Theoretical Specific Capacity Research Articles

Prediction of Halogenated MXenes as Electrode Materials for Halide-Ion Batteries.

Exploring and developing new rechargeable halide-ion batteries plays an important role in the advancement and growth of the ion battery family. Here, we systematically explored the feasibility of single-layer MXenes and their hydrogenated derivatives as electrode materials for halide-ion batteries via first-principles theory. The calculated results indicate that halide ions (T ions) can be stably and efficiently adsorbed on the surfaces of M2X and M2XH2, with theoretical specific capacities ranging from 227 to 497 mAh g-1. The diffusion barriers of the T ion on MXenes are from 0.55 to 0.10 eV, comparable to those of the Li ion in graphite and LiCoO2. The electronegativity of halide anions displays significant impacts on their discharge voltage plateaus on M2X, with the highest voltage up to 5.60 V for the F ion. As a comparison, the hydrogenation of M2XH2 with less surface activity raises a 2-3 V voltage reduction. All MXene-based full cells of TxTi2C|TyTi2CH2 (where x = 0-2 and y = 2-0) and TxTi2N|TyTi2NH2 (where x = 0-2 and y = 2-0) demonstrated high full battery specific energies for F-, Cl-, and Br-ion batteries, up to 462 Wh kg-1. These results demonstrate the potential of new halide-ion battery designs, paving the way for future research and innovation in battery technology.

Formation mechanisms of multiple Si/graphene nanocomposites through underwater pulsed discharge using different wire arrangements

Si/graphene nanocomposite is regarded as an advanced lithium-ion anode material, attributable to its advantageous microstructure and exceptionally high theoretical specific capacity. This study demonstrates a novel approach for the preparation of Si/graphene nanocomposites, achieved through the pulsed discharge method employing graphite and Si strips as precursors. We devised two distinct “one-step” synthetic routes through pulsed discharge of different wire arrangements. The characterization results of the obtained samples unveiled the presence of Si/graphene composite and Si@carbon layer composite. In addition, the formation mechanisms of Si/graphene nanocomposites have been proposed, different wire arrangements lead to the different energy deposition processes, inducing different robust mechanical and thermal effects on the products. The formed Si clusters either deposit on the surface of exfoliated graphene or become encapsulated within curling graphitic layers, forming a core@shell structure. This work not only presents a straightforward and innovative approach for synthesizing Si/graphene nanocomposites but also contributes valuable insights into the underlying mechanisms governing their formation.

Advancing Anode Performance in Aqueous Zinc-Ion Batteries: A Review of Metal-Organic Framework-Based Strategies.

Aqueous zinc-ion batteries (AZIBs) are garnering substantial research interest in electric vehicles, energy storage systems, and portable electronics, primarily for the reason that the inexpensive cost, high theoretical specific capacity, and environmental sustainability of zinc metal anodes, which are an essential component to their design. Nonetheless, the progress of AZIBs is hindered by significant obstacles, such as the occurrence of anodic side reactions (SR) and the formation of zinc dendrites. Metal-organic framework (MOF)-based materials are being explored as promising alternatives owing to homogeneous porous structure and large specific surface areas. There has been a rare overview and discussion on strategies for protecting anodes using MOF-based materials. This review specifically aims to investigate cutting-edge strategies for the design of highly stable MOF-based anodes in AZIBs. Firstly, the mechanisms of dendrites and SR are summarized. Secondly, the recent advances in MOF-based anodic protection including those of pristine MOFs, MOF composites, and MOF derivatives are reviewed. Furthermore, the strategies involving MOF-based materials for zinc anode stabilization are presented, including the engineering of surface coatings, three-dimensional zinc structures, artificial solid electrolyte interfaces, separators, and electrolytes. Finally, the ongoing challenges and prospective directions for further enhancement of MOF-based anodic protection technologies in AZIBs are highlighted.

Gradient Lithium Ion Regulation Current Collectors for High-Performance and Dendrite-Free Li Metal Batteries.

Lithium metal anode has attracted wide attention due to its ultrahigh theoretical specific capacity, lowest reduction potential, and low density. However, uncontrollable dendritic growth and volume change caused by uneven Li+ deposition still seriously hinder the large-scale commercial application of lithium metal batteries, even causing serious battery explosions and other safety problems. Hence, gold nanoparticles with a gradient distribution anchored on 3D carbon fiber paper (CP) current collectors followed by the encapsulation of polydopamine (PDA) (CP/Au/PDA) are constructed for stable and dendrite-free Li metal anodes for the first time. Significantly, lithiophilic Au nanoparticles showing a gradient distribution in the carbon fiber paper could guide the transfer of Li+ from the outside to the inside of the CP/Au/PDA electrode as well as lower the nucleation overpotential of Li, thereby obtaining the uniform Li deposition. Meanwhile, the PDA layer could in situ be converted to Li-PDA which could serve as an efficient Li+ conductor to further facilitate uniform Li+ transport among the whole CP/Au/PDA electrode. Besides, 3D carbon fiber paper could effectively accommodate the volume change during the plating/stripping process of Li metal. As a result, CP/Au/PDA electrodes deliver a low nucleation overpotential (∼9 mV) and a high Coulombic efficiency (mean value of ∼98.8%) at a current density of 1 mA cm-2 with the capacity of 1 mA h cm-2. Furthermore, Li@CP/Au/PDA electrodes also can demonstrate an ultralow voltage hysteresis (∼20 mV) and a long cycle life (1000 h) in symmetric cells. Finally, with LiFePO4 (LFP) as the cathode, the Li@CP/Au/PDA-LFP full cell delivers a high discharge capacity of 136 mA h g-1 even after 350 cycles at 1C, exhibiting a per cycle loss as low as 0.01%. This gradient lithium ion regulation current collector is of great significance for the development of lithium metal anodes.

Interface-reinforced high-capacity fiber cathode for wearable Li-S batteries

Abstract Fiber-shaped Li-S batteries are attractive for constructing smart textiles as flexible power solutions due to their high theoretical specific capacity, flexibility, and wearability. However, severe interfacial issues, such as the shuttle effect of polysulfides on the cathode side, lead to capacity decay and poor lifespan of the batteries. Herein, we report a fiber-shaped composite cathode with collaborative interface interactions to maintain electrode integrity and boost electrochemical performance. In this architecture, nanosulfur-polyvinylpyrrolidone (nanoS-PVP) particles are uniformly implanted into the few-layer Ti3C2Tx with outstanding electrical conductivity and then coated on aluminum (Al) fiber current collectors. Impressively, nanoS and soluble polysulfides are restricted to the cathode side via synergy physical confinement and chemical adsorption of Ti3C2Tx. The PVP chains on the surface of nanoS prevent the sulfur from agglomeration and bridge the Ti3C2Tx by abundant hydrogen bonds. The enhanced interface endows the cathode with excellent mechanical flexibility, good adsorption of polysulfides, and fast reaction kinetics. Consequently, the prepared Ti3C2Tx/nanoS-PVP@Al cathode exhibits excellent cycling performance (capacity retention of 92.8% after 1000 cycles at 1 C), high-rate capacity (556.2 mAh g−1 at 2.0 C), and high linear capacity (22.9 mAh m−1). Additionally, the fiber-shaped Li-S battery works effectively under deformation and high/low-temperature conditions. It can be integrated into the fabric to power LEDs or charge a smartphone wirelessly.

Poly(ethylene) Oxide Electrolytes for All-Solid-State Lithium Batteries Using Microsized Silicon/Carbon Anodes with Enhanced Rate Capability and Cyclability.

Silicon (Si) has been widely studied as one of the promising anodes for lithium-ion batteries (LIBs) because of its ultrahigh theoretical specific capacity and low working voltage. However, the poor interfacial stability of silicon against conventional liquid electrolytes has largely impeded its practical use. Therefore, the combination of silicon-based anodes and solid electrolytes has attracted a great deal of attention in recent years. Here, we demonstrate three types of microsized porous silicon/carbon (Si/C) electrodes (i.e., pristine, prelithiated by liquid electrolyte, and preinfiltrated by polymer electrolyte) that are paired with poly(ethylene) oxide (PEO)-based electrolytes for all-solid-state lithium batteries (ASSLBs). We found that when compared with ionic conductivity, the mechanical stability of the PEO electrolyte dominates the electrochemical performance of ASSLBs using Si/C electrodes at elevated temperature. Additionally, both prelithiated and preinfiltrated Si/C electrodes show higher specific capacity in comparison to the pristine electrode, which is attributed to continuous lithium-ion conducting pathways within the electrode and thus improved utilization of active material. Moreover, owing to good interfacial lithium-ion transport in the electrode, a solid-state half-cell with preinfiltrated Si/C electrode and PEO-lithium bis (trifluoromethanesulfonyl)imide electrolyte delivers a specific capacity of ∼1,000 mAh g-1 after 100 cycles under 800 mA g-1 at 60 °C with average Coulombic efficiency >98.9%. This work provides a strategy for rationally designing the microstructure of silicon-based electrodes with solid electrolytes for high-performance all-solid-state lithium batteries.

Electrolytes for Aluminum-Ion Batteries: Progress and Outlook.

Aluminum-ion batteries (AIBs), as electrochemical energy storage technologies, are advantageous because of their high theoretical specific capacity, lightweightness, zero pollution, safety, inexpensiveness, and abundant resources, which make them recent research hot spots. However, their electrolyte issues significantly limit their commercialization. The electrolyte choices for AIBs are significantly limited, and most of the available choices do not facilitate the three-electron-transfer reaction of Al3+/Al. Thus, this review presents an overview of recent advances in electrolytes, as well as modification strategies for AIBs, to clarify the limitations of existing AIB electrolytes and offer guidance for improving their performances. Furthermore, the advantages as well as limitations and possible solutions for each electrolyte are discussed, after which the future of AIB electrolytes is envisioned.

Design of Coatings for Sulfur-Based Cathode Materials in Lithium-Sulfur Batteries: A review.

Lithium-sulfur batteries (LSBs) are considered next-generation energy storage and conversion solutions owing to their high theoretical specific capacity and the high abundance/low-cost of sulfur-based cathode materials. However, LSBs still encounter significant challenges, including the low conductivities of sulfur-based materials, severe volumetric expansion of sulfur during the discharge process, and the persistent "shuttle effect" of polysulfides. In recent years, a tremendous amount of research has been conducted to address the above challenges by developing coating and compositing materials and corresponding fabrication strategies for sulfur-based cathode materials. In this study, the surface coating, compositing materials, and fabrication methodologies of LSB cathodes are comprehensively reviewed in terms of advanced materials, structure/component characterization, functional mechanisms, and performance validation. Some technical challenges are analyzed in detail, and possible future research directions are proposed to overcome the challenges toward practical applications of lithium-sulfur batteries.

Improving cycling performance of the NaNiO2 cathode in sodium-ion batteries by titanium substitution

O3-type layered oxide cathodes, such as NaNi0.5Mn0.5O2, have garnered significant attention due to their high theoretical specific capacity while using abundant and low-cost sodium as intercalation species. Unlike the lithium analog (LiNiO2), NaNiO2 (NNO) exhibits poor electrochemical performance resulting from structural instability and inferior Coulomb efficiency. To enhance its cyclability for practical application, NNO was modified by titanium substitution to yield the O3-type NaNi0.9Ti0.1O2 (NNTO), which was successfully synthesized for the first time via a solid-state reaction. The mechanism behind its superior performance in comparison to that of similar materials is examined in detail using a variety of characterization techniques. NNTO delivers a specific discharge capacity of ∼190 mAh g−1 and exhibits good reversibility, even in the presence of multiple phase transitions during cycling in a potential window of 2.0‒4.2 V vs. Na+/Na. This behavior can be attributed to the substituent, which helps maintain a larger interslab distance in the Na-deficient phases and to mitigate Jahn–Teller activity by reducing the average oxidation state of nickel. However, volume collapse at high potentials and irreversible lattice oxygen loss are still detrimental to the NNTO. Nevertheless, the performance can be further enhanced through coating and doping strategies. This not only positions NNTO as a promising next-generation cathode material, but also serves as inspiration for future research directions in the field of high-energy-density Na-ion batteries.

A Review of Electrospun Carbon-based Nanofibers Materials Used in Lithium-Sulfur Batteries.

Commercial lithium-ion batteries are gradually approaching their theoretical values (200-250 Wh kg-1), which cannot meet the fast-growing energy storage demands. Lithium-sulfur (Li-S) batteries are anticipated to supersede lithium-ion batteries as the next-generation energy storage system owing to their high theoretical specific capacity (1675 mAh g-1) and energy density (2600 Wh kg-1). Nonetheless, Li-S batteries encounter several challenges, including the inadequate conductivity of sulfur and lithium sulfide, sulfur's volume expansion, and the shuttle effect of lithium polysulfides, all of which significantly impact the practical utilization of Li-S batteries. Electrospun carbon-based nanofibers can simultaneously resolve these issues with their economical preparation, distinctive nanostructure, and exceptional flexibility. This review presents the most recent research findings on electrospun carbon-based nanofibers materials serving as sulfur hosts and interlayer components in Li-S batteries. We analyzed the impact of the material's structural design on the performance of Li-S batteries and the relative underlying mechanism. Finally, the current challenges and issues faced by carbon-based nanofibers composites in the application of Li-S batteries are summarized, and the future development trajectory are outlined.

Promoting polysulfides conversion by hexagonal-like V-MOF-derived VC-doped carbon nanotubes for lithium-sulfur batteries

Lithium-sulfur batteries (LSBs) are one of the representatives of a new generation of high-performance batteries, due to their large theoretical specific discharge capacity, high energy density and low cost et al. However, shuttle effect and slow conversion kinetics of polysulfides (LiPSs) hinder the performance of LSBs. In order to mitigate shuttle effect, metal-organic frameworks are introduced. Carbon nanotubes (CNTs) is used as composite cathode, due to their high electrical conductivity. V-MOF/CNTs-derived hexagonal VC/CNTs nanosheets are successfully synthesized and used as the sulfur host. VC/CNTs nanosheet with mesoporous structure can provide a lot of active sites. VC nanosheets are uniformly distributed and interconnected with CNTs to form a conductive network structure. VC/CNTs has excellent chemical adsorption and catalytic properties on polysulfides, which can improve the redox reaction kinetics and the adsorption capability. Due to the synergistic effects, S/VC/CNTs has an excellent cycling stability. S/VC/CNTs shows a significant initial specific capacity of 1370 mAh g-1 at 0.1C. Capacity decay rate per cycle is about 0.037% After 500 cycles at 0.5C, the Coulomb efficiency is nearly to 100%. The results show that the introduction of VC/CNTs composites with special hexagonal structure can accelerate the catalytic electrochemical reaction, and the dissolution and diffusion of polysulfides are well controlled.

Advanced Separator Materials for Enhanced Electrochemical Performance of Lithium-Sulfur Batteries: Progress and Prospects.

Lithium-sulfur (Li-S) batteries are promising energy storage devices owing to their high theoretical specific capacity and energy density. However, several challenges, including volume expansion, slow reaction kinetics, polysulfide shuttle effect and lithium dendrite formation, hinder their commercialization. Separators are a key component of Li-S batteries. Traditional separators, made of polypropylene and polyethylene, have certain limitations that should be addressed. Therefore, this review discusses the basic properties and mechanisms of Li-S battery separators, focuses on preparing different functionalized separators to mitigate the shuttle effect of polysulfides. This review also introduces future research trends, emphasizing the potential of separator functionalization in advancing the Li-S battery technology.

Experimental and theoretical investigation of silicon-based carbon composite electrode for high performance Li-ion capacitors

Lithium-ion capacitors (LICs) have garnered significant attention in recent years due to their ability to overcome the shortcomings of lithium-ion batteries (LIBs) and supercapacitors (SCs). Silicon (Si) stands out as a superior anode material for LICs due to its compelling attributes, including a high theoretical specific capacity (4200 mAh/g) and a low de-lithiation potential. Nevertheless, the inherent challenges of Si, such as low electrical conductivity and significant volume expansion (300 %), contribute to low electrochemical performance. To address this issue, a conductive carbon layer is introduced on Si using a simple and scalable approach. The resulting architecture, known as carbon-encapsulated Si (Si/C), not only improves electrical properties by enhancing Li+ diffusion but also mitigates volume expansion, leading to enhanced capacity and cyclic stability. Theoretical findings based on density functional theory (DFT) support these enhancements, confirming improved interactive properties at an atomic scale, including low binding energy and accelerated charge transfer kinetics (higher valence charge transfer) between the Si/C electrode and Li ions. As a result, the ‘binder-free’ and flexible Si/C electrode exhibits a notable initial discharge capacity (3450 mAh/g at 0.05 C) with improved rate capability (3010 mAh/g at 0.1 C). When employed as an anode in LICs, the Si/C electrode exhibits outstanding performance, boasting a large energy density (222.29 Wh/kg), high power density (25 kW/kg), and superior cyclic stability (81.3 % over 10,000 cycles). These findings highlight the potential of the Si/C electrode as a formidable candidate for advanced energy storage applications.

Bond-Engineered MoSe2 Nanosheets with Expanded Layers and an Enriched 1T Phase for Highly Efficient Na+ Storage.

MoSe2 has attracted significant interest for Na+ storage due to its large interlayer distance, favorable band gap structure, and satisfying theoretical specific capacity. Nevertheless, the poor conductivity and large volume stress/strain always lead to poor cycle stability and limited rate capability. Herein, the P-Se bond and phase engineering strategies are proposed to enhance the stability of MoSe2 with the assistance of carbon compositing. Systematical characterizations confirm that the presence of a strong P-Se bond can ensure the good structural stability and enlarge the layer distance of the MoSe2 anode. 1T phase-enriched composition endows excellent conductivity and thus fast Na+ transport kinetics. Additionally, the combination of carbon contributes to the improvement of electron conductivity, further enhancing the reversible Na+ storage and cyclic stability. Consequently, an ultrastable reversible specific capacity of 347.8 mAh g-1 with a high retention ratio of 99.1% can be maintained after 1000 cycles at 1 A g-1, which is superior to the previous reports of MoSe2 nanosheets. The presented strategy is ingenious, offering an effective guidance to designing advanced electrodes to be applied in rechargeable batteries with a long lifespan.

Interfacial engineering in SnO2-embedded graphene anode materials for high performance lithium-ion batteries

Tin dioxide is regarded as an alternative anode material rather than graphite due to its high theoretical specific capacity. Modification with carbon is a typical strategy to mitigate the volume expansion effect of SnO2 during the charge process. Strengthening the interface bonding is crucial for improving the electrochemical performance of SnO2/C composites. Here, SnO2-embedded reduced graphene oxide (rGO) composite with a low graphene content of approximately 5 wt.% was in situ synthesized via a cetyltrimethylammonium bromide (CTAB)-assisted hydrothermal method. The structural integrity of the SnO2/rGO composite is significantly improved by optimizing the Sn–O–C electronic structure with CTAB, resulting a reversible capacity of 598 mAh g−1 after 200 cycles at a current density of 1 A g−1. CTAB-assisted synthesis enhances the rate performance and cyclic stability of tin dioxide/graphene composites, and boosts their application as the anode materials for the next-generation lithium-ion batteries.

Strain effect on TaSe2/Te2 monolayer as adsorption substrate in lithium–sulfur battery

Lithium-sulfur (Li–S) batteries, with their high theoretical specific capacity and energy density, are considered a promising alternative to current energy storage technologies. However, their practical application is hindered by the polysulfide shuttle effect, which leads to capacity fade and reduced coulombic efficiency. In this study we employs density functional theory (DFT) to explore the use of two-dimensional (2D) metallic transition metal dichalcogenides (TMDs), tantalum diselenide (TaSe2) and tantalum ditelluride (TaTe2), as anchoring materials for lithium polysulfides (LiPSs). Our findings reveal that these TMD monolayers exhibit a balanced binding affinity towards LiPSs, ranging from 1.20ev to 3.34eV (TaSe2) and from 2.35ev to 3.74eV (TaTe2). Notably, the decomposition barriers for Li2S on TaSe2 and TaTe2 are significantly lower than those of bulk Li2S with a value of 1.62eV and 1.54eV, suggesting these materials can facilitate rapid charge-discharge processes. The introduction of strain, simulating the expansion during lithiation, demonstrates that these monolayers maintain their adsorption capabilities, a crucial attribute for practical applications, with a increased decomposition barriers of 2.4eV(TaSe2) and 2.51eV(TaTe2). The catalytic activity of these monolayers for the sulfur reduction reaction (SRR) was evaluated, showing a spontaneous conversion mechanism for lithium-sulfur clusters, which is expected to enhance the overall performance of Li–S batteries. This study presents TaSe2 and TaTe2 as innovative and promising candidates for advanced Li–S battery applications, offering a perspective in addressing the critical challenges associated with the polysulfide shuttle effect.

Ultrahigh Potassium Storage Capacity of Ca2Si Monolayer with Orderly Multilayered Growth Mechanism.

As the rising renewable energy demands and lithium scarcity, developing high-capacity anode materials to improve the energy density of potassium-based batteries (PBBs) is increasingly crucial. In this work, a unique orderly multilayered growth (OMLG) mechanism on a 2D-Ca2Si monolayer is theoretically demonstrated for potassium storage by first-principles calculations. The global-energy-minimum Ca2Si monolayer is a semiconductor with isotropic mechanical properties and remarkable electrochemical properties, such as a low potassium ion migration energy barrier of 0.07eV and a low open circuit voltage ranging from 0.224 to 0.003V. Most notably, 2D-Ca2Si demonstrates an ultrahigh theoretical specific capacity of 5459mAhg-1 and a total specific capacity of 610mAhg-1, reaching up to 89% of the capacity of a potassium metal anode. Remarkably, the OMLG mechanism facilitates stable, dendrite-free deposition of hcp-K metal layers on the 2D-Ca2Si surface, where the ultrahigh and gradually converging lattice match as the layers increase is the key to achieving theoretically near-infinite growth. The study theoretically demonstrates the Ca2Si monolayer a highly promising anode material, and offers a novel potassium storage strategy for designing 2D anode materials with high specific capacity, rapid potassium-ion migration, and good safety.

Al-Based MOF-Derived Amorphous/Crystalline Heterophase Cobalt Sulfides as High-Performance Supercapacitor Materials.

Transition metal sulfides (TMSs) are promising electrode materials due to their high theoretical specific capacitance, but sluggish charge transfer kinetics and an insufficient number of active sites hamper their applications in supercapacitors. In this work, a self-sacrificial template strategy was employed to construct Al-based MOF-derived metal sulfides with an amorphous/crystalline (a/c) heterophase, in which aluminum, nitrogen, and carbon species were evenly coordinated in the amorphous phase. The metal sulfides a/c-Co(Al)S-1 and a/c-Co(Al)S-2, originating from the CAU-1 and CoAl-MOF on NF as self-sacrificial templates, were investigated as electrode materials, respectively, in which the a/c-Co(Al)S-1 showed a more excellent electrochemical performance. Through acid etching CAU-1 using Co(NO3)2 followed by sulfuration, the a/c-Co(Al)S-1 with a unique 3D network structure was constructed, whose unique architecture expanded the interfacial contact with the electrolyte and provided vast active sites, accelerating the charge transportation and ion diffusion. Notably, the a/c-Co(Al)S-1 displayed a high specific charge of 1791.8 C g-1 at 1 A g-1, satisfactory cycle stability, and good rate capability. The corresponding assembled a/c-Co(Al)S-1//AC device delivered a high energy density of 77.1 Wh kg-1 at 800 W kg-1 and good durability (87.4% capacitance retention over 10 000 cycles).

In Situ Construction of Specific SEI Layer Affords Effective Prelithiation.

Silicon-based anodes have been attracting attention due to their high theoretical specific capacity, but their low initial Coulombic efficiency (ICE) seriously hinders their commercial application. Direct contact prelithiation is considered to be one of the effective means of solving this problem. By means of prelithiation, a specific solid electrolyte interphase (SEI) was constructed, which inhibited the volume expansion of the SiO/C composite anode during prelithiation and reduced the local current generated when the lithium source was in contact with the anode. On the one hand, it can reduce the side reactions derived from the decomposition of electrolytes in the prelithiation process, and on the other hand, it can slow down the prelithiation process and inhibit the volume expansion of the SiO/C composite anode in the prelithiation process. The results of XPS, TOF-SIMS, and other tests show that the use of an electrolyte whose main component is LiTFSI can construct SEI film whose main component is LiF, which to a certain extent can slow down the rate of prelithiation, reduce the local current generated when the lithium source is in contact with the negative electrode, minimize the occurrence of side reactions, and inhibit the volume expansion of the negative electrode material. The full battery assembled with NCM111 positive electrode still exhibits 83.5% capacity retention after 500 cycles at 1 C current density. These studies provide some ideas to enhance the performance of silicon-based materials.

Hexagonal MoO3 Anode with Extremely High Capacity and Cyclability for Lithium-Ion Battery: A Combined Theoretical and Experimental Study.

It is essential and still remains a big challenge to obtain fast-charge anodes with large capacities and long lifespans for Li-ion batteries (LIBs). Among all of the alternative materials, molybdenum trioxide shows the advantages of large theoretical specific capacity, distinct tunnel framework, and low cost. However, there are also some key shortcomings, such as fast capacity decaying due to structural instability during Li insertion and poor rate performance due to low intrinsic electron conductivity and ion diffusion capability, dying to be overcome. A unique strategy is proposed to prepare Ti-h-MoO3-x@TiO2 nanosheets by a one-step hydrothermal approach with NiTi alloy as a control reagent. The density functional theory (DFT) calculations indicate that the doping of Ti element can make the hexagonal h-MoO3-x material show the best electronic structure and it is favor to be synthesized. Furthermore, the hexagonal Ti-h-MoO3-x material has better lithium storage capacity and lithium diffusion capacity than the orthogonal α-MoO3 material, and its theoretical capacity is more than 50% higher than that of the orthogonal α-MoO3 material. Additionally, it is found that Ti-h-MoO3-x@TiO2 as an anode displays extremely high reversible discharge/charge capacities of 1326.8/1321.3 mAh g-1 at 1 A g-1 for 800 cycles and 611.2/606.6 mAh g-1 at 5 A g-1 for 2000 cycles. Thus, Ti-h-MoO3-x@TiO2 can be considered a high-power-density and high-energy-density anode material with excellent stability for LIBs.