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Lead-Carbon hybrid ultracapacitors have attracted attention in recent times due to high power density and remarkably long cycling stability. Herein, we report bio-waste orange peel derived B, N doped porous carbons as negative electrode active material for Pb-C hybrid ultracapacitors. B, N doped porous carbons are obtained from orange peel using boric acid by carbonization at 800 °C. B, N doped porous carbons contain about 1.22% of boron, 2.89% of nitrogen. These porous carbons exhibit 866 F g−1 capacitance at 1 A g−1 current density in potential range between the −0.4 V to 0.2 V. Pb-C hybrid ultracapacitors assembled with these carbons as the negative electrode and in situ formed PbO2 as a positive electrode can deliver capacitance of 192 F g−1 at 10 A g−1 and stable over 10,000 cycles. The superior electrochemical performance of lead-carbon ultracapacitor is due to the boron and nitrogen doping into the carbon, which increases the hole density and electron carrier, respectively and subsequently enhances the charge storage property. The significant improvement in capacitance of the ultracapacitor electrode of Pb-C hybrid ultracapacitors presented here opens up a new realm of possibilities for the lead-carbon ultracapacitor development and will contribute directly towards improving the energy and power density of the system.

Lead-carbon hybrid ultracapacitors are being a solution to the lead-acid battery to solve issues of sulfation and improve cycle life. In this work, we present polypyrrole-MoS2–based composite anode material coupled with PbO2 cathode for the lead-carbon hybrid ultracapacitors. Ultracapacitor behavior of polypyrrole-MoS2 based composite shows significant improvement in capacitance and power-density due to the synergetic effect of the high conducting polymer network and redox behavior of MoS2. The nanopetal shaped composite materials have been synthesized by a simple hydrothermal method at 160 oC by using polypyrrole. The composite Polypyrrole-MoS2 electrode delivers a specific capacitance of 782 Fg−1 at 1 A g−1 current density with low areal specificresistance (1.15 Ohm cm2) in an aqueous H2SO4 electrolyte. Besides, the PbO2/Polypyrrole-MoS2 hybrid ultracapacitors deliver capacitance of 285 F g−1 at 5 A g−1 and stable over 10,000 cycles. The improved capacitive behavior of the Polypyrrole-MoS2 composite electrode is due to the redox behavior, effective intercalation of H+ ions into the composite frameworks by transporting the electrons as well as have easy doping/de-doping of sulfate ions to the polypyrrole network.

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Sulfation at the negative electrode and grid corrosion at the positive electrode are the major failure modes of lead-acid batteries. To overcome the issues of sulfation, we synthesize carbon coating onto SnO2 as a negative electrode additive for lead-acid batteries. 0.25 wt% of carbon-SnO2 additive into the negative active material reduces formation cycle from 3 cycles to 1 cycle and 60% increment in capacity during the 1st cycle compare to conventional lead-acid cell. The additive cells also deliver 300 deep charge-discharge cycles at C/5 rate and >60% increase in capacity at 2C rate in relation to conventional lead-acid cells. The enhancement in capacity at all C rates and improvement in cycling is due to carbon coating which enhances the conductivity and charge storage property of negative active material. Carbon-SnO2 occupies in the pores of negative active material, restricts the growth of PbSO4 and decreases hydrogen evolution, thereby improves charge acceptance. Besides, the additive cells show 300% increase in high rate partial state of charge cycles compare to conventional lead-acid cells. The specific capacitance of carbon coated SnO2 in 4.5 M H2SO4 is 150 F g−1, at 2A g−1 with >90% capacity retention after 2000 cycles.

We herein report a method for reducing lead-alloy positive grid corrosion in lead acid batteries by developing a polypyrrole (ppy) coating on to the surface of lead-alloy grids through potentiostatic polymerization technique. The experimental results demonstrate that the presence of ppy coating significantly enhances the corrosion resistance and inhibits the oxygen evolution rate as compare to bare grids. C-rate studies of 2 V/2.6 Ah lead-acid cells show ∼15-20% improvement in capacity at low charge-discharge rates (C/20-C/5) and ∼10% at high C rates (C/2 and 3C) for the cells with ppy coating grids in relation to conventional lead-acid cells.

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