Key Takeaways & Executive Findings
- •• A universal bulk heterojunction strategy is developed to create oxygen vacancies by embedding laser-manufactured metal nanocrystals into the TiO2 matrix, significantly boosting carrier mobility. • The proposed mechanism combines plasmonic-induced hot electron injection and enhanced conductivity from Schottky contact-derived oxygen vacancies, leading to improved photocharge separation and transport. • The TiO2-based photocathode achieves benchmark performance in photoassisted lithium-ion batteries, including a capacity of 276 mAh g−1 at 0.2 A g−1 under illumination and a photoconversion efficiency of 1.276% at 3 A g−1. • The bulk heterojunction strategy demonstrates excellent stability with minimal capacity and Coulombic efficiency loss over 200 cycles, highlighting its potential for efficient and stable photoassisted energy storage systems.
Abstract
Efficient and stable photocathodes with versatility are of significance in photoassisted lithium-ion batteries (PLIBs), while there is always a request on fast carrier transport in electrochemical active photocathodes. Present work proposes a general approach of creating bulk heterojunction to boost the carrier mobility of photocathodes by simply laser assisted embedding of plasmonic nanocrystals. When employed in PLIBs, it was found effective for synchronously enhanced photocharge separation and transport in light charging process. Additionally, experimental photon spectroscopy, finite difference time domain method simulation and theoretical analyses demonstrate that the improved carrier dynamics are driven by the plasmonic-induced hot electron injection from metal to TiO2, as well as the enhanced conductivity in TiO2 matrix due to the formation of oxygen vacancies after Schottky contact. Benefiting from these merits, several benchmark values in performance of TiO2-based photocathode applied in PLIBs are set, including the capacity of 276 mAh g−1 at 0.2 A g−1 under illumination, photoconversion efficiency of 1.276% at 3 A g−1, less capacity and Columbic efficiency loss even through 200 cycles. These results exemplify the potential of the bulk heterojunction strategy in developing highly efficient and stable photoassisted energy storage systems.
1. Introduction
Developing solar energy supplies are essential in addressing the challenges posed by the energy crisis and combating energy poverty in future societies [1–3]. Traditionally, the common approach has been to integrate photovoltaic cells and lithium-ion batteries as off-grid energy storage devices, while these systems encounter difficulties such as ohmic losses, voltage mismatching, and packaging limitations, thereby hindering the further development of this field [4–7].
Photoassisted battery that can combine photoelectronic capabilities with energy storage in a single device, integrates the functions of capturing and utilizing light energy for both generating electrons and storing energy within the battery. Such unique design allows the battery to significantly enhance its discharge capacity when exposed to illumination. In addition, this integration also enables miniaturization, making the battery more compact and suitable for various applications [8–12]. Among the various types of photoassisted batteries, photoassisted Li-ion batteries (PLIBs) have attracted considerable attention due to their high energy density [13–17]. In PLIBs, the photoactive cathode serves as a dual function by absorbing sunlight to generate additional electrons (e−) and providing a suitable structure for the rapid (de)-insertion of Li+ ions, thereby contributing significantly to the high capacity and ideal potential of the battery while playing a crucial role in both photoelectric conversion and energy storage [18–20].
Semiconductor materials that have the potential to meet the aforementioned requirements often suffer from rapid recombination of photogenerated carriers due to their inappropriate band structures [21–23]. To address this issue, a common approach is to construct a hybrid electrode by combining a photosensitizer and a conductive agent.
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Zelin Ma, Shiyao Wang, Zhuangzhuang Ma, Juan Li, Luomeng Zhao, Zhihuan Li, Shiyuan Wang, Yazhou Shuang, Jiulong Wang, Fang Wang, Weiwei Xia, Jie Jian, Yibo He, Junjie Wang, Pengfei Guo, Hongqiang Wang (2024). Efficient and Stable Photoassisted Lithium-Ion Battery Enabled by Photocathode with Synergistically Boosted Carriers Dynamics. Nano-Micro Letters. https://doi.org/10.1007/s40820-024-01570-7
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Frequently Asked Questions
What is the main innovation of this paper?
The paper introduces a universal bulk heterojunction strategy to create oxygen vacancies by embedding laser-manufactured metal nanocrystals into TiO2, which significantly boosts carrier mobility and enhances the performance of photoassisted lithium-ion batteries.
How does the proposed mechanism improve carrier dynamics?
The improved carrier dynamics are driven by plasmonic-induced hot electron injection from metal to TiO2 and enhanced conductivity due to oxygen vacancies formed after Schottky contact, leading to better photocharge separation and transport.
What are the benchmark performance values achieved?
The TiO2-based photocathode achieves a capacity of 276 mAh g−1 at 0.2 A g−1 under illumination, a photoconversion efficiency of 1.276% at 3 A g−1, and maintains low capacity and Coulombic efficiency loss over 200 cycles.
What is the significance of this work for energy storage?
This work demonstrates a promising approach to develop highly efficient and stable photoassisted energy storage systems, potentially enabling more compact and integrated solar energy storage devices.
What materials are used in the photocathode?
The photocathode is based on TiO2 nanofibers with embedded plasmonic metal nanocrystals, which form a bulk heterojunction to enhance carrier dynamics.
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