A Large Scalable and Low‐Cost Sulfur/Nitrogen Dual‐Doped Hard Carbon as the Negative Electrode Material for High‐Performance Potassium‐Ion Batteries

Abstract

Among the negative electrode materials for potassium ion batteries, carbon is very promising because of its low cost and environmental benignity. However, the relatively low storage capacity and sluggish kinetics still hinder its practical application. Herein, a large scalable sulfur/nitrogen dual‐doped hard carbon is prepared via a facile pyrolysis process with low‐cost sulfur and polyacrylonitrile as precursors. The dual‐doped hard carbon exhibits hierarchical structure, abundant defects, and functional groups. The material delivers a high reversible potassium storage capacity and excellent rate performance. In particular, a high reversible capacity of 213.7 and 144.9 mA h g−1 can be retained over 500 cycles at 0.1 A g−1 and 1200 cycles at 3 A g−1, respectively, demonstrating remarkable cycle stability at both low and high rates, superior to the other carbon materials reported for potassium storage, to the best of the authors' knowledge. Structure and kinetics studies suggest that the dual‐doping enhances the potassium diffusion and storage, profiting from the formation of a hierarchical structure, introduction of defects, and generation of increased graphitic and pyridinic N sites. This study demonstrates that a facile and scalable pyrolysis strategy is effective to realize hierarchical structure design and heteroatom doping of carbon, to achieve excellent potassium storage performance.

Rational Design of Core@shell Structured CoSx@Cu2MoS4 Hybridized MoS2/N,S‐Codoped Graphene as Advanced Electrocatalyst for Water Splitting and Zn‐Air Battery

“…A typical XPS survey spectrum of the CoS x @Cu 2 MoS 4 ‐MoS 2 /NSG hybrid in Figure S11 in the Supporting Information showed a list of peaks relating to respective binding energies of Co2p, Cu2p, Mo3d, S2p, N1s, and C1s at 779.9, 932.8, 232.2, 166.5, and 398.7 eV, respectively. From C1s core level spectrum, in addition to binding energies of CC (284.6 eV), CO (286.5 eV), CO (287.2 eV), and OCO (289.2 eV) derived from the specific features of reduced graphene oxide, it also clearly indicated successful N and S doping into the graphitic skeleton with the binding energies of CN (285.4 eV) and CSC (284.0 eV) ( Figure 3 a) . This was further demonstrated by N1s and S2p core level spectra in Figures b,c, respectively.…”

“…Figure 7 a displayed LSV curve in the range from 0.3 to 1.9 V with bifunctional catalytic behaviors of the CoS x @Cu 2 MoS 4 ‐MoS 2 /NSG toward ORR and OER. The potential difference (Δ E ) between ORR and OER (Δ E = E J = 10 − E half , where E J = 10 is the potential value to achieve a current response of 10 mA cm −2 for OER and E half is the half‐wave potential of ORR) was found to be 0.694 V. This result was much smaller than that of many reported metal‐based catalysts, demonstrating promising bifunctional ORR and OER activities of the CoS x @Cu 2 MoS 4 ‐MoS 2 /NSG for Zn‐air battery application. In order to realize its practicability, CoS x @Cu 2 MoS 4 ‐MoS 2 /NSG was used as a cathodic catalyst (1.6 mg cm −2 ) for constructing Zn‐air battery device (Figure b).…”

Metal chalcogenides for potassium storage

“…Inspired by the existing pioneering work involving graphite, tremendous efforts have been devoted to this area of research. To date, several categories of materials are verified to be effective for potassium storage in terms of anodes, including carbon nanophases (eg, hard carbon, graphite, and heteroatom‐doped carbon), alloy‐type (semi‐)metals (eg, Sn, Bi, Sb, and P), metal oxides (eg, Nb 2 O 5 , SnO 2 , Fe x O, and Sb 2 MoO 6 )/sulfides (eg, MoS 2 , VS 2 , SnS 2 , and Sb 2 S 3 ) and phosphides (eg, FeP, CoP, Sn 4 P 3 , and GeP 5 ), sylvite compounds (eg, KVPO 4 F, K 2 V 3 O 8 , KTi 2 (PO 4 ) 3 , and K x Mn y O z ), metal‐organic composites (eg, Co 3 [Co(CN) 6 ] 2 and K 1.81 Ni[Fe(CN) 6 ] 0.97 ·0.086H 2 O), and pure organic polymers (eg, boronic ester, fluorinated covalent triazine, perylene‐tetracarboxylate, perylenetetracarboxylic diimide, azobenzene‐4,4′‐dicarboxylic acid potassium, 2,2′‐azobis[2‐methylpropionitrile], and poly[pyrene‐ co ‐benzothiadiazole]). However, most carbon materials barely deliver reversible capacities exceeding 300 mAh g −1 despite their excellent electrochemical cyclability.…”

Improved potassium ion storage performance of graphite by atomic layer deposition of aluminum oxide coatings

“…Pristine graphene, graphitic carbon nanocage, N‐doped graphene, boron‐doped graphene, P, O dual‐doped graphene, etc with enlarged crystal layer gap and more reaction sites could enhance K + storage performance. Soft carbon, hard carbon, and hard‐soft composite carbon with optimized nanostructures also showed an improved PIBs anode.…”