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Effects of cobalt from lithium ion batteries

Introduction

Electronics are the fastest growing trash group on the planet. It is estimated that 41.8 million metric tonnes (Mt) of electronic waste were produced in 2014 alone. That number is also estimated to rise to 50 million metric tonnes by 2018. Of the 41.8 million (Mt) of electronic waste in 2014, three million (MT) were small IT devices such as cell phones, pocket calculators, tablets, personal computers, etc. An additional 12.8 million (Mt) was comprised of items such as vacuum cleaners, electric shavers, and video cameras. Due to the increase in electronic waste being created there is also an increase in the amount batteries being thrown away. Americans alone dispose of over three billion batteries a year. At least 14,000 tons of those three billion batteries are rechargeable Many rechargeable devices, such as those listed above, utilize a Lithium-ion battery (LIB) as their source of power. The issue is that electronic devices are one of the only items disposed of even if they are not broken or defective. In the case of current technology, new is already old. Items that become obsolete are as susceptible to being thrown as ones that are broken. Because of this trend, more and more electronic devices, along with their batteries, are being thrown away improperly. The goal of this page is to increase the awareness of the potential environmental effects of cobalt from lithium ion batteries.

About the batteries

The purpose of the Cobalt (Co) within the LIBs is to act as a sort of bridge for the lithium ions to travel on between the cathode (positive end of the battery) and the anode (the negative end). During the charging of the battery, the cobalt is oxidized from Coᶾ⁺ to Co⁴⁺. This means that the transition metal, cobalt, has lost an electron. During the discharge of the battery the cobalt is reduced from Co⁴⁺ to Coᶾ⁺. Reduction is the opposite of oxidation. It is the gaining of an electron and decreases the overall oxidation state of the compound. Oxidation and reduction reactions are usually coupled together in a series of reactions known as red-ox (reduction-oxidation) reactions. This chemistry was utilized by Sony in 1990 to produce lithium ion cells. (See Lithium-ion battery)

Lithium ion battery

LiCoO₂ is the primary component of many LIBs, especially those of mobile devices. This compound offers a high energy density but can become a safety hazard if it is damaged. This is not the only type of LIB. Other types of LIBs include but are not limited to: LiFePO₄, LiMn₂O₄, LiNiCoAlO₂, and LiNiMnCoO₂ (NMC). As you can see, cobalt can be found within many types of lithium ion batteries and is necessary for sustaining the lifetime of those batteries.

The reason that LIBs are so often used is because of their high specific energy. The battery has a cobalt oxide cathode (positive end) and a graphite carbon anode (negative end). In the cathode during discharge, lithium ions move from the anode to the cathode. The flow reverses on charge. The greatest con of LIBs are their short life spans and also a low thermal stability. The low thermal stability is partly the reason why some phones or devices have ignited.

Chemistry with cobalt

The symbol for cobalt is Co. It has an atomic number of 27, an atomic mass of 58.933195 grams/mole. The melting point of Co is 1495 °C and the specific heat is 0.568 Joules/moles*kelvin. Cobalt is considered to be a fairly reactive element and is also one needed by many living things.

Cobalt is known to react with acids to produce hydrogen (H₂) gas. This gas is not a serious health concern though large concentrations of H₂ gas can cause an area to become oxygen deficient and this in turn can be dangerous for both humans and animals. Below is an example of cobalt reacting with sulfuric acid to produce the gas:

Co(s) + H₂SO₄(aq) → Co²⁺(aq) + SO₄^2-(aq) + H₂(g)

Water and cobalt are basically nonreactive at room temperature. However when cobalt is heated to the point where it is red hot it can be placed in water to react with the steam. The reaction of the hot cobalt and the steam is going to produce cobalt(II) oxide, CoO This cobalt oxide, when in a powder forms is very flammable. It is very common for LIBs which have been improperly disposed to end up in the back of a garbage truck. In the back of this truck it can become very hot and dry. In these conditions, the cobalt oxide can be ignited and can lead to serious fires as well as injuries.

2Co(s) + O₂(g) → 2CoO(s)

Overcharging a LIB can also lead to the production of cobalt oxide. This will be cobalt(IV) oxide, as proved by an x-ray diffraction experiment:

LiCoO₂ → Li⁺ + CoO₂ + e^-

Cobalt oxide is also capable of reacting with mineral acids to form corresponding cobalt salts:

CoO + 2 HX → CoX₂ + H₂O

As it can be seen from the above reactions, different forms of cobalt oxide are quite capable of reacting with many other compounds. The interaction with oxygen is of the most concern as this will lead to cobalt being present in air, water, and soil. Though as stated earlier that there is no real reactivity between water and cobalt at room temperature, it should be noted that cobalt in water forms a complex of six water molecules surrounding the cobalt ion. In chemical notation, this would appear as [Co(H₂O)₆]²⁺.

Health and environmental impact

Image of Cobalt

When the batteries are thrown away with regular trash as opposed to to being recycle, they will most likely end up being in a landfill. Eventually that battery will be incinerated and currently the incineration of cobalt within landfills is entirely legal. This incineration, each time more batteries containing cobalt are burned, will place cobalt particle as well as cobalt oxide particles into the air. Humans and animals both require small amounts of cobalt within their diet to live. Humans use cobalt in the form of cobalamin, also known as Vitamin B12. In a report issued by the ATSDR (Agency for Toxic Substances and Disease Registry) there is usually less than 2 nano-grams per cubic meter of cobalt in the air we breathe. The same report also stated that the average cobalt concentration of soil is anywhere between one to forty parts per million. Parts per million meaning milligrams of cobalt per every kilogram of soil. In drinking water, the concentration is found to be around one to two parts per billion or even less. Parts per billion means micro-grams per liter. These concentrations are not damaging to human and animal health but that can change when the cobalt concentration in the soil, water, or air increases.

Image of cobalamin

As previously stated, cobalt can be found within humans in the form of cobalamin. Cobalamin mainly contributes to the formation of red blood cells as well as bone marrow. Cobalt deficiency in humans can cause a number of side effects such as anemia, memory loss, dementia, and depression High accumulation of cobalt within humans is known to cause lung effects such as asthma and pneumonia. These are just some of the impacts of cobalt within humans. Metal compounds such as arsenic, cadmium, chromium, cobalt, lead, mercury, and nickel are classified as carcinogens affecting human health through occupational and environmental exposure. However, the underlying mechanisms involved in tumor formation are not well clarified. This simply means that cobalt has been labeled as a possible carcinogen but the means by which it causes cancer have not yet been identified. High concentrations of cobalt have a larger role in the environment rather than only on humans.

Plants, animals, and humans can all be affected by high cobalt concentrations in the environment. For plants, the uptake and distribution of cobalt is entirely species specific. In some species of plants, the over accumulation of cobalt can lead to an Iron deficiency (plant disorder). This in turn leads to poor growth of the plant as well as leaf loss which overall decreases the amount of oxygen produced by plants during photosynthesis. Eventually the deficiency would lead to plant death. One such example was seen in an experiment involving the effects of increased cobalt concentration on tomato plants. As the dosage of cobalt in the soil surrounding the plants increased, so too did the rate of necrosis of the leaves of the tomato plant. Overtime this led to an inability of the plant to produce fruit and eventually the plant died. One can imagine that if this happens on a large scale then crops of a specific region could be negatively affected. This could lead to famine as well as the deaths of animals which feed off certain crops.

Effects such as this are normally seen in areas where cobalt mining is very active, but it is also possible for a large volume of cobalt within a landfill to have the same effect. The cobalt enters the landfill in the form of the LIB. This LIB is then eventually incinerated or allowed to sit in the landfill to degrade very slowly over time. If it is incinerated then much of the cobalt is going to react with oxygen to form cobalt oxide particles. These particles can then travel using the air waves and will ultimately end up in soil or in a body of water being consumed by man, plants, and animals. When Co concentrations get too high (whether in air, water, or soil) the surrounding wildlife can suffer and die. In many grazing animals such as cows, high cobalt concentrations in their food supply can lead to lung tumors and overall death of the animal. Thus it can be understood that if cobalt concentrations are allowed to rise too high, through the accumulation of cobalt containing items such as LIBs or even cobalt mines, then the surrounding ecosystem is going to see negative effects. These negative effects would have consequences for all groups within that area which use or can be affected by cobalt.

Currently there are several facilities in North America which recycle batteries but the problem is that not everyone recycles and cobalt is one of the most expensive metals to have recycled. With the ever increasing human population and the equally increasing demand for new and improved handheld devices and gadgets, the production of these cobalt containing batteries is only going to increase. Greater strides need to be made towards recycling and reusing the materials in these batteries or else compounds such as cobalt could have negative future impacts on the environment.

References

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