Ionic Liquid-Directed Nanoporous TiNb2 O7 Anodes with Superior Performance for Fast-Rechargeable Lithium-Ion Batteries

Engineering of Cerium Modified TiNb2O7 Nanoparticles For Low-Temperature Lithium-Ion Battery

Although TiNb2O7 (TNO) with comparable operating potential and ideal theoretical capacity is considered to be the most ideal replacement for negative Li4Ti5O12 (LTO), the low ionic and electronic conductivity still limit its practical application as satisfactory anode for lithium-ion batteries (LIBs) with high-power density. Herein, TNO nanoparticles modified by Cerium (Ce) with outstanding electrochemical performance are synthesized. The successful introduction of Ce3+ in the lattice leads to increased interplanar spacing, refined grain size, more oxygen vacancy, and a smaller lithium diffusion barrier, which are conducive to improve conductivity of both Li+ and electrons. As a result, the modified TNO reaches high reversible capacity of 256.0 mA h g-1 at 100 mA g-1 after 100 cycles, and 183.0 mA h g-1 even under 3200 mA g-1. In particular, when the temperature drops to -20 °C, the cell undergoing 1500 cycles at a high current density of 500 mA g-1 can still reach 89.7 mA h g-1, corresponding to a capacity decay rate per cycle of only 0.033%. This work provides a new way to improve the electrochemical properties of alternative anodes for LIBs at extreme temperature.

Niobium-Based Oxide for Anode Materials for Lithium-Ion Batteries

Recently, it has become imperative to develop high energy density as well as high safety lithium-ion batteries (LIBS) to meet the growing energy demand. Among the anode materials used in LIBs, the currently used commercial graphite has low capacity and is a safety hazard due to the formation of lithium dendrites during the reaction. Among the transition metal oxide (TMO) anode materials, TMO based on the intercalation reaction mechanism has a more stable structure and is less prone to volume expansion than TMO based on the conversion reaction mechanism, especially the niobium-based oxide in it has attracted much attention. Niobium-based oxides have a high operating potential to inhibit the formation of lithium dendrites and lithium deposits to ensure safety, and have stable and fast lithium ion transport channels with excellent multiplicative performance. This review summarizes the recent developments of niobium-based oxides as anode materials for lithium-ion batteries, discusses the special structure and electrochemical reaction mechanism of the materials, the synthesis methods and morphology of nanostructures, deficiencies and improvement strategies, and looks into the future developments and challenges of niobium-based oxide anode materials.

Well-Dispersed Bi nanoparticles for promoting the lithium storage performance of Si Anode: Effect of the bridging Bi nanoparticles

Silicon (Si) is considered a promising anode material for lithium-ion batteries (LIBs) due to its high theoretical specific capacity of up to 4200 mAh/g. However, the poor cycling and rate performances of Si induced by the low intrinsic electronic conductivity and large volume expansion during the lithiation/delithiation process limit its practical application. Herein, a novel silicon/bismuth@nitrogen-doped carbon (Si/Bi@NC) composite with nanovoids was synthesized and investigated as an advanced anode material for LIBs. In such a structure, ultrafine bismuth nanoparticles coupled with an N-doped carbon layer were introduced to modify the surface of Si nanoparticles. Subsequently, the lithiated LixBi has excellent high ionic conductivity and acts as a fast transport bridge for lithium ions. The introduced carbon coating layer and nanovoids can buffer the volume expansion of Si during the lithiation/delithiation process, thus maintaining structural stability during the cycling process. As a result, the Si/Bi@NC composite exhibits excellent electrochemical performance, providing a relatively high capacity of 955.8 mAh/g at 0.5 A/g after 450 cycles and excellent rate performance with a high capacity of 477.8 mAh/g even at 10.0 A/g. Furthermore, the assembled full cell with LiFePO4 as cathode and pre-lithium Si/Bi@NC as anode can provide a high capacity of 138.8 mAh/g at 1C after 90 cycles, exhibiting outstanding cycling performance.

Heterogeneous-Structured Molybdenum Diboride as a Novel and Promising Anode for Lithium-Ion Batteries

With the development of electric vehicles, exploiting anode materials with high capacity and fast charging capability is an urgent requirement for lithium-ion batteries (LIBs). Borophene, with the merits of high capacity, high electronic conductivity and fast diffusion kinetics, holds great potential as anode for LIBs. However, it is difficult to fabricate for the intrinsic electron-deficiency of boron atom. Herein, heterogeneous-structured MoB2 (h-MoB2 ) with amorphous shell and crystalline core, is prepared by solid phase molten salt method. As demonstrated, crystalline core can encapsulate the honeycomb borophene within two adjacent Mo atoms, and amorphous shell can accommodate more lithium ions to strengthen the lithium storage capacity and diffusion kinetics. According to theoretical calculations, the lithium adsorption energy in MoB2 is about -2.7 eV, and the lithium diffusion energy barrier in MoB2 is calculated to be 0.199 eV, guaranteeing the enhanced adsorption capability and fast diffusion kinetic behavior of Li+ ions. As a result, h-MoB2 anode presents high capacity of 798 mAh g-1 at 0.1 A g-1 , excellent rate performance of 183 mAh g-1 at 5 A g-1 and long-term cyclic stability for 1200 cycles. This work may inspire ideas for the fabrication of borophene analogs and two-dimensional metal borides.

Structural Distortion in the Wadsley-Roth Niobium Molybdenum Oxide Phase Triggering Extraordinarily Stable Battery Performance

Wadsley-Roth niobium oxide phases have attracted extensive research interest recently as promising battery anodes. We have synthesized the niobium-molybdenum oxide shear phase (Nb, Mo)13 O33 with superior electrochemical Li-ion storage performance, including an ultralong cycling lifespan of at least 15000 cycles. During electrochemical cycling, a reversible single-phase solid-solution reaction with lithiated intermediate solid solutions is demonstrated using in situ X-ray diffraction, with the valence and short-range structural changes of the electrode probed by in situ Nb and Mo K-edge X-ray absorption spectroscopy. This work reveals that the superior stability of niobium molybdenum oxides is underpinned by changes in octahedral distortion during electrochemical reactions, and we report an in-depth understanding of how this stabilizes the oxide structure during cycling with implications for future long-life battery material design.

Emerging Multiscale Porous Anodes toward Fast Charging Lithium-Ion Batteries

With the accelerated penetration of the global electric vehicle market, the demand for fast charging lithium-ion batteries (LIBs) that enable improvement of user driving efficiency and user experience is becoming increasingly significant. Robust ion/electron transport paths throughout the electrode have played a pivotal role in the progress of fast charging LIBs. Yet traditional graphite anodes lack fast ion transport channels, which suffer extremely elevated overpotential at ultrafast power outputs, resulting in lithium dendrite growth, capacity decay, and safety issues. In recent years, emergent multiscale porous anodes dedicated to building efficient ion transport channels on multiple scales offer opportunities for fast charging anodes. This review survey covers the recent advances of the emerging multiscale porous anodes for fast charging LIBs. It starts by clarifying how pore parameters such as porosity, tortuosity, and gradient affect the fast charging ability from an electrochemical kinetic perspective. We then present an overview of efforts to implement multiscale porous anodes at both material and electrode levels in diverse types of anode materials. Moreover, we critically evaluate the essential merits and limitations of several quintessential fast charging porous anodes from a practical viewpoint. Finally, we highlight the challenges and future prospects of multiscale porous fast charging anode design associated with materials and electrodes as well as crucial issues faced by the battery and management level.

Insights into the Chemistry of the Cathodic Electrolyte Interphase for PTFE-Based Dry-Processed Cathodes

Dry processing is a promising method for high-performance and low-cost lithium-ion battery manufacturing which uses polytetrafluoroethylene (PTFE) as a binder. However, the electrochemical stability of the PTFE binder in the cathodes and the generated chemistry of the cathode electrolyte interphase (CEI) layers are rarely reported. Herein, the CEI properties and PTFE electrochemical stability are studied via cycling the high-loading dry-processed electrodes in electrolytes with LiPF6 or LiClO4 salt. Using LiClO4 salt can eliminate other possible F sources, allowing the decomposition of PTFE to be studied. The detection of LiF in cells with the LiClO4 salt confirms that PTFE undergoes side reaction(s) in the cathodes. When compared with LiClO4, the CEI layer is much thicker when LiPF6 is used as the electrolyte salt. These results provide insights into the CEI layer and may potentially enlighten the development of binders and electrolytes for the high efficiency and long durability of DP-based LIBs.

Partially Carbonized Polymer Binder with Polymer Dots for Silicon Anodes in Lithium-Ion Batteries

Large-scale applications of conventional conductive binders for silicon (Si) anodes are challenging to accomplish due to their complex synthesis steps and high cost. Herein, a carbonized polymer dots-assisted polyvinyl alcohol-chitosan (PVA-CS-CPDs) binder is developed through a simple and low-cost hydrothermal method. Through rational design, the PVA-CS-CPDs binder retains rich polar groups while forming conjugated structures. The conjugated structure endows the PVA-CS-CPDs with high electronic conductivity, and the retained polar groups maintain strong binding strength. The proposed water-soluble binding system acts as both a binder and conductive additive, enabling stable cycling for high-Si-content (90 wt.%) anodes without any other conductive additives.

Superimposed Effect of La Doping and Structural Engineering to Achieve Oxygen-Deficient TiNb2O7 for Ultrafast Li-Ion Storage

TiNb₂O₇ (TNO) is a competitive candidate of a fast-charging anode due to its high specific capacity. However, the insulator nature seriously hinders its rate performance. Herein, the La³⁺-doped mesoporous TiNb₂O₇ materials (La-M-TNO) were first synthesized via a facile one-step solvothermal method with the assistance of polyvinyl pyrrolidone (PVP). The synergic effect of La³⁺ doping and the mesoporous structure enables a dual improvement on the electronic conductivity and ionic diffusion coefficient, which delivers an impressive specific capacity of 213 mAh g^-1 at 30 C. The capacity retention (@30C/@1C) increases from 33 to 53 and 74% for TNO, M-TNO, and La-M-TNO (0.03), respectively, demonstrating a step-by-step improvement of rate performance by making porous structures and intrinsic conductivity enhancement. DFT calculations verify that the enhancement in electronic conductivity due to La³⁺ doping and oxygen vacancy, which induce localized energy levels via slight hybridization of O 2p, Ti 3d, and Nb 4d orbits. Meanwhile, the GITT result indicates that PVP-induced self-assembly of TNO accelerates the lithium ion diffusion rate by shortening the Li⁺ diffusion path. This work verifies the effectiveness of the porous structure and highlights the significance of electronic conductivity to rate performance, especially at >30C. It provides a general approach to low-conductivity electrode materials for fast Li-ion storage.

Nano-Sized Niobium Tungsten Oxide Anode for Advanced Fast-Charge Lithium-Ion Batteries

The further demand for electric vehicles and smart grids prompts that the comprehensive function of lithium-ion batteries (LIBs) has been improved greatly. However, due to sluggish Li⁺ diffusion rate, thermal runway and volume expansion, the commercial graphite as an important part of LIBs is not suitable for fast-charging. Herein, nano-sized Nb₁₄ W₃ O₄₄ blocks are effectively synthesized as a fast-charge anode material. The nano-sized structure provides shorter Li⁺ diffusion pathway in the solid phase than micro-sized materials by several orders of magnitude, corresponding to accelerating the Li⁺ diffusion rate, which is beneficial for fast-charge characteristics. Consequently, Nb₁₄ W₃ O₄₄ displays excellent long-term cycling life (135 mAh g^-1 over 1000 cycles at 10 C) and rate capability at ultra-high current density (≈103.9 mAh g^-1 , 100 C) in half-cells. In situ X-ray diffraction and Raman combined with scanning electron microscopy clearly confirms the stability of crystal and microstructure. Furthermore, the fabricated Nb₁₄ W₃ O₄₄ ||LiFePO₄ full cells exhibit a remarkable power density and demonstrate a reversible specific capacity. The pouch cell delivers long cycling life (the capacity retention is as high as 96.6% at 10 C after 5000 cycles) and high-safety performance. Therefore, nano-sized Nb₁₄ W₃ O₄₄ could be recognized as a promising fast-charge anode toward next-generation practical LIBs.

Polyvinylpyrrolidone regulated synthesis of mesoporous titanium niobium oxide as high-performance anode for lithium-ion batteries

TiNb₂O₇ (TNO) as a promising candidate anode for lithium-ion batteries (LIBs) shows obvious advantages in terms of specific capacity and safety, but which undergoes the intrinsic poor electrical and ionic conductivity. Herein, we propose a simple synthesis strategy of mesoporous TNO via a polymeric surfactant-mediated evaporation-induced sol-gel method, using polyvinylpyrrolidone (PVP) with different molecular weights (average Mw: 10000/58000/1300000) as the regulating agent, which greatly affects the lithium storage performance of the as-prepared TNO. The optimized TNO (i.e., PVP of 58000) delivers a high reversible capacity of 303.1 mAh/g at 1 C, with a retention rate of 73.4% (222.5 mAh/g) after 300 cycles. Even at 5 C, a high reversible capacity of 185.6 mAh/g can be achieved, with a retention rate of 72.3% after 1000 cycles. The superior lithium storage behavior is attributed to the fine mesoporous framework consisting of interconnected TNO nanocrystallites with high specific surface area and high mesoporosity, which greatly increases the active sites, improves the Li⁺ diffusion kinetics and alleviates volume fluctuation induced by the repetitive Li⁺ insertion-extraction processes.

Synchronous Manipulation of Ion and Electron Transfer in Wadsley-Roth Phase Ti-Nb Oxides for Fast-Charging Lithium-Ion Batteries

Implementing fast-charging lithium-ion batteries (LIBs) is severely hindered by the issues of Li plating and poor rate capability for conventional graphite anode. Wadsley-Roth phase TiNb₂ O₇ is regarded as a promising anode candidate to satisfy the requirements of fast-charging LIBs. However, the unsatisfactory electrochemical kinetics resulting from sluggish ion and electron transfer still limit its wide applications. Herein, an effective strategy is proposed to synchronously improve the ion and electron transfer of TiNb₂ O₇ by incorporation of oxygen vacancy and N-doped graphene matrix (TNO_{- x} @N-G), which is designed by combination of solution-combustion and electrostatic self-assembly approach. Theoretical calculations demonstrate that Li⁺ intercalation gives rise to the semi-metallic characteristics of lithiated phases (Li_y TNO_{- x} ), leading to the self-accelerated electron transport. Moreover, in situ X-ray diffraction and Raman measurements reveal the highly reversible structural evolution of the TNO_{- x} @N-G during cycling. Consequently, the TNO_{- x} @N-G delivers a higher reversible capacity of 199.0 mAh g^-1 and a higher capacity retention of 86.5% than those of pristine TNO (155.8 mAh g^-1 , 59.4%) at 10 C after 2000 cycles. Importantly, various electrochemical devices including lithium-ion full battery and hybrid lithium-ion capacitor by using the TNO_{- x} @N-G anode exhibit excellent rate capability and cycling stability, verifying its potential in practical applications.

Porous Co2VO4 Nanodisk as a High-Energy and Fast-Charging Anode for Lithium-Ion Batteries

The Li⁺ diffusion coefficient of Co₂VO₄ is evaluated by theoretical calculation to be as high as 3.15 × 10^–10 cm² s⁻¹, theoretically proving Co₂VO₄ a promising anode in fast-charging lithium-ion batteries.

A hexagonal porous Co₂VO₄ nanodisk (PCVO ND) structure is designed, featuring a high specific surface area of 74.57 m² g⁻¹ and numerous pores with a pore size of 14 nm.

The PCVO ND shows excellent fast-charging performance (a high average capacity of 344.3 mAh g⁻¹ at 10 C for 1000 cycles with only 0.024% capacity loss per cycle for 1000 cycles).

High-energy–density lithium-ion batteries (LIBs) that can be safely fast-charged are desirable for electric vehicles. However, sub-optimal lithiation potential and low capacity of commonly used LIBs anode cause safety issues and low energy density. Here we hypothesize that a cobalt vanadate oxide, Co₂VO₄, can be attractive anode material for fast-charging LIBs due to its high capacity (~ 1000 mAh g⁻¹) and safe lithiation potential (~ 0.65 V vs. Li⁺/Li). The Li⁺ diffusion coefficient of Co₂VO₄ is evaluated by theoretical calculation to be as high as 3.15 × 10^–10 cm² s⁻¹, proving Co₂VO₄ a promising anode in fast-charging LIBs. A hexagonal porous Co₂VO₄ nanodisk (PCVO ND) structure is designed accordingly, featuring a high specific surface area of 74.57 m² g⁻¹ and numerous pores with a pore size of 14 nm. This unique structure succeeds in enhancing Li⁺ and electron transfer, leading to superior fast-charging performance than current commercial anodes. As a result, the PCVO ND shows a high initial reversible capacity of 911.0 mAh g⁻¹ at 0.4 C, excellent fast-charging capacity (344.3 mAh g⁻¹ at 10 C for 1000 cycles), outstanding long-term cycling stability (only 0.024% capacity loss per cycle at 10 C for 1000 cycles), confirming the commercial feasibility of PCVO ND in fast-charging LIBs.

Operando Analysis of Gas Evolution in TiNb2O7 (TNO)-Based Anodes for Advanced High-Energy Lithium-Ion Batteries under Fast Charging

TiNb₂O₇ (TNO) is regarded as one of the promising next-generation anode materials for lithium-ion batteries (LIBs) due to its high rate capabilities, higher theoretical capacity, and higher lithiation voltage. This enables the cycling of TNO-based anodes under extreme fast charging (XFC) conditions with a minimal risk of lithium plating compared to that of graphite anodes. Here, the gas evolution in real time with TNO-based pouch cells is first reported via operando mass spectrometry. The main gases are identified to be CO₂, C₂H₄, and O₂. A solid-electrolyte interphase is detected on TNO, which continues evolving, forming, and dissolving with the lithiation and delithiation of TNO. The gas evolution can be significantly reduced when a protective coating is applied on the TNO particles, reducing the CO₂ and C₂H₄ evolution by ∼2 and 5 times, respectively, at 0.1C in a half-cell configuration. The reduction on gas generation in full cells is even more pronounced. The surface coating also enables 20% improvement in capacity under XFC conditions.

Mesoscopic Ti2Nb10O29 cages comprised of nanorod units as high-rate lithium-ion battery anode

Benefiting from large tunnel structure, zero strain feature, and excellent pseudocapacitive performance, Ti₂Nb₁₀O₂₉ was considered as a potential anode material for lithium-ion batteries (LIBs). Herein, Ti₂Nb₁₀O₂₉ cages comprised of nanorod units were elaborately designed. The mesoscopic structure could effectively shorten the ion diffusion pathway, and the big central electrolyte reservoir relieves the concentration polarization of electrolyte. Moreover, the perforated pore feature guarantees competent contact between electrolyte and framework. As the anode of LIBs, the mesoscopic Ti₂Nb₁₀O₂₉ cages deliver high reversible capacity (302.5 mAh/g) and rate capability (134.3 mAh/g at 30 A/g). This unique mesoscopic structure holds excellent potential for the electrode design of high-rate and long-life LIBs.

Inorganic Synthesis Based on Reactions of Ionic Liquids and Deep Eutectic Solvents

Ionic liquids and deep eutectic solvents are of growing interest as solvents for the resource‐efficient synthesis of inorganic materials. This Review covers chemical reactions of various deep eutectic solvents and types of ionic liquids, including metal‐containing ionic liquids, [BF₄]⁻‐ or [PF₆]⁻‐based ionic liquids, basic ionic liquids, and chalcogen‐containing ionic liquids. Cases in which cations, anions, or both are incorporated into the final products are also included. The purpose of this Review is to raise caution about the chemical reactivity of ionic liquids and deep eutectic solvents and to establish a guide for their proper use.

Tailoring Stress and Ion-Transport Kinetics via a Molecular Layer Deposition-Induced Artificial Solid Electrolyte Interphase for Durable Silicon Composite Anodes

Silicon is considered as a blooming candidate material for next-generation lithium-ion batteries due to its low electrochemical potential and high theoretical capacity. However, its commercialization has been impeded by the poor cycling issue associated with severe volume changes (∼380%) upon (de)lithiation. Herein, an organic-inorganic hybrid film of titanicone via molecular layer deposition (MLD) is proposed as an artificial solid electrolyte interphase (SEI) layer for Si anodes. This rigid-soft titanicone coating with Young's modulus of 21 GPa can effectively relieve stress concentration during the lithiation process, guaranteeing the stability of the mechanical structure of a Si nanoparticles (NPs)@titanicone electrode. Benefiting from the long-strand (Ti-O-benzene-O-Ti-) unit design, the optimized Si NPs@70 cycle titanicone anode delivers a high Li⁺ diffusion coefficient and a low Li⁺ diffusion barrier, as revealed by galvanostatic intermittent titration (GITT) investigations and density functional theory (DFT) simulations, respectively. Ultimately, the Si NPs@70 cycle titanicone electrode shows high initial Coulombic efficiency (84%), long cycling stability (957 mAh g^-1 after 450 cycles at 1 A g^-1), a stable SEI layer, and good rate performances. The molecular-scale design of the titanicone-protected Si anodes may bring in new opportunities to realize the next-generation lithium-ion batteries as well as other rechargeable batteries.

Sn modified nanoporous Ge for improved lithium storage performance

Although high-capacity germanium (Ge) has been regarded as the promising anode material for lithium ion batteries (LIBs), its actual performance is far from expectation because of low electrical conductivity and rapid capacity decay during cycling. In this work, Sn modified nanoporous Ge materials with different Ge/Sn atomic ratios in precursors were synthesized by a simple melt-spinning and dealloying strategy. As the anodes of LIBs, Sn modified nanoporous Ge materials display improved cycling stability compared with Sn-free nanoporous Ge, revealing a potential role of Sn in improving electrochemical properties of Ge-based anodes. In particular, Sn modified nanoporous Ge with Ge/Sn atomic ratio of 3:1 presents the best Li storage performance among measured electrodes, delivering a reversible capacity of 974 mA h g^-1 after 500 cycles at 200 mA g^-1. It is found that the introduction of appropriate amount of Sn can not only regulate the nanoporous structure of Ge to better alleviate volume expansion, but also improves the conductivity and activity of the electrode material. This improvement is demonstrated by density functional theory calculations. The study uncovers a route to improve Li storage properties by rationally modify Ge-based anodes with Sn, which may facilitate the development of high-performance LIBs.

Alloyed BiSb Nanoparticles Confined in Tremella-Like Carbon Microspheres for Ultralong-Life Potassium Ion Batteries

Bismuth-antimony alloy is considered as a promising potassium ion battery anode because of its combination of the high theoretical capacity of antimony and the excellent rate capacity of bismuth. However, the large volume change and sluggish reaction kinetic upon cycling have triggered severe capacity fading and poor rate performance. Herein, a nanoconfined BiSb in tremella-like carbon microspheres (BiSb@TCS) are delicately designed to address these issues. As-prepared BiSb@TCS renders an outstanding potassium-storage performance with a reversible capacity of 181 mAh g^-1 after ultralong 5700 cycles at a current density of 2 A g^-1 , and an excellent rate capacity of 119.3 mAh g^-1 at 6 A g^-1 . Such a superior performance can be ascribed to the delicate microstructure. The self-assembled carbon microspheres can strengthen integral structure and effectively accommodate the volume expansion of BiSb nanoparticles, and 2D carbon nanowalls in carbon microspheres can provide fast ion/electron diffusion dynamic. Theoretical calculation also suggests a thermodynamic feasibility of alloyed BiSb nanoparticles for storing potassium ion. Such a work shows that BiSb@TCS possesses a great potential to be a high-performance anode of potassium ion batteries. The rational designing of multiscaled structure would be instructive to the exploitation of other energy-storage materials.

Precisely Tunable T-Nb2O5 Nanotubes via Atomic Layer Deposition for Fast-Charging Lithium-Ion Batteries

The demand for fast-charging of lithium-ion batteries (LIBs) in modern electric transportation and wearable electronics is rapidly growing. However, commercially available graphite anodes still suffer from slow kinetics of lithium-ion diffusion and severe safety concerns of lithium plating when achieving the fast-charging goal. Here, it is demonstrated that the Li-ion diffusion kinetics of orthorhombic Nb₂O₅ nanotubes (T-Nb₂O₅ NTs) is enhanced by atomically precise manufacturing of nanoarchitectures. The controlled fabrication of T-Nb₂O₅ NTs with wall thicknesses from 24 to 43 nm is realized via atomic layer deposition (ALD) using electrospun polyacrylonitrile nanofibers as a sacrificing template. The wall thickness of T-Nb₂O₅ NTs can be precisely tuned by adjusting the number of ALD cycles. The relationship between the wall thicknesses and electrochemical performances is investigated in detail. The electrochemical kinetic analysis suggests that the lithium storage in T-Nb₂O₅ NTs is dominated by surface and intercalation pseudocapacitance. The morphology of T-Nb₂O₅ crystallites is found to have significant effects on the Li-ion insertion/extraction kinetics and the performance of the electrodes in LIBs. The resulting T-Nb₂O₅ NTs exhibit fast charge-storage kinetics and enable highly reversible insertion/extraction of Li ions without a phase change. This work may open up a new avenue for further development of intercalation-pseudocapacitive nanostructured materials for high-rate and ultrastable energy-storage devices.

Realizing the enhanced cyclability of a cactus-like NiCo2O4 nanocrystal anode fabricated by molecular layer deposition

Lithium-ion batteries with conversion-type anode electrodes have attracted increasing interest in providing higher energy storage density than those with commercial intercalation-type electrodes. However, conversion-type materials exhibit severe structural instability and capacity fade during cycling. In this work, a molecular layer deposition (MLD)-derived conductive Al₂O₃/carbon layer was employed to stabilize the structure of the cactus-like NiCo₂O₄ nanocrystal (NC) anode. The conductive Al₂O₃/carbon network and cactus-like NiCo₂O₄ NCs are beneficial for fast Li⁺/e^- transport. Moreover, the Al₂O₃/carbon buffer-layer can prevent the NiCo₂O₄ NCs from agglomeration and form a steady solid electrolyte interphase (SEI), thus hampering the penetration of the electrolyte. Owing to these advantages, the assembled NiCo₂O₄@Al₂O₃/carbon half battery shows a high reversible capacity (931.2 mA h g^-1 at 2 A g^-1) and long-term stability of 290 mA h g^-1 at 5 A g^-1 over 500 cycles. Quantitative analyses further reveal the fast kinetics and the capacitance-battery dual model mechanism in the 3D core-shell structures. The design and introduction of MLD-derived hybrid coating may open a new way to conversion-type and alloy-type anode materials beyond NiCo₂O₄ to achieve high cyclability.

Hierarchical structure TiNb2O7 microspheres derived from titanate for high-performance lithium-ion batteries

Hierarchical structure TiNb₂O₇ microspheres derived from titanate displayed satisfactory long-term cycling stability and prominent rate capability for lithium-ion batteries.