Electrochemical evaluation of Pb-Ca-Sn- Sr alloy for positive grid of lead-acid battery

Optimizing the electrochemical and mechanical properties of the positive grid of lead-acid batteries exert a great influence on their performance.High content of Ca in Pb-Ca-Sn alloy causes premature capacity loss,while reducing its content brings about losing hardness and casting ability. This issue can be solved by use of Strontium as the fourth element in positive grid alloy.In this study we prepared Four different alloys with Sr content of 0.012% to 0.060% and same Ca and Sn values to compare with a reference sample without Sr. Cyclic Voltammetry,Potentiostatic,electrochemical impedance spectroscopy and hardness tests were conducted on all samples.The results indicate that adding Sr improves the performance of the grid alloy in all mentioned tests and the best results observed when Sr were used in the range of 0.012% to 0.020%.Based on hardness and electrochemical tests results, the best sample was chosen for preparing a 66 Ah battery and tests it according to PSA standard,including Capacity,CCA,Charge Acceptance and Cycling to compared with the alloy without Sr. The results shows that employing 0.020% of Sr in the grid alloy resulted in four-time lower passive current density,41% lower PbO formation peak,70% lower O2 evolution rate,55% increased electrochemical impedance of the oxides formed on the electrode surface and 16% increase hardness, comparing to reference alloy without Sr addition.Battery performance tests results were also in line with electrochemical ones,Sr improved the CCA of the battery 10%, enhanced charge acceptance 37%, prolonged battery cycling test 44% and resulted is 57% lower residual capacity loss after cycle life.