Lithium-ion batteries, known for their safety, low cost, and excellent performance, are widely used in portable electronic devices, large-scale energy storage systems, electric vehicles, and other fields, making them outstanding secondary energy storage devices.
A typical lithium-ion battery consists of an anode, a cathode, a separator, electrolyte, and current collectors. Common anode materials include LiNiMnCoO₂, LiFePO₄, LiCoO₂, LiMn₂O₄, etc., while graphite is primarily used for the cathode. To improve performance parameters like energy density, cathode graphite is often doped with materials like SiOₓ. Extensive research on materials for lithium-ion batteries is conducted within this context.
Preparation of 3D Porous Copper
Copper foil, with its excellent conductivity and mechanical properties, is currently the preferred choice for the negative electrode current collector in lithium-ion batteries. In recent years, many researchers have also been actively seeking new types of current collectors to accommodate battery development.
The production process for the battery anode involves uniformly coating a prepared slurry of negative electrode active material onto the copper foil surface, followed by drying, rolling, slitting, and other steps to form the final negative electrode product.
Therefore, copper foil must not only meet the performance requirements for conductivity, surface roughness, and glossiness but also satisfy the processing requirements regarding mechanical properties such as tensile strength and elongation. Furthermore, with the application of high-energy-density negative electrode materials like silicon-carbon (SiC), lithium (Li), tin (Sn), and antimony (Sb), additional demands are placed on the copper foil supporting these materials.
In recent years, many researchers have attempted to mitigate and solve issues such as volume changes and dendrite formation in SiC, lithium metal, and other negative electrode materials during cycling from the perspective of the negative electrode current collector copper foil.
Some studies indicate that porous structure copper foil can effectively increase the specific surface area, enhance the contact area between the current collector and the active material, provide buffer space for the expansion and contraction of the negative electrode material, increase adhesion to prevent detachment of the negative electrode material, and thereby improve the battery's cycling performance.
The porous structure can also suppress the formation of lithium dendrites during the charge/discharge cycles of lithium metal, addressing safety concerns arising from dendrite formation.
The preparation method of porous copper foil not only determines properties such as conductivity, lightweight nature, and active material loading capacity of the final product but also whether the method is simple, feasible, employs mature equipment, and is economically viable for production are key factors for achieving mass production.
This paper summarizes the research status of preparation techniques for porous copper current collectors, including template methods, dealloying, powder sintering, chemical methods, and copper mesh weaving, along with their impact on battery performance. It also provides prospects for the future development of 3D porous copper current collectors.
Different preparation methods result in variations in pore form, size, and porosity of the porous copper. Current main preparation methods include: using CO₂ lasers and printed templates to directly create micro-through-holes on copper foil; using processes like hydrogen bubble templates or dextran templates to form foam-like pores; employing dealloying and powder sintering to create irregular pores; weaving copper wires to form mesh pores; and using chemical methods to prepare fibrous skeleton pores on the surface.
Pore form, size, porosity, etc., are significantly influenced by the preparation process, leading to considerable performance differences.
Impact of 3D Porous Copper Current Collectors on Lithium-Ion Battery Performance
In lithium-ion batteries, copper foil acts as both the support structure and current collector for the negative electrode. Its surface activity, electrical conductivity, oxidation resistance, and own weight directly affect battery indicators such as energy density and cycling performance.
With increasing demands on lithium-ion batteries, new negative electrodes like SiC, Sn, and Li metal are being extensively researched, offering theoretical capacities far exceeding graphite. However, the use of these new negatives presents prominent challenges, such as significant volume changes during charge/discharge and susceptibility to lithium dendrite formation.
3D porous copper foil has become one of the approaches to address these issues. Compared to ordinary flat electrolytic copper foil, many studies show that 3D porous copper foil can effectively mitigate volume expansion/contraction problems of negative electrode materials, thereby improving battery energy density and rate capability.
Safety Enhancement
Testing the electrical performance of lithium metal batteries encapsulated with 3D skeleton copper current collectors revealed that batteries with ordinary copper foil experienced short circuits after 400 cycles.
This was due to lithium dendrite formation during cycling, which pierced the separator, causing the short circuit, along with severe voltage hysteresis during cycling. In contrast, lithium metal batteries encapsulated with 3D lithium battery copper foil showed no short circuit occurrence after 600 cycles, indicating significant suppression of lithium dendrites during cycling, avoiding battery short circuits and resulting in more uniform voltage changes.
Therefore, 3D skeleton copper current collectors can effectively solve the lithium dendrite problem in lithium metal batteries, providing a safety guarantee for these batteries.
3D porous copper current collectors can effectively address some key issues arising during the practical application of next-generation lithium-ion battery negative electrode materials, making the industrial application of materials like Li, Sn, and SiC possible. Research on 3D porous copper current collectors is closely related to the performance of negative electrode materials.
Therefore, it is necessary to select preparation methods for 3D porous copper current collectors that are easy to industrialize for specific negative electrode materials. Detailed studies should investigate the influence of process conditions on pore form, pore size of the 3D porous copper current collector, and corresponding battery performance metrics such as energy density, cycling efficiency, and cycle count.
Based on this, complete production equipment should be developed to achieve industrialization of 3D porous copper current collectors. Currently, most research remains at the basic research stage, focusing on whether the prepared 3D porous copper current collectors are effective.
Development Trends and Prospects for 3D Porous Copper Current Collectors
Extensive research proves that porous copper current collectors are one of the important future directions for copper foil current collector development.
Significant research on preparation methods for 3D porous copper current collectors and new negative electrode materials will inevitably drive the evolution of lithium-ion batteries. The preparation process and method determine the specific surface area, mechanical properties, adhesion to negative electrode materials, and negative electrode conductivity of the 3D porous copper current collector.
Existing literature lacks in-depth research on the specific impact of 3D porous copper current collectors on lithium-ion battery performance, and exploration into industrializing corresponding preparation methods needs acceleration. In the future, finding methods with low energy consumption, mature equipment, and easy scalability to produce porous copper foil current collectors with low mass, tunable pore size, high conductivity, and good mechanical properties is a direction for developing new lithium-ion battery negative electrode materials, holding significant importance for enhancing lithium-ion battery performance.
References
China National Knowledge Infrastructure (CNKI)
