Novel lithium-ion capacitor based on tin phosphide and olive pit derived activated carbon

In this work we report for the first time the use of a carbon coated tin phosphide (Sn4P3@C) composite as the negative electrode in lithium-ion capacitor (LIC) technology. The Sn4P3@C delivers a stable capacity of similar to 900 mAh g(-1) vs. Li+/Li at 0.1 A g(-1), with excellent capacity retention of similar to 55% at 5 A g(-1) (>500 mAh g(-1)) and similar to 30% at 10 A g(-1) (similar to 300 mAh g(-1)). The excellent rate capability properties of Sn4P3@C allow to combine the latter with an olive pit derived activated carbon (AC) as the positive electrode, in a 1 to 5 mass ratio, for the realization of a high energy and high power LIC. For comparison purposes a LIC using the same AC paired with hard carbon (HC), in 1 M LiPF6 EC: DMC electrolyte, was also fabricated. At low power, the new LIC delivers 200 Wh kg(AM)(-1) (per total active mass of both electrodes), twice as much energy of its dual carbon based counterpart. The energy gain remains double until sub-minute discharge times are reached, exceeding power values of 10000 W kg(AM)(-1). However, despite the excellent energy-to-power ratios, cyclability needs to be further improved for the viability of the technology.