High selectivity, capacity and stability for electrochemical lithium extraction on boron-doped HMnO by tailoring lattice constant and intercalation energy.

A sustainable supply of lithium from salt-lake brines is necessary due to the surge in demand of the lithium-battery market. However, the presence of coexisting ions, particularly Na, poses a significant challenge due to the similarities in charge, electronic structure, and hydrated size. The electrochemical system with manganese (Mn)-based lithium-ion (Li) sieves electrodes is a promising method for Li recovery, but often suffers from geometric configuration distortion, which reduces their selectivity and capacity. In this work, we developed a boron-modified HMnO (HMO-B) material for Li extraction through hybrid capacitive deionization (HCDI) intercalation. Characterizations and theoretical calculations verified that the formation of the BO bond reduces the lattice constant, significantly inhibiting the Jahn-Teller distortion of Mn, thereby stabilizing the crystal structure. The transformation of Mn to Mn effectively prevents Mn dissolution during the electro-de-intercalation process. B doping narrows the lattice spacing and increases the intercalation energy difference between Li and Na. Consequently, HMO-B exhibits an outstanding Li/Na selectivity of 1211.68. The reduction in interface impedance improves current efficiency, while the increase in specific surface area provides abundant recognition sites for Li, enhancing Li intercalation performance from 14 mg g day for HMO to 34.94 mg g h for HMO-B. Additionally, Mn dissolution reduces from 7 % for HMO to 1.13 % for HMO-B after 10 cycles. This work holds substantial practical value for the selective Li extraction from salt lake brine and is anticipated to provide a stable Li supply for the burgeoning new energy industry.