Enhanced stability of LiCoO₂ cathodes in lithium-ion batteries using surface modification by atomic layer deposition

Ultrathin atomic layer deposition (ALD) coatings enhance the performance of lithium-ion batteries (LIBs). Previous studies have demonstrated that LiCoO₂ cathode powders coated with metal oxides with thicknesses of ∼100 to 1000 Å grown using wet chemical techniques improved LIB performance. In this study, LiCoO₂ powders were coated with conformal Al₂O₃ ALD films with thicknesses of only ∼3 to 4 Å established using two ALD cycles. The coated LiCoO₂ powders exhibited a capacity retention of 89% after 120 charge-discharge cycles in the 3.3-4.5 V (vs Li/Li⁺) range. In contrast, the bare LiCoO₂ powders displayed only a 45% capacity retention. Al₂O₃ ALD films coated directly on the composite electrode also produced improved capacity retention. This dramatic improvement may result from the ultrathin Al₂O₃ ALD film acting to minimize Co dissolution or reduce surface electrolyte reactions. Similar experiments with ultrathin ZnO ALD films did not display enhanced performance.