Potassium intercalation into graphite to realize high-voltage/high-power potassium-ion batteries and potassium-ion capacitors

Abstract

Highly reversible potassium intercalation into graphite in carbonate ester solution at room temperature is achieved byelectrochemical reductionat the potential approaching to K + /Kstandard potential which islower than that of Li + /Li. The intercalation results in formation of stage-1 KC 8 compound with delivering 244 mAh g-1 of reversible capacity. The initial irreversible capacity is suppressed by polycarboxylate bindercompared to poly(vinyledene fluoride) binder.The lower potential, good cyclabilty, andexcellent rate capabilityare first demonstrated forenergy storage applications. Because of the lowest potential andweakest solvation among Li + , Na + , K + , Mg 2+ , and Ca 2+ ion carriers, potassium shuttlecock mechanism between two insertion materials as "potassium-ion battery" is advantageous for higher-voltage/-power rechargeable batteries.The excellent rate performance is beneficial for the application to hybrid-type capacitor, "potassium-ion capacitor,"as an alternative to lithium-ion capacitors.

Non-Aqueous K-Ion Battery Based on Layered K0.3MnO2and Hard Carbon/Carbon Black

“…In addition, higher transport numbers and mobility of K + ions could be possible in non-aqueous electrolytes due to the lower charge density of K + vs. both, Li + and Na + . 5 However, the larger Shannon's ionic radius and higher atomic weight of potassium (1.40 Å and 39.098 g mol −1 for K + ) vs. lithium (0.76 Å and 6.941 g mol −1 ) and sodium (1.00 Å and 22.990 g mol −1 ) result in decreased gravimetric and volumetric energy. 5,6 The high reactivity of K metal also raises serious safety concerns and is probably one of the major reasons why KIBs have not yet been investigated in greater detail.…”

“…5 However, the larger Shannon's ionic radius and higher atomic weight of potassium (1.40 Å and 39.098 g mol −1 for K + ) vs. lithium (0.76 Å and 6.941 g mol −1 ) and sodium (1.00 Å and 22.990 g mol −1 ) result in decreased gravimetric and volumetric energy. 5,6 The high reactivity of K metal also raises serious safety concerns and is probably one of the major reasons why KIBs have not yet been investigated in greater detail. Nevertheless, the interesting properties of KIBs, which are between those of LIBs and NIBs, certainly deserve a more detailed investigation.…”

“…24 Komaba et al demonstrated that in EC:DEC organic electrolytes KFSI [potassium bis(fluorosulfonyl)imide] is the most appropriate conductive salt in comparison with KClO 4 and KPF 6 due to its higher solubility. 5 Only few reports on positive and negative electrode materials for KIBs exist and, to the best of our knowledge, a conventional nonaqueous KIB (full cell) has not been demonstrated yet. Thus far, only one report dealing with an unconventional K-ion oxygen cell, employing an oxygen cathode, is available, albeit with limited cycling.…”

“…Recently, soft carbon, hard carbon (HC) and graphite were evaluated as anode materials in KIBs. 5,23,24 Compared to soft carbon, graphite exhibits a more pronounced capacity fade and lower rate capability, but both deliver high capacities of about 260 mAh g −1 . 23 The use of HC is interesting as the capacity is mostly delivered above 0.1 V, which reduces the risk of K-metal plating.…”

Insertion of Mono- vs. Bi- vs. Trivalent Atoms in Prospective Active Electrode Materials for Electrochemical Batteries: An ab Initio Perspective

“…Indeed, these elements have some of the highest concentrations in the Earth's continental crust (Na: 2.36%, K: 2.14%) [3] so that scarcity is not expected to be an issue. Also, these elements' standard electrode potentials are comparable (Li + /Li: −3.040 V, Na + /Na: −2.714 V, K + /K: −2.936 V against the standard hydrogen electrode) [4], so that expected battery voltages could in principle reach similar values, and their Stokes radii generally decrease with increasing mass, which leads to faster diffusion in liquid electrolytes [5]. On the other hand, the increasing mass-to-carried-charge ratio leads to a decrease of the energy density from Li to K and the increasing ionic radii complicate the accommodation of the metal ions in an electrode host structure.…”