Triboelectric Nanogenerator (TENG) is a mechanical energy harvesting technology with the potential to autonomously power future wearable and portable electronics. Triboelectric charging is the major phenomenon governing the power generation and efficiency of a TENG. Studies on TENG, thus far, have focussed on the symmetric triboelectric charging with equal amounts of triboelectric charges with opposite polarities distributed on its two contact surfaces, especially for the purpose of theoretical modelling and simulations. Our work presents a fundamental study on the asymmetric triboelectric charging with unequal quantities of charges on TENG contact surfaces obtained through an external charging method, as an effective technique to enhance its power generation. For the first time, a theoretical model which can simulate the outputs of an asymmetrically charged TENG is derived using the distance-dependent electric field concept and experimentally verified, providing a detailed understanding of this phenomenon. The asymmetric charging is experimentally demonstrated to enhance the average power outputs of TENGs containing dissimilar contact surfaces (469% improvement) and identical contact surfaces (6076% improvement). Therefore, this study introduces a method to use identical triboelectric materials as TENG contact surfaces and generate comparable outputs to triboelectrically dissimilar materials, which significantly enhances the material range compatible for TENGs. Furthermore, we provide an insight into materials transfer characteristics between TENG contact surfaces and its impact on the non-linear external charging behaviour, revealing several crucial parameters which affect the efficiency and consistency of a TENG. Finally, this work elaborates on the TENG surface contaminations during experimental practices and the importance of TENG fabrication and characterisation procedures towards their long-term applications.

摩擦纳米发电机 (TENG) 是一种机械能量收集技术，具有为未来可穿戴和便携式电子设备自动供电的潜力。摩擦充电是控制 TENG 发电和效率的主要现象。迄今为止，对 TENG 的研究主要集中在对称摩擦充电上，在其两个接触表面上分布有等量的相反极性的摩擦电荷，特别是出于理论建模和模拟的目的。我们的工作对通过外部充电方法获得的 TENG 接触表面上不等量电荷的不对称摩擦充电进行了基础研究，作为提高其发电的有效技术。首次，使用与距离相关的电场概念推导出了一个可以模拟不对称带电 TENG 输出的理论模型，并通过实验验证，提供了对这种现象的详细理解。实验证明不对称充电可以提高包含不同接触面（提高 469%）和相同接触面（提高 6076%）的 TENG 的平均功率输出。因此，本研究介绍了一种使用相同摩擦电材料作为 TENG 接触面并产生与摩擦电不同材料相当的输出的方法，这显着提高了与 TENG 兼容的材料范围。此外，我们深入了解了 TENG 接触面之间的材料转移特性及其对非线性外部充电行为的影响，揭示了影响 TENG 效率和一致性的几个关键参数。最后，这项工作详细说明了实验实践中 TENG 表面污染以及 TENG 制造和表征程序对其长期应用的重要性。