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Improvement in the rate capability needs to be addressed for utilization of a Si anode in high-power Li-ion batteries. Regarding the rate capability, its improvement by Si–C nanocomposites seems to be somewhat saturated, thus indicating that the other method should be tried for further enhancement of the rate capability. Here, we introduce Si nanoparticles uniformly coated with nanometer-thick polyacrylonitrile (PAN) with better wettability to liquid electrolytes and minimizing electronic resistance, which might result from a thick PAN coating: the effective contact surface area made by the contact of Si nanoparticles and liquid electrolyte is increased for larger Li-ion current, leading to ultrafast rate capability retaining 62% of the 0.2C rate discharge capacity at 100C. In addition, a strong adhesive property of PAN provides highly mechanically robust Si anodes for multielectrode-stacked flexible lithium-ion batteries, which show no physical damage after 30 000 bending cycles with a bending radius of ...

Here, we show that the capacity retention rate and Coulombic efficiency of silicon/graphite composite anodes are improved significantly when the electrode particles are strongly bonded to the current collector with the aid of a polymeric adhesive interlayer. The improved adhesion between the electrode film and the current collector, which was confirmed by the scratch test, effectively suppresses the evolution of the interphase as well as the charge-transfer resistance of the electrode during cycling. Thus, it can be concluded that maintaining a good electrical contact between the active material and the current collector is crucial for developing high-performance Si anodes for lithium-ion batteries.

High-voltage cathode materials have gained much attention as one of the promising electrode materials to increase power density of lithium ion batteries by raising the working voltage. However, the use of such high-voltage cathode materials is still challenging, because their working voltage is close to the electrochemical oxidation potential of organic electrolyte used in lithium ion batteries. In this work, we demonstrated that simultaneous fluorination of LiNi 0.5 Mn 1.5 O 4 (LNMO) particles as well as conductive agent in the electrode could significantly improve the electrochemical stability of LNMO cathode. The resulting electrode showed better cycle performance both at room temperature and elevated temperature compared to both bare LNMO electrode and the electrode with only LNMO fluorinated. These results showed that direct fluorination of high voltage cathode can reduce the side reaction of high voltage cathode electrode with the electrolyte, thereby stabilizing the surface of carbon black as well as that of high voltage cathode material.

Anode materials including graphite are known to be thermodynamically unstable toward organic solvents and salts and become covered by a passivating film (Solid electrolyte interphase, SEI) which retards the kinetics because of the high electronic resistivity. To achieve high performance in lithium ion batteries (LIBs), the SEIs are required to be mechanically stable during repeated cycling and possess highly ion-conductive. In this work, we have investigated an artificial pre-SEI on graphite electrode using a polymer binder containing lithium (i.e., a Li-copolymer of isobutylene and maleic anhydride, Li-PIMA) and its effect on the anode performances. During charging, the polymer binder with the functional group (–COOLi) acts as a SEI component, reducing the electrolyte decomposition and providing a stable passivating layer for the favorable penetration of lithium ions. Hence, by using the binder containing lithium, we have been able to obtain the first Coulombic efficiency of 84.2% (compared to 77.2% obtained using polyvinylidene fluoride as the binder) and a capacity retention of 99% after 100 cycles. The results of our study demonstrate that binder containing lithium we have used is a favorable candidate for the development of high-performance LIBs.

A 2H-MoS2 (H=hexagonal) ultrathin nanomesh with high defect generation and large porosity is demonstrated to improving electrochemical performance, including in lithium-ion batteries (LIBs) and the hydrogen evolution reaction (HER), with the aid of a 3D reduced graphene oxide (RGO) scaffold as fast electron and ion channels. The 3D defect-rich MoS2 nanomesh/RGO foam (Dr-MoS2 Nm/RGO) can be easily obtained through a one-pot cobalt acetate/graphene oxide (GO) co-assisted hydrothermal reaction, in which GO, cobalt and acetate ions are co-morphology-controlling agents and defect inducers. As an anode material for LIBs, Dr-MoS2 Nm/RGO has only a 9% capacity decay at a 10 C discharge rate versus 0.2 C with stable cyclability at the optimized composition (5 wt% RGO to MoS2 and 2 mol% Co to Mo), and significantly achieves 810 mA h g(-1) at a high current density of 9.46 A g(-1) over at least 150 cycles. Moreover, Dr-MoS2 Nm/RGO exhibits superior activity for the HER with an overpotential as low as 80 mV and a Tafel slope of about 36 mV per decade. In contrast to the MoS2 nanosheet/RGO (MoS2 Ns/RGO), which is synthesized in the absence of cobalt ions, Dr-MoS2 Nm/RGO provides high interconnectivity for efficient lithium-ion transport, and rich defects as electrochemically active sites. DFT is used to prove the existence of rich defects due to anion replacement to become a Co-Mo-S atomic structure, releasing inert basal planes to active sites.

Morphology-controlled MoS2 nanosheets were successfully synthesized with the aid of graphene/acid coexistence by a one-pot hydrothermal method. The ultrathin MoS2 nanosheets were self-assembled into a cockscomb-like structure with an exposed (100) facet on graphene sheets, which is in strong contrast to large aggregate MoS2 plates grown freely on graphene sheets without acetic acid. The ultrathin MoS2 nanosheets displayed excellent rate performance for Li storage (709 mAh·g(-1) capacity at 8320 mA·g(-1) discharging rate) and superior charge/discharge cyclability.

Fatigue crack growth and closure behavior under random loadings in 7475-T7351 aluminum alloy is investigated by performing various random loading tests. The effects of random load spectrum, history length, and stress ratio on the crack growth and closure behavior are discussed. The crack opening load was automatically determined by using the normalized-extended ASTM method. The crack opening load is nearly constant during a random loading block and is mainly governed by the largest load cycle in a random load history, irrespective of random load spectrum and history length. The fatigue crack growth under random loading can be well described by the crack closure concept.

In this work, we report novel composite gel polymer electrolyte for lithium-ion polymer batteries. As the lithium ion sources of single ion conductor, the core–shell structured SiO2(Li+) particles with uniform spherical shape are synthesized and used as functional fillers in composite gel polymer electrolytes. We show that our material, based on the incorporation of core–shell structured SiO2(Li+) particles into a gel polymer matrix, acts as a very effective polymer electrolyte for lithium-ion polymer batteries. Keywords: Core–shell particle, Functional filler, Lithium batteries, Composite polymer electrolyte, Silica

Problems related to tremendous volume changes associated with cycling and the low electron conductivity and ion diffusivity of Si represent major obstacles to its use in high-capacity anodes for lithium ion batteries. We have developed a group IVA based nanotube heterostructure array, consisting of a high-capacity Si inner layer and a highly conductive Ge outer layer, to yield both favorable mechanics and kinetics in battery applications. This type of Si/Ge double-layered nanotube array electrode exhibits improved electrochemical performances over the analogous homogeneous Si system, including stable capacity retention (85% after 50 cycles) and doubled capacity at a 3C rate. These results stem from reduced maximum hoop strain in the nanotubes, supported by theoretical mechanics modeling, and lowered activation energy barrier for Li diffusion. This electrode technology creates opportunities in the development of group IVA nanotube heterostructures for next generation lithium ion batteries.

The effects of surface-modified carbon black induced by UV/ozone and triethylenetetramine on the microstructure and electrochemical properties of ink-jet-printed LiCoO 2 electrodes for lithium ion batteries are observed. The dispersion properties of surface-modified carbon black and LiCoO 2 ink are evaluated using particle size distribution measurements, surface pressure calculations, and scanning electron microscopy. Modifications to the surface of carbon black result in improved dispersion properties, which in turn enhance the compactness and homogeneity of the microstructure of ink-jet-printed LiCoO 2 electrodes compared to those printed with as-received carbon black. Electrochemical experiments indicate that LiCoO 2 electrodes ink-jet-printed with surface-modified carbon black exhibit improved initial specific discharge capacities compared to those printed with as-received carbon black due to the better electrical contact between the carbon black and the LiCoO 2 , as evidenced by the analysis of the area-specific impedance of the electrode as a function of the depth of discharge.

Silicon is a promising candidate for electrodes in lithium ion batteries due to its large theoretical energy density. Poor capacity retention, caused by pulverization of Si during cycling, frustrates its practical application. We have developed a nanostructured form of silicon, consisting of arrays of sealed, tubular geometries that is capable of accommodating large volume changes associated with lithiation in battery applications. Such electrodes exhibit high initial Coulombic efficiencies (i.e., >85%) and stable capacity-retention (>80% after 50 cycles), due to an unusual, underlying mechanics that is dominated by free surfaces. This physics is manifested by a strongly anisotropic expansion in which 400% volumetric increases are accomplished with only relatively small (

Developing electrode materials with high-energy densities is important for the development of lithium-ion batteries. Here, we demonstrate a mesoporous molybdenum dioxide material with abnormal lithium-storage sites, which exhibits a discharge capacity of 1,814 mAh g−1 for the first cycle, more than twice its theoretical value, and maintains its initial capacity after 50 cycles. Contrary to previous reports, we find that a mechanism for the high and reversible lithium-storage capacity of the mesoporous molybdenum dioxide electrode is not based on a conversion reaction. Insight into the electrochemical results, obtained by in situ X-ray absorption, scanning transmission electron microscopy analysis combined with electron energy loss spectroscopy and computational modelling indicates that the nanoscale pore engineering of this transition metal oxide enables an unexpected electrochemical mass storage reaction mechanism, and may provide a strategy for the design of cation storage materials for battery systems., Electrode materials with high energy density are important for the development of Li-ion batteries. Here, the authors report a molybdenum dioxide anode with abnormal lithium storage sites, exhibiting a discharge capacity twice its theoretical value by utilizing two different storage mechanisms.

Silicon is receiving discernable attention as an active material for next generation lithium-ion battery anodes because of its unparalleled gravimetric capacity. However, the large volume change of silicon over charge–discharge cycles weakens its competitiveness in the volumetric energy density and cycle life. Here we report direct graphene growth over silicon nanoparticles without silicon carbide formation. The graphene layers anchored onto the silicon surface accommodate the volume expansion of silicon via a sliding process between adjacent graphene layers. When paired with a commercial lithium cobalt oxide cathode, the silicon carbide-free graphene coating allows the full cell to reach volumetric energy densities of 972 and 700 Wh l−1 at first and 200th cycle, respectively, 1.8 and 1.5 times higher than those of current commercial lithium-ion batteries. This observation suggests that two-dimensional layered structure of graphene and its silicon carbide-free integration with silicon can serve as a prototype in advancing silicon anodes to commercially viable technology., The volume expansion of silicon is a big problem in lithium-ion batteries with silicon anodes. Here, the authors report direct graphene growth on silicon nanoparticles, which effectively mitigates the problem, leading to excellent electrochemical performance.

We report a synthetic scheme for preparing a SnO2–Sn–carbon triad inverse opal porous material using the controlled sintering of Sn precursor-infiltrated polystyrene (PS) nanobead films. Because the uniform PS nanobead film, which can be converted into carbon via a sintering step, uptakes the precursor solution, the carbon can be uniformly distributed throughout the Sn-based anode material. Moreover, the partial carbonization of the PS nanobeads under a controlled Ar/oxygen environment not only produces a composite material with an inverse opal-like porous nanostructure but also converts the Sn precursor/PS into a SnO2–Sn–C triad electrode.

MoS2 nanosheets are prepared from a neutralized aqueous solution of graphene oxide, (NH4)6Mo7O24, and thiourea followed by hydrothermal treatment (autoclave, 240 °C, 12 h) in the presence of glacial acetic acid as suppressor for growth in c-axis direction and NaOH as reducing agent.

Germanium holds great potential as an anode material for lithium ion batteries due to its large theoretical energy density and excellent intrinsic properties related to its kinetics associated with lithium and electrons. However, the problem related to the tremendous volume change of Ge during cycling is the dominant obstacle for its practical use. The previous research has focused on the improvement in mechanics associated with lithium without consideration of the kinetics. In this study, we demonstrate that the configuration engineering of the Ge electrode enables the improvement in kinetics as well as favorable mechanics. Two types of Ge inverse opal structures with porous walls and dense walls were prepared using a confined convective assembly method and by adjusting Ge deposition parameters in a chemical vapor deposition system. The Ge inverse opal electrode with porous walls shows much improved electrochemical performances, especially cycle performance and rate capability, than the electrode with dense walls. These improvements are attributed to a large free surface, which offers a facile strain relaxation pathway and a large lithium flux from the electrolyte to the active material.

Si nanowires (SiNWs)–carbon nanofibers (CNFs) branched structures with variation in carbon densities were synthesized. SiNWs with critical density of CNFs show the best electrochemical performance, which is attributed to increase in free volume around the SiNWs as well as a buffering role of the branched CNFs against large volumetric change during cycling.