Enhanced electrochemical stability of high-voltage LiNi0.5Mn1.5O4 cathode by surface modification using atomic layer deposition

We report improved cycling performance of high-voltage LiNi0.5Mn1.5O4 cathode for lithium-ion batteries by modifying its surface with ultrathin layer coating of Al2O3 (<1 nm) using atomic layer deposition (ALD) technique. Four and six layers of ALD Al2O3 were coated directly on the porous LiNi0.5Mn1.5O4 nanoparticle (~200 nm) slurry composite. Electrochemical characterization results show that LiNi0.5Mn1.5O4 electrode with four and six layers of ALD Al2O3 maintained 92 and 98 % of their initial capacity after 200 cycles, respectively, in comparison to bare LiNi0.5Mn1.5O4 electrode which showed 84 % capacity retention. We show that the ALD Al2O3 coated cathode surface is protected from undesired side reactions occurring at the electrode/electrolyte interface. For the first time, we used XPS studies to investigate the surface chemistry of ultrathin ALD Al2O3 coated LiNi0.5Mn1.5O4 and confirmed that the ultrathin ALD Al2O3 layer reduces side reactions involving organic components of the electrolyte decomposition product in high-voltage cathodes.