Contents lists available at ScienceDirect Nano Energy journal homepage: www.elsevier.com/locate/nanoen Review Recent advance in new-generation integrated devices for energy harvesting and storage Sining Yun a,* , Yongwei Zhang a , Qi Xu b , Jinmei Liu b , Yong Qin b a Functional Materials Laboratory (FML), School of Materials Science and Engineering, Xi'an University of Architecture and Technology, Xi'an, Shaanxi, 710055, China b School of Advanced Materials and Nanotechnology, Xidian University, Xi'an, Shaanxi, 710126, China ARTICLE INFO Keywords: Integrated devices Lithium-ion batteries Supercapacitors Nanogenerators Biofuel cells Solar cells ABSTRACT Energy harvesting and storage devices, including lithium-ion batteries (LIBs), supercapacitors (SCs), nanogen- erators (NGs), biofuel cells (BFCs), photodetectors (PDs), and solar cells, play a vital role in human daily life due to the possibility of replacing conventional energy from fossil fuels. However, these isolated devices only have limited performance and/or sole applicability, and cannot provide enough energy for application with long-term run and the ever-changing working positions. This suggests that it is urgent to develop the fine self-powered systems to meet the growing demand of energy for long-term use in different environment scenes. Developing integrated power pack, combining energy harvesting and storage, is an effective path to obtain a small size, light weight, high density and high reliability energy system. In this review, eight types of multifunctional integrated devices, such as LIB&SC, LIB&NG, BFC&NG, PD&BFC, SC&PD, SC&solar cells, NG&SC&solar cell, and LIB&solar cells, for energy harvesting and storage are reviewed in a broad sense, and a comprehensive summary of the recent development trends and highlights in the integrated device fields is given. Finally, the challenges and future outlooks for their successful commercialization are featured based on the recent advances and important findings. 1. Introduction Due to the limited capacity, greenhouse gases emission of the tra- ditional fossil fuel, and the increasing energy requirement, developing new and highly efficient technologies for harvesting energy from the environment has become a matter of great urgency. Harvesting the unused and wasted environmental green energy, such as solar energy, wind energy, microbe energy, and kinetic energy, and converting them into a more useable form is a promising way for the long-term energy needs and environmental sustainability. Up to date, a large number of energy conversion technologies, such as solar cells [1–4], piezoelectric nanogenerators (PENGs) [5–9], triboelectric nanogenerators (TENGs) [10–12], and biofuel cells (BFCs) [13–15], have been developed to convert the diverse environmental energy into electricity. However, these environmental energies are highly dependent on when and where they are available, so the harvested energy could not provide con- tinuous power supply which is always not in good alignment with the actual demand. One promising solution is to integrate different kinds of energy harvesters into one unit, which can harvest diverse ambient energies simultaneously, and thus enhance the environmental adaptability of energy harvesters. Taking the implantable device as an example, by integrating a PENG and a BFC based on a simple RC high pass filter [16], the hybrid energy scavenging device can convert both the glucose from the biofluid and the kinetic energy from breathing into electricity. The two energy harvesting approaches can work simultaneously or individually, thereby boosting output energy and service lifetime of the original devices. In addition, integrating different devices together, through the synergistic effect between the devices having different operation mechanisms, one could obtain much larger power output as compared with its two individual power output components [17], which facilitates more effective multi-type energies harvesting. The other solution is to develop an energy conversion and storage system, through which the electrical energy, harvested from the en- vironment, can be stored high-efficiently into energy storage devices for future energy requirements. A large number of energy storage devices, such as lithium-ion batteries (LIBs) [18–20], lithium-sulfur batteries [21–23], and supercapacitors (SCs) [24–26], can be the appropriate candidates. For example, under sunlight illumination, a photo-charging process in the semiconductor will convert the solar energy into elec- tricity and store it by an electrochemical way in the lithium battery; the stored electrochemical energy can then be delivered to the electronics. https://doi.org/10.1016/j.nanoen.2019.03.074 Received 23 January 2019; Received in revised form 1 March 2019; Accepted 21 March 2019 * Corresponding author. E-mail addresses: alexsyun1974@aliyun.com, yunsining@xauat.edu.cn (S. Yun). Nano Energy 60 (2019) 600–619 Available online 29 March 2019 2211-2855/ © 2019 Elsevier Ltd. All rights reserved. T