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A new phase Na 2 Ti 3 O 7 compound is synthesized by solid-state method for the first time, which is verified to belong to the triclinic structure in P-1 space group. Compared to the conventional monoclinic Na 2 Ti 3 O 7 (m-NTO), in P2 1 /m1 space group, the triclinic Na 2 Ti 3 O 7 (t-NTO) possesses a shorter O-O band in the distorted TiO 6 octahedron, which accounts for more smooth Na + transport channels and a more stable layered structure with smaller fluctuation. The experimental results show that the t-NTO keeps a low charge potential plateau at 0.3 V compared to the m-NTO, but with much promoted structure resilience. It delivers a capacity retention of 94.7%, far exceeding the 25.7% of the m-NTO upon decades of cycles. In situ X-ray diffraction reveals that the conventional m-NTO experiences an irreversible phase transition during insertion/de-insertion of Na + , while the new t-NTO can recover its structure reversibly after discharge and charge, which is consistent with its improved cycling performance. The results demonstrate a new t-NTO anode and provide a new understanding for the phase diversity of sodium-ion battery materials.

Straw retention, an alternative to artificial fertilization, commonly mitigates soil degradation and positively affects soil fertility. In this study, we investigated the succession of soil bacteria during two sugarcane straw retention treatments (control (CK) and sugarcane straw retention (SR)) and at four depths (0–10, 10–20, 20–30, and 30–40 cm) in fallow soil in a sugarcane cropping system. Using an Illumina MiSeq (16S rRNA) and soil enzyme activity, we explored the SR influence on soil bacterial communities and enzyme activities and its inclusive impact on soil fertility, with an emphasis on topsoil (0–10 cm) and subsoil (10–40 cm). Our results show that SR effectively improved soil fertility indicators (C, N, and P), including enzyme activities (C and N cycling), throughout the soil profile: these soil parameters greatly improved in the topsoil compared to the control. Sugarcane straw retention and soil depth (0–10 cm vs. 10–40 cm) were associated with little variation in bacterial species richness and alpha diversity throughout the soil profile. Subsoil and topsoil bacterial communities differed in composition. Compared to the CK treatment, SR enriched the topsoil with Proteobacteria, Verrucomicrobia, Actinobacteria, Chloroflexi, and Nitrospirae, while the subsoil was depleted in Nitrospirae and Acidobacteria. Similarly, SR enriched the subsoil with Proteobacteria, Verrucomicrobia, Actinobacteria, Chloroflexi, Gemmatimonadetes, and Bacteroidetes, while the topsoil was depleted in Acidobacteria, Gemmatimonadetes, and Planctomycetes compared to the CK. At the genus level, SR enriched the topsoil with Gp1, Gp2, Gp5, Gp7, Gemmatimonas, Kofleria, Sphingomonas, and Gaiella, which decompose lignocellulose and contribute to nutrient cycling. In summary, SR not only improved soil physicochemical properties and enzyme activities but also enriched bacterial taxa involved in lignocellulosic decomposition and nutrient cycling (C and N) throughout the soil profile. However, these effects were stronger in topsoil than in subsoil, suggesting that SR enhanced fertility more in topsoil than in subsoil in fallow land.

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