Surface-controlled sodium-ion storage mechanism of Li4Ti5O12 anode

Insight on electrochemical charge storage behavior of naturally surface oxidized amorphous NiCuCoB nanosheets

Exploring the effect of electrolyte on charge storage mechanisms in sustainable supercapacitor electrodes from sugarcane leaf-derived porous activated carbon.

Li-ion batteries with LiFePO4 cathode and Li4 Ti5 O12 anode show promise for storing renewable energy. However, their low output voltage results in a low energy density. In contrast, dual-ion batteries with graphite cathode and Li4 Ti5 O12 anode can achieve a high output voltage of >3.0 V. In this study, mesocarbon microbeads (MCMB)@LiFePO4 ||Li4 Ti5 O12 dual-ion batteries are developed to address these issues. In the cathode, MCMB improves the conductivity of LiFePO4 and increases the output voltage by the intercalation of anions in the cell voltage range of 2.1-3.5 V. Moreover, the LiFePO4 shell sustains the structural integrity of MCMB and generates in situ a cathode-electrolyte interphase (CEI) with rich LiF. Owing to these unique compositional and structural features, MCMB@LiFePO4 ||Li4 Ti5 O12 manifests much better electrochemical performance than LiFePO4 ||Li4 Ti5 O12 and MCMB||Li4 Ti5 O12 . It sustains 89.6 % of the initial capacity after 1200 cycles at 0.2 A g-1 and achieves a specific energy up to 128 Wh kg-1 at 179 W kg-1 .

Ti, F Codoped Sodium Manganate of Layered P2-Na _0.7 MnO _2.05 Cathode for High Capacity and Long-Life Sodium-Ion Battery

Developing high-performance electrode materials with high energy and long-term cycling stability is a hot topic and of great importance for sodium ion batteries (SIBs). In this work, a highly porous carbon/tin sulfide aerogel with a "skeleton/skin" morphology (SSC@SnS2) has been developed and further used as a binder-free anode for SIBs. This SSC@SnS2 electrode delivers a high specific capacity of 612 mA h g-1 at 0.1 A g-1, a good rate capability, and a long-term cycling stability up to 1000 times with an average Coulombic efficiency of ∼99.9%. Meanwhile, this SSC@SnS2 aerogel also achieves a stable cycling performance even at a high current density up to 5.0 A g-1. The fast-yet-stable sodium ion storage performance of the prepared SSC@SnS2 aerogel can be ascribed to the reasons that (i) the carbon nanofiber/graphene skeleton provides unimpeded pathways for the rapid transfer of electrons; (ii) thin SnS2 skin with nonaggregated morphology can provide a great number of active sites for sodium ion storage; (iii) the porous structure of the SSC@SnS2 aerogel ensures a rapid penetration of electrolyte and can further accommodate the volume expansion of active SnS2 nanoflakes; and (iv) the intermediate product of Na15Sn4 alloy contributes greatly to the sodium ion storage performance of the SSC@SnS2 aerogel. The excellent electrochemical performances coupling with the unique structural features of this SSC@SnS2 aerogel make it a promising anode candidate for SIBs.

Aqueous Zn batteries (AZBs) offer many advantages over state-of-the-art Li-ion batteries for grid-scale energy applications due to their low cost, high raw material abundance, and inherent safety from using aqueous electrolytes 1. Cathode development is the main factor limiting the commercialization of AZBs. Transition-metal oxides (TMOs), including V2O5 and MnO2, are considered the current leading cathode candidates, citing high theoretical capacities and rate capabilities 2. However, the TMOs suffer from poor practical capacity and capacity retention. There is also a debate over charge storage mechanisms, specifically the competition between H+ and Zn2+ intercalation 3. This debate inhibits the design of high-performance cathode materials by reducing the ability to optimize materials for their specific charge-storage and degradation mechanisms. To address this, we utilized operando mechanical experiments to elucidate how charge-storage mechanisms impact electrochemical performance. This study used operando digital image correlation (DIC) and multi-beam optical stress sensors (MOSS) to probe strain and stress generation, respectively, in V2O5 cathodes during cycling of aqueous Zn batteries. DIC revealed homogeneous expansion and contraction during battery cycling on free-standing electrode 4. Expansion was observed during discharge, and contraction was observed during charge. Strain derivatives with respect to voltage were taken to correlate the electrochemical and mechanical behaviors. Strain derivative peaks were aligned closely with the CV redox peaks, except for a discharge peak at approximately 1.0 V, which produced a negligible strain response. Cycle-dependent behavior was revealed for both electrochemical and mechanical behaviors, highlighting the activation process for V2O5 electrodes in aqueous media. MOSS, performed with thin-film electrodes on Au-coated cantilevers, yielded compressive stress generation during discharge and tensile stress generation during charge. Lower voltages produced greater stress than higher voltages per unit current, indicating stress build-up and difficulty in ion-extraction. Operando mechanical measurements have provided critical insights into the charge storage, activation, and degradation mechanisms of V2O5 cathodes in aqueous batteries.REFERENCES1. Wu, T. and Lin, W. Electrochimica Acta 2021, 394, 139134. DOI:10.1016/j.electacta.2021.1391342. Yong, B. et al. Adv. Energy. Mater. 2020, 10, 2002354. DOI: 10.1002/aenm.2020023543. Liu, X.; Dong, X.; and Passerini, S. Journal of Power Sources 2024, 623, 236401. DOI:10.1016/j.jpowsour.2024.2354014. Marckx, B.A.; Maclennan, H.; and Capraz, Ö. Ö. Chem. Biomed. Imaging 2025.

The development of fast-charging lithium-ion batteries (LIBs) is crucial for achieving significant market adoption of electric vehicles (EVs). The successful achievement of fast-charging LIBs depends on efficient charge transfer and the diffusivity of lithium ions. The photo-assisted battery system exhibits promising fast-charging properties. Previous research has shown that direct exposure to white light can induce a more oxidized center in a spinel LiMn2O4 (LMO) cathode, accelerating its charging rate.[ 1] Recently, our group found that illumination with red light on an operating LMO cathode induces an Mn d-d electron excitation, simultaneously shrinks the Mn-Mn lattice, and facilitates faster delithiation of the LMO cathode.[ 2] Consequently, the charging time of the battery decreases. This encourages us to consider whether the photon energy from a specific wavelength of light can also enhance the lithiation process on the anode side. Spinel Li4Ti5O12 (LTO) is a promising material for faster-charging anodes due to its small volume charge and high-rate capability in lithium intercalation. However, the system displays slow lithium diffusivity due to poor bulk ionic conductivity. To examine the photon effect of light on these anodes, we demonstrate the photo-accelerated fast-charging (lithiation process) mechanism with an LTO spinel anode.The thin film LTO's energy band gap (Eg), approximately 3.4 eV, was determined through intense UV-visible (UV-Vis) absorption spectrum analysis, assessed in a transmission mode employing Tauc’s Law. This indicates that an LED light with photon energy around 3.4 eV might trigger rapid charging by exciting electron transfer to the T-t2g band. To explore the impact of light on the fast-charging behavior of the LTO electrode, current was measured while applying a constant voltage of 1.2 V. During the 20-minute chronoamperometry experiment, utilizing the 3.4 eV UV LED to illuminate the cell resulted in a progressive increase in current. This current increase peaked at approximately 200s, leading to a maximum average capacity increase of 13 mA h g-1. This suggests that UV illumination accelerates the lithiation process compared to the dark state, particularly favoring the early lithiation stage. Subsequently, a red LED emitting 2 eV photon energy was used to illuminate the same cell, resulting in no discernible change in current levels compared to the dark state. Electrochemical impedance spectroscopy (EIS) further revealed a significant reduction in charge transfer resistance of the window cell when illuminated with UV light compared to both the dark state and red illumination. This alteration in electrode reaction kinetics at the interface suggests a distinct influence of different light wavelengths on the charging process.In addition to assessing charge transfer at the electrode interface, galvanostatic intermittent titration technique (GITT) analysis was conducted at a 2 C rate to further elucidate diffusion within the LTO electrode. The GITT curves reveal that the diffusion of Li+ ions was approximately 1.3 times faster when the cell was illuminated by UV light compared to dark conditions. Consequently, we deduce that photo-accelerated fast charging can also occur during the lithiation process (reduction reaction) of anode materials, driven by optical forces.To delve into the underlying mechanisms, we conducted first-principles density functional theory (DFT) calculations. The outcomes revealed that the generation of additional electrons in LTO results in a reduction in the bandgap and shifts the Fermi level above the conduction band minimum, effectively transforming LTO into an active conductor of electricity. These calculations indicate that UV light illumination has the capability to surmount the bandgap of LTO, generating electron-hole pairs and thereby facilitating charge transfer and lithium-ion diffusion.In conclusion, our study showcased that UV light illumination on the LTO anode can lead to a faster charging speed of approximately 17% compared to dark conditions. We posit that the observed phenomenon of photo-accelerated fast charging in LTO is linked to the formation of electron-hole pairs in intrinsically wide-bandgap insulators or semiconducting materials. This discovery holds considerable implications for the advancement of fast charging technologies for lithium-ion batteries, potentially mitigating range anxiety concerns and facilitating the widespread adoption of electric vehicles.Acknowledgments: This work was supported by funding from Royal Dutch Shell plc. Argonne National Laboratory operates under contract no. DE-AC02-06CH11357 with the U.S. Department of Energy Office of Science. We gratefully acknowledge use of the Bebop or Swing or Blues cluster in the Laboratory Computing Resource Center at Argonne National Laboratory and supported by the U.S. Department of Energy Office of Science.Reference[1] A. Lee et al., Nat. Commun., 10, 4946 (2019).[2] J. Lipton et al., Cell Reports Physical Science, 3, 101051 (2022).

Mechanisms of Charge Storage in Nanoparticulate TiO2 and Li4Ti5O12 Anodes: New Insights from Scan rate-dependent Cyclic Voltammetry

Charge storage behavior in nitride nanomaterials depends on a number of particle properties and also on the nature of the electrode (1-9). Vanadium nitride is a promising supercapacitor material on account of pseudocapacitance arising from the surface oxide/oxynitride phase interactions. We have previously reported excellent charge storage behavior of nanoparticulate vanadium nitride on account of the surface reactions occurring on the surface of the oxide exo-shell. Vanadium oxide is a superior pseudocapacitor material but suffers from poor electronic conductivity(10). Forming a thin surface oxide layer on nanoparticle nitrides yields the benefits of the charge storage along with charge storage occurring in the nitride core itself. However, there is evidence showing that the surface oxide suffers from instability in highly alkaline solutions on account of side-reactions. In addition, the core nitride itself becomes a poor conductor when prepared as fine nanoparticles (<10 nm)(3). In this study, we tailor nitride nanoparticles to engineer architectures similar to that shown in Figure 1by the use of suitable dopants. By using wet chemical procedures, we generate a number of doped nitrides with doped surface oxide structure. We use ab-initio first principle studies to guide our dopant selection with improved electronic conductivity of surface oxide/core nitride and stability of surface oxide being parameters driving our dopant selection. We demonstrate in this study doped VN with superior electronic conductivity, high capacity and long cycle life. In-depth surface characterization using XPS and electrochemical impedance spectroscopy (EIS) to probe change in charge-storage mechanisms are conducted herein to obtain fundamental understanding into the nature of the various doped nitride materials. Change in nanoparticle morphology and surface composition are also examined and related to charge storage behavior. Results of these studies will be presented and discussed.

Spinel Li4Ti5O12 (LTO) is an attractive candidate for negative electrode materials of lithium ion battery because the LTO anode shows the high rate capability, long cycle life, outstanding safety characteristics, and a flat insertion/extraction potential of at 1.5 V vs. Li+/Li. The 4V-class cathode (such as LiCoO2, LiNi1/3Mn1/3Co1/3O2, and LiMn2O4) / LTO battery has a low working voltage of about 2.5 V, leading to its low energy density. Some researchers have studied the LiNi0.5Mn1.5O4 (LNMO) / LTO battery system, because LNMO cathode offers a high operating potential at 4.7 V, which increases the working voltage of the battery using the LTO anode to 3.1 V [1] [2] [3]. Amine et al. reported that the negative limited LNMO / LTO cell showed a high rate capability and long cycle life at room temperature [1]. However, we found that the negative-limited LNMO /LTO battery showed a poor cycle characteristic at 50 ℃ (figure1-a). In this presentation, we aim to clarify the degradation mechanism of the negative-limited LNMO / LTO battery in order to improve the cycle life at a high temperature. For this purpose, we disassembled the LNMO / LTO cells after the cycle test at 50 ℃ and extracted the electrodes and electrolyte. The extracted LNMO / Li-metal half-cell and the extracted LTO / Li-metal half-cell were assembled and tested. It was found that the capacity of the LNMO electrode did not decrease. On the other hand, the capacity of the LTO electrode decreased. It is revealed that the degradation of the negative-limited LNMO/LTO battery was caused by the decline of the LTO anode capacity. The XPS spectra of the LTO electrode indicated that LiF covered around the LTO materials and caused its capacity degradation. To reveal the generation pathway of LiF, the extracted electrolyte was analyzed by GC-MS, LC-MS/MS and 19F-NMR. The results revealed that the reduction reaction of the chain-like carbonate such as dimethyl carbonate and the ring-opening reaction of the cyclic carbonate such as ethylene carbonate caused the LiF generation. Especially, the lithium alkoxide generated by the ring-opening reaction of the cyclic carbonate accelerated the LiF generation reaction. The use of the electrolyte containing only chain-like carbonate as a solvent significantly improved the cycle characteristics at 50 ℃ (figure1-b).

Effect of solid electrolyte interface (SEI) film on cyclic performance of Li4Ti5O12 anodes for Li ion batteries

Sodium-ion batteries (SIBs) toward large-scale energy storage applications has fascinated researchers in recent years owing to the low cost, environmental friendliness, and inestimable abundance. The similar chemical and electrochemical properties of sodium and lithium make sodium an easy substitute for lithium in lithium-ion batteries. However, the main issues of limited cycle life, low energy density, and poor power density hamper the commercialization process. In the last few years, the development of electrode materials for SIBs has been dedicated to improving sodium storage capacities, high energy density, and long cycle life. The insertion type spinel Li4 Ti5 O12 (LTO) possesses "zero-strain" behavior that offers the best cycle life performance among all reported oxide-based anodes, displaying a capacity of 155 mAh g-1 via a three-phase separation mechanism, and competing for future topmost high energy anode for SIBs. Recent reports offer improvement of overall electrode performance through carbon coating, doping, composites with metal oxides, and surface modification techniques, etc. Further, LTO anode with its structure and properties for SIBs is described and effective methods to improve the LTO performance are discussed in both half-cell and practical configuration, i.e., full-cell, along with future perspectives and solutions to promote its use.

The most popular anode material in commercial Li-ion batteries is still graphite. However, its low intercalation potential is close to that of lithium, which results in the dendritic growth of lithium at its surface, and the formation of a passivation film that limits the rate capability and may result in safety hazards. High-performance anodes are thus needed. In this context, lithium titanite oxide (LTO) has attracted attention as this anode material has important advantages. Due to its higher lithium intercalation potential (1.55 V vs. Li+/Li), the dendritic deposition of lithium is avoided, and the safety is increased. In addition, LTO is a zero-strain material, as the volume change upon lithiation-delithiation is negligible, which increases the cycle life of the battery. Finally, the diffusion coefficient of Li+ in LTO (2 × 10-8 cm2 s-1) is larger than in graphite, which, added to the fact that the dendritic effect is avoided, increases importantly the rate capability. The LTO anode has two drawbacks. The energy density of the cells equipped with LTO anode is lower compared with the same cells with graphite anode, because the capacity of LTO is limited to 175 mAh g-1, and because of the higher redox potential. The main drawback, however, is the low electrical conductivity (10-13 S cm-1) and ionic conductivity (10-13-10-9 cm2 s-1). Different strategies have been used to address this drawback: nano-structuration of LTO to reduce the path of Li+ ions and electrons inside LTO, ion doping, and incorporation of conductive nanomaterials. The synthesis of LTO with the appropriate structure and the optimized doping and the synthesis of composites incorporating conductive materials is thus the key to achieving high-rate capability. That is why a variety of synthesis recipes have been published on the LTO-based anodes. The progress in the synthesis of LTO-based anodes in recent years is such that LTO is now considered a substitute for graphite in lithium-ion batteries for many applications, including electric cars and energy storage to solve intermittence problems of wind mills and photovoltaic plants. In this review, we examine the different techniques performed to fabricate LTO nanostructures. Details of the synthesis recipes and their relation to electrochemical performance are reported, allowing the extraction of the most powerful synthesis processes in relation to the recent experimental results.

Reasonably designing and synthesizing advanced electrode materials is significant to enhance the electrochemical performance of lithium ion batteries (LIBs). Herein, a metal-organic framework (MOF, Mil-125) was used as a precursor and template to successfully synthesize the porous mooncake-shaped Li4 Ti5 O12 (LTO) anode material assembled from nanoparticles. Even more critical, SmF3 was used to modify the prepared porous mooncake-shaped LTO material. The SmF3 -modified LTO maintained a porous mooncake-shaped structure with a large specific surface area, and the SmF3 nanoparticles were observed to be attach on the surface of the LTO material. It has been proven that the SmF3 modification can further facilitate the transition from Ti4+ to Ti3+ , reduce the polarization of electrode, decrease charge transfer impedance (Rct ) and solid electrolyte interface impedance (Rsei ), and increase the lithium ion diffusion coefficient (DLi ), thereby enhancing the electrochemical performance of LTO. Therefore, the porous mooncake-shaped LTO modified using 2 wt % SmF3 displays a large specific discharge capacity of 143.8 mAh g-1 with an increment of 79.16 % compared to pure LTO at a high rate of 10 C (1 C=170 mAh g-1 ), and shows a high retention rate of 96.4 % after 500 cycles at 5 C-rate.

Two dimensional (2D) materials such as graphene have attracted tremendous interest and have shown promising potential in various applications due to their unique physical structure and properties. Another new class of 2D materials, a group of early transition metal carbides and/or carbonitrides, called MXene, have been studied and reported recently. MXenes are chemically derived from layered Mn+1AXn or MAX phases, where M is early transition metal, A is an A-group element (mainly groups 13 and 14), X is C and/or N, and n=1,2, and 3. Since discovery of the first MXene (Ti3C2) in 2011, more than 10 new MXenes have been synthesized and demonstrated its interesting and unique properties in many applications. It has been shown that MXenes have promising potential in electrochemical energy storage applications such as lithium ion batteries (LIBs) and electrochemical capacitors (ECs), due to their high electrical conductivity, good structural/chemical stability, and large surface areas. Recently, MXene application studies are expanding to other battery systems such as Na-ion batteries (NIBs). The growing concerns on the cost and resource limit of lithium for large scale applications have triggered the development of NIBs as an alternative battery system to LIBs for large scale energy storage applications due to their potentially low-cost and natural abundance. Moreover, the accumulated knowledge and technology of LIBs enables fast-advancements of NIBs research since the operating principles of the NIBs are similar to that of “rocking-chair” mechanism in LIBs. Although many concepts can be adopted from LIB in NIB research, the electrochemistry of NIBs turns out to be different in many aspects requiring new design of electrode materials and electrolyte for improving and/or optimizing performance of NIBs. In particular, Na+ has a larger radius than Li+, which directly affects the mass transport and storage in the electrochemical reaction. This makes many of current LIB anode materials, such as graphite, unsuitable for NIBs. In this regards, the laminar nature of MXenes bonded by weak van der walls forces and its inherent interlayer spacing are very attractive as anode materials for NIBs. However, most of studies on the electrochemical behavior of MXenes as anode materials for NIBs are just at the theoretical estimation only without much experimental support. In this study, we present a systematic study on the electrochemical properties and their charge storage mechanisms of V2C and Nb2C MXenes as anode materials for NIBs. X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) were used in both ex situ and in situ way to look at the structural changes during electrochemical cycling. By utilizing such combined X-ray techniques, we are able to get better understanding of structural/electronic structure changes of MXenes and their related charge storage behavior during sodiation/desodiation process. A systematic comparison of electrochemical properties and charge storage mechanism for MXenes between NIBs and LIBs as well as the approaches to improve them will also be discussed. Acknowledgement The work done at Brookhaven National Lab was supported by the U.S. Department of Energy, the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies, under Contract Number DE-SC0012704. The work performed at Drexel University was supported by the Office of Electricity Delivery and Energy Reliability, Energy Storage Systems Program, through Sandia National Laboratories. The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.