Abstract
Potassium‐ion batteries (PIBs) are considered as promising candidates for lithium‐ion batteries due to the abundant reserve and lower cost of K resources. However, K+ exhibits a larger radius than that of Li+, which may impede the intercalation of K+ into the electrode, thus resulting in poor cycling stability of PIBs. Here, an N/O dual‐doped hard carbon (NOHC) is constructed by carbonizing the renewable piths of sorghum stalks. As a PIB anode, NOHC presents a high reversible capacity (304.6 mAh g−1 at 0.1 A g−1 after 100 cycles) and superior cycling stability (189.5 mAh g−1 at 1 A g−1 after 5000 cycles). The impressive electrochemical performances can be ascribed to the super‐stable porous structure, expanded interlayer space, and N/O dual‐doping. More importantly, the NOHC can be prepared in large scale in a concise way, showing great potential for commercialization applications. This work may impel the development of low‐cost and sustainable carbon‐based materials for PIBs and other advanced energy storage devices.
Highlights
Introduction layer spacingIt has been demonstrated that the introduction of heteroatoms (N, O, P, S, F, etc.) is an effective approach to Lithium-ion batteries (LIBs) are the most common energy adjust interlayer distance.[17]
A series of a N/O dual-doped carbon network for potassium-ion batteries (PIBs), which exhibits energy storage devices has received great attentions as prom- a capacity of 260 mAh g−1 at 0.1 A g−1 after 100 cycles and a ising alternatives to LIBs, such as magnesium-ion batteries, capacity of 160 mAh g−1 after 4000 cycles at 1 A g−1.[17]. He et al
The initial discharge and charge capacities are 627.3 and 318.1 mAh g−1 for N/O dual-doped hard carbons (NOHCs)-600, 976.4 and 398.2 mAh g−1 for NOHC-800, and 778.4 and 254.6 mAh g−1 for NOHC-1000 at a current density of 0.1 A g−1, with a corresponding initial Coulombic efficiencies (CE) of 50.7%, 40.8%, and 32.7%, respectively
Summary
Three typical peaks at 531.77, 532.70, and 533.64 eV are observed in O 1s spectra, corresponding to C O, C OH/C O C, and COOH groups, respectively.[32,40] the presence of C OH hydroxyl group could improve the surface wettability.[40,41] As a result, high specific surface area can be fully utilized and the K+ storage is promoted.[40,41] The N 1s XPS spectrum of NOHC800 (see Figure 3d) can be fitted into three peaks at 398.15, 400.05, and 401.91 eV, which are related to pyridinic N (19.7%), pyrrolic N (56.2%), and graphitic N (24.1%), respectively.[42] A certain amount of N can afford more electrochemical active sites and enhance the conductivity by accelerating the ion/electron diffusion.[38] with rising temperature, the contents of C increase in NOHCs, while the N and O contents decrease gradually (see Figure 3e). The contents of pyridinic N and pyrrolic N reduce, whereas the graphitic N content increases apparently (see Figure 3f)
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