Improved Capacity Retention of Metal Oxide Anodes in Li‐Ion Batteries: Increasing Intraparticle Electronic Conductivity through Na Inclusion in Mn3O4

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In this work, we significantly improve the cyclability of Mn3O4 anodes in Li‐ion batteries by enhancing its intraparticle electronic conductivity by doping with Na. Na was selected because, unlike typical transition‐metal dopants, it is non‐surface redox active in the potential window where the metal oxide conversion reaction occurs, and hence is more electrochemically stable during charge/discharge cycling. This work presents the first time that Na has been used as a dopant in metal oxide anodes, and the result is excellent capacity retention and rate capability. More specifically, Na was added to Mn3O4 (to achieve a Mn/Na ratio of ca. 9 : 1), impregnated onto a carbon nanotube matrix. The concentration of Na considering the entire composition of the anode material was 0.5 at %. These electrodes were able to achieve a capacity of approximately 750 mAh/g at a 1C rate, and retain over 99 % of that capacity over 500 cycles. They were also able to provide nearly twice the theoretical capacity of conventional graphite anodes under high rate discharge (609 mAh/g @ 5C), as well as achieve a higher capacity at 10C (ca. 350 mAh/g) than conventional graphite electrodes can at 1C.