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51.
Suppression of Voltage Decay through Manganese Deactivation and Nickel Redox Buffering in High‐Energy Layered Lithium‐Rich Electrodes 下载免费PDF全文
Kyojin Ku Jihyun Hong Hyungsub Kim Hyeokjun Park Won Mo Seong Sung‐Kyun Jung Gabin Yoon Kyu‐Young Park Haegyeom Kim Kisuk Kang 《Liver Transplantation》2018,8(21)
Cobalt‐free layered lithium‐rich nickel manganese oxides, Li[LixNiyMn1?x?y]O2 (LLNMO), are promising positive electrode materials for lithium rechargeable batteries because of their high energy density and low materials cost. However, substantial voltage decay is inevitable upon electrochemical cycling, which makes this class of materials less practical. It has been proposed that undesirable voltage decay is linked to irreversible structural rearrangement involving irreversible oxygen loss and cation migration. Herein, the authors demonstrate that the voltage decay of the electrode is correlated to Mn4+/Mn3+ redox activation and subsequent cation disordering, which can be remarkably suppressed via simple compositional tuning to induce the formation of Ni3+ in the pristine material. By implementing our new strategy, the Mn4+/Mn3+ reduction is subdued by an alternative redox reaction involving the use of pristine Ni3+ as a redox buffer, which has been designed to be widened from Ni3+/Ni4+ to Ni2+/Ni4+, without compensation for the capacity in principle. Negligible change in the voltage profile of modified LLNMO is observed upon extended cycling, and manganese migration into the lithium layer is significantly suppressed. Based on these findings, we propose a general strategy to suppress the voltage decay of Mn‐containing lithium‐rich oxides to achieve long‐lasting high energy density from this class of materials. 相似文献
52.
Jian Qing Xiao‐Ke Liu Mingjie Li Feng Liu Zhongcheng Yuan Elizaveta Tiukalova Zhibo Yan Martial Duchamp Shi Chen Yuming Wang Sai Bai Jun‐Ming Liu Henry J. Snaith Chun‐Sing Lee Tze Chien Sum Feng Gao 《Liver Transplantation》2018,8(21)
Recently, Ruddlesden–Popper perovskites (RPPs) have attracted increasing interests due to their promising stability. However, the efficiency of solar cells based on RPPs is much lower than that based on 3D perovskites, mainly attributed to their poor charge transport. Herein, a simple yet universal method for controlling the quality of RPP films by a synergistic effect of two additives in the precursor solution is presented. RPP films achieved by this method show (a) high quality with uniform morphology, enhanced crystallinity, and reduced density of sub‐bandgap states, (b) vertically oriented perovskite frameworks that facilitate efficient charge transport, and (c) type‐II band alignment that favors self‐driven charge separation. Consequently, a hysteresis‐free RPP solar cell with a power conversion efficiency exceeding 12%, which is much higher than that of the control device (1.5%), is achieved. The findings will spur new developments in the fabrication of high‐quality, aligned, and graded RPP films essential for realizing efficient and stable perovskite solar cells. 相似文献
53.
Liquid Exfoliated Co(OH)2 Nanosheets as Low‐Cost,Yet High‐Performance,Catalysts for the Oxygen Evolution Reaction 下载免费PDF全文
David McAteer Ian J. Godwin Zheng Ling Andrew Harvey Lily He Conor S. Boland Victor Vega‐Mayoral Beata Szydłowska Aurélie A. Rovetta Claudia Backes John B. Boland Xin Chen Michael E. G. Lyons Jonathan N. Coleman 《Liver Transplantation》2018,8(15)
Identifying cheap, yet effective, oxygen evolution catalysts is critical to the advancement of water splitting. Using liquid exfoliated Co(OH)2 nanosheets as a model system, a simple procedure is developed to maximize the activity of any oxygen evolution reaction nanocatalyst. First the nanosheet edges are confirmed as the active areas by analyzing the catalytic activity as a function of nanosheet size. This allows the authors to select the smallest nanosheets (length ≈50 nm) as the best performing catalysts. While the number of active sites per unit electrode area can be increased via the electrode thickness, this is found to be impossible beyond ≈10 µm due to mechanical instabilities. However, adding carbon nanotubes increases both toughness and conductivity significantly. These enhancements mean that composite electrodes consisting of small Co(OH)2 nanosheets and 10 wt% nanotubes can be made into freestanding films with thickness of up to 120 µm with no apparent electrical limitations. The presence of diffusion limitations results in an optimum electrode thickness of 70 µm, yielding a current density of 50 mA cm?2 at an overpotential of 235 mV, close to the state of the art in the field. Applying this procedure to a high‐performance catalyst such as NiFeOx should significantly surpass the state of the art. 相似文献
54.
Synthesis, structure and properties of a new layered gadolinium benzenedicarboxylate with piperazine
A hydrothermal reaction of a mixture of Gd(NO3)3, 1,2-benzenedicarboxylic acid (1,2-BDC), piperazine, NaOH and water at 180 °C for three days under autogeneous pressure gave rise to a new compound of the formula [C4N2H12][Gd2(H2O)2(C6H4(COO)2)2] (I). The connectivity between GdO8 distorted dodecahedra and 1,2-BDC units gives rise to a two-dimensional structure with large apertures. The fully protonated piperazine molecule occupies the middle of these apertures. The compound has favorable CH?π interactions between the benzene rings of adjacent layers and shows photoluminescence at room temperature. Crystal data: monoclinic, space group = P21/c (No. 14), a = 13.1671(3) Å, b = 13.7336(3) Å, c = 11.3100(1) Å, β = 115.411(1)°, v = 1847.34(6) Å3, Z = 4, R1 = 0.0238 for 2658 reflections [I > 2σ(I)]. 相似文献
55.
R. L. McIntosh P. J. Katinic J. D. Allison J. H. Borden D. L. Downey 《Agricultural and Forest Entomology》2001,3(2):113-120
1 Traps of four new designs were tested against the conventionally used multiple‐funnel trap to determine whether trapping of large wood‐boring insects can be improved in western Canada. All four new traps used a large collecting receptacle containing detergent‐laced water, and three presented a prominent visual silhouette above the receptacle. 2 In total, 27 336 large woodborers were captured from 10 June to 30 September in an experiment in the southern interior of British Columbia, and 4737 from 6 June to 27 July in an experiment in northern Alberta. The woodborers captured in the British Columbia experiment were mainly beetles in the families Cerambycidae (79%) and Buprestidae (15%), and woodwasps in the family Siricidae (6%). Most woodborers, e.g. three Monochamus spp. and Xylotrechus longitarsus (the predominant cerambycids), were captured throughout the summer, with peak captures in August. 3 Cross‐vane, pipe and stacked‐bottomless‐flower‐pot traps were generally superior to pan and multiple‐funnel traps for insects in nine taxa, but cross‐vane traps were the most effective overall, trapping 32% of all insects captured. 4 The large number of target insects captured in a relatively small number of traps in the two experiments suggests that employment of an efficacious trap with a large vertical silhouette and a wide, escape‐proof collecting receptacle could make mass trapping of large woodborers in timber processing areas operationally feasible. 5 Because the most effective traps were unstable in the wind, and the detergent‐laced water captured unacceptably high numbers of small mammals, design modifications are necessary. We are currently developing a wind‐firm trap, with a prominent vertical silhouette, a wide collecting surface, and an escape‐proof, but dry collecting receptacle. 相似文献
56.
Understanding the Degradation Mechanisms of LiNi0.5Co0.2Mn0.3O2 Cathode Material in Lithium Ion Batteries 下载免费PDF全文
Sung‐Kyun Jung Hyeokjo Gwon Jihyun Hong Kyu‐Young Park Dong‐Hwa Seo Haegyeom Kim Jangsuk Hyun Wooyoung Yang Kisuk Kang 《Liver Transplantation》2014,4(1)
LiNixCoyMnzO2 (NCM, 0 ≤ x,y,z < 1) has become one of the most important cathode materials for next‐generation lithium (Li) ion batteries due to its high capacity and cost effectiveness compared with LiCoO2. However, the high‐voltage operation of NCM (>4.3 V) required for high capacity is inevitably accompanied by a more rapid capacity fade over numerous cycles. Here, the degradation mechanisms of LiNi0.5Co0.2Mn0.3O2 are investigated during cycling under various cutoff voltage conditions. The surface lattice structures of LiNi0.5Co0.2Mn0.3O2 are observed to suffer from an irreversible transformation; the type of transformation depends on the cutoff voltage conditions. The surface of the pristine rhombohedral phase tends to transform into a mixture of spinel and rock salt phases. Moreover, the formation of the rock salt phase is more dominant under a higher voltage operation (≈4.8 V), which is attributable to the highly oxidative environment that triggers the oxygen loss from the surface of the material. The presence of the ionically insulating rock salt phase may result in sluggish kinetics, thus deteriorating the capacity retention. This implies that the prevention of surface structural degradation can provide the means to produce and retain high capacity, as well as stabilize the cycle life of LiNi0.5Co0.2Mn0.3O2 during high‐voltage operations. 相似文献
57.
Layered hydroxides (LHs) are promising supercapacitor electrode materials with high specific capacitances. However, they generally exhibit poor energy storage ability at high current densities due to their insulating nature. Nickel‐cobalt‐aluminum LHs are synthesized and chemically treated to form LHs with enhanced conductivity that results in greatly enhanced rate performances. The key role of chemical treatment is to enable the partial conversion of Co2+ to a more conductive Co3+ state that stimulates charge transfers. Simultaneously, the defects on the LHs caused by the selective etching of Al promoted the electrolyte diffusion within LHs. As a result, the LHs show a high specific capacitance of 738 F g?1 at 30 A g?1, which is 57.2% of 1289 F g?1 at 1 A g?1. The strategy provides a facile and effective method to achieve high performance LHs for supercapacitor electrode materials. 相似文献
58.
A Novel Strategy to Suppress Capacity and Voltage Fading of Li‐ and Mn‐Rich Layered Oxide Cathode Material for Lithium‐Ion Batteries 下载免费PDF全文
Shiming Zhang Haitao Gu Hongge Pan Suhui Yang Wubin Du Xiang Li Mingxia Gao Yongfeng Liu Min Zhu Liuzhang Ouyang Dechao Jian Feng Pan 《Liver Transplantation》2017,7(6)
Poor cycling stability is one of the key scientific issues needing to be solved for Li‐ and Mn‐rich layered oxide cathode. In this paper, sodium carboxymethyl cellulose (CMC) is first used as a novel binder in Li1.2Ni0.13Co0.13Mn0.54O2 cathode to enhance its cycling stability. Electrochemical performance is conducted by galvanostatic charge and discharge. Structure and morphology are characterized by X‐ray diffraction, scanning electronic microscopy, high‐resolution transmission electron microscopy, and X‐ray photoelectron spectroscopy. Results reveal that the CMC as binder can not only stabilize the electrode structure by preventing the electrode materials to detach from the current collector but also suppress the voltage fading of the Li1.2Ni0.13Co0.13Mn0.54O2 cathode due to Na+ ions doping. Most importantly, the dissolution of metal elements from the cathode materials into the electrolyte is also inhibited. 相似文献
59.
60.
In Situ Probing and Synthetic Control of Cationic Ordering in Ni‐Rich Layered Oxide Cathodes 下载免费PDF全文
Jianqing Zhao Wei Zhang Ashfia Huq Scott T. Misture Boliang Zhang Shengmin Guo Lijun Wu Yimei Zhu Zonghai Chen Khalil Amine Feng Pan Jianming Bai Feng Wang 《Liver Transplantation》2017,7(3)
Ni‐rich layered oxides (LiNi1–x Mx O2; M = Co, Mn, …) are appealing alternatives to conventional LiCoO2 as cathodes in Li‐ion batteries for automobile and other large‐scale applications due to their high theoretical capacity and low cost. However, preparing stoichiometric LiNi1–x Mx O2 with ordered layer structure and high reversible capacity, has proven difficult due to cation mixing in octahedral sites. Herein, in situ studies of synthesis reactions and the associated structural ordering in preparing LiNiO2 and the Co‐substituted variant, LiNi0.8Co0.2O2, are made, to gain insights into synthetic control of the structure and electrochemical properties of Ni‐rich layered oxides. Results from this study indicate a direct transformation of the intermediate from the rock salt structure into hexagonal phase, and during the process, Co substitution facilities the nucleation of a Co‐rich layered phase at low temperatures and subsequent growth and stabilization of solid solution Li(Ni, Co)O2 upon further heat treatment. Optimal conditions are identified from the in situ studies and utilized to obtain stoichiometric LiNi0.8Co0.2O2 that exhibits high capacity (up to 200 mA h g?1 ) with excellent retention. The findings shed light on designing high performance Ni‐rich layered oxide cathodes through synthetic control of the structural ordering in the materials. 相似文献