Sodium-ion oxide cathodes made from transition metal core-shell particles \u2014 a nickel-rich core surrounded by a cobalt- and manganese-rich shell \u2014 were studied.<\/p>\n\n\n\n
“The manganese surface provides the particle with structural stability during cyclic charge-discharge,” the laboratory reports. “The nickel core provides high energy storage capacity.”<\/p>\n\n\n\n
The energy storage capacity gradually decreased during cyclic processes, when cracks began to form in the cathode particles due to deformation occurring between the shell and core in the particles.<\/p>\n\n\n\n
Further research showed that these cracks form deep inside the particles, rather than, as expected, on their surface. This also revealed a way to prevent crack formation.<\/p>\n\n\n\n
These two statements suggest the vast research efforts needed for this discovery, which, among other equipment, required the use of two of the world’s most powerful synchrotrons and a supercomputer ranked in the top 50 in the world: the Advanced Photon Source from Argonne, the National Synchrotron Light Source II from Brookhaven National Laboratory, and the Polaris supercomputer from Argonne.<\/p>\n\n\n\n
“Preventing crack formation during cathode synthesis yields significant dividends when the cathode is later charged and discharged,” said chemist Guo-Liang Xu from the Argonne laboratory.<\/p>\n\n\n\n
Deceptively simple, crack-resistant cathode particles that did not lose their capacity after 400 cycles were the result of modifying the heat treatment used to fabricate them.<\/p>\n\n\n\n
Core-shell cathode particles are made by heating hydroxide precursors at up to 600\u00b0C.<\/p>\n\n\n\n
When heated at 5\u00b0C\/min, cracks began to form at the core-shell boundary at only 250\u00b0C, but at an extremely slow heating rate \u2014 1\u00b0C\/min \u2014 the particles were stronger.<\/p>\n\n\n\n
“Prospects look very promising for future sodium-ion batteries, which will not only be cheaper and more durable, but also have energy density comparable to lithium iron phosphate cathodes currently used in many lithium-ion batteries. This will lead to electric vehicles with good range,” noted battery development team leader at Argonne, Khalil Amin.<\/p>\n\n\n\n
Future work in the laboratory will include attempts to reduce costs and enhance durability by removing nickel from the cathode.<\/p>\n","protected":false},"featured_media":4609,"template":"","acf":[],"yoast_head":"\n