A rechargeable all-solid-state sodium peroxide (Na₂O₂) battery with low overpotential

Abstract

Na–O2 batteries have been attracting attention owing to their intrinsically high theoretical energy density. Several Na–O2 systems can produce various discharge products with different electrochemical performances. For example, sodium superoxide (NaO2) batteries have a low overpotential, and sodium peroxide (Na2O2) batteries have a high capacity. Studies of Na2O2 batteries are relatively scarce, owing to the difficulty of forming pure Na2O2 discharge products. A pure Na2O2 battery system is highly desirable for fully exploring the formation and decomposition of Na2O2 in Na–O2 batteries and evaluating their potential. This model of a Na2O2 battery should also be compatible with in situ characterization. To this end, we constructed a simple rechargeable all-solid-state Na2O2 battery. Using a nanoporous gold film as the cathode and Na–β″-Al2O3 as a solid electrolyte, we assembled a Na–O2 battery that can produce and decompose Na2O2. The all-solid-state Na–O2 battery is a simple model for conducting in situ ambient-pressure x-ray photoelectron spectroscopy (APXPS) investigations. The battery can be cycled at a low overpotential (≈450 mV). Qualitative and quantitative analyses of the APXPS and Raman results demonstrated that Na2O2 was the main discharge product and its transformation occurred during the charge and discharge periods. The operando investigation of this type of all-solid-state Na2O2 battery can help in the comprehensive exploration of the potential of Na–O2 batteries.

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

“…Compared with the Na 1s and O 1s spectra of pristine and recharged Ru/CNT cathodes, a new peak corresponding to the Na 2 O 2 at 1072.3 and 532.5 eV occurred in the fully discharged and after the 100th cycle recharged Ru/CNT cathodes. Moreover, a new peak of 536.2 eV from O 1s (Figure d) corresponding to the Na Auger peak (Na KLL) was observed . Similar results were obtained for the CNT cathode under pristine and discharge conditions, as shown in Figure S8.…”

“…Figure S7 shows the comparative study of the present work with previous investigations using different cathodes with liquid electrolyte Na−O 2 batteries (cathodes: Ru/CNT, 13 Ru−Sac/N−rGO, 19 CoB/CNT, 41 CNT, 42 GO, 43 N−CNF, 44 Pt−Ni/C, 45 and Pt−Ir/CNT 46 ), quasi-solid-state Na−O 2 batteries (cathodes: Super P, 20 SWCNT, 21 and carbon paper 22 ), and ASS Na−O 2 batteries (cathode: nanoporous gold, 24 CNT, 25 and silver polymer-composite 47 ). As result, the Ru/CNT cathode has displayed a top catalyst for NOBs.…”

“…Na–O 2 batteries have been paired with different types of electrolytes, such as liquid electrolytes, , quasi-solid-state polymer electrolytes, and hybrid solid electrolytes. − However, these batteries are not suitable due to flammability problems. All-solid-state sodium oxygen (ASS Na–O 2 ) batteries are suitable because of their high safety and nonflammable inorganic solid-state electrolytes (ISSEs) . Among all ISSEs, the Na 3 Zr 2 Si 2 PO 12 (NZSP) electrolyte is the most promising material owing to its excellent electrochemical window, high ionic conductivity, and thermal stability. ,, However, there are few studies that investigated ASS Na–O 2 batteries using a nanoporous gold film and CNT cathodes with Na−β-Al 2 O 3 and Na 3.2 Hf 2 Si 2.2 P 0.8 O 11.85 F 0.3 solid electrolytes. , For real batteries, the nanoporous gold film is not an effective cathode material.…”

“…3,5,21 However, there are few studies that investigated ASS Na−O 2 batteries using a nanoporous gold film and CNT cathodes with Na−β-Al 2 O 3 and Na 3.2 Hf 2 Si 2.2 P 0.8 O 11.85 F 0.3 solid electrolytes. 24,25 For real batteries, the nanoporous gold film is with the NZSP electrolyte has never been developed, and its design appears to be challenging. ASS Na−O 2 battery development still faces many challenges due to the sluggish direct contact between the Ru/CNT cathode and NZSP electrolyte, a major cause of short circuits, poor contact, poor cycling and rate performance, capacity loss, and reduced interfacial charge transfer kinetics (Scheme S1a).…”

Designing a Novel Electrolyte Na3.2Hf2Si2.2P0.8O11.85F0.3 for All‐Solid‐State Na‐O2 Batteries

“…Based on the above analysis, the working mechanism of the all‐solid‐state Na‐O 2 battery should be as follows ( Figure ): During the discharge process, O 2 obtained two electrons to form O 2 2− , which would react with Na + to generate Na 2 O 2 (or NaO 2 ) in an absolutely dry environment [Equations (1) and (2)]. [ 43 ] As Na 2 O 2 has a very strong ability to absorb water, thus there will have a hydration reaction once water is present [Equation (3)]. [ 44 ] And with water gradually captured on the surface of the air cathode, facilitated the reaction between H 2 O and Na 2 O 2 to form NaOH [Equation (4)].…”