Search

Search for novel cathode materials is of current interest. Among them, Li2MnSiO4 shows promise as a cathode material in the poly-anion family due to its structural diversity, abundance, low cost, and high theoretical capacity (330 mA h g−1). However, it suffers from low electronic and ionic conductivity, limited reversible capacity, and poor cycling performance. To overcome these deficiencies, using a global structure search at high pressure, we find a new phase with a group symmetry of Cc, which is the ground-state at a pressure of 50 Gpa, and remains stable when the pressure is released. This new phase exhibits many attractive features such as a high energy density of 612 Wh kg−1 with a reversible capacity of 170 mA h g−1, a high average discharge voltage of 3.6 V, improved electronic conductivity, coexistence of anionic and cationic redox, and superior ionic conductivity due to unique diffusion channels with reduced steric hindrance and coulombic repulsion. All these features endow the new phase of Li2MnSiO4 with potential for use as a high performance cathode material.

Na-ion batteries, as an alternative to Li-ion batteries, have gained increasing attention due to the abundance of sodium and its low cost. In the present work, we prepare a 3D porous carbon material by inserting hexagonal carbon rings into sp3 C–C bonds in a previously established 3D-(4,4) lattice, termed tC24. Ab initio calculations uncover that not only is tC24 thermally, dynamically and mechanically stable, but it also exhibits a unique electronic band structure with two topological nodal surfaces traversing through the whole Brillouin zone. More importantly, tC24 is the first all carbon topological nodal-surface semimetal for Na-ion batteries, exhibiting a high theoretical capacity of 232.65 mA h g−1, a low diffusion energy barrier for Na ions, an appropriate average voltage of 0.54 V and a negligible volume change (∼0.94%) during charging/discharging operation. These properties provide tC24 with a potentially long cycling life when used as an anode material for Na-ion batteries.

Motivated by the advantages of inherent high electronic conductivity and ordered porosity of topological semimetal monoclinic C16 (m-C16), we explore its possible use as a lithium-ion battery anode material. Using state-of-the-art theoretical calculations, we show that the m-C16 structure has a high specific capacity of 558 mA h g−1, a low Li ion diffusion energy barrier of 0.25 eV, and a small volume change of 3.6% during charging/discharging operation. The overall performance of m-C16 is superior to that of topological semimetal body-centered orthorhombic C16 (bco-C16) reported recently with corresponding values of 558 mA h g−1, 0.53 eV and 13.4%. This study further expands the family of porous topological carbon for high-performance anode materials going beyond the commercially used graphite.

Due to the structural failure of layered CoO2, there has been considerable effort to improve the reversible capacity of commercial LiCoO2 cathode materials. Using a global structural search, we have discovered a rutile-like CoO2 phase as the ground state at 50 GPa. The material is thermally, mechanically and dynamically stable, even after removing the pressure. We show that, when lithiated, this LiCoO2 material can serve as an improved cathode material for Li-ion batteries. Its many advantages include good structural stability against transition metal migration and oxygen loss, one-dimensional channels for Li ion diffusion with variable energy barriers (0.36–0.86 eV), enhanced ionic mobility, and good intrinsic electronic conductivity brought about by its metallic band structure. Furthermore, with a voltage platform of 3.2–3.8 V, it provides better stability against conventional carbonate solvents than conventional layered cathode materials (>4.0 V). All these features demonstrate that the non-layered CoO2 phase synthesized at high pressure would be a promising cathode material, providing a performance beyond that of the currently used layered phase.