electrode in Na-ion batteries is also advantageous to the cost reduction, while copper foil is necessary in Li-ion batteries. [30,31] Studies on room-temperature Na-ion batteries have started since 1970s and electrochemical properties of Na//Na x CoO 2 and Na//TiS 2 cells were reported in 1980 [32,33] when that of Li//LiCoO 2 was also first reported. [34] Then, Li-ion batteries was commercialized in 1991. In principle, Li-ion batteries consist of a Li-containing material such as LiCoO 2 as a positive electrode material and a Li-insertion material such as carbon as a negative one. On charge process, Li + ions move from the posi tive to negative electrode through electrolyte solution with simultaneous movement of electrons through an external circuit. A discharge process proceeds in the opposite direction. Li + ions and electrons come back to the positive electrode on the discharge. For ease in handling, Licontaining materials are utilized for the positive and non-Li ones for the negative electrode. Li-ion batteries have attracted much attention as high-voltage rechargeable batteries. On the other hand, Na-ion batteries essentially consist of the same technology with Li-ion batteries, except charge carriers. Na-containing materials are used for the positive and non-Na ones for the negative electrode. Na//Na x CoO 2 , however, shows working voltage ≈1 V lower than Li//LiCoO 2 , resulting in lower energy density. [35] As a result, Na-ion batteries have never been commercialized so far. [18] Indeed, Allied Corp. in USA, Showa Denko K. K., and Hitachi, Ltd. in Japan had collaborative work on Na-ion batteries and filed patents of Na-Pb alloy//γ-Na x CoO 2 cells [36][37][38][39] exhibiting good cycle stability but they had never commercialized the Na-ion batteries. The Na-Pb alloy//γ-Na x CoO 2 cells needed presodiation process for the Pb negative electrode. Therefore, primary drawback of Na-ion batteries was no candidates as practical negative electrode materials without Na predoping. Now, nongraphitizable carbon, so called hard carbon, is known to deliver large reversible capacity with good capacity retention. [40,41] Thus, secondary issue is low working potential of positive electrode materials. Open circuit potential of αand γ-Na x CoO 2 in Na cells is lower than that of α-NaFeO 2 type LiCoO 2 in the Li cell at the end of discharge. Indeed, standard redox potential of Na metal is lower than that of Li metal by ≈0.3 V. [42,43] The difference is, however, much smaller than that between Na x CoO 2 and LiCoO 2 at the end of discharge (ΔV ≈ 1.5 V), [14] which is probably due to larger ionic size and lower Lewis acidity of Na + in comparison to Li + as already discussed by Goodenough and Mizushima et al. in 1980. [35] Since our group demonstrated hard carbon//NaNi 1/2 Mn 1/2 O 2 full cells exhibiting acceptable cycle stability in 2009 [44] and Sodium 3d transition metal oxides for Na-ion batteries have attracted attention of battery researchers because of their new chemistries and abundant material resources in the eart...

Study aims This study aimed to investigate the clinical usefulness of magnifying endoscopy (ME) for non-ampullary duodenal tumors. Patients and methods We enrolled 103 consecutive patients with non-ampullary duodenal tumors that were observed by ME with narrow-band imaging (ME-NBI) and had pit pattern analysis before endoscopic resection at Hiroshima University Hospital before December 2014. ME-NBI images were classified as Type B or Type C according to the Hiroshima classification, and pit patterns were classified as regular or irregular. We studied the clinicopathological features and diagnoses with ME-NBI and pit pattern analyses according to the Vienna classification (category 3: 73 patients; category 4: 30 patients). Results Category 4 lesions were significantly larger than category 3 lesions. According to ME-NBI images, category 4 Type C lesions (83 %) were significantly more common than category 4 Type B lesions (17 %). According to pit pattern analyses, category 4 irregular lesions 4 (77 %) were significantly more common than category 4 regular lesions (23 %). The accuracies of using Type C ME-NBI images and irregular pit patterns to diagnose category 4 lesions were 87 % and 84 %, the sensitivities were 83 % and 77 %, and the specificities were 89 % and 88 %, respectively. There was no significant difference between ME-NBI and pit pattern analyses for diagnosing the histologic grade of non-ampullary duodenal tumors. Conclusion Our study showed that ME-NBI and pit pattern analysis had equivalent abilities to determine the histologic grade of non-ampullary duodenal tumors. ME-NBI may be more useful because it is a simple, less time-consuming procedure.

O3 type NaNi1/2Mn1/2O2 materials with Mg and Ti co-substitution demonstrate better capacity capability with an initial discharge capacity of 200 mA h g−1 in non-aqueous Na cells without any capacity loss due to substitution.

Although O3‐NaFe1/2Mn1/2O2 delivers a large capacity of over 150 mAh g−1 in an aprotic Na cell, its moist‐air stability and cycle stability are unsatisfactory for practical use. Slightly Na‐deficient O3‐Na5/6Fe1/2Mn1/2O2 (O3‐Na5/6FeMn) and O3‐Na5/6Fe1/3Mn1/2Me1/6O2 (Me = Mg or Cu, O3‐FeMnMe) are newly synthesized. The Cu and Mg doping provides higher moist‐air stability. O3‐Na5/6FeMn, O3‐FeMnCu, and O3‐FeMnMg deliver first discharge capacities of 193, 176, and 196 mAh g−1, respectively. Despite partial replacement of Fe with redox inactive Mg, oxide ions in O3‐FeMnMg participate in the redox reaction more apparently than O3‐Na5/6FeMn. X‐ray diffraction studies unveil the formation of a P‐O intergrowth phase during charging up to >4.0 V.

Na-ion batteries are emerging alternatives to Li-ion chemistries for large-scale energy storage applications. Quaternary layered oxide Na0.76Mn0.5Ni0.3Fe0.1Mg0.1O2 offers outstanding electrochemical performance in Na-ion batteries compared to pure-phase layered oxides because of the synergistic effect of the P/O-phase mixing. The material is indeed constituted by a mixture of P3, P2, and O3 phases, and a newly identified Na-free phase, i.e., nickel magnesium oxide phase, which improves heat removal and enhances the electrochemical performance. Herein, we structurally investigate, through synchrotron-radiation X-ray diffraction, the modifications occurring after full desodiation, detailing the material structural rearrangement upon Na removal and revealing the effect of two different charging protocols, i.e., constant current (CC) and constant current–constant voltage (CCCV). While the Na-free phase is electrochemically inactive, likely helping in homogenization of the thermal gradient in the electrode during cycling, O–P intergrown phases appear during the extraction of Na ions from interslab layers, and they are dependent on the desodiation level. The application of a constant voltage step at the end of the galvanostatic charge is responsible for a shortening of the interslab distance and a significant volume contraction (−11.9%).