A positive electrode with thoughtful diffusion capacitance for solid flexible supercapacitor: N-6 doped porous carbon shell coated Cu doped Mn Co LDO core

The suitable proportion of diffusion contribution during the electrochemical process could influence the electrochemical performance of electrode materials. An effective method is that tuning the diffusion reaction contribution via doping heteroatom, introducing defects or surface modification. In this work, a unique core-shell structure material Cu-Mn-Co LDO-C is obtained. Benefitting from Cu pre-doped into MnCo LDO, large amount of oxygen vacancies is introduced to enhance electrochemical performance; N-6 doped porous carbon shell protects Cu-Mn-Co LDO core and improves electrochemical performance of Cu-Mn-Co LDO-C further. In addition, doping Cu broadens potential window of Cu-Mn-Co LDO-C surprisingly. Cu-Mn-Co LDO-C presents 5028.7 mF cm−2 at a current density of 1 mA cm−2 with a facilely reached potential window of 0–0.65 V finally, and retains 73.4 % diffusion contribution at a scan rate of 1 mV s−1, 18.3 % at 100 mV s−1. After 10,000 cycles at 2 mA cm−2, Cu-Mn-Co LDO-C keeps 90.3 % of initial capacitance. Using Cu-Mn-Co LDO-C as positive and Fe3O4-C as negative to fabricate a solid flexible asymmetrical supercapacitor (SAS), this SAS presents a considerable energy density that attribute to the high working potential of positive Cu-Mn-Co LDO-C. SAS could working stably at a potential window of 0–2.2 V, and presents the highest energy density 243.1 μWh cm−2 at a power density of 2.8 mW cm−2, remains 203.0 μWh cm−2 at the highest power density of 55.4 mW cm−2. A hand ring that was assembled by three SAS which contacted in series could light a highest rated voltage white LED more than 10 min. As a result, Cu-Mn-Co LDO-C is an ideal candidate for flexible positive electrode in the field of smart, portable energy storage.