Effect of Nitrogen and Cobalt Dopants for Efficient Lithium Storage: Metal‐Organic Framework‐Derived Mesoporous Carbonaceous Materials

Cobalt‐ and nitrogen‐doped mesoporous carbons are obtained from the pyrolysis at different temperatures (700 and 900 °C) of either ZIF‐67 (catena‐(bis(μ ₂ ‐2‐methylimidazolato)‐cobalt(II)) or CoNic (catena‐(bis(μ ₃ ‐nicotinato)‐bis(μ ₂ ‐nicotinato)‐(μ ₂ ‐aqua)‐di‐cobalt(II)) cobalt metal‐organic frameworks (MOFs), from Co(CO ₂ ) ₂ Pz (catena‐((μ ₂ ‐pyrazine‐2,3‐dicarboxylato)‐diaqua‐cobalt(II) dehydrate)), a linear coordination polymer (CP), and CoCO ₂ Pz (diaqua‐bis(pyrazine‐2‐carboxylato)‐cobalt(II)) a complex, followed by acid treatment. The lithium storage capacities of these materials are studied as a function of the BET‐specific surface area and N and Co contents, discussed in the context of the state of the art bibliography. Clear correlation between these three parameters with the material reversible maximum capacity is observed. The specific contribution to the total capacity of each one of these three structural features is discussed. The two highest capacity values are observed for ZIF‐67 and Co(CO ₂ ) ₂ Pz pyrolized at 700 °C, affording values of 979 and 915 mA h g ⁻¹ , respectively. The Co(CO ₂ ) ₂ Pz 700 material exhibits a high cycle stability (400 cycles) at high rate capability. Postmortem analysis of the electrodes is carried out by means of SEM microscopy, EDX, and XPS techniques, revealing promising structural stability after challenging cycling conditions. These results are discussed in terms of the accepted mechanisms for Li storage and are relevant for the design of new anodes.