Nanosized anatase TiO2 with exposed (001) facet for high‑capacity Mg2+ ion storage in magnesium ion batteries

As demand for safe, low-cost energy storage grows, rechargeable magnesium batteries (MIBs) offer a promising alternative to lithium-ion technology—yet their development is hindered by the sluggish diffusion of Mg²⁺ within conventional electrode lattices. Now, researchers from Chongqing University and the University of Oxford, led by Dr. Jili Yue, Dr. Guangsheng Huang, and Prof. Fusheng Pan, have unveiled a nanostructured anatase TiO₂ cathode that exposes the highly reactive (001) facet, doubling capacity and setting a new benchmark for Mg²⁺ storage performance.

Why the (001) Facet Matters

• Interfacial Storage Boost: First-principles calculations show the (001) surface lowers Mg²⁺ diffusion barriers to 0.475 eV—far below bulk TiO₂ (0.637 eV)—and delivers the strongest adsorption energy (−2.14 eV), enabling rapid, reversible interfacial storage.
• Dual-Salt Synergy: In Mg–Li hybrid electrolytes, the “charge-shielding” effect of Li⁺ further accelerates Mg²⁺ kinetics, yielding 312.9 mAh g^-1—triple that of micron-sized TiO₂ and outperforming state-of-the-art cathodes such as VO₂, MoS₂, and MXenes.
• Stable Long-Term Cycling: The (001)-dominated nanosheets retain 170.6 mAh g⁻¹ after 1 070 cycles at 1 A g^-1 and power 20 yellow LEDs in series-connected pouch cells, demonstrating real-world viability.

Innovative Design and Features

• Facet-Controlled Synthesis: A one-step hydrothermal route with HF tunes nanosheet thickness to ~12 nm, maximizing (001) exposure and surface area (126 m² g^-1) while preserving structural integrity over thousands of cycles.
• Multiscale Characterization: Ex-situ XRD, XPS, and depth-profiling confirm reversible Mg²⁺/Li⁺ co-intercalation without phase transitions; contact-angle measurements reveal superior electrolyte wettability (47°) that lowers interfacial resistance.
• Mechanistic Insight: CI-NEB and Bader analyses quantify faster ion migration and larger charge transfer (1.29 |e|) on (001), corroborating pseudocapacitive contributions up to 89 % at high scan rates.

Applications and Future Outlook

• Grid-Scale Storage: The low-cost, dendrite-free Mg metal anode paired with facet-engineered TiO₂ opens a safe, high-energy pathway for stationary batteries.
• Flexible Electronics: Ultrathin, bendable pouch cells maintain 77 % capacity after 378 cycles, promising wearables and IoT devices.
• Scalable Manufacturing: Hydrothermal synthesis uses commodity precursors and is compatible with roll-to-roll coating, easing commercial translation.

This work provides a clear design principle—crystal-facet nanostructuring—for unlocking multivalent-ion storage and propelling magnesium batteries toward market readiness. Stay tuned for further advances from the Chongqing University energy-storage team!