The increase in hydrogen back pressure unexpectedly enhances the overall dehydrogenation reaction rate of the 4LiBH(4) + YH(3) composite significantly. Also, argon back pressure has a similar influence on the composite. Gas back pressure seems to enhance the dehydrogenation reaction by kinetically suppressing the formation of the diborane by-product.

We report the direct observation of microstructural changes of LixSi electrode with lithium insertion. HRTEM experiments confirm that lithiated amorphous silicon forms a shell around a core made up of the unlithiated silicon and that fully lithiated silicon contains a large number of pores of which concentration increases toward the center of the particle. Chemomechanical modeling is employed in order to explain this mechanical degradation resulting from stresses in the LixSi particles with lithium insertion. Because lithiation‐induced volume expansion and pulverization are the key mechanical effects that plague the performance and lifetime of high‐capacity Si anodes in lithium‐ion batteries, our observations and chemomechanical simulation provide important mechanistic insight for the design of advanced battery materials.

This paper investigates dehydrogenation reaction behavior of the LiBH 4 −MgH 2 composite at 450 °C under various hydrogen and argon backpressure conditions. While the individual decompositions of LiBH 4 and MgH 2 simultaneously occur under 0.1 MPa H 2 , the dehydrogenation of MgH 2 into Mg first takes place and subsequent reaction between LiBH 4 and Mg into LiH and MgB 2 after an incubation period under 0.5 MPa H 2 . Under 1 MPa H 2 , enhanced dehydrogenation kinetics for the same reaction pathway as that under 0.5 MPa H 2 is obtained without the incubation period. However, the dehydrogenation reaction is significantly suppressed under 2 MPa H 2 . The formation of Li 2 B 12 H 12 as an intermediate product during dehydrogenation seems to be responsible for the incubation period. The degradation in hydrogen capacity during hydrogen sorption cycles is not prevented with the dehydrogenation under 1 MPa H 2 , which effectively suppresses the formation of Li 2 B 12 H 12 . The overall dehydrogenation behavior under argon pressure conditions is similar to that at hydrogen pressure conditions, except that under 2 MPa Ar.

We report observations of microstructural changes in {100} and {110} oriented silicon wafers during initial lithiation under relatively high current densities. Evolution of the microstructure during lithiation was found to depend on the crystallographic orientation of the silicon wafers. In {110} silicon wafers, the phase boundary between silicon and Li x Si remained flat and parallel to the surface. In contrast, lithiation of the {100} oriented substrate resulted in a complex vein-like microstructure of Li x Si in a crystalline silicon matrix. A simple calculation demonstrates that the formation of such structures is energetically unfavorable in the 2 absence of defects due to the large hydrostatic stresses that develop. However, TEM observations revealed micro-cracks in the {100} silicon wafer, which can create fast diffusion paths for lithium and contribute to the formation of a complex vein-like Li x Si network. This defect-induced microstructure can significantly affect the subsequent delithiation and following cycles, resulting in degradation of the electrode.

This article investigates the dehydrogenation behavior of the LiBH4–YH3 composite under various early-stage Ar back-pressure conditions. It is clearly observed that a minute change in early-stage atmosphere greatly affects the overall dehydrogenation reaction of the composite. Free boron and Li2B12H12 start to form in turn as the partial dehydrogenation products around 400 °C under static vacuum or low Ar back pressure. The formation of Li2B12H12 greatly increases the activation energy for the dehydrogenation reaction between LiBH4 and YH3 into LiH and YB4, hence significantly retarding the reaction. The formation of B just slightly increases the incubation period of the reaction. The formation of Li2B12H12 is effectively suppressed by initially applying Ar back pressure above 0.1 MPa.

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This study demonstrates the application of Si/C composite fibers as anode materials for all-solid-state lithium-ion batteries. Using polyacrylonitrile as the carbon precursor, Si/C fibers were prepared through electrospinning and subsequent heat-treating processes. To investigate the correlation between fiber diameter and electrochemical performance, we prepared three electrodes (A, B, C), containing Si/C fibers with ∼2 μm, ∼1 μm and ∼0.1 μm diameters, respectively. Our results revealed that although the composition of all three electrodes was nearly the same, the Si/C fiber based electrodes exhibited better capacity retention when their fiber diameters were smaller. Normalized to the total mass of electrode composite, the solid-state half-cell prepared with the smallest diameter (∼0.1 μm) Si/C fibers achieved a reversible specific capacity of ∼700 mAh g −1 (normalized to electrode mass) over 70 cycles. We believe that this report can serve as an informative approach toward the utilization of electrospun Si/C fibers as anode materials for all-solid-state lithium-ion batteries. Lithium-ion batteries (LIBs) have widely been used as portable energy storage devices owing to their great reversibility, long cycle life and high power output without memory effect.1,2 However, current LIBs utilizing conventional organic liquid electrolytes still have significant safety risks, such as operational instability at elevated temperatures, leakage of hazardous solvents and ignition by external damages.3-6 To overcome these safety risks, the development of the all-solid-state lithium-ion battery (SLIB) has attracted considerable attention. [3][4][5][6][7][8][9][10][11] In the SLIB configuration, a highly Li-ion conductive solid-state electrolyte (SSE) layer is deployed between positive and negative electrodes in place of the organic liquid electrolytes typically used in LIBs. This replacement of the liquid electrolyte with a highly conductive ceramic material is expected to improve both the SLIB's thermal and mechanical stabilities.To date, graphite has been extensively used as an anode material in LIBs; however, its limited capacity (372 mAh g −1 ) has been regarded as a drawback to achieving higher energy density LIBs. Silicon is considered to be a promising anode material alternative to graphite due to its large theoretical capacity (3,579 mAh g −1 ), low cost and high earth abundance.9,11-17 To achieve such a high capacity, Si inevitably undergoes a massive volume expansion/contraction process when alloying/de-alloying with Li. 18,19 Since the repeated volume changes of Si particles during cycling causes cracking, pulverization and rapid capacity fading brought on by the electrochemical isolation of active materials, it is believed that an effective accommodation of this Si volume change is essential for achieving acceptable capacity retention in these anodes. 20One effective strategy to accommodate the extreme volume changes of Si is to limit its extent of alloying with Li by introducing resilient additives into the electro...

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