MXene-based anode materials for high performance sodium-ion batteries

2D/3D hierarchical Zinc@Ti3C2Tx-MXene composite-coated copper foil as dendrite-free lithium host for stable lithium metal batteries

Lithium metal, with its ultrahigh theoretical capacity (3860 mAh g-1) and the lowest redox potential among metallic anodes (-3.04 V vs. SHE), is regarded as the ultimate anode for next-generation high-energy-density batteries. However, rampant dendrite growth and unstable solid electrolyte interphase (SEI) formation critically hinder its practical adoption. Herein, we design a hierarchical 2D/3D Zinc@MXene (Zn@M) composite-coated Cu current collector to stabilize lithium metal anodes. The MXene nanosheets (Ti3C2Tx) function as lithium-philic conductive channels to homogenize Li+ flux, while micrometer-sized Zn particles construct a porous scaffold that mitigates MXene restacking and provides preferential nucleation sites for lithium deposition. Benefiting from the strong interfacial bonding between MXene and Zn, the composite forms a robust dual-phase architecture with enhanced mechanical integrity and ion/electron transport efficiency. This synergy enables dendrite-free Li plating/stripping, as evidenced by the Li||Zn@M half-cell achieving a high average coulombic efficiency of 97.6 % over 450 cycles (1 mA cm-2/1 mAh cm-2) and symmetrical cells sustaining stable operation for 3300 h (1 mA cm-2/1 mAh cm-2). Remarkably, when paired with a high-loading LiFePO4 cathode (12.7 mg cm-2) in anode-free configuration, the Zn@M/Cu current collector demonstrates exceptional full-cell cyclability with 70 % capacity retention after 50 cycles. This work provides a universal interface engineering strategy for realizing dendrite-suppressive lithium hosts, paving the way toward practical high-energy lithium-metal batteries.

Engineering the next generation of MXenes: challenges and strategies for scalable production and enhanced performance

Two-dimensional nanomaterials, such as MXenes, have garnered significant attention due to their excellent properties, including electrical conductivity, mechanical strength, and thermal stability. These properties make them promising candidates for energy storage and catalysis applications. However, several challenges impede their large-scale production and industrial application. Issues such as high production costs, safety concerns related to toxic etching agents, instability in oxidative environments, and the complex synthesis process must be addressed. In this review, we systematically analyze current methodologies for scaling up MXene production, focusing on the synthesis and etching of MAX phases, delamination strategies, and the production of MXene derivatives. We explore strategies for overcoming challenges like aggregation, oxidation, and cost, presenting optimization techniques for enhancing electrochemical performance and stability. The review also discusses the applications of MXenes in batteries and supercapacitors, emphasizing their potential for large-scale use. Finally, we provide an outlook on future research directions for MXene to develop safer and more cost-effective production methods to improve the performance of MXene in order to realize its commercial potential in energy technologies.

Ti3C2T x MXenes as Anodes for Sodium-Ion Batteries: the In Situ Comprehension of the Electrode Reaction

Since their appearance on the scene, MXenes have been recognized as promising anode materials for rechargeable batteries, thanks to the combination of structural and electronic features. The layered structure with a suitable interlayer distance, good electronic conductivity, and moldability in composition makes MXenes exploitable both as active and support materials for the fabrication of nanocomposites providing both capacitive and Faradaic contributions to the final capacity. Although a variety of possibilities has been explored, the fundamental mechanism of the electrode reaction is still hazy. We herein report the investigation of Ti3C2T x MXenes, the benchmark composition for application in energy storage, through the combined operando X-ray absorption spectroscopy (XAS) and Raman analysis supported by density functional theory (DFT) calculations with the aim of clarifying the origin and nature of capacity when the material was cycled vs Na. The electrode reaction determined was Ti3C2X2 + 1Na → Na1Ti3C2X2, defining the theoretical capacity.

Theoretical Investigation of a Novel Two-Dimensional Non-MXene Mo3C2 as a Prospective Anode Material for Li- and Na-Ion Batteries

A new two-dimensional (2D) non-MXene transition metal carbide, Mo3C2, was found using the USPEX code. Comprehensive first-principles calculations show that the Mo3C2 monolayer exhibits thermal, dynamic, and mechanical stability, which can ensure excellent durability in practical applications. The optimized structures of Lix@(3×3)-Mo3C2 (x = 1-36) and Nax@(3×3)-Mo3C2 (x = 1-32) were identified as prospective anode materials. The metallic Mo3C2 sheet exhibits low diffusion barriers of 0.190 eV for Li and 0.118 eV for Na and low average open circuit voltages of 0.31-0.55 V for Li and 0.18-0.48 V for Na. When adsorbing two layers of adatoms, the theoretical energy capacities are 344 and 306 mA h g-1 for Li and Na, respectively, which are comparable to that of commercial graphite. Moreover, the Mo3C2 substrate can maintain structural integrity during the lithiation or sodiation process at high temperature. Considering these features, our proposed Mo3C2 slab is a potential candidate as an anode material for future Li- and Na-ion batteries.

Universal Intercalation/Alloying Hybrid Mechanism with -ICOHP Criterion in MAX Toward Steadily Ascending Lithium-Ion Batteries

Profiting from the unique atomic laminated structure, metallic conductivity, and superior mechanical properties, transition metal carbides and nitrides named MAX phases have shown great potential as anodes in lithium-ion batteries. However, the complexity of MAX configurations poses a challenge. To accelerate such application, a minus integrated crystal orbital Hamilton populations descriptor is innovatively proposed to rapidly evaluate the lithium storage potential of various MAX, along with density functional theory computations. It confirms that surface A-element atoms bound to lithium ions have odds of escaping from MAX. Interestingly, the activated A-element atoms enhance the reversible uptake of lithium ions by MAX anodes through an efficient alloying reaction. As an experimental verification, the charge compensation and SnxLiy phase evolution of designed Zr2SnC MAX with optimized structure is visualized via in situ synchrotron radiation XRD and XAFS technique, which further clarifies the theoretically expected intercalation/alloying hybrid storage mechanism. Notably, Zr2SnC electrodes achieve remarkably 219.8% negative capacity attenuation over 3200 cycles at 1 A g-1. In principle, this work provides a reference for the design and development of advanced MAX electrodes, which is essential to explore diversified applications of the MAX family in specific energy fields.