Ion-selective and chemical-protective elastic block copolymer interphase for durable zinc metal anode

Aqueous rechargeable batteries based on zinc anodes are among the most promising systems to replace conventional lithium-ion batteries owing to their intrinsic safety, high ionic conductivity, and economic benefits. However, inferior reversibility of zinc anode resulting from zinc dendrites and surface side reactions limits the practical realization of zinc-ion batteries. Herein, we develop a thin but robust polymeric artificial interphase to enhance reversibility of zinc anode. The grafted maleic anhydride groups in the polymer structure restrain the detrimental reactions through selective zinc-ion penetration and homogenize ion distribution, leading to a smooth electrode surface after plating-stripping processes. Consequently, the coated zinc anode shows excellent stability with a long-term symmetric cell lifespan (>3,000 h at 3 mA??cm???2) and maintains capacity retention of 80% after 2,500 cycles, paired with a manganese oxide cathode. This study provides a facile fabrication process and accessible analysis methods to rationalize the development of high-performance zinc-ion batteries

Understanding medical students’ empathy based on Enneagram personality types

Purpose High self-awareness can promote communication and empathy. The Enneagram is a well-known personality tool to enhance self-awareness. We evaluated differences in empathy among medical students using the Enneagram typology. Methods This cross-sectional study included first and second grade students at the Inje University College of Medicine. The Jefferson Scale of Empathy was used to measure empathy and the Korean Enneagram Personality Type Indicator was used for examining personality characteristics. Empathy scores were analyzed according to the Triads, Hornevian group, Harmonic group, and each Enneagram type. Results The Instinctive triad, the Withdrawns, and the Positive outlook group were the most common, and the Feeling triad, the Assertives, and the Emotional realness group were the least common. Students in the Feeling triad and the Dutifuls had higher compassionate care (CC) scores as compared to their counterparts. Type 2 and 6 students showed the two highest empathy and CC scores. The empathy score of type 3 students was the lowest. Type 7 had the lowest CC score but the highest perspective taking score. Conclusion These differences in empathy according to Enneagram personality types can be applied to medical education to maintain and improve medical students’ empathy

A fabrication of stable lithium metal anodes using HF scavenging films

A stable lithium metal anode was fabricated using a functional lithiophilic thin film polymer. The functional film captures HF impurities in the electrolyte and provides a fluorine-rich surface. In addition, the lithiophilic properties and in situ formed stable solid-electrolyte-interphase layer induced uniform lithium electrodeposition and exhibited outstanding cell performance in both liquid and solid electrolytes.11Nsciescopu

Compressive Strain Sensing Using 3D Graphene Oxide Hydrogels

Graphene-based hydrogels are characterized by nanoporous structure and tailored properties, which can provide routes to a number of lightweight, multifunctional applications. Here, we report a class of three-dimensionally robust, compression-sensitive, lightweight graphene oxide hydrogel (GOH) with tailored porosity, surface area and electrical conductivity controlled by chemical modification, graphene oxide (GO)concentration and degree of reduction. Ethylene and diamine and ascorbic acid were used as crosslinking agents. The results showed the electrical conductive network formed by crosslinked graphene platelets are densified when subjected to compression, and their response to strains vary with GOH porosity and pore size. This piezoresitive mechanism enables GOH to serve as strain sensors capable of measuring. Copyright 2015. Used by the Society of the Advancement of Material and Process Engineering with permission

Layering Charged Polymers Enable Highly Integrated High‐Capacity Battery Anodes

High-capacity anode materials are promising candidates for increasing the energy density of lithium (Li)-ion batteries due to their high theoretical capacities. However, a rapid capacity fading due to the huge volume changes during charge-discharge cycles limits practical applications. Herein, a layering-charged polymeric binder is introduced that can effectively integrate high-capacity anodes using a strong yet reversible Coulomb interaction and enriched hydrogen bonding. The charged polymeric binder builds a dynamically charge-directed network on the active materials with high versatility and efficiently dissipates the electrode stress with its excellent mechanical properties. In addition, poly(ethylene glycol) (PEG) moieties of the charged binder offer a fast Li-ion conduction pathway that can form an ultra-thick silicon oxide (SiOx)-based electrode (≈10.2 mAh cm−2) without compromising the reversible specific capacity and promote effective charge interaction as a mechanical modulator. Such an unprecedented charge-directed binder provides insights into the rational design of a binder for high-capacity anodes.11Nsciescopu

Layering Charged Polymers Enable Highly Integrated High-Capacity Battery Anodes

High-capacity anode materials are promising candidates for increasing the energy density of lithium (Li)-ion batteries due to their high theoretical capacities. However, a rapid capacity fading due to the huge volume changes during charge-discharge cycles limits practical applications. Herein, a layering-charged polymeric binder is introduced that can effectively integrate high-capacity anodes using a strong yet reversible Coulomb interaction and enriched hydrogen bonding. The charged polymeric binder builds a dynamically charge-directed network on the active materials with high versatility and efficiently dissipates the electrode stress with its excellent mechanical properties. In addition, poly(ethylene glycol) (PEG) moieties of the charged binder offer a fast Li-ion conduction pathway that can form an ultra-thick silicon oxide (SiOx)-based electrode (≈10.2 mAh cm−2) without compromising the reversible specific capacity and promote effective charge interaction as a mechanical modulator. Such an unprecedented charge-directed binder provides insights into the rational design of a binder for high-capacity anodes.11Nsciescopu

Effect of reductive cyclic carbonate additives and linear carbonate cosolvents on fast chargeability of LiNi0.6Co0.2Mn0.2O2/graphite cells

For application to electric vehicles, the fast charging of lithium-ion batteries is required. However, lithium-ion batteries are faced with undesirable Li plating causing the capacity fading with low Coulombic efficiency at high charge rates. Here, we present the effects of solid electrolyte interphase structures of the graphite anode and linear carbonate solvents on fast charging capability of LiNi0.6Co0.2Mn0.2O2/graphite full cells. To control the nature of the interfacial layer on the graphite anode affecting the Li plating behavior, we exploit three kinds of additives, ethylene carbonate, fluoroethylene carbonate and vinylene carbonate, as anode solid electrolyte interphase formers. In addition, the effect of ethyl methyl carbonate and dimethyl carbonate on the solvation and transport of high concentrations of Li ions de-intercalated from the LiNi0.6Co0.2Mn0.2O2 cathode in a full cell at high charge rates is explored in fluoroethylene carbonate-based electrolytes. Our investigation reveals that the combination of fluoroethylene carbonate and dimethyl carbonate in the electrolyte enables fast-charging LiNi0.6Co0.2Mn0.2O2/graphite full cells showing the excellent capacity retention of 79% after 1000 cycles at a high charging current density of 6 mA cm−2, corresponding to 2C, and a discharge rate of 1C without Li plating on the graphite anode

All-impurities Scavenging, Safe Separators with Functional Metal-Organic-Frameworks for High-Energy-Density Li-Ion Battery

Li-ion batteries (LIBs) have wide applications owing to their high-energy density and stable cycle characteristics. Nevertheless, with the rapid expansion of electric vehicle market, issues such as explosion of LIBs and the need to secure a longer driving distance have emerged. In this work, functional metal-organic frameworks (MOFs) are introduced as a separator in LIBs, in which a highly heat-resistant polymer separator is fabricated through electrospinning. The MOFs can scavenge impurities (including gas, water, and hydrofluoric acid) that positively affect battery performance and safety. The multi-functional separator suppresses salt decomposition when a nickel-rich cathode is operated at high voltage and high temperature through it. This delays the deterioration of the cathode interface and results in a superb cycle stability with 75% retention even in the presence of 500 ppm of water in the electrolytes. In addition, the pouch cell is manufactured by enlarging the separator, and the degree of electrode swelling due to gas generation and interface degradation in the pouch state is alleviated to 50% or less. These findings highlight the necessity of scavenging impurities to maintain excellent performance and provides the development direction of functional separators in LIBs

A Three-Dimensional Nano-web Scaffold of Ferroelectric Beta-PVDF Fibers for Lithium Metal Plating and Stripping

Lithium metal has been considered as an anode material to improve energy densities of lithium chemistry-based rechargeable batteries (that is to say, lithium metal batteries or LMBs). Higher capacities and cell voltages are ensured by replacing practically used anode materials such as graphite with lithium metal. However, lithium metal as the LMB anode material has been challenged by its dendritic growth, electrolyte decomposition on its fresh surface, and its serious volumetric change. To address the problems of lithium metal anodes, herein, we guided and facilitated lithium ion transport along a spontaneously polarized and highly dielectric material. A three-dimensional web of nanodiameter fibers of ferroelectric beta-phase polyvinylidene fluoride (beta-PVDF) was loaded on a copper foil by electrospinning (PVDF#Cu). The electric field applied between the nozzle and target copper foil forced the dipoles of PVDF to be oriented centro-asymmetrically and then the beta structure induced ferroelectric polarization. Three-fold benefits of the ferroelectric nano-web architecture guaranteed the plating/stripping reversibility especially at high rates: (1) three-dimensional scaffold to accommodate the volume change of lithium metal during plating and stripping, (2) electrolyte channels between fibers to allow lithium ions to move, and (3) ferroelectrically polarized or negatively charged surface of beta-PVDF fibers to encourage lithium ion hopping along the surface. Resultantly, the beta-PVDF web architecture drove dense and integrated growth of lithium metal within its structure. The kinetic benefit expected from the ferroelectric lithium ion transport of beta-PVDF as well as the porous architecture of PVDF#Cu was realized in a cell of LFP as a cathode and lithium-plated PVDF#Cu as an anode. Excellent plating/stripping reversibility along repeated cycles was successfully demonstrated in the cell even at a high current such as 2.3 mA cm(-2), which was not obtained by the nonferroelectric polymer layer