Polyanionic Compounds for Potassium‐Ion Batteries

Abstract

Lithium‐ion batteries have the highest energy density among practical secondary batteries and are widely used for electronic devices, electric vehicles, and even stationary energy‐storage systems. Along with the expansion of demand and applications, the concern about resources of lithium and cobalt is growing. Therefore, secondary batteries composed of abundant elements are required to complement lithium‐ion batteries. In recent years, the development of potassium‐ion batteries has attracted much attention, especially for large‐scale energy storage. In order to realize potassium‐ion batteries, various compounds are proposed and investigated as positive electrode materials, including layered transition‐metal oxides, Prussian blue analogues, and polyanionic compounds. This article offers a review of polyanionic compounds which are typically composed of abundant elements and expected high operating potential. Furthermore, we deliver our new results to partially compensate for lack of studies and provide a future perspective.

Sulfonylamide‐Based Ionic Liquids for High‐Voltage Potassium‐Ion Batteries with Honeycomb Layered Cathode Oxides

“…It is evident that few high‐voltage cathodes exist (exhibiting average working voltages of close to or beyond 4 V); Prussian organic moieties and polyanionic compounds such as KVOPO 4 , KVP 2 O 7 , KVPO 4 F, amongst others dominating as high‐voltage cathode candidates. Potassium‐based oxides tend to show low average voltage; however, this prevailing notion was recently obliterated by the design of tellurium‐doped K 2/3 Ni 2/3 Te 1/3 O 2 (or equivalently as K 2 Ni 2 TeO 6 , for simplicity) and K 2/3 Ni 1/3 Co 1/3 Te 1/3 O 2 (K 2 NiCoTeO 6 ) as high‐voltage layered cathode materials (Figure a) . Despite the alluring prospects of using these high‐voltage cathode materials to develop a high‐voltage battery system, instability of organic electrolytes at high‐voltage operation coupled with the high reactivity of potassium metal anode continues to cast doubt on the safety of electrolytes based on organic solvents …”

“…Ni 2/3 Te 1/3 O 2 (or equivalently as K 2 Ni 2 TeO 6 , for simplicity) and K 2/ 3 Ni 1/3 Co 1/3 Te 1/3 O 2 (K 2 NiCoTeO 6 ) as high-voltage layered cathode materials(Figure 1a) [6,7,[9][10][11][12][13]. Despite the alluring prospects of using these high-voltage cathode materials to develop a highvoltage battery system, instability of organic electrolytes at high-voltage operation coupled with the high reactivity of…”

Advancements and Challenges in Potassium Ion Batteries: A Comprehensive Review

“…The designing of high‐voltage KIBs are considered to be a challenge due to the limited availability of high‐voltage cathodes and high‐voltage stable electrolytes. In recent years, some cathode materials (K 2/3 Ni 2/3 Te 1/3 O 2 , K 2/3 Ni 1/3 Co 1/3 Te 1/3 O 2 ) have been explored in this aspect . Hence the main challenge is to develop electrolyte which can withstand at high voltages.…”

“…In recent years, some cathode materials (K 2/3 Ni 2/3 Te 1/3 O 2 , K 2/3 Ni 1/3 Co 1/3 Te 1/3 O 2 ) have been explored in this aspect. [74,79,[195][196][197][198][199] Hence the main challenge is to develop electrolyte which can withstand at high voltages. In this regard, ionic liquids are considered to a promising category of electrolyte because of their stable nature at higher voltages.…”

A Potential Cathode Material for Rechargeable Potassium‐Ion Batteries Inducing Manganese Cation and Oxygen Anion Redox Chemistry: Potassium‐Deficient K0.4Fe0.5Mn0.5O2

“…In this context, rechargeable batteries that utilize earth‐abundant materials such as potassium‐ion (K‐ion) are gaining tremendous attention as not only promising low‐cost alternatives to Li‐ion technology but also as high‐performance energy storage systems . An economical and well‐studied material such as graphite can be used directly as anode, whereas high voltages can be handled by coupling graphite with suitable cathode candidates and stable potassium‐based electrolytes . Despite the alluring virtues of adopting the K‐ion technology, only a few electrode materials that can facilitate reversible insertion of the large K‐ion exist.…”