3D fusiform hierarchical micro/nano Li1.2Ni0.2Mn0.6O2 with preferred orientation (110) plane is successfully synthesized via a simple hydrothermal method, where the voltage fading is efficiently suppressed, and the rate performance is improved.
As a potential multi-electron electrode material for next generation lithium ion batteries, iron fluoride (FeF 3 ) and its analogues are attracting much more attentions. Their microstructures are the key to achieve good electrochemical performances. In this work, FeF 3 ·3H 2 O nano-flakes precursor with high crystallinity and flower-like morphology is synthesized successfully, by a liquid precipitation method using Fe(NO 3 ) 3 ·9H 2 O and NH 4 HF 2 as raw materials. The formation and the crystal growth mechanisms of the FeF 3 ·3H 2 O precursors are investigated and discussed. After different temperature heat-treatment and followed by ball-milling with Super P, the as-prepared FeF 3 ·0.33H 2 O/C and FeF 3 /C nanocomposites are used as cathode materials for lithium ion batteries. The FeF 3 ·0.33H 2 O/C nanocomposite exhibits a noticeable initial specific capacity of 187.1 mAh g -1 and reversible specific capacity of 172.3 mAh g -1 at 0.1C within a potential range of 2.0-4.5V. The capacity retention is as high as 97.33% after 50 cycles. Combined with HRTEM test, it confirms that the hydration water is not harmful but useful, namely, the tunnel phase formed with the hydration water is crucial to unobstructed Li + diffusion, and therefore leading to excellent electrochemical performances.
As a typical multielectron cathode material for lithium-ion batteries, iron fluoride (FeF) and its analogues suffer from poor electronic conductivity and low actual specific capacity. Herein, we introduce Ag nanoparticles by silver mirror reaction into the FeF·0.33HO cathode to build the electronic bridge between the solid (active materials) and liquid (electrolyte) interface. The crystal structures of as-prepared samples are characterized by X-ray diffraction and Rietveld refinement. Moreover, the density of states of FeF·0.33HO and FeF·0.33HO/Ag (Ag-decorated FeF·0.33HO) samples are calculated using the first principle density functional theory. The FeF·0.33HO/Ag cathodes exhibit significant enhancements on the electrochemical performance in terms of the cycle performance and rate capability, especially for the Ag-decorated amount of 5%. It achieves an initial capacity of 168.2 mA h g and retains a discharge capacity of 128.4 mA h g after 50 cycles in the voltage range of 2.0-4.5 V. It demonstrates that Ag decoration can reduce the band gap, improve electronic conductivity, and elevate intercalation/deintercalation kinetics.
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