Дисертації з теми "High capacity anode"

In this study we looked at several different silicon nanostructures grown for the purpose of optimizing anodes for lithium ion batteries. We primarily focused on two distinct types of structures, nanospirals, and Rugate structures. The samples were designed to have the mechanical robustness to endure the massive expansion caused by lithiation of silicon. All of the samples were grown using an electron beam evaporator. Scanning electron microscope images show that we have achieved the desired structural growth. The spirals were shown to have an average diameter of 343 nm on polished copper, and 366 nm on unpolished copper. The Rugate structures had two distinct sample sets. The first mimicked the design of a thin film. The other formed distinct pillars that grouped into islands. The tops of the islands had an average diameter of 362 nm, while the pillars had an average width varying between 167 nm and 140 nm.

This study sought to improve the performance of Si-based anodes through the use of hierarchically structured electrodes to provide the nanoscale framework needed to accommodate large volume changes while controlling the interfacial area – which affects solid-electrolyte interphase (SEI) formation. To accomplish this, electrodes were fabricated from vertically aligned carbon nanotubes (VACNT) infiltrated with silicon. On the nanoscale, these electrodes allowed us to adjust the surface area, tube diameter, and silicon layer thickness. On the micro-scale, we have the ability to control the electrode thickness and the incorporation of micro-sized features. Treatment of the interfacial area between the electrolyte and the electrode by encapsulating the electrode controls the stabilization and reduction of unstable SEI. Si-VACNT composite electrodes were prepared by first synthesizing VACNTs on Si wafers using photolithography for catalyst patterning, followed by aligned CNT growth. Nano-layers of silicon were then deposited on the aligned carbon nanotubes via LPCVD at 200mTorr and 535°C. A thin copper film was used as the current collector. Electrochemical testing was performed on the electrodes assembled in a CR2025 coin cell with a metallic Li foil as the counter electrode. The impact of the electrode structure on the capacity at various current densities was investigated. Experimental results demonstrated the importance of control over the superficial area between the electrolyte and the electrode on the performance of silicon-based electrodes for next generation lithium ion batteries. In addition, the results show that Si-VACNT height does not limit Li transport for the range of the conditions tested.

A prototype 3-dimensional (3D) anode, based on multiwall carbon nanotubes (MWCNTs), for Li-ion batteries (LIBs), with potential use in Electric Vehicles (EVs) was investigated. The unique 3D design of the anode allowed much higher areal mass density of MWCNTs as active materials, resulting in more amount of Li+ ion intake, compared to that of a conventional 2D counterpart. Furthermore, 3D amorphous Si/MWCNTs hybrid structure offered enhancement in electrochemical response (specific capacity 549 mAhg-1). Also, an anode stack was fabricated to further increase the areal or volumetric mass density of MWCNTs. An areal mass density of the anode stack 34.9 mg/cm2 was attained, which is 1,342% higher than the value for a single layer 2.6 mg/cm2. Furthermore, the binder-assisted and hot-pressed anode stack yielded the average reversible, stable gravimetric and volumetric specific capacities of 213 mAhg-1 and 265 mAh/cm3, respectively (at 0.5C). Moreover, a large-scale patterned novel flexible 3D MWCNTs-graphene-polyethylene terephthalate (PET) anode structure was prepared. It generated a reversible specific capacity of 153 mAhg-1 at 0.17C and cycling stability of 130 mAhg-1 up to 50 cycles at 1.7C.

We show full Li/S cells with the use of balanced and high capacity electrodes to address high power electro-mobile applications. The anode is made of an assembly comprising of silicon nanowires as active material densely and conformally grown on a 3D carbon mesh as a light-weight current collector, offering extremely high areal capacity for reversible Li storage of up to 9 mAh/cm(2). The dense growth is guaranteed by a versatile Au precursor developed for homogenous Au layer deposition on 3D substrates. In contrast to metallic Li, the presented system exhibits superior characteristics as an anode in Li/S batteries such as safe operation, long cycle life and easy handling. These anodes are combined with high area density S/C composite cathodes into a Li/S full-cell with an ether- and lithium triflate-based electrolyte for high ionic conductivity. The result is a highly cyclable full-cell with an areal capacity of 2.3 mAh/cm(2), a cyclability surpassing 450 cycles and capacity retention of 80% after 150 cycles (capacity loss <0.4% per cycle). A detailed physical and electrochemical investigation of the SiNW Li/S full-cell including in-operando synchrotron X-ray diffraction measurements reveals that the lower degradation is due to a lower self-reduction of polysulfides after continuous charging/discharging.

We show full Li/S cells with the use of balanced and high capacity electrodes to address high power electro-mobile applications. The anode is made of an assembly comprising of silicon nanowires as active material densely and conformally grown on a 3D carbon mesh as a light-weight current collector, offering extremely high areal capacity for reversible Li storage of up to 9 mAh/cm(2). The dense growth is guaranteed by a versatile Au precursor developed for homogenous Au layer deposition on 3D substrates. In contrast to metallic Li, the presented system exhibits superior characteristics as an anode in Li/S batteries such as safe operation, long cycle life and easy handling. These anodes are combined with high area density S/C composite cathodes into a Li/S full-cell with an ether- and lithium triflate-based electrolyte for high ionic conductivity. The result is a highly cyclable full-cell with an areal capacity of 2.3 mAh/cm(2), a cyclability surpassing 450 cycles and capacity retention of 80% after 150 cycles (capacity loss <0.4% per cycle). A detailed physical and electrochemical investigation of the SiNW Li/S full-cell including in-operando synchrotron X-ray diffraction measurements reveals that the lower degradation is due to a lower self-reduction of polysulfides after continuous charging/discharging.

Intermittent electricity generation from renewable energy sources, such as wind energy, ocean energy, and solar energy, has significantly intensified the demand for high-energy-density, high-power, and low-cost energy storage devices. In this regard, tremendous efforts have been devoted to the development of electrode materials, electrolytes, and separators of energy-storage devices to address the fundamental needs of emerging technologies such as electric vehicles, artificial intelligence, and virtual reality. Polymer materials are ubiquitous in fabricating these energy storage devices and are widely used as binders, electrolytes, separators, and other components. However, binders, as an important component in energy-storage devices, are yet to receive sufficient attention. Polyvinylidene fluoride (PVDF) has been the dominant binder in the battery industry for decades despite several well-recognized drawbacks, i.e., limited binding strength due to the lack of chemical bonds with electroactive materials, insufficient mechanical properties, and low electronic and lithium-ion conductivities. The limited binding function cannot meet the inherent demands of emerging electrode materials with high capacities such as silicon anodes and sulfur cathodes. Polymers are also used as electrolyte matrices because they offer the advantages of low cost, lightweight, easy processability, excellent mechanical deformation, and better interfacial contact and compatibility with electrodes. However, the practical implementation of solid polymer electrolytes has been hindered by several challenging issues including low ionic conductivity, low ion transfer number, high-voltage instability, and lithium dendrite growth. Because of the increasingly growing demand for higher performance of energy storage devices, it is necessary to develop novel polymeric binders and solid electrolytes with advanced functionalities to help improve the operation of the currently existing energy storage systems. In the first study, we synthesized a novel self-healing poly(ether-thioureas) (SHPET) polymer with balanced rigidity and softness for the silicon anode. The as-prepared silicon anode with the self-healing binder exhibits excellent structural stability and superior electrochemical performance, delivering a high discharge capacity of 3744 mAh g−1 at a current density of 420 mA g−1, and achieving a stable cycle life with a high capacity retention of 85.6% after 250 cycles at a high current rate of 4200 mA g−1. The success of this work suggests that the proposed SHPET binder facilitates fast self-healing, buffers the drastic volume changes and overcomes the mechanical strain in the course of the charge/discharge process, and could subsequently accelerate the commercialization of the silicon anode. Binders could play crucial or even decisive roles in the fabrication of low-cost, stable, and high-capacity electrodes. This is especially the case for the silicon (Si) anodes and sulfur (S) cathodes that undergo large volume change and active material loss in lithium-ion batteries during prolonged cycles. In the second study, a hydrophilic polymer poly(methyl vinyl ether-alt-maleic acid) (PMVEMA) was explored as a dual-functional aqueous binder for the preparation of high-performance silicon anodes and sulfur cathodes. Benefiting from the dual functions of PMVEMA, i.e., the excellent dispersion ability and strong binding forces, the as-prepared electrodes exhibit improved capacity, rate capability, and long-term cycling performance. In particular, the as-prepared Si electrode delivers a high initial discharge capacity of 1346.5 mAh g-1 at a high rate of 8.4 A g-1 and maintains 834.5 mAh g-1 after 300 cycles at 4.2 A g-1, while the as-prepared S cathode exhibits enhanced cycling performance with high remaining discharge capacities of 711.44 mAh g-1 after 60 cycles at 0.2 C and 487.07 mAh g-1 after 300 cycles at 1 C, respectively. These encouraging results suggest that PMVEMA could be a universal binder to facilitate the green manufacture of both anodes and cathodes for high-capacity energy storage systems. Stable and seamless interfaces among solid components in all‐solid‐state batteries (ASSBs) are crucial for high ionic conductivity and high rate performance. This can be achieved by the combination of functional inorganic material and flexible polymer solid electrolytes. In the third study, a flexible all‐solid‐state composite electrolyte is synthesized based on oxygen‐vacancy‐rich Ca‐doped CeO2 (Ca-CeO2) nanotube, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and poly(ethylene oxide) (PEO), namely Ca-CeO2/LiTFSI/PEO. Ca-CeO2 nanotubes play a key role in enhancing ionic conductivity and mechanical strength while the PEO offers flexibility and assures the stable seamless contact between the solid electrolyte and the electrodes in ASSBs. The as‐prepared electrolyte exhibits high ionic conductivity of 1.3 × 10−4 S cm−1 at 60 °C, a high lithium ion transference number of 0.453, and high‐voltage stability. More importantly, various electrochemical characterizations and density functional theory (DFT) calculations reveal that Ca-CeO2 helps dissociate LiTFSI, produces free Li-ions, and therefore enhances ionic conductivity. The ASSBs based on the as‐prepared Ca-CeO2/LiTFSI/PEO composite electrolyte deliver high‐rate capability and high‐voltage stability. Offering high energy density and high safety, all-solid-state lithium-sulfur batteries (ASSLSBs) have emerged as one of the most promising next-generation energy storage systems. However, there are a series of barriers to their practical applications, including insufficient sulfur utilization, low ionic conductivity and unstable interfaces. In the fourth study, we adopt acetamide to construct a deep eutectic system to suppress electrode passivation, and therefore address the issues of sulfur utilization, and improve the ionic conductivity of the solid polymer electrolytes. Furthermore, we establish a lithium bis(trifluoromethanesulfonyl)imide - lithium oxalyldifluoroborate (LiTFSI-LiDFOB) dual-salt system to facilitate the establishment of a stable and uniform passivation layer, a favorable interface on lithium anode, to prevent lithium dendrite formation and the polysulfide shuttling. Consequently, the as-prepared ASSLSBs deliver a high initial discharge specific capacity of 1012 mAh g-1 at 0.05 C and a stable capacity of 234.84 mAh g-1 after 1000 cycles at 0.1 C. This work suggests that the simultaneous adoption of the deep eutectic system and dual-salt electrolyte could accelerate the practical applications of ASSLSBs. In summary, the high performance of the as-prepared silicon anodes demonstrates potential for addressing the challenges for next-generation anodes by designing self-healing polymers and aqueous hydrophilic polymers. Moreover, the success of the aqueous hydrophilic polymer in lithium-sulfur batteries suggests that such a binder system can be extended to other high-capacity energy storage materials that suffer from severe volume changes. As for the polymer electrolytes, the design of functional inorganic/polymeric composite electrolyte presents a promising strategy to resolve the stubborn barriers (i.e., insufficient contact at the interfaces and ionic conductivity) of ASSBs. Additionally, combining the merits of the deep eutectic system and the dual-salt system, long-term cycling stability and high capacity retention of ASSLSBs can be achieved. These polymeric binders and electrolytes can be further optimized to realize high performance for various energy storage systems.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Environment and Sc
Science, Environment, Engineering and Technology
Full Text

碩士
國立中央大學
化學工程與材料工程研究所
91
This thesis describes the structural and lithium-insertion properties of pyrolytic carbons derived from peanut shells. Peanut shells were treated with different weight ratios of a proprietary porogenic agent and carbonized between 600 and 900°C. The work covers three areas: (1) optimization of the porogen-to-peanut shell weight ratio (P) and the pyrolysis temperature, (2) comparison of the lithium-insertion properties of carbons obtained from untreated and porogen-treated peanut shells, and (3) charge-discharge studies with pre-lithiated carbons. Porogen treatment was implemented in order to alter the pore structure and effect a manifold increase in the surface area of the carbonaceous product. Both the untreated and porogen-treated shells yielded carbons with poor crystallinity, but the pore diameter of the latter was twice as large and the surface area was 66 times greater than the untreated carbon. Both types of products were primarily non-parallel single sheets of carbons, as determined by the values of their R factors. While porogen can increase the number of uncorrelated graphene fragments, leading to more lithium accommodation sites, the pyrolysis temperature can induce breakage of the links between adjacent sheets and encourage their parallel alignment. The products obtained with P = 5 at 500°C gave a first-cycle lithium insertion capacity of 4765 mAh/g, which is the highest value reported for any lithium-insertion material so far. At a pyrolysis temperature of 600°C, the P = 5 product gave the optimal insertion and deinsertion capacities, their values in the first cycle being 3504 and 1650 mAh/g, respectively. The deinsertion capacity of this sample in the tenth cycle was very high at 1504 mAh/g. However, the irreversible capacities of these carbons, especially in the first cycle, were too large to be practical. The large irreversible capacities were reflected in the cyclic voltammograms of the carbons, where the absence of a significant anodic peak indicated that only part of the inserted lithium could be retrieved. In the case of the P = 0 carbon, lithium insertion was observed below 0.7 V vs. Li+/Li, while in the P = 5 carbon, the insertion process commenced from about 1.3 V. Moreover, the decrease in the insertion current with cycle number was lower in the case of the porogen-treated carbon than with the untreated carbon, suggesting the former had better capacity retention. No distinguishable current peaks were seen in the cyclic voltammograms, indicating lack of any long-range ordering, which precludes staging behavior during the insertion and deinsertion processes. The P = 5 carbon also exhibited higher exchange current densities, which would imply that the kinetics of the insertion reaction was faster than when the carbon was untreated. Electrochemical impedance studies showed that the resistance due to the formation of surface film increased when the carbon was charged. However, the slight increase in resistance suggests that the products of the surface reduction are either soluble in the electrolyte or are loosely held to the surface. Charge-discharge studies with the porogen-treated carbon, pre-charged and discharged prior to use in coin cells, indicated that the first-cycle reversible capacity was the greatest when the charge-discharge rate was 0.4 C. At this rate, the carbon maintained capacities of about 325 mAh/g for 20 cycles, and then stabilized at around 380 mAh/g for over 70 cycles. Signature curves of the carbon showed that the deliverable capacities at charge-discharge rates of 0.2, 0.4, 0.8 C were 900, 700 and 500 mAh/g, respectively. Even at the 1.6 C rate, more than 300 mAh/g could be tapped from the carbon after 130 cycles.

Lithium-ion batteries(LIBs) have dominated the energy storage market in the past two decades. The high specific energy, low self-discharge, relatively high power and low maintenance of LIBs enabled the revolution of electronic devices and electric vehicle industry, changed the communication and transportation styles of the modern world. Although the specific energy of LIBs has increased significantly since first commercialized in 1991, it has reached a bottleneck with current electrode materials. To meet the increasing market demand, it is necessary to develop high capacity electrode materials.

碩士
國立高雄應用科技大學
化學工程與材料工程系
97
In this study, the iron oxide (α-Fe2O3) active materials are synthesized by electrochemical deposition and chemical precipitation methods, respectively. In addition, the iron oxide was coated on the surface of carbon fiber (VGCF) to form α-Fe2O3/VGCF composite electrode as an anode material for high-capacity Li-ion batteries. In the first part, the iron oxide film and α-Fe2O3/VGCF composite electrodes are prepared by electrochemical deposition method. The effects of different deposition current densities (0.025 and 0.125 mA cm-2) on the material characteristics and electrochemical performances of iron oxide electrode are investigated. According to the SEM analysis, the iron oxide film deposited at low-current density (0.025 mA cm-2) is rod-like morphology and that deposited at high-current density (0.125 mA cm-2) is sheet-like morphology. During the first charge-discharge process, the reversible capacity of films deposited at 0.025 and 0.125 mA cm−2 are 1390 and 1275 mAh g-1, respectively; At 10 C rate, the reversible capacity are 803 and 797 mAh g-1, respectively. The synthesized anode materials have a higher capacity than the graphite material for lithium storage. The SEM and XRD results indicate that iron oxide films are uniformly coated on the surface of carbon fiber by means of electrochemical deposition process. Compared with iron oxide electrode (deposited at 0.125 mA cm-2), the reversible capacity of α-Fe2O3/VGCF composite electrodes are increased by 17.9 % in first charge-discharge process and 12 % at 10 C rate. The results show that carbon fiber can improve the electrochemical performance of the composite electrodes effectively. In the second part, the iron oxide powder is synthesized by chemical precipitation method and is deposited onto the stainless steel substrate by electrophoretic deposition to form iron oxide film and α-Fe2O3/VGCF composite electrodes. The effects of different precursors [Fe(NH4)2(SO4)2．6H2O and FeCl3．6H2O] on the material characteristics and electrochemical performances of the iron oxide electrode is investigated. According to the SEM analysis, when the precursors are Fe(NH4)2(SO4)2．6H2O and FeCl3．6H2O, the morphologies of resulting iron oxide powder are nanorod and nanoparticles, respectively. The TG-DTA and XRD results indicate that FeOOH is fully converted into α-Fe2O3 when the annealing temperature is elevated to 400℃. During the first charge-discharge process, the reversible capacity of films for Fe(NH4)2(SO4)2．6H2O and FeCl3．6H2O are 1390 and 1275 mAh g-1, respectively; At 10 C rate, the reversible capacity are 713 and 503 mAh g-1, respectively. Compared with iron oxide electrode [Fe(NH4)2(SO4)2．6H2O], the reversible capacity of α-Fe2O3/VGCF composite electrodes are increased by 16.2 % in first charge-discharge process and 11.8 % at 10 C rate.

博士
國立交通大學
應用化學系碩博士班
103
In this studies, we demonstrate the synthesis of tin-based nanostructures include SnO2 nanorods (NRs), hollow spheres (HSs), nanosheets (NSs) and Sn@C core-shell nanowires (NWs) without the usage of template and catalysts. Growth mechanism and electrochemical properties of tin-based samples were also investigated. First, phase-segregated SnO2 nanorods (NRs, length 1-2 m and diameter 10-20 nm) were developed in a matrix of CaCl2 salt by reacting CaO particles with a flowing mixture of SnCl4 and Ar gases at elevated temperatures via a vapor–solid reaction growth (VSRG) pathway. And developed a facile hydrothermal method to synthesize SnO2 hollow spheres (HSs) and nanosheets (NSs). The morphologies and structures of SnO2 could be controlled by Sn+4/+2 precursors. The shell thickness of the HSs was around 200 nm with diameter 1-3 μm, while thickness of the NSs was 40 nm. The correlation between the morphological characteristics and the electrochemical properties of SnO2 NRs, HSs and NSs were discussed. The SnO2 nanomaterials were investigated as a potential anode material for Li-ion batteries (LIBs). SnO2 NRs, HSs and NSs exhibit superior electrochemical performance and deliver 435, 522 and 490 mA h g−1 up to the one hundred cycles at a current density of 100 mA g-1 (0.13 C), which is ascribed to the unique structure of SnO2 which be surrounded in the inactive amorphous byproduct matrix. The matrix probably buffered and reduced the stress caused by the volume change of the electrode during the charge-discharge cyclings. Development tin-based nanocomposites containing suitably chosen matrix elements to achieve higher performance and reduce irreversibility processes. Designed strategy to fabricate a novel tin-carbon nanocomposites as electrodes of LIBs. Sn@C core-shell nanowires (NWs) were synthesized by reacting SnO2 particles with a flowing mixture of C2H2 and Ar gases at elevated temperatures. The overall diameter of the core–shell nanostructure was 100-350 nm. The C shell thickness was 30-70 nm. The NW length was several micrometers. Inside the shell, a void space was found. The reaction is proposed to be via a vapor–solid reaction growth (VSRG) pathway. The NWs were investigated as a potential anode material for Li-ion batteries (LIBs). The half-cell constructed from the as-fabricated electrode and a Li foil exhibited a reversible capacity of 525 mA h g-1 after one hundred cycles at a current density of 100 mA g-1. At a current density as high as 1000 mA g-1, the battery still maintained a capacity of 486 mA h g-1. The excellent performance is attributed to the unique 1D core-shell morphology. The core-shell structure and the void space inside the shell can accommodate large volume changes caused by the formation and decomposition of LixSn alloys in the charge-discharge steps.

Colloidally synthesized silicon (Si) and germanium (Ge) were explored as high capacity anode materials in lithium ion batteries. a-Si:H particles were synthesized through the thermal decomposition of trisilane in supercritical n-hexane. Precise control over particle size and hydrogen content was demonstrated. Particles ranged in size from 240-1500 nm with hydrogen contents from 10-60 atomic%. Particles with low hydrogen content had some degree of local ordering and were easily crystallized during Raman spectroscopy. The as-synthesized particles did not perform well as an anode material due to low conductivity. Increasing surface conductivity led to enhanced lithiation potential. Cu nanoparticles were deposited on the surface of the a-Si:H particles through a hydrogen facilitated reduction of Cu salts. The resulting Cu coated particles had a lithiation capacity seven times that of pristine a-Si:H particles. Monophenylsilane (MPS) grown Si nanowire paper was annealed under forming gas to reduce a polyphenylsilane shell into conductive carbon. The resulting paper required no binder or carbon additive and achieved capacities of 804 mA h/g vs 8 mA h/g for unannealed wires. Si and Ge heterostructures were explored to take advantage of the higher inherent conductivity of Ge. Ge nanowires were successfully coated with a-Si by thermal decomposition of trisilane on their surface, forming Ge@a-Si core shell structures. The capacity increased with increasing Si loading. The peak lithiation capacity was 1850 mA h/g after 20 cycles – higher than the theoretical capacity of pure Ge. MPS additives created a thin amorphous shell on the wire surfaces. By incubating the wires after MPS addition the shell was partially reduced, conductivity increased, and a 75% increase in lithiation capacity was observed for the nanowire paper. The syntheses of Bi and Au nanoparticles were also explored. Highly monodisperse Bi nanocrystals were produced with size control from 6-18 nm. The Bi was utilized as seeds for the SLS synthesis of Ge nanorods and copper indium diselenide (CuInSe2) nanowires. Sub 2 nm Au nanocrystals were synthesized. A SQUID magnetometer probed their magnetic behavior. Though bulk Au is diamagnetic, the Au particles were paramagnetic. Magnetic susceptibility increased with decreasing particle diameter.
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碩士
國立臺灣師範大學
化學系
101
In recent years, FeS2 (natural pyrite) has been widely studied and considered to be potential electrode in the anode material for lithium-ion batteries, because some of the iron disulfide itself good properties and advantages, such as high theoretical capacity, no toxicity for low environmental impact and low cost. However, due to the lithium metal is very expensive material, secondary battery focuses on the development of low-cost battery. Sodium-ion battery is considered to be quite consistent with a choice, because of the low cost price of the sodium metal, high theoretical capacity, etc. It is possible to completely replace the similar properties of the lithium metal. But in fact, the low energy density, low output potential and capacity restriction are the problems encountered by the sodium-ion battery. In this thesis, we find a suitable electrode material to improve cycle stability and high capacity at high charge-discharge rate of the sodium-ion batteries. Therefore, this study focused on the natural iron disulfide material used in the sodium-ion battery anode. We found that iron disulfide as anodic materials of sodium-ion battery (FeS2-NIB) has demonstrated the first discharge and charge capacity of 730 mAh g-1 and 584 mAh g-1 at a current density of 50 mA g-1. The irreversible capacity of first cycle is approximately 20%. Especially, the irreversible capacity of charge-discharge process after second cycle is much less. The capacity of FeS2-NIB still remained 400 mAh g-1 after 50th cycles. During rapid charge-discharge test, FeS2-NIB have high capacity of 280 mAh g-1 at a current density of 8920 mA g-1. Overall results showed that the pure iron disulfide as anodic materials of sodium-ion battery demonstrated long cycle performance, high coulombic efficiency and good capacity retention at high charge-discharge rate. The results indicate that earth-abundant FeS2 is an extremely interesting candidate as anode materials of sodium-ion battery with a suitable electrolyte for fast intercalate/deintercalate Na ion reversibly.