Boron-, nitrogen-, aluminum-, and phosphorus-doped graphite electrodes for non-lithium ion batteries

Intercalation of Li⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺, Zn²⁺, and Al³⁺ ions into B-, N-, Al-, and P-doped graphite has been studied using density functional theory calculations. While the intercalation of Li⁺, K⁺, and Ca²⁺ ions into graphite is thermodynamically favorable, that of Na⁺, Mg²⁺, Zn²⁺, and Al³⁺ ions into graphite is unfavorable. When doped in the form of graphitic structure, B, Al, and P dopants significantly stabilize the ion-intercalated graphite compounds. As a result, Na⁺ ions that are unable to intercalate into graphite can intercalate into B-, Al-, and P-doped graphite. The electron transfer from B, Al, and P dopants to host C atoms reinforces the ion–graphene electrostatic interaction, enhancing the thermodynamic driving force for ion intercalation. The catalytic activity of the dopant to promote the ion intercalation increases in the order of N < B < P < Al, which is associated with the electronegativity of the dopant.