Liquid‐State Templates for Constructing B, N, Co‐Doping Porous Carbons with a Boosting of Potassium‐Ion Storage Performance

Abstract

lithium resources greatly limits the large-scale promotion and application of LIBs. [4-7] As possible candidates, sodium and potassium ion systems are receiving intense attention owing to their low cost and high natural abundant resources. [8-14] Particularly, recent studies indicated that compared with sodium ions, potassium ions exhibited more merits on the basis of its similar intercalation behaviors in graphite and closer redox potential (K/K + , −2.92 V) with Li ions. [15,16] Therefore, potassium ion energy storage system, including potassium ion batteries (PIBs) and potassium ion hybrid capacitors (PIHCs) demonstrates a promising prospect in practical applications, and the corresponding studying upsurge is just beginning. [16,17] In the exploration of potassium electrode materials, porous carbons are highly preferable owing to their elastic framework, rich porosity and good conductivity, which can efficiently alleviate the volume expansion caused by the larger K + (ionic radius, 1.38 Å) intercalation and provides more pathways for fast K + diffusion. [16,18-21] So far, many carbons with various porosities have been successfully used in potassium ion system, exhibiting excellent electrochemical performance. [22,23] In current strategies of producing porous carbons, the template method is considered as one ideal way owing to its good control of porous architectures. [16] Presently, solid-phase templates including salts, SiO 2 nanospheres, and metal foams have been applied widely in constructing porous carbons. [24-26] Besides, gas-phase templates such as gas bubbles and foams are also popular due to their facile and economical process. [23,27] Despite a great process, several challenges still remain. For example, salt or gas-phase templates are simple and scalable, but always create large-size pores, giving rise to the severe decrease of the volumetric capacitance. [28] The nanosized solid-phase templates can lead to small-size pores, but are hindered by high cost and the probability of contamination from the removal process. [29] Therefore, the development of a scalable and green template strategy for the synthesis of carbons with rich nanosized porosity is important. Notably, in contrast to the success of solid-and gas-phase templates, liquid-state templates are rarely reported so far, which might be Template-assistant design and fabrication of porous carbon electrode materials has experienced great progress throughout the past decades and yielded lots of successes via various gas or solid state templates. Nevertheless, liquid-state templates are rather rare in preparing porous carbon materials to date. In this work, melting B 2 O 3 beads are used as both templates and a B dopant, leading to unique B, N co-doping hierarchically porous carbons containing a "bubble pool"-like skeleton built of interconnected carbon nanobubbles. Notably, an interesting amending effect of doped B atoms on the N-doped carbon network can be identified for the first time, which creates a "paddy field"-like hybrid microstructure wi...

Water‐Soluble Salt Template‐Assisted Anchor of Hollow FeS2 Nanoparticle Inside 3D Carbon Skeleton to Achieve Fast Potassium‐Ion Storage

“…Generally, the total charge transfer process can be divided into faradaic reaction‐controlled and diffusion‐controlled process by the following equation: i = av b , where a and b are adjustable parameters. [ 63 ] A b ‐value close to 0.5 represents a typical diffusion‐controlled process, while a b ‐value close to 1.0 represents an ideal faradaic reaction‐controlled process. Usually, the reaction‐controlled charge storage intrinsically more quickly, while the diffusion‐controlled charge storage is more sluggish.…”

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

“…NH 4 HB 4 O 7 ·3H 2 O was used as a dopant to generate B 2 O 3 and NH 3 in the heat treatment to simultaneously introduce the doping of B and N atoms in the porous carbons (BN‐PC, Figure 9A). 76 The HRTEM image (Figure 9B) showed several sp 3 defective carbon areas in the continuous sp 2 graphitic carbon conductive network. Based on the results of XPS spectra, the possible formation process of C‐N‐B bonds in BN‐PC was proposed by the model in Figure 9C, where the N element was first doped to the carbon skeleton, and the dopant B atom bonded to the N atom and carbon skeleton.…”

“…The B‐doped graphene with B 4 C 28 structure (doping concentration of 12.5 at%) was studied to be metallic with good electronic conductivity and possess a large specific capacity of 546 mA h/g with the maximum eight K + adsorptions to graphene layer to form K 8 B 4 C 28 , although without further experimental investigations of this structure. However, B‐doped porous carbon materials were successfully synthesized by a liquid‐state template method using B 2 O 3 as dopant and the elevated specific capacity of carbon materials after B doping was verified 76 …”

“…HRTEM, high‐resolution transmission electron microscope; PIBs, potassium‐ion batteries. Reproduced with permission: Copyright 2021, Wiley‐VCH 76 …”

Perspective on Carbon Anode Materials for K+ Storage: Balancing the Intercalation‐Controlled and Surface‐Driven Behavior

“…The strategies include: 1) enhancing specific surface area by introducing nanopores or designing various nanostructures, [ 41–52 ] 2) producing tremendous intrinsic carbon layer defects, [ 36,53 ] and 3) incorporating doped heteroatom functional groups. [ 39,40,54–97 ] Some representative electrochemical results in terms of capacity, cycle stability, and rate performances are summarized in Figure 3e.…”