Abstract Biogenic birnessite (BB), a stable form of manganese in the natural environment that originates from microbial oxidation, could be use as a starting material to prepare nanocrystalline lithium manganese oxide (LMO) by solid-state reaction for Li+ recovery. In this work, the effects of calcination temperature on Li+ adsorption density were investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, N2 adsorption–desorption isotherms, and Li+ ion sorption isotherms. An increase in calcination temperature causes a phase transformation that results in changes in crystal compositions. The formation of Li4Mn5O12 was observed at 350°C. An increase in calcination temperature from 350 to 450°C results in a decrease in the Li4Mn5O12 phase quantity, an increase in the Li2MnO3 phase quantity, and a decrease in Li+ sorption density from 4248 to 2789mmol/kg. The sorption density of Li+ is mainly affected by the Li4Mn5O12 phase content. LMOs prepared from BB show a higher Li+ sorption density compared with acidic birnessite. Phase transformation on poorly-crystalline BB at a relatively lower calcination temperature facilitates formation of the Li4Mn5O12 phase, which is the main contributor to Li+ sorption from aqueous solution.