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Ni-rich layered oxides are regarded as next-generation cathode materials for lithium-ion batteries with high energy density. However, these materials suffer capacity degradation and power fade at high cutoff voltages. Herein, a robust La, Zr nanocomposite oxide coating layer is successfully deposited on the LiNi0.6Co0.2Mn0.2O2 surface using a wet-chemical method. The surface modified LiNi0.6Co0.2Mn0.2O2 exhibits improved rate capability and superior cycling performance even at a high cutoff voltage of 4.5 V. Ex situ analyses uncover the capacity fading mechanisms of LiNi0.6Co0.2Mn0.2O2 and the effects of the coating layer by a combination of X-ray diffraction, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. The results show that particle cracking, structural transformation, and interfacial side reactions are responsible for the inferior performance of pristine LiNi0.6Co0.2Mn0.2O2. Nevertheless, the coating layer not only retains structural integrity and suppresses irreversible surface phase transformation, but also alleviates accumulation of highly resistive species on the cathode surface. This investigation highlights the advantages of combining multiple techniques in investigating the effects of surface modification and could be extended to explore other coating materials.

LiNixCoyMnzO2 cathode materials play a vital role in next-generation lithium-ion batteries because of their high energy density, but they suffer capacity decay at elevated temperatures. Improving the cycling stability of LiNixCoyMnzO2 requires a basic comprehension of its capacity fade mechanisms. Here, we investigate the electrochemical performance of LiNi0.6Co0.2Mn0.2O2 at 55 °C under various cutoff voltages and examine the corresponding degradation mechanisms. The discharge capacity of LiNi0.6Co0.2Mn0.2O2 increases from 176.0 mAh g−1 to 218.1 mAh g−1 at 1 C as the cutoff voltage increases from 4.3 V to 4.7 V, whereas the capacity retention decreases from 96.3% to 78.9% after 50 cycles, respectively. Ex situ analyses via high-resolution transmission electron microscopy illuminate structural transformations of cathode materials after electrochemical cycling. This accounts for the increase in charge transfer resistance and capacity loss. In addition, X-ray photoelectron spectroscopy analyses highlight the correlations between the electrochemical performance and interfacial compositions of the cathode/electrolyte interface. These data provide another explanation for the capacity degradation. Our results underscore the value of improving the surface structural stability of cathode materials and reducing the charge transfer resistance of the electrode/electrolyte interface.

Nanoscale coordination polymers (NCPs) are promising nanomedicine platforms featured with biodegradability and versatile functionalities. However, multi-step post-synthesis surface modification is usually required to functionalize as-made NCPs before their biomedical applications. Moreover, efforts are still required to design therapeutic NCPs responsive to the unique tumor microenvironment to achieve more specific and effective therapy. Herein, we uncover a simple yet general strategy to synthesize a series of polyethylene glycol (PEG) modified NCPs via a one-step method by adding poly-histidine-PEG co-polymer into the mixture of metal ions and organic ligands during NCPs formation. With NCPs consisting Ca2+/dicarboxylic cisplatin (IV) prodrug as the example, we show that such Ca/Pt(IV)@pHis-PEG NCPs are highly sensitive to pH changes. With slightly negative charges and compact structure under pH 7.4 during blood circulation, those NCPs exhibit efficient passive accumulation in the tumor, in which the reduced pH (c.a. 6.5) would trigger charge conversion and size expansion to enhance their tumor retention and cell internationalization. After cellular uptake, NCPs within cell endo-/lysosomes with further reduced pH would then lead to decomposition of those NCPs and thus drug release. Chemotherapy with Ca/Pt(IV)@pHis-PEG NCPs in our animal tumor model demonstrates great efficacy under low drug doses, and is found to be particularly effective towards solid tumors with reduced pH.

Ni-rich cathode materials attract ongoing interest due to their high specific capacity (∼200 mAh g−1). However, these materials suffer rapid capacity fading when charged to a high voltage and cycled at elevated temperature. In this study, we propose a facile method to reconstruct the surface structure of LiNi0.6Co0.2Mn0.2O2 via Nb modification, which integrates the merits of partial Nb5+ doping in the pristine structure and surface Li3NbO4 coating. The obtained results from Rietveld refinement and high resolution transmission electron microscopy confirm that Nb5+ is partially doped into Li+ sites within the surface lattice. Further ex-situ powder X-ray diffraction and kinetic analysis using electrochemical impedance spectroscopy reveal that Nb modification stabilizes the layered structure and facilitates the charge transfer process. Owing to the robust surface structure, 1 mol% Nb modified LiNi0.6Co0.2Mn0.2O2 delivers a discharge capacity of 160.9 mAh g−1 with 91% capacity retention after 100 cycles at 3.0–4.5 V, whereas the discharge capacity of the pristine sample drops to 139.6 mAh g−1, corresponding to 78% of its initial value. The presence of Nb5+ in the Li layer exhibits positive effects on stability of layered structure, and the surface Li3NbO4 coating layer increases interfacial stability, which results in superior electrochemical performance.

Improving tumor oxygenation and concentrating X-ray radiation energy inside the tumor have received considerable attention in cancer radiotherapy. Herein, core–shell tantalum oxide@manganese dioxide (TaOx@MnO2) nanostructures are prepared as an efficient radiosensitizer for enhancing radiotherapy (RT). In these nanostructures, the TaOx core serves as a RT sensitizer that efficiently concentrates X-ray radiation energy inside the tumor, while the MnO2 shell may trigger the decomposition of endogenous H2O2 in the tumor microenvironment (TME) to generate oxygen and overcome hypoxia-associated radiation resistance. In vitro and in vivo experiments demonstrated that the synthesized TaOx@MnO2-PEG nanostructures could accomplish an excellent synergistic radiotherapy sensitization effect. Furthermore, TaOx@MnO2-PEG nanoparticles could also serve as promising agents for MR/CT dual-modal imaging. In brief, our study highlights a new type of multifunctional radiosensitizer agent to enhance radiotherapy treatment by means of simultaneously concentrating radiation energy inside tumors and overcoming tumor hypoxia, promising for applications in tumor radiotherapy.

Nanoscale coordination polymers (NCPs), with inherent biodegradability, chemical diversities, and porous structures, are a promising class of nanomaterials in the nanomedicine field. Herein, a unique type of redox-sensitive NCPs is constructed with manganese ions (Mn2+) and dithiodiglycolic acid as the disulfide (SS)-containing organic bridging ligand. The obtained Mn-SS NCPs with a mesoporous structure could be efficiently loaded with doxorubicin (DOX), a chemotherapeutics. The yielded Mn-SS/DOX nanoparticles are coated with a layer of polydopamine (PDA) and then modified by poly(ethylene glycol) (PEG). In such a Mn-SS/DOX@PDA-PEG NCP structure, the disulfide linkage (SS) within dithiodiglycolic acid can be cleaved in the presence of glutathione (GSH), leading to efficient redox-responsive dissociation of NCPs and the subsequent drug release. Meanwhile, Mn2+ in Mn-SS/DOX@PDA-PEG NCPs would offer a strong T1 contrast in magnetic resonance (MR) imaging, Upon intravenous injection, these Mn-SS/DOX@PDA-PEG N...

A high-capacity Si anode is always accompanied by very large volume expansion and structural collapse during the lithium-ion insertion/extraction process. To stabilize the structure of the Si anode, magnesium vapor thermal reduction has been used to synthesize porous Si and SiO2 (pSS) particles, followed by in situ growth of carbon nanotubes (CNTs) in pSS pores through a chemical vapor deposition (CVD) process. Field-emission scanning electron microscopy and high-resolution transmission electron microscopy have shown that the final product (pSS/CNTs) possesses adequate void space intertwined by uniformly distributed CNTs and inactive silica in particle form. pSS/CNTs with such an elaborate structural design deliver improved electrochemical performance, with better coulombic efficiency (70% at the first cycle), cycling capability (1200 mAh g–1 at 0.5 A g–1 after 200 cycles), and rate capability (1984, 1654, 1385, 1072, and 800 mAh g–1 at current densities of 0.1, 0.2, 0.5, 1, and 2 A g–1, respectively), co...

In this study, Zn–Fe–O@C hollow microspheres are prepared by chemical vapor deposition (CVD) method with ZnFe2O4 hollow microspheres as precursors which are synthesized via a facile solvothermal method. ZnFe2O4 hollow microspheres and Zn–Fe–O@C hollow microspheres are characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy and transmission electron microscopy. The physical analysis shows a fraction of Fe(III) reduced to Fe(II) and the hollow microspheres maintained during the CVD process. Zn–Fe–O@C hollow microspheres can deliver a reversible specific capacity of 1035.6 mA h g−1 after 50 cycles at a current density of 100 mA g−1, and maintain a stable capacity as high as 1000 mA h g−1 at 500 mA g−1 after 200 cycles. Compared with ZnFe2O4 hollow microspheres, Zn–Fe–O@C hollow microspheres present excellent rate performance. The better electrochemical performances of the Zn–Fe–O@C hollow microspheres should be ascribed to the carbon coating, which can elevate electrical conductivity and improve the structural stability of the active materials.