on Ni foam as a binder-free supercapacitor electrode with high performance. The Ni(OH) 2 hexagonal platelets are self-grown on three-dimensional (3D) Ni foam by a one-step hydrothermal treatment of Ni foam in a 15 wt% H 2 O 2 aqueous solution without the use of nickel salts, acids, bases, or post-treatments. The asprepared Ni(OH) 2 hexagonal platelets-Ni foam (HNF) electrode can be used directly as a supercapacitor electrode material, thereby avoiding the need for binders and conducting agents. The Ni(OH) 2 hexagonal platelets demonstrate high capacitance (2534 F g À1 at a scan rate of 1 mV s À1 ) and excellent cycling stability (97% capacitance retention after 2000 cycles at a scan rate of 50 mV s À1 ). The fabrication method developed here has the significant advantage of low-cost, facile, green, and additive-free processing, and it is therefore a promising route for preparing self-supported metal (hydr)oxide electrodes for high-performance supercapacitors and other energy-storage devices.

A pouch-type lithium-ion cell, with graphite anode and LiNi 0.8 Co 0.15 Al 0.05 O 2 cathode, was cycled at C/2 over 100% depth of discharge (DOD) at ambient temperature. The

In situ spectroscopic ellipsometry was employed to study the initial stage of solid electrolyte interphase ͑SEI͒ layer formation on thin-film LiMn 2 O 4 electrodes. The SEI layer formed immediately upon exposure of the electrode to ethylene carbonate/dimethyl carbonate ͑1:1 by vol͒ 1.0 M LiPF 6 electrolyte. The SEI layer thickness then increased in proportion to a logarithmic function of elapsed time. In comparison, the SEI layer thickness on a cycled electrode increased in proportion to a linear function of the number of cycles.It is well known that both the anode ͑negative electrode͒ and cathode ͑positive electrode͒ in Li-ion batteries are almost covered with a passive surface layer, which is generally called the solid electrolyte interphase ͑SEI͒. Peled ͑1979͒ introduced the idea of the SEI layer on alkali and alkaline earth metals in organic electrolytes. 1 SEI layer formation has been observed for various electrode materials such as Li foil, carbon, and transition-metal oxides. [2][3][4][5][6][7][8][9][10][11][12] The SEI layer plays a key role in the electrochemical performance and calendar life of Li-ion batteries because it prevents the electrode surface from further reacting with the electrolyte components, thereby increasing the cell impedance and decreasing its cycling efficiency. 13 Due to its important role in Li-ion batteries, analytical techniques such as X-ray photoelectron spectroscopy ͑XPS͒, 2-4,10,11 nuclear magnetic resonance ͑NMR͒, 8 and Fourier transform infrared spectroscopy 9-11 have been employed to study the nature and formation mechanisms of the SEI layer.Reported thicknesses of SEI layers on anodes ͑Li metal or carbon͒ range from tens to hundreds of nanometers. 4,5 Meitav and Peled calculated the thickness of the SEI layer on lithium electrodes based on the differential capacitance and coulombic measurements. 14 The development of modern surface characterization techniques allowed direct observation and characterization of the morphology of SEI layers. In situ atomic force microscopy was used to study SEI thickness and morphology. 15,16 Lee and Pyun examined the morphology of the SEI layer on graphite using high resolution transmission electron microscopy. 17 Andersson et al. used XPS to study the depth profile of SEI formed on a graphite powder electrode in a Li-ion battery. 18 Compared with the anode SEI layer, the cathode SEI layer is apparently so thin that its presence has not been confirmed until recently. Greenbaum et al. used NMR to detect a passivating layer on a LiNi 0.8 Co 0.2 O 2 cathode and concluded that it eventually led to the loss of electrical contact between active cathode particles. 8 Balasubramanian et al. observed the formation of an SEI layer on a LiNi 0.85 Co 0.15 O 2 cathode by using X-ray absorption spectroscopy. 19 Aurbach et al. found that an SEI layer, which consisted mainly of ROLi, ROCO 2 Li, polycarbonates, and some salt-reduction products such as LiF, replaced the nascent Li 2 CO 3 surface films on cathode particles ͑LiNiO 2 and LiMn 2 O 4 ͒ when batter...

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The following facile approach has been developed to prepare a biomimetic-structural superhydrophobic surface with high stabilities and strong resistances on 2024 Al alloy that are robust to harsh environments. First, a simple hydrothermal treatment in a La(NO3)3 aqueous solution was used to fabricate ginkgo-leaf like nanostructures, resulting in a superhydrophilic surface on 2024 Al. Then a low-surface-energy compound, dodecafluoroheptyl-propyl-trimethoxylsilane (Actyflon-G502), was used to modify the superhydrophilic 2024 Al, changing the surface character from superhydrophilicity to superhydrophobicity. The water contact angle (WCA) of such a superhydrophobic surface reaches up to 160°, demonstrating excellent superhydrophobicity. Moreover, the as-prepared superhydrophobic surface shows high stabilities in air-storage, chemical and thermal environments, and has strong resistances to UV irradiation, corrosion, and abrasion. The WCAs of such a surface almost remain unchanged (160°) after storage in air for 80 days, exposure in 250 °C atmosphere for 24 h, and being exposed under UV irradiation for 24 h, are more than 144° whether in acidic or alkali medium, and are more than 150° after 48 h corrosion and after abrasion under 0.98 kPa for 1000 mm length. The remarkable durability of the as-prepared superhydrophobic surface can be attributed to its stable structure and composition, which are due to the existence of lanthanum (hydr)oxides in surface layer. The robustness of the as-prepared superhydrophobic surface to harsh environments will open their much wider applications. The fabricating approach for such robust superhydrophobic surface can be easily extended to other metals and alloys.

{1̄11} faceted Ni3S2 with an asymmetric zigzag structure is elaborately designed and fabricated, which exhibits remarkable electrocatalytic performance for the HER and OER.