Fast Capacitive Energy Storage and Long Cycle Life in a Deintercalation-Intercalation Cathode Material.

Ni-rich Li-ion cathode materials promise high energy density, but are limited in power density and cycle life, resulting from their poor dynamic characteristics and quick degradation. On the other hand, capacitor electrode materials promise high power density and long cycle life but limited capacities. A joint energy storage mechanism of these two kinds is performed in the material-compositional level in this paper. A valence coupling between carbon π-electrons and O2- is identified in the as-prepared composite material, using a tracking X-ray photoelectron spectroscopy strategy. Besides delivering capacity simultaneously from its LiNi0.8 Co0.1 Mn0.1 O2 and capacitive carbon components with impressive amount and speed, this material shows robust cycling stability by preventing oxygen emission and phase transformation via the discovered valence coupling effect. Structural evolution of the composite shows a more flattened path compared to that of the pure LiNi0.8 Co0.1 Mn0.1 O2 , revealed by the in situ X-ray diffraction strategy. Without obvious phase transformation and losing active contents in this composite material, long cycling can be achieved.

Compound-Hierarchical-Sphere LiNi0.5Co0.2Mn0.3O2: Synthesis, Structure, and Electrochemical Characterization.

Compound-hierarchical-sphere-structured LiNi0.5Co0.2Mn0.3O2 was synthesized to improve the electrochemical performance of this material in lithium-ion battery cathodes. The product was found to have a large specific surface area, good electron and ion conductivities, a stable interface, and a robust nano/microhierarchical structure, all of which improved the rate capability, capacity, and cycling stability of this material. When this material was cycled between 3.0 and 4.3 V, a high discharge capacity of 180.8 mA h g-1 was obtained at 0.2C with 94.0% capacity retention after 100 cycles. In addition, a superior discharge capacity of 148.9 mA h g-1 was observed at a high current density of 1600 mA g-1. This compound-hierarchical-sphere LiNi0.5Co0.2Mn0.3O2 is readily prepared using our ternary coprecipitation method. We also propose an effector unit theory to explain the enhanced cycling stability of this substance and believe that the present results will assist in the design of cathode materials for lithium-ion batteries.

3D Reticular Li1.2Ni0.2Mn0.6O2 Cathode Material for Lithium-Ion Batteries.

In this study, a hard-templating route was developed to synthesize a 3D reticular Li1.2Ni0.2Mn0.6O2 cathode material using ordered mesoporous silica as the hard template. The synthesized 3D reticular Li1.2Ni0.2Mn0.6O2 microparticles consisted of two interlaced 3D nanonetworks and a mesopore channel system. When used as the cathode material in a lithium-ion battery, the as-synthesized 3D reticular Li1.2Ni0.2Mn0.6O2 exhibited remarkably enhanced electrochemical performance, namely, superior rate capability and better cycling stability than those of its bulk counterpart. Specifically, a high discharge capacity of 195.6 mA h g-1 at 1 C with 95.6% capacity retention after 50 cycles was achieved with the 3D reticular Li1.2Ni0.2Mn0.6O2. A high discharge capacity of 135.7 mA h g-1 even at a high current of 1000 mA g-1 was also obtained. This excellent electrochemical performance of the 3D reticular Li1.2Ni0.2Mn0.6O2 is attributed to its designed structure, which provided nanoscale lithium pathways, large specific surface area, good thermal and mechanical stability, and easy access to the material center.

Structural and Electrochemical Study of Hierarchical LiNi(1/3)Co(1/3)Mn(1/3)O2 Cathode Material for Lithium-Ion Batteries.

In this study, a facile nanoetching-template route is developed to synthesize porous nanomicrohierarchical LiNi1/3Co1/3Mn1/3O2 microspheres with diameters below 1.5 µm, using porous CoMnO3 binary oxide microspheres as the template. The unique morphology of CoMnO3 template originates from the contraction effect during the oxidative decomposition of Ca0.2Mn0.4Co0.4CO3 precursors and is further improved by selectively removing calcium carbonate with a nanoetching process after calcination. The as-synthesized LiNi1/3Co1/3Mn1/3O2 microsphere, composed of numerous primary particles and pores with size of dozens of nanometers, illustrates a well-assembled porous nanomicrohierarchical structure. When used as the cathode material for lithium-ion batteries, the as-synthesized microspheres exhibit remarkably enhanced electrochemical performances with higher capacity, excellent cycling stability, and better rate capability, compared with the bulk counterpart. Specifically, hierarchical LiNi1/3Co1/3Mn1/3O2 achieves a high discharge capacity of 159.6 mA h g(-1) at 0.2 C with 98.7% capacity retention after 75 cycles and 133.2 mA h g(-1) at 1 C with 90% capacity retention after 100 cycles. A high discharge capacity of 135.5 mA h g(-1) even at a high current of 750 mA g(-1) (5 C) is also achieved. The nanoetching-template method can provide a general approach to improve cycling stability and rate capability of high capacity cathode materials for lithium-ion batteries.