A breakthrough study published in Nano-Micro Letters reveals how a critical bimetallic phosphide layer (CBPL) can simultaneously accelerate electron transfer and deliver extra energy in nickel-zinc batteries, shattering the traditional ceiling on energy and power density. Led by Liang He from Sichuan University, the work establishes a scalable, bifunctional surface-modification route that turns NiCo-layered double hydroxide (NiCo-LDH) cathodes into record performers for flexible quasi-solid-state zinc batteries.
Why This Research Matters
• Overcoming Nickel-Cathode Limitations: Conventional nickel-based cathodes suffer from sluggish kinetics, low active-material utilization and structural collapse, restricting aqueous zinc batteries to modest energy density. The CBPL strategy directly tackles these bottlenecks by introducing a highly conductive heterostructure that both transports electrons and participates in redox reactions.
• Enabling Flexible, Fast-Charging Devices: Beyond grid storage, wearable electronics, IoT sensors and soft robotics demand compact, safe and deformable power sources. The reported flexible pouch cells maintain stable output under repeated bending, validating real-world viability.
Innovative Design and Mechanisms
• Gradient Phosphidizing & Heterostructure Engineering: A precisely controlled low-temperature phosphidizing treatment converts the outer surface of NiCo-LDH into a nanoscale Ni 2 P/Co 2 P layer while preserving an inner NiCo-LDH core. The resulting core–shell architecture forms abundant heterointerfaces that redistribute charge density and lower the OH - adsorption energy (−1.31 eV versus −0.77 eV for bare LDH).
• Dual-Function CBPL: Unlike conventional surface coatings that merely protect, the CBPL is electrochemically active. It provides an additional low-voltage redox plateau (≈0.35 V versus Hg/HgO) that supplements the high-voltage Ni(OH) 2 /Co(OH) 2 ↔ NiOOH/CoOOH reaction, effectively doubling the depth-of-discharge without sacrificing rate capability.
• Fast Electron/Ion Transport: The metallic conductivity of Ni 2 P/Co 2 P, combined with the intimate heterojunction, cuts charge-transfer resistance to <1 Ω and enables 72 % capacity retention at 40 C. Density-functional theory confirms a ten-fold increase in electronic states near the Fermi level compared with pristine LDH.
Applications and Future Outlook
• Record Energy/Power Metrics: Assembled NiCo-P 1.0 //Zn full cells deliver 503.62 Wh kg -1 at 493 W kg -1 and 18.62 kW kg -1 at 336 Wh kg -1 —outperforming state-of-the-art nickel-zinc, zinc-ion and alkaline chemistries.
• Flexible Quasi-Solid-State Pouch Cells: A 2 cm × 2 cm hydrogel-based pouch sustains 150 cycles at 1 C with 71 % retention while powering a timer during 6 h of flat-bend-flat deformation. Three cells in series light a 34-red/46-yellow LED neon sign, demonstrating modular scalability.
• Scalable Manufacturing: The method employs earth-abundant Ni, Co and NaH 2 PO 2 , uses open-air phosphidizing at 350 °C and is directly compatible with roll-to-roll coating onto carbon cloth, promising low-cost mass production.
• Future Research Directions: Next steps include optimizing phosphorus dosage to suppress phosphate by-products, integrating CBPL with 3D-printed current collectors and coupling the cathode with dendrite-free zinc anodes for 10 000-cycle grid modules.
Conclusions
This study demonstrates that a critical bimetallic phosphide layer can simultaneously act as a high-conductivity highway and an extra energy reservoir, pushing aqueous nickel-zinc batteries well beyond their traditional limits. With unmatched energy/power density and mechanical flexibility, the CBPL-modified NiCo-LDH platform paves the way for next-generation safe, fast-charging and bendable energy-storage systems across consumer electronics and large-scale storage markets.
Nano-Micro Letters
Experimental study
Critical Bimetallic Phosphide Layer Enables Fast Electron Transfer and Extra Energy Supply for Flexible Quasi-Solid-State Zinc Batteries
21-May-2025