Designing and Understanding the Superior Potassium Storage Performance of Nitrogen/Phosphorus Co‐Doped Hollow Porous Bowl‐Like Carbon Anodes

Abstract

Potassium‐ion batteries (PIBs) are promising alternatives to lithium‐ion batteries because of the advantage of abundant, low‐cost potassium resources. However, PIBs are facing a pivotal challenge to develop suitable electrode materials for efficient insertion/extraction of large‐radius potassium ions (K+). Here, a viable anode material composed of uniform, hollow porous bowl‐like hard carbon dual doped with nitrogen (N) and phosphorus (P) (denoted as N/P‐HPCB) is developed for high‐performance PIBs. With prominent merits in structure, the as‐fabricated N/P‐HPCB electrode manifests extraordinary potassium storage performance in terms of high reversible capacity (458.3 mAh g−1 after 100 cycles at 0.1 A g−1), superior rate performance (213.6 mAh g−1 at 4 A g−1), and long‐term cyclability (205.2 mAh g−1 after 1000 cycles at 2 A g−1). Density‐functional theory calculations reveal the merits of N/P dual doping in favor of facilitating the adsorption/diffusion of K+ and enhancing the electronic conductivity, guaranteeing improved capacity, and rate capability. Moreover, in situ transmission electron microscopy in conjunction with ex situ microscopy and Raman spectroscopy confirms the exceptional cycling stability originating from the excellent phase reversibility and robust structure integrity of N/P‐HPCB electrode during cycling. Overall, the findings shed light on the development of high‐performance, durable carbon anodes for advanced PIBs.

High Capacity and Fast Kinetics of Potassium-Ion Batteries Boosted by Nitrogen-Doped Mesoporous Carbon Spheres

“…With the scan rates increasing from 0.2 to 10 mV s −1 , the shapes of the CV curves occupy larger area, which illustrates the capacitive-controlled dominant characteristic (Figs. 4 a and S15, S16) [ 17 ]. Clearly, a distortion from the basic shape appears at high scan rates (more than 2 mV s −1 ) in Fig.…”

“…4 i) based on Eqs. 3 and 4 [ 17 ]. where τ is the duration of the current pulse; m B presents the mass loading of electrode active material; S stands for the geometric area of the electrode.…”

“…Nevertheless, their electrochemical behaviors are still not so satisfying. In comparison, hard carbon with higher disorder degree and larger interlayer spacing is more conducive to improving electrochemical performances [ 17 ]. For instance, in 2016, hard carbon microspheres were first synthesized as anode materials for PIBs, achieving the capacity of 262 mAh g −1 at 28 mA g −1 [ 18 ].…”

Carbon‐based anode materials for potassium‐ion batteries: From material, mechanism to performance

“…Remarkably, the ICE of PNHC materials in the potassiation/depotassiation process was improved significantly with further P doping mainly due to the decreased defective sites that contributed to the irreversible capacity. A similar configuration of N/P dual doping was conducted by Chen et al 81 …”

Magnetic Field Assisted Construction of Hollow Red P Nanospheres Confined in Hierarchical N‐Doped Carbon Nanosheets/Nanotubes 3D Framework for Efficient Potassium Storage

“…In this way, superb 3D ionic/electronic conductive networks can be guaranteed for rapid ion/electron transport in all directions and enhanced comprehensive electrochemical properties, particularly at large current densities. [32][33][34][35] It is therefore of particular significance yet urgent to explore more efficient methodologies to purposefully fabricate hierarchical H-P/heteroatomdoped carbon composites for high-performance PIBs.…”