Because of their nanoporous composition, large surface area, porosity, three-dimensional (3D) conducting matrix, and remarkable flexibility, nanoporous metals have received a lot of interest in battery storage applications. A recent paper published in the journal ACS Applied Energy Materials describes a simple approach for making Si-Ni nanofoam composite materials for a high loading Si electrode in lithium (Li)-ion rechargeable batteries.
Lithium-ion Batteries: The Future of Energy Storage Applications
Renewable energy has become a necessary endeavor to reduce the world's dependency on fossil fuels, both ecologically destructive and limited in supply. Because many renewable sources of energy are inherently intermittent, energy storage must be included as part of any energy recovery system.
Lithium-ion batteries (LIBs) are the most rapidly developing energy storage system compared to all other systems. Boosting their energy storage capability is an important research topic for incorporation in many modern applications, and LIBs' near-exclusive dependence on graphitic anode materials is a limiting constraint.
While silicon-based anodes offer up to 11 times the energy capacity of graphite-based anode materials, they are yet to be widely utilized for practical Li-ion battery applications.
Disadvantages of Pure Silicon-Based Anodes
Silicon has a substantial capacity factor, rendering it a potential candidate material for breaking the upper bound of lithium-ion battery energy density (LIBs). However, pure Si anodes have drawbacks such as low conduction, severe structural changes, and rapid breakdown.
Silicon-based anodes also face unsatisfactory electrocatalytic deterioration since silicon expands by 400% during charge/discharge cycling. This leads to poor initial coulombic performance and cyclic stability, limiting their practical usage in LIBs.
Nanoporous Metals: Advantages for Lithium-ion Battery Applications
Electrode materials with nanoporous architectures have received much attention and success in Li-ion batteries. Compared to standard electrodes, they often exhibit superior electrocatalytic activity, primarily due to their highly porous structure at the nanoscale scale, allowing a decrease in the Li-ion path length between the electrolytes and the electrode.
Because of their distinctive metallic features (large conductance and highly ductile nature) and nanoparticle characteristics (permeability and large surface area), nanoporous metals can efficiently alleviate several difficulties caused by Si volume expansion during cycling.
Previous Studies and Their Limitations
Previous research has concentrated on employing carbon and aluminum as control elements to mechanically mill Si/Ni-Sn composite anode composites, which lowers the intrinsic capacity degradation of Si owing to volume expansion during cycles. These approaches, however, are complex and expensive, making it difficult to accelerate the development of LIBs for large-scale utilization.
A pomegranate-like Si-Ni anode was previously created utilizing a simple one-step burning process. However, during the combustion, the robust reaction mechanism generated an unequal distribution of Si and Ni, leading to poor cycling efficiency.
A Novel Method for Synthesis of Si-Ni Nanofoam Composites
To create Si-Ni nanofoam composites, the researchers adopted a uniform vacuum calcination process in this study. The Si particles can be dispersed evenly in the Ni nanofoam structure. When employed as an anode for LIBs, the composite materials entirely use the Ni nanofoam structure, which offers a well-stabilized architecture and efficiently supports the Si material's volume change.
Field emission scanning electron microscopy examined the geometry and composition of the materials. X-ray diffraction and energy dispersive spectrometry were used to determine the crystalline structure and chemical contents. The electrical and chemical measurements were performed on a multilayer battery analyzer and an electrochemical workbench at ambient temperature.
Key Findings of the Study
Ni nanofoams with a 3D-linked network topology can quickly transfer electrons to active materials and adapt to volume fluctuations. A conductive Ni nanofoam as a composite electrode framework can function similarly to metal mesh in concrete blocks, effectively protecting the electrode structure's integrity after repeated charging and discharging.
After 100 cycles, Si Ni nanofoam composite materials have a high capacity at a current density of 500 mA g-1. Such enhanced cycling performance suggests that nanoporous compounds have tremendous promise for use in Si anode applications and may be applied to other power storage and energy production industries.
Zhu, H. et al. (2022). Si–Ni Nanofoam Composites with a 3D Nanoporous Structure as a High-Loading Lithium-Ion Battery Anode. ACS Applied Energy Materials. Available at: https://pubs.acs.org/doi/10.1021/acsaem.2c00893