(Nanowerk Highlight) Lithium-ion batteries, with their excessive power density and lengthy lifetimes, have dominated the rechargeable battery marketplace for a long time. Nevertheless, lithium’s shortage and rising price have spurred an intense seek for different battery chemistries utilizing extra considerable supplies.
Sodium, proper under lithium on the periodic desk, has emerged as a number one contender. With chemical properties just like lithium however far larger availability, sodium might allow low-cost rechargeable batteries for large-scale power storage if researchers can overcome the technical challenges. Whereas the bigger dimension of sodium ions makes it more durable for them to squeeze out and in of electrodes, current breakthroughs in sodium ion conductors and high-capacity electrodes are steadily narrowing the efficiency hole with lithium-ion batteries.
Sodium superionic conductors (NASICONs) have proven specific promise as cathodes on account of their open crystal construction that enables fast sodium ion diffusion. NASICONs containing vanadium, which may give up a number of electrons per ion, can obtain capacities approaching these of lithium cathodes. Nevertheless, vanadium’s comparatively excessive price and toxicity have motivated efforts to partially change it with cheaper, extra benign parts like iron and manganese.
Now, a workforce led by Assistant Professor Edison H. Ang at Nanyang Technological College in Singapore has developed an revolutionary NASICON cathode that substitutes almost half the vanadium with iron whereas boosting efficiency. As reported within the journal Superior Science (“Pearl-Structure-Enhanced NASICON Cathode toward Ultrastable Sodium-Ion Batteries”), their Na3.05V1.03Fe0.97(PO4)3 (NVFP) cathode incorporates a conductive carbon framework that improves conductivity and structural stability, enabling ultra-stable biking at excessive charges.
The researchers synthesized NVFP with a sol-gel technique, utilizing citric acid to restrict particle progress and coat the particles with carbon. Crucially, they mechanically milled the fabric with spherical carbon nanoparticles known as Ketjen Black (KB), whose distinctive branching construction hyperlinks the NVFP particles collectively in a conductive community. “The KB branch chains encircle the NVFP like pearls on a necklace,” Ang explains to Nanowerk, “creating additional electron transport pathways that dramatically increase capacity and durability.”
Microscopy and spectroscopy confirmed this “pearl” nanostructure, with chains of KB nanoparticles adhering to the NVFP and boosting its digital conductivity by almost an order of magnitude. X-ray diffraction evaluation revealed NVFP’s sturdy crystal construction, with the iron and vanadium atoms randomly distributed in octahedral websites.
a,b) TEM and HRTEM pictures of p-NVFP (pearl-like KB department chains encircling the NVFP). c) Schematic diagram of p-NVFP. (Picture: reproduced from DOI:10.1002/advs.202301308, CC BY)
Electrochemical exams revealed the fabric’s distinctive sodium storage capabilities, reaching a powerful 106.8 mAh/g capability at a reasonable charge and retained over 75% of that capability at a really excessive 15C charge, far outperforming unmodified NVFP. The structured cathode additionally demonstrated outstanding stability, retaining 87.7% capability after 5000 cycles at a 5C charge.
“By buffering the impact of high current densities, the pearl nanostructure allows ultra-stable cycling with minimal degradation,” says Ang.
In-situ X-ray diffraction throughout biking supplied insights into the cathode’s cost storage mechanism and structural evolution. In contrast to typical NASICON supplies, NVFP exhibited an uncommon lower in lattice parameter throughout preliminary charging, which the authors attribute to partial oxidation of iron facilitated by the floor interactions with the carbon community. This modulation seems to advertise sodium extraction and enhance biking stability, with a quantity change of simply 3% – among the many lowest reported for NASICON electrodes.
Measurements of sodium diffusion kinetics throughout biking revealed the NVFP’s impressively excessive ionic conductivity, significantly by way of the voltage plateaus similar to the iron and vanadium redox reactions. The interconnected nanostructure and optimized crystal framework synergistically improve sodium transport all through cost and discharge.
To reveal sensible applicability, the workforce paired the NVFP cathode with a low-cost laborious carbon anode in a full sodium ion cell. The complete cell delivered a excessive 102.5 mAh/g preliminary capability and retained 83% of that after 500 cycles at 2C, putting it among the many top-performing sodium ion batteries reported up to now.
Although challenges stay in matching the power density of lithium-ion cells, this nanostructured NASICON represents a major step towards realizing high-performance sodium ion batteries. By combining the multi-electron capability of vanadium with the abundance of iron in a rationally designed nanostructure, the NTU workforce has achieved a cathode that displays each excessive power and ultra-stable long-term biking.
“With further optimization, our strategy of coupling mixed-metal NASICONs with conductive nanocarbon scaffolds could enable sodium ion batteries that compete with lithium cells on performance while using cheaper, more sustainable materials,” Ang concludes. “Such a breakthrough would accelerate the deployment of large-scale rechargeable batteries for electric vehicles and renewable energy storage, helping to power the transition to a clean energy future.”
Get our Nanotechnology Highlight updates to your inbox!
Thanks!
You’ve got efficiently joined our subscriber record.
Turn into a Highlight visitor writer! Be a part of our giant and rising group of visitor contributors. Have you ever simply printed a scientific paper or produce other thrilling developments to share with the nanotechnology group? Right here is the way to publish on nanowerk.com.
