In-situ thermal annealing Pt/Ti interphase layers for epitaxial growth of improved Li(Ni0.5Mn0.3Co0.2)O2 solid thin-film cathodes

Thin film batteries (TFBs) are receiving increasing interest in the transition stage from current liquid electrochemistry to solid-state future in pursuit of higher energy and power densities. Nevertheless, the fundamental understanding the impacts of the electrode-solid-electrolyte interface engineering and unveiling the correlation between crystallographic texture as well as the electrochemical behavior of electrodes has remained elusive. Herein, the epitaxial growth of LiNi0.5Mn0.3Co0.2O2 cathode on two rational designed buffer substrates has been studied. The highly textured LiNi0.5Mn0.3Co0.2O2 thin films with c-axis (003) preferred orientation were successfully fabricated onto the in situ-annealed Pt (111) reconstructed buffer substrate by virtue of direct-current (DC) and radio frequency (RF) magnetron sputtering technologies. The LiNi0.5Mn0.3Co0.2O2 thin films were also deposited onto the Ti buffer substrate. The effects of the substrate on the structural and electrochemical properties of the LiNi0.5Mn0.3Co0.2O2 thin film deposited on these two (Pt and Ti) substrates have been both investigated and compared. The deposited LiNi0.5Mn0.3Co0.2O2 thin film on the Pt substrate exhibited much better electrochemical performance as the sole active cathodes thin film electrodes than the Ti buffered one. The results demonstrate that the Pt/LiNi0.5Mn0.3Co0.2O2 thin film electrode exhibits a discharge capacity of 84 mA h/g at ambient temperature and shows a stable cyclic performance within 200 cycles. Such interface dominated electrochemical performance behavior is of technological significance. Furthermore, it is indispensable in developing synergistic interfacial engineered design and process control strategy on fabricating more robust batteries with higher energy density and longer cycling stability beyond thin solid ones.