High-capacity Anode For Sodium Ion Batteries Research Articles

SnSe Nanosheet Array on Carbon Cloth as a High-Capacity Anode for Sodium-Ion Batteries.

Binder-free electrodes offer a great opportunity for developing high-performance sodium-ion batteries (SIBs) aiming at the application in energy storage devices. Tin selenide (SnSe) is considered to be a promising anode material for SIBs owing to its high theoretical capacity (780 mA h g-1). In this work, a SnSe nanosheet array (SnSe NS) on a carbon cloth is prepared using a vacuum thermal evaporation method. The as-prepared SnSe NS electrode does not have metal current collectors, binders, or any conductive additives. In comparison with the electrode of SnSe blocky particles (SnSe BP), the SnSe NS electrode delivers a higher initial charge capacity of 713 mA h g-1 at a current density of 0.1C and maintains a higher charge capacity of 410 mA h g-1 after 50 cycles. Furthermore, the electrochemical behaviors of the SnSe NS electrode are determined via pseudocapacitance and electrochemical impedance spectroscopy measurements, indicating a faster kinetic process of the SnSe NS electrode compared to that of the SnSe BP. Operando X-ray diffraction measurements prove that the SnSe NS exhibits better phase reversibility than the SnSe BP. After the cycles, the SnSe NS electrode still maintains its particular structure. This work provides a feasible method to prepare SnSe nanostructures with high capacity and improved sodium ion diffusion ability.

Design of antimony nanocomposite for high areal capacity sodium battery anodes

Antimony (Sb) is attractive as a high-capacity anode for sodium-ion batteries, but undergoes structural degradation and instability of the solid-electrolyte interphase caused by the large volume change during cycling. Here, we demonstrate a unique Sb-based composite anode by embedding the Sb nanoparticles into the conductive hierarchical porous graphitic carbon (HPGC) that leaves enough room for volume change and is further encapsulated by a uniform conductive nitrogen-doped carbon (NC) layer to act as an electrolyte barrier. Such a design enables the [email protected]/NC composite to exhibit a high capacity of 639 mAh g−1, stable cycling stability, and a commercial-level areal capacity of 3.11 mAh cm−2. In addition, full cells by coupling with sodium vanadium phosphate cathode deliver a high energy density of 223.4 Wh kg−1 with superior rate performance. This work provides a bright way for the rational design and construction of Sb-based anode materials for advanced SIBs.

CuFeS2 Nanosheets Assembled into Honeycomb-like Microspheres as Stable High-Capacity Anodes for Sodium-Ion Batteries

As an anode in sodium-ion batteries (SIBs), chalcopyrite (CuFeS2) has aroused tremendous interest owing to its earth-abundant elements and high theoretical specific capacities. Because ingenious nanostructures of electrode materials can significantly improve their energy storage properties, in this paper, CuFeS2 nanosheets have been assembled into honeycomb-like microspheres by a facile solvothermal method. The performance of the CuFeS2 product with the honeycomb-like microsphere structure is analyzed by several physicochemical characterizations. The results indicate that the microsphere structure of CuFeS2 can improve the energy storage properties of the anode material when it is used in SIBs. Specially, the reversible capacity is up to 528 mA h g–1 after 100 cycles, over 86.4% of initial capacity retentions, and an excellent cycling stability is achieved. Moreover, the CuFeS2 microsphere can buffer the volume expansion due to the unique layer structure. Therefore, CuFeS2 nanosheet-assembled honeycomb-like microspheres can significantly improve the energy storage properties of electrode materials during the discharging and charging processes, and it shows great promise to become the next-generation electrode material for large-scale energy storage.

Diaper-derived selenium–carbon composites as high-capacity anodes for sodium-ion batteries

Exploring ideal electrode materials and overcoming key issues such as large changes in electrode volume resulting from the big radius of Na ions and slow redox kinetics are urgent issues in the large-scale applications of sodium-ion batteries. Here, through freeze-drying and annealing strategies, a molecular complex of Se encapsulated in superabsorbent polymers carbon (Se@SAPC) has been constructed. The superabsorbent polymers carbon base serves as a storage space for the reaction of Se and Na+ and shows good physical constraints and can ensure the overall structural stability of a Se@SAPC composite anode. In addition, the hierarchical pore structure effectively can adjust the volume effect of Se, so that electrons and ions are transferred smoothly in the circulation. Electrochemical measurements showed that the Se@SAPC electrode show excellent performance, including a long cycle life (198 mA h g−1 after 1000 cycles at 2 A g−1), and high-rate performance (200 mAh g−1 at 5 A g−1). At the same time, in-situ Raman, ex-situ transmission electron microscopy and electrochemical analysis reveals the working principle of intercalation/deintercalation of Na ions in Se@SAPC composites. In addition, the full Se@SAPC // Na3V2(PO4)3/C battery shows a large reversible capacity of 198.4 mAh g−1 even after 200 cycles at 0.2 A g−1 current density. This work provides guidance for the further development and utilisation of Se anodes.

Carbon-Reinforced Nb2CTx MXene/MoS2 Nanosheets as a Superior Rate and High-Capacity Anode for Sodium-Ion Batteries.

Sodium-ion batteries operating at room temperature have emerged as a generation of energy storage devices to replace lithium-ion batteries; however, they are limited by a lack of anode materials with both an adequate lifespan and excellent rate capability. To address this issue, we developed Nb2CTx MXene-framework MoS2 nanosheets coated with carbon (Nb2CTx@MoS2@C) and constructed a robust three-dimensional cross-linked structure. In such a design, highly conductive Nb2CTx MXene nanosheets prevent the restacking of MoS2 sheets and provide efficient channels for charge transfer and diffusion. Additionally, the hierarchical carbon coating has a certain level of volume elasticity and excellent electrical conductivity to guarantee the intercalation of sodium ions, facilitating both fast kinetics and long-term stability. As a result, the Nb2CTx@MoS2@C anode delivers an ultrahigh reversible capacity of 530 mA h g-1 at 0.1 A g-1 after 200 cycles and very long cycling stability with a capacity of 403 mA h g-1 and only 0.01% degradation per cycle for 2000 cycles at 1.0 A g-1. Moreover, this anode has an outstanding capacity retention rate of approximately 88.4% from 0.1 to 1 A g-1 in regard to rate performance. Most importantly, the Nb2CTx@MoS2@C anode can realize a quick charge and discharge at current densities of 20 or even 40 A g-1 with capacities of 340 and 260 mAh g-1, respectively, which will increase the number of practical applications for sodium-ion batteries.

Three-Dimensional Self-assembled Hairball-Like VS4 as High-Capacity Anodes for Sodium-Ion Batteries

HighlightsThe unique hairball-like VS4 composed of spiral nanowires was successively constructed through a one-step hydrothermal method.The prepared hairball-like VS4 exhibits high capacity and long cycle stability for Na+ storage at room temperature, and it can tolerate drastic temperature changes.The ex situ characterization and electrochemical kinetic analysis reveal that the storage mechanisms of VS4 changed with the increase in the number of cycles.

Effect of the Particle-Size Distribution on the Electrochemical Performance of a Red Phosphorus-Carbon Composite Anode for Sodium-Ion Batteries

Sodium-ion batteries will have an important role as a complement to lithium-ion in a future where lithium or cobalt, two critical elements for lithium-ion batteries, become scarce or prohibitively expensive. Red phosphorus (RP) is a promising candidate as an anode for sodium-ion batteries because of its low potential and high specific capacity. Its main disadvantage is its 490% volumetric expansion during sodiation. This leads to particle pulverization and substantial reduction of the cycle life. Furthermore, RP has an extremely low electronic conductivity of 10-14 S cm-1. Both issues have been previously addressed by ball milling RP with a carbon matrix. This decreases the RP particle size and also forms a more electronically conductive composite. However, it is challenging to determine the RP particle size independent of the size of the composite particles. Consequently, little is known about how much the RP particle size must be reduced to improve anode performance. We quantified the relationship between the RP particle-size distribution and its cycle life for the first time by separating the ball milling process into two steps. An initial wet ball milling is used to control the RP particle-size distribution, which is measured via dynamic light scattering. This is followed by a dry milling step to produce RP-graphite composites. We found that wet milling breaks apart the largest RP particles in the range of 2 to 10 µm decreases the Dv90 from 1.85 to 1.26 µm and significantly increases the cycle life of the RP. The RP with a Dv90 of 0.79 µm mixed with graphite for 48h delivered 1,354 mA h g-1 with high coulombic efficiency (>99%) and cyclability (88% capacity retention after 100 cycles). Furthermore, we determined that the length of time of the second milling step affects the uniformity of the carbon distribution in the composite. Photoelectron spectroscopy and transmission electron microscopy confirms the successful formation of a carbon coating, thus improving the performance of the resulting material. These results are an important step in the development of cyclable, high-capacity anodes for sodium-ion batteries. Figure 1

Effect of the Particle-Size Distribution on the Electrochemical Performance of a Red Phosphorus-Carbon Composite Anode for Sodium-Ion Batteries.

Red phosphorus (RP) is a promising candidate as an anode for sodium-ion batteries because of its low potential and high specific capacity. It has two main disadvantages. First, it experiences 490% volumetric expansion during sodiation, which leads to particle pulverization and substantial reduction of the cycle life. Second, it has an extremely low electronic conductivity of 10–14 S cm–1. Both issues can be addressed by ball milling RP with a carbon matrix to form a composite of electronically conductive carbon and small RP particles, less susceptible to pulverization. Through this procedure, however, the resulting particle-size distribution of the RP particles is difficult to determine because of the presence of the carbon particles. Here, we quantify the relationship between the RP particle-size distribution and its cycle life for the first time by separating the ball-milling process into two steps. The RP is first wet-milled to reduce the particle size, and then the particle-size distribution is measured via dynamic light scattering. This is followed by a dry-milling step to produce RP–graphite composites. We found that wet milling breaks apart the largest RP particles in the range of 2–10 μm, decreases the Dv90 from 1.85 to 1.26 μm, and significantly increases the cycle life of the RP. Photoelectron spectroscopy and transmission electron microscopy confirm the successful formation of a carbon coating, with longer milling times leading to more uniform carbon coatings. The RP with a Dv90 of 0.79 μm mixed with graphite for 48 h delivered 1354 mA h g–1 with high coulombic efficiency (>99%) and cyclability (88% capacity retention after 100 cycles). These results are an important step in the development of cyclable, high-capacity anodes for sodium-ion batteries.

High-Capacity Hard Carbon Pyrolyzed from Subbituminous Coal as Anode for Sodium-Ion Batteries

A pyrolyzed subbituminous carbon is synthesized through a simple one-step carbonization process as low-cost and high-capacity anode for sodium-ion batteries (SIB). The pyrolyzed subbituminous carbon, SHC-1300 anode shows high Na storage capacity of 291 mA h g–1 at 20 mA g–1 and high initial Coulombic efficiency of 79.5%, as well as stable cycling performance, exhibiting a promising alternative anode for affordable and high-performance SIB. Furthermore, according to the investigation of the electrochemical performance and structural characterizations, the SHC-1300 pyrolyzed from subbituminous coal with flexible structure demonstrates a better electrochemical performance compared with the BHC-1300 pyrolyzed from bituminous coal with rigid structure. The sodium storage mechanism and structural evolution reported in this work may give a new prospect for the selection of pyrolyzed carbon materials for high-performance sodium-ion batteries.

In situ N-doped carbon modified (Co0.5Ni0.5)9S8 solid-solution hollow spheres as high-capacity anodes for sodium-ion batteries

The in situ N-doped carbon modified (Co0.5Ni0.5)9S8 solid-solution hollow spheres can be explored as high-capacity anodes for sodium-ion batteries.

Sodiation and Desodiation via Helical Phosphorus Intermediates in High-Capacity Anodes for Sodium-Ion Batteries

Na-ion batteries are promising alternatives to Li-ion systems for electrochemical energy storage because of the higher natural abundance and widespread distribution of Na compared to Li. High capacity anode materials, such as phosphorus, have been explored to realize Na-ion battery technologies that offer comparable performances to their Li-ion counterparts. While P anodes provide unparalleled capacities, the mechanism of sodiation and desodiation is not well-understood, limiting further optimization. Here, we use a combined experimental and theoretical approach to provide molecular-level insight into the (de)sodiation pathways in black P anodes for sodium-ion batteries. A determination of the P binding in these materials was achieved by comparing to structure models created via species swapping, ab initio random structure searching, and a genetic algorithm. During sodiation, analysis of 31P chemical shift anisotropies in NMR data reveals P helices and P at the end of chains as the primary structural components in amorphous Na xP phases. X-ray diffraction data in conjunction with variable field 23Na magic-angle spinning NMR support the formation of a new Na3P crystal structure (predicted using density-functional theory) on sodiation. During desodiation, P helices are re-formed in the amorphous intermediates, albeit with increased disorder, yet emphasizing the pervasive nature of this motif. The pristine material is not re-formed at the end of desodiation and may be linked to the irreversibility observed in the Na-P system.

Investigating the Reaction Mechanism of Sodium Insertion/Extraction in SnF2 Anode Material

Sodium-ion batteries (SIBs) are considered as a potential candidate for electrical energy storage system (ESS) because of their advantages such as low-cost system and evenly distributed sodium resources worldwide. However, there is need to explore new electrode materials for the realization of SIBs. Particularly, the anode side of SIBs needs more improvements as commonly investigated anodes in lithium-ion batteries (LIBs) such as graphite and silicon do not intercalate sodium ions. In the search for high capacity anodes for SIBs, we have investigated electrochemical properties of a nanocomposite based on SnF2 and acetylene black. The nanocomposite electrode delivers a reversible capacity of 563 mAh g-1 which is higher than the specific capacity of 323 mAh g-1 of the micron-sized bare SnF2 electrode. The sodium insertion/extraction process of the high-performing nanocomposite is revealed by in-situ XRD, ex-situ XAS and TEM techniques. The reaction mechanism revealed using in-situ XRD show the existence of a solid solution of two or more compositions during cycling. Ex-situ XAS reveals the electronic and atomic configurations of SnF2 at different potential states during dis/charging. The XAS results reveal that the valence change of Sn follows the conversion (SnF2 + 2Na → Sn + 2NaF) and the alloying (Sn + XNa → SnNaX) reaction upon sodium insertion into a composite.

A phosphorene-graphene hybrid material as a high-capacity anode for sodium-ion batteries.

Sodium-ion batteries have recently attracted significant attention as an alternative to lithium-ion batteries because sodium sources do not present the geopolitical issues that lithium sources might. Although recent reports on cathode materials for sodium-ion batteries have demonstrated performances comparable to their lithium-ion counterparts, the major scientific challenge for a competitive sodium-ion battery technology is to develop viable anode materials. Here we show that a hybrid material made out of a few phosphorene layers sandwiched between graphene layers shows a specific capacity of 2,440 mA h g(-1) (calculated using the mass of phosphorus only) at a current density of 0.05 A g(-1) and an 83% capacity retention after 100 cycles while operating between 0 and 1.5 V. Using in situ transmission electron microscopy and ex situ X-ray diffraction techniques, we explain the large capacity of our anode through a dual mechanism of intercalation of sodium ions along the x axis of the phosphorene layers followed by the formation of a Na3P alloy. The presence of graphene layers in the hybrid material works as a mechanical backbone and an electrical highway, ensuring that a suitable elastic buffer space accommodates the anisotropic expansion of phosphorene layers along the y and z axial directions for stable cycling operation.