All‐Solid‐State Thin Film Lithium/Lithium‐Ion Microbatteries for Powering the Internet of Things

Abstract

As the world steps into the era of Internet of Things (IoT), numerous miniaturized electronic devices requiring autonomous micropower sources will be connected to the internet. All‐solid‐state thin‐film lithium/lithium‐ion microbatteries (TFBs) combining solid‐state battery architecture and thin‐film manufacturing are regarded as ideal on‐chip power sources for IoT‐enabled microelectronic devices. However, unlike commercialized lithium‐ion batteries, TFBs are still in the immature state, and new advances in materials, manufacturing, and structure are required to improve their performance. In this review, the current status and existing challenges of TFBs for practical application in internet‐connected devices for the IoT are discussed. Recent progress in thin‐film deposition, electrode and electrolyte materials, interface modification, and 3D architecture design is comprehensively summarized and discussed, with emphasis on state‐of‐the‐art strategies to improve the areal capacity and cycling stability of TFBs. Moreover, to be suitable power sources for IoT devices, the design of next‐generation TFBs should consider multiple functionalities, including wide working temperature range, good flexibility, high transparency, and integration with energy‐harvesting systems. Perspectives on designing practically accessible TFBs are provided, which may guide the future development of reliable power sources for IoT devices.

Direct Recycling of All-Solid-State Thin Film Lithium Batteries with Lithium Anode Failure

“…In the upcoming era of the Internet of Things, miniaturized electronic devices (such as micro sensors, micro robots, medical implants, etc.) will be wirelessly linked together to collect and exchange data, which necessitates the development of compatible micro power sources [1][2][3] . Among current battery technologies, all-solid-state thin film lithium batteries (TFBs) are regarded as the most promising candidate to power these miniaturized electronic devices due to their solid-state architecture, flexible size and shape, long cycle life, low self-discharge rate, and facile miniaturization 2,4,5 .…”

“…will be wirelessly linked together to collect and exchange data, which necessitates the development of compatible micro power sources [1][2][3] . Among current battery technologies, all-solid-state thin film lithium batteries (TFBs) are regarded as the most promising candidate to power these miniaturized electronic devices due to their solid-state architecture, flexible size and shape, long cycle life, low self-discharge rate, and facile miniaturization 2,4,5 . Since Bates et al 6 reported the LiCoO2 (LCO)/lithium phosphorus oxynitride (LiPON)/Li TFBs with outstanding electrochemical performance three decades ago, intensive efforts have been made to develop highperformance TFBs [7][8][9] .…”

“…Currently, Li metal or Li alloy is the most widely used anode in TFBs due to its high theoretical capacity (3680 mAh•g −1 ), low redox potential (−3.04 V vs. the standard hydrogen electrode), and excellent electrochemical performance 2,7,10 . However, its strong reactivity with moisture, large volume change during cycling, and inevitable dendrite growth during Li plating may lead to its failure and the end of life of the TFBs, as schematically illustrated in Fig.…”

“…(1) The formation of Li voids at the LiPON/Li interface due to irreversible Li stripping and plating or dewetting of Li with LiPON electrolyte during cycling may result in the Li failure. (2) The oxidation of Li by non-inert gases (e.g., carbon dioxide, moisture, oxygen, nitrogen, etc.) during the TFBs' preparation process, transfer process, encapsulation process, and operating process may result in the Li failure.…”

“…(1) The most commonly used amorphous electrolytes (e.g., LiPON) cannot withstand a high-temperature or hydrothermal treatment. (2) The cathode film and electrolyte film in TFBs cannot be processed and regenerated separately because it is difficult to separate them by mechanical separation or dissolution separation methods. Therefore, in this work, based on the most commonly used TFBs of LCO/LiPON/Li (F-TFB) with its Li anode being partially oxidized during cycling, a simple ethanol-assisted method was proposed to remove the spent Li anode in the F-TFB to directly recycle the underlying LCO/LiPON film.…”