Full-cell Configuration Research Articles

Double Carbon-Species Coated Porous Silicon Anode Induced by Interfacial Energy Reduction for Lithium-Ion Batteries.

The rapid development of electric vehicles necessitates high-energy density Li-ion batteries for extended range. Silicon is a promising alternative to graphite anodes due to its high capacity; however, its substantial volume expansion during cycling leads to continuous growth of the solid electrolyte interphase and significant capacity fading. This study addresses these issues by designing a porous Si structure combined with a double carbon-species coating layer, induced by low interfacial energy in a scalable process. Carbon and graphene are located on Si surfaces, forming a close interface that maintains electrical contact, suppresses lithium consumption, and enhances charge transfer properties. The composite anode with a double carbon-species coating on Si demonstrates rapid stabilization with increasing coulombic efficiency, achieving a specific capacity of 1,814 mAh g-1 at 0.2 C and a high-rate capability of 1,356 mAh g-1 at 10C. Additionally, in a full-cell configuration with LiFePO4, it recorded a specific capacity of 161 mAh g-1 at 0.2 C. These results show the potential of porous Si with a carbon-graphene coating for stable, high-capacity operation in Li-ion batteries, offering new insights into high-performance electrochemical systems. Moreover, the double carbon-species coating derived from a scalable surface chemistry-based process presents a realistic alternative for industrial applications.

Water-Mediated Surface Engineering Enhances High-Voltage Stability of Fast-Charge LiCoO2 Cathodes.

Maintaining the surface structure stability of LiCoO2 (LCO) during rapid charge-discharge processes (>5C) and under high-voltage conditions (>4.2 V) is challenging due to interfacial side reactions, cobalt dissolution, and oxygen redox activity at deeply delithiated states, all of which contribute to performance degradation. Herein, different from traditional surface coating methods, we report a water-mediated strategy that modifies the surface architecture of LCO, creating a passivating layer to inhibit surface degradation and enhance cycling stability under fast charging conditions. The surface etching of LCO by H2O is accompanied by a concurrent Li+/H+ cation exchange, which passivates surface oxygen with H+ ions, thereby enhancing both the hydrophobicity and structural stability. Consequently, the modified LCO exhibits superior capacity retention, which is 2.5 times that of the pristine LCO, after 100 cycles at a current density of 1000 mA g-1 (∼6C at 4.5 V). Even at an elevated temperature of 45 °C, it maintains impressive cycling stability at a current density of 500 mA g-1 (∼3C), as demonstrated in practical full-cell configurations. Investigation with multiple samples confirmed that the water-mediated strategy demonstrated broad applicability. We emphasize that the water-mediated modification of the surface architecture on cathode materials offers significant insights into enhancing the stability of high-energy-density lithium-ion batteries (LIBs).

Transition metal-assisted layer-by-layer binder free deposition for high-performance energy storage devices

The increasing energy demands of the world necessitate the development of advanced energy storage systems. Hybrid supercapacitors (HSCs) have emerged as promising candidates, combining the high specific power density (PS) of supercapacitors (SCs) with the high specific energy density (ES) of batteries (BATs). However, its performance is dependent on the properties of electrode materials, which need enhancements in conductivity, surface area, and electrochemical stability. In this study, we utilized magnetron sputtering technique for exploring the potential of interface engineering to improve the electrochemical performance of tungsten disulfide (WS2) as a battery grade electrode material by incorporating chromium (Cr) and titanium (Ti) as an interfacial layer. This strategic modification significantly increased the conductivity, charge transfer efficiency, and structural stability of the WS2 electrode. Electrochemical experimentation in both half-cell and full-cell configurations revealed that the WS2/Cr and WS2/Ti electrode exhibits superior CS [2400 and 3800] F/g, respectively compared to pristine WS2. Fabricated WS2/Cr//AC and WS2/Ti//AC attained ES [95 and 117] Wh/kg and PS [6800 and 8500] W/kg, respectively. The outcomes from the electrochemical testing further demonstrated the superior cyclic stability of WS2/Cr//AC and WS2/Ti//AC with [96.5 and 98.3] % which shows that Cr and Ti as an interfacial layer not only mitigates the limitations of WS2 but also enables the devices to achieve higher performance metrics, underscoring the critical role of interface engineering in advancing HSCs technologies.

Enhanced Hydrogen Bonding Through Strong Water‐Locking Additives for Long‐Term Cycling of Zinc Ion Batteries

AbstractThe promising energy storage devices, zinc ion batteries (ZIBs), face challenges such as dendritic growth and side reactions, which hinder their application and development. As a polar group, hydroxyl groups can utilize hydrogen bonding to stably anchor water molecules, preventing contact between water and the anode. Moreover, they can attract and guide Zn2+ to rapidly and uniformly deposit on the anode. Here, the introduction of multi‐hydroxyl water‐locking additive Lactobionic acid (LA) molecules is proposed into conventional electrolytes. Through an in situ reaction between the highly reactive carboxyl groups on LA molecules and the zinc anode, a stable multi‐hydroxyl protective layer is formed on the anode surface, effectively preventing interface corrosion and dendritic growth. As a result, the Zn||Zn symmetric cell with LA exhibits remarkable performance, cycling for 2300 h under 1 mA cm−2 and 1 mAh cm−2. Even under more rigorous conditions of 10 mA cm−2 and 10 mAh cm−2, it maintains over 800 h of cycling durability. Moreover, in the Zn||NH4V4O10 full cell configuration, an impressive capacity retention rate of 80.35% after 2000 cycles at a current density of 5 A g−1. This innovative method can open a new avenue for designing high‐performance ZIBs.

Dual carbon confining SnO2 nanocrystals as high-performance anode for sodium-ion batteries

The increasing global demand for sustainable energy sources has driven research into sodium-ion batteries (SIBs) for large-scale energy storage. However, their electrochemical performance is hindered by poor reaction kinetics and significant volume expansion in electrode materials. In this work, we developed a dual-carbon-confined SnO2 nanocrystal anode (CNTs@SnO2@NC) designed for high-performance SIBs. This innovative structure uses carbon nanotubes (CNTs) and a nitrogen-doped carbon (NC) coating to stabilize SnO2, ensuring structural integrity during charge/discharge cycles. The CNTs network in CNTs@SnO2@NC can alleviate the agglomeration of SnO2 nanocrystals to a certain extent; With its superior electronic conductivity, CNTs can enhance the anode's conductivity and function as an electronic highway; The sodiophilic properties and good electrical conductivity of CNTs enable sodium ions to migrate rapidly on the surface of the nanotubes. Moreover, numerous external defects and active sites generated by nitrogen doping enhance the sodium ion absorption capabilities; The existence of nitrogen-doped carbon coating can effectively accommodate the volume changes of SnO2 and enhance the structural stability of CNTs@SnO2@NC composites during the repeated charge and discharge cycles. As a result, the CNTs@SnO2@NC composite demonstrates excellent electrochemical performance, achieving capacity of 235 mAh g−1 at 0.1 A g−1 over 100 cycles and 102 mAh g−1 at 1.0 A g−1 over 300 cycles. In a full-cell configuration with a Na3V2(PO4)3 cathode, it delivers 38 mAh g−1 at 100th cycle at 0.1 A g−1. This study underscores the substantial improvements achieved by dual-carbon confinement for high-performance SIB anodes, offering a promising direction for future anode material design.

Cobalt-doped copper sulfide nanocomposite integrated with graphene oxide as a high-performance conversion anode for aqueous zinc-ion batteries

Rechargeable aqueous zinc-ion batteries (ZIBs) encounter substantial obstacles arising from the inherent dilemmas of dendrite growth, hydrogen gas evolution, and corrosion affiliated with zinc metal anodes, thereby highlighting the necessity for researching conversion anode materials as a promising pathway forward. Copper sulfide (CuS) has been demonstrated as a promising conversion anode material for ZIBs due to its notable electrochemical performance, while challenges persist regarding the Coulombic interactions between Zn2+ and host anions, coupled with the material’s fundamental conductivity that remains less than fully satisfactory. To address the above issues, we have designed and synthesized a nanostructured composite of cobalt doped CuS integrated in graphene oxide frames (GO/Co-CuS) as anode for ZIBs. The cobalt doping serves to alleviate Coulomb interaction (Coulomb attraction) between Zn2+ and host anions, thereby enhancing the kinetics of Zn2+ diffusion. Furthermore, the incorporation of GO framework improves the electrical conductivity of the material and mitigates volume expansion during the reaction process. The synergistic effect engendered by the combination of cobalt doping and the incorporation of a GO framework results in the remarkable electrochemical performance exhibited by GO/Co-CuS. The GO/Co-CuS composite nanostructure exhibited commendable rate capability and cycling stability. Specifically, it exhibits remarkable rate capability, delivering 296 mAh g−1 at 1 A/g and 168 mAh g−1 at 10 A/g. Furthermore, after 1000 cycles at a high current density of 10 A/g, it maintains a capacity of 166 mAh g−1, demonstrating exceptional cycling stability. Additionally, the full-cell configuration of GO/Co-CuS//MnO2@CNTs, when cycled 241 times at 2 A/g, retains a capacity of 79 mAh g−1, thereby confirming the practical efficacy of the GO/Co-CuS nanocomposite as an efficient conversion anode for ZIBs.

Heterogeneous NASICON-Type Cathode With Reversible Multielectron Reaction for High-Performance Sodium-Ion Batteries.

Na superionic conductor (NASICON)-structured compounds demonstrate great application potential by their robust framework and compositional diversity. However, they are blamed for the mediocre energy density, and achieving both multielectron reaction and good cycling stability simultaneously is challenging. Herein, a novel heterogeneous Na4Fe3(PO4)2(P2O7)/Na2VTi(PO4)3 (NFPP/NVTP) material with stable multielectron reaction is constructed by spray drying technology. The mutual promotion effect of intergrowth structures effectively improves the purity and the crystallization of NFPP/NVTP during the fabrication process, which is beneficial to the high capacity and cycling stability. As a result, the optimized NFPP/NVTP demonstrates a high reversible capacity of 155.3 mAh g-1 at 20mA g-1 and outstanding cycling stability with 82.9% capacity retention over 2500 cycles at 1 A g-1, which are much superior to those of NFPP and NVTP individually. Even in full cell configuration, the energy density remains high at ≈380Wh kg-1 based on the cathode mass. The high capacity of NFPP/NVTP is also attributed to the successive reduction/oxidation mechanism involving the introduction of Ti3+ and interfacial charge redistribution effect between the heterogeneous phases, which greatly improve the electronic and ionic conductivity. Moreover, high reversible structural evolution during the multisodium storage process further guarantees excellent cycling stability.

Polarization-Switchable Electrochemistry of 2D Layered Bi2O2Se Bifunctional Microreactors by Ferroelectric Modulation.

Ferroelectric catalysts are known for altering surface catalytic activities by changing the direction of their electric polarizations. This study demonstrates polarization-switchable electrochemistry using layered bismuth oxyselenide (L-Bi2O2Se) bifunctional microreactors through ferroelectric modulation. A selective-area ionic liquid gating is developed with precise control over the spatial distribution of the dipole orientation of L-Bi2O2Se. On-chip microreactors with upward polarization favor the oxygen evolution reaction, whereas those with downward polarization prefer the hydrogen evolution reaction. The microscopic origin behind polarization-switchable electrochemistry primarily stems from enhanced surface adsorption and reduced energy barriers for reactions, as examined by nanoscale scanning electrochemical cell microscopy. Integrating a pair of L-Bi2O2Se microreactors consisting of upward or downward polarizations demonstrates overall water splitting in a full-cell configuration based on a bifunctional catalyst. The ability to modulate surface polarizations on a single catalyst via ferroelectric polarization switching offers a pathway for designing catalysts for water splitting.

A Practical Zinc Metal Anode Coating Strategy Utilizing Bulk h‐BN and Improved Hydrogen Redox Kinetics

Achieving high‐performance aqueous zinc‐ion batteries requires addressing the challenges associated with the stability of zinc metal anodes, particularly the formation of inhomogeneous zinc dendrites during cycling and unstable surface electrochemistry. This study introduces a practical method for scattering untreated bulk hexagonal boron nitride (h‐BN) particles onto the zinc anode surface. During cycling, stabilized zinc fills the interstices of scattered h‐BN, resulting in a more favorable (002) orientation. Consequently, zinc dendrite formation is effectively suppressed, leading to improved electrochemical stability. The zinc with scattered h‐BN in a symmetric cell configuration maintains stability 10 times longer than the bare zinc symmetric cell, lasting 500 hours. Furthermore, in a full cell configuration with α‐MnO2 cathode, increased H+ ion activity can effectively alter the major redox kinetics of cycling due to the presence of scattered h‐BN on the zinc anode. This shift in H+ ion activity lowers the overall redox potential, resulting in a discharge capacity retention of 96.1% for 300 cycles at a charge/discharge rate of 0.5 A g−1. This study highlights the crucial role of surface modification, and the innovative use of bulk h‐BN provides a practical and effective solution for improving the performance and stability.

La0.8Sr0.2CoO3 Electrocatalyst for Oxygen Evolution Reaction in Alkaline Electrolysis: From Powder to the Fuel Cell Application

In recent years, there has been a growing need for new renewable energy sources due to the rapid depletion of conventional energy sources and an escalating energy demand. Since environmental protection concerns are increasing, electrochemical processes are becoming increasingly essential [1]. Specifically, the focus has shifted towards storing energy in hydrogen and its subsequent conversion into on-demand electricity [2]. Here, hydrogen, generated via water electrolysis, serves as either an intermediary for generating energy carriers like liquid fuels or plays a key role as an energy carrier [3]. Despite significant efforts focused on enhancing electrolyzers for energy conversion, the progression towards practical application has encountered challenges stemming from differing catalyst development requisites in academic and industrial research. This study proposes a systematic approach for efficiently transitioning electrocatalysts from fundamental research to application readiness for alkaline oxygen evolution reactions.Herein, La0.8Sr0.2CoO3 was chosen as a catalyst and compared with the benchmark material NiFe2O4. Initially, the La0.8Sr0.2CoO3 catalyst was successfully synthesized by scalable spray-flame synthesis. Following this, various inks were formulated utilizing different binders (Nafion®, Naf; Sustainion®, Sus). The dispersion stability of La0.8Sr0.2CoO3 and commercial NiFe2O4 inks was investigated in the presence of Nafion and Sustainion using analytical centrifugation and transmittograms. Subsequently, these selected dispersions were applied onto nickel substrates via spray coating techniques, ensuring a homogeneous catalyst distribution. Finally, the La0.8Sr0.2CoO3 and NiFe2O4 catalysts were subjected to extensive electrochemical evaluations, including glassy carbon rotating disk electrode, scanning droplet cell (SDC), compression cell, flow cell, and zero-gap cell, to evaluate the material performance. SDC findings highlight the excellent uniformity in La0.8Sr0.2CoO3 electrodes and NiFe2O4-Sustainion (standard deviation < 11%). However, the NiFe2O4-Sustainion film experienced delamination, exhibiting a standard deviation of 28%. SDC experiments offer advantages over various half-cell techniques by enabling the detection of any inhomogeneities or coating defects within the catalytic film. Additionally, complementary compression and flow cell experiments provide detailed information on the chemical and mechanical stress parameters resembling those in a full cell configuration. In assessing industrial applicability, the catalytic materials were undergone examination within a scalable full cell under industrial conditions (500 mA/cm² and 60 °C) utilizing a zero-gap cell setup. The observed trend in the full cell for the coated electrodes is as follows: La0.8Sr0.2CoO3-Naf > La0.8Sr0.2CoO3-Sus > NiFe2O4-Sus > NiFe2O4-Naf.These findings achieved through a well-structured coherent workflow, enhance our knowledge of the electrocatalytic system and offer essential insights for implementing novel materials in large-scale industrial applications. REFERENCES: [1] M.-S. Park, J. Kim, K.J. Kim, J.-W. Lee, J.H. Kim, Y. Yamauchi, Porous nanoarchitectures of spinel-type transition metal oxides for electrochemical energy storage systems, Phys. Chem. Chem. Phys. 17 (2015) 30963–30977. https://doi.org/10.1039/C5CP05936D.[2] J.R. Varcoe, P. Atanassov, D.R. Dekel, A.M. Herring, M.A. Hickner, P.A. Kohl, A.R. Kucernak, W.E. Mustain, K. Nijmeijer, K. Scott, T. Xu, L. Zhuang, Anion-exchange membranes in electrochemical energy systems, Energy Environ. Sci. 7 (2014) 3135–3191. https://doi.org/10.1039/C4EE01303D.[3] C. Van Pham, D. Escalera-López, K. Mayrhofer, S. Cherevko, S. Thiele, Essentials of High Performance Water Electrolyzers – From Catalyst Layer Materials to Electrode Engineering, Adv. Energy Mater. 11 (2021) 2101998. https://doi.org/https://doi.org/10.1002/aenm.202101998.

(Invited) Structural Lithium-Ion Battery Based on LiFePO4/Reduced Graphene Oxide Composite Cathode and Graphene Anode Prepared via Electrophoretic Deposition on Carbon Cloth

Structural lithium-ion batteries based on binder-free LiFePO4/reduced graphene oxide composite cathode electrode and graphene anode electrode are prepared respectively via electrophoretic co-deposition of LiFePO4, reduced graphene oxide, and carbon black on carbon cloth substrate for the cathode, and graphene oxide and carbon black on carbon cloth substrate for the anode. Following deposition, the electrode materials were dried. The graphene oxide of the anode was reduced to graphene via rapid thermal annealing. Possessing excellent stiffness, strength-to-weight ratio, and good electrical conductivity, the carbon cloth substrate serves multifunctional roles in the battery: as structural reinforcement and mechanical load bearing element and as current collector. Given its good electrical conductivity, high aspect ratio, and high surface area, reduced graphene oxide improves electrical conductivity within the cathode and provides sites for hosting LiFePO4; this enhances reversible Li ion extraction from the host during cycling. Graphene with its good electrical conductivity and high aspect ratio provides sites for insertion of Li ions in the anode; this enhances the aerial lithiation capacity of the battery system. Carbon black enhances conductivity within the two electrodes and reduces interfacial impedance. The electrochemical properties of the electrodes are strongly correlated to their microstructure and phase composition. Electrochemical characterization of the electrodes and their performance in half-cell and full cell configurations are evaluated. Additionally, Li-ion diffusivity within the materials is evaluated with three independent electroanalytical methods, including potentiostatic and galvanostatic and intermittent titration techniques, and electrochemical impedance spectroscopy.

Fabrication of Na+-Conducting Ionic Liquids Na[((FSO2)2n) x ((CF3SO2)(FSO2)N)1-X ], and Its Physical and Electrochemical Properties

To achieve low-carbon society in near future, it’s imperative to research and develop high-performance and low-cost batteries. Therefore, sodium-ion batteries (SIBs) are attracting attention owing to their possibility to be composed of elements with no resource scarcity and low cost.To solve the challenge of low energy density in SIBs, it is essential to focus on developing electrodes of the 4V to 5V class. Simultaneously, electrolytes with wide electrochemical window are crucial from in terms of electrolyte decomposition at high operating voltages. Molten salt electrolytes exhibit relatively high ionic conductivity and electrochemical stability. On the other hands, there is an issue that the electrolyte must be heated to a high temperature to maintain molten state of the electrolytes. In this study, with the goal of expanding the melting temperature range of molten salt electrolytes, we precisely mixed relatively low-melting sodium salts Na(FSO2)2N (NaFSA) and Na(CF3SO2)(FSO2)N (NaFTA) and found a composition with a melting point below 100 ℃. As a result, we successfully fabricated novel single-sodium cationic salt ionic liquid. In this presentation, we will report on its bulk properties and electrochemical characteristics. All mixed sodium salts were mixed NaFSA and NaFTA in each molar ratio and stirred during gradually cooling after uniformly melting at 170 ℃ in Ar-filled grove box. The thermal properties of the mixed sodium salts were evaluated by differential scanning calorimetry (DSC). The samples were stored at room temperature for 2~3 days to reach equilibrium state, and then sealed in a high-pressure SUS pan. Ionic conductivity (σ) of the mixed sodium salts were also measured from 60 ℃ to 135 ℃ at each temperature. Symmetrical cells were constructed by put the mixed sodium salt between two SUS or sodium metal electrodes. Ionic conductivity of mixed sodium salts was evaluated by electrochemical impedance spectroscopy (EIS) with SUS electrodes symmetric cells. Na+ transference number was measured by potentiostatic polarization and EIS with sodium metal symmetric cells at 90℃. The binary phase diagram of NaFSA and NaFTA were shown in Fig.1. In the NaFTA-rich composition range (0.1 < x < 0.4), the phase diagram resembles a simple eutectic phase diagram, while, in the NaFTA-rich composition range (0.5 < x < 0.9), the mixed sodium salts exhibited pseudo-single-phase behavior, and the lowest liquid-phase transition temperature (T L) was observed at 90℃ of Na[(FSA)0.8(FTA)0.2].(1) Additionally, in this composition range, glass transition points (T g) were also confirmed, indicating the supercooled behavior.The Arrhenius plot of the ionic conductivity (σ) for Na[(FSA)0.8(FTA)0.2] was shown in Fig.2. At the T L around 90℃, σ was observed to 0.69 mS cm-1. This is attributed to the strong interactions between Na+ and anion in the absence of solvents, causing high viscosity and decreasing mobility. Below the T L, there was no remarkable decrease in σ and Nyquist plots remained non-divergent to 55℃, allowing for the attribution of σ. Moreover, below the T L, the glass transition and crystallization of Na[(FSA)0.8(FTA)0.2] were not observed. The temperature dependence of σ was analyzed by the Vogel-Fulcher-Tamman (VFT) equation.(2) In addition, the σ(T g) at the observed T g from DSC were calculated by VFT equation. Also, the decoupling index (R τ), representing the ratio of ionic conductive relaxation time (τ σ) to structural relaxation time (τ s), were calculated.(3) The value of logR τ value for Na[(FSA)0.8(FTA)0.2] was -0.62 and the low value indicates that τ s is coupled with τ σ.To investigate the Na+ conduction behavior in Na[(FSA)0.8(FTA)0.2], chronoamperograms with an applied potential of 500 mV to the sodium metal symmetric cells were shown in Fig.3(a). Fig.3(b) shows Nyquist plots before and after direct current polarization. The steady current was observed after 8h. Furthermore, there was slightly changes of Nyquist plots before and after direct current (DC) polarization, stable interface between sodium metal and Na[(FSA)0.8(FTA)0.2] was also confirmed. The Na+ transference Number (t Na+) in the Na[(FSA)0.8(FTA)0.2] was estimated to be 0.86. Tatara et al. reported the t Na+ of 0.18 in the 1M NaPF6/PC+0.5vol% FEC.(4) Since molten salts consisting of only cations and anions should not be occurred concentration polarization, it exhibited a considerably higher t Na+ in Na[(FSA)0.8(FTA)0.2] compared to the t Na+ in dilute non-aqueous sodium electrolyte. In the presentation, we will discuss the cycle characteristics obtained by constant current charge-discharge tests of both half-cell and full-cell configurations using generic positive and negative electrode materials.(1) K. Kubota et al., J. Chem. Eng. Data, 55, No. 9, 2010, 3142–3146.(2) H. Vogel., Phys. Z. 1921, 22, 645.(3) C. A. Angell, Annu. Rev. Phys. Chem. 1992, 43, 693.(4) R. Tatara et al., Electrochemistry, 89(6), 2021, 590–596. Figure 1

(Invited) MAX Phase Oxidation As a Novel Approach to Highly Reversible Oxide Nanocomposite Electrodes for Lithium-Ion Batteries

Among the materials utilized for the negative electrodes in Li-ion batteries, there is notable interest in oxides that can undergo reactions with Li+ through processes like intercalation, conversion, or alloying. These oxides exhibit high specific capacities but face challenges related to inadequate mechanical stability. A novel approach to constructing nanocomposites involves the partial oxidation of the tin-containing MAX phase within the Ti3Al(1-x)SnxO2 composition. By employing this strategy, and optimizing the Sn amount and the oxidation process, we have developed composite electrodes comprising Sn/TiOx and MAX phase, demonstrating exceptional durability with over 600 cycles in half cells. These electrodes exhibit charge efficiencies exceeding 99.5% and specific capacities comparable to graphite, surpassing those of lithium titanate (Li4Ti5O12) or MXene-based electrodes. These remarkable electrochemical performances extend to full cell configurations when combined with a low cobalt content layered oxide. The success of these electrodes is elucidated through a thorough chemical, morphological, and structural investigation, revealing the intimate contact between the MAX phase and oxide particles. Throughout the oxidation process, electroactive nanoparticles of TiO2 and Ti(1-y)SnyO2 emerge on the surface of the unreacted MAX phase, which serves both as a conductive agent and a buffer to maintain the mechanical integrity of the oxide during lithiation and de-lithiation cycles.

Scalable Synthesis of Bulk TiO2 Hybrids and Its Li-Storage Properties in “Rocking-Chair” Type Full-Cell Assembly with LiNi0.5Mn1.5O4 Cathode

TiO2 as an anode material in lithium-ion batteries (LIB) has abolished hurdles like irreversibility, cycling stability, rate capability, and energy density, which are vital for electrochemical performance. Conventionally, time-consuming and complex techniques like solvothermal methods are employed to synthesize TiO2. We herein open a new avenue towards a simple, scalable, and eco-friendly synthesis of bulk TiO2 anatase/bronze hybrids from sodium meta-titanate through a facile mechano-chemical and ion-exchange process under different temperature conditions (400, 450, and 500 °C). Structural and morphological features are analyzed through various characterization techniques such as XRD, FE-SEM, HR-TEM, and XPS. The bronze phase’s high reversibility, low redox potential, high current rate performance, and high power capability of the anatase phase make the hybrid attractive for fabricating high power and high energy density Li-ion power packs. The Li insertion/extraction properties are studied in half-cell assembly (Li/TiO2), where all three TiO2 hybrids exhibited promising results with an initial discharge capacity >165 mAh g-1 at a current rate of 0.05 A g-1 along with a capacity retention >90% after 100 cycles. A “rocking-chair” type full-cell configuration with high voltage LiNi0.5Mn1.5O4 cathode is fabricated, in which LNMO/TiO2-400 °C displayed a discharge capacity of ~88 mAh g-1 at a current rate of 0.05 A g-1. Moreover, the full cell exhibited a capacity retention of >70% after 100 cycles with a maximum energy density of 192.75 Wh kg-1. Figure 1

Machine Learning Accelerated Identification of Bifunctional Active Sites in Metal-Organic Framework Derived Metal Oxide Heterostructures for High-Performance Zinc-Air Batteries

The demand for electrochemical energy storage (ESS) systems and their market size has drastically increased in many applications ranging from portable devices through electric vehicles to large-scale grid systems over the past decades. Yet, a more advanced ESS is required due to the safety issues and limited energy density of currently commercialized lithium-ion batteries (LIBs) for wide and matured applications. As a solution to this challenge, zinc-air batteries (ZABs) have gained tremendous attention due to their high energy density, low cost, environmental friendliness, and much lower fire risk characteristics. ZABs utilize oxygen from the atmosphere at their cathode during discharge, where the atmospheric oxygen is reduced to hydroxide via an oxygen reduction reaction (ORR). On the other hand, hydroxide is released as oxygen via oxygen evolution reaction (OER) during charge. The fact that oxygen is drawn directly from the air enables high gravimetric and volumetric energy densities of ZABs compared to those of commercial LIBs. However, the sluggish kinetics of the four-electron transfer steps in ORR and the mass transport of oxygen in OER remain major challenges for the practical application of ZABs. Meanwhile, precious metal-based catalysts such as Pt/C and RuO2 are known to have good catalytic activity towards ORR and OER. However, the integration of different catalysts into the same cathode is very difficult. Additionally, the high cost and natural scarcity of novel metals limit their usage for practical applications.We synthesized a bifunctional CoO/Mn3O4 heterostructure (CMH) OER/ORR electrocatalyst which was derived from metal-organic framework (MOF) for excellent activities in ZABs. The CMH cathode exhibited high ORR and OER performances, as demonstrated by the higher ORR current density than that of the Pt/C catalyst as well as the low OER overpotential exceeding those of the RuO2 catalyst. Remarkably, atomic structures of the CMH were elucidated using global optimization of genetic algorithm integrated with the machine learning force field. By adopting first-principles electronic structure calculations, we further revealed the charge transfer and active sites for both reactions in the identified heterojunction. Furthermore, assembling CMH cathode and Zn metal anode into a ZAB full-cell configuration achieves a ~5.5-fold higher energy density of 879 Wh kg-1 exceeding those of commercial lithium-ion batteries (LIBs), a high-discharge outstanding power density that is 1.39 times higher than novel metal catalysts, and robust cycle stability with negligible voltage decay which is far superior to that of benchmark Pt/C+RuO2 electrocatalysts.

Enhancing low-temperature lithium-ion battery performance under high-rate conditions with niobium oxides

Low-temperature operation (−20 °C and below) under high-rate conditions is a critical deficiency for lithium-ion batteries. To achieve size, weight, and power requirements tailored for demanding applications, novel materials are needed to sustain high performance. In the present study, we synthesize a series of niobate anode materials (Nb2O5, Nb2O5–x, and Nb12O29) and tailor their particle size, defect nature, and electrical/ionic conductivity to enable high-performance operation at −20 °C under high-rate conditions (1.2C–2C). When paired with lithium manganese oxide (LMO) in a full-cell configuration, the Nb2O5–x-based full-cells achieve high-rate capability (∼90 mAh/g up to 2C cycling rate at −20 °C) and great long-term stability (>98% retention up to 50 cycles at −20 °C). During a simulated 30 min duty cycling test synthesized from measured data from an actual drone flight (continuous range of 1.2C–2C cycling rates), the Nb2O5–x||LMO cell enables full discharge at −20 °C, with only a 0.3 V voltage drop when compared to duty cycling at room temperature. The work presented herein demonstrates the future possibilities of expanding the operational capabilities of lithium-ion batteries.

Nonsolvating Fluoroaromatic Cosolvent Enabled Long-Term Cycling of High-Voltage Lithium-Ion Batteries with Organosulfur Electrolytes.

The structure-activity relationships of nonsolvating cosolvents for organosulfur-based electrolyte systems were revealed. The performance of nonsolvating dilutant fluorobenzene (FB) was compared to various fluorinated ether dilutants in high-voltage electrolytes containing a concentration of 1.2 M LiPF6 dissolved in fluoroethylene carbonate (FEC), ethyl methyl sulfone (EMS), and the dilutant. In a high-voltage and high-loading LiNi0.8Mn0.1Co0.1O2 (NMC811) full cell configuration, the organosulfur-based electrolyte containing FB dilutant enabled superior electrochemical performance compared to the electrolytes using other nonsolvating fluorinated ether formulations. Moreover, the FB-containing electrolyte exhibited the highest ionic conductivity and lowest viscosity among all organosulfur-based electrolytes containing nonsolvating dilutant. These improvements are attributed to the enhanced physical properties of electrolyte and lithium-ion mobility. Furthermore, by employing first-principles simulations, the observed suppression of side reactions at high voltage is linked to FB's lower reactivity toward singlet dioxygen, which is likely produced at the NMC interface. Overall, FB is considered an excellent diluent that does not impede cell operation by mass decomposition at the cathode.

Engineering interleaved large and small Na4MnV(PO4)3@NC microspheres cathode towards high performance sodium ion batteries

The booming consumption of energy storage devices spontaneously accelerates the urgent development of robust cathode materials for sodium-ion batteries (SIBs). In view of this, the sodium superionic conductor Na4MnV(PO4)3 (NMVP), with considerable energy density of 425 Wh kg−1, has become the focus in SIB research. Despite this, the performance of NMVP is substantially compromised by Jahn-Teller distortion of Mn3+ ions in conjunction with inherently limited electronic conductivity. In order to address this limitation, this study introduces a series of N-doped carbon (NC) coated NMVP materials with interleaved large and small microsphere morphology. Of particular note, the optimized NMVP-NC2 shows the most excellent performance, maintaining a capacity of 65.7 mAh g−1 at 5C over 500 cycles. A full cell configuration employing an NMVP-NC2 cathode and a commercial hard carbon (HC) anode manifests commendable circular stability with a capacity of 80.7 mAh g−1 underneath 100 cycles at 1C, with an impressive 95.3 % capacity preservation. This distinctive architecture imparts the materials with a high tap density and a relatively low surface area, which is beneficial to the industrial employment. In addition, density functional theory (DFT) calculations indicate that the NC regulation significantly narrows the NMVP's bandgap and facilitates electron transfer, thereby accelerating electron/ion transport kinetics. The NC coating approach combined with large-scale spray drying tactic in this work offers a clear strategy to industrialize NMVP cathode towards high-performance SIBs.

Multifunctional-Element doping of NASICON-Structured cathode enables High-Rate and stable sodium storage

The NASICON cathode of sodium ion battery (SIB) exhibits a stable structure and good electrochemical performance. Na3V2(PO4)3 (NVP), as a typical NASICON cathode, has been widely used in SIBs due to its high capacity and long cycle life. However, the high proportion of vanadium in NVP escalates its cost, which deviates from the initial objective of affordable sodium-ion batteries. In this work, a multifunctional-element substitution of vanadium sites in NVP is introduced by the cost-effective transition metals (Mn and Al), which optimizes the host structure, promotes the transmission of sodium ions and improves the cycle stability. The introduction of Mn can enhance its electrochemical activity and increase the reaction potential, and the doping of Al can improve structural support and cycle stability by the enhanced covalent skeleton. It was found that the Na3.7VAl0.3Mn0.7(PO4)3 cathode shows a high capacity of 87.77 mAh g−1 even at 40C (93.2 % retention compared to 1C), and the capacity retention reaches 96.33 % after 1000 cycles at 2C. In-situ XRD analysis demonstrate that the Na3.7VAl0.3Mn0.7(PO4)3 cathode exhibits a solid solution reaction mechanism instead of the previous two-phase transformation process during the Na+ (de)insertion. Furthermore, we conducted assessments on the efficacy of diverse phosphate cathodes within a coin-type full-cell configuration, which initially exhibits a high energy density of 343.9 Wh kg−1 and excellent capacity retention of 91.58 % after 150 cycles at 0.5C. These characteristics position it as a promising candidate for NASICON cathode materials in the field of research and development.

Establishing Li-acetylide (Li2C2) as functional element in solid-electrolyte interphases in lithium-ion batteries

Previously, lithium-acetylide (Li2C2) had been identified as electrolyte degradation product on lithium-metal based electrodes using Raman spectroscopy. This raised the question, if Li2C2 is also be formed on graphitic electrodes in lithium-ion batteries without lithium metal present. In order to shed light on this research question, we performed a series of in situ Raman experiments with graphitic electrodes in half- and full-cell configuration. The recorded cell potential dependent spectra clearly prove the presence of Li2C2 in the lithiated state of the electrodes, but the according peak vanishes when delithiating. This observation indicates a somewhat reversible process involving Li2C2. Several chemical/electrochemical reactions are in question to contribute to this effect. With respect to its properties and potential role in the solid-electrolyte interphase (SEI) DFT calculations of Li2C2-nanoclusters were performed, which revealed an exceptionally low energy band gap, hence a remarkable electric conductivity. In conjunction with a relatively high ionic conductivity, Li2C2 appears to play a key role in the degradation of lithium-ion batteries, which had not yet been revealed nor taken into account in simulations of the interphase.