Graphitic Nanocarbon with Engineered Defects for High‐Performance Potassium‐Ion Battery Anodes

Abstract

The application of graphite anodes in potassium-ion batteries (KIB) is limited by the large variation in lattice volume and the low diffusion coefficient of potassium ions during (de)potassiation. This study demonstrates nitrogendoped, defect-rich graphitic nanocarbons (GNCs) as high-performance KIB anodes. The GNCs with controllable defect densities are synthesized by annealing an ethylenediaminetetraacetic acid nickel coordination compound. The GNCs show better performance than the previously reported thin-walled graphitic carbonaceous materials such as carbon nanocages and nanotubes. In particular, the GNC prepared at 600 °C shows a stabilized capacity of 280 mAh g −1 at 50 mA g −1 , robust rate capability, and long cycling life due to its high-nitrogen-doping, short-range-ordered, defect-rich graphitic structure. A high capacity of 189 mAh g −1 with a long cycle life over 200 cycles is demonstrated at a current density of 200 mA g −1 . Further, it is confirmed that the potassium ion storage mechanism of GNCs is different from that of graphite using multiple characterization methods. Specifically, the GNCs with numerous defects provide more active sites for the potassiation process, which results in a final discharge product with short-range order. This study opens a new pathway for designing graphitic carbonaceous materials for KIB anodes.

A Site‐Selective Doping Strategy of Carbon Anodes with Remarkable K‐Ion Storage Capacity

“…In the initial cycles, the anodic peak at 0.7 V shifts slightly and stabilizes due to the structural re-arrangement during (de)potassiation. [23] Compared with ENDC500, ENDC700 and NDC900 electrodes show smaller areas of the CV curves (Supporting Information, Figure S12), indicating decreased reversible capacity. The galvanostatic chargedischarge (GCD) curves (Figure 4 b) demonstrate similar behavior as the CV curves.…”

“…[20][21][22] Nonetheless, the rate capability and cycling stability of graphite anode for PIB are still limited owing to the large volume variation (58 %) during (de)potassiation, the low diffusion coefficient of K-ion, and the irreversible trapping of K atoms in graphite lattices. [23][24][25][26] To compete with the LIB technology or achieve a low energy storage cost, the capacity of carbonaceous anodes of PIB should be improved to be comparable to the specific capacity of LiC 6 . For the sake of enhanced capacity of carbonaceous anodes in PIB, several parameters must be carefully controlled, including 1) the (002) lattice spacing should be made large enough for efficient (de)potassiation; [27,28] 2) the defect-induced adsorption mechanism should be engineered to enhance K-ion storage beyond the intercalation mechanism (here, defects refer to CÀC sp 3 defects, and heteroatom-doping-induced defects).…”

“…For the sake of enhanced capacity of carbonaceous anodes in PIB, several parameters must be carefully controlled, including 1) the (002) lattice spacing should be made large enough for efficient (de)potassiation; [27,28] 2) the defect-induced adsorption mechanism should be engineered to enhance K-ion storage beyond the intercalation mechanism (here, defects refer to CÀC sp 3 defects, and heteroatom-doping-induced defects). [23,24,29] Nitrogen-doping has been demonstrated as an efficient way to enhance the potassium storage capacities of carbonaceous materials owing to the increased electron negativity of defective sites for efficient adsorption of Kions. [23,30] Furthermore, edge-nitrogen (pyrrolic, and pyridinic) doping, as demonstrated by calculation and experimental study, has higher adsorption energy than sp 2 hybridized graphitic nitrogen doping.…”

“…[23,24,29] Nitrogen-doping has been demonstrated as an efficient way to enhance the potassium storage capacities of carbonaceous materials owing to the increased electron negativity of defective sites for efficient adsorption of Kions. [23,30] Furthermore, edge-nitrogen (pyrrolic, and pyridinic) doping, as demonstrated by calculation and experimental study, has higher adsorption energy than sp 2 hybridized graphitic nitrogen doping. [31,32] However, the state-of-art pyrolysis methods for preparing nitrogen-doped carbons from nitrogen-abundant organics are mostly done by trial and error approaches.…”

Defect Engineering on Electrode Materials for Rechargeable Batteries

“…Electrochemical test results showed that the prepared N‐GCNs exhibited a reversible capacity and high cycling stability. In addition, by adjusting the annealing temperature, Zhang et al prepared graphitic nanocarbons with controllable defect density of doped nitrogen and CC sp 3 and graphene layer length for potassium‐ion battery anodes . On the one hand, the production of CC sp 3 defects in graphite carbon provides a way for effective diffusion of potassium ions.…”