At the heart of most electronics, today are rechargeable lithium-ion batteries (LIBs). But their energy storage capacities are not enough for large-scale energy storage systems (ESSs). Lithium-sulfur batteries (LSBs) could be useful in such a scenario due to their higher theoretical energy storage capacity. They could even replace LIBs in other applications like drones, given their lightweight and lower cost.
But the same mechanism that is giving them all this power is keeping them becoming a widespread practical reality. Unlike LIBs, the reaction pathway in LSBs leads to an accumulation of solid lithium sulfide (Li2S6) and liquid lithium polysulfide (LiPS), causing a loss of active material from the sulfur cathode (positively charged electrode) and corrosion of the lithium anode (negatively charged electrode). To improve battery life, scientists have been looking for catalysts that can make this degradation efficiently reversible during use.
In a new study published in ChemSusChem, scientists from Gwangju Institute of Technology (GIST), Korea, report their breakthrough in this endeavor. “While looking for a new electrocatalyst for the LSBs, we recalled a previous study we had performed with cobalt oxalate (CoC2O4) in which we had found that negatively charged ions can easily adsorb on this material’s surface during electrolysis. This motivated us to hypothesize that CoC2O4 would exhibit similar behavior with sulfur in LSBs as well,” explains Prof. Jaeyoung Lee from GIST, who led the study.
To test their hypothesis, the scientists constructed an LSB by adding a layer of CoC2O4 on the sulfur cathode.
Sure enough, observations and analyses revealed that CoC2O4‘s ability to adsorb sulfur allowed the reduction and dissociation of Li2S6 and LiPS. Further, it suppressed the diffusion of LiPS into the electrolyte by adsorbing LiPS on its surface, preventing it from reaching the lithium anode and triggering a self-discharge reaction. These actions together improved sulfur utilization and reduced anode degradation, thereby enhancing the longevity, performance, and energy storage capacity of the battery.
Charged by these findings, Prof. Lee envisions an electronic future governed by LSBs, which LIBs cannot realize. “LSBs can enable efficient electric transportation such as in unmanned aircrafts, electric buses, trucks and locomotives, in addition to large-scale energy storage devices,” he observes. “We hope that our findings can get LSBs one step closer to commercialization for these purposes.”
Perhaps, it’s only a matter of time before lithium-sulfur batteries power the world.
]]>With these differences in chemistry come differences in performance and cost. While both lithium-ion and lead-acid battery options can be effective storage solutions, here’s how they stack up when compared head to head in key categories:
| LITHIUM-ION | LEAD ACID | |
| Cost | X | |
| Capacity | X | |
| Depth of discharge | X | |
| Efficiency | X | |
| Lifespan | X |
In most cases, lithium-ion battery technology is superior to lead-acid due to its reliability and efficiency, among other attributes. However, in cases of small off-grid storage systems that aren’t used regularly, less expensive lead-acid battery options can be preferable.
Lithium-ion and lead-acid batteries can both store energy effectively, but each has unique advantages and drawbacks. Here are some important comparison points to consider when deciding on a battery type:
The one category in which lead-acid batteries seemingly outperform lithium-ion options is in their cost. A lead-acid battery system may cost hundreds or thousands of dollars less than a similarly-sized lithium-ion setup – lithium-ion batteries currently cost anywhere from $5,000 to $15,000 including installation, and this range can go higher or lower depending on the size of system you need.
While lead-acid batteries typically have lower purchase and installation costs compared to lithium-ion options, the lifetime value of a lithium-ion battery evens the scales. Below, we’ll outline other important features of each battery type to consider, and explain why these factors contribute to an overall higher value for lithium-ion battery systems.
A battery’s capacity is a measure of how much energy can be stored (and eventually discharged) by the battery. While capacity numbers vary between battery models and manufacturers, lithium-ion battery technology has been well-proven to have a significantly higher energy density than lead-acid batteries. This means that more energy can be stored in a lithium-ion battery using the same physical space. Because you can store more energy with lithium-ion technology, you can discharge more energy, thus power more appliances for longer periods of time.
A battery’s depth of discharge is the percentage of the battery that can be safely drained of energy without damaging the battery. While it is normal to use 85 percent or more of a lithium-ion battery’s total capacity in a single cycle, lead-acid batteries should not be discharged past roughly 50 percent, as doing so negatively impacts the lifetime of the battery. The superior depth of discharge possible with lithium-ion technology means that lithium-ion batteries have an even higher effective capacity than lead-acid options, especially considering the higher energy density in lithium-ion technology mentioned above.
Just like solar panel efficiency, battery efficiency is an important metric to consider when comparing different options. Most lithium-ion batteries are 95 percent efficient or more, meaning that 95 percent or more of the energy stored in a lithium-ion battery is actually able to be used. Conversely, lead-acid batteries see efficiencies closer to 80 to 85 percent. Higher efficiency batteries charge faster, and similarly to the depth of discharge, improved efficiency means a higher effective battery capacity.
Batteries are also similar to solar panels in that they degrade over time and become less effective as they age. Discharging a battery to power your home or appliances and then recharging it with solar energy or the grid counts as one “cycle”. The numbers vary from study to study, but lithium-ion batteries generally last for several times the number of cycles as lead-acid batteries, leading to a longer effective lifespan for lithium-ion products.
If you need a battery backup system, both lead-acid and lithium-ion batteries can be effective options. However, it’s usually the right decision to install a lithium-ion battery given the many advantages of the technology – longer lifetime, higher efficiencies, and higher energy density. Despite having higher upfront costs, lithium-ion batteries are usually more valuable than lead-acid options.
One case where lead-acid batteries may be the better decision is in a scenario with an off-grid solar installation that isn’t used very frequently. For example, keeping a lead-acid battery on a boat or RV as a backup power source that is only used every month or so is a less expensive option than lithium-ion, and due to the lower usage rate, you’ll avoid many of the drawbacks of lead-acid technology, such as their shorter lifespan.
With any large purchase like solar and batteries (paired or separately), you want to consider your options. You can sign up on the EnergySage Marketplace to receive turnkey quotes for solar installation from pre-screened local solar installers. If battery storage is something you’re interested in pairing with your system, we recommend adding a note in your account preferences specifying you’re interested in pricing and information about batteries. Even if a solar installer doesn’t install batteries themselves, they can design a solar panel system so that you can
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