| The history of lead-acid batteries has been more than 150 years.Due to its high cost performance,stability and reliability,it is widely used in automotive start-up power supplies,electric bicycle power supplies and uninterruptible power supplies.With the rapid development of the automotive industry and the electric bicycle industry,lead-acid batteries have ushered in large-scale use,and a large number of used lead-acid batteries have also been produced.If this problem is not handled properly,it will cause environmental pollution and threaten human health.Therefore,the development of green,economic,and environmentally friendly new processes is of great significance to the healthy and sustainable development of the lead-acid battery industry.In this paper,the process of chemical separation of lead paste obtained by four separations to prepare lead sulfate?PbSO4?and tetrabasic lead sulphate?4BS?was studied,and they were used as the negative electrode and positive electrode active material of lead-acid battery respectively,and the electrochemical performance of the lead acid battery was studied.The main contents are as follows:1.The lead paste composition of the waste lead-acid battery was studied,and the lead paste was characterized and the content was determined.The XRD pattern indicates that the lead paste mainly contains lead oxide,lead,lead sulfate,lead dioxide and tribasic lead sulfate.Chemical analysis is used to determine the content of each component of the lead paste.The results show that the the content of PbO,Pb,PbSO4 and PbO2 in the lead paste used in this paper is 15.40%,2.76%,35.98%,40.60%,respectively,and the total lead content is 76.79%.Subsequent four-factor and three-level orthogonal experiments confirmed that the optimal conditions for the reduction of formic acid lead paste were:n?HCOOH?:n?Pb?ratio of 6,reaction temperature of 100°C,reaction time of 6 h,the stirring rate is 400 r/min.At this time,the lead recovery rate is up to 97.11%,and the insoluble matter rate is at least 8.28%.The insoluble matter contains metal elements such as Pb,Sb,and Ba,and the insoluble matter can be further added to the next formic acid reduction process to continue to recover the Pb element.Elements such as Ba and Sb can also be recovered by appropriate chemical processes.2.The method for synthesizing PbSO4 from the lead salt obtained by the above method was studied,and four samples with slightly different morphology were obtained?hereinafter referred to as S1,S2,S3,and S4?.Samples S1 and S2 were obtained by directly mixing H2SO4 and?NH4?2SO4 with a lead salt solution in a 1:1molar ratio in a three-necked flask;The S3 and S4 samples were obtained by mixing a H2SO4 solution and?NH4?2SO4 with a lead salt solution in a 1:1 molar ratio using a peristaltic pump in a Y-tube..Using them as negative electrode active materials,respectively,under the conditions of discharge depth?DOD?of 100%and discharge current density of 100 mAh·g-1,the cycle specific capacities of the four electrodes were 106.47 mAh·g-1 and 106.45 mAh·g-1,107.40 mAh·g-1,106.50 mAh·g-1,the four electrodes are not much different,and both show good electrochemical performance and cycle stability.However,the S3 electrode performed slightly better than the other three electrodes under different discharge regimes.In addition,after 300 cycles,the four electrodes were still able to maintain an initial steady state capacity of more than80%.Therefore,lead sulfate synthesized in this experiment is suitable as a negative electrode active material for lead-acid batteries.3.A method for synthesizing tetrabasic lead sulfate?4BS?from lead salts recovered from used lead-acid batteries was studied.The obtained 4BS is a prismatic particle having a length of 5 to 10?m and a width of 1 to 2?m.When used as a positive electrode active material for lead-acid batteries,the discharge specific capacity is 92.97 mAh·g-1 after 100 cycles of complete charge and discharge at a discharge depth of 100%and a discharge current density of 100 mAh·g-1,The 4BS electrode still maintains an 80%initial steady state capacity after 370 full charge and discharge cycles.The rate performance of the test electrode after 100 cycles,the electrode still exhibits better electrochemical performance at different discharge current densities.Subsequently,a grid with different mesh sizes was used and a 4BS electrode was prepared by adding 0.3%and 0.4%graphite.It was found that a grid with a small mesh and 0.4%graphite were added to facilitate the cycle stability and discharge capacity of the electrode.The capacity of the electrode after 80 cycles is still 101.60 mAh·g-1... |
PDF Full Text Request