Nitrogen and Fluorine Dual Doping of Soft Carbon Nanofibers as Advanced Anode for Potassium Ion Batteries

Abstract

Potassium-ion batteries (PIBs) are recognized as promising alternatives for lithium-ion batteries as the next-generation energy storage systems. However, the larger radius of K + hinders the K + insertion into the conventional carbon electrode and results in sluggish potassiation kinetics and poor cycling stability. Here, nitrogen and fluorine dual doping of soft carbon nanotubes (NFSC) anode are synthesized in one pot, achieving extraordinary electrochemical performance for PIBs. It is demonstrated that NFSC with a doping dose of 5.6 at% nitrogen and 1.3 at% fluorine together exhibits the highest reversible capacity of 238 mAh g −1 at 0.2 A g −1 and cycling stability of 186 mAh g −1 after 1000 cycles at 1 A g −1 . The extraordinary electrochemical performance can be attributed to the hollow structure, expanded interlayer distance, nitrogen and fluorine dual doping, and the binding ability of abundant defect sites. Moreover, density functional theory shows that the extra fluorine modification can dramatically enhance the conventional nitrogen doping effect and reduces the formation energy which makes a great contribution to the improvement of electrical conduction and K-ions insert. This work may promote the development of low-cost and sustainable carbonbased materials for PIBs and other advanced energy storage devices.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/smll.202101576. energy storage devices have been developed as alternatives to LIBs and received widespread attentions, such as magnesium-ion batteries, calcium-ion batteries, aluminum-ion batteries, sodium-ion batteries, and potassium-ion batteries (PIBs). [5,[8][9][10][11] Among them, PIBs are valued to be an ideal candidate due to the abundant reservation and strong interaction with conventional carbon layers to intercalate potassium species. [8,[12][13][14] Moreover, PIBs have more negative standard potential versus standard hydrogen electrode (−2.93V) than that of LIBs (−3.04V) as well as promising formation ability of potassium-graphite intercalation. [8] However, PIBs are suffering from poor rate capability and short cycling lifespan due to the larger radius of K + (1.38 Å) than that of Li + (0.76 Å), [15,16] which causes the collapse of solid electrolyte interphase (SEI) and active materials, exacerbating side reactions and extensive volumetric change during potassium insertion/extraction. [17][18][19][20] Hence, it is significant to seek alternative PIBs anode materials with favorable structural stability.Recently, great efforts have been made in the development of high-performance PIBs anode materials, such as sulfides, [18,19,21] phosphides, [22] carbonaceous, [23] and metallic materials, [24,25] etc. Among them, carbon-based materials have become one of the most promising PIBs anode due to their high conductivity, low potential platform, and structural stability in charging/ discharging process. [23,[26][27][28] In addition, due to its expanded

Modification of Porous N‐Doped Carbon with Sulfonic Acid toward High‐ICE/Capacity Anode Material for Potassium‐Ion Batteries

“…In consideration of previous researches, we can infer that if the adsorption energy of K + to the modified structure is too negative, the irreversible capture process on the surface can lead to excess stranded potassiumions and low ICE, but if it is too weak, that the ability to absorb storage will be insufficient and the increase of the potassium storage capacity is also limited. [62][63][64] For SA-NC advantageous structure, it possesses an appropriate K ions adsorption energy and charge interaction, so as to realize the improvement of the capacity and reversibility of surface adsorption storage of potassium-ions synchronously, thus optimizing the capacity performance and ICE significantly.…”

Se/N co-doped carbon nanorods for potassium ion storage

“…During the first cycle, two cathodic peaks at about 0.41 and 0.70 V can be clearly observed, which can be attributed to the formation of an irreversible electrolyte interphase (SEI). 31 No significant change is observed from the second cycle. The overlapped CV curves indicate the highly excellent electrochemical reversibility of K + intercalation/deintercalation in the SeNCRs.…”

“…[28][29][30] The existence of pyridinic-N and pyrrolic-N can enhance the adsorption of K + . 31 Furthermore, the Se 3d spectrum can be deconvoluted into three peaks (Fig. 2f and Fig.…”

Unraveling the Intercorrelation Between Micro/Mesopores and K Migration Behavior in Hard Carbon

“…Lithium‐ion batteries (LIBs), as a mature energy storage technology, have been widely applied in smart grids and portable electronic devices. [ 1–4 ] Nevertheless, low reserves, uneven distribution, and high cost of lithium resources cannot meet the rapid increasing demands for rechargeable batteries, which greatly limits the further large‐scale application of LIBs. [ 5–8 ] Therefore, it is quite important to explore alternative energy storage technologies with low cost and high electrochemical performance beyond LIBs for a sustainable development.…”