Recycling Of Electrode Active Materials From Spent Lead Acid Batteries

In view of the distinctive advantages of mature manufacturing technology, low price, high reliability and high safety, lead acid batteries (LABs) have been widely used as the power source in electric bicycles,SLI (starter,lights and ignition) batteries,UPS,and especially, large scale energy storage for renewable energy sources. The widespread and ever-increasing use of lead acid batteries also leads to an increasing generation of spent LABs. It is important to invent new routes for efficient, economic and environment-friendly recycling of spent lead acid batteries (SLABs). Based on full separation of the SLABs, positive and negative active materials were produced separately from the corresponding spent lead pastes. This method can avoid the adverse effects of impurities (such as BaSO4) on the recycled positive active material.In this thesis, the processes of recycling the positive and negative materials in spent lead acid batteries were investigated. The major contents of this thesis are as follows:1?This part reports preparation and electrochemical property of a-PbO from the spent negative material which is compose of PbSO4 (the major phase) and Pb (the minor phase). To make things simpler, pure PbSO4 is firstly used as the model compound and desulfated with(NH4)2CO3 to obtain PbCO3, which is then calcined in air at different temperatures to produce PbO. At 450?, the calcination produces pure ?-PbO, which can still discharge a capacity of 98.6 mAh·g-1 after 50 cycles of 100% DOD at 120 mA·g-1. By using the same procedures, the real spent negative powder is also treated to produce pure a-PbO, which discharges a similar capacity of 100 mAh·g-1 at 120 mA·g-1. This is 25% higher than that of industrial leady oxide.These results show that the small amount of metallic lead has little effect on the treatment.2.This part reports preparation and electrochemical property of lead oxide from the spent positive material which is compose of PbSO4 and PbO2. PbSO4 is desulfated with (NH4)2CO3 to obtain PbCO3, the mixture of PbCO3 and PbO2 is then calcined in air to produce PbO. At 550?, the calcination produces a mixture of a-PbO, Pb3O4 and ?-PbO, which can be directly used as PAM of brand new LABs. After formation, the electrode contains ?-PbO2 (the major phase) and a-PbO2 (the minor phase),which can still discharge a capacity of 97.8 mAh·g-1 after 50 cycles of 100% DOD at 100 mA·g-.3.This part reports the room temperature reduction of PbO2 by oxalic acid and the subsequent calcination to produce PbO as positive active martial (PAM). The results show that the reduction does produce the intermediate H2O2, but it cannot be achieved completely at room temperature, probably due to the PbC2O4 coat on PbO2; the residual PbO2 can be reduced by CO formed during calcination of PbC2O4; the calcination at 450 0C of the PbC2O4 coated PbO2 in air produces fine particles of sponge-like mixture of a-PbO and Pb3O4, which can be directly used as PAM of brand new LABs. After formation, the electrode shows a hollow urchin-like structure composed of many interconnected nano-whiskers,which can still discharge a capacity of 115.2 mAh·g-1 after 50 cycles of 100% DOD at 100 mA·g-1.4.This part reports reduction of PbO2 by formic acid and the subsequent precipitation reaction to produce PbSO4. PbO2 is reduced and dissolved by formic acid solution, which can react with H2SO4 solution to produce PbSO4. The reacted solution which contained formic acid can be further used to reduce PbO2 by adding the lacked formic acid. By using the same procedures, the real spent positive powder is also treated to produce pure PbSO4 rods with 1?m in diameter and 2?6 ?m in length, which can be desulfated with (NH4)2CO3 to produce PbCO3. At 450?,the calcination produces a-PbO and Pb3O4 spherical particles with wrinkles on the surface. PbSO4 rods and lead oxide spherical particles as PAM can still discharge capacities of 85.4 and 107.1 mAh·g-1 after 50 cycles of 100% DOD at 100 mA·g-1, which are 8% and 35% higher than that of industrial leady oxide, respectively.