Controlling the residual charge to alleviate the frequency dependence of ternary direct current triboelectric nanogenerators

Recently, the ternary direct current triboelectric nanogenerators (T-DC-TENGs), especially those working in rotation mode, have received much attentions due to their high DC output and superior durability. However, the frequency dependence of T-DC-TENG was largely ignored, which greatly hinders the miniaturization of the device. Because the electron-donating capacity of positive tribo-layer is unequal to the electron-gaining capacity of negative tribo-layer, the number of residual charges on the intermediate triboelectric layer due to not instant dissipation depends on the rotation frequency of T-DC-TENGs. At higher frequency, the more undissipated residual charges will exemplify their effect on the triboelectrification process and limit the output of T-DC-TENGs. Herein, we disclose these residual charges first and then their frequency dependent effect on triboelectrification in T-DC-TENGs. In this study, a charge collecting electrode (CCE) is introduced to construct an electrostatic breakdown T-DC-TENG (EBT-DC-TENG) with greatly reduced frequency dependence. By efficiently reducing the residual charges, the charge density output of EBT-DC-TENG is increased by 51.75% at 90 rpm (from 145.7 to 221.1 μC m−2 r−1) compared with T-DC-TENG without CCE. Furthermore, with the help of its soft property, the less residual charges accumulated polyester fur enables EBT-DC-TENG to maintain 100% output without wear after 10,000 cycles. This EBT-DC-TENG with a better crest factor of 1.028 can continuously power 1200 LEDs in series connection, showing unique advantages in harvesting environmental energy steadily and efficiently. This work also provides a theoretical and practical path for the miniaturization of the rotating mode T-DC-TENG.