Synthesis Of Rice Husk-derived Hierarchical Porous Carbon-Based Additives And Their Application In Negative Electrodes Of Lead-Carbon Battery Towards Energy Storage

Energy storage system with low cost and high safety is the key part of future smart grid,which will play important roles in the fields of renewable energy generation,peak load shifting,and power quality improvement.Among the secondary battery technologies,lead-acid battery stands out for its characteristics such as good safety,low manufacturing cost,mature manufacturing basis and well-developed recycling system,which is one of the ideal choices for battery energy storage.In energy storage system,lead-acid battery works under partial-state-of-charge?PSoC?operation,and its main failure mode is the sulfation of negative electrodes.The sulfation of negative electrode results in the decrease of porosity,reaction activity and capacity of lead-acid battery.Nevertheless,developments of new materials,especially the carbon additives used for negative electrodes exhibit prospects to prolong the cycling life of lead-carbon batteries.The purpose of this paper is to prepare high performance rice husk-based carbon additives,and to study the mechanisms of the rice husk-based carbon additives in lead-carbon electrodes under the mode of energy storage,so as to provide support for the development of lead-carbon batteries.The main results of research are as follows1.The application characteristics and mechanism of rice-husk-derived hierarchical porous carbon,RHHPC used as carbon additive in lead-carbon electrode has been studied.Compared with graphite,carbon black and commercial activated carbon,RHHPC exhibits good effect on enlarging electrochemically active surface area of lead-carbon electrode.Because the unique hierarchical pores of RHHPC provide active sites for Pb deposition and Pb branches to grow,the electrochemically active surface area of lead-carbon electrode is enlarged,and subsequently the reversibility of lead-carbon electrode is improved.As a result,the charging acceptance of RHHPC cell maintains good,which is higher than the reference cells at the end of deep charge/discharge PSoC test,and its 1C₁ specific discharge capacity is 83.3mAh·g^-1.However,carbon additives accelerate the hydrogen evolution of lead-carbon electrode,which limits the reversibility of lead-carbon electrode.2.Based on RHHPC with hierarchical porous structure used as carbon skeleton,a new lead coated-carbon?Pb/C?composite is prepared by electroless plating to inhibit hydrogen evolution,and improve the cycling reversibility of lead-carbon electrode.The Pb/C composite with a high specific surface area(669.7 m²·g^-1)and mesoporous volume(0.28 cm³·g^-1)is uniformly coated by lead.The lead-carbon electrode containing Pb/C composite with a lead loading of 9.59%shows a good effect on inhibiting hydrogen evolution.Therefore,the addition of Pb/C composite materials effectively enhances the rate performance and reversibility of lead-carbon electrode.The specific discharge capacities of Pb/C cell with the current densities of 0.1C₁₀ and1C₁ are 133.3 and 87.8 mAh·g^-1,respectively.In the deep charge/discharge PSoC test,the discharge capacity of RHHPC@PbO_1-x cell at 90^th cycle is still as high as 62.5%of its initial capacity,and its capacity is 2.2 that of the blank cell and 1.6 that of the RHHPC cell.3.The influence of different lead loadings of Pb/C composites on the electrochemical behaviors of lead-carbon electrodes are studied.Results show that with the increase of lead loading,the specific surface area and pore volume of Pb/C composites decrease,the conductivity of Pb/C composites increases,and the hydrogen evolution rates of their corresponding lead-carbon electrodes decrease.At the same time,with the lead loading increasing,the electrochemically active surface area of lead-carbon electrode increases first and then decreases.With ca.3 wt.%lead loading of Pb/C composite,the lead-carbon electrode exhibits the highest electrochemically active surface area and the longest high-rate partial state of charge?HRPSoC?cycling life,up to 10554 cycles which is 11 times that of the blank battery.4.A carbon@lead(RHHPC@PbO_1-x)composite is rationally designed and synthesized for simple-preparation,low-cost and large-scale production.The RHHPC@PbO_1-x with uniform and compact nano-sized lead oxide coating on its surface exhibits high specific surface area(1111.3 m²·g^-1)and mesopore volume(0.29cm³·g^-1),as well as a stable RHHPC/Pb/PbO three-phase composite structure.The specific discharge capacities of RHHPC@PbO_1-x cell with the current densities of0.1C₁₀ and 1C₁ are 147.4 and 93.7 mAh·g^-1,respectively.After 350 deep charge/discharge PSoC cycles,the discharge capacity of RHHPC@PbO_1-x cell is still as high as 96.4%of its initial capacity,and its cycling life is fourfold that of the blank cell and twice that of the RHHPC cell.