Advanced Raman spectroscopy for battery applications: Materials characterization and operando measurements

Strategies for formulation optimization of composite positive electrodes for lithium ion batteries based on layered oxide, spinel, and olivine-type active materials

Currently, there exist various materials surface analysis and characterization techniques, but it is difficult to measure their component distribution, in particular from a three-dimensional prospect. In this paper, the component distribution of nano-carbon materials in 2D and 3D views were both characterized via Time of Flight-Secondary Ion Mass Spectrometer (TOF-SIMS). The results indicate that TOF-SIMS could provide comprehensive information about component distribution, which is expected to be developed as an advanced technology in material analysis and characterization to the research community.

Carbon based nanomaterials have been widely used as cathode materials for Li-O2 batteries because of their high conductivity, large surface area, and good ORR catalytic activity. However, instability of carbon under Li-O2 operation poses problems. During recharge, carbon can decompose to form lithium carbonate at high charging potential1, but also react chemically with the discharge product Li2O2 2. Metal oxides, like MnO2 and RuO2, have been investigated as cathode catalysts in Li-O2 batteries3. In this study, MnO2 nanostructure is electrodeposited on stainless steel mesh and applied as a carbon-free and binder-free cathode for non-aqueous Li-O2 battery. To maintain good adhesion and electrical contact between deposited layer and the substrate, the mesh is pre-treated. Benefiting from enhanced electronic contact and large surface area of MnO2, the electrochemical performance is improved. Material characterization and electrochemical impedance spectroscopy (EIS) technique are also utilized to systematically study the electrochemical processes of these carbon-free MnO2-based electrodes.

Increasing awareness of environmental pollution and requirement of reliable energy are driving to develop various energy storage systems. Among them, rechargeable batteries play a key role in our modern society. "Building better batteries" remains an ongoing process to cater diverse energy demands starting from small-scale consumer electronics to large-scale automobiles and grid storage. Constantly promoting the development of battery technologies towards better, cheaper and safer properties is the persistent mission of scientific researchers. Due to the similar working principle to Li-ion batteries, abundant resource advantages, and mature fabrication technologies, Na-ion batteries (NIBs) have become a rising star and aroused a great deal of interest particularly for the application in the grid electrical energy storage. To realize the goal, the scientific community is making unremitting endeavors in the search for more efficient, reliable and economical materials and technologies, where the new designing and discovering, the endless improvements and innovations, as well as the proposed solutions and strategies are the best proof. This special issue presents a body of work discussing the important topics in NIB research: i) the synthetic condition- and composition-dependent layered oxides, ii) the multielectron reactions of polyanionic materials, iii) the application of Prussian blue analogs in organic or aqueous electrolytes, iv) the synthesis of anode materials and understanding of storage mechanism, and v) the effect of salt concentration on electrolyte and electrode property. This issue begins with a research news of sodium-oxygen batteries to review the cell chemistry and reaction mechanism, and consists of three communications, five reviews and nine research papers to introduce the above-mentioned topics, discuss them in detail, and summarize recent advances. As one of the main components of NIBs, cathode materials play a key role in overall performance, and consequently capture considerable interest. Among them, layered metal oxides, polyanionic compounds and Prussian blue analogs have been intensively examined due to their respective advantages. Four papers cover sodium layered oxides (investigating the synthetic condition, element doping and structure design for the material modification), six papers involve polyanionic cathodes (with regard to the versatile skeleton, multielectron reaction and tunable redox potential to realize high power or high energy density batteries), and two papers concern Prussian blue analogs (possessing rigid open framework with large interstitial sites and capable of applying in both organic and aqueous electrolytes). Compared with cathode materials, the selection of anode materials suffer from limited options. Two reviews summarize the state-of-the-art achievements of carbonaceous anodes: one aims to help readers comprehensively learn how to fabricate one-element doped and several-elements co-doped carbons to tune the anode performance, and the other intends to demonstrate the sodium storage ability of graphitic carbons with strategies of solvent co-intercalation, graphite expanding and active material compositing. One research paper on the cobalt/chalcogenides in B, N co-doped graphene for sodium storage is a live example combining the main content of the two reviews. Besides, another research paper reports evidence for reversible silicon redox activity by investigating the sodium storage mechanism in silicon oxycarbide. Electrolytes are also crucial to influence the whole performance of battery system. Organic electrolytes containing solvents and salts are still the mostly used type, where the salt-solvent coordination greatly impacts the ionic conductivity, viscosity, electrochemical stability window etc. One research paper systematically investigates the salt concentration on the properties of organic carbonate-based electrolyte and finds that viscosity plays a major role in influencing ionic conductivity rather than ions and molecules' coordination. The best electrolyte should make a good compromise between physicochemical and electrochemical properties. This special issue in Small Methods attempts to offer highlights on the new developments of electrode material design, electrolyte composition optimization, sodium storage mechanism interpretation, and electrochemical performance improvement for NIBs in a broad range. Even there are still many challenges to be resolved, given the facts that important achievements have been realized and over 10 companies in the world start to commercialize this technology, in particular, HiNa Battery Company has successfully installed a Na-ion battery system with a capacity of 30 kW/100 kWh for the energy storage in Liyang city of China (Figure 1). We are sure that NIBs will have promising applications in the future. It has been our pleasure to edit this special issue, and we would like to thank Small Methods editors, particularly, Dr. Guangchen Xu, for proposing the special issue and handling all the papers. We would also express our earnest thanks to all the authors for their commitment and great work, and appreciate all the reviewers who have made excellent contributions to guarantee this high-quality issue for the community.

Sodium-ion batteries (SIBs) have been increasingly studied due to sodium (Na) being an inexpensive ionic resource (Na) and their battery chemistry being similar to that of current lithium-ion batteries (LIBs). However, SIBs have faced substantial challenges in developing high-performance anode materials that can reversibly store Na+ in the host structure. To address these challenges, molybdenum sulfide (MoS2)-based active materials have been considered as promising anodes, owing to the two-dimensional layered structure of MoS2 for stably (de)inserting Na+. Nevertheless, intrinsic issues of MoS2—such as low electronic conductivity and the loss of active S elements after a conversion reaction—have limited the viability of MoS2 in practical SIBs. Here, we report MoS2 embedded in carbon nanofibers encapsulated with a reduced graphene oxide (MoS2@CNFs@rGO) composite for SIB anodes. The MoS2@CNFs@rGO delivered a high capacity of 345.8 mAh g−1 at a current density of 100 mA g−1 for 90 cycles. The CNFs and rGO were synergistically taken into account for providing rapid pathways for electrons and preventing the dissolution of S sources during repetitive conversion reactions. This work offers a new point of view to realize MoS2-based anode materials in practical SIBs.

The success of commercializing sodium-ion batteries is inhibited by the implementation of suitable electrolytes that have economic feasibility and stable electrochemical performance. Organic electrolytes such as Na[ClO4]- or Na[PF6]-including organic solvents, EC, PC, DMC, and DEC, are most widely used to investigate the performance of sodium-ion batteries. These electrolytes are widely accepted because of the analogous studies in LIBs, but their flammability can cause reliability issues. Moreover, the SEI layer composed of sodium cations is known to be inhomogeneous and fragile, giving a higher solubility than that based on lithium cations.(1) In this regard, ionic liquid electrolytes are a drawing huge attention to constructing safe electrochemical devices owing to their unique properties such as low volatility and low flammability. Furthermore, recent studies report ionic liquids show similar electrochemical performance at room temperature to organic electrolytes and better interfacial properties.(2-4) Despite this bright improvement, the cost of ionic liquids drags down the advantage of economical sodium-ion batteries.In this study, ionic liquid and organic liquid electrolytes are mixed to adjust the balance of cost, performance, and safety. The [C3C1pyrr][FSA] (C3C1pyrr+ = N-methyl-N-propylpyrrolidinium) ionic liquid and PC organic solvent are used as mother electrolytes with Na[FSA] (FSA = bis(fluorosulfonyl)amide) and Na[ClO4] salts. The physical and electrochemical properties of the various mixing ratio of those mixture electrolytes are investigated for sodium-ion batteries. These mixture electrolytes improve not only flammability but also show better rate and cycling performance. The detailed electrochemical properties are evaluated by comparing reference electrolytes to clarify the dual salts effect and dual solvents (ionic liquids and organic solvent) effect. This performance will be discussed based on half cell tests using a Na2FeP2O7 positive electrode and full cell tests using a hard carbon negative electrode and a NaCrO2 positive electrode.

A green approach has been used for the synthesis of fluorescent sodium banana peel xanthate Carbon Dot (SBPX C-dot) with the use of yellow banana peels as carbon source. The Carbon Dot were synthesized by hydrothermal treatments. pigments and other low molecular weight hydrocarbons, most of the above materials on reaction with carbon disulphide Banana peel is mostly composed of cellulose (8.4 nmol L-1), pectin (10-21%), hemicellulose (6.4-9.4 %), lignin (6-12%). Banana peel was first treated with 10% NaOH for a day to hydrolyze or digest or disentigrate into the low molecular weight and bigger molecular weight compounds, with a lot of hydroxyl functional groups, which make the Banana peel a potential substrate for the synthesis of Banana Peel Xanthate C-Dot (SBPX C-Dot). The Banana Peel Xanthate C-Dot (SBPX C-Dot) are analyzed and identified by FT-IR, Raman Spectroscopy and UV-Visible spectroscopy. Effect of pH on UV-Visible and Fluorescence Spectroscopy were carried out in the pH range (pH=1-10). Field Emission Scanning Electron Microscopy was used to study the surface morphology. The utility of (SBPX C-Dot) with Carbon Paste to form a Composite Electrode (CCPE) for potentiometric sensing of Hg (II) ion was accomplished in aqueous acetate and chloride medium at different pHs (pH=1-10). Reasonable and selective sensing was observed with CCPE for Hg (II) ion is observed.

The advancement of battery materials has been accelerated by new characterization methods that are capable of probing battery chemistries at various length and time scales. Synchrotron X-ray techniques stand out as one of the most effective methods that allow for nearly nondestructive probing of materials characteristics such as electronic and geometric structures with various depth sensitivities through spectroscopy, scattering, and imaging. In this presentation, we will discuss the state-of-the-art of some X-ray spectroscopic and imaging techniques and their successful applications in gaining fundamental insights into intercalation battery chemistries. We will then provide some examples in lithium ion and sodium ion batteries. Specifically, lithium and sodium layered cathode materials are usually multicomponent transition metal (TM) oxides and each TM plays unique roles in operating the cathode chemistry, e.g., redox activity, structural stabilization, surface passivation. Engineering the three-dimensional (3D) distribution of TM cations in individual primary and secondary particles can take advantage of the depth-dependent charging and passivation mechanisms. This will enable a path towards tuning local TM–O chemical environments and eliminating undesired cathode–electrolyte interfacial reactions that are responsible for capacity fading, voltage decay, and safety hazards. We will then highlight our recent progress in understanding and manipulating the cathode chemistry using the unconventional design principle of 3D heterogeneous chemical distribution and advanced diagnostic tools. The presentation will show that “there is plenty of room at the bottom” by tuning nano/meso scale heterogeneities for stabilizing multicomponent transition metal oxides based cathode chemistry in rechargeable batteries. Finally, we will provide a perspective to elaborate how synchrotron techniques can impact the development of next-generation battery chemistries.

To meet the increasing demands of energy storage, particularly for transportation applications such as plug-in hybrid electric vehicles, researchers will need to develop improved lithium-ion battery electrode materials that exhibit high energy density, high power, better safety, and longer cycle life. The acceleration of materials discovery, synthesis, and optimization will benefit from the combination of both experimental and computational methods. First principles (ab Initio) computational methods have been widely used in materials science and can play an important role in accelerating the development and optimization of new energy storage materials. These methods can prescreen previously unknown compounds and can explain complex phenomena observed with these compounds. Intercalation compounds, where Li(+) ions insert into the host structure without causing significant rearrangement of the original structure, have served as the workhorse for lithium ion rechargeable battery electrodes. Intercalation compounds will also facilitate the development of new battery chemistries such as sodium-ion batteries. During the electrochemical discharge reaction process, the intercalating species travel from the negative to the positive electrode, driving the transition metal ion in the positive electrode to a lower oxidation state, which delivers useful current. Many materials properties change as a function of the intercalating species concentrations (at different state of charge). Therefore, researchers will need to understand and control these dynamic changes to optimize the electrochemical performance of the cell. In this Account, we focus on first-principles computational investigations toward understanding, controlling, and improving the intrinsic properties of five well known high energy density Li intercalation electrode materials: layered oxides (LiMO2), spinel oxides (LiM2O4), olivine phosphates (LiMPO4), silicates-Li2MSiO4, and the tavorite-LiM(XO4)F (M = 3d transition metal elements). For these five classes of materials, we describe the crystal structures, the redox potentials, the ion mobilities, the possible phase transformation mechanisms, and structural stability changes, and the relevance of these properties to the development of high-energy, high-power, low-cost electrochemical systems. These results demonstrate the importance of computational tools in real-world materials development, to optimize or minimize experimental synthesis and testing, and to predict a material's performance under diverse conditions.

The present study reports on a highly rate capable NASICON-structured NaTi2(PO4)3/ reduced graphene oxide (NTP/rGO) composite electrode synthesized by polyol-assisted pyro synthesis for Na-ion batteries (NIBs). X-ray diffraction (XRD) studies confirmed the presence of a rombohedral NaTi2(PO4)3 phase in the composite while Raman spectroscopy studies helped to identify the existence of rGO in the composite. Electron microscopy studies established that NaTi2(PO4)3 nanoparticles of average sizes ranging between 20 and 30 nm were uniformly distributed and embedded on the GO sheets. When tested for sodium storage properties, the obtained NTP/rGO composite electrode registered high rate capacities (95 mAh g-1 at 9.2 C and 78 mAh g-1 at 36.8 C) when compared to that of the NTP/C electrode (~1 mAh g-1 at 9.2 and 36.8 C). The enhanced performance of the composite electrode can be attributed to the nano-sized NaTi2(PO4)3 particles with shorter diffusion path lengths embedded on the rGO sheets with enhanced electrolyte/electrode contact areas that ultimately leads to an improvement in the electrical conductivity at high current densities. Ex-situ XANES studies confirmed reversible Na-ion intercalation/de-intercalation into/from NTP/rGO. The study thus demonstrates that the NaTi2(PO4)3/rGO nanocomposite electrode is a promising candidate for the development of high power/energy density anodes for NIBs.

Biomass carbon micro/nano-structures derived from ramie fibers and corncobs as anode materials for lithium-ion and sodium-ion batteries

Silicon and its oxides are attractive anode materials in energy storage devices, because of their high theoretical Li-storage capacities (Si: ~3580 mA h g− 1; SiO: ~2600 mA h g− 1; and SiO2: ~1680 mA h g− 1), low lithiation potential (<0.5 V vs. Li/Li+), low cost and environmental benignity.1,2 These silicon-based anodes can be used both in traditional lithium ion batteries and in more recent Li-S and Li-O2 batteries as a replacement for the dendrite-forming lithium metal anodes.3 Currently, the most critical challenge is to improve their low initial coulombic efficiency and accommodate the structure degradation and instability of the solid-electrolyte interface caused by the large volume change. Here, we propose a binder-free structured Si/SiO x anode that can tackle the above issues. We introduce a unique electrode fabrication technique based on directly encapsulating Si/SiO x particles into cyclized polyacrylonitrile (PAN) frameworks as a monolithic, multi-core, cross-linking composite electrode. In this composite, the micro-nano Si/SiO x particles reduced by high-energy ball-milling SiO act as active materials, and the cyclized PAN serves both as binders and conductive agents. Owing to the high electrochemical activity of Si/SiO x and the good mechanical resiliency of cyclized PAN, this specific composite structure enhances the utilization efficiency of silicon oxides and accommodates its large volume expansion, as well as its good ionic and electronic conductivity. The cyclized-PAN coating Si/SiO x composite exhibits excellent electrochemical properties, including a high initial reversible capacity (2734 mA h g− 1 with 75% coulombic efficiency), excellent cycle stability (988 mA h g− 1 after 100 cycles), and good rate capability (800 mA h g− 1 at 1 A g− 1rate). Because the composite is naturally abundant and shows such excellent electrochemical performance, it is a promising anode candidate material for lithium-ion batteries. The binder-free architectural design also provides an effective way to prepare other monolithic electrode materials for advanced lithium-ion batteries. In Fig. 1A, the composite electrode exhibited a monolithic structure with coarse surface morphology, many Si/SiO x particles were exposed onto the electrode surface, and several cracks were caused by the volume contraction of the PAN’s cyclization. These specific structural properties might guarantee the infiltration of the electrolyte into the bulk electrode, which was beneficial for charge transfer and ion transport. In Fig. 1B, the Raman spectra showed a sharp band at 502 cm− 1 which was attributed to the crystalline Si, indicating that nano-Si were dispersed into silicon oxides matrices, another two bands at 1356 and 1592 cm− 1 were attributed to the D-band (disorder-induced phonon mode) and G-band (graphite band), respectively, of delocalized sp2 π bonds in nitrogen doped carbon. In Fig. 1C, the composite electrode showed a weak reduction peak at 0.52 V, which indicated that the capacity loss results from the formation of SEI, and that the reduction of SiO to Si could be negligible in the composite electrode. This was due to the existence of cyclized PAN layer coating on active materials that hindered the decomposition of the electrolyte, as well as the mechanochemical reduction of SiO to nano-Si oxides could reduce the formation of Li2O and Li-silicates. Fig. 1D showed the charge–discharge profiles of the composite electrode at the current density of 0.1 A g− 1. It delivered a high initial discharge capacity of 2733.7 mA h g− 1 and a charge capacity of 2046.6 mA h g− 1, with 75% coulombic efficiency. The second discharge capacity could maintain at 2051.2 mA h g− 1. After 100 cycles (Fig. 1E), the composite electrode revealed a high capacity retention of 987.8 mA h g− 1, with an average coulombic efficiency of 98.5% for 100 cycles. Note that the cycle performance of the composite electrode was much better than that of the pristine SiO electrode. In summary, a binder-free anode of cyclized-PAN coating Si/SiO x composite was designed, and it exhibited excellent electrochemical properties in lithium ion batteries. This unique structural design would provide new avenues for the rational engineering of electrode materials for advanced lithium ion batteries and other electrochemical devices. References 1 J.-I. Lee and S. Park, Nano Energy, 2013, 2, 146−152. 2 J. Wang, W. Bao, L. Ma, G. Tan, Y. Su, S. Chen, F. Wu, J. Lu and K. Amine, ChemSusChem, 2015, 8, 4073−4080. 3 N. Liu, Z. Lu, J. Zhao, M. T. McDowell, H.-W. Lee, W. Zhao and Y. Cui, Nat. Nanotechnol., 2014, 9, 187–192. Fig. 1 (A) SEM image, (B) Raman spectrum, (C) Cyclic voltammograms, and (D) Charge–discharge profiles of the composite electrode, and (E) Cycle performance of the pristine SiO electrode and composite electrode at a current density of 0.1 A g−1. Figure 1

This thesis was aimed at investigating the physical-chemical properties and the behaviour in physiological environment of two classes of bioceramics: calcium silicate-based dental cements and alumina-based femoral heads for hip joint prostheses. The material characterization was performed using spectroscopic techniques such as that allow to obtain information on the molecular structure of the species and phases present in the analyzed samples. Raman, infrared and fluorescence spectroscopy was principally used. Calcium silicate cements, such as MTA (Mineral Trioxide Aggregate), are hydraulic materials that can set in presence of water: this characteristic makes them suitable for oral surgery and in particular as root-end filling materials. With the aim to improve the properties of commercial MTA cements, several MTA-based experimental formulations have been tested with regard to bioactivity (i.e. apatite forming ability) upon ageing in simulated body fluids. The formation of a bone-like apatite layer may support the integration in bone tissue and represents an essential requirement for osteoconduction and osteoinduction. The spectroscopic studies demonstrated that the experimental materials under study had a good bioactivity and were able to remineralize demineralized dentin. . Bioceramics thanks to their excellent mechanical properties and chemical resistance, are widely used as alternative to polymer (UHMWPE) and metal alloys (Cr-Co) for hip-joint prostesis. In order to investigate the in vivo wear mechanisms of three different generations of commercial bioceramics femoral heads (Biolox®, Biolox® forte, and Biolox® delta), fluorescence and Raman spectroscopy were used to investigate the surface properties and residual stresses of retrieved implants. Spectroscopic results suggested different wear mechanisms in the three sets of retrievals. Since Biolox® delta is a relatively recent material, the Raman results on its retrievals has been reported for the first time allowing to validate the in vitro ageing protocols proposed in the literature to simulate the effects of the in vivo wear.

Advances in lithium-ion battery (LIB) technology have taken center stage over the past decade due to their high energy densities compared to other battery chemistries. However, resource limitations are expected to increase production costs, prompting interest in alternative technologies. Sodium-ion batteries (SIBs), which share similar chemistry with LIBs but rely on more abundant elements, have emerged as promising next-generation energy storage solutions. In this context, solid electrolyte materials are crucial for enabling safe and efficient sodium batteries by mitigating the risks associated with flammable liquid electrolytes. Sodium-Super-Ionic-Conductor (NASICON) structures like Na₃Zr₂Si₂PO₁₂ (NZSP) have attracted considerable attention for their excellent ionic conductivity and thermal stability. However, their practical use is often hindered by inherent porosity and low density, which degrade ionic conductivity and electrochemical stability, ultimately limiting battery performance.In this study, we significantly enhance the performance of NZSP solid electrolyte materials tailored for All-Solid-State batteries (ASSBs) through a successful densification process. By introducing a densification agent that interacts effectively with the sodium-ion conducting matrix, we achieved notable improvements in both material compactness and ionic transport properties. The densified sample exhibited an impressive room-temperature ionic conductivity of 8.4 × 10⁻⁴ S/cm and attained ~98% of the theoretical density, resulting in a robust and mechanically stable electrolyte structure. This process also reduced porosity and grain boundary resistance, enabling faster and more efficient sodium-ion conduction. Comprehensive electrochemical evaluations were conducted to assess the performance of the optimized solid electrolyte. The densified sample exhibited a high critical current density (CCD) of 6 mA cm⁻², which is three times greater than that of the pristine counterpart. This high CCD signifies the ability of the electrolyte to support high rates of sodium-ion transport without significant polarization, a crucial parameter for high-power applications.To further validate the effectiveness of our densification approach, full cells were assembled using the densified NZSP electrolyte paired with a sodium vanadium phosphate (NVP) cathode. These cells exhibited a marked increase in capacity, reflecting the improved ionic conductivity and reduced interfacial resistance achieved through densification. The results demonstrate the practical viability of the optimized electrolyte in real battery systems. Such advancements are crucial for the commercialization of high-energy-density sodium batteries, paving the way for safer and more sustainable energy storage technologies. Figure 1

The physicochemical characterization of pharmaceutical materials is essential for drug discovery, development and evaluation, and for understanding and predicting their interaction with physiological systems. Amongst many measurement techniques for spectroscopic characterization of pharmaceutical materials, Electrical Impedance Spectroscopy (EIS) is powerful as it can be used to model the electrical properties of pure substances and compounds in correlation with specific chemical composition. In particular, the accurate measurement of specific properties of drugs is important for evaluating physiological interaction. The electrochemical modelling of compounds is usually carried out using spectral impedance data over a wide frequency range, to fit a predetermined model of an equivalent electrochemical cell. This paper presents experimental results by EIS analysis of four drug formulations (trimethoprim/sulfamethoxazole C14H18N4O3-C10H11N3O3, ambroxol C13H18Br2N2O.HCl, metamizole sodium C13H16N3NaO4S, and ranitidine C13H22N4O3S.HCl). A wide frequency range from 20 Hz to 30 MHz is used to evaluate system identification techniques using EIS data and to obtain process models. The results suggest that arrays of linear R-C models derived using system identification techniques in the frequency domain can be used to identify different compounds.