Performance Of Na-ion Batteries Research Articles

Exploring Mo2B MBene as a high-capacity anode material for multi-valent metal-ion batteries: Insights from first-principles calculations

A novel class of 2-dimensional (2D) materials, known as MBenes, has recently been proposed as a promising candidate for electrode applications in metal-ion batteries due to their high conductivity and rich chemistry. In this study, we present a computational investigation into the potential of Mo2B MBene as an anode material for Na-, Mg-, and Al-ion batteries. Using density functional theory (DFT) calculations, we examine the structural, electronic, and electrochemical properties of both H- and T-type configurations of Mo2B. Our findings reveal that Mo2B exhibits metallic behavior and excellent metal adsorption characteristics, with Al exhibiting the strongest binding affinity, followed by Mg and Na. This strong binding, especially with Al, although results in higher diffusion barriers, it enhances layer adsorption leading to increased theoretical capacity. The calculated maximum capacities are significant, with Al (1323 mAh g−1) showing the highest capacity, followed by Mg (923 mAh g−1) and Na (216 mAh g−1). Additionally, the open-circuit voltage (OCV) for all metals ranges between 0.1 and 1.0 V, suggesting the suitability of Mo2B MBene as an anode material that minimizes dendrite formation risks. These results indicate the potential of Mo2B for high-performance multi-valence ion batteries, with particular promise for Al-ion batteries due to their superior capacity. Furthermore, we propose that strain engineering could optimize Mo2B for enhanced performance in Na-ion batteries. Overall, this study suggests Mo2B MBene as a highly promising anode material for next-generation metal-ion batteries, offering significant advantages in terms of capacity, voltage, and safety. Our findings provide insights that could be used for further experimental design of Mo2B-based anodes for energy storage technologies.

Mg/Ti co-substituted P2-Na0.67Ni0.23Mg0.05Ti0.05Mn0.67O2 cathode with outstanding performance for Na-ion batteries

P2-type layer oxides are one class of cathode materials for Na-ion batteries (SIBs) with the advantages of good rate and cycle performance, but suffer from poor storage stability and relative low capacity, hindering their practical applications. In this study, the Mg/Ti co-substituted P2-type layered oxide Na0.67Ni0.23Mg0.05Ti0.05Mn0.67O2 (NMgTiM) was synthesized via sol–gel method. The initial capacity of NMgTiM reached to 162.2mAh g−1, which is more than twice that of pristine oxides Na0.67Ni0.33Mn0.67O2 (NM), showing an excellent synergistic effect. Long-cycle testing showed that the NMgTiM delivered a high and stable capacity of 165 ∼ 180mAh g−1 at 0.5C before 80 cycles, and remained at 132.6mAh g−1 with a capacity retention of 81.6 % at 100th cycle. The crystal structure of pristine and Mg/Ti substitution samples was confirmed by XRD analysis.

Unleashing the impact of Nb-doped, single crystal, cobalt-free P2-type Na0.67Ni0.33Mn0.67O2 on elevating the cycle life of sodium-ion batteries

A synergistic stabilization effect in a Nb-doped P2-type single crystal cobalt-free layered oxide cathode material, offering remarkable cycling stability and high-power performance for Na-ion batteries have unveiled in this study. The introduction of Nb in the transition metal layer not only reduces the electronic band gap but also enhances electronic conductivity and mitigates ionic diffusion energy barriers. The induction of a robust Nb-O bond expedites electron and Na+ transfer, contributing to the stabilization of the host structure is further confirmed through the density functional theory calculations, including electron localization function (ELF) and crystal orbital Hamiltonian population (COHP). To the best of our knowledge, this study is the first to demonstrate a homogeneous distribution of niobium throughout the single crystal, specifically doped at the nickel site within the bulk, without inducing atomic-scale surface reorganization. The presence of single crystals improves various kinetic factors, demonstrating the profound correlation between structural defects and chemical proliferation, thereby reducing the evolution of oxygen gas. The P2-type Nb-doped single crystal cathode (Na0.67Ni0.31Mn0.67Nb0.02O2) exhibits remarkable capacity retention, >95 % after 100 cycles at 0.1 C and >90 % after an extended cycling of 2000 cycles at 1 C. Practical assessments in complete cell setups with a pre-sodiated hard carbon anode further validate the material's viability, showcasing capacity retention of over 93 % after 100 cycles in a coin cell and approximately 89 % in a pouch cell format. This comprehensive study establishes the transformative potential of Nb-doped single crystal cobalt-free P2-type layered oxide cathode materials, marking a significant advancement in sodium-ion battery technology.

Li-doped P3-type Mn-Ni-Based Cathodes with Improved Electrochemical Performance for Na-ion Batteries

Li-doped P3-type Mn-Ni-Based Cathodes with Improved Electrochemical Performance for Na-ion Batteries

A Carbonyl and Azo-Based Polymer Cathode for Low-Temperature Na-Ion Batteries.

Due to flexible structure tunability and abundant structure diversity, redox-active polymers are promising cathode materials for developing affordable and sustainable Na-ion batteries (NIBs). However, polymer cathodes still suffer from low capacity, poor cycle life, and sluggish reaction kinetics. Herein, we designed and synthesized a polymer cathode material bearing carbonyl and azo groups as well as extended conjugation structures in the repeating units. The polymer cathode exhibited exceptional electrochemical performance in NIBs in terms of high capacity, long lifetime, and fast kinetics. When coupled with a low-concentration electrolyte, it shows superior performance at low temperatures down to -50 °C, demonstrating great promise for low-temperature battery applications. Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) were employed to study the reaction mechanism, interphase structure, and morphological evolution, confirming reversible redox reactions between azo/carbonyl groups in the polymer and Na+/electrons, a NaF-rich interphase, and high structure stability upon cycling. This work provides an effective approach to developing high-performance polymer cathodes for affordable, sustainable, and low-temperature NIBs.

Improving the Electronic Conductivity of Alluaudite Na2.5Fe1.75(SO4)3 Cathodes for Na-Ion Batteries

The increasing dependency on batteries in modern technology has led to an ever-increasing demand that cannot be met by Li-ion batteries (LIBs) alone. The push towards using renewable energy and electric vehicles, coupled with the limited reserves of lithium resources is encouraging research into alternative options for electrochemical storage devices. Na-ion batteries (SIBs) are a promising alternatives due to the similarity of their chemistry to LIBs. This allows for utilisation of analogous materials and methods already in place for LIBs. Furthermore, SIBs are more economically viable and environmentally sustainable due to the abundance of the elements that can be utilised as electrode active materials. For example, SIB cathodes, such as Na2.5Fe1.75(SO4)3, can be synthesised from precursor materials that are widely available by-products of industry. The polyanionic framework of Na2.5Fe1.75(SO4)3 has three 3-dimensional vacancies within it, in which Na-ions de/intercalate.[1] However, the performance of Na-ion batteries is hindered by the low electronic conductivity of these polyanionic compounds, affecting the flow of electrons through the material and the reversible movements of the Na ions.[2] To address this issue, previous reports have shown that using a conductive additive such as carbon black and graphene oxides can increase the electronic conductivity of Na ion cathode materials and improving battery performance.[3]In this work, we investigate a non-stoichiometric alluaudite phase Na2.5Fe1.75(SO4)3 material (NFS), produced by a ball-milling-assisted solid-state synthesis. A study of the effects of variables on the ball milling process using the was carried out. A multi-step process involving a repetition of the ball milling and annealing was used to decrease particle size and eliminate impurities. The results were compared regarding particle size, impurities present, conductivity and battery performance. The obtained materials were characterised using X-ray diffraction, scanning electron microscopy and electrochemical impedance spectroscopy. The materials were tested as cathodes in sodium half-cells with 1 mol/L NaClO4 in ethylene carbonate (EC)/ propylene carbonate (PC) electrolyte. The additional ball milling and annealing steps saw a significant decrease in impurities present across all variations in methodology. All batteries show three redox peaks in their differential capacity plots, demonstrating that all three vacancies within the polyanionic framework of Na2.5Fe1.75(SO4)3 are active during charge and discharge. The best performing electrode achieved a capacity of 80 mAh/g using only C45 as a conductive additive. These are promising results that are expected to improve with further studies researching the addition of RGOs and MXenes into the ball milling process. These composite electrodes will be prepared by combining rGOs/MXenes with the NFS precursors during the synthesis process of Na2.5Fe1.75(SO4)3 to enhance battery performance further.

High-Rate Performance of Antimony Chalcogenides (Sb2X3) Studied By Operando X-Ray Diffraction (XRD)

Na-ion batteries (NIBs) represent an environmentally-friendly and sustainable alternative to Li-ion batteries (LIBs), owing to the higher abundance of Na compared to Li. [1] However, many challenges associated with the successful implementation of NIBs are yet to be addressed, which includes the optimization of the present set of materials. Among others, the development of high-performing anode materials as a replacement for conventionally used hard carbon is essential to deliver NIBs with high energy density. A class of materials promising for implementation in NIBs is based on the combined conversion/alloying reaction pathway as a main motive of their operating mechanism. [2] However, such conversion/alloying materials (CAMs) typically undergo a set of complex structural and chemical transformations during electrochemical cycling (formation of new phases, amorphization, etc). [3] Investigation of the (de)sodiation mechanism using advanced characterization techniques, such as operando X-ray diffraction (XRD), is therefore the key to revealing the true potential of these battery mechanisms.Among many CAMs, Sb-based chalcogenides (Sb2X3, where X = O, S, Se, Te) have demonstrated superior electrochemical performance in NIBs. In the present work, the research efforts have been focused on elucidating the (de)sodiation mechanism of Sb2Se3/Sb (Sb-rich Sb2Se3) materials using operando XRD. The study reveals the true complexity of the (de)sodiation mechanism for Sb2Se3/Sb (Figure 1), where the active material passes through a combination of multiple phases (Na2Se, Na2Se4, Sb, NaSb, hexagonal Na3Sb, cubic Na3Sb) during sodiation, where some of these phases are amorphous.One of the discovered benefits of such chalcogenide materials is the ability to operate at high cycling rates. Therefore, another objective of this study is to understand if and how the (de)sodiation mechanism change as a function of the C-rate. The preliminary operando XRD analysis suggests that kinetics plays a crucial role in the formation of certain phases during cycling leading to a rate-dependent cycling mechanism. Thus, a systematic study utilizing specific currents of 100 mA g-1, 1000 mA g-1, and 5000 mA g-1 have been applied to the Sb2Se3/Sb system to deepen the understanding of the (de)sodiation mechanism.This presentation will underpin the fundamentals of the cycling mechanism of Sb2Se3/Sb using operando XRD as a function of cycling rates. A better knowledge of the various mechanisms by which sodium can move in and out of this material is crucial for our understanding and potentially mitigate the limited cycling stability that limits their practical usefulness.References. Hasa, I., et al., Challenges of today for Na-based batteries of the future: From materials to cell metrics. Journal of Power Sources, 2021. 482: p. 228872. Skurtveit, A., et al., Benefits and Development Challenges for Conversion-Alloying Anode Materials in Na-Ion Batteries. Frontiers in Energy Research, 2022. 10. Brennhagen, A., et al., Understanding the (De)Sodiation Mechanisms in Na‐Based Batteries through Operando X‐Ray Methods. Batteries & Supercaps, 2021. 4(7): p. 1039-1063. Figure 1

Revealing the Cycling and Degradation Mechanism of Bi-Metallates As Anode Materials for Na-Ion Batteries

Na-ion batteries (NIBs) represent an emerging alternative to modern Li-ion batteries. To improve the overall performance of NIBs it is crucial to develop new types of anode materials with high capacity and long cycle life. Among the anode candidates, materials operating under combined conversion and alloying mechanisms (CAMs) are considered as promising. They are capable of delivering high capacity, however, despite theoretical predictions the cycling stability is still below expectations. Therefore, a comprehensive understanding of the cycling and degradation mechanisms of CAMs is crucial to improve their performance. However, these materials undergo multiple chemical transformations, which often involves formation of amorphous and nanocrystalline phases during cycling. Such chemical complexity substantially impedes their full characterization and understanding.Bismuth metallates, with a general formula of Bi-TM-O (TM = transition metal), is a group of ternary CAMs. Their general cycling mechanism consists of an irreversible conversion reaction, which leads to formation of Bi nanoparticles embedded in a Na-TM-O matrix during the first sodiation. This is followed by a reversible two-step alloying reaction leading to formation of Na3Bi with NaBi as an intermediate phase. In this work, we have used operando X-ray diffraction over the course of ∼30 cycles to study the cycling and degradation mechanisms of two CAMs - Bi2MoO6 and BiFeO3. With the help of ex situ X-ray absorption spectroscopy and pair distribution function (PDF) analysis, we have revealed new insights into these materials in addition to confirming the general cycling mechanism.Both materials form the cubic phase of Na3Bi (c-Na3Bi) in the sodiated state with some noticeable differences. While, the hexagonal Na3Bi (h-Na3Bi) phase starts to form after 10 cycles in Bi2MoO6, a combination of c-Na3Bi and h-Na3Bi can be observed after the first cycle in BiFeO3. The formation of c-Na3Bi is kinetically favorable in these systems, while h-Na3Bi is the more thermodynamically stable and, therefore, forms later in the cycling process. Both materials shows three distinct regions of capacity degradation, where the first is initiated by a growth in the crystallite sizes of Bi-particles. This is followed by a disappearance of the Bi-phase as the second step. The last degradation phase is related to the disappearance of the NaBi-phase and locking the system in the sodiated state. The present talk will discuss the mechanisms of these degradation steps in view of the future development of CAMs in greater details. Figure 1

(Invited) Advanced Organic Electrode Materials for High-Performance and Sustainable Na-Ion Batteries

Na-ion batteries (NIBs) are promising alternatives to Li-ion batteries (LIBs) due to the low cost, abundance, and high sustainability of sodium resources. However, the high performance of inorganic electrode materials in LIBs does not extend to NIBs because of larger ion size of Na+ than Li+ and more complicated electrochemistry. Therefore, it is vital to search for high-performance electrode materials for NIBs. To this end, organic electrode materials (OEMs) with the advantages of high structural tunability and abundant structural diversity show great promise in developing high-performance NIBs. To achieve advanced OEMs for NIBs, a fundamental understanding of the structure–performance correlation is desired for rational structure design and performance optimization. Tailoring molecular structures of OEMs can enhance their performance in Na-ion batteries, however, the substitution rules and the consequent effect on the specific capacity and working potential remain elusive. Herein, we explored the electrochemical performances and reaction mechanisms of various carboxylate-based anode materials, including halogenated sodium carboxylates, N-doped sodium carboxylates, etc. By examining sodium carboxylates with different functional groups, selective N substitution, and extended conjugation structure, we exploited the correlation between structure and performance to establish substitution rules for high-capacity OEMs. Our results show that substitution position and types of functional groups are essential to create active centers for uptake/removal of Na+ and thermodynamically stabilize organic structures. Furthermore, rational host design and electrolytes modulation were performed to extend the cycle life. In addition to sodium carboxylate-based anode materials, we also designed and synthesized novel organic cathode materials based on azo and carbonyl groups for NIBs. The electrochemical performance of the organic cathode materials with an extended conjugated structure such as a naphthalene backbone structure is better than that with benzene and biphenyl structures due to faster kinetics and lower solubility in the electrolyte. It unravels the rational design principle of extending π-conjugation aromatic structures in redox-active polymers to enhance the electrochemical performance. To further optimize the organic cathodes, nitrogen-doped or single layer graphene is employed to increase the conductivity and mitigate the dissolution of organic materials in the electrolytes. The resulting organic cathodes deliver high specific capacity, long cycle life, and fast-charging capability. Post-cycling characterizations were employed to study the chemical structure and morphology evolution upon cycling, demonstrating that the active centers (azo and carbonyl groups) in the organic cathode materials can undergo reversible redox reactions with Na+ for sustainable NIBs. Our work provides a valuable guideline for the design principle of high-capacity and stable OEMs for sustainable energy storage.

Assessment of Na-Ion Battery Performance Using Machine Learning

In the last couple of decades, the smart design of battery electroactive materials and cells to satisfy the demand for efficient energy storage has attracted significant research interest. Li-ion batteries have been widely employed in hybrid cars, power plants, and electronic devices. However, sodium-ion batteries are getting increasing attention as sodium is much more earth-abundant and inexpensive than lithium. In this work, we studied the impact of critical materials and cell design factors, electrode preparation methods, and operational descriptors on the discharge capacity and the cycle life of the Na-ion batteries using machine learning. The dataset was created from 355 experimental papers published in 2015-2020 and contained 1227 different experiments: 747 and 380 cases had only the anode and the cathode studies, respectively, whereas 100 cases were for the full cells. In the analysis, 38 descriptors were used on the electrode materials, electrolyte, and electrode structure, in addition to material synthesis and electrode preparation methods. On the other hand, peak discharge capacity and cycle life (the highest cycle number at which 80% of the peak capacity is retained) were selected as the target (output) variables. Random forest, gradient boosting, support vector machines (for regression), and decision tree (for classification) methods were used for the analysis. In the analyses, the dataset was randomly divided into two subsets: 75% to build the models (training and validation) and 25% to test the performance of the models in predicting the unseen data. Five-fold cross-validation was applied for hyperparameter optimization. Root mean square error (RMSE) was calculated as the performance indicator.The pre-analysis of the dataset presented that the highest average discharge capacity is obtained with the alloy-based anodes, followed by metal sulfides. However, their average cycle life is relatively low. In contrast, carbon-based anodes present prolonged cycle life even though they have low discharge capacities. Moreover, full-cell applications that couple the alloy-based anodes with the metal oxide cathodes show the highest average discharge capacity. Lastly, for anode or cathode half-cell studies, using a single solvent leads to higher discharge capacities and cycle life. In contrast, mixed solvents perform better in full cells.Random forest models successfully predicted the discharge capacity and demonstrated the relative significance of descriptors (Figure 1). Boruta analysis, performed for feature importance, showed that the anode and cathode types are highly effective. At the same time, the synthesis method and crystal structure were also found to be influential. On the other hand, we used classification models, which can be considered as range prediction instead of point prediction, instead of regression models to analyze the cycle life data. Decision tree classification of cycle life was quite effective, leading to heuristic rules for selecting the anode and cathode materials or methods for synthesis and electrode preparation. Material synthesis conditions are essential for high cycle life for the anode, while solvent selection is also critical for the cathode studies. Figure 1. Random Forest Regression model for the prediction of the peak discharge capacity for a) anode training, b) anode testing, c) cathode training, and d) cathode testing sets

Investigation of electrochemical performance of Na-ion batteries by hard carbon anodes produced by biomass of Prunus armeniaca seeds

Investigation of electrochemical performance of Na-ion batteries by hard carbon anodes produced by biomass of Prunus armeniaca seeds

Structural Control of Electrodeposited Sb Anodes through Solution Additives and Their Influence on Electrochemical Performance in Na-Ion Batteries

Structural Control of Electrodeposited Sb Anodes through Solution Additives and Their Influence on Electrochemical Performance in Na-Ion Batteries

Dielectric polarization in MgFe2O4 coating and bulk doping to enhance high-voltage cycling stability of Na2/3Ni1/3Mn2/3O2 cathode material

Charging P2-Na2/3Ni1/3Mn2/3O2 to 4.5 V for higher capacity is enticing. However, it leads to severe capacity fading, ascribing to the lattice oxygen evolution and the P2-O2 phase transformation. Here, the MgFe2O4 coating and Mg, Fe co-doping were constructed simultaneously by Mg, Fe surface treatment to suppress lattice oxygen evolution and P2-O2 phase transformation of P2-Na2/3Ni1/3Mn2/3O2 at deep charging. Through ex-situ X-ray diffraction (XRD) tests, we found that the Mg, Fe bulk co-doping could reduce the repulsion between transition metals and Na+/vacancies ordering, thus inhibiting the P2-O2 phase transition and significantly reducing the irreversible volume change of the material. Meanwhile, the internal electric field formed by the dielectric polarization of MgFe2O4 effectively inhibits the outward migration of oxidized Oα− (α < 2), thereby suppressing the lattice oxygen evolution at deep charging, confirmed by in situ Raman and ex situ XPS techniques. P2-NaNM@MF-3 shows enhanced high-voltage cycling performance with capacity retentions of 84.8% and 81.3% at 0.1 and 1 C after cycles. This work sheds light on regulating the surface chemistry for Na-layered oxide materials to enhance the high-voltage performance of Na-ion batteries.

The synergistic effect of Ti and Nb in TiNbC leads to enhanced anode performance for Na-ion batteries - first-principles calculations

Currently, MXenes have been identified as promising candidate electrode materials for Na-ion batteries because of their excellent energy storage and electrical conductivity. Among them, dual transition metal MXenes have attracted attention due to their excellent properties as anode materials for Na-ion batteries. In order to explore the reason why dual transition metal MXenes outperform single transition metal MXenes, we systemically investigated and compared the performance of TiNbC-based dual transition metal MXenes (TiNbC, TiNbCF2, and TiNbCO2) with that of Nb2C-based single transition metal MXenes (Nb2C, Nb2CF2, and Nb2CO2) as anode materials for Na-ion batteries based density functional theory calculations. The results showed that TiNbC, TiNbCO2, Nb2C, and Nb2CO2 are promising anode materials for Na-ion batteries due to the low diffusion barrier and high capacity of Na on their surfaces. Compared with the Nb2C-based single transition metal MXenes, the TiNbC-based dual transition metal MXenes have better adsorption performance, diffusion rate, and theoretical storage of Na atoms. The higher adsorption ability of TiNbC and TiNbCO2 to Na atoms was attributed to the synergistic effect of Ti and Nb which increases the interaction between the substrate and Na. This conclusion provides a new insight for the development of other high-performance MXenes-based anode materials for Na-ion batteries.

Three-dimensional heterogeneity in liquid electrolyte structures promotes Na ion transport and storage performance in Na-ion batteries.

Unlike solid materials, the molecular structure and chemical distribution in electrolyte solutions have been considered in isotropic states. Herein, we reveal controllable regulation of solution structures in electrolytes by manipulating solvent interactions for Na-ion batteries. Low-solvation fluorocarbons as diluents in concentrated phosphate electrolytes induce adjustable heterogeneity in electrolyte structures through variable intermolecular forces between high-solvation phosphate and diluents. An optimal trifluorotoluene (PhCF3) diluent weakens the solvation strength around Na+ and spontaneously leads to a locally enlarged Na+ concentration and global 3D continuous Na+ transport path thanks to the appropriate electrolyte heterogeneity. Besides, strong correlations between the solvation structure and the Na+ storage performance and interphases are demonstrated. PhCF3 diluted concentrated electrolyte enables superior operations of Na-ion batteries at both room temperature and a high temperature of 60 °C. A hard carbon anode exhibits a reversible capacity of 300 mA h g-1 at 0.2C and excellent life over 1200 cycles without decay.

N-doped carbon coated V2O3 nanospheres with V-C bond for superior sodium storage

• Close contact and strong interaction between V 2 O 3 and NC existed in V 2 O 3 @NC. • Shortened ion diffusion pathways favored the electrochemical kinetics. • The surface coated NC introduced strong pseudo-capacitive behaviors. • V-C bond provided additional pathways and created more active sites for ion storage. • V 2 O 3 @NC delivered a high rate performance and a stable electrochemical stability. Uniform V 2 O 3 @NC (N-doped C) nanospheres with close contact and strong interaction between V 2 O 3 and NC was fabricated through a solvothermal and carbonization strategy. The fabricated V 2 O 3 @NC electrode exhibited shortened ion diffusion pathways and improved electronic conductivity, which favored the electrochemical kinetics. In addition, the strong interaction between V 2 O 3 and NC through V-C bond provided additional electron diffusion pathways, and the surface coated NC introduced a strong pseudo-capacitive behavior. As a consequence, the V 2 O 3 @NC electrode delivered excellent electrochemical performance in Na-ion batteries.

One-Pot Spray Engineering to Design Na0.44MnO2 Cathode Electrodes for High-Rate and Cycle-Stable Na-Ion Batteries

To improve the practical performance of Na-ion batteries, electrode structure engineering provides a new route to improve the electrochemical efficiency of the cathode active material. In this study, we suggest a new route of one-pot spray engineering to design Na0.44MnO2 cathodes to realize high-rate and cycle-stable Na-ion battery performance. This technique adjusts the electrode structure from a dense to an open sponge-like morphology during layer-by-layer deposition of the materials. The sponge-like cathode results in improved ion insertion and transport kinetics, thus accelerating the rate capability with increased capacity and high-rate cycling capability (100.1 mAh/g and 90.2% cycling retention after 100 cycles at 5 C). These results highlight the potential for design engineering of cathode structures to achieve high-rate and cycle-stable performance for Na-ion batteries.

Is There a Ready Recipe for Hard Carbon Electrode Engineering to Enhance Na-Ion Battery Performance?

Hard carbon (HC) materials are commonly used as anode materials in Na-ion batteries. In most of the cases, their electrochemical performance is correlated only to their physicochemical properties, and the impact of the electrode additives (binders–conductive agent) and electrolyte is often neglected. In this work, a systematic study is performed to understand the role of electrode/electrolyte engineering on HC initial Coulombic efficiency (iCE), specific capacity, and cycle stability. Four HCs obtained by pyrolysis of several biopolymers, i.e., cellulose (HC-Cell), chitosan (HC-Chs), chitin (HC-Cht), and lignin (HC-Lig), are used. The binder was found to have an important impact on the electrochemical performance, with PVDF resulting in better performance than CMC. The carbon black additive had no significant impact on CMC-based electrochemical performance while it boosted the electrochemical performance of PVDF-based electrodes. For an optimized formulation (PVDF/carbon black), the best HC performance in NaPF6 in 1 EC:DEC was delivered by HC-Cell (83% iCE, 332 mAh g–1 at C/10, and 97% retention). This was attributed to its large graphene interlayer space, high purity, and low surface area. HC-Cht and HC-Chs exhibited similar good electrochemical performance (∼280 mAh g–1) whereas the use of HC-Lig resulted in low iCE and capacity fading overcycling due to the high level of impurities in its structure. This could be overcome by changing the electrolyte salt, by using NaClO4 (76% retention) instead of NaPF6 (52% retention). Based on the obtained results, the electrochemical performance could be correlated with the HC physicochemical properties and binder/conductive additive. It could be demonstrated that careful electrode engineering combined with proper electrolyte selection and tuned HC properties allowed all investigated materials achieving reasonable iCE (up to 83%), high specific capacity (∼280 to 332 mAh g–1), and high-capacity retention (72–97% after 50 cycles).

Morphological & Structural Control of Electrodeposited Sb Anodes through Solution Additives and Their Influence on Electrochemical Performance in Na-Ion Batteries

Alloy-based materials such as antimony (Sb) are of interest for both Li/Na-ion batteries due to their theoretical capacity and electronic conductivity. Of the various ways to fabricate Sb films (slurry casting, sputtering, etc.) one promising route is through the use of electrodeposition. Electrodeposition is an industrially relevant synthetic technique that allows for the use of solution additives to control different characteristics such as film uniformity, morphology, and electrical conductivity. Solution additives such as cetyltrimethylammonium bromide (CTAB) and bis-(3-sulfopropyl) disulfide (SPS) have been used to control characteristics such as particle morphology, and electrical conductivity in various applications but have not been applied to the electrodeposition of Sb for battery applications. In this study, Sb films were electrodeposited with various concentrations of CTAB and SPS and the structure, morphology, composition, and electrochemical performance in Na-ion batteries were compared. We report that CTAB and SPS additives can significantly influence electrodeposited Sb films by altering the morphology and reducing the crystallinity of the Sb films, affecting the electrochemical performance. These studies provide valuable insight into the tunability of alloy-based films through electrodeposition and solution additives.

Constructing porous lignin-based carbon nanofiber anodes with flexibility for high-performance lithium/sodium-ion batteries

Lithium (Li)/sodium (Na)-ion batteries have been widely studied as energy storage power sources because of their long cycle life and high energy density. Lignin, which is environmentally friendly, inexpensive, and has a high carbon content, is considered one of the most promising raw materials for anodes. Hence, in this study, a porous lignin-based carbon nanofiber anode was obtained using gas–electric blending. The prepared anode is flexible, self-supporting, and can be directly used without any binders in Li/Na-ion batteries. It showed an excellent first reversible specific capacity of 1783.8 mAh/g at 0.2 C current density and maintained a specific capacity of 1429.7 mAh/g after 50 cycles in the Li-ion battery. Even at a high current density of 2 C, it exhibited a high reversible specific capacity of 1135.4 mA/h/g in the first cycle and retained 1064.7 mAh/g after 100 cycles. Furthermore, it also exhibited an excellent specific discharge capacity, stable cycle performance, and high rate performance in Na-ion batteries. This study demonstrates that lignin has broad application prospects as a high-performance energy storage material.