Abstract:

Owing to their remarkable miniaturization and integration capabilities, all-solid-state thin-film lithium-ion batteries are quite appropriate as the on-chip power for microsystems, such as implantable medical devices, micro-electro-mechanical systems and integrated circuits. The performance of the all-solid-state thin-film lithium-ion batteries is greatly determined by the anode film. Metal Li is usually adopted as the anode material, however, the issues, including Li dendrite growth and poor thermal stability, hinder its applications in the high-temperature and high-safety fields, such as industrial and military. Therefore, various anode materials have been investigated in recent years. Unfortunately, few anode materials can achieve high specific capacity and good stability simultaneously. Due to its relatively high specific capacity and good electrochemical stability, LiNbO₃ has been widely used as a coating layer in the batteries and has been demonstrated to effectively suppress side reactions at the electrode|electrolyte interface. However, there is still lack of deep understanding of the electrochemical characteristics of LiNbO₃; also, no previous work has been performed to explore the applications of LiNbO₃ in the all-solid-state thin-film lithium-ion batteries. In this work, the electrochemical characteristics of LiNbO₃ as a new anode material are carefully investigated. It is found that the LiNbO₃ anode has relatively high specific capacity (410.2 mAh·g⁻¹), high rate capability (80.9 mAh·g⁻¹ at 30C), good cycling stability (100% capacity retention over 2000 cycles at 1C) and high ionic conductivity (4.5 × 10⁻⁸ S·cm^–1 at room temperature). Moreover, an all-solid-state thin-film lithium-ion battery with a Pt current collector|NCM523 cathode|LiPON electrolyte|LiNbO₃ anode|Pt current collector configuration is also prepared. This full battery presents good performance in terms of its relatively high area capacity (16.3 μAh·cm⁻² at a current density of 0.5 μA·cm⁻²), good rate characteristic (1.9 μAh·cm⁻² even at a high current density of 30 μA·cm⁻²) and good stability (86.4% capacity retention after 300 cycles). Particularly, the retained capacity remains as high as 95.6% even when this full battery operates continuously at 100 ℃ for ~200 h, demonstrating its good thermal stability. As confirmed by both the electrochemical and micro characterization, the LiPON|LiNbO₃ interface is quite stable under both the repeated charge/discharge cycling and high temperature operation, which contributes to the good performance of this full battery even under high temperatures. For comparison, the LiPON|Li interface degrades significantly under high temperatures, thus resulting in poor performance of the corresponding full battery. This work is helpful to develop a new anode film and all-solid-state thin-film lithium-ion battery which is suitable for the industrial and military applications.

Key words: All-solid-state lithium-ion battery, LiNbO₃ film, Anode, Interface, High temperature, Stability