ABSTRACT
As a potential anode material for lithium-ion batteries (LIBs), metal tin shows a high specific capacity. However, its inherent "volume effect" may easily turn tin-based electrode materials into powder and make them fall off in the cycle process, eventually leading to the reduction of the specific capacity, rate and cycle performance of the batteries. Considering the "volume effect" of tin, this study proposes to construct a carbon coating and three-dimensional graphene network to obtain a "double confinement" of metal tin, so as to improve the cycle and rate performance of the composite. This excellent construction can stabilize the tin and prevent its agglomeration during heat treatment and its pulverization during cycling, improving the electrochemical properties of tin-based composites. When the optimized composite material of C@Sn/NSGr-7.5 was used as an anode material in LIB, it maintained a specific capacity of about 667 mAh g-1 after 150 cycles at the current density of 0.1 A g-1 and exhibited a good cycle performance. It also displayed a good rate performance with a capability of 663 mAh g-1, 516 mAh g-1, 389 mAh g-1, 290 mAh g-1, 209 mAh g-1 and 141 mAh g-1 at 0.1 A g-1, 0.2 A g-1, 0.5 A g-1, 1 A g-1, 2 A g-1 and 5 A g-1, respectively. Furthermore, it delivered certain capacitance characteristics, which could improve the specific capacity of the battery. The above results showed that this is an effective method to obtain high-performance tin-based anode materials, which is of great significance for the development of new anode materials for LIBs.
ABSTRACT
Deep cerebral veins have been recently associated with the severity of hemodynamic impairment in moyamoya disease. The aim of the current study was to determine the correlation of deep medullary veins (DMVs) in susceptibility-weighted imaging (SWI) with ipsilateral cerebrovascular reactivity (CVR) of and anterior cecebrocervical artery stenosis in patients with ischemic stroke. Patients with unilateral TIA or infarction who underwent 3.0 T magnetic resonance imaging SWI, digital subtraction angiography and transcranial Doppler with CO2 stimulation within the first 7 days of hospitalization were retrospectively selected. CVR and stenosis of anterior cerebrocervical arteries were compared between different DMVs stages in symptomatic hemispheres (SHs) and asymptomatic hemispheres (AHs). A total of 61 patients were subsequently included in the present study. A univariate analysis was conducted and results for age (PAHs=0.004, PSHs=0.006), hypertension (PAHs=0.008, PSHs=0.020), current smoking (PAHs=0.006, PSHs=0.021), CVR (PAHs=0.000, PSHs=0.000), and artery stenosis (PAHs=0.000, PSHs=0.000) were obtained. The results suggested statistically significant differences between DMVs grades in SHs and AHs. A subsequent multivariate analysis revealed that CVR (ORAHs=0.925, 95% CIAHs: 0.873-0.981; ORSHs=0.945, 95% CISHs: 0.896-0.996), and artery stenosis (ORAH=3.147, 95% CIAH: 1.010-9.806; ORSHs=2.882, 95% CISHs: 1.017-8.166) were independent risk factors of DMVs. In conclusion, 3.0 T SWI was useful in detecting the DMVs around the lateral ventricle in patients with atherosclerotic ischemic stroke. CVR and stenosis of anterior cerebrocervical arteries were independent risk factors for ipsilateral DMVs in SHs and AHs.
