Sputtering TiO2 on LiCoO2 composite electrodes as a simple and effective coating to enhance high-voltage cathode performance

Abstract

Abstract Surface coating is a key strategy in lithium-ion battery technologies to achieve a high and stable battery performance. Increasing the operation voltage is a direct way to increase the energy density of the battery. In this work, TiO 2 is directly sputtered on as-fabricated LiCoO 2 composite electrodes, enabling a controllable oxide coating on the topmost of the electrode. With an optimum coating, the discharge capacity is able to reach 160 mAh g −1 (86.5% retention) after 100 cycles within 3.0–4.5 V at 1 C, which is increased by 40% compared to that of the bare electrode. The high-voltage rate capability of LiCoO 2 is also remarkably enhanced after TiO 2 -coating as reflected by the much larger capacity at 10 C (109 vs. 74 mAh g −1 ). The artificially introduced oxide coating is believed to make the LiCoO 2 electrode more resistant to interfacial side reactions at high voltage and thus minimizes the irreversible loss of the active material upon long cycling. The TiO 2 coating layer is also possible to partially react with the decomposition product of electrolyte (e.g. HF) and form a more stable and conductive interphase containing TiF x , which is responsible for the improvement of the rate capability.