In what is our first guide to a major battery type, we look at Li-ion, particularly its leading chemistry of choice, lithium cobalt oxide—before considering the applications, and ultimately tackling the question: how do the battery type’s advantages and disadvantages fare overall?
A lithium-ion battery, which is revealed by someone detaching the back panel of an iPhone. Image courtesy of Wikimedia Commons.
Lithium-ion Batteries and What Makes Them So Popular
Li-ion is the most universally relied-upon battery today—so much so, that it has, in place of its competitors (including lead-acid and nickel-metal hydride), become the standard EV energy source of choice (discussed later).
Such popularity is also reflected of course by the fact that it’s the consumer’s choice for all manner of portable devices (consider its role in the smartphone revolution, to name just one example). And still, “we have only just started with Li-ion,” says Sven Bauer, CEO of Europe’s leading battery giant, BMZ, “and that’s why ... manufacturers have invested in huge R&D departments”.
Accordingly, the industry consensus is that its popularity and production is set to go on indefinitely, especially as Li-ion’s highly energy-dense chemistry renders it the best consumer rechargeable in terms of its power-to-weight ratio. This is largely because most consumer Li-ion batteries are LCO batteries, i.e. many Li-ion chemistries benefit from being lithium cobalt oxide-based, by way of having a cathode made of cobalt (a highly demanded metal, as covered later).
Accordingly, let’s now consider the general internal aspects of Li-ion, by focusing on its epitome (at least for consumer technology): the lithium cobalt oxide battery.
A diagram representing the internal makeup of a lithium-ion battery, particularly the movement of its lithium ions (from the cathode to the anode) during the charging process. Image courtesy of Bigstock.
The Internal Makeup of Lithium-ion Batteries
LCOs and other Li-ion batteries are formed of the 6 main components mentioned below, under which is also a mention of the typical materials that they’re made from:
Usually made of graphite carbon.
Again, made of cobalt, particularly in the case of LCOs (but non-LCO Li-ion battery cathodes can be made of lithium manganese, nickel, and so on).
Formed of non-aqueous lithium salt.
Made of polyolefin (due to its high chemical resistance, which is needed for anode/cathode separation).
A Positive Current Collector
Made of aluminium, due to the metal’s reduction*-friendly nature.
A Negative Current Collector
Made of copper, due to the metal’s oxidation-friendly nature.
*'Reduction' and 'oxidation' collectively form the 'redox' process, which enables electrons to be gained and lost respectively.
The Chemical Exchange
In LCOs and other Li-ion batteries, the role of each of the above components are as follows:
The anode and the cathode (collectively known as electrodes—respectively the negative and the positive electrode) are each there to store lithium ions (Li-ions), as well as release them: the anode releases Li-ions to the cathode when discharging, and the cathode releases Li-ions to the anode when charging.
To facilitate this exchange, the electrolyte is there to carry the positively-charged Li-ions, via the permeable, protective separator (there to mitigate the risk of a short circuit) from the anode to the cathode and vice versa (again, the order depends on whether the Li-ion battery is discharging or charging).
Mounted on the anode is the negative current collector (NCC), and mounted on the cathode is the positive current collector (PCC), and they are each positioned on the far, opposing sides of the Li-ion battery. The NCC receives the electrons (after they’ve exited the PCC during charging) from the external circuit; and the PCC receives electrons (after they’ve exited the NCC during discharging), from the external circuit.
Each component and its function ensures a relatively long-lasting (typically 2 to 3 years), reversible flow of electrons and Li-ions. But, aside from its rare but infamous risk of dendrite-related fire hazards, there remain other weaknesses that come with such an exchangeable chemistry.
All LCO batteries (in fact, Li-ion batteries in general) will inevitably succumb to capacity fade, namely the loss of a battery’s optimal charge, over time. Research is ongoing to mitigate capacity fade, but the fact that it’s naturally impossible for all the Li-ions to be perfectly shuttled, from anode to cathode and vice versa, is the smoking gun.
“Lithium oxide has a low electronic conductivity,” says Sooyeon Hwang, a staff scientist from the Electron Microscopy Group at the Center for Functional Nanomaterials. “Its accumulation creates a barrier [deemed an internal passivation layer] to the electrons that are shuttling back and forth between the battery's positive and negative electrode”.
And yet, most pressingly of all, LCO is confronted by the question of production. Consider whether the necessary LCO materials can even be safely and pragmatically obtained in the first place.
This leads us to lithium cobalt oxide batteries’ said, controversial (but highly sought after) metal: cobalt.
A close-up of pure cobalt chips. Image courtesy of Wikimedia Commons.
Cobalt Cathodes: The Strengths
As this journal extract from Chemical Society Reviews states: “Lithium cobalt oxide-based Li-ion batteries [have] led to the unprecedented success of consumer electronics”.
Indeed, Sony’s introduction in 1991 of the lithium-ion cobalt oxide chemistry, which is sometimes referred to by its formula name, LiCoO2, marked a breakthrough for portable devices.
This is chiefly due to:
Its high cycle life: 500 to 1,000 cycles (i.e. charge/discharge cycles); and
Its high energy density: 150 to 240 Wh/kg (watt-hour per kilogram).
Such a high energy, in fact, is even stronger than its manganese and phosphate-based Li-ion counterparts.
A graph that displays the watt-hour per kilogram (Wh/kg) measurements of 6 battery types. Cobalt lithium-ion leads at over 160 Wh/kg. Image courtesy of Battery University.
Cobalt: the Weaknesses
As touched on, the reliance of cobalt nevertheless comes at a price: the two main concerns of LCO batteries are in regards to potentially low safety levels and high pricing. Respectively:
Cobalt contributes to the potential flammability of Li-ion: if the latter overheats enough, the battery’s LCO cathode can break down, release its oxygen, and—combined with other flammable components in the electrolyte—spontaneously combust.
At the time of writing, Cobalt now costs over $14.29 per lb (for context, another popular battery metal, nickel, is roughly half the price at $7.41 per lb), and on top of that, it is also “subject to price volatility”, to quote Lithium-Ion Batteries: Advances & Applications, which “may dramatically change the price of the end product”.
Cobalt: Weighing up the Pros and Cons
Altogether, for LCOs, such issues in safety, usage, and production currently appear to be considered ‘necessary evils’, rather than deal breakers for cobalt, whose consumer interests continue to soar. “With demand from the battery sector expected to enjoy double-digit [percentage] growth over the coming decade,” says metal and chemical research group, Roskill, “the market is gearing itself up for ... unprecedented consumption”.
It’s with Li-ion’s popularity in mind that we now broaden our scope from LCOs to Li-ion batteries in general: namely, their leading applications.
Lithium-ion Battery Applications
Put simply, consumer devices and electric vehicles are 2 key areas for Li-ion batteries (which, typically, are respectively powered by a lithium cobalt oxide, and a lithium nickel manganese cobalt oxide chemistry).
A smartphone being held and in use. Image courtesy of Pexels.
As mentioned, alongside its good power-to-weight ratio, Li-ion batteries have a very strong cycle life, and the convenience that this grants the typical on-the-go consumer is unmistakable.
What’s more, a charge/discharge cycle does not start and end as soon as the user recharges their device; rather, the cycle is only complete once the battery has spent 100% of its charge, which is especially beneficial for the most ubiquitous consumer device of all: the smartphone. As smartphone giant Apple points out in its article, ‘Why Lithium-ion?’:
“[Y]ou might use 75% of your battery’s capacity one day, then recharge it fully overnight. If you use 25% the next day, ... the 2 days will add up to [just] 1 charge cycle. It could [therefore] take several days to complete a cycle.”
Accordingly, such a long-lasting and lightweight rechargeable chemistry makes Li-ion batteries the leading choice for portable consumer usage, even for the more cumbersome devices, such as laptops.
An electric vehicle (the Renault Zoe) being powered at a charging point. Image courtesy of Geograph.
As touched on above, the leading battery chemistry for EVs is the lithium nickel manganese cobalt (NMC). The power source is chosen due to the practical balance that comes with the high energy density of nickel, and the low internal resistance of manganese.
Other EV battery chemistries include such sources as lithium nickel cobalt aluminium oxide (Tesla’s energy source of choice in its Model S vehicles, due to its comparatively lower cobalt requirements).
While the specific EV battery chemistries vary from manufacturer to manufacturer, it's clear that it’s lithium-ion in general that has overshadowed its predecessors, nickel-metal hydride and lead-acid.
The reasons are, again, largely down to Li-ion’s power-to-weight ratio. But that is not to say that they are a definite replacement for traditional cars just yet, of course. According to UK financial data research firm, NimbleFins, the mean average range for EVs (even when you factor in the said, industry-leading Model S vehicles) is 196 miles, whereas petrol cars can run for hundreds more than this: for instance, Britain’s most popular petrol car (the Ford Fiesta) dwarfs this, as it can reach over 800 miles.
A graphic of 3 lithium-ion (Li-ion) batteries. Image courtesy of Bigstock.
So while Li-ion’s automotive applications are promising, the chemistry still has a long way to go to be as power-efficient as traditional transport. This is especially true when you consider that battery EVs can take 30 minutes at a minimum to charge, and potentially up to 12 hours—all depending on battery size, charger type, and so on.
That said, this is where lithium-ion R&D becomes all the more important: the technology is, after all, both universal and scalable. Projects are well underway to find workarounds for Li-ion EV limitations: AI-based battery state-of-health readings, improved electrolyte technology, and EV battery-swapping stations are all examples of why the chemistry is set only to improve with time.
Lithium-ion Batteries: Altogether a Powerful Industry
With lithium-ion batteries’ pros, cons, and industry applications considered, it’s clear why the battery chemistry is increasingly popular in—not just the said consumer electronics and EV industries—but renewables, medtech, and much more. While the chemistry may prove controversial, at least there are manufacturers, engineers, and all manner of R&D pioneers who are working to optimise its production.
After all, lithium-ion has long overtaken its rechargeable rivals in popularity, so enhancing (rather than replacing) the chemistry may well be the best course.