Long-life Na-rich nickel hexacyanoferrate capable of working under stringent conditions

Abstract

Prussian blue materials have been considered as ideal cathodes for sodium-ion batteries (SIBs) because of their unique open framework structure. Among those, nickel hexacyanoferrate (NiHCF) with “zero strain” characteristics is of peculiar interest. In this work, large-size, multi-edge structured Na-rich NiHCF was prepared via a controlled coprecipitation method. At 25 °C, the NiHCF exhibits extremely stable cycling with 90.4% capacity retained after 16 000 cycles at 20C (1C = 85 mA g⁻¹). Besides, the material shows superior rate capability with 78.5% capacity yielded at 50C relativ to 0.2C. The material also exhibits stable cycling under stringent conditions, namely, at high/low temperatures and after overcharge/overdischarge abuse. High capacity retentions, 95.5% over 600 cycles at 60 °C and 91.9% over 1800 cycles at −20 °C, are achieved for this material after being cycled at 5C. After overcharge to 4.8 V and overdischarge to 1.2 V, the NiHCF can still exhibit good cycling stability with both the structure and capacity recovered in the normal voltage window. The NiHCF also demonstrates a long cycle life in an aqueous NiHCF/Zn battery, maintaining 84.1% capacity after 3100 cycles at 5C. A scale-up preparation of kilogram-grade NiHCF was realized and pouch-type NiHCF/hard carbon full batteries were fabricated and evaluated to realize potential applications of the material.