Open Access

Simon Fleischmann, Aura Tolosa, Marco Zeiger, Benjamin Kruner, Nicolas J. Peter, Ingrid Grobelsek, Antje Quade, Angela Kruth, Volker Presser

• Atomic layer deposition has proven to be a particularly attractive approach for decorating mesoporous carbon substrates with redox active metal oxides for electrochemical energy storage. This study, for the first time, capitalizes on the cyclic character of atomic layer deposition to obtain a highly conformal and atomically controlled decoration of carbon onions with alternating stacks of vanadia and titania. The addition of 25 mass% TiO2 leads to an expansion of the VO2 unit cell, thus greatly enhancing lithium intercalation capacity and kinetics. Electrochemical characterization revealed ultrahigh discharge capacity of up to 382 mAh[middle dot]g-1 of the composite electrode (554 mAh[middle dot]g-1 per metal oxide) with an impressive capacity retention of 82 mAh[middle dot]g-1 (120 mAh[middle dot]g-1 per metal oxide) at a high discharge rate of 20 A[middle dot]g-1 or 52 C. Rigorous stability benchmarking showed superior stability over 3,000 cycles when discharging to a reduced potential of -1.8 V vs. carbon. These capacity values are among the highest reported for any metal oxide system, while in addition, supercapacitor-like power performance and longevity are achieved. On a device level, high specific energy and power of up to 110 Wh[middle dot]kg-1 and 6 kW[middle dot]kg-1, respectively, were achieved when employing the hybrid material as anode versus activated carbon cathode.