Simultaneously promoting the surface/bulk structural stability of Fe/Mn-based layered cathode for sodium ion batteries.

Layered sodium iron manganese oxide cathodes have attracted great interest owing to their high specific capacity and cost-effective metal resources, while the detrimental phase transitions and surface structural degradation severely limit their commercial applications. In this work, the bulk and surface structure stability of a P2-Na0.67Fe0.5Mn0.5O2 cathode can be synergically enhanced by a one-step Li/Nb co-doping strategy. Structural characterizations reveal that Li doping promotes the formation of P2/O3 biphasic structure and makes the unfavorable P2-OP4 phase transition convert into a smooth solid-solution reaction. Nb doping enhances the mobility of sodium ions and forms strong Nb-O bonds, thereby enhancing the stability of the TMO2 layer structure. In particular, the Nb element induces the surface reorganization of an atomic-scale NaNbO3 coating layer, which could effectively prevent the dissolution of metals and surface side reactions. The synergistic mechanism of enhanced electrochemical performance is proved by multiple characterizations during cycling. As a result, the as-prepared Na0.67Li0.1Fe0.5Mn0.38Nb0.02O2 exhibits improved capacity retention of 85.4 % than raw material (45.7 %) after 100 cycles at 0.5C (1C = 174 mA g-1) within 2.0-4.0 V. This co-regulating strategy provides a promising approach to designing highly stable sodium-ion battery cathodes. Furthermore, a full cell of Na0.67Li0.1Fe0.5Mn0.38Nb0.02O2 with hard carbon displays excellent cycling stability (85.1 % capacity retention after 100 cycles), making its commercial operation possible. This synergistic strategy of biphasic structure and surface reorganization is a critical route to accelerate the application of layer oxide cathodes.

The investigation of the physiochemical factors and bacterial communities indicates a low-toxic infectious risk of the Qiujiang River in Shanghai, China.

The overall water quality of urban rivers is closely related to the community structure and the physiochemical factors in them. In this study, the bacterial communities and physiochemical factors of the Qiujiang River, an important urban river in Shanghai, were explored. Water samples were collected from nine sites of the Qiujiang River on November 16, 2020. The water quality and bacterial diversity were studied through physicochemical detection, microbial culture and identification, luminescence bacteria method, and 16S rRNA Illumina MiSeq high-throughput sequencing technology. The water pollution of the Qiujiang River was quite serious with three water quality evaluation indexes, including Cd2+, Pb2+, and NH4+-N, exceeding the Class V standard set by the Environmental Quality Standards for Surface Water (China, GB3838-2002), while the luminescent bacteria test indicated low toxicity of nine sampling sites. Through 16S rRNA sequencing, a total of 45 phyla, 124 classes, and 963 genera were identified, in which Proteobacteria, Gammaproteobacteria, and Limnohabitans were the most abundant phylum, class, and genus, respectively. The Spearman correlation heatmap and redundancy analysis showed that the bacterial communities in the Qiujiang River were correlated with pH; the concentrations of K+, and NH4+-N, and the Limnohabitans were significantly correlated with the concentrations of K+, and NH4+-N in the Zhongyuan Road bridge segment. In addition, opportunistic pathogens Enterobacter cloacae complex and Klebsiella pneumoniae in the samples collected in the Zhongyuan Road bridge segment and Huangpu River segment, respectively, were successfully cultured. The Qiujiang River was a heavily polluted urban river. The bacterial community structure and diversity were greatly affected by the physiochemical factors of the Qiujiang River, and it displayed low toxicity while a relatively high infectious risk of intestinal and lung infectious diseases.

NiSb/nitrogen-doped carbon derived from Ni-based framework as advanced anode for lithium-ion batteries.

Antimony anode has attracted much attention owing to its low lithium-embedded platform and high specific capacity. However, the dramatic volume expansion during the insertion and detachment of Li+ seriously affects its application in lithium-ion batteries. In this work, NiSb alloy embedded in nitrogen-doped carbon (NiSb/C) derived from a Ni-based framework was synthesized by a simple hydrothermal reaction followed by annealing treatment. NiSb alloy nanoparticles could alleviate significant volume expansion during lithium/delithiation owing to the good buffering action of Ni. Nitrogen-doped carbon provides abundant active sites for Li+ and serves as a conductive network to accelerate electron transport. Moreover, the uniformly dispersed NiSb alloy particles and the nitrogen-doped carbon can effectively cooperate to retain the structural completeness of antimony, which promotes the cycling stability and high-rate performance of the NiSb/C anode. At a high density of 2 A g-1, the prepared NiSb/C anode exhibits a reversible specific capacity of 426 mAh g-1 after 450 cycles. It can also exhibit a superior rate capability of 387 mAh g-1 at 5.0 A g-1, which can provide a possibility for designing new anode materials for rechargeable batteries.