Mg₂Nb₃₄O₈₇ Porous Microspheres for Use in High-Energy, Safe, Fast-Charging, and Stable Lithium-Ion Batteries

M–Nb–O compounds are advanced anode materials for lithium-ion batteries (LIBs) due to their high specific capacities, safe operating potentials, and high cycling stability. Nevertheless, the found M–Nb–O anode materials are very limited. Here, Mg₂Nb₃₄O₈₇ is developed as a new M–Nb–O material. Mg₂Nb₃₄O₈₇ porous microspheres (Mg₂Nb₃₄O₈₇-P) with primary-particle sizes of 30–100 nm are fabricated based on a solvothermal method. Mg₂Nb₃₄O₈₇ has an open 3 × 4 × ∞ Wadsley–Roth shear structure and a large unit-cell volume, leading to its largest Li⁺ diffusion coefficients among all the developed M–Nb–O anode materials. In situ X-ray diffraction analyses reveal its high structural stability and intercalating characteristic. These architectural, conductivity, and structural advantages in Mg₂Nb₃₄O₈₇-P lead to its most significant intercalation pseudocapacitive contribution (87.7% at 1.1 mV s^–1) among the existing M–Nb–O anode materials and prominent rate capability (high reversible capacities of 338 mAh g^–1 at 0.1C and 230 mAh g^–1 at 10C). Additionally, this new material exhibits a safe operating potential (∼1.68 V), an ultrahigh initial Coulombic efficiency (94.8%), and an outstanding cycling stability (only 6.9% capacity loss at 10C over 500 cycles). All of these evidences indicate that Mg₂Nb₃₄O₈₇-P is an ideal anode material for high-energy, safe, fast-charging, and stable LIBs

GaNb₁₁O₂₉ Nanowebs as High-Performance Anode Materials for Lithium-Ion Batteries

M–Nb–O compounds have been considered as promising anode materials for lithium-ion batteries (LIBs) because of their high capacities, safety, and cyclic stability. However, very limited M–Nb–O anode materials have been developed thus far. Herein, GaNb₁₁O₂₉ with a shear ReO₃ crystal structure and a high theoretical capacity of 379 mAh g^–1 is intensively explored as a new member in the M–Nb–O family. GaNb₁₁O₂₉ nanowebs (GaNb₁₁O₂₉-N) are synthesized based on a facile single-spinneret electrospinning technique for the first time and are constructed by interconnected GaNb₁₁O₂₉ nanowires with an average diameter of ∼250 nm and a large specific surface area of 10.26 m² g^–1. This intriguing architecture affords good structural stability, restricted self-aggregation, a large electrochemical reaction area, and fast electron/Li⁺-ion transport, leading to a significant pseudocapacitive behavior and outstanding electrochemical properties of GaNb₁₁O₂₉–N. At 0.1 C, it shows a high specific capacity (264 mAh g^–1) with a safe working potential (1.69 V vs Li/Li⁺) and the highest first-cycle Coulombic efficiency in all of the known M–Nb–O anode materials (96.5%). At 10 C, it exhibits a superior rate capability (a high capacity of 175 mAh g^–1) and a durable cyclic stability (a high capacity retention of 87.4% after 1000 cycles). These impressive results indicate that GaNb₁₁O₂₉-N is a high-performance anode material for LIBs