Abstract
Abstract Energy storage is an integral part of the modern world. One of the newest and most interesting concepts is the internal hybridization achieved in metal-ion capacitors. In this study, for the first time we used sodium borohydride (NaBH4) as a sacrificial material for the preparation of next-generation sodium-ion capacitors (NICs). NaBH4 is a material with large irreversible capacity of ca. 700 mA h g−1 at very low extraction potential close to 2.4 vs Na+/Na0. An assembled NIC cell with the composite-positive electrode (activated carbon/NaBH4) and hard carbon as the negative one operates in the voltage range from 2.2 to 3.8 V for 5,000 cycles and retains 92% of its initial capacitance. The presented NIC has good efficiency >98% and energy density of ca. 18 W h kg−1 at power 2 kW kg−1 which is more than the energy (7 W h kg−1 at 2 kW kg−1) of an electrical double-layer capacitor (EDLC) operating at voltage 2.7 V with the equivalent components as in NIC. Tin phosphide (Sn4P3) as a negative electrode allowed the reaching of higher values of the specific energy density 33 W h kg−1 (ca. four times higher than EDLC) at the power density of 2 kW kg−1, with only 1% of capacity loss upon 5,000 cycles and efficiency >99%.
Highlights
Energy storage is an integral part of the modern world
The results presented in this study confirms that all NaBH4 is irreversibly extracted, while the BH−4 anion is electrochemically oxidized and can be removed from the cell while not decreasing the specific energy and power of the next-generation sodium-ion capacitors (NICs) cell
galvanostatic charge/discharge with potential limitation (GCPL) on the Na2BCN/activated carbon (AC) composite-positive electrode was done at C/20, and the potential range was the same as for the cyclic voltammetry (CV) investigation
Summary
Abstract: Energy storage is an integral part of the modern world. One of the newest and most interesting concepts is the internal hybridization achieved in metal-ion capacitors. For the first time we used sodium borohydride (NaBH4) as a sacrificial material for the preparation of next-generation sodium-ion capacitors (NICs). An assembled NIC cell with the compositepositive electrode (activated carbon/NaBH4) and hard carbon as the negative one operates in the voltage range from 2.2 to 3.8 V for 5,000 cycles and retains 92% of its initial capacitance. 18 W h kg−1 at power 2 kW kg−1 which is more than the energy (7 W h kg−1 at 2 kW kg−1) of an electrical double-layer capacitor (EDLC) operating at voltage 2.7 V with the equivalent components as in NIC. Four times higher than EDLC) at the power density of 2 kW kg−1, with only 1% of capacity loss upon 5,000 cycles and efficiency >99% Tin phosphide (Sn4P3) as a negative electrode allowed the reaching of higher values of the specific energy density 33 W h kg−1 (ca. four times higher than EDLC) at the power density of 2 kW kg−1, with only 1% of capacity loss upon 5,000 cycles and efficiency >99%
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