Na-storage Capacity Research Articles

Irida-graphene as a high-performance anode for sodium batteries

Clean energy storage is in the spotlight of the scientific community, as is the development of alternatives to the negative impact of conventional lithium-based batteries; therefore, sodium-ion batteries (SIBs) have emerged due to the abundant Na resources. In this sense, the performance of irida-graphene (IG), a 2D carbon allotrope with metallic character, and geometrically formed by 3-, 6- and 8- carbon rings, is computationally investigated for Na storage by density functional theory (DFT) simulations. The maximum Na capacity in the IG is 24 atoms, a ratio of 1 Na to 2C (1:2), with adsorption energies from −1.42 eV (single Na) to −0.38 eV (24 Na), demonstrating its electrochemical stability. The Na mobility was analyzed, indicating a high diffusion rate (3.11 × 10−5 cm2/s at 300 K) associated with a very small diffusion barrier (0.09 eV). The operating open circuit voltage (OCV) ranges from 0.32 to 1.42 V, which is suitable for a safety battery application. Finally, the Na storage capacity is 1022 mAhg−1, surpassing many commercial anodes and competitive with other structures. The results highlight the IG potential as an effective and safe anode material for SIBs.

Microcrystalline Engineering of Anthracite-Based Carbon Via Salt-Assisted Ball Milling for Enhanced Sodium Storage Performance.

Coal-based carbon material, characterized by abundant resources and low cost, has gained considerable interests as a promising anode candidate for sodium-ion batteries (SIBs). However, the coal-based carbon generally shows inferior Na-storage performance due to its highly-ordered microstructure with narrow interlayer spacing. Herein, a salt-assisted mechanical ball-milling strategy is proposed to disrupt the polycyclic aromatic hydrocarbon structure in anthracite molecules, thereby reducing the microcrystalline regularity of the derived carbon during following pyrolysis process. In addition, the induced C─O─C bonds during ball-milling process can alter the pyrolysis behavior of anthracite and restrain the formation of surface defects. Consequently, in contrast to pristine anthracite-based pyrolytic carbon, which exhibits a Na-storage capacity of 198.4 mAh g-1 with a low initial Coulombic efficiency (ICE) of 65.1%, the ball-milling modified carbon assisted by NaCl salt (NAC), with enhanced structural disordering and reduced surface defects, demonstrate significantly improved Na-storage capacity of 332.1 mAh g-1 and ICE value of 82.0%. The NAC electrode also realizes excellent cycle and rate performance, retaining a capacity of 196.0 mAh g-1 at 1 C after 1000 cycles. Furthermore, when coupled with NaNi1/3Fe1/3Mn1/3O2 cathode, the assembled Na-ion full cell deliveres an exceptional electrochemical performance, highlighting its promising prospect as high-performance anode for SIBs.

Insights into Na ion adsorption and diffusion in biphenylene as an anode material for sodium-ion batteries: A first-principles study

Anode materials are essential for the advancement of sodium-ion batteries (NIBs). This study comprehensively evaluates the biphenylene network (BP) as a promising anode material using first-principles calculations. Density functional theory (DFT) results reveal that sodium (Na) ions stably adsorb on BP surfaces, with adsorption energies ranging from −1.29 eV to −2.92 eV, due to effective charge transfer and hybridization between Na (s) and carbon (p) orbitals. The diffusion barriers for Na ion migration are 0.31 eV for the monolayer and 0.76 eV for the bilayer, with optimal paths involving the C8-ring and passing through C6- or C4-rings. Notably, edge sites were found to provide strong Na adsorption on monolayer BP nanoribbon, with low diffusion barriers (0.36 eV), revealing the critical role of edge configurations in enhancing the BP performance as an anode material. The theoretical capacity of Na on the BP monolayer is 908.52 mAh·g⁻¹, surpassing many other two-dimensional materials, and the average open circuit voltage (OCV) is 0.64 V. Overall, BP offers high Na storage capacity, low diffusion barriers, and suitable OCV, positioning it as a strong candidate for high-performance NIB anodes.

Hybrid of sub-1 nm single-dispersed polyoxometalate and reduced graphene oxide as advanced anodes for durable sodium-ion batteries

Polyoxometalates (POMs) are widely thought as promising choices for sodium-ion batteries (SIBs) because of their refined molecular structures and excellent reversible multielectron charge-discharge behaviors. Nevertheless, the POMs anion clusters could dissolve in the electrolyte when attacked by solvent molecules, thus reducing active sites and affecting the actual performance of these POMs-based electrodes. Herein, we report the development of a new type of electrode system that produces single-dispersed POMs molecular cluster/polydopamine/reduced graphene oxide composites ({PMo12}/PDA@rGO) through a self-assembly method. PDA acts as the role of “killing two birds with one stone”. It not only works as the linker to promote the formation of stable and uniform monodisperse {PMo12} clusters on the rGO surface, but also prevents the POMs from desorbing and dissolving upon deep cycling test. As a consequence, when used as the anode material for SIBs, the obtained {PMo12}/PDA@rGO exhibits an admirable long-term cycling performance, for instance, it holds a high Na-storage capacity of 277.5 mAh g−1 with an average Coulomb efficiency up to 99.89 % over 2000 cycles at 1 A g−1. This work offers versatile possibilities for designing POMs-based composites and provides new insight into developing single dispersed POMs for advanced SIBs.

First-Principles Calculations of TiB4 and TiB5 as Anodes with High Capacity for Na-Ion Batteries.

The electrochemical properties of TiB4 and TiB5 monolayers in Na-ion batteries (NIBs) were studied by using the first-principles calculation method based on density functional theory. The TiB4/TiB5 monolayer showed excellent Na storage capacity, capable of adsorbing two layers of Na with theoretical capacities of 1176.77 and 1052.05 mA g-1, respectively. The average operating voltages of the TiB4 and TiB5 monolayers are 0.073 and 0.042 eV, respectively, indicating that they can be used as anode materials for NIBs. More interestingly, the exposed B surface not only brings a high theoretical capacity but also provides a relatively small diffusion barrier of 0.16 (for TiB4) and 0.33 eV (for TiB5), enhancing their rate capability in NIBs.

Cyclic Ether Derived Stable Solid Electrolyte Interphase on Bismuth Anodes for Ultrahigh-Rate Sodium-Ion Storage.

The bismuth anode has garnered significant attention due to its high theoretical Na-storage capacity (386mAh g-1). There have been numerous research reports on the stable solid electrolyte interphase (SEI) facilitated by electrolytes utilizing ether solvents. In this contribution, cyclic tetrahydrofuran (THF) and 2-methyltetrahydrofuran (MeTHF) ethers are employed as solvents to investigate the sodium-ion storage properties of bismuth anodes. A series of detailed characterizations are utilized to analyze the impact of electrolyte solvation structure and SEI chemical composition on the kinetics of sodium-ion storage. The findings reveal that bismuth anodes in both THF and MeTHF-based electrolytes exhibit exceptional rate performance at low current densities, but in THF-based electrolytes, the reversible capacity is higher at high current densities (316.7mAh g-1 in THF compared to 9.7mAh g-1 in MeTHF at 50A g-1). This stark difference is attributed to the formation of an inorganic-rich, thin, and uniform SEI derived from THF-based electrolyte. Although the SEI derived from MeTHF-based electrolyte also consists predominantly of inorganic components, it is thicker and contains more organic species compared to the THF-derived SEI, impeding charge transfer and ion diffusion. This study offers valuable insights into the utilization of cyclic ether electrolytes for Na-ion batteries.

Heterogeneous MoS2 Nanosheets on Porous TiO2 Nanofibers toward Fast and Reversible Sodium-Ion Storage.

2D layered molybdenum disulfide (MoS2) has garnered considerable attention as an attractive electrode material in sodium-ion batteries (SIBs), but sluggish mass transfer kinetic and capacity fading make it suffer from inferior cycle capability. Herein, hierarchical MoS2 nanosheets decorated porous TiO2 nanofibers (MoS2 NSs@TiO2 NFs) with rich oxygen vacancies are engineered by microemulsion electrospinning method and subsequent hydrothermal/heat treatment. The MoS2 NSs@TiO2 NFs improves ion/electron transport kinetic and long-term cycling performance through distinctive porous structure and heterogeneous component. Consequently, the electrode exhibits excellent long-term Na storage capacity (298.4mAhg-1 at 5Ag-1 over 1100 cycles and 235.6mAhg-1 at 10Ag-1 over 7200 cycles). Employing Na3V2(PO4)3 as cathode, the full cell maintains a desirable capacity of 269.6mAhg-1 over 700 cycles at 1.0Ag-1. The stepwise intercalation-conversion and insertion/extraction endows outstanding Na+ storage performance, which yields valuable insight into the advancement of fast-charging and long-cycle life SIBs anode materials.

High Thiophene-S doped soft carbons for sodium storage

S-doped carbon materials with both low cost and high capacity are one of the best choices for large-scale sodium storage. However, conventional S doping strategies often fail to obtain a high S concentration and accurately control the doping forms of sulfur, which restricts the Na-storage performance and mechanism revelation of materials. Here, low-cost pitch-derived soft carbons with ultrahigh surface-S doping (12.19 at%) and thiophene-S ratio approaching 95 % (CSC95) are accurately synthesized by a modified sulfate pyrolysis strategy. Density functional theory calculations indicate that thiophene-S is an ideal doping form that can form reversible Na-S bonds, which is beneficial for improving the Na-adsorption and storage ability for the materials. The rich thiophene-S regulates the local charge density to improve the electrical conductivity of CSC95. More importantly, the highly reversible redox reactions between thiophene-S and Na+ dominate the Na-storage process. In addition, the hierarchically porous structure of CSC95 provides moderate surface area and ion diffusion channels to ensure the fast Na-storage kinetics. As expected, CSC95 deliver a high Na-storage capacity of 574.5 and 187.7 mAh g−1 at 0.2 and 10 A g−1, respectively, and remarkable cyclability of 77.4 % capacity retention for 800 cycles at 10 A g−1. Moreover, Na3V2(PO4)2F3@C (NVPF@C)//CSC95 full cells display gravimetric energy density of 217 Wh kg−1 at 0.1C and 89.4 % capacity retention after 120 cycles at 1C.

Janus SnXY (X/Y = O, S, Se, Te, X ≠ Y) monolayers for sodium ion storage anodes: In view of first principles understanding

The exploration of two-dimensional (2D) anode materials with fascinating theoretical specific capacity and ion diffusion rate has been paid much attention in the domain of alkali ion batteries. In this present contribution, the potency of monolayer Janus SnXY (X/Y = O, S, Se, Te, X ≠ Y) to function as an anode material for Na-ion batteries (SIBs) is anticipated upon the ground of first-principles calculations. The outcomes indicate that the cohesion energies of all the SnXY are positive, signifying that they are energetically stabilized. The distribution of electrons in the SnXY structure is strongly dependent on the electronegativity of the atoms on both sides, and the higher the electronegativity, the more electrons are gathered. Meanwhile, the larger (smaller) charge transfer between Sn atoms and X/Y atoms enhances (weakens) the bond strength and leads to a decrease (increase) in the interlayer spacing. In service, Na atoms tend to be steadily adsorbed at the top of O, Sn, Se and Te, and a large number of electrons are transferred from Na atoms to SnXY. SnXY exhibits a metallic state after embedding, increasing its own electrical conductivity. Particularly, the SnSSe has a low diffusion barrier of 0.12 eV and a high Na storage capacity of 1380 mAh/g. These insights demonstrate that monolayer Janus SnXY is a prospective anode material for SIBs possessing high storage capacity and rapid charge/discharge rates.

Density Functional Theory Analysis of the Impact of Boron Concentration and Surface Oxidation in Boron-Doped Graphene for Sodium and Aluminum Storage

Graphene is thought to be a promising material for many applications. However, pristine graphene is not suitable for most electrochemical devices, where defect engineering is crucial for its performance. We demonstrate how the boron doping of graphene can alter its reactivity, electrical conductivity and potential application for sodium and aluminum storage, with an emphasis on novel metal-ion batteries. Using Density Functional Theory calculations, we investigate both the influence of boron concentration and the oxidation of the material on the mentioned properties. It is demonstrated that the presence of boron in graphene increases its reactivity towards atomic hydrogen and oxygen-containing species; in other words, it makes B-doped graphene more prone to oxidation. Additionally, the presence of these surface functional groups significantly alters the type and strength of the interaction of Na and Al with the given materials. Boron-doping and the oxidation of graphene is found to increase the Na storage capacity of graphene by a factor of up to four, and the calculated sodiation potentials indicate the possibility of using these materials as electrode materials in high-voltage Na-ion batteries.

Na-storage reactions of rutile TiNbO4

As a novel anode material for Na-ion battery, we evaluated rutile-type TiNbO4 synthesized by a sol−gel method. It was revealed for the first time that TiNbO4 showed reversible reactions of Na+-insertion and Na+-extraction in the potential ranges of 0.005–1.0 and 0.6–1.6 V vs. Na+/Na, respectively. TiNbO4 maintained its rutile structure even after charge−discharge cycling. The size of Na+ diffusion path along its c-axis was broadened with increasing Nb amount in TiNbO4, leading to the improvement in the reversible capacity. The TiNbO4 electrode with Nb 48 at.% exhibited a high capacity of 360 mA h g−1. The long-term cyclability and rate capability were also improved by increasing Nb amount. We consider that the wider space in the diffusion path increases the degree of freedom of Na+ occupancy position, which weakens the electrostatic repulsion between Na+ and Na+ to increase Na storage capacity. These results clearly demonstrate that TiNbO4 can be applied as a promising anode material.

Facile and Scalable Development of High-Performance Carbon-Free Tin-Based Anodes for Sodium-Ion Batteries.

Tin (Sn)-based anodes for sodium (Na)-ion batteries possess higher Na-storage capacity and better safety aspects compared to hard carbon -based anodes but suffer from poor cyclic stability due to volume expansion/contraction and concomitant loss in mechanical integrity during sodiation/desodiation. To address this, the usage of nanoscaled electrode-active particles and nanoscaled-carbon-based buffers has been explored, but with compromises with the tap density, accrued irreversible surface reactions, overall capacity (for "inactive" carbon), and adoption of non-scalable/complex preparation routes. Against this backdrop, anode-active "layered" bismuth (Bi) has been incorporated with Sn via a facile-cum-scalable mechanical-milling approach, leading to individual electrode-active particles being composed of well-dispersed Sn and Bi phases. The optimized carbon-free Sn-Bi compositions, benefiting from the combined effects of "buffering" action and faster Na transport of Bi, to go with the greater Na-storage capacity and lower operating potential of Sn, exhibit excellent cyclic stability (viz., ∼83-92% capacity retention after 200 cycles at 1C) and rate capability (viz., no capacity drop from C/5 to 2C, with only ∼25% drop at 5C), despite having fairly coarse particles (∼5-10 μm). As proven by operando synchrotron X-ray diffraction and stress measurements, the sequential sodiation/desodiation of the components and, concomitantly, stress build-ups at different potentials provide "buffering" action even for such "active-active" Sn-Bi compositions. Furthermore, the overall stress development upon sodiation of Bi has been found to be significantly lower than that of Sn (by a factor of ∼3.8), which renders Bi promising as a "buffer" material, in general. Dissemination of such complex interplay between electrode-active components during electrochemical cycling also paves the way for the development of high-performance, safe, and scalable "alloying-reaction"-based anode materials for Na-ion batteries and beyond, sans the need for ultrafine/nanoscaled electrode particles or "inactive" nanoscaled-carbon-based "buffer" materials.

Na vacancies and Li doping synergistically constructed P2-type Na0.5Li0.1Ni0.2Mn0.7O2 as high-performance cathode material for sodium-ion batteries

P2-type Na-Ni-Mn layered oxides are potential cathode materials for energy storage in sodium-ion batteries, but have low cycling stability and limited Na storage capacity due to complex phase transitions. Herein, co-regulating vacancies and doping were implemented to address the issue, resulting in the successful synthesis of hexagonal columnar P2-Na0.5Li0.1Ni0.2Mn0.7O2 through a solid-state synthesis method. Increased interlayer spacing of Na+ can offer numerous active sites for Na+ insertion and extraction. P2-Na0.5Li0.1Ni0.2Mn0.7O2 exhibits an impressive initial discharge capacity of 139.1 mAh g−1 and 78.5 % capacity retention after 100cycles at 1.0C, which is a significant improvement compared to the pristine Na0.7Ni0.3Mn0.7O2. Overall, our study significantly boosts the electrochemical performance of P2-type materials, thus offering exciting avenues for the advancement of high-performance sodium-ion batteries.

Application of T4,4,4-graphyne for anode of Na-ion battery: first principle theoretical study

ABSTRACT The sodium (Na) storage behaviour of T4,4,4-graphyne of two-dimensional porous carbon sheet is explored using the density functional theory (DFT). The energy of adsorption and barrier, storage capacity, and open-circuit voltage are calculated. The calculations predict that Na atom is extraordinary mobile on T4,4,4-graphyne monolayer as a result of the relatively slight energy barrier. The Na storage capacity is as high as Na8C9, which exceeds the values reported for graphite and some other two-dimensional carbon-based materials. The high Na mobility and theoretical capacity make T4,4,4-graphyne monolayer suitable for implementation in rechargeable ion batteries. The electronic properties are also studied to ensure that T4,4,4-graphyne is suitable for Na-ion batteries as an anode material, and they revealed that semiconductor–metal transition is induced by Na adsorption. The favourable electronic conduction is another demand for promising Na-ion batteries. These results predict that the application of T4,4,4-graphyne sheet will increase efficiency of the Na-ion batteries.

Honeycomb-kagome FSL-graphene: A carbon allotrope as an ultra-high capacity anode material for fast-rechargeable sodium-ion battery

Sodium-ion batteries (SIBs) are promising candidates for large-scale energy storage due to the abundance and low cost of sodium. However, graphite, the primary anode for commercial lithium-ion batteries, cannot be applied to SIBs. Its two-dimensional (2D) counterpart graphene is also inactive toward Na ions because of the delocalized π-electron network. We propose an idea to tackle this problem by introducing kagome topology into the honeycomb lattice, creating localized electronic states for improving the Na storage performance. Herein, we design a form of 2D carbon allotrope (named FSL-graphene), consisting of a kagome and a honeycomb sublattice. It has excellent stability, which is confirmed by the superior cohesive energy, positive phonon modes, high thermal stability, and strong mechanical stability. FSL-graphene exhibits an ultra-high theoretical Na storage capacity of 3347.1 mA h g−1, superior to most previously reported 2D anode materials. In addition, it possesses low diffusion energy barriers (0.19–0.23 eV), low open-circuit voltages (0.59–0.61 V), and small changes in lattice constants (1.3%). Furthermore, the electrolytes with high dielectric constants (e.g., ethylene carbonate) could improve the adsorption and migration of Na on FSL-graphene. This study provides an insight for designing high-performance carbon anode materials for SIBs by focusing on the topological lattices.

Compact TiO2@SnO2@C heterostructured particles as anode materials for sodium-ion batteries with improved volumetric capacity

Sodium-ion batteries (SIBs) are promising candidates for large-scale energy storage. Increasing the energy density of SIBs demands anode materials with high gravimetric and volumetric capacity. To overcome the drawback of low density of conventional nanosized or porous electrode materials, compact heterostructured particles are developed in this work with improved Na storage capacity by volume, which are composed of SnO2 nanoparticles loaded into nanoporous TiO2 followed by carbon coating. The resulted TiO2@SnO2@C (denoted as TSC) particles inherit the structural integrity of TiO2 and extra capacity contribution from SnO2, delivering a volumetric capacity of 393 mAh cm-3 notably higher than that of porous TiO2 and commercial hard carbon. The heterogeneous interface between TiO2 and SnO2 is believed to promote the charge transfer and facilitate the redox reactions in the compact heterogeneous particles. This work demonstrates a useful strategy for electrode materials with high volumetric capacity.

The CrBr3 monolayer: Two dimension sodium ion battery anode material to characterize state-of-charge by magnetism

Ion batteries always use the charge properties of electron to estimate the state-of-charge. In this work, we predict that CrBr3 monolayers can be used as anode materials for sodium ion batteries to characterize state-of-charge of corresponding ion batteries by magnetism. According to the first-principles calculations based on density functional theory, the available maximum Na storage capacity of CrBr3 monolayer can reach 795 mAh/g with the ultra-low open circuit voltage (∼0.02 V). Na ions have good diffusion properties in the CrBr3 monolayer, and the corresponding diffusion barrier is about to be 0.22 eV. There is a magnetic configuration transition in CrBr3 monolayer during charge/discharge, which arises from the change in the occupation of Cr-d orbitals. Our results shed a light to subsequently design and search for anode materials, suggesting that the magnetic properties of electrode materials could provide a new path to monitor the state-of-charge of ion battery.

Bismuth−Antimony Alloy Embedded in Carbon Matrix for Ultra-Stable Sodium Storage

Alloy-type anodes are the most promising candidates for sodium-ion batteries (SIBs) due to their impressive Na storage capacity and suitable voltage platform. However, the implementation of alloy-type anodes is significantly hindered by their huge volume expansion during the alloying/dealloying processes, which leads to their pulverization and detachment from current collectors for active materials and the unsatisfactory cycling performance. In this work, bimetallic Bi-Sb solid solutions in a porous carbon matrix are synthesized by a pyrolysis method as anode material for SIBs. Adjustable alloy composition, the introduction of porous carbon matrix, and nanosized bimetallic particles effectively suppress the volume change during cycling and accelerate the electrons/ions transport kinetics. The optimized Bi1Sb1@C electrode exhibits an excellent electrochemical performance with an ultralong cycle life (167.2 mAh g-1 at 1 A g-1 over 8000 cycles). In situ X-ray diffraction investigation is conducted to reveal the reversible and synchronous sodium storage pathway of the Bi1Sb1@C electrode: (Bi,Sb) Na(Bi,Sb) Na3(Bi,Sb). Furthermore, online electrochemical mass spectrometry unveils the evolution of gas products of the Bi1Sb1@C electrode during the cell operation.

Superlattice-like alternating layered Zn2SiO4/C with large interlayer spacing for high-performance sodium storage

Layered materials are among the most promising anode candidates for sodium-ion batteries, but suffer from limited interplanar spacing and poor electrical conductivity, resulting in unsatisfactory electrochemical performance. Herein, a novel layered composite of Zn2SiO4 and carbon (Zn2SiO4/C) is designed by a simple one-pot hydrothermal intercalation strategy. The Zn2SiO4/C shows unique superlattice-like lamellar configuring that the Zn2SiO4 layers and graphene-like carbon layers are alternately stacked, forming a sandwich-type structure. Such alternating layered contexture endows Zn2SiO4/C with improved conductivity and stability. In addition, the interplanar spacing of the Zn2SiO4/C achieves 1.44 nm, larger than most state-of-the-art layered materials, allowing the fast ion transfer from bulk electrolyte to the inner surface. As such, the Zn2SiO4/C delivers a high reversible Na storage capacity of 374 mAh g−1, and it presents no visible capacity decline during the cycling test. More importantly, even under a very high current density of 20 A g−1, the capacity remains 180 mAh g−1, suggesting an ultrafast energy output within 33 s (≈109 C). The ex-situ studies show that Na storage of Zn2SiO4 obeys a conversion−alloying mechanism, in which it is reduced to Zn, followed by the formation of NaxZn alloy.

One stone two birds: Pitch assisted microcrystalline regulation and defect engineering in coal-based carbon anodes for sodium-ion batteries

Coal-based carbons with abundant resources and low cost are regarded as promising anode materials for sodium‐ion batteries (SIBs). However, their ordered carbon microstructure and abundant surface defects often result in low Na-storage capacity and poor initial coulombic efficiency (ICE). Herein, we propose a simple vapor deposition strategy to synthesize coal-based carbons coated with pitch-based soft carbon layer (PCLC) for potential use as anodes for SIBs. The deposition of pitch-based volatile species allows for an efficient cross-linking reaction between hydroxyl‑containing volatile species and oxygen-rich functional groups of coal, thus generating a disordered inner-phase microcrystalline structure with dominant pseudo-graphitic phase in coal-derived carbon. Meanwhile, the exterior soft carbon coating layer substantially reduces surface defects and increases the electrical conductivity of coal-based carbon. Unlike the pristine lignite coal pyrolytic carbon which exhibited a Na-storage capacity of 290.2 mAh g−1 and ICE of 59.9%, the optimal PCLC (PCLC-1) delivered a higher reversible capacity of 312.2 mAh g−1 and a much-improved ICE of 85.3%. In addition, the PCLC-1 electrode also demonstrated excellent cycle stability with 93.4% retention after 1,000 cycles. When coupled with O3-NaNi1/3Fe1/3Mn1/3O2 cathode, PCLC-1 as an anode in a full cell configuration achieved a high energy density of 220.9 Wh kg−1 with excellent cycling and rate performance. The proposed work offers a unique insight into modulating the microcrystalline structure and surface chemistry of high-performance coal-based carbon anode materials for commercial SIBs.