A Water-Soluble NaCMC/NaPAA Binder for Exceptional Improvement of Sodium-Ion Batteries with an SnO2 -Ordered Mesoporous Carbon Anode

Breaking Barriers: Binder-Assisted NiS/NiS2 Heterostructure Anode with High Initial Coulombic Efficiency for Advanced Sodium-Ion Batteries

Developing sodium-ion batteries (SIBs) with high initial coulombic efficiency (ICE) and long-term cycling stability is crucial to meet energy storage device requirements. Designing anode materials that could exhibit high ICE is a promising strategy to realize enhanced energy density in SIBs. A trifunctional network binder substantially improves the electrochemical performance and ICE, providing excellent mechanical properties and strong adhesion strength. A rationally designed electrode material and binder can achieve high ICE, long cycling performance, and excellent specific capacity. Here, a NiS/NiS2 heterostructure as an anode material and a trifunctional network binder (SA-g-PAM) are designed for SIBs. Unprecedently, the anode comprising of an SA-g-PAM binder achieved the highest ICE of 90.7% and remarkable cycling stability for 19000 cycles at a current density of 10 A g-1 and maintained the specific capacity of 482.3 mAh g-1 even after 19000 cycles. This exciting work provides an alternate direction to the battery industry for developing high-performance electrode materials and binders with high ICE and excellent cycling stability for energy storage devices.

Cross-Linked Sodium Alginate as A Multifunctional Binder to Achieve High-Rate and Long-Cycle Stability for Sodium-Ion Batteries

Sodium-ion batteries (SIBs) hold great promise owing to the naturally abundant sodium resource and high safety. The research focus of SIBs is usually directed toward electrode materials, while the binder as an important component is rarely investigated. Herein, a cross-linked sodium alginate (SA)/graphene oxide (GO) binder is judiciously designed to serve as a robust artificial interphase on the surface of both anode and cathode of SIBs. Benefiting from the cross-linking continuous network structure as well as the highly hydrophilic nature, the SA-GO binder possesses a large tensile strength of 197.7 Mpa and a high ionic conductivity of 0.136 mS cm^-1 , superior to pure SA (93.8 Mpa, 0.025 mS cm^-1 ). Moreover, the structural design of SA-GO binder exhibits a strong binding ability to guarantee structural integrity during cycling. To demonstrate its effectiveness, polyanion-type phosphates (e.g., Na₃ (VO)₂ (PO₄ )₂ F) and chalcogenides (e.g., MoS₂ , VS₂ ) are adopted as cathode and anode materials of SIBs, respectively. As compared to traditional binders (e.g., PVDF, SA), electrodes with the SA-GO binder exhibits significantly increased rate capability and cycling stability, such as Na₃ (VO)₂ (PO₄ )₂ F (40 C fast-charge, 84% capacity retention after 1000 cycles). This work highlights the role of novel aqueous-based binders in developing next-generation sodium-storage devices.

Fundamental Understanding and Research Progress on the Interfacial Behaviors for Potassium-Ion Battery Anode

Potassium-ion batteries (PIBs) exhibit a considerable application prospect for energy storage systems due to their low cost, high operating voltage, and superior ionic conductivity. As a vital configuration in PIBs, the two-phase interface, which refers to K-ion diffusion from the electrolyte to the electrode surface (solid-liquid interface) and K-ion migration between different particles (solid-solid interface), deeply determines the diffusion/reaction kinetics and structural stability, thus significantly affecting the rate performance and cyclability. However, researches on two-phase interface are still in its infancy and need further attentions. This review first starts from the fundamental understanding of solid-liquid and solid-solid interfaces to in-depth analyzing the effect mechanism of different improvement strategies on them, such as optimization of electrolyte and binders, heterostructure design, modulation of interlayer spacing, etc. Afterward, the research progress of these improvement strategies is summarized comprehensively. Finally, the major challenges are proposed, and the corresponding solving strategies are presented. This review is expected to give an insight into the importance of two-phase interface on diffusion/reaction kinetics, and provides a guidance for developing other advanced anodes in PIBs.

Binders for sodium-ion batteries: progress, challenges and strategies

Binders as a bridge in electrodes can bring various components together thus guaranteeing the integrity of electrodes and electronic contact during battery cycling. In this review, we summarize the recent progress of traditional binders and novel binders in the different electrodes of SIBs. The challenges faced by binders in terms of bond strength, wettability, thermal stability, conductivity, cost, and environment are also discussed in details. Correspondingly, the designing principle and advanced strategies of future research on SIB binders are also provided. Moreover, a general conclusion and perspective on the development of binder design for SIBs in the future are presented.

Effect of new crystalline phase on the ionic conduction properties of sodium perchlorate salt doped carboxymethyl cellulose biopolymer electrolyte films

Dopant induced modifications in the microstructure of sodium carboxymethyl cellulose (NaCMC) were characterized by FTIR, XRD, DSC and EIS techniques. FTIR analysis exhibited a considerable microstructural modification in NaCMC upon NaClO4⋅H2O doping invoked through complex formation via Lewis acid-base interaction and hydrogen bond formation between ions and dipoles. This resulted in the modification in the orderliness/disorderliness of polymer chains as observed from XRD deconvolution. At higher salt concentrations, the complexity of the network causes the formation of new amorphous and crystalline phases as reflected in the XRD studies. DSC analysis showed an increase in Tg as the salt concentration increased, indicating a reduction in polymer chains flexibility. The contribution of free ions has masked over the enhancement in amorphous content to conductivity at a lower concentration of salt in the matrix, later on, the formation of a new crystalline phase due to transient crosslinks by Na+…ClO4−…Na+ has affected the ion transport process.

Conversion-Alloying Anode Materials for Sodium Ion Batteries

The past decade has witnessed a rapidly growing interest toward sodium ion battery (SIB) for large-scale energy storage in view of the abundance and easy accessibility of sodium resources. Key to addressing the remaining challenges and setbacks and to translate lab science into commercializable products is the development of high-performance anode materials. Anode materials featuring combined conversion and alloying mechanisms are one of the most attractive candidates, due to their high theoretical capacities and relatively low working voltages. The current understanding of sodium-storage mechanisms in conversion-alloying anode materials is presented here. The challenges faced by these materials in SIBs, and the corresponding improvement strategies, are comprehensively discussed in correlation with the resulting electrochemical behavior. Finally, with the guidance and perspectives, a roadmap toward the development of advanced conversion-alloying materials for commercializable SIBs is created.

A Sodium-Ion Battery Separator with Reversible Voltage Response Based on Water-Soluble Cellulose Derivatives

The development of efficient, safe, and environmentally friendly energy storage systems plays a pivotal role in moving toward a more sustainable society. Sodium-ion batteries (NIBs) have garnered considerable interest in grid energy storage applications because of the abundance of sodium, low cost, and suitable redox potential. However, NIB technology is still in its infancy, especially with regard to separators. Here we develop a novel separator based on renewable water-soluble cellulose derivatives. Carboxymethyl cellulose (CMC) and hydroxyethyl cellulose (HEC) are cross-linked to afford large-specific-surface-area membranes upon nonsolvent-induced phase separation (NIPS). Long-term galvanostatic cycling in a symmetric Na/Na cell configuration shows an impressive reversible voltage response with a square wave shape of the polarization even after 250 h of cycling, indicating remarkably stable Na plating and stripping with Na dendrite growth suppression. This novel membrane is evaluated as a separator in Na₃V₂(PO₄)₃/Na half-cells. After 10 cycles at C/10, the cellulosic separator delivers a capacity of 74 mA·h·g^-1 with a 100% Coulombic efficiency compared to that of 61 mA·h·g^-1 and 96% obtained for Whatman GF/D as a commercially available separator. Our work provides novel cues for the development of biomass-derived porous membranes to function as battery separators, surpassing the performance of commercially available separators based on fossil resources in terms of capacity retention, Coulombic efficiency, homogeneous plating/stripping of Na, and dendrite growth suppression. These separators, which may be extended to other battery systems, are expected to play a significant role in developing sustainable energy storage systems.

High-performance sodium-ion batteries with a hard carbon anode: transition from the half-cell to full-cell perspective

Hard carbon is an appealing anode material for sodium-ion batteries (SIBs) due to renewable resources, low cost and high specific capacity. Practical full cells based on hard carbon with high energy density and long cyclability are expected to possess application interest for grid-scale energy storage. In this review, following this archetypal use scenario of SIBs, we aim at providing a quantitative full-cell metric for evaluating newly designed anodes or cathodes. Some significant problems in conventional half-cell and full-cell tests, including unfaithful prediction of capacity loss by coulombic efficiency in the full-cell and under-estimated capacity of hard carbon in the half-cell test, are discussed to better assess the actual capacity and cyclability of the hard carbon anode in sodium-matched full cells. Finally, we review rational design of hard carbon itself and the selection of electrolytes from such a full-cell perspective.

Composition Modulation of Ionic Liquid Hybrid Electrolyte for 5 V Lithium-Ion Batteries

Electrolyte is a key component in high-voltage lithium-ion batteries (LIBs). Bis(trifluoromethanesulfonyl)imide-based ionic liquid (IL)/organic carbonate hybrid electrolytes have been a research focus owing to their excellent balance of safety and ionic conductivity. Nevertheless, corrosion of Al current collectors at high potentials usually happens for this kind of electrolyte. In this study, this long-standing problem is solved via the modulation of the IL/carbonate ratio and LiPF₆ concentration in the hybrid electrolyte. The proposed electrolyte suppresses Al dissolution and electrolyte oxidation at 5 V (vs Li⁺/Li) and thus allows for ideal lithiation/delithiation performance of a high-voltage LiNi_0.5Mn_1.5O₄ (LNMO) cathode even at 55 °C. The underlying mechanism is examined in this work. Excellent cycling stability (97% capacity retention) for an LNMO cathode after 300 cycles is achieved. This electrolyte shows good wettability toward a polyethylene separator and low flammability. In addition, satisfactory compatibility with both graphite and Si-based anodes is confirmed. The proposed electrolyte design strategies have great potential for applications in high-voltage LIBs.

Preparation of an Amorphous Cross-Linked Binder for Silicon Anodes

An amorphous cross-linked binder is prepared from abundant and low-cost sodium alginate and carboxymethyl cellulose by protonation and mixing and is used to improve the electrochemical performance of silicon anodes in lithium-ion batteries. The amorphous cross-linked structure, formed by intermolecular hydrogen bonding between the functional groups in the two polymers, effectively enhances the flexibility and strength of the binder, resulting in strong adhesion between the binder and other components in the silicon anodes. Furthermore, the binder tolerates large volume changes and reduces the pulverization of silicon during the charge-discharge process. The hydrogen bonding in the binder helps to maintain the anode integrity during the volume change, leading to an excellent cycling stability and superior rate capability with a capacity of 1863 mAh g^-1 at 500 mA g^-1 after 150 cycles.

Sodium Alginate Enabled Advanced Layered Manganese-Based Cathode for Sodium-Ion Batteries

Sodium-ion batteries (SIBs) are promising candidates applied to large-scale energy storage systems owing to abundant sodium resources and high economic efficiency. Layered manganese-based oxides as a prevailing cathode for sodium-ion batteries have been extensively studied, where doping or coating has been demonstrated to improve the electrochemical performance. However, the binder that tends to be the popular poly(vinylidene difluoride), is revealed to generate swellability upon cycling, leading to electrode material cracks and disconnection with current collectors. For the above issues, in this work, environmentally friendly sodium alginate is utilized as the aqueous binder in a conventional layered transition-metal oxide cathode P2-Na_2/3MnO₂ for SIBs. Through credible comparative experiments, sodium alginate is testified to play an essential role in suppressing cracks on the surface of materials, preventing surge in charge-transfer resistance and restraining detachment between electrode and current collector. Therefore, sodium alginate is proved to be an ideal binder to match with P2-Na_2/3MnO₂, where some issues existed before, as a promising cathode material with excellent performance and low cost. This study displays that improving battery performance by exploring suitable binder systems can equal or even exceed the performance improvement through modification of the material itself, and this perspective of enhancement should not be ignored.