VRLA battery is not ideal in electric vehicles because of its short life under deep charge and discharge cycle conditions. In recent years, with the improvement of positive plate grid materials, the cycle life of batteries has been improved, and the main reason for the failure of VRLA batteries for electric vehicles is the sulfation of the negative electrode. To this end, there are more studies on the negative sulphation of VRLA batteries for electric vehicles, and the negative sulphation project accounts for most of them, especially the research on negative additives to improve the performance of batteries. Adding conductive substances to the negative active substances is one of the effective ways to solve the negative sulphation of VRLA batteries, and carbon black is a cheap and fine negative additive. It can improve the utilization rate and capacity of active substances in the negative electrode of the battery, improve the charging acceptance capacity of the battery, alleviate the sulfation of the negative electrode, and improve the battery's cycle life.

The test battery is a 2V5Ah winding battery (the prototype of the 12V10Ah power winding battery). The positive plate grid is lead-calcium-tin-aluminum-silver alloy, and the negative plate grid is lead-tin alloy. The thickness of the positive and negative plates is 1.0mm and 0.8mm respectively. The negative additive carbon black is imported and the particle size is 300 mesh. The addition amount of the test battery was 0%, 0.3%, 0.6%, 0.9%, 1.2% (the following numbers are 1#, 2#, 3#, 4#, 5#), and the rest of the lead paste formula and plate manufacturing process were equal. Because the test mainly studied negative electrodes, the battery was not set as the negative electrode limit, and the battery was assembled and activated to be tested.

1.1 With the increase of the addition of negative carbon black, the discharge capacity of the battery increases, which means that the utilization rate of negative active substances increases. Compared with the discharge results of 0.5A and 2.0A, the greater the discharge current, the greater the influence of negative carbon black content on discharge capacity. As the discharge product of the negative electrode is a non-conductive PbSO4 crystal, with the discharge process, the non-conductive PbSO4 crystal accumulates around the negative active substance (NAM) lead, preventing the further occurrence of discharge reaction. Carbon black has excellent electrical conductivity, so that the discharge reaction can be further carried out, and the utilization capacity of the active substance is improved. The distribution of carbon black particles in the negative active substance (NAM)

1.2 Test battery capacity test One test battery each. After a full charge, constant discharge of 0.5A and 2.0A current is carried out respectively. The ambient temperature is 25℃. The discharge equipment is a 10A/18V charge and discharge tester controlled by Arbin Company with a microcomputer, and the recording time is set at 1min. The discharge termination voltages were 1.80V and 1.60V respectively, and each experimental battery's discharge capacity (Ah) was obtained according to the computer records.

1.3 Test of experimental battery charging acceptability This index is to assess the degree of difficulty of charging the battery after discharge. According to IEC60896-2-1 (fixed lead-acid battery) 2, the experimental battery is respectively tested for charging acceptability.

One of each experimental battery was discharged with 0.5A current after full charge, the discharge termination voltage was 1.80V, and the capacity of the battery was recorded as CO. Then, it was charged with a constant current of 0.5A and voltage limit of 2.35V for 24h, and then discharged with 0.5A current, the discharge termination was 1.80V, and the capacity of the battery was recorded as C1. Then calculate the battery charging acceptance R24 (%) R24 (%) = (C1×100) /CO according to the following formula

1.4 Test of cycle life of experimental battery under different charging modes @Shibai Charging mode 1: The experimental battery with qualified capacity detection and sufficient charge is discharged at 2.0A, the termination voltage is 1.60V, and then charged at 1A current voltage limit 2.40V for 10h, so cycle, and the discharge time cannot reach 1h36min (80% of the rated capacity). The cycle lifetimes (times) of each experimental battery were obtained from the computer records.

Charging Mode 2: The experimental battery with qualified capacity detection and sufficient electricity is discharged with 2.5A current, the termination voltage is 1.60V, and then charged with 1A current for 5h, and then charged with 0.05A current for 5h, so the cycle is terminated with the discharge time not reaching 1h36min, and the cycle life number (times) of each experimental battery is obtained according to the computer record.

Effect of carbon black content on the discharge capacity of experimental battery;

The results show that with the increase of negative carbon black addition, the discharge capacity of the battery increases, which means that the utilization rate of the negative active substance increases. Compared with the discharge results of 0.5A and 2.0A, the greater the discharge current, the greater the influence of negative carbon black content on discharge capacity.

As the discharge product of the negative electrode is a non-conductive PbSO4 crystal, with the discharge process, the non-conductive PbSO4 crystal accumulates around the negative active substance (NAM) lead, preventing the further occurrence of discharge reaction. Carbon black has excellent electrical conductivity, so that the discharge reaction can be further carried out, and the utilization capacity of the active substance is improved. Distribution of carbon black particles in the negative active substance (NAM).