Junchao Zheng,Zhuo Yang,Alvin Dai,Linbo Tang,Hanxin Wei,Yunjiao Li,Zhenjiang He,Jun Lu
Although the high energy density and environmental benignancy of LiNi 0.8 Co 0.15 Al 0.05 O 2 (NCA) holds promise for use as cathode material in Li-ion batteries, present low rate capabilities, and fast capacity fade limit its broad commercial applications. Here, it is reported that surface modification of NCA cathode ( R-3m ) with 5 nm-thick nanopillar layers and Fm-3m structures significantly improves electrode structure, morphology, and electrochemical performance. The formation of nanopillar layers increases cycling and working voltage stability of NCA by shielding the host material from hydrofluoric acid and improves structural stability with the electrolyte. The modified NCA cathode exhibits an enhanced 89% capacity retention at a rate of 1 C over that of pristine NCA (75.2%) after 150 cycles and effectively suppresses working voltage fade (a drop of 0.025 V after 300 cycles) during repeated charge–discharge cycles. In addition, the diffusion barrier of Li ions in NCA crystals at 0.80 V is noticeably smaller than that of Li ions in pristine NCA (0.87 eV). These findings demonstrate that this unique surface structure design considerably enhances cycle and rate performance of NCA, which has potential applications in other Ni-rich layered cathode materials.
This study focuses on suppressing the voltage decay and improving the electrochemical performance of Li-rich and manganese-based (LRM) material by Nb 2 O 5 coating, which is realized by an effective soft-chemical route using a mixture of ethanol and water as co-solvent. After Nb 2 O 5 coating, the resulted material demonstrates superior electrochemical performance as cathode material for LIBs. Particularly, it shows an excellent capacity retention of 98 % after 200 cycles at 1 C (1 C=250 mA g −1 ). Voltage decay within cycling is also obviously suppressed by Nb 2 O 5 coating. Moreover, it exhibits superior rate capacities, delivering 189 and 152 mAh g −1 at high current densities of 2 and 5 C, respectively. The improved electrochemical performance of Nb 2 O 5 coated sample can be attributed to that Nb 2 O 5 can suppress the phase transformation and voltage decay by acting as not only a fast ion conductor to accelerate the lithium ion diffusion at the cathode/electrolyte interface, but also an inert protective layer to reduce the direct contact between the cathode and electrolyte.
危险品化学品经营许可证（带存储）