Low power metal corrosion seawater battery
Low power seawater battery appeared earlier. The goal of studying this kind of battery is to find a battery with reasonable structure, relatively low cost and suitable for use in seawater at different depths.
The US Navy has conducted systematic research for military purposes, but the results have not been made public.
With the miniaturization and low power of various electronic detection equipment, this field has attracted people's attention. It is generally believed that seawater battery is more suitable for providing low-power power power supply for a long time in the marine environment, which creates an opportunity for it to provide power for marine exploration devices.
In this regard, Keng batteries and Fu nickel batteries are mostly used. File batteries are expensive and their service life and safety in seawater need to be improved. Although tin nickel batteries have good performance, they have an impact on the environment. The use of these two types of batteries needs to be placed in specific pressure vessels, and the overall technical requirements are relatively high.
The research on seawater battery shows that selecting a suitable electric pair can provide a voltage of about 1.0V when it is open to seawater, which can basically meet the requirements of small detection elements. Seawater battery provides anode discharge current by relying on the corrosion and dissolution of negative metal materials in seawater, The positive electrode mainly relies on the dissolved oxygen in seawater for reduction reaction on the inert gas electrode to provide positive current. The maintenance time is relatively long, and the cost and structure are easy to accept. Therefore, it has development value.
The cathode of the battery is equivalent to a gas electrode and needs suitable conductive materials. The research objects include graphite, copper and stainless steel. Graphite can obtain a greater open circuit potential than copper and stainless steel, but it is too brittle. A fixed structure needs to be designed to strengthen the cathode structure.
Due to the limited dissolved oxygen in seawater, the current of electric pair is relatively small. In order to ensure sufficient current, a large area of cathode is required; Of course, the current density of the battery can also be increased by increasing the alkalinity of seawater, such as adding KOH solution. However, after the alkalinity is enhanced, insoluble salts such as Mg (OH) 2 and Ca (OH) 2 will be generated near the cathode electrode, which will reduce the electrical performance of the electrode. Therefore, it is very important to ensure sufficient dissolved oxygen concentration when considering the electrolyte of seawater battery.
Copper and stainless steel are ideal materials for cathodes with sufficient area and compact structure.
In shallow water, the beneficial biofilm formed on the surface of stainless steel after 1 ~ 3 weeks is better than that of copper. In deep water (greater than 2000m), there is no sufficient evidence that biofilm formed on copper surface is beneficial.