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Electrode and interface design for lithium/sodium – selenium batteries Aboonasr Shiraz, Mohammad Hossein

Abstract

Electric vehicles (EVs) have become a global trend to decrease fossil fuel use in transportation and reduce greenhouse gas emissions. The battery technology is one of the most critical parts of the wide adoption of EVs. The rapidly developing market for the emerging plug-in hybrid vehicle and mobile electronics has prompted the urgent need for rechargeable batteries with high energy density. Although considerable progress has been made in lithium-ion batteries (LIBs), the overall energy density of LIBs is limited by the low capacity of current cathode materials. Therefore, cathode materials with high specific capacity have been extensively investigated. Selenium (Se) has drawn much more attention to be a good candidate in lithium/sodium batteries. Preparation of high-performance electrodes with tremendous capacity and durability over long cycling is the most challenging task. In this thesis, microporous carbon (MPC) derived from metal-organic frameworks (MOF) and polyvinylidene fluoride (PVDF) has found to be a suitable matrix to confine selenium and prepare Se-based cathode (MPC/Se), demonstrating high electrochemical performance in terms of cyclability, specific capacity, energy density, and rate capability. The polyselenides dissolution phenomenon in the Se-based batteries (shuttle effect), which was one of the most challenging parts, has been remarkably suppressed by using the optimized carbonization temperature (800°C), composite selenium content (50 wt.%), and electrode selenium loading (2 mg cm-²). The optimal MPC/Se cathode delivered a reversible capacity of 530 mAh g-¹ at a current density of 0.1 C in Li-Se batteries. Further studies showed that by the addition of a 3 vol.% fluoroethylene carbonate (FEC) additive to the electrolyte, a stable solid electrolyte interface (SEI) layer is formed on both cathode and the metal anode, enhancing the electrochemical properties of Li/Na-Se batteries and removing the shuttle effect issue. Further cathode development was conducted using the atomic layer deposition (ALD) technique to coat the electrode. The studies revealed that the five cycles coating of Alucone and Al₂O₃ could powerfully tackle polyselenide's dissolution into the electrolyte, resulting in high capacity and long life for Li/Na-Se batteries.

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Attribution-NonCommercial-NoDerivatives 4.0 International