Charge Storage in Ti₃C₂Tₓ for Rechargeable Batteries: Recent Progress and Outlook

Ti₃C₂Tₓ is a representative member of a rapidly growing family of two-dimensional, layered transition-metal carbides, nitrides, and carbonitrides whose electrochemical behavior is defined by three coupled features: (i) a highly conductive metal–carbon backbone, (ii) termination-rich surfaces that govern interfacial chemistry, and (iii) a stackable sheet morphology that creates an interlayer gallery where ions, solvent molecules, and intercalants can reside. Together, these attributes produce a material platform that is fundamentally different from many other 2D solids. Graphene, for example, offers exceptional conductivity and mechanical reinforcement but has a relatively inert basal plane unless defects or heteroatoms are introduced, whereas transition-metal dichalcogenides can provide layered insertion sites but may undergo phase evolution or conversion-type processes depending on voltage window. In contrast, Ti₃C₂Tₓ combines metallic-like transport with intrinsically active, chemically tunable surfaces, allowing electrochemical function to be engineered through termination chemistry, interlayer spacing, and electrode architecture.

These characteristics have enabled Ti₃C₂Tₓ to contribute to multiple battery platforms, including lithium-ion, sodium-ion, lithium sulfur, and zinc-based systems, where its role depends strongly on how it is assembled. In some cases, Ti₃C₂Tₓ acts as the primary charge-storage host and delivers fast, surface-controlled storage with high power capability. In others, it serves as a conductive scaffold that lowers polarization in electrodes built from less conductive active phases, stabilizes microstructure during repeated volume changes, and improves electrolyte wetting through hydrophilic terminations. Ti₃C₂Tₓ has also been used as a reinforcing component in hybrid electrodes, where it maintains electron percolation and reduces mechanical degradation, and as an interfacial modifier on current collectors, where it improves contact resistance and can regulate interphase formation. Across these functions, one of the most central and scientifically informative is its behavior as a charge-storage host material, because this role directly links atomic-scale surface chemistry and gallery structure to device-level capacity, rate capability, and stability.

In this review, I integrate recent progress in Ti₃C₂Tₓ synthesis, processing, and characterization and evaluate, from a mechanistic perspective, how Ti₃C₂Tₓ performs as an active electrode material in divalent-ion batteries. I focus on design approaches that improve reversible capacity, accelerate transport, and extend cycle life under multivalent charge carriers, where strong solvation and electrostatic interactions frequently impose kinetic and structural penalties. I compare the dominant storage pathways in single-phase Ti₃C₂Tₓ with those in composite architectures and heterostructures, where graphene, carbon nanotubes, layered oxides, and other 2D materials are often introduced to prevent restacking, improve conductivity over practical thickness, and stabilize interfaces. Particular attention is given to how storage mechanisms evolve with electrolyte environment and operating window, including the balance between surface-controlled charging, pseudocapacitive redox at termination sites, and interlayer insertion or co-insertion phenomena that can involve solvent or protons in aqueous systems.

Finally, I identify the main limitations that currently constrain practical deployment, including oxidation and moisture sensitivity, termination variability arising from synthesis history, restacking-driven transport losses, and the gap between laboratory-scale materials and scalable manufacturing. I outline research directions where microstructure engineering provides a realistic route to higher-performing divalent-ion storage, emphasizing controllable variables such as interlayer spacing and pillaring, flake size and alignment, defect populations, termination distributions, and engineered interfaces that reduce charge-transfer resistance while suppressing parasitic reactions. By framing Ti₃C₂Tₓ alongside graphene and other established 2D materials, I highlight where Ti₃C₂Tₓ offers unique advantages and where hybrid strategies are likely to be most effective for translating its intrinsic properties into durable, high-performance multivalent batteries.