Insight into discharge of non-aqueous Li–O2 battery using a three-dimensional electrochemical lattice Boltzmann model

Abstract

Non-aqueous Li–${\text{O}}_2$${\text{O}}_2$ battery (NALiO2B) is a promising alternative to lithium-ion batteries, offering high theoretical energy density. However, its practical applications are hampered by limited understanding of the underlying mechanisms. In this study, a three-dimensional electrochemical lattice Boltzmann method is proposed to simulate the physical and electrochemical processes during NALiO2B discharge at the pore scale. The discharge performance of NALiO2B is evaluated for various electrode and electrolyte designs. It is found that the limited ${\text{O}}_2$${\text{O}}_2$ diffusion within homogeneous electrodes is the primary cause of the declined reactive electrode surface area, the intensified electrochemical reaction (or overpotential), and finally the premature battery death. This issue can be mitigated by employing the hierarchical electrode ${\text{BP}}_2$${\text{BP}}_2$ with a bi-porous structure. The large pores in ${\text{BP}}_2$${\text{BP}}_2$ improve ${\text{O}}_2$${\text{O}}_2$ transport to sustain the stable reaction process, thus enhancing the discharge capacity of NALiO2B. To further boost the rate capability of NALiO2B, ${\text{BP}}_2$${\text{BP}}_2$ is partially infiltrated with electrolyte to form the multiphase (MP) electrode, where air bubbles exist and serve as ${\text{O}}_2$${\text{O}}_2$ reservoirs. These bubbles effectively provide adequate ${\text{O}}_2$${\text{O}}_2$ to support the extensive ${\text{O}}_2$${\text{O}}_2$ consumption during the fast electrochemical reaction at high current densities. Consequently, NALiO2B with MP demonstrates the satisfactory discharge capacity and rate capability. This study provides valuable insights into the complex physics and reaction kinetics behind NALiO2B discharge, which facilitates the optimization and development of NALiO2B.