Discovery of Calcium‐Metal Alloy Anodes for Reversible Ca‐Ion Batteries

Abstract

techniques with high energy density and low cost. [1] Multivalent batteries, like Mg-ion, [2] Ca-ion, [3,4] and Al-ion batteries, [5,6] have the potential to realize significantly improved capacities, compared to monovalent batteries (e.g., Li-ion batteries), due to more electrons carried per ion. Among them, Ca-ion batteries (CIB) have drawn special attention with merits besides the capacity enhancement:(1) Ca/Ca 2+ has a reduction potential (−2.87 V) only slightly higher than Li/Li + (−3.04 V), yet much lower than Mg/Mg 2+ (−2.36 V) and Al/Al 3+ (−1.68 V), which provides CIB the prospect to function at voltages comparable with Li-ion batteries and much higher than the counterparts of Mg-ion and Al-ion batteries. [7,8] (2) Ca is the fifth most abundant element in the earth's crust with an extensive global resource distribution, in contrast to lithium. (3) The kinetics of Ca-ion in solid electrodes are faster than Mg-and Al-ions due to reduced charge density. [9][10][11] The development of CIBs was originally pioneered by the study of Ca-ion electrochemical intercalations into layered transition metal oxides and sulfides. [12] Subsequently, many efforts then were made to search for cathode materials which will tolerate a large amount of Ca-ions reversibly extracted/ re-accommodated upon charge/discharge. Material systems including Prussian blue compounds, [10,13,14] Chevrel phases, [15,16] spinels, [17][18][19] perovskites, [20] layered transition metal (TM) sulfides, [21] and iron phosphate, [22] were suggested to be effective Ca-ion electrodes with the spinels and perovskites attracting extra attention because of their predicted high voltage (>3.5 V) and large theoretical capacities (>240 mAh g −1 ) during discharge at room temperature. [17][18][19][20] Distinct from these TM-based electrodes, a graphite cathode has been reported which functions via the (de-)intercalation of electrolyte salt anions (A − = PF 6 − , ClO 4 − , and so on) upon charge/discharge at remarkably high voltages (4.5-5.6 V) [23,24] with a theoretical capacity as high as 372 mAh g −1 (corresponding to AC 6 ). [24,25] Yet, the practical capacity of batteries based on this material suffers from a large degradation (≈90 mAh g −1 ) as a result of the electrolyte decomposition under high voltage. [24] Unlike the continuous development of CIB cathode materials, studies focusing on anodes have been relatively scarce. Graphite-based CIB anodes have been shown to be problematic at room temperature due to difficulties related to the intercalation of calcium. [26] The pursuit of a calcium metal Ca-ion batteries (CIBs) show promise to achieve the high energy density required by emerging applications like electric vehicles because of their potentially improved capacities and high operating voltages. The development of CIBs is hindered by the failure of traditional graphite and calcium metal anodes due to the intercalation difficulty and the lack of efficient electrolytes. Recently, a high voltage (4.45 V) CIB cell using Sn as the anode has been reported...

Computational screening of anode materials for potassium‐ion batteries

“…Recently, material explorations using computational screening have assisted in the identification of promising candidates using high-throughput material databases based on first principles calculations. [24][25][26][27] Promising materials were identified for coatings at the interface of solid electrolytes, 28,29 cathode materials, [30][31][32][33][34] anode materials, 35,36 solid-state electrolyte, 37 Mg battery electrolytes, 38 photo-catalysts, 39 and fuel cell electrodes. 40 Our earlier works also presented novel and promising anode materials for SIBs using high-throughput screening.…”

Recent Advances and Perspectives on Calcium‐Ion Storage: Key Materials and Devices

“…Currently, anode materials for CIBs can be classified into four categories based on Ca 2+ storage mechanism, that is, plating anodes, [ 22,23 ] alloying anodes, [ 25,32 ] intercalation anodes, [ 29,33 ] and organic anodes. [ 24,34 ] Typical representatives of each category are exemplified in Figure , and Table 1 summarizes the experimental performances of anodes for CIBs.…”

Enhanced Potassium Ion Battery by Inducing Interlayer Anionic Ligands in MoS1.5Se0.5 Nanosheets with Exploration of the Mechanism

“…[ 3 ] Meanwhile, K + has high ion mobility and ionic conductivity in propylene carbonate (PC) electrolyte. Nevertheless, facing the issues arising from it having the largest atomic radius (1.38 Å) compared to lithium (0.68 Å), sodium (0.97 Å), and calcium (1.18 Å), [ 5–7 ] it is quite challenging to design suitable materials with the capability of highly reversible and long‐term K + insertion and extraction processes. [ 8,9 ] Based on global academic research, various materials have been explored and designed for KIBs, such as transition metal oxides, carbon‐based materials, and polyanion based materials, all of which showed signs of potential higher performance.…”