Abstract
Transition metal oxides are very promising alternative anode materials for high-performance lithium-ion batteries (LIBs). However, their conversion reactions and concomitant volume expansion cause the pulverization, leading to poor cycling stability, which limit their applications. Here, we present the quasi-single-crystal NixCo3-xO4 hexagonal microtube (QNHM) composed of continuously twinned single crystal submicron-cubes as anode materials for LIBs with high energy density and long cycle life. At the current density of 0.8 A g−1, it can deliver a high discharge capacities of 1470 mAh g−1 over 100 cycles (105% of the 2nd cycle) and 590 mAh g−1 even after 1000 cycles. To better understand what underlying factors lead our QNHMs to achieve excellent electrochemical performance, a series of NixCo3-xO4 products with systematic shape evolution from spherical to polyhedral, and cubic particles as well as circular microtubes consisted of spheres and square microtubes composed of polyhedra have been synthesized. The excellent electrochemical performance of QNHMs is attributed to the unique stable quasi-single-crystal structure, which can both provide efficient electrical transport pathway and suppress the electrode pulverization. It is important to note that such quasi-single-crystal structure would be helpful to explore other high-energy lithium storage materials based on alloying or conversion reactions.
Highlights
Application targets of lithium-ion batteries (LIBs) are moving from portable electronic devices to their proposed use in high-power systems such as electric drive vehicles or renewable energy storage
The ratio of the intensity of the (400) peak to that of (111) peak increased from 0.12 for circular microtubes to 0.32 for square microtubes, and to 0.97 for quasi-single-crystal NixCo3-xO4 hexagonal microtube (QNHM), indicating the building blocks for microtubes were evolved from particles with mostly exposed (111) plane into cubes with exposed (400) plane with the increase of temperature from 180 °C to 230 °C
scanning electron microscopy (SEM) and X-ray diffraction (XRD) characterization further reveal that the QNHMs can stabilize the structure after enduring the severe convention reaction cycles
Summary
Application targets of lithium-ion batteries (LIBs) are moving from portable electronic devices to their proposed use in high-power systems such as electric drive vehicles or renewable energy storage. Considerable efforts are devoted to explore high-energy lithium storage materials based on alloying or conversion reactions such as Si2,3, Sn4, and transition metal oxides[5,6]. Great efforts have been devoted to growing active materials on the conductive current collector substrate with the aim of being free of the binders and carbon conductors as well as buffering the volume changes[26,27]. This type of electrode still demonstrated poor capacity retention and short cycle life. The problem of pulverization of NixCo3-xO4 electrode could be solved by using this stable quasi-single-crystal structure and without the aid of a carbonaceous matrix for the first time, and the obtained comprehensive performance is the best among NixCo3-xO4 materials to date
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