![]() Through an extensive study of the structural changes by in-depth in situ and ex situ X-ray diffraction (XRD) characterization during Na + intercalation/deintercalation, Sn is proven to be effective in stabilizing the layered structure by suppressing the irreversible phase transformation under the high-voltage region (∼4.1 V vs Na/Na +). In this work, the incorporation of Sn into a NaNi 1/3Fe 1/3Mn 1/3O 2 cathode has been studied to simultaneously stabilize the crystal structure as well as the particle surface at high cell voltages. However, the much higher atomic weight of Na (Na 23 g/mol vs Li 6.9 g/mol) and higher standard electrochemical potential make it difficult for NIBs to surpass LIBs in terms of energy density. (16−18) Therefore, sodium-ion batteries (NIBs) offer a reasonable low-cost sustainable alternative to current lithium-ion batteries. (4,5) In addition, alternative transition metals, such as Mn, (6,7) Fe, (8,9) Cu, (10,11) Ti, (12) Cr, (13) V, (14,15) can be utilized, instead of cobalt for the cathode, along with the reported safety benefits. (1−3) Sodium-ion batteries offer one such solution, as sodium is geographically widespread and can be harvested through seawater and from rock salt and is significantly more abundant than lithium (Na: 23 000 ppm vs Li: 17 ppm in the Earth’s crust). However, the relatively low reserves and uneven distribution of widely used strategic metals and critical materials in LIBs such as lithium, nickel, cobalt, and graphite have forced researchers to search for alternatives. With the widespread increase in the numbers of batteries needed for consumer electronics, electric vehicles, and energy storage industries, lithium-ion batteries are experiencing an unprecedented period of rapid development. ![]() ![]() This work offers a facile process to simultaneously stabilize the bulk structure and interface for the O3-type layered cathodes for sodium-ion batteries and raises the possibility of similar effective strategies to be employed for other energy storage materials. An 8%-Sn-modified NaNi 1/3Fe 1/3Mn 1/3O 2 cathode exhibits a doubling in capacity retention increase after 150 cycles in the wide voltage range of 2.0–4.1 V vs Na/Na + compared to none, and 81% capacity retention is observed after 200 cycles in a full cell vs hard carbon. A series of Sn-modified materials are reported. In the meantime, the nanolayer Sn/Na/O composite on the surface effectively inhibits surface parasitic reactions and improves the interfacial stability during cycling. ![]() The bulk substitution of Sn 4+ stabilizes the crystal structure by alleviating the irreversible phase transition and lattice structure degradation and increases the observed average voltage. A novel Sn-modified O3-type layered NaNi 1/3Fe 1/3Mn 1/3O 2 cathode is presented, with improved high-voltage stability through simultaneous bulk Sn doping and surface coating in a scalable one-step process. However, rapid capacity fading caused by serious structural changes and interfacial degradation hampers their use. O3-type layered oxide materials are considered to be a highly suitable cathode for sodium-ion batteries (NIBs) due to their appreciable specific capacity and energy density.
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