American scholars use lithium battery electrodes to increase lithium concentration in seawater

With the increasing use of electronic products and electric vehicles, the demand for lithium batteries and their important raw material, lithium, has grown exponentially. However, the lithium resources on land are limited after all, and many scientists have turned their attention to the oceans that contain huge amounts of lithium resources. However, the lithium content in seawater is extremely low, and it is very difficult to extract lithium from seawater, and it has never been put into large-scale application. However, a recent achievement by American scholars is of great significance for the promotion of lithium extraction overseas.

It is estimated that there are 180 billion tons of lithium in seawater, and the current global annual demand for lithium exceeds 160,000 tons. Even if the demand increases 10 times in the next ten years, the supply of lithium resources in seawater is more than enough. However, the seawater contains only two parts per million lithium, and coexists with metals such as sodium and magnesium, making it difficult to extract lithium.

A group of scholars from Stanford University recently published an article in the world-renowned academic journal "Joule", saying that they used lithium battery positive and negative electrodes to successfully increase the concentration of lithium in seawater, so that overseas lithium can be economically mass-produced. One step forward.

Lithium ion battery is a kind of rechargeable battery, it mainly relies on the movement of lithium ion between positive electrode and negative electrode to work. Lithium ion batteries use an intercalated lithium compound as an electrode material, such as lithium iron phosphate, lithium cobalt oxide, and so on.

Breakthrough

To increase the lithium content in seawater, you can evaporate most of the water (H2O) in seawater, but this takes time and a large area to increase the lithium concentration like sun salt. Stanford scholars have tried to use lithium-ion battery electrodes to extract lithium directly from seawater and brine without evaporating the water.

In seawater, the negative voltage can cause lithium ions to be adsorbed on the electrode, thereby pulling the lithium ions into the electrode. But it also absorbs chemically similar sodium, which contains about 100,000 times the sodium content in seawater. If these two elements enter the electrode at the same rate, sodium almost completely squeezes out the lithium.

Stanford's solution is: First, apply a thin layer of titanium dioxide on the electrode so that smaller lithium ions can enter the electrode more easily; Second, do not apply a constant negative voltage to the electrode. The cycle of shutdown, positive voltage, and short shutdown, because the electrode material has a stronger affinity for lithium, so that more lithium can be absorbed in the electrode. After 10 simple cycles, the researchers obtained 1:1 lithium and sodium.

However, the economics of this scheme currently do not have an advantage, which is not enough to compare with the cost of developing lithium mines on land. The research team is using Other raw materials to test whether it can reduce the cost of lithium.