Template-Free Synthesis of Nanoporous Nickel and Alloys as Binder-Free Current Collectors of Li Ion Batteries

3D Co-Doping α-Ni(OH)2 Nanosheets for Ultrastable, High-Rate Ni-Zn Battery

The α-Ni(OH)₂ is regarded as one promising cathode for aqueous nickel-zinc batteries due to its high theoretical capacity of ≈480 mAh g^-1 , its practical deployment however suffers from the poor stability in strong alkaline solution, intrinsic low electrical conductivity as well as the retarded ionic diffusion. Herein, a 3D (three dimensional) macroporous α-Ni(OH)₂ nanosheets with Co doping is designed through a facile and easily scalable electroless plating combined with electrodeposition strategy. The unique micrometer-sized 3D pores come from Ni substrate and rich voids between Co-doping α-Ni(OH)₂ nanosheets can synergistically afford facile, interconnected ionic diffusion channels, sufficient free space for accommodating its volume changes during cycling; meanwhile, the Co-doping can stabilize the structural robustness of the α-Ni(OH)₂ in the alkaline electrolyte during cycling. Thus, the 3D α-Ni(OH)₂ shows a high capacity of 284 mAh g^-1 at 0.5 mA cm^-2 with an excellent retention of 78% even at 15 mA cm^-2 , and more than 2000 stable cycles at 6 mA cm^-2 , as well as the robust cycling upon various flexible batteries. This work provides a simple and efficient pathway to enhance the electrochemical performance of Ni-Zn batteries through improving ionic transport kinetics and stabilizing crystal structure of cathodes.

Controllable 3D Porous Ni Current Collector Coupled with Surface Phosphorization Enhances Na Storage of Ni3 S2 Nanosheet Arrays

3D porous Ni is fabricated via an easily scalable electroless plating method using a dynamic template formed through in-situ hydrogen bubbles. The pore size in the range of several micrometers is controllable through adjusting the Ni²⁺ depositing rate and hydrogen bubbles releasing rate. The Ni₃ S₂ nanosheet arrays anode is then grown on the unique 3D porous Ni current collector followed by subsequent surface phosphorization. The tremendous interconnected pores and rich voids between the Ni₃ S₂ nanosheet arrays cannot only provide rapid transferring channels for Na⁺ , but also accommodate volumetric changes of the Ni₃ S₂ electrode during cycling, guaranteeing the integrity of the active material. In addition, the surface phosphorized layer enhances the electronic conductivity through providing an electron transport highway along the 3D Ni₃ S₂ , NiP₂ layer, and 3D porous Ni current collector, and simultaneously stabilizes the electrode/electrolyte interphase as a protecting layer. Because of these merits, the phosphorized 3D porous Ni₃ S₂ (3D P-Ni₃ S₂ ) electrode is capable of delivering an ultra-stable capacity of 387.5 mAh g^-1 at 0.1 A g^-1 , and a high capacity retention of 85.3% even at a high current density of 1.6 A g^-1 .

Lightweight Through-Hole Copper Foil as a Current Collector for Lithium-Ion Batteries

In the past few decades, much effort has been dedicated to improve electrochemical performance of lithium-ion batteries (LIBs) through material design. Less attention, however, has been paid to structure engineering of battery components, which is an effective way for improving the electrochemical performance of LIBs. In this work, a lightweight Cu current collector with a through-hole array and columnar crystal on the surface (CC/THCu) was designed and fabricated using a nanosecond ultraviolet laser and electrodeposition processing to enhance specific capacity and cycle stability of LIBs. The synergistic effect of the columnar crystal and through-hole structure for improving electrochemical performances of LIBs assembled with the CC/THCu current collector was investigated. The results show that the complex structure provides spaces for volume expansion and reduces volume variation. When the hole fraction reaches 20%, the weight loss of CC/THCu is 28.41%. The corresponding LIB with the 20% hole fraction CC/THCu shows a high residual capacity rate of 81.2% and enhanced specific capacity (55.9% compared to the LIB with a bare Cu current collector). At a high rate of 1 C, the remaining specific capacity of the LIB with the CC/THCu current collector is better than that with the bare Cu current collector after 200 cycles. The CC/THCu current collector effectively improves the specific capacity and cycle stability of LIBs in contrast to the bare Cu current collector.