Abstract
The Lithium-Sulfur (Li-S) battery has been a subject of intensive research in recent years due to its potential to provide much higher energy density and lower cost than the current state of the art lithium-ion battery technology. In this work, we have investigated Cupric Sulfide (CuS) as a capacity-contributing conductive additive to the sulfur electrode in a Li-S battery. Galvanostatic charge/discharge cycling has been used to compare the performance of both sulfur electrodes and S:CuS hybrid electrodes with various ratios. We found that the conductive CuS additive enhanced the utilization of the sulfur cathode under a 1C rate discharge. However, under a C/10 discharge rate, S:CuS hybrid electrodes exhibited lower sulfur utilization in the first discharge and faster capacity decay in later cycles than a pure sulfur electrode due to the dissolution of CuS. The CuS dissolution is found to be the result of strong interaction between the soluble low order polysulfide Li2S3 and CuS. We identified the presence of conductive copper-containing sulfides at the cycled lithium anode surface, which may degrade the effectiveness of the passivation function of the solid-electrolyte-interphase (SEI) layer, accounting for the poor cycling performance of the S:CuS hybrid cells at low rate.
Highlights
Li-‐S battery is amongst the most promising alternatives to Li-‐ion batteries, which are approaching their limits in energy density and power capability as determined by the metal oxide based cathode and graphite based anode materials.[1]
Successful remedies to these issues generally involved the use of novel sulfurs carbon cathode architectures.3s 5 transition metal sulfides have been studied intensively as electrode materials in Li batteries in parallel to sulfur, because they serve as a good compromise between the high energy density of sulfur and better electronic conductivity in combination with a lower solubility of a metal based compound.6s 8 Since their electronic conductivities are close to or even exceeding that of graphite (1000 S cms 1), these transition metal sulfides can work as conductive fillers for sulfur electrodes as good as carbon black and further contribute additional capacity to the existing Lis S battery to partially balance its fast capacity decay.[9, 10]
It has been reported that introduction of Cu nanos crystals into sulfur electrode helps to enhance the cycIability of Lis S battery by conversion of sulfur to more electrochemically stable Cupric Sulfide (CuS),[10] which demonstrated the potential benefit of CuS inclusion for capacity retention of sulfur electrode
Summary
Li-‐S battery is amongst the most promising alternatives to Li-‐ion batteries, which are approaching their limits in energy density and power capability as determined by the metal oxide based cathode and graphite based anode materials.[1].
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