Electrolyte Salt Chemistry Enables 3D Nitrogen and Phosphorus Dual‐Doped Graphene Aerogels for High‐Performance Potassium‐Ion Batteries

Abstract

Potassium‐ion batteries (PIBs) have attracted tremendous attentions for scalable electrical energy storage owing to the abundant K resources. Heteroatom co‐doped hard carbon is considered to be a reliable material to boost ion transport and provide active sites for reversible potassium storage. Herein, N/P dual‐doped 3D graphene aerogels (NPGAs) with hierarchical pores, enlarged interlayer distance, and high doping level are successfully synthesized, which exhibit outstanding electrochemical performance for PIBs. A detailed comparative study found that promoted coulombic efficiency, improved specific capacity (507 mAh g−1 at 100 mA g−1 after 100 cycles) and excellent cycle performance (106 mAh g−1 at 5000 mA g−1 after 3000 cycles) can be reached by replacing KPF6 with potassium bis(fluorosulfonyl)imide (KFSI). Further kinetic analysis reveals that NPGAs present more capacitive behavior of K‐ion, low resistance, and fast K‐ion conductivity by virtue of the advanced solid electrolyte interphase (SEI) film formed in KFSI‐EC/DEC electrolyte. Ex situ XPS, SEM, and TEM all confirm a physical flexible, chemical stable, and inorganic SEI layer formed on the surface of the electrode. In general, this work promotes a deep understanding of the mechanism of potassium storage and provides more opportunities for practical PIBs.

Sulfur and nitrogen codoped cyanoethyl cellulose‐derived carbon with superior gravimetric and volumetric capacity for potassium ion storage

“…The peak at S 2p together with KSO x (166.9 eV) and thiosulfate/–SO 2 – (168.8 and 170.1 eV) is the main components of the SEI layer 100 . In addition, K–F (683.0 and 684.2 eV), C–F, O–F, and S–F (687.4 eV) are present in the F 1s 101 . In N 1s, N‐5, N‐6, and N‐Q can be converted into N‐5/K, N‐6/K, and N‐Q/K, respectively, indicating that the structure of the functional group had undergone irreversible changes 24 .…”

“…100 In addition, K-F (683.0 and 684.2 eV), C-F, O-F, and S-F (687.4 eV) are present in the F 1s. 101 In N 1s, N-5, N-6, and N-Q can be converted into N-5/K, N-6/K, and N-Q/K, respectively, indicating that the structure of the functional group had undergone irreversible changes. 24 In summary, XPS analysis demonstrates that the SEI film formed in SNCC is mainly composed of inorganic salts based on K-S, K-F, and K-C.…”

Organic electrolyte design for practical potassium-ion batteries

“…Since then, KFSI has been widely used as the salt for anode materials such as phosphorus, 26 phosphides, 27,28 chalcogenides, [29][30][31][32][33][34] and carbon materials. [35][36][37] Besides the ability to form a stable SEI, the reduced free solvent molecules in the KFSI electrolyte due to the strong solvation are also helpful to alleviate the parasitic reactions, and thus enable a higher performance. Moreover, KFSI has higher solubility and higher conductivity than KPF 6 , due to the low ionic association of the K + and FSI À ions.…”

Interfacial Engineered Vanadium Oxide Nanoheterostructures Synchronizing High-Energy and Long-Term Potassium-Ion Storage

“…As a potential alternative, potassium reserves in the Earth’s crust are nearly 1000 times greater than lithium sources. Meanwhile, it also features a low reduction potential of −2.93 V vs SHE, similar to the value of lithium (−3.04 V), promising for designing KICs with electrochemical performance comparable to LICs. , However, most of the reported KICs suffer from moderate energy density and electrochemical stability, − due to the large ionic radius of K + (1.38 Å). In KICs, only partial active sites of usual electrode materials can be occupied by K + , and the insertion/extraction of large K + also leads to significant and irreversible electrode pulverization during charge–discharge processes.…”