High Energy and High Power Lithium‐Ion Hybrid Supercapacitors with Prolonged Cycle Life Based on High‐Rate Capability Materials: Li 4 Ti 5 O 12 , Activated Carbon, Li 3 V 1.95 Ni 0.05 (PO 4 ) 3 /C

Two lithium‐ion hybrid supercapacitors (LiHSs) based on high power active materials like Li 3 V 1.95 Ni 0.05 (PO 4 ) 3 /C (LVNP/C), Li 4 Ti 5 O 12 (LTO) and activated carbon (AC) are investigated as high energy and high power devices. Both LiHSs are assembled by using a bi‐material negative LTO:AC electrode (50 : 50), able to deliver 38.3 mAh g −1 at 35 A g −1 (200 C for LTO), and to retain 80 % of the initial capacity over 10000 cycles at 17.5 A g −1 . Two positive electrodes are employed in complete devices: a battery‐type LVNP/C and a bi‐material LVNP/C:AC (65 : 35) based electrodes, for two LiHSs named Hybrid A and Hybrid B, respectively. The energies of the LiHSs are evaluated from 0.05 to 10 A g −1 , and at different cell voltages (2.6, 2.7 and 2.8 V). The best performance is obtained with Hybrid A cycled between 0–2.7 V, that with 36.3 Wh L −1 at 4.3 kW L −1 , possesses an energy density five time higher than that of the AC||AC (6.8 Wh L −1 ). Despite both LiHSs charged up to 2.8 V possess superior energy values, at this cell voltage Hybrid A and Hybrid B retain only 11 % and 8 % of the initial capacity cycled over 8000 cycles at 10 A g −1 , respect to the 75 % and 81 % of the same systems cycled up to 2.7 V.