Sifu Bi

Synthesis and electrochemical performance of Sn-doped LiNi0.5Mn1.5O4 cathode material for high-voltage lithium-ion batteries

LiNi0.5Mn1.5−xSnxO4 (0 ≤ x ≤ 0.1) cathode materials with uniform and fine particle sizes were successfully synthesized by a two-step calcination of solid-state reaction method. As the cathode materials for lithium ion batteries, the LiNi0.5Mn1.48Sn0.02O4 shows the highest specific capacity and cycle stability. In the potential range of 3.5–4.9 V at room temperature, LiNi0.5Mn1.48Sn0.02O4 composite material shows a discharge capacity of more than 117 mA h g−1 at 0.1 C, while the corresponding discharge capacity of undoped LiNi0.5Mn1.5O4 is only 101 mA h g−1. Moreover, in cycle performance, all the LiNi0.5Mn1.5−xSnxO4 (0 ≤ x ≤ 0.1) samples show better capacity retention than the undoped LiNi0.5Mn1.5O4 at 1 C rate after 100 cycles. Especially, for the LiNi0.5Mn1.5O4, the discharge capacity after 100 cycles is 90 mA h g−1, while the corresponding discharge capacities of the undoped LiNi0.5Mn1.5O4 is only 56.1 mA h g−1. The significantly enhanced DLi+ and the enlarged electronic conductivity make the Sn-doped spinel LiNi0.5Mn1.5O4 material present even more excellent electrochemical performances. These results reveal that Sn-doping is an effective way to improve electrochemical performances of LiNi0.5Mn1.5O4.摘要本文采用两步烧结高温固相法成功制备了锡掺杂LiNi0.5Mn1.5−xSnxO4 (0 ≤ x ≤ 0.1)锂离子电池正极材料. x为0.02时, LiNi0.5Mn1.48Sn0.02O4的比容量和循环性能最好. 室温下, 在3.5–4.9 V电压范围内, 0.1 C放电倍率, LiNi0.5Mn1.48Sn0.02O4的首次放电比容量为117 mA h g−1, 而没有锡掺杂的LiNi0.5Mn1.5O4只有101 mA h g−1. 此外, 1 C放电100个循环后, 所有锡掺杂后的LiNi0.5Mn1.5O4材料均保持了较高的放电比容量; 尤其是LiNi0.5Mn1.48Sn0.02O4, 100个循环后, 放电比容量为90 mA h g−1, 而纯的LiNi0.5Mn1.5O4, 100个循环后其放电比容量仅为56.1 mA h g−1. 锡掺杂后的LiNi0.5Mn1.48Sn0.02O4材料具有比LiNi0.5Mn1.5O4材料及其他组材料更高的锂离子扩散效率, Sn离子的掺杂有利于锂离子的扩散和导电性的提高, 从而提高了LiNi0.5Mn1.5O4的电化学性能. 因此锡掺杂是一种有效的改善高电压锂离子电池材料LiNi0.5Mn1.5O4电化学性能的方法.

Effects of organic additives on the immersion gold depositing from a sulfite–thiosulfate solution in an electroless nickel immersion gold process

An immersion gold-plating process on electroless Ni–P alloy substrate was investigated. The immersion Au coating was deposited from a thiosulfate–sulfite mixed ligand bath based on Ni–P alloy substrate. The effects of three organic additives, such as polyethylenimine (PEI), hexamethylene tetramine (HET) and benzotriazole (BTA) on the depositing process and the performance of Au coating were investigated. The study was performed by measuring the open circuit potential–time curves in situ and Tafel tests in combination with X-ray fluorescence spectrometry (XRF), scanning electron microscope (SEM), Raman spectroscopy and X-ray diffraction (XRD) analysis techniques. The results show that PEI, HET and BTA could adsorb and desorb on the surface of Au coating and they had the similar influences on the open circuit potential. With these organic compounds adding, the plateau potential shifts to the positive direction, and the time for the potential to reach the plateau value decreases with increasing additive concentration. The XRF, XRD and SEM studies indicated that these three additives decreased the initial deposition rate, decreased the size of Au particles, and thus changed the morphology of Au deposits. Tafel studies demonstrated that the corrosion resistance of Au coating could be improved by adding PEI, HET or BTA to immersion gold bath. A cause for understanding these additives was indicated based on the above experiments.