Tailoring Nitrogen Terminals on MXene Enables Fast Charging and Stable Cycling Na-Ion Batteries at Low Temperature

Superior sodiophilicity and molecule crowding of crown ether boost the electrochemical performance of all-climate sodium-ion batteries

Sodium-ion batteries (SIBs) as one of the promising alternatives to lithium-ion batteries have achieved remarkable progress in the past. However, the all-climate performance is still very challenging for SIBs. Herein, 15-Crown-5 (15-C-5) is screened as an electrolyte additive from a number of ether molecules theoretically. The good sodiophilicity, high molecule rigidity, and bulky size enable it to reshape the solvation sheath and promote the anion engagement in the solvated structures by molecule crowding. This change also enhances Na-ion transfer, inhibits side reactions, and leads to a thin and robust solid-electrolyte interphase. Furthermore, the electrochemical stability and operating temperature windows of the electrolyte are extended. These profits improve the electrochemical performance of SIBs in all climates, much better than the case without 15-C-5. This improvement is also adopted to μ-Sn, μ-Bi, hard carbon, and MoS2. This work opens a door to prioritize the potential molecules in theory for advanced electrolytes.

Regulating nitrogen/sulfur terminals on 3D porous Ti3C2 MXene with enhanced reaction kinetics toward high-performance alkali metal ion storage

In this paper, we have developed a simple and efficient sulfur-amine chemistry strategy to prepare a three-dimensional (3D) porous Ti3C2Tx composite with large amounts of N and S terminal groups. The well-designed 3D macroporous architecture presents enlarged interlayer spacing, large specific surface area, and unique porous structure, which successfully solves the re-stacking issue of MXene during storage and electrode fabrication. It is the amount of concentrated hydrochloric acid added to the S-EDA (ethylenediamine)/MXene colloidal suspension that is critical to the formation of 3D morphology. In addition, N and S terminals on MXene could improve the adsorption ability of K+. Owing to the synergistic effect of the structure design and terminal modification, the N, S codoped three-dimensional porous Ti3C2Tx (3D-NSPM) material shows a high surface capacitive contribution and rapid diffusion kinetics for K+ and Na+. As a result, the as-prepared 3D-NSPM delivers high reversible capacity (237 and 273 mAh g-1 at 0.1 A g-1 for PIBs and SIBs, respectively), superb cycling stability (84.9% capacity retention after 10,000 cycles at 1 A g-1 in PIBs and 74.0% capacity retention after 2200 cycles at 1 A g-1 in SIBs), and excellent rate capability (111 and 196 mAh g-1 at 5 A g-1 for PIBs and SIBs, respectively), which are superior to other MXene-based anodes for PIBs and SIBs. Moreover, the described strategy provides a new insight for constructing the 3D porous structure from 2D building blocks beyond MXene.

Solvation Effect: The Cornerstone of High-Performance Battery Design for Commercialization-Driven Sodium Batteries

Sodium batteries (SBs) emerge as a potential candidate for large-scale energy storage and have become a hot topic in the past few decades. In the previous researches on electrolyte, designing electrolytes with the solvation theory has been the most promising direction is to improve the electrochemical performance of batteries through solvation theory. In general, the four essential factors for the commercial application of SBs, which are cost, low temperature performance, fast charge performance and safety. The solvent structure has significant impact on commercial applications. But so far, the solvation design of electrolyte and the practical application of sodium batteries have not been comprehensively summarized. This review first clarifies the process of Na+ solvation and the strategies for adjusting Na+ solvation. It is worth noting that the relationship between solvation theory and interface theory is pointed out. The cost, low temperature, fast charging, and safety issues of solvation are systematically summarized. The importance of the de-solvation step in low temperature and fast charging application is emphasized to help select better electrolytes for specific applications. Finally, new insights and potential solutions for electrolytes solvation related to SBs are proposed to stimulate revolutionary electrolyte chemistry for next generation SBs.

Advanced Insights on MXenes: Categories, Properties, Synthesis, and Applications in Alkali Metal Ion Batteries

The development and optimization of promising anode material for next-generation alkali metal ion batteries are significant for clean energy evolution. 2D MXenes have drawn extensive attention in electrochemical energy storage applications, due to their multiple advantages including excellent conductivity, robust mechanical properties, hydrophilicity of its functional terminations, and outstanding electrochemical storage capability. In this review, the categories, properties, and synthesis methods of MXenes are first outlined. Furthermore, the latest research and progress of MXenes and their composites in alkali metal ion storage are also summarized comprehensively. A special emphasis is placed on MXenes and their hybrids, ranging from material design and fabrication to fundamental understanding of the alkali ion storage mechanisms to battery performance optimization strategies. Lastly, the challenges and personal perspectives of the future research of MXenes and their composites for energy storage are presented.

Nitrogen-Doped Graphene-Like Carbon Intercalated MXene Heterostructure Electrodes for Enhanced Sodium- and Lithium-Ion Storage

MXene is investigated as an electrode material for different energy storage systems due to layered structures and metal-like electrical conductivity. Experimental results show MXenes possess excellent cycling performance as anode materials, especially at large current densities. However, the reversible capacity is relatively low, which is a significant barrier to meeting the demands of industrial applications. This work synthesizes N-doped graphene-like carbon (NGC) intercalated Ti3C2Tx (NGC-Ti3C2Tx) van der Waals heterostructure by an in situ method. The as-prepared NGC-Ti3C2Tx van der Waals heterostructure is employed as sodium-ion and lithium-ion battery electrodes. For sodium-ion batteries, a reversible specific capacity of 305 mAh g-1 is achieved at a specific current of 20 mA g-1, 2.3 times higher than that of Ti3C2Tx. For lithium-ion batteries, a reversible capacity of 400 mAh g-1 at a specific current of 20 mA g-1 is 1.5 times higher than that of Ti3C2Tx. Both sodium-ion and lithium-ion batteries made from NGC-Ti3C2Tx shows high cycling stability. The theoretical calculations also verify the remarkable improvement in battery capacity within the NGC-Ti3C2O2 system, attributed to the additional adsorption of working ions at the edge states of NGC. This work offers an innovative way to synthesize a new van der Waals heterostructure and provides a new route to improve the electrochemical performance significantly.

Monolithic Interphase Enables Fast Kinetics for High-Performance Sodium-Ion Batteries at Subzero Temperature

In spite of the competitive performance at room temperature, the development of sodium-ion batteries (SIBs) is still hindered by sluggish electrochemical reaction kinetics and unstable electrode/electrolyte interphase under subzero environments. Herein, a low-concentration electrolyte, consisting of 0.5M NaPF6 dissolving in diethylene glycol dimethyl ether solvent, is proposed for SIBs working at low temperature. Such an electrolyte generates a thin, amorphous, and homogeneous cathode/electrolyte interphase at low temperature. The interphase is monolithic and rich in organic components, reducing the limitation of Na+ migration through inorganic crystals, thereby facilitating the interfacial Na+ dynamics at low temperature. Furthermore, it effectively blocks the unfavorable side reactions between active materials and electrolytes, improving the structural stability. Consequently, Na0.7Li0.03Mg0.03Ni0.27Mn0.6Ti0.07O2//Na and hard carbon//Na cells deliver a high capacity retention of 90.8 % after 900 cycles at 1C, a capacity over 310 mAh g-1 under -30 °C, respectively, showing long-term cycling stability and great rate capability at low temperature.

3D Pathways Enabling Highly-Efficient Lithium Reservoir for Fast-Charging Batteries

Enhancing the mobility of lithium-ions (Li+) through surface engineering is one of major challenges facing fast-charging lithium-ion batteries (LIBs). In case of demanding charging conditions, the use of a conventional artificial graphite (AG) anode leads to an increase in operating temperature and the formation of lithium dendrites on the anode surface. In this study, a biphasic zeolitic imidazolate framework (ZIF)-AG anode, designed strategically and coated with a mesoporous material, is verified to improve the pathways of Li+ and electrons under a high charging current density. In particular, the graphite surface is treated with a coating of a ZIF-8-derived carbon nanoparticles, which addresses sufficient surface porosity, enabling this material to serve as an electrolyte reservoir and facilitate Li+ intercalation. Moreover, the augmentation in specific surface area proves advantageous in reducing the overpotential for interfacial charge transfer reactions. In practical terms, employing a full-cell with the biphasic ZIF-AG anode results in a shorter charging time and improved cycling performance, demonstrating no evidence of Li plating during 300 cycles under 3.0 C-charging and 1.0 C-discharging. The research endeavors to contribute to the progress of anode materials by enhancing their charging capability, aligning with the increasing requirements of the electric vehicle applications.

Challenges and Breakthroughs in Enhancing Temperature Tolerance of Sodium-Ion Batteries

Lithium-based batteries (LBBs) have been highly researched and recognized as a mature electrochemical energy storage (EES) system in recent years. However, their stability and effectiveness are primarily confined to room temperature conditions. At temperatures significantly below 0 °C or above 60 °C, LBBs experience substantial performance degradation. Under such challenging extreme contexts, sodium-ion batteries (SIBs) emerge as a promising complementary technology, distinguished by their fast dynamics at low-temperature regions and superior safety under elevated temperatures. Notably, developing SIBs suitable for wide-temperature usage still presents significant challenges, particularly for specific applications such as electric vehicles, renewable energy storage, and deep-space/polar explorations, which requires a thorough understanding of how SIBs perform under different temperature conditions. By reviewing the development of wide-temperature SIBs, the influence of temperature on the parameters related to battery performance, such as reaction constant, charge transfer resistance, etc., is systematically and comprehensively analyzed. The review emphasizes challenges encountered by SIBs in both low and high temperatures while exploring recent advancements in SIB materials, specifically focusing on strategies to enhance battery performance across diverse temperature ranges. Overall, insights gained from these studies will drive the development of SIBs that can handle the challenges posed by diverse and harsh climates.

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

As an emerging class of layered transition metal carbides/nitrides/carbon-nitrides, MXenes have been one of the most investigated anode subcategories for sodium ion batteries (SIBs), due to their unique layered structure, metal-like conductivity, large specific surface area and tunable surface groups. In particular, different MAX precursors and synthetic routes will lead to MXenes with different structural and electrochemical properties, which actually gives MXenes unlimited scope for development. In this feature article, we systematically present the recent advances in the methods and synthetic routes of MXenes, together with their impact on the properties of MXenes and also the advantages and disadvantages. Subsequently, the sodium storage mechanisms of MXenes are summarized, as well as the recent research progress and strategies to improve the sodium storage performance. Finally, the main challenges currently facing MXenes and the opportunities in improving the performance of SIBs are pointed out.

Copper Phosphide Nanostructures Covalently Modified Ti3 C2 Tx for Fast Lithium-Ion Storage by Enhanced Kinetics and Pesudocapacitance

2D layer Ti3 C2 Tx material attracts enormous attention in lithium ion energy storage field owing to the unique surface chemistry properties, but the material still suffers from restacking issue and the restriction on capacity. Herein, copper phosphide (Cu3 P) nanostructures@Ti3 C2 Tx composites are prepared by the in situ generation of Cu-BDC precursor in the bulk material followed with phosphorization. The uniformly distributed copper phosphide nanostructures effectively expand the interlayer spacing promoting the structural stability, and achieves the effective connection with the bulk material accelerating the diffusion and migration of lithium ions. The electrochemical activity of Cu3 P also provides more lithium ion active sites for lithium storage. The X-ray photoelectron spectroscopy (XPS) analysis verifies that Ti─O─P bond with strong covalency allows the upper shift of maximum valence band and Fermi level, stimulating the charge transportation between Cu3 P and the bulk Ti3 C2 Tx for better electrode kinetics. 3Cu3 P@Ti3 C2 Tx exhibits excellent rate performance of 165.4 mAh g-1 at 3000 mA g-1 and the assembled 3Cu3 P@Ti3 C2 Tx //AC Lithium-ion hybrid capacitorsLIC exhibits superior energy density of 93.0 Wh kg-1 at the power density of 2367.3 W kg-1 . The results suggest that the interfacial modification of Ti3 C2 Tx with transition metal phosphides will be advantageous to its high energy density application in lithium-ion storage.

Surface Decoration of TiC Nanocrystals onto the Graphite Anode Enables Fast-Charging Lithium-Ion Batteries

To significantly reduce the charging time of commercial lithium-ion batteries (LIBs), it is essential to control the surface properties of graphite anodes because the charging process involves sluggish interfacial kinetics between graphite and the electrolyte. For the effective surface modification of graphite, herein we demonstrate the surface decoration with titanium carbide (TiC) nanocrystals onto graphite particles via a simple wet-coating process. The high electrical conductivity, low Li+ adsorption energy, and small surface diffusion barrier of the TiC nanocrystals facilitate fast Li+ adsorption and migration in the graphite surface by reducing the overpotential upon the charging process. The feasibility of the TiC nanocrystal-decorated graphite (TiC@AG) anode is thoroughly examined with an in-depth understanding of the interfacial reaction mechanism. Furthermore, the full-cell with a commercial cathode (LiNi0.8Co0.1Mn0.1O2) and TiC@AG anode demonstrates an impressive capacity retention (94.5%) after 300 cycles under fast-charging condition (3 C-charging and 1 C-discharging) without any sign of Li plating. The charging time of the TiC@AG full-cell was estimated at 16.2 min (80% of state of charge), which is substantially shorter than that of the artificial graphite full-cell. Our findings offer practical insights into the design principles of advanced graphite anodes, contributing to the realization of fast-charging LIBs.

Spin-Polarized Surface Capacitance Effects Enable Fe3 O4 Anode Superior Wide Operation-Temperature Sodium Storage

Fe3 O4 is widely investigated as an anode for ambient sodium-ion batteries (SIBs), but its electrochemical properties in the wide operation-temperature range have rarely been studied. Herein, the Fe3 O4 nanoparticles, which are well encapsulated by carbon nanolayers, are uniformly dispersed on the graphene basal plane (named Fe3 O4 /C@G) to be used as the anode for SIBs. The existence of graphene can reduce the size of Fe3 O4 /C nanoparticles from 150 to 80 nm and greatly boost charge transport capability of electrode, resulting in an obvious size decrease of superparamagnetic Fe nanoparticles generated from the conversion reaction from 5 to 2 nm. Importantly, the ultra-small superparamagnetic Fe nanoparticles (≈2 nm) can induce a strong spin-polarized surface capacitance effect at operating temperatures ranging from -40 to 60 °C, thus achieving highly efficient Na-ion transport and storage in a wide operation-temperature range. Consequently, the Fe3 O4 /C@G anode shows high capacity, excellent fast-charging capability, and cycling stability ranging from -40 to 60 °C in half/full cells. This work demonstrates the viability of Fe3 O4 as anode for wide operation-temperature SIBs and reveals that spin-polarized surface capacitance effects can promote Na-ion storage over a wide operation temperature range.

N-Terminalized Ti3 C2 Tx MXene for Supercapacitor with Extraordinary Pseudocapacitance Performance

MXenes have demonstrated significant potential in electrochemical energy storage, particularly in supercapacitors, owing to their exceptional properties. The surface terminal groups of MXene play a pivotal role in pseudocapacitive mechanism. Considering the hindered electrolyte ion transport caused by -F terminal groups and the limited ion binding sites associated with -O terminal groups, this study proposes a novel strategy of replacing -F with -N terminal groups. The modulated MXene-N electrode, featuring a substantial number of -N terminal groups, demonstrates an exceptionally high gravimetric capacitance of 566 F g-1 (at a scan rate of 2 mV s-1 ) or 588 F g-1 (at a discharge rate of 1 A g-1 ) in 1 м H2 SO4 electrolyte, and the potential window is significantly increased. Furthermore, subsequent spectra analysis and density functional theory calculations are employed to investigate the mechanism associated with -N terminal groups. This work exemplifies the significance of terminal modulation in the context of electrochemical energy storage.

Enhanced TiO2/SiCx Active Layer Formed In Situ on Coal Gangue/Ti3C2 MXene Electrocatalyst as Catalytic Integrated Units for Efficient Li-O2 Batteries

The pursuit of efficient cathode catalysts to improve cycle stability at ultra-high rates plays an important role in boosting the practical utilization of Li-O2 batteries. Featured as industrial solid waste, coal gangue with rich electrochemical active components could be a promising candidate for electrocatalysts. Here, a coal gangue/Ti3C2 MXene hybrid with a TiO2/SiCx active layer is synthesized and applied as a cathode catalyst in Li-O2 batteries. The coal gangue/Ti3C2 MXene hybrid has a tailored amorphous/crystalline heterostructure, enhanced active TiO2 termination, and a stable SiCx protective layer; thereby, it achieved an excellent rate stability. The Li-O2 battery, assembled with a coal gangue/Ti3C2 MXene cathode catalyst, was found to obtain a competitive full discharge capacity of 3959 mAh g-1 and a considerable long-term endurance of 180 h (up to 175 cycles), with a stable voltage polarization of 1.72 V at 2500 mA g-1. Comprehensive characterization measurements (SEM, TEM, XPS, etc.) were applied; an in-depth analysis was conducted to reveal the critical role of TiO2/SiCX active units in regulating the micro-chemical constitution and the enhanced synergistic effect between coal gangue and Ti3C2 MXene. This work could provide considerable insights into the rational design of catalysts derived from solid waste gangue for high-rate Li-O2 batteries.

Hierarchically Structured Nb2O5 Microflowers with Enhanced Capacity and Fast-Charging Capability for Flexible Planar Sodium Ion Micro-Supercapacitors

Highlights

Hierarchically structured Nb2O5 microflowers consiste of porous and ultrathin nanosheets. Nb2O5 microflowers exhibit enhanced capacity and rate performance boosting Na ion storage. Planar NIMSCs with charge and kinetics matching show superior areal capacitance and lifespan.

Abstract

Planar Na ion micro-supercapacitors (NIMSCs) that offer both high energy density and power density are deemed to a promising class of miniaturized power sources for wearable and portable microelectronics. Nevertheless, the development of NIMSCs are hugely impeded by the low capacity and sluggish Na ion kinetics in the negative electrode. Herein, we demonstrate a novel carbon-coated Nb2O5 microflower with a hierarchical structure composed of vertically intercrossed and porous nanosheets, boosting Na ion storage performance. The unique structural merits, including uniform carbon coating, ultrathin nanosheets and abundant pores, endow the Nb2O5 microflower with highly reversible Na ion storage capacity of 245 mAh g−1 at 0.25 C and excellent rate capability. Benefiting from high capacity and fast charging of Nb2O5 microflower, the planar NIMSCs consisted of Nb2O5 negative electrode and activated carbon positive electrode deliver high areal energy density of 60.7 μWh cm−2, considerable voltage window of 3.5 V and extraordinary cyclability. Therefore, this work exploits a structural design strategy towards electrode materials for application in NIMSCs, holding great promise for flexible microelectronics.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40820-023-01281-5.

Interface Engineering of Fe7S8/FeS2 Heterostructure in situ Encapsulated into Nitrogen-Doped Carbon Nanotubes for High Power Sodium-Ion Batteries

Heterostructure engineering combined with carbonaceous materials shows great promise toward promoting sluggish kinetics, improving electronic conductivity, and mitigating the huge expansion of transition metal sulfide electrodes for high-performance sodium storage. Herein, the iron sulfide-based heterostructures in situ hybridized with nitrogen-doped carbon nanotubes (Fe7S8/FeS2/NCNT) have been prepared through a successive pyrolysis and sulfidation approach. The Fe7S8/FeS2/NCNT heterostructure delivered a high reversible capacity of 403.2 mAh g-1 up to 100 cycles at 1.0 A g-1 and superior rate capability (273.4 mAh g-1 at 20.0 A g-1) in ester-based electrolyte. Meanwhile, the electrodes also demonstrated long-term cycling stability (466.7 mAh g-1 after 1,000 cycles at 5.0 A g-1) and outstanding rate capability (536.5 mAh g-1 at 20.0 A g-1) in ether-based electrolyte. This outstanding performance could be mainly attributed to the fast sodium-ion diffusion kinetics, high capacitive contribution, and convenient interfacial dynamics in ether-based electrolyte.

Zinc Single-Atom-Regulated Hard Carbons for High-Rate and Low-Temperature Sodium-Ion Batteries

Hard carbons, as one of the most commercializable anode materials for sodium-ion batteries (SIBs), have to deal with the trade-off between the rate capability and specific capacity or initial Columbic efficiency (ICE), and the fast performance decline at low temperature (LT) remains poorly understood. Here, a comprehensive regulation on the interfacial/bulk electrochemistry of hard carbons through atomic Zn doping is reported, which demonstrates a record-high reversible capacity (546 mAh g^-1 ), decent ICE (84%), remarkable rate capability (140 mAh g^-1 @ 50 A g^-1 ), and excellent LT capacity (443 mAh g^-1 @ -40 °C), outperforming the state-of-the-art literature. This work reveals that the Zn doping can generally induce a local electric field to enable fast bulk Na⁺ transportation, and meanwhile catalyze the decomposition of NaPF₆ to form a robust inorganic-rich solid-electrolyte interphase, which elaborates the underlying origin of the boosted electrochemical performance. Importantly, distinguished from room temperature, the intrinsic Na⁺ migration/desolvation ability of the electrolyte is disclosed to be the crucial rate-determining factors for the SIB performance at LT. This work provides a fundamental understanding on the charge-storage kinetics at varied temperatures.