Fig. 4

Output electrical performance of BPP-HNG under different external conditions. (a) Output voltages of BPP-HNG with different BTO contents; (b) Output voltages of BPP-HNG with different BTO-PVDF thicknesses; (c) Output voltages of BPP-HNG with different cathode materials; (d) Output performances of BPP-HNG under different pressures; Comparison of the output performances of (e) PENG and BPP-HNG; and (f) TENG and BPP-HNG; (g) The output current and power density of BPP-HNG under different loads; (h) Initial 100 cycles; (i)Stability test of the BPP-HNG.