Direct-contact prelithiation (PL) is a facile, practical, and scalable method to overcome the first-cycle loss and large volume expansion issues for silicon anode (with 30 wt % Si loading) material, and a detailed study is absent. Here, an understanding of direct-contact PL as a function of the PL time, and the effects of externally applied pressure (weight), microstructure, and operating temperature have been studied. The impact of PL on the Si–C electrode surfaces has been analyzed by electrochemical techniques and different microstructural analyses. The solid electrolyte interface (SEI) layer thickness increases with the increase in PL time and decreases after 2 min of PL time. The ideal PL time was found to be between 15 (PL-15) and 30 (PL-30) min with 83.5 and 97.3% initial Coulombic efficiency (ICE), respectively, for 20 g of externally applied weight. The PL-15 and PL-30 cells showed better cyclic stability than PL-0 (without prelithiation), with more than 90% capacity retention after 500 cycles at 1 A g–1 current density. The discharge capacities for PL-15 and PL-30 have been observed as highest at 45 °C operating temperature with limited cyclability. We propose here a synchronization strategy in prelithiation time, pressure, and temperature to achieve excellent cell performance.

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Developing room-temperature sodium−sulfur (RT Na−S) batteries with a high-sulfur-containing cathode and a relatively low amount of electrolyte is the prime factor for implementation of these batteries into the energy storage market. However, it is extremely challenging to achieve stable, long-term cyclability while utilizing a high-sulfur-loaded cathode, since strong adhesion of active material with the current collector should be maintained during charge−discharge. Here, we report manganese dioxide nanoarray-decorated carbon cloth conformally wrapped with sodium−alginate nanofibers (abbreviated as CC@MnO 2 @Naalg) as a robust cathode current collector, which not only restricts the gradual dissolution of polysulfides but also offers good adhesion to the active material. To facilitate ion-transport kinetics, a liquidphase Na 2 S 6 catholyte is used as an active material. At 1C (C = 1672 mA g −1 ), the catholyte-infiltrated CC@MnO 2 @Na-alg electrode scaffold, with a high sulfur loading of 3.4 mg cm −2 , exhibits a remarkable capacity retention of 94.4% after 1000 cycles. Comprehensive theoretical studies reveal the possible anchoring sites in sodium−alginate for the confinement of the polysulfide species.

Investment in stocks and expected return from such investment always comes with risk. Financial economists and financial analysts have been working for years to find ways to minimize risk. What all financial analysts believe is that creating well-diversified portfolio can minimize risk. Fama (1976), Elton & Grubber (1977), Evans & Archer (1968) and many other analysts have shown that well-diversified portfolios can actually minimize risk and have suggested the minimum number of stocks required for a well-diversified portfolio. In this paper portfolio diversification theory is applied for the investors investing in the Karachi Stock Exchange. Fifteen (15) securities were randomly selected and equally weighted portfolios were created. Standard Deviations for all portfolios were calculated and the results were analyzed. The study concluded that a portfolio of 10 stocks can diversify away significant amount of risk.

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