Understanding Structure–Property Relationships under Experimental Conditions for the Optimization of Lithium‐Ion Capacitor Anodes based on All‐Carbon‐Composite Materials

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The nanoscale combination of a conductive carbon and a carbon‐based material with abundant heteroatoms for battery electrodes is a method to overcome the limitation that the latter has high affinity to alkali metal ions but low electronic conductivity. The synthetic protocol and the individual ratios and structures are important aspects influencing the properties of such multifunctional compounds. Their interplay is, herein, investigated by infiltration of a porous ZnO‐templated carbon (ZTC) with nitrogen‐rich carbon obtained by condensation of hexaazatriphenylene‐hexacarbonitrile (HAT‐CN) at 550–1000 °C. The density of lithiophilic sites can be controlled by HAT‐CN content and condensation temperature. Lithium storage properties are significantly improved in comparison with those of the individual compounds and their physical mixtures. Depending on the uniformity of the formed composite, loading ratio and condensation temperature have different influence. Most stable operation at high capacity per used monomer is achieved with a slowly dried composite with an HAT‐CN:ZTC mass ratio of 4:1, condensed at 550 °C, providing more than 400 mAh g−1 discharge capacity at 0.1 A g−1 and a capacity retention of 72% after 100 cycles of operation at 0.5 A g−1 due to the homogeneity of the composite and high content of lithiophilic sites.