Lets be clear from the outset, my only interest in cars is to get from A to B, if I can do this cleanly why not. Many environmentalists tell us to go electric. In this essay we will explore the chemistry of electric cars and their impact on the environment. So please don’t get the canned soap to throw on petrol cars yet.
Lets first plunge into the history of batteries, for this we start of with two Italians Luigi Galvini and Alessandro Volta. Galvini noticed that legs from dead frogs would move when two different metals were placed on them. He thought this energy was coming from the legs themself. Volta disagreed, to prove his point he built the voltaic pile. Using copper and zinc metal strips seperated by cloth or cardboard soaked in a salt solution. It was then established by Volta that the energy in the frogs legs had something to do with two different metals connected via a moist material.
The theory behind how cells work is now well established and only a basic knowledge of chemistry is needed to grasp the basic theory. Different metals have different reactivity, more reactive metals have a low ionization energy and loose electrons easily and they are able to donate these electrons to less reactive metals. This is the basis of the electro chemical series found in all chemistry data booklets. A salt soln or some other paste/gel material is needed to allow ions to move and therefore allow the transfer of electrons. The potential difference of a cell E°cell is calculated using the equation below where the electrode potential for the cathode (reduction) is subtracted from the electrode potential of the anode (oxidation). Clearly the larger the difference in electrode potential the greater the potential difference in a cell.
E°cell = E°cathode − E°anode
The free energy of the cell can be calculated from the nos of moles of electrons involved in the redox reaction (n), Faradays constant (F) and the standard cell potential E°cell
ΔG=−nFE
Lithium is ideal for batteries as it has an exceptionally high energy density due to being very electropositve and having a small mass. Lithium is far too reactive to use in its metallic form so instead it is used in its ionic form. The 2019 Nobel prize in chemistry was given for the development of the lithium battery, this was a serious technical challenge as Lithium is highly reactive and using it in its metallic form would and has caused very exothermic reactions in other words it causes fires and explosions, the lithium then is used in the form of ions intercalated in carbon making it much safer, thankfully laptops generally don’t go on fire as the lithium has been stabilized. The equations for a typical lithium battery are shown below. Batteries based on this chemistry power mobile phones, laptops and electric cars.
CoO2 + Li+ + e- → LiCoO2 Reduction half equation
LiC6 → C6 + Li+ + e Oxidation half equation
LiC6 + CoO2 ⇄ C6 + LiCoO2 Overall equation
This all sounds great no more burning of fossil fuels Greta Thunberg would no doubt approve. But....before Greta can celebrate lets look at some serious threats posed by lithium batteries.
Where does lithium come from and how is it obtained for use in lithium batteries? Lithium is extracted in two processes, around 80% comes from brine deposits(this is the process discussed below, the other process involves hard rock extraction and the use of HCl or H2SO4 to extract it), to extract the lithium salts, the brine is pumped from underground aquifers, and allowed to evaporate in large ponds. Aluminium chloride and sodium hydroxide is used in the precipitatipon process. The precipitate is filtered and dried. Already it can be seen that this is an energy intense process, resulting in a large carbon foot print. The impact on local water reserves and land is substantial. Environmentalists glue yourself to a lithium mine in Chile, Argentina or Bolivia please, a quick glance online will show the devastation of lithium extraction on land and water resources.
What about Cobalt unfortunately this is also causing tremendous environmental and human damage a quick online search of Congolese cobalt mining unfortunately shows this. Cobalt is toxic causing human suffering for the unfortunate miners, also rivers and land are toxified. The process of extracting cobalt (often times cobalt is found with copper and nickel) is energy intense and as has already been noted toxic. Worryingly there are large deposits of cobalt and other metals in certain deep-sea sites. Soon if cobalt continues to be mined in large quantities these deposits will probably become economical to mine. This would then devastate the deep sea environment.
Hydrocarbon fuels have been used extensively and this too as we are all so too well aware causes environmental issues. Electric cars/hydrocarbon cars which one is better for for the environment? No reasonable person disagrees that hydrocarbon fuels have an impact on the environment, which brings us on to global warming, most climate scientists will tell us the earth is warming (the extent of the warming and the mechanisms are not always clear). An attempt might be made to look at some of the chemistry and physics underlying global warming, I am more used to thermodynamics in a closed system so I might need to consult with an engineer to get a more rounded approach to the thermodynamics involved in global warming.
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