There is little known about the transport behavior of ions in electrolyte solutions at very high concentrations and there is currently no one widely-accepted theory or equation to describe it over the whole concentration range. In this work, the ionic conductivity (κ) of lithium salts in aqueous and non-aqueous electrolyte solutions have been measured as a function of concentration (C) and have been fitted to known theoretical and empirical equations. A new, isothermal, semi-empirical equation based on free volume theory:C] where V o and V f are the occupied and unoccupied "free" volume, respectively, gives better fit over the whole concentration range than the known equations. V f and V 0 2,φ , the apparent molar volume of the salt, were calculated from density measurements and it is found that free volume decreases with concentration in both the aqueous and non-aqueous solutions over the whole range. We hypothesize that the changes to transport properties in solution with concentration are caused by structural changes that switches the conductivity mechanism from vehicular to a Grotthuss-type or a mixture of both. We, for the first time, correlate the origin of C max , the concentration of highest conductivity, to the eutectic composition in the salt-solvent phase diagram.

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Increasing the energy density of Li-ion batteries is very crucial for the success of electric vehicles, grid-scale energy storage, and nextgeneration consumer electronics. One popular approach is to incrementally increase the capacity of the graphite anode by integrating silicon into composites with capacities between 500 and 1000 mAh/g as a transient and practical alternative to the more-challenging, silicon-only anodes. In this work, we have calculated the percentage of improvement in the capacity of silicon:graphite composites and their impact on energy density of Li-ion full cell. We have used the Design of Experiment method to optimize composites using data from half cells, and it is found that 16% improvements in practical energy density of Li-ion full cells can be achieved using 15 to 25 wt% of silicon. However, full-cell assembly and testing of these composites using LiNi 0.5 Mn 0.5 Co 0.5 O 2 cathode have proven to be challenging and composites with no more than 10 wt% silicon were tested giving 63% capacity retention of 95 mAh/g at only 50 cycles. The work demonstrates that introducing even the smallest amount of silicon into graphite anodes is still a challenge and to overcome that improvements to the different components of the Li-ion battery are required.

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Driven by the demands for high energy density and safe Li batteries, designing a high-performance, all-solid-state Li battery (ASSLB) has been the focus of much attention in the past few decades. As a promising solid electrolyte (SE) candidate, the garnet family has been extensively studied, mainly due to its high ionic conductivity and stability toward reaction with elemental Li. Recently, several works have realized garnet-based ASSLBs at the lab scale. The aim of this Focus Review is to provide a brief description of the garnet structure, its optimization for ionic conductivity, and synthesis methods for bulk, thin-film, and composite garnet SEs, as well as a detailed comparison of garnet-based ASSLBs in terms of cell design and testing considerations. This work is targeted to provide a fundamental insight into the latest achievements in the field that can pave the way to realize practical garnet-based ASSLBs.

The conventional polyvinylidene fluoride (PVDF) binder works well with the graphite anode, but when combined with silicon in composites to increase the energy density of Li-ion batteries, it results in severe capacity fade. Herein, by using scanning electron microscopy and energy-dispersive X-ray spectroscopy analyses, we reveal that this failure stems from the loss of connectivity between the silicon (or its agglomerates), graphite, and PVDF binder because of the mechanical stresses experienced during battery cycling. More importantly, we reveal for the first time that the PVDF binder undergoes chemical decomposition during the cycling of not only the composite but also the Si-only or even graphite-only electrodes despite the excellent battery performance of the latter. Through X-ray photoemission electron microscopy and X-ray photoelectron spectroscopy techniques, LiF was identified as the predominant decomposition product. We show that the distribution of LiF in the electrodes due to the differences in the interactions between PVDF and either Si or graphite could correlate with the performance of the battery. This study shows that the most suitable binder for the composite electrode is a polymer with a good chemical interaction with both graphite and silicon.

All-solid-state batteries continue to grow as an alternative to replace the traditional liquid-based ones not only because they provide increased safety but also higher power and energy densities. However, current solid-state electrolytes are either ceramics that are brittle but highly conducting (e.g. Li0.33La0.55TiO3, LLTO) or polymer electrolytes that are poorly conducting but form flexible films with desired mechanical properties (e.g. Poly(ethylene oxide):Lithium bis(trifluoromethanesulfonyl)imide, PEO:LiTFSI). In this work, we have developed quaternary composite solid-state electrolytes (CSEs) to combine the benefits of the two types along with Succinonitrile (SN) as a solid plasticizer. CSEs with different compositions have been fully characterized over the whole compositional range. Guided by neural network simulation results it has been found that a polymer-rich CSE film gives the optimal ionic conductivity (>10−3 S cm−1 at 55 °C) and mechanical properties (Tensile strength of 16.1 MPa; Elongation-at-break of 2360%). Our solid-state coin-type cell which employs our in-house made cathode shows good cycling performance at C/20 and 55 °C maintaining specific discharge capacity at 143.2 mAh g−1 after 30 cycles. This new approach of formulating quaternary CSEs is proven to give the best combination of properties and should be universal and be applied to other CSEs with different chemistry.

We demonstrated a simple method for the device design of a staggered herringbone micromixer (SHM) using numerical simulation. By correlating the simulated concentrations with channel length, we obtained a series of concentration versus channel length profiles, and used mixing completion length L(m) as the only parameter to evaluate the performance of device structure on mixing. Fluorescence quenching experiments were subsequently conducted to verify the optimized SHM structure for a specific application. Good agreement was found between the optimization and the experimental data. Since L(m) is straightforward, easily defined and calculated parameter for characterization of mixing performance, this method for designing micromixers is simple and effective for practical applications.