Role of Nitrogen-Doped Graphene for Improved High-Capacity Potassium Ion Battery Anodes

Abstract

Potassium is an earth abundant alternative to lithium for rechargeable batteries, but a critical limitation in potassium ion battery anodes is the low capacity of KC8 graphite intercalation compounds in comparison to conventional LiC6. Here we demonstrate that nitrogen doping of few-layered graphene can increase the storage capacity of potassium from a theoretical maximum of 278 mAh/g in graphite to over 350 mAh/g, competitive with anode capacity in commercial lithium-ion batteries and the highest reported anode capacity so far for potassium ion batteries. Control studies distinguish the importance of nitrogen dopant sites as opposed to sp3 carbon defect sites to achieve the improved performance, which also enables > 6X increase in rate performance of doped versus undoped materials. Finally, in-situ Raman spectroscopy studies elucidate the staging sequence for doped and undoped materials and demonstrate the mechanism of the observed capacity enhancement to be correlated with distributed storage at local nitrogen sites in a staged KC8 compound. This study demonstrates a pathway to overcome the limitations of graphitic carbons for anodes in potassium ion batteries by atomically precise engineering of nanomaterials.

Recent Progress and Perspective in Electrode Materials for K‐Ion Batteries

“…[48][49][50][51] Most of these materials exhibit remarkable capacities, even in excess of the theoretical capacity of graphite. N-doped and F-doped graphenes are demonstrated to deliver close to 350 mA h g −1 .…”

“…N-doped and F-doped graphenes are demonstrated to deliver close to 350 mA h g −1 . [48,50] Their rate capability and capacity retention are fair ( Figure 3d. [26] Chen et al [43] reported a N-doped carbon material with high rate capability using nongraphitic carbon: 154 mA h g −1 at a 72 C rate.…”

K‐Ion Batteries Based on a P2‐Type K0.6CoO2 Cathode

“…[3,4,[10][11][12][13][14][15][16][17][18][19][20] For example, Eftekhari demonstrated that Prussian blue can reversibly store K ions in a nonaqueous electrolyte system. [5] Later, the amorphous phase of FePO 4 as well as organic materials were also suggested as cathodes for KIBs.…”

Constructing Multichannel Carbon Fibers as Freestanding Anodes for Potassium‐Ion Battery with High Capacity and Long Cycle Life

“…[28,31,32] Among them, relative ratios of N-6 and N-5 are 40.5% and 39.4%, respectively. [17,29,30] N-Q, located inside the carbon plane, can noticeably enhance the electronic conductivity of carbons. [33] Especially, N-6 can induce the local electron deficiency, which has an extremely high affinity for the electron from the adjacent K atom, facilitating the interaction of active materials and K atom.…”

“…[10,11] And, the rate performance needs to be improved at high current densities because of the poor diffusion kinetics of K + . Such as, hard carbon microspheres fabricated by carbonizationetching strategy or hydrothermal reaction combined with pyrolysis method, [14,15] hard-soft composite carbon prepared by combination of hydrothermal reaction with pyrolysis method, [16] graphene prepared with a chemical vapor deposition (CVD) method, [17] graphene aerogel fabricated through Hummers' process combined with hydrothermal treatment process, [18] and carbon nanofiber prepared by a modified oxidative template assembly route following with annealing process. Such as, hard carbon microspheres fabricated by carbonizationetching strategy or hydrothermal reaction combined with pyrolysis method, [14,15] hard-soft composite carbon prepared by combination of hydrothermal reaction with pyrolysis method, [16] graphene prepared with a chemical vapor deposition (CVD) method, [17] graphene aerogel fabricated through Hummers' process combined with hydrothermal treatment process, [18] and carbon nanofiber prepared by a modified oxidative template assembly route following with annealing process.…”