Thermodynamic aspects of cathode coatings for lithium-ion batteries

Metal oxide cathode coatings are capable of scavenging the hydrofluoric acid (HF) (present in LiPF₆-based electrolytes) and improving the electrochemical performance of Li-ion batteries. Here, a first-principles thermodynamic framework is introduced for designing cathode coatings that consists of four elements: i) HF-scavenging enthalpies, ii) volumetric and iii) gravimetric HF-scavenging capacities of the oxides, and iv) cyclable Li loss into coating components. 81 HF-scavenging reactions involving binary s-, p- and d-block metal oxides and fluorides are enumerated and these materials are screened to find promising coatings based on attributes (i-iv). The screen successfully produces known effective coating materials (e.g., Al₂O₃ and MgO), providing a validation of our framework. Using this design strategy, promising coating materials, such as trivalent oxides of d-block transition metals Sc, Ti, V, Cr, Mn and Y, are predicted. Finally, a new protection mechanism that successful coating materials could provide by scavenging the wide bandgap and low Li ion conductivity LiF precipitates from the cathode surfaces is suggested.