Prussian blue analogue-derived porous nanocages with hollow (Co,Fe)O nanoparticles as anodes for lithium ion batteries

CoFe-Prussian blue analog (CoFe-PBA) template derived porous nanocages comprising hollow (Co,Fe)O nanoparticles are introduced as a highly efficient anode for lithium-ion batteries (LIBs) by integrating the co-precipitation and nanoscale Kirkendall diffusion processes. This strategic approach employs a solution-based facile polydopamine (PDA)-derived carbon coating process to control the oxidation rate of nanoparticles during subsequent heat treatment to achieve the hollow structure by the nanoscale Kirkendall diffusion effect. The application of different concentrations of PDA to the nanocages resulted in the formation of porous nanocages of three types, such as (Co,Fe)O@PDA-C-20, (Co,Fe)O@PDA-C-100, and (Co,Fe)O@PDA-C-200. Notably, (Co,Fe)O@PDA-C-100 porous nanocages exhibit remarkable cycling stability by the hollow structured (Co,Fe)O nanoparticles. Additionally, the hollow and porous structures facilitate rapid charge species diffusion, efficient electrolyte infiltration, and effective management of volumetric changes. When used as anodes for LIBs, the hollow (Co,Fe)O@PDA-C-100 anodes demonstrate impressive structural robustness and high-rate performance. They exhibit remarkable structural integrity, demonstrating stable cycling performance for up to 300 cycles at 0.5 and 1.0 A g⁻¹ (capacity retentions of 99.3% and 97.2%, respectively). In terms of rate capability, the hollow (Co,Fe)O@PDA-C-100 porous nanocages exhibit a high discharge capacity of 284 mA h g⁻¹ at 10 A g⁻¹. Moreover, the practical application potential of the prepared hollow (Co,Fe)O@PDA-C-100 anode is demonstrated by a full-cell test paired with and Li(Ni_0.8Co_0.1Mn_0.1)O₂ cathode under the condition of practical application. This clearly highlights the structural advantages of the prepared hollow (Co,Fe)O@PDA-C-100 porous nanocages.