45Development status and main challenges of bipolar lead-acid battery technology

Development status and main challenges of bipolar lead-acid battery technology

Internationally, bipolar lead-acid batteries are in a state of technological development. British Atraverda company uses their patented Ebonex® conductive ceramic material (titanium oxide with magneli phase, TinO2n-1) and organic binder to make bipolar plates by pressing, and develops GEN12V/24V/36V/48V14Ah series batteries. The American AppliedIntellectualCapital (AIC) company uses the magneli phase titanium oxide material to cover the metal titanium plate to make a bipolar plate. Effpower uses the magneli phase titanium oxide to make porous ceramic bipolar plates, and the active material is filled in the porous ceramic. Although the three companies have different technical routes, they all use the magneli phase titania ceramic material with stable performance in sulfuric acid and close to graphite conductivity as the conductive substrate of the bipolar plate. In China, Hunan Huiyou New Materials Co., Ltd. cooperated with the Chemical Defense Research Institute to develop and research bipolar batteries based on titania conductive ceramics, and a prototype has been produced.

Although bipolar lead-acid batteries have good prospects in design theory, they are currently in the research and development stage, and there is still a certain distance from commercial large-scale production.

Because the structure is different from the traditional lead-acid battery, the technical bottleneck of the bipolar lead acid battery is also somewhat different from that of the traditional lead-acid battery. The main problems are the performance of bipolar plate (including conductivity, strength, impermeability), bipolar plate forming process, suitable active material formula, active material filling and coating process, chemical forming process, assembly and sealing process, etc., all require technical accumulation and improvement. Some key technical challenges of bipolar batteries are as follows:

(1) Although the bipolar lead-acid battery has a simple structure, its production process is relatively complicated. First, it uses bipolar plates. This kind of plate requires positive active material on one side and negative active material on the other side. The middle requires electrons to be conductive and ions to be non-conductive. The production process has higher requirements on equipment and processes. Secondly, the acid filling process is also more complicated, and the internal space of each cell of the bipolar lead battery is relatively small, and the bipolar lead-acid battery is generally designed with a large number of cells, it is difficult to ensure that the acid content in each cell is consistent and the performance of each cell is uniform.

(2) The sealing technology is difficult, and it is difficult to completely seal the cells in the battery. This is also the main reason why it is difficult to promote bipolar batteries at present. At present, bipolar plates are made of lead or other lead-plated metal plates coated with active material materials, which inevitably “creep” during the charging and discharging process of the battery, resulting in the phenomenon of “climbing acid”, which makes the electrolyte between the cells of the battery conduct, and the battery fails.

(3) The heat dissipation design of the battery, how to quickly remove the heat generated during the high current discharge and overcharge of the bipolar battery and prevent the battery from thermal runaway is also one of the difficulties in the design of bipolar lead batteries.