Using approximate computational methods, researchers at the SHARP Corporation and Kyoto Universities have identified a new battery material that can retain charge even after a massive amount of charge and discharge cycles. Experiments suggest that the new lithium ion battery that uses a co-substitute of lithium iron phosphate as the cathode can retain 70% of its charge even after 25,000 cycles. In comparison, a typical laptop battery can only retain 80% of its initial charge after 300 cycles.
The team chose lithium iron phosphate (LiFePO4) as the starting point in their quest to find a long-lasting battery material because it’s already well documented, readily available and cheap. Manufacturers report LiFePO4 batteries have cycle durability of 2000 cycles. They wanted to find a material close to LiFePO4, but with far larger durability.
This wasn’t an easy tasks since the researchers identified hundreds of potential candidate compounds. Testing each material would be mad – it would take an extremely long time and cost a lot of money. Instead, they approached the problem from an engineer’s perspective and opted to perform computer simulations. Namely, the scientists relied on a technique called Density Functional Theory (DFT), which is an approximate way to compute the quantum mechanical and general properties of a material that depend on its electron behavior. This way, they screened through 630 solute combinations in a short time.
Unfortunately, we’ve yet to find a way to compute the life cycle of a battery directly, but there are workarounds. For instance, the researchers assessed an approximate battery life by looking at the volume change of the material between the lithiated and delithiated states of the battery. Your typical laptop or smartphone battery has a volume change of about 6.5% . The larger the volume change, the greater the physical breakdown over time caused by microcracks inside the cathodes as a result of mechanical stress.
The resulting material from the computer analysis with the lowest volume change (3%, compared to 6.5% in a regular LiFePO4 battery) is a variant with silicon (Si4+) or aluminum (Al3+) substituted at the phosphorus (P) site and trivalent or tetravalent cations at the iron (Fe) site, and addition of zirconium (Zr) or yttrium (Y) that further enhance properties.
Finally, it was time to put the computations and simulations to the test. They synthesized their target material, made it into a lithium ion cathod and ran charge-discharge experiments. Findings show the battery can retain 80% charge at 10,000 cycles, and by extrapolation, 70% at 25,000 cycles, far above the target and current properties of LiFePO4 batteries.
For me, I find it really amazing just how much time and effort could be spared by working smart, instead of working hard. Often times, science isn’t about being precise and meticulous (though these shouldn’t be shone off), but about taking the most efficient route. It’s worth nothing that the result material will most likely be used for industrial applications, like huge energy stacks for solar cells or wind turbines, maybe even electric vehicle batteries, instead of telephones or notebooks.
Findings appeared in Nature Communications.
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