Let's Look at Lithium-ion

Lithium-ion batteries have revolutionised our lives, with the average home now full of rechargeable devices harbouring the technology. The importance of this was recognised in 2019 when John Goodenough, M Stanley Whittingham and Akira Yoshino were awarded the Nobel Prize in Chemistry for their work in the early development of lithium-ion energy storage devices.

One reason for the hype is that lithium-ion technology could help reduce emissions and clean up our cities. The WHO estimates that road transport accounts for around 17% of global CO2 emissions. A world in which fossil fuel-powered vehicles are replaced by rechargeable alternatives is appealing to anyone interested in reducing the devastating impact of climate change, or improving local pollution levels in our cities.

An important area of development is providing batteries with high capacity and high voltage, a combination which results in the delivery of more energy. The capacity of the cathode is the limiting factor for lithium-ion batteries. Cathode material development has therefore been a crucial area of research.

Lithium cobalt oxide (LCO), discovered by Goodenough in the early 1980s, has been the most commercially successful cathode material, still being found in many lithium-ion batteries used today. It has the advantage of providing a large specific capacity of 274 milliamp hours per gram of material (mAh/g). Despite this, LCO suffers from reduced capacity at high discharge rates, which is a major concern when developing batteries for EVs. Small electronic devices operate on a trickle of current from the battery – a low discharge rate. But the capacity of a battery will often be lower when a battery is discharged more quickly. A heavy EV needs a lot of power over a small space of time when accelerating, so another area of development has concentrated on finding alternatives to LCO, which maintain high capacity even at higher discharge rates. On top of this, the high cost of elemental cobalt renders LCO too expensive for widespread commercial use.

Based on the low cost and low environmental impact of manganese relative to cobalt, compounds such as lithium manganese oxide (LMO) have been investigated as potential cathode materials, but a major stumbling block for such manganese-containing materials is capacity fade. Lithium-ion batteries lose some capacity with every charge. For a mobile phone this isn’t a huge problem, but for an EV this means range would reduce for the vehicle over time.

LCO and LMO fall within the broader category of transition metal oxide materials and there has been much research into other materials within this category. However, other types of cathode materials are now also growing in popularity. For example, lithium iron phosphate (LFP), which is a so-called “polyanion” material, is being quickly adopted by several EV manufacturers, due to the thermal stability, high power and fast charging that it offers. LFP is a cobalt-free material that also has relatively low toxicity and cost.

As of September 2022, the market share of LFP batteries had risen to 31%, and this is expected to continue to grow. For instance, Ford is planning to build a new $3.5bn factory in Michigan, USA for the production of these batteries. Ford will use technology developed by Chinese firm CATL, who also supply batteries to a range of other EV makers, such as Tesla, BMW and Volkswagen.

Electrical energy storage is so essential to such a huge range of devices that any significant developments in the basic technologies available will resonate throughout our daily lives.  

It is generally considered that, at least in the short term, energy storage advances will come from incremental development of traditional lithium ion type batteries. Nevertheless, we find ourselves at a juncture, facing the need for both improved recycling of lithium ion batteries and the commercial realisation of different forms of battery and other energy storage solutions.

Major growth in the uptake of battery use brings with it the challenge of a sharp rise in battery waste.  Lithium-ion batteries, which are currently used as the power storage unit in hybrid and EVs, tend to contain toxic and rare transition metals in their cathode material, such as cobalt, nickel and manganese. Lithium itself is found in relatively few countries and the global supply is not thought to be sufficient to replace all conventional vehicles with EVs using today's battery technology. Owing to their lower toxicity as compared with lead-acid or nickel-cadmium batteries, where up to 99% of toxic material is reclaimed, there is not an established recycling industry for lithium ion batteries.  However, the sheer volume of disused lithium ion batteries and the increasing shortage of materials required to manufacture them means that effective re-use strategies for lithium ion batteries and/or alternative high energy density power storage solutions will need to be developed to mitigate against potential future global and environmental crises.

The need for new battery technologies to satisfy industry and many other areas is clear. Additionally, public interest in climate change and environmental damage is likely to drive consumer demand for innovative products in these areas, providing a healthy incentive for investment in energy storage research and development.

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