How does electrode spacing affect the performance of a TENG?

Electrode spacing in a TENG significantly affects its performance by influencing both the capacitance and the electric field distribution within the device. Smaller electrode spacing generally leads to higher capacitance, according to the formula C = εA/d, where C is capacitance, ε is the permittivity of the dielectric material between the electrodes, A is the area of the electrodes, and d is the distance between them. Higher capacitance can improve charge storage and current output. However, extremely small spacing may increase the risk of electrical breakdown or short circuits, especially in high-voltage TENGs. Larger electrode spacing, on the other hand, reduces the capacitance but can increase the open-circuit voltage. This is because a larger separation distance allows for a greater potential difference to develop between the electrodes due to the triboelectric charge. The electric field distribution also depends on the electrode spacing; a non-uniform electric field can lead to inefficient charge collection. Therefore, an optimal electrode spacing must be carefully chosen to balance the trade-offs between capacitance, voltage, and electric field uniformity to maximize the overall TENG performance. For instance, in a contact-separation TENG, the spacing during the separation phase is critical; a larger separation distance results in a higher voltage output, but the initial spacing when the surfaces are in contact also influences the initial capacitance and charge distribution.