<p>Zinc–manganese batteries contain iron, copper, and black mass containing zinc, manganese, and graphite. Hydrometallurgical processing of the black mass of batteries in alkali solutions allows for the selective extraction of zinc, and the transfer of manganese and graphite into an insoluble residue. However, hetaerolite ZnMn₂O₄ is formed during the operation of the batteries, an alkali-insoluble compound, reducing the efficiency of the alkaline leaching process of zinc. The paper considers a method of thermal treatment of the black mass of batteries with the addition of sodium peroxide Na₂O₂, which allows destroying the hetaerolite and increasing zinc extraction during subsequent alkaline leaching. The regularities of alkaline leaching of samples of the initial and sintered black mass are studied. The influence of thermal treatment conditions (temperature 300–600&#xa0;℃, Na₂O₂ consumption 12.5–50%), leaching temperature (25–80&#xa0;℃), initial NaOH concentration (100–440&#xa0;g/dm³), and duration of the operation (1–40&#xa0;min) on zinc extraction is established. The phase composition of the samples of the initial and sintered black mass, as well as the cake after leaching is estimated. The recommended optimal parameters for the sintering and leaching processes allow zinc extraction at a level of 68%. The values of the apparent activation energy of ZnO dissolution from the initial and sintered mass were calculated to be 19.3 and 14.7&#xa0;kJ/mol, respectively, as well as the apparent orders of zinc leaching reactions from the samples of the initial and sintered black mass, equal to 0.96 and 0.6, respectively.</p> Graphical Abstract <p></p>