The Promise and Challenge of Phosphorus‐Based Composites as Anode Materials for Potassium‐Ion Batteries

Abstract

Potassium-ion batteries (KIBs) are a core energy storage device that can meet the need for scalable and affordable stationary applications because they use low-cost and earth-abundant potassium. In addition, KIB shares a similar storage mechanism with current Li-ion batteries. As the key to optimizing a battery's performance, the development of high-performance electrode materials helps to increase the feasibility of KIB technology. In this sense, phosphorus-based materials (i.e., phosphorus and metal phosphide) with high theoretical capacity and low redox potential tick all the right boxes as a material of choice. A rapid glimpse at recent studies on phosphorus-based anode materials for advanced KIBs is provided, covering the synthetic methods, reaction mechanisms, electrochemical properties, and performances. In addition, several promising strategies are highlighted to address the imminent challenges faced by phosphorus-based anode materials, hoping to cast an insightful outlook for possible future direction in this field. Potassium-Ion BatteriesDedicated to the 70th anniversary of Dalian Institute of Chemical Physics, CAS

Metal chalcogenides for potassium storage

“…Even though, a few metal chalcogenides have been proven to be electrochemically active when employed for potassium storage, it does not mean that there are no scientific issues and technical hurdles before discussing the feasibility of metal chalcogenides for practical PIBs and other K‐based energy storage systems . These challenges facing current metal chalcogenide anodes can be mainly concluded as the following aspects: In most metal chalcogenides (mainly sulfides/selenides), potassium polychalcogenides are generated during the deep potassiation process (discharge voltage cutoff: 0.005 V), which may result in detrimental shuttle effects similar to those observed in Li‐S batteries.…”

“…In contrast to the standard redox potential of Na + /Na (−2.71 V vs the standard hydrogen electrode [SHE]), that of K + /K (−2.93 V vs SHE) is much lower and even comparable to the redox potential of Li + /Li (−3.04 V vs SHE), indicating that KIBs could achieve a higher working voltage than SIBs and LIBs. However, K has a larger atomic radius (1.38 Å) than Li (0.68 Å) and Na (0.97 Å) atoms but has the smallest solvated ion radius of these three monovalent alkali metals (3.6 Å for K + , 4.8 Å for Li + , and 4.6 Å for Na + ) in propylene carbonate (PC) solvent because of the weaker Lewis acidity of K + . This is a useful feature of K + ‐based electrolytes, resulting in high ionic conductivity and fast diffusion kinetics.…”

“…The first step toward achieving high‐performance K + ‐based energy storage technologies is to exploit host materials that have superior potassium storage capability and sufficient structural stability to withstand the repeated K + ‐ion insertion and extraction processes . For PIBs, the most representative K + ‐based rechargeable energy storage system, the aforementioned target indicates that developing efficient anode materials with the favorable features of high specific capacities, excellent cycling stabilities, and fast diffusion/reaction kinetics is urgently required to advance the progress of current PIBs toward practical applications .…”

“…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.…”

Facile Synthesis of Hierarchical Hollow CoP@C Composites with Superior Performance for Sodium and Potassium Storage

“…[3] They still suffer, however, from large volume variation and low intrinsic electrical conductivity,w hich lead to rapid capacity decay and poor rate performance during cycling. [4] Preparing nanostructures is an efficient way to shorten the diffusion length and electron transport distance for electrode materials,b ut the increased interface charge transfer resistance,and self-aggregation and pulverization of nanoparticles during cycling are issues that need to be addressed. [5] Devising hollow morphologies and compounding with ac onductive matrix are being further utilized, offering synergistic effects to decrease the selfaggregation of nanoparticles,p ermit easy permeation of the electrolyte,a nd buffer the volume strain during cycling.…”