Multifunctional Current Collectors

Updated 11 August 2025

Multifunctional current collectors are engineered conductors that enable efficient charge transport while providing secondary functions like mechanical reinforcement and interface stability.
Tailored modifications using metallic alloys, carbon-based substrates, porous architectures, and atomic-level treatments improve electrical performance and mitigate issues such as dendrite formation.
Their integration in energy devices, including batteries, supercapacitors, and optoelectronic systems, drives performance enhancement, sustainability, and structural resilience.

Multifunctional current collectors are engineered conductors that not only serve as charge transport pathways in electrochemical devices (batteries, supercapacitors, and emerging spintronic/optoelectronic platforms) but also impart secondary functionalities including mechanical robustness, interfacial engineering, environmental compatibility, and flow regulation. Contemporary research delineates how compositional, structural, and process modifications transform current collectors into active design elements that influence device performance far beyond simple electrical conduction.

1. Materials, Architectural Diversity, and Enhancement Strategies

Multifunctional current collectors are fabricated from an array of metallic, carbonaceous, and alloyed substrates, subject to intricate physical and chemical modifications that augment both primary (electrical) and auxiliary functionalities.

Metallic Foils and Alloys: Standard collectors (Cu, Al) remain essential due to favorable conductivity, but advances incorporate Li‐alloys (Li–Ag, Li–Si, Li–Zn) and tailored brass via vapor phase dealloying (VPD) (Woods et al., 8 Aug 2025).
Carbon Nanotube (CNT) Fibres and Graphite Paper (GP): CNT fibers serve as both electrode and collector in structural composites, while GP collectors, especially with nano-metallic enhancements, bridge high conductivity with mechanical flexibility (Qu et al., 2015, Rana et al., 2020).
Porous Architectures: Three-dimensional Cu networks and engineered porosity (micron-scale channels) optimize surface area, tortuosity, and ion transport (Lu et al., 2021, Woods et al., 8 Aug 2025).
Atomic Interface Engineering: Ion implantation protocols create oxide-free, defect-rich surfaces conferring oxidation resistance and interface stability (Li et al., 1 Aug 2025).
Direct Reuse and Sustainability: Reclamation protocols for Al and Cu foils from spent batteries leverage chemical washes and etching, altering surface morphology and wettability while supporting circular economies (Zhu et al., 2022).

Material/Process	Electrical Function	Secondary Functionality
Li-alloy (DFT/NEB-screened) (Pande et al., 2019)	High nucleation, low overpotential	Uniform Li plating, higher energy density
CNT fibre composite (Rana et al., 2020)	Conductive, lightweight	Structural integrity, mechanical tolerance
VPD brass (Cu-Zn) (Woods et al., 8 Aug 2025)	Porous, tunable surface Zn	Suppress dendrites, CE control
Nano-metal GP (Qu et al., 2015)	Flexible, thin	Low weight, improved adhesion
Ion-implanted Cu (Li et al., 1 Aug 2025)	Oxide-free, conductive	Stabilized SEI, oxygen trapping
Reclaimed Al/Cu (Zhu et al., 2022)	Reused, modified surfaces	Waste reduction, adhesion tuning

2. Interfacial Engineering and Electrochemical Performance

The collector–electrolyte or collector–electrode interfaces define local nucleation, plating/stripping efficiency, solid electrolyte interphase (SEI) composition, and overall cycle life.

Atomic Interface Cleaning: Ion implantation on Cu foils removes native oxides and introduces subsurface vacancy clusters that “trap” oxygen, preventing reoxidation and creating an atomically clean interface. This enables a thin, Li₂O-rich SEI, uniform lithium deposition, and reduced parasitic reactions (nucleation overpotential ~38.4 mV, 99% CE over 400 cycles) (Li et al., 1 Aug 2025).
Surface Chemistry Control: Zn coating on 3D Cu collectors minimizes nucleation barriers (e.g., reduction from 46.1 mV to 32.5 mV on optimized samples), improves lithium plating uniformity by producing lithophilic surfaces, and increases Coulombic efficiency up to 99.56% (Lu et al., 2021).
Porosity and Compositional Gradients: VPD brass collectors illustrate how higher processing temperatures reduce residual surface Zn and create deeper pores; surface Zn <1 at.% at 800 °C delivers >90% CE, while higher Zn levels (4–8 at.%) at 500 °C foster Li–Zn alloying, dendrite formation, and rapid capacity loss (Woods et al., 8 Aug 2025).
DFT-Screened Collector Surfaces: Li-alloy collectors display adsorption energies near zero and diffusion barriers as low as 0.02 eV (for Li₃Ag(101)), supporting low nucleation overpotentials and rapid lateral growth, ideal for anode-free lithium-metal cells (Pande et al., 2019).

3. Structural Roles: Mechanical, Thermal, and Device Integration

Collectors increasingly double in structural roles, imparting mechanical resilience, damage tolerance, and facilitative integration in advanced cell architectures.

CNT Fibre Composites and Resin Rivets: CNT current collectors integrate seamlessly as both electrical pathways and composite reinforcements, negating the need for metallic foils and providing mechanical tolerance under repeated bending and cycling; resin “rivets” optimize interlaminar shear strength as quantified by finite element modelling (FEA), delivering up to 83% effective EDLC area with minimal loss in shear strength (Rana et al., 2020).
Thin, Flexible Collectors: Graphite paper with nano-metal layers creates >250 μm thick, lightweight, flexible batteries (bendable to 1 cm radius with preserved performance). Adhesion and interfacial yield increase nearly tenfold over bare GP (Qu et al., 2015).

4. Electrical Modelling: Thickness, Tab Geometry, and Resistance Effects

Electrical resistance within the collector system modulates voltage drop, heating, and thus practical power capability—of acute relevance for miniaturized, high-power devices.

Analytical Expressions for Potential Drop: The maximum potential drop (Vmax) scales inversely with collector thickness (d). Analytical expressions: $V_{max} = \frac{\rho L I}{b d}$ , with a logarithmic relation $\ln(V_{max}) = -\ln(d) + C$ confirmed over a range of thicknesses (Campillo-Robles et al., 14 Jan 2025).
Material Choice: For identical geometries, Al exhibits ~60% higher Vmax than Cu due to higher resistivity. Tab position alters resistance: central tabs increase Vmax by 50%, corner tabs by an additional 14% (Campillo-Robles et al., 14 Jan 2025).
Design Implications: Miniaturization reduces weight but dramatically increases ohmic losses below 500 μm thickness; designers must optimize both geometry and material to balance electrical and mechanical requirements.

5. Flow Regulation and Stability in Fluid-Based Energy Devices

In liquid metal batteries, current collector geometry and boundary conditions exert direct control over electrodynamic instabilities and flow phenomena.

Tayler Instability (TI) and Hartmann Number: TI emerges once $\mathrm{Ha}$ exceeds a critical value (~20), with instability structure and growth modified by the collector’s electrical boundary conditions ( $\varphi_i$ ), material conductivity ( $\sigma_{cc}$ ), and geometric extension (Weber et al., 2014).
Electro-Vortex Flows: Radial current components induced by non-uniform collector boundaries drive Lorentz force distributions that initiate axisymmetric and non-axisymmetric electro-vortex flows. Moderate flows enhance mixing (reducing concentration polarization); excessive flows risk electrolyte layer disruption (Weber et al., 2014).
Simulation Methodology: Models couple Navier–Stokes and Biot–Savart integro-differential formulations, with explicit Dirichlet–Neumann partitioning at collector interfaces to resolve radial/axial current diversions.

6. Spintronic, Optoelectronic, and Thermoelectric Multifunctionality

Beyond classical charge transport, current collectors act as dynamic modulators in emerging device paradigms.

Lateral VS₂|MoS₂ Heterojunctions: First-principles calculations combined with Landauer–Büttiker formalism reveal perfect rectifying behavior (rectification ratios >10⁴), spin filtering efficiency (A-type, SP ~94%), and gate-tunable current/rectification in field-effect transistors (An et al., 2020).
Photodetection and Thermospin: Under illumination, both Z-type and A-type VS₂|MoS₂ diodes demonstrate high blue-light photoresponse (photocurrent densities up to 34.2 mA/cm²) and robust thermoelectric current generation under temperature gradients, highlighting applications in photodetectors, photovoltaics, and caloritronic energy harvesting (An et al., 2020).
Multifunctionality: Spin-dependent transport, optoelectronic sensitivity, and thermoelectric conversion position certain heterojunction collectors at the intersection of spintronics, optoelectronics, and energy conversion technologies.

7. Environmental Compatibility and Direct Reuse

Direct reuse strategies for current collectors offer functional sustainability and support circular material flows.

Reclamation Protocols and Surface Morphology: NMP/oxalic acid treatments for Al and sequential water/HCl/HNO₃ cleaning for Cu generate modified surfaces with distinct wettability, adhesion (up to 80 N/m for etched Al), and conductivity. Enhanced roughness improves adhesion but may decrease conductance at high rates (Zhu et al., 2022).
Electrochemical Equivalency: Reclaimed Al and Cu collectors exhibit comparable performance to pristine ones at low C rates; at high C rates, reduced Al contact conductivity warrants caution. Cu collectors display robust performance across treatments (Zhu et al., 2022).
Waste Reduction and Circularity: Given that collectors constitute >15% battery mass, direct reuse bypasses intensive remelting or casting, contributing significantly to waste management in LIBs.

Conclusion

Multifunctional current collectors manifest as critical, actively designed elements in contemporary electrochemical systems. Their complex materiality, interface chemistry, geometry, and integrated roles govern not only electrical conduction but also nucleation phenomena, mechanical tolerance, instability control, device integration, and environmental sustainability. Optimization across these dimensions—guided by empirical, computational, and atomic-scale engineering—is essential for next-generation high-performance, durable, and versatile energy and information devices.