High selectivity, capacity and stability for electrochemical lithium extraction on boron-doped H1.6Mn1.6O4 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 H_1.6Mn_1.6O₄ (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 Mn³⁺, thereby stabilizing the crystal structure. The transformation of Mn³⁺ to Mn⁴⁺ 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^-1 day^-1 for HMO to 34.94 mg g^-1 h^-1 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.