Processing-and cell-stage thermodynamic screening of nacre-and bone-inspired carbonate and phosphate phases on aluminium current collectors in fluorine-free lithium-ion cells with an open screening framework

Water-processed, fluorine-free lithium-ion cathodes avoid fluorinated binders and organic solvents, but their alkaline slurry attacks the aluminium current collector, and the cell lacks the protective AlF3 layer that fluorinated salts form. Water-processed (bio-)binders do not protect the collector; the current fixes are pH control with H3PO4 and carbon-coated foil. We ask which nacre- and bone-lineage mineral phases can survive both the alkaline aqueous slurry and the oxidising potential of a fluorine-free cell, and which measurements would decide the rest. We compare nacre-lineage calcium carbonate, bone-lineage calcium phosphates, condensed calcium phosphates and aluminium phosphates as biopolymer-templated coatings, in the slurry (processing stage) and at cell potential (cell stage). Our open, extensible screening framework uses sourced thermochemistry with propagated uncertainty, and reports which phases are excluded, which remain open, and how precise a measurement must be to decide each. Calcite is thermodynamically stable against dissolution at pH 10.0–13.0 for total calcium from 1×10−4 mol dm−3. In a LiClO4-saturated electrolyte, carbonate is thermodynamically excluded above about 4.02 V, and hydroxyapatite and the tricalcium phosphates (upper bounds on oxidation onset 3.98 V–4.07 V) at 4.3 V and above. Condensed calcium phosphates are not excluded at any cutoff-voltage class, and aluminium phosphates are undetermined. Carbonate and bone mineral therefore cannot serve as the cell-stage barrier, and the condensed calcium phosphates remain the open bone-inspired candidates. One slurry-immersion and potential-hold experiment, with two measurements (the Ca2+ transfer free energy into the cell solvent and the template–nucleus interfacial energy), would decide them. No phase can pass the oxidation test while these transfer free energies are unmeasured, and the nucleation model failed its check against literature cases with known outcomes.