Electrochemical Behavior Of PbO/GO Negative Additives In Lead-acid Battery And Their Effects On Battery Performance

In electric and hybrid vehicles,lead-acid batteries continuously work in a high-rate partial-state-of-charge（HRPSo C）mode,which can cause a large amount of irreversible sulfation in the battery.Carbon materials as additives for negative plates can significantly inhibit the irreversible sulfation of lead-acid batteries,but they also produce severe hydrogen evolution to decrease the battery cycle life.Our research group previously reported that PbO/GO additives can inhibit the hydrogen evolution behavior and significantly increase the HRPSo C cycle life of lead-acid batteries.However,the electrochemical behavior of the PbO/GO additive itself and the optimized content of PbO of the PbO/GO composite have not been clarified.In this thesis,the effect of the PbO content of the PbO/GO composites on the electrochemical performance of these composites and the performance of negative plates and simulated batteries was studied by electrochemical methods,hydrogen evolution tests,and microscopic analysis,while the corresponding mechanisms were also discussed.The main findings are as follows:（1）PbO/GO composites with different PbO contents were prepared by controlling the pickling time in the pyrolysis-acid washing method,i.e.PbO/GO-0min,PbO/GO-2min,PbO/GO-10min,and PbO/GO-1h.With an increase in pickling time,the PbO content reduces largely from 81.43 to 7.18 wt.%and the PbO particles distributed on the surface of GO sheets or wrapped in GO layers decrease significantly.Therefore,the specific surface area,total pore volume,and average pore diameter of the PbO/GO composites are changed.Among them,PbO/GO-10min has the largest specific surface area and total pore volume,and a relatively large average pore diameter.（2）A self-designed model electrode and hydrogen evolution test device were used to study the electrochemical behavior of the different PbO/GO composites in 5 mol/L H₂SO₄.The GO in the PbO/GO composites can be further reduced rapidly during cathodic polarization,and the Pb?Pb SO₄ redox processes and hydrogen evolution process on the composites are significantly promoted.With an increase in the PbO content,both the steady-state and transient hydrogen evolution processes on the PbO/GO composites are inhibited.Among them,PbO/GO-10min has the highest Pb?Pb SO₄ reactivity and a lower hydrogen evolution rate(v _H2).The simulated HRPSo C charge-discharge test found that smaller Pb SO₄crystals can be formed on the PbO/GO-10min surface,which proves that the surface of the PbO/GO composite can provide more nucleation sites for Pb SO₄ crystal growth.（3）Compared with the blank negative plate,the hydrogen evolution on the negative plates containing different PbO/GO composites（except PbO/GO-1h）is significantly suppressed,and the impedance of the plate system is significantly reduced.The addition of the PbO/GO composites promotes the Pb?Pb SO₄ redox processes on the negative plate and increases its specific capacitance value.With an increase in the PbO content,the steady-state or transient v _H2 of the negative plate is decreased,but too high or too low PbO content is not good for its other electrochemical performance,which may be related to the changes in the microstructure of the negative plates.Generally,the negative plate containing PbO/GO-10min has the largest BET area and total pore volume,small average pore diameter,the best electrochemical performance,and small v _H2.Therefore,it has the most excellent comprehensive performance.（4）Compared with the blank battery,the simulated batteries containing different PbO/GO composites have larger battery capacities under different rates and much longer HRPSo C cycle life under 2C rate.The simulated battery containing PbO/GO-10min has a higher C₂₀capacity and dynamic charge acceptance ability,especially,it has the highest HRPSo C cycle life under 2C rate（25108 cycles）.PbO/GO-10min is the best additive and the proper PbO content is the key issue for the PbO/GO additives.