The effect of CO2 contamination in rechargeable non-aqueous sodium–air batteries

Abstract

Metal–air batteries have higher theoretical specific energies than existing rechargeable batteries including Li-ion batteries. Among metal–air batteries, the Na–O2 battery has gained much attention due to its low discharge/charge overpotentials (∼100 mV) at relatively high current densities (0.2 mA/cm2), high electrical energy efficiency (90%), high theoretical energy density, and low cost. However, there is no information reported regarding the effect of CO2 contamination in non-aqueous Na–air batteries. Density functional theory has, here, been applied to study the effect of low concentrations of CO2 contamination on NaO2 and Na2O2 growth/depletion reaction pathways and overpotentials. This was done on step surfaces of discharge products in non-aqueous Na–air batteries. Adsorption energies of CO2 at various nucleation sites for both step surfaces were determined, and results revealed that CO2 preferentially binds at the step valley sites of (001) NaO2 and 11¯00 Na2O2 surfaces with binding energies of −0.65 eV and −2.67 eV, respectively. CO2 blocks the step nucleation site and influences the reaction pathways and overpotentials due to carbonate formation. The discharge electrochemical overpotential increases remarkably from 0.14 V to 0.30 V and from 0.69 V to 1.26 V for NaO2 and Na2O2 surfaces, respectively. CO2 contamination is thus drastically impeding the growth/depletion mechanism pathways and increases the overpotentials of the surface reaction mechanism, hampering the performance of the battery. Avoiding CO2 contamination from intake of gas and electrolyte decomposition is thus critical in development of Na–air batteries.

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

“…[1][2][3] However, there are still face many challenges such as dendrite growth, electrolyte leakage, and side reaction when using traditional liquid electrolyte, which greatly affects the service life of the battery. [4][5][6] In addition, the dissolution of discharge products in liquid electrolyte also brings great challenges to the development of sodium-air batteries. All-solid-state sodium-air battery has been widely concerned by researchers because it not only inhibits the sodium dendrites growth effectively but also avoid the flammability and volatilization of liquid electrolytes.…”

Fast 3D-lithium-ion diffusion and high electronic conductivity of Li2MnSiO4 surfaces for rechargeable lithium-ion batteries

“…The DFT calculation is also a very powerful technique to predict metal-ion and metal-air batteries at bulk, surface, and interface structures emphasizing on the charge (ionic, electronic, and polaronic) transport mechanisms, thermodynamic stability, and their catalytic effect. 15,20,35,[44][45][46][47][48][49] Herein, we employed the DFT + U analysis to investigate the electronic properties, structural stability and lithium-ion diffusion pathways in the bulk and selected surface structures of the Li 2 MnSiO 4 cathode material in the rechargeable lithium-ion batteries. Detail analysis will also be given to rationalize the reason behind the superior surface conduction observed on the Li 2 MnSiO 4 (001) surface unlike the previously reported poor bulk Li 2 MnSiO 4 conductivity.…”

Boron and pyridinic nitrogen-doped graphene as potential catalysts for rechargeable non-aqueous sodium–air batteries

“…In an attempt to make batteries viable for use in future transportation, there has been signicant research and development of rechargeable metal-air batteries (Li-, Na-and Zn-O 2 /air batteries). [1][2][3][4][5][6][7] A sodium-air battery (Na-O 2 ) consists of sodium metal as the anode and an air/oxygen cathode in which environmental oxygen can be used. Recently, there has been considerable interest in Na-O 2 due to its relatively high energy density and capacities, operation at low dis/charge overpotentials, high electrical energy efficiency (approximately 90%), and operation over multiple cycles with chemical reversibility comparable to that of lithium ion batteries.…”