Sulfation on coated carbon related to lead ion and its effect on the performance of advanced ultra-battery at high rate

Abstract The ultra-battery is a kind of advanced power type lead-carbon battery, which is adept in cycling under high rate and partial state of charge. The sulfation in the lead paste of the negative electrode is considered as a key factor which affects the performance of the ultra-battery. Meanwhile, because the free lead ions would contact with the coated carbon and the working potential of the coated carbon is close to the lead paste, the sulfation also occurs in the coated carbon, which in turn affects the performance of carbon materials. However, there has been limited work to explore the sulfation on the coated carbon. In this paper, a variety of physical characterizations and electrochemical research methods are used to study the sulfation process on the coated carbon. The results show that the reduction potential of lead ions on the coated carbon is more negative than that on the lead paste during high-rate cycling, resulting in more serious sulfation occurred on the coated carbon. And the sulfation is more likely to occur in the place where coated carbon is adjacent to the lead paste. This side reaction has a great influence on the performance of the ultra-battery at high-rate. When the PVA gel obtained by the sol-gel method is used to inhibit the sulfation on the coated carbon, the energy retention rate of the ultra-battery is increased from 76.01% to 83.75% after 2000 cycles at 1 A g-1 under 100% DOD, and the charge and discharge efficiency of the ultra-battery is increased from 44.12% to 97.45%.