The bipolar lead acid battery uses light acid-resistant conductive material as the current collector, and the positive and negative lead storage batteries are filled on both sides of the current collector respectively. The 2V working unit of the battery is: a positive surface is opposite to a negative surface, and a separator (such as an AGM separator) is placed in the middle for isolation. The surrounding is sealed with a plastic frame to form a battery compartment. The battery compartment is filled with sulfuric acid electrolyte to form a 2V working unit. Multiple 2V cells are continuously stacked and connected in series to form a single battery with a design demand voltage. The capacity of the battery depends on the size of the individual pole pieces. The difference from traditional batteries is that bipolar lead acid batteries can be connected in series to obtain high-voltage single-cell batteries, and the single-cell voltage can reach more than 200V, while the capacity is limited by the single-piece electrode plate. If you want to increase the capacity, you need to increase the plate area, or you can only connect the batteries in parallel through an external circuit. In traditional batteries, the plates can be connected in parallel inside the same single battery to obtain larger capacity. The voltage of the single battery generally does not exceed 36V. If a single battery with a voltage of 144V is to be obtained, an external circuit is generally used in series.
The main advantages of bipolar lead acid batteries are as follows:
(1) Low internal resistance and high power characteristics. Bipolar lead acid battery current is perpendicular to the electrode plane and only passes through the thin bipolar electrodes. Compared with the conduction current of the ordinary lead acid battery through the grid and the connecting bar between the single cells, the bipolar lead battery provides a short distance for current passing, a large cross-sectional area, almost no internal resistance between single cells, and the total internal resistance is about 1/5 of that of ordinary batteries. According to the parameters of Atraverda and Effpower, the internal resistance is about 0.1~30mn, while the traditional lead acid battery is about 80mfi. Due to the significant reduction in the internal resistance consumption of the battery during high-current charging and discharging, the power performance is significantly improved, and its specific power can be close to 1000W/kg.
(2) Higher specific energy. The bipolar lead acid battery simplifies many structures of the common lead acid battery, saves the busbar and the connecting bar between the single cells, and does not need the partition between the cells, which greatly reduces the battery quality and improves the specific energy of the battery. The higher the voltage, the more obvious its volume-specific energy advantage.
(3) The utilization rate of battery active material is high. The polar plates of bipolar batteries are stacked in parallel, and the current transfer is different from the way of collecting the tabs of traditional batteries, and the current is distributed in parallel rather than gradient, so the utilization rate of the active material is theoretically completely uniform throughout the plate, while the traditional battery has the phenomenon of uneven utilization at the top and bottom of the plate. Therefore, the utilization rate of active materials in bipolar batteries is higher, and the current density distribution is more uniform.
(4) The quality is small. Since bipolar lead acid batteries use lightweight materials as current collectors to replace the lead grids of traditional batteries, the mass is reduced by more than 30%.
(5) Long life. According to the current 2V battery test results, the same battery can be doubled in cycle life when placed horizontally than when placed vertically. However, due to the production process and structure of ordinary 6V or 12V lead batteries, the plates must be placed vertically, and the plates of bipolar lead acid batteries can be placed horizontally. Horizontal laying can effectively prevent the delamination of the electrolyte during the circulation process, and at the same time reduce the stripping of the active material, so that the service life of the battery can be doubled.
(6) Suitable for high voltage design. The high-voltage design can effectively reduce the power consumption in the transformation process and improve the energy utilization rate. The voltage of a single battery of an ordinary lead acid battery is generally only up to 12V. If a high voltage is required, multiple batteries need to be connected in series. Due to its structural characteristics, the bipolar lead acid battery can be directly designed to be high voltage. It is only necessary to increase the number of bipolar plates used according to the voltage to be achieved, and the highest can even reach more than 100V.
The main disadvantages of bipolar lead acid batteries are as follows:
(1) For bipolar lead acid batteries, since the bipolar plate not only acts as a current collector, but also acts as the partition wall of the battery cell system, the bipolar plate has high requirements on the strength, conductivity and anti-penetration and leakage performance indicators, so the failure rate of the battery will be relatively high.
(2) Since the capacity of a single bipolar plate determines the capacity of a single battery, and the area of the electrode plate is too large, the deformation resistance and leakage of the electrode plate will be affected. Therefore, it is relatively difficult to make bipolar lead acid batteries as large-capacity batteries.
(3) Compared with traditional batteries, the production process of bipolar lead acid batteries has strict requirements on technical processes such as bipolar plate production, smearing, chemical formation, and sealing, and the technical difficulty is high.