No abstract

The fire incidents triggered by the thermal runaway of Li-ion batteries (LIBs) have aroused widespread concerns, as the instabilities of the delithiated cathode materials are generally accepted as one of the reasons for the ignition of LIBs. Herein, the electrochemical performance and the thermal stability of single-crystal and polycrystalline LiNi 0.6 Co 0.2 Mn 0.2 O 2 electrode were investigated, trying to explore a novel, advanced approach for the thermal and cyclic stability of LiNi 0.6 Co 0.2 Mn 0.2 O 2 . Our results showed that the collapses of the layer structures and the cracks of polycrystalline particles occurred during charge; compared with the polycrystalline materials, the single-crystal particles efficiently improved the thermal stability, cyclic performance, and collapse of the layer structures. Additionally, the single-crystal material could maintain the structure and morphology even under a high charging voltage of 4.95 V. After 800 cycles at 45 • C, 92.5% of the initial capacity was maintained for the single-crystal LiNi 0.6 Co 0.2 Mn 0.2 O 2 , while the capacity retention of the polycrystalline materials was below 90.5% after 300 cycles.

A thick and dense flakelike LiCoO2 with exposed {010} active facets is synthesized using Co(OH)2 nanoflake as a self-sacrificial template obtained from a simple coprecipitation method, and served as a cathode material for lithium ion batteries. When operated at a high cutoff voltage up to 4.5 V, the resultant LiCoO2 exhibits an outstanding rate capability, delivering a reversible discharge capacity as high as 179, 176, 168, 116, and 96 mA h g(-1) at 25 °C under the current rate of 0.1, 0.5, 1, 5, and 10 C, respectively. When charge/discharge cycling at 55 °C, a high specific capacity of 148 mA h g(-1) (∼88% retention) can be retained after 100 cycles under 1 C, demonstrating excellent cycling and thermal stability. Besides, the flakelike LiCoO2 also shows an impressive low-temperature electrochemical activity with specific capacities of 175 (0.1 C) and 154 mA h g(-1) (1 C) at -10 °C, being the highest ever reported for a subzero-temperature lithium storage capability, as well as 52% capacity retention even after 80 cycles under 1 C. Such superior high-voltage electrochemical performances of the flakelike LiCoO2 operated at a wide temperature range are mainly attributed to its unique hierarchical structure with specifically exposed facets. The exposed {010} active facets provide a preferential crystallographic orientation for Li-ion migration, while the micrometer-sized secondary particles agglomerated by submicron primary LiCoO2 flakes endow the electrode with better structural integrity, both of which ensure the LiCoO2 cathode to manifest remarkably enhanced reversible lithium storage properties.

A dual-emitting MOF-based sensor 1⊃HPTS was prepared through encapsulating the dye HPTS via an ion-exchange approach. 1⊃HPTS exhibits a broad response to nitro compounds including nitroaromatic explosives, aliphatic nitro-explosives and nitro-containing antibiotics.