All-Solid-State Na–O₂ Batteries with Long Cycle Performance

Abstract

All-solid-state sodium oxygen (ASS Na–O2) batteries have received interest due to their higher theoretical energy density, lower cost, higher safety level, and nonflammability compared with liquid electrolyte and Li–O2 batteries. Here, we report the application of carbon nanotube (CNT) and Ru/CNT cathodes, succinonitrile with a NaClO4 (SN + NaClO4) interlayer, a Na3Zr2Si2PO12 (NZSP) solid electrolyte, and a Na film anode for ASS Na–O2 batteries. Results showed that the SN + NaClO4 interlayer plays a crucial role in the tri-conductive cathode, ionic conductivity, and interfacial charge transfer kinetics between the Ru/CNT cathode and NZSP electrolyte. The ASS Na–O2 batteries with Ru/CNT and SN + NaClO4 tri-conductive cathodes exhibited a long cycling performance of 100 cycles (current density of 100 mA g–1 and limited capacity of 500 mA h g–1), a discharge capacity of 11 034 mA h g–1 (current density of 100 mA g–1), and a small overpotential gap of 1.4 V. These values were better than those for CNT and SN + NaClO4 tri-conductive cathodes (maximum discharge capacity of 2413 mA h g–1, 27 cycles, and potential gap of 1.7 V) with a Na2O2 discharge product. Ex situ analysis showed that the Ru/CNT cathode achieved superior reversibility deposition and decomposition of the Na2O2 discharge product. Therefore, the ASS Na–O2 battery system is safe and stable for energy storage applications.

Battery Performance Amelioration by Introducing a Conducive Mixed Electrolyte in Rechargeable Mg–O2 Batteries

“…On the contrary, the MgO, which is formed as the final discharge product, is decomposed to form O 2 (OER) during the charging phase. The Ru NPs embedded in the CNT matrix help to improve the electrocatalytic activity of metal–O 2 batteries . However, after a long cycling time, these results show that the discharge products like MgO or MgO 2 , created during the discharge process, were not completely deformed during recharging cycles.…”

“…The Ru NPs embedded in the CNT matrix help to improve the electrocatalytic activity of metal−O 2 batteries. 7 However, after a long cycling time, these results show that the discharge products like MgO or MgO 2 , created during the discharge process, were not completely deformed during recharging cycles. This could be a valid reason behind the underperformance of the CSE-based Ru/CNT cathodes compared to the CME.…”

“…Hence, the global need for a feasible energy storage technology accompanied by high specific energy and volumetric energy density has propelled its interest in metal–air batteries (batteries that run mainly using oxygen or air). − Being an efficient derivative of its predecessor, rechargeable lithium–air batteries with air cathode have been widely researched to mitigate the demerits of LIBs in the past 10 years. , The high theoretical energy density of 3456 Wh kg –1 for a typical Li–O 2 battery (2Li + O 2 ⇌ Li 2 O 2 , theoretical cell voltage 2.96 V vs standard hydrogen electrode (SHE)) has attracted much attention . Therefore, with such boundless capability, cheaper and more abundant metals like magnesium, sodium, zinc, aluminum, and potassium have also significantly gained interest. − Among these metals, magnesium has its virtues as low redox potential (−2.37 V vs SHE), compatibility with air-based cathodes, natural abundance (2.08% in the earth’s crust), cost-effectiveness, eco-friendliness, sustainability, and most importantly, and Mg suppresses dendrite formation. − The theoretical cell voltages of secondary Mg–O 2 batteries with aprotic electrolytes are 2.95 V vs Mg 2+ /Mg 0 for 2Mg 2+ + O 2 + 4e – ↔ 2MgO and 2.91 V vs Mg 2+ /Mg 0 for Mg 2+ + O 2 + 2e – ↔ MgO 2 . Regarding the theoretical energy density, a Mg–O 2 battery can produce 3905 and 2751 Wh kg –1 , depending upon the formation of MgO and MgO 2 , respectively .…”

“…20 In this work, to tackle the poor cyclic performance and high overpotential, we have designed a conducive mixed electrolyte Apart from the electrolyte modification, we chose Ru nanoparticle (NP)-decorated multiwalled carbon nanotubes (Ru/CNT) as an electrocatalyst for the gas cathode, which could expedite the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) kinetics to improve the Mg− O 2 battery performances. 7,25 The highly catalytic Ru NPs catalyze the ORR and OER, and the interconnected network of the one-dimensional (1D) CNTs with huge active surface area scaffold the Ru NPs and act as the highway for electron transport. With the CME (2 M Mg(NO 3 ) 2 + 1 M of Mg(TFSI) 2 in diglyme) and Ru/CNT catalytic cathode, the Mg−O 2 batteries delivered a deep discharge capacity of 25 793 mAh g −1 at a current density of 500 mA g −1 and within the voltage window of 0.5−3.5 V, manifested an unprecedented cycle life of 65 at the current density of 100 mA g −1 , a curtailing capacity of 500 mAh g −1 , and a charging− discharging overpotential of 1.4 V.…”