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Ni-rich layered cathodes have been regarded as one of the high-priority materials, but their commercial application was limited by the highly active surfaces, poor thermal stability, and irreversible phase transition. Furthermore, when they are stored in moist air, the particles can easily form an impurity layer of Li2CO3/LiOH. This inert substance hinders the transmission of lithium ions and electrons, leading to electrochemical performance deterioration. Herein, we report a simple method, namely, metaphosphate repair, which can successfully restore the degraded LiNi0.8Co0.1Mn0.1O2(NCM811) cathode materials and form an in situ multifunctional hybrid repaired layer of Li3PO4-YPO4-Y(PO3)3on the secondary particle. The repaired NCM811 delivers a discharge capacity of 171.7 mAh g–1after 100 cycles, which is much higher than those of pristine (147.6 mAh g–1) and stored degraded (116.2 mAh g–1) samples. Moreover, the restored sample could deliver a capacity retention of 92.3% after 100 cycles at 1C along with a better initial Coulombic efficiency (CE) of 88.4%. This study provides a facile strategy to revive degraded Ni-rich cathode materials and other similar layered oxide cathodes for advanced batteries.

Single-crystalline LiNi0.6Co0.2Mn0.2O2cathodes have received great attention due to their high discharge capacity and better electrochemical performance. However, the single-crystal materials are suffering from severe lattice distortion and electrode/electrolyte interface side reactions when cycling at high voltage. Herein, a unique single-crystal LiNi0.6Co0.2Mn0.2O2with Al and Zr doping in the bulk and a self-formed coating layer of Li2ZrO3in the surface has been constructed by a facile strategy. The optimized cathode material exhibits excellent structural stability and cycling performance at room/elevated temperatures after long-term cycling. Specifically, even after 100 cycles (1C, 3.0–4.4 V) at 50 °C, the capacity retention for the Al and Zr co-doped sample reaches 92.1%, which is much higher than those of the single Al-doped (85.4%), single Zr-doped (87.1%), and bare samples (76.3%). The characterization results and first-principles calculations reveal that the excellent electrochemical properties are attributed to the stable structure and interface, in which the Al and Zr co-doping hinders cation mixing and suppresses detrimental phase transformations to reduce internal stress and mitigate microcracks, and the coating layer of Li2ZrO3can protect the surface and suppress interfacial parasitic reactions. Overall, this work provides important insights into how to simultaneously build a stable bulk structure and interface for the single-crystal NCM cathode via a facile preparation process.

Silicon (Si) has been considered as the most potential anode material for next-generation high-energy density lithium-ion batteries (LIBs) because of its extremely high theoretical capacity. However, the performance deterioration caused by volume change and low electrical conductivity of active Si particles greatly limit its commercial use. Here, we designed a nonstoichiometric TiOx-coated Si anode with a litchi-like structure, in which Si–Ti and Si–O dual bonds are expected to form between the Si core and TiOxshell. This unique structure plays a major role in preventing the volume expansion and improving the electrical conductivity of the Si anode. The as-prepared TiOx-coated Si anode could exhibit excellent cycling stability after 1000 cycles at 1000 mA g–1with a relatively small capacity decay rate of ∼0.04% per cycle, which can be comparable to most of the modified Si anodes in references. This strategy of surface regulating on the Si anode could be extended to other electrodes with large volume expansion during cycling in LIBs for achieving competitive electrochemical properties.

Si-based anode materials have attracted considerable attention because of their ultrahigh reversible capacity. However, poor cycling stability caused by the large volume change during cycling prevented the commercial application of Si anodes for lithium-ion batteries (LIBs). To overcome these challenges, in the present study, we designed a nitrogen plasma-treated core–bishell nanostructure where the Si nanoparticle was encapsulated into a SiOxshell and N-doped TiO2−δshell. Here, the SiOxinside the shell and the TiO2outside the shell act as binary buffer matrices to accommodate the large volume change and also help to stabilize the solid electrolyte interphase films on the shell surface. More importantly, the plasma-induced N-doped TiO2−δshell with many Ti3+species and oxygen vacancies plays a key role in improving the electrical conductivity of Si anodes. Owing to the synergistic effects of SiOxand N-doped TiO2−δbishells, the cycling stability and rate performance of Si anodes are significantly enhanced. The as-obtained sample exhibits superior cycling stability with a capacity retention of 650 mA h g–1at 200 mA g–1after 300 cycles. This strategy is favorable for improving the electrochemical performances of Si-based anodes to employ in practical LIBs.

Inferior cycling stability at elevated temperature is a big challenge for the commercial application of nickel-rich cathode materials because more serious phase transition, transition metal ion dissolution and side reaction of interface happen at elevated temperature than at room temperature. In the present work, strategies of element doping and surface coating are utilized together to stabilize the structure and interface electrochemistry. We successfully synthesized a Zr-doped and LiAlO2-Al2O3 coated LiNi0.8Co0.1Mn0.1O2 material by a simple ball milling and wet chemical method. Owing to the synergistic effect of Zr doping and dual LiAlO2-Al2O3 coating, when cycled at 50degC, the modified LiNi0.8Co0.1Mn0.1O2 sample exhibited significantly improved cycling stability with a capacity retention of over 96.8% after 60 cycles at a current rate of 1C, while the pristine sample could only retain a capacity of 73.3%. This improved electrochemical performance can be attributed to the effective doping and coating technique employed to the LiNi0.8Co0.1Mn0.1O2 sample. The Zr doping is beneficial to reduce cation mixing and suppress the phase transition, while the LiAlO2-Al2O3 coating helps to enhance the protection of the electrode/electrolyte interface and reduce the transition metal ion dissolution.

The capacity fluctuation phenomenon during cycling, which is closely related with solid electrolyte interphase and plays a key role for the design for advanced electrode, could be frequently observed in the titanium-based anode. However, the underlying reason for capacity fluctuation still remains unclear with rare related reports. Here, the origin of capacity fluctuation is verified with a long-life Na2Ti6O13anode. The reaction mechanism, structural evolution and reaction kinetics during the reported sodiation/desodiation processes were carefully investigated. The gradually enhanced diffusion controlled contribution resulted in the capacity increasing. And the capacity decay could be ascribed to the irreversible reaction of metallic titanium formation and the increasing potential polarization. It is worth noting that sodium ions seem to partially reduce NTO to metallic state, which is irreversible. The present study can provide more information for the design of advanced Na2Ti6O13anode.

The present study provides detailed experimental results on the synthesis and characterization of carbonized lithium titanate spinel (LTO) composites as electrode materials for lithium ion capacitor. The LTO particles were grafted with a porous carbon layer obtained from the pyrolysis of camphor. The graphitic nature of the carbon was confirmed through Raman spectroscopy. The relative contributions from the capacitive and diffusion controlled processes underlying these electrodes were mathematically modeled. Electron transport mechanism underlying these electrodes was determined by measuring the work functions (φ) of LTO and carbon grafted LTO using ultraviolet photoelectron spectroscopy. These carbon grafted LTO composites exhibited an energy density of 330 mWh·L−1and a peak power density of 2.8 kW·L−1, when employed as electrodes in coin cells with excellent cycling stability at the end of 4000 cycles.

Energy conversion technologies like fuel cells and metal-air batteries require oxygen reduction reaction (ORR) electrocatalysts with low cost and high catalytic activity. Herein, N-doped carbon spheres (N-CS) with rich micropore structure have been synthesized by a facile two-step method, which includes the polymerization of pyrrole and formaldehyde and followed by a facile pyrolysis process. During the preparation, zinc chloride (ZnCl2) was utilized as a catalyst to promote polymerization and provide a hypersaline environment. In addition, the morphology, defect content and activity area of the resultant N-CS catalysts could be regulated by controlling the content of ZnCl2. The optimum N-CS-1 catalyst demonstrated much better catalytic activity and durability towards ORR in alkaline conditions than commercial 20 wt% Pt/C catalysts, of which the half-wave potential reached 0.844 V vs. RHE. When applied in the Zn-air batteries as cathode catalysts, N-CS-1 showed a maximum power density of 175 mW cm-2and long-term discharging stability of over 150 h at 10 mA cm-2, which outperformed 20 wt% Pt/C. The excellent performance could be due to its ultrahigh specific surface area of 1757 m2g-1and rich micropore channels structure. Meanwhile, this work provides an efficient method to synthesize an ultrahigh surface porous carbon material, especially for catalyst application.

Inferior cycling stability at elevated temperature is a big challenge for the commercial application of nickel-rich cathode materials because more serious phase transition, transition metal ion dissolution and side reaction of interface happen at elevated temperature than at room temperature. In the present work, strategies of element doping and surface coating are utilized together to stabilize the structure and interface electrochemistry. We successfully synthesized a Zr-doped and LiAlO2-Al2O3coated LiNi0.8Co0.1Mn0.1O2material by a simple ball milling and wet chemical method. Owing to the synergistic effect of Zr doping and dual LiAlO2-Al2O3coating, when cycled at 50°C, the modified LiNi0.8Co0.1Mn0.1O2sample exhibited significantly improved cycling stability with a capacity retention of over 96.8% after 60 cycles at a current rate of 1C, while the pristine sample could only retain a capacity of 73.3%. This improved electrochemical performance can be attributed to the effective doping and coating technique employed to the LiNi0.8Co0.1Mn0.1O2sample. The Zr doping is beneficial to reduce cation mixing and suppress the phase transition, while the LiAlO2-Al2O3coating helps to enhance the protection of the electrode/electrolyte interface and reduce the transition metal ion dissolution.