A novel calcium fluorinated alkoxyaluminate salt as a next step towards Ca metal anode rechargeable batteries

Abstract

Ca metal anode rechargeable batteries are seen as a sustainable high-energy density and high-voltage alternative to the current Li-ion battery technology due to the low redox potential of Ca metal...

Design Principles and Routes for Calcium Alkoxyaluminate Electrolytes

“…To address these challenges, we report a new synthetic route utilizing a one-pot method with both a soluble calcium base as well as using an intermediate without separations. Previously, Ca(OR) 2 (where OR = hfip) has been synthesized through an exchange reaction between a slurry of Ca(OMe) 2 and hexafluoroisopropanol; 16 however, the less acidic and more sterically bulky tftb and hftb ligands are much less reactive. As shown in Scheme 1, the new route is enabled by a soluble source of calcium, calcium hexamethydisilazide (Ca-(HMDS) 2 ).…”

A metallic two-dimensional b-BS2 monolayer as a superior Na/K-ion battery anode

“…15–18 In recent years, with the rapid development of the high-end electronics market, non-lithium-ion batteries (NLBs), including sodium-ion batteries (SIBs), potassium-ion batteries (PIBs), and multivalent ion batteries, have been considered as the next generation of energy power sources. 19–23 Therefore, the development of cost-effective, long-life, especially anode electrode materials of large-capacity energy storage systems is still highly desired. 24–26…”

Calcium Cosalt Addition to Alter the Cation Solvation Structure and Enhance the Ca Metal Anode Performance

“…Coulombic efficiencies (CE) as high as 97% have been reported using this electrolyte. − More recently, electrolytes using calcium salts with weakly coordinating anions (WCAs) have been developed with the goal of widening the electrochemical stability window of the electrolyte. Two groups concurrently reported the synthesis and testing of calcium tetrakis­(hexafluoroisopropoxy) borate (Ca­(BHFIP) 2 )/dimethoxyethane (DME) electrolytes with CE as high as 92%. , As with Ca­(BF 4 ) 2 /EC/PC, deposits from this electrolyte displayed significant F content, indicating salt decomposition. , Similarly, calcium tetrakis­(hexafluoroisopropoxy) aluminate (Ca­(AlHFIP) 2 ) /DME and calcium tetrakis­(perfluoro- tert -butoxy) aluminate (Ca­(TPFA) 2 ) /DME electrolytes exhibit instability at Ca deposition potentials. , Furthermore, despite magnesium bis­(trifluoromethylsulfonyl)­imide (MgTFSI 2 ) being used to successfully cycle Mg metal, , CaTFSI 2 has been shown to be incapable of reversibly plating and stripping Ca metal in ethereal electrolytes, likely due to the decomposition of the TFSI – anion . As an alternate class of WCA electrolytes lacking F, calcium carba- closo -dodecaborate (Ca­(CB 11 H 12 ) 2 ) /DME/THF displayed reversible calcium plating and stripping with CE as high as 88% .…”

“…To meet society’s growing needs for renewable energy storage, novel battery chemistries with higher energy density and lower cost than Li-ion batteries need to be developed. , Ca metal batteries have been proposed as alternatives to Li-ion batteries due to the greater crustal abundance (41,500 mg/kg for Ca vs 20 mg/kg for Li) and anode capacity (1337 mAh/g for Ca metal anodes vs 372 mAh/g for Li/C 6 anodes). Despite these advantages, development of Ca metal batteries has been limited. ,− …”

“…2 0 , 2 1 Similarly, calcium tetrakis-(hexafluoroisopropoxy) aluminate (Ca(AlHFIP) 2 ) /DME and calcium tetrakis(perfluoro-tert-butoxy) aluminate (Ca-(TPFA) 2 ) /DME electrolytes exhibit instability at Ca deposition potentials. 8,22 Furthermore, despite magnesium bis(trifluoromethylsulfonyl)imide (MgTFSI 2 ) being used to successfully cycle Mg metal, 23,24 CaTFSI 2 has been shown to be incapable of reversibly plating and stripping Ca metal in ethereal electrolytes, likely due to the decomposition of the TFSI − anion. 25 As an alternate class of WCA electrolytes lacking F, calcium carba-closo-dodecaborate (Ca(CB 11 H 12 ) 2 ) /DME/THF displayed reversible calcium plating and stripping with CE as high as 88%.…”