Advanced hard carbon materials for practical applications of sodium-ion batteries developed by combined experimental, computational, and data analysis approaches

Zhu Z., Men Y., Zhang W., Yang W., Wang F., Zhang Y., Zhang Y., Zeng X., Xiao J., Tang C., Li X., Zhang Y.

Cheng Y., Wang Y., Chen B., Han X., He F., He C., Hu W., Zhou G., Zhao N.

AbstractAprotic alkali metal–CO2 batteries (AAMCBs) have garnered significant interest owing to fixing CO2 and providing large energy storage capacity. The practical implementation of AAMCBs is constrained by the sluggish kinetics of the CO2 reduction reaction (CO2RR) and the CO2 evolution reaction (CO2ER). Because the CO2ER and CO2RR take place on the cathode, which connects the internal catalyst with the external environment. Building a bidirectional cathode with excellent CO2ER and CO2RR kinetics by optimizing the cathode's internal catalyst and environment has attracted most of the attention to improving the electrochemical performance of AAMCBs. However, there remains a lack of comprehensive understanding. This review aims to give a route to bidirectional cathodes for reversible AAMCBs, by systematically discussing engineering strategies of both the internal catalyst (atomic, nanoscopic, and macroscopic levels) and the external environment (photo, photo‐thermal, and force field). The CO2ER and CO2RR mechanisms and the “engineering strategies from internal catalyst to the external environment–cathode properties–CO2RR and CO2ER kinetics and mechanisms–batteries performance” relationship are elucidated by combining computational and experimental approaches. This review establishes a fundamental understanding for designing bidirectional cathodes and gives a route for developing reversible AAMCBs and similar metal–gas battery systems.

Wang Y., Cheng Y., Chen B., Zhou J., Xie H., Fan Y., Sha J., Liu E., He F., He C., Hu W., Zhao N.

Wu C., Yang Y., Zhang Y., Xu H., Huang W., He X., Chen Q., Dong H., Li L., Wu X., Chou S.

AbstractGiven the merits of abundant resource, low cost and high electrochemical activity, hard carbons have been regarded as one of the most commercializable anode material for sodium‐ion batteries (SIBs). However, poor rate capability is one of the main obstacles that severely hinder its further development. In addition, the relationships between preparation method, material structure and electrochemical performance have not been clearly elaborated. Herein, a simple but effective strategy is proposed to accurately construct the multiple structural features in hard carbon via adjusting the components of precursors. Through detailed physical characterization of the hard carbons derived from different regulation steps, and further combined with in‐situ Raman and galvanostatic intermittent titration technique (GITT) analysis, the network of multiple relationships between preparation method, microstructure, sodium storage behavior and electrochemical performance have been successfully established. Simultaneously, exceptional rate capability about 108.8 mAh g−1 at 8 A g−1 have been achieved from RHC sample with high reversible capacity and desirable initial Coulombic efficiency (ICE). Additionally, the practical applications can be extended to cylindrical battery with excellent cycle behaviors. Such facile approach can provide guidance for large‐scale production of high‐performance hard carbons and provides the possibility of building practical SIBs with high energy density and durability.

Jiang C., Chen B., Xu M., Jiang J.

The single ionic doping helps suppress the detrimental phase transition when P2-type layered cathodes are charged to a high voltage above 4.0 V (vs. Na+/Na). However, this is realized at the sacrifice of their electrochemical redox centers and output capacities. To achieve both high voltage tolerance and capacity, we herein propose a cooperative Al cation and F anion co-doping strategy. The XANES detections affirm that substituting Ni/O with Al/F intends to augment the amount of highly active Mn3+ cations in cathodes, making more contributions on specific capacities for sodium-ion batteries (SIBs). Besides, this co-doping treatment would disorder the transition metal ionic arrangements of cathodes, disrupting long-range Jahn-Teller effects and impeding other undesired phases generation. As a proof-of-concept demonstration, our designed Na2/3Ni0.23Al0.1Mn2/3O1.95F0.05 (NAF) cathodes show a delivered capacity as high as 142.0 mAh g−1 (0.2C), and an impressive capacity retention of 86.7 % after all cycling. The in-situ XRD detections reveal no apparent O2 phase peaks emerge until 4.23 V upon deep Na+ extraction from NAF. This work provides a key understanding toward cation/anion co-doping effects, opening up a useful avenue for rational design of practical P2-type cathodes for SIBs.

Song Z., Di M., Zhang X., Wang Z., Chen S., Zhang Q., Bai Y.

AbstractDeveloping non‐graphitic carbons with unique microstructure is a popular strategy to enhance the significant potential in practical applications of sodium‐ion batteries (SIB), while the electrochemical performance imbalances arising from their intricate active surface and porous structure pose significant challenges to its commercialization. Inspired by the structure of biological cell membranes, N/P co‐doped hard carbon nanospheres (NPCS) anodes with abundant ultramicropores (≈0.6 nm) are proposed and synthesized as robust sodium anodes. Based on density functional theory calculations, optimizing ultramicropores can enable small Na+ to be well confined within the pores and hinder large solvent molecules from invading and reacting, introducing N/P species contributes to the rapid adsorption/diffusion of Na+. In situ XRD and Raman analysis suggest that the nanoconfinement strategy induced by abundant ultramicropores and N/P co‐doping enables highly reversible electrochemical reactions. Electrochemical test confirms that the nanoconfinement strategy endows the NPCS anode with high reversible capacity (376.3 mAh g−1 at 0.1 A g−1), superior initial coulombic efficiency (87.3% at 1.0 A g−1), remarkable rate capability (155.6 mAh g−1 at 50.0 A g−1) and excellent cycling stability (with capacity retention of ≈94.6% after 10 000 cycles), lightening a promising avenue for developing SIB with robust durability.

Patel A., Mishra R., Tiwari R.K., Tiwari A., Samriddhi, Singh S.P., Yadav V., Singh R.K.

Zhang X., Yi Z., Tian Y., Xie L., Su F., Wei X., Chen J., Chen C.

Pitch is an excellent precursor of hard carbons (HCs) with low-cost and high carbon content, enabling its commercial-scale application in sodium-ion batteries. Pre-oxidation is the key to obtaining pitch-derived HCs with disordered microstructures. However, pitch is a mixture of fractions with different molecular weights and structures. With the introduction of oxygen, the cross-linked structure established by each fraction could be different, the effect of which on the microstructure and sodium storage performance of HCs remains unclear. Here, we separate pitch into three fractions and further pre-oxidize and carbonize to produce HCs, in order to systematically investigate the effects of structural differences among pitch fractions on the cross-linking mechanism and microstructure of as-obtained HCs. It is found that tetrahydrofuran-insoluble (THFI) enables the enrichment of polar oxygen functional groups, thus enhancing its oxidative activity to obtain more oxygen for the construction of abundant three-dimensional cross-linked structure. It is conducive to preventing the rearrangement of carbon layers and promoting the development of micropores during high-temperature carbonization process, which facilitates the storage of sodium ions in the low-voltage plateau region. The resulting hard carbon (THFI-1400) has significantly improved overall sodium storage performances. This work provides a new strategy to prepare low-cost and high-performance HCs.

Idamayanti D., Rochliadi A., Iqbal M., Noer Z., Febrian R., Septiani N.L., Purwasasmita B.S., Yuliarto B., Nuruddin A.

Hard carbon (HC) is recognized as a promising anode material for sodium-ion batteries due to its high capacity and low operating voltage. However, the usage of polyvinylidene fluoride (PVDF) binder leads to a shortened HC cycle life because of the high reactivity of PVDF toward the carbonate ester-based electrolyte. Herein, we have reported the synthesis of a cellulose nanocrystal (CNC) reinforced chitosan (Ch)-derived free-standing HC anode, which features hydroxyl surface chemistry on HC and flexible framework. The CNC-Ch not only serves as a binder and a substrate but also increases the Na-ions adsorption and diffusion. The CNC content induced the pseudocapacitive behavior and enhanced the cycle stability of the HC anode. The CNC of 6 % exhibits an initial discharge capacity of 285 mAh g−1, an initial Coulombic efficiency (ICE) of 82 %, and a reversible capacity of 244 mAh g−1 at a current density of 25 mA g−1 for 5 cycles. For 100-cycle charge-discharge, it showed excellent cycle stability, retaining 67 % of its capacity in the first 50 cycles at 25 mA g−1 and 82 % in the subsequent 50 cycles at 50 mA g−1. This finding suggests that the free-standing HC anode in CNC-Ch presents a new opportunity for the development of a low-cost, stable, flexible, and environmentally sustainable anode for SIB application.

He B., Feng L., Hong G., Yang L., Zhao Q., Yang X., Yin S., Meng Y., Xiao D., Wang Y., Ai J.

Sharma S., Manchala V., Gopalan R., Rao T.N., Das B.

Hard carbon (HC) is identified as a potential anode for sodium ion batteries (SIBs) due to its outstanding electrochemical performance. However, selection of synthesis routes and its precursors remain crucial to develop the HC of desired microstructures for enhanced sodium-ion storage. Herein, we employed novel flame pyrolysis route to prepare spherical HC nanoparticles (

Li E., Tang X., Zhou J., Zhao H., Teng J., Huang J., Dai B., Lu T., Tao Q., Zhang K., Deng W., Li J.

Sodium-ion batteries are a promising energy storage system due to their rich sodium resources and many other advantages. However, its development is severely hampered by the electrolyte's low compatibility with the electrode contact. Herein, we propose a solvation control strategy with ethoxy (pentafluoro) cyclotriphosphazene (PFPN) and NaClO4 double additives to reconstruct the solvation structure of sodium ions in electrolytes. This enables the electrolyte to form a dense and stable solid electrolyte interlayer (SEI) and double-layer cathode electrolyte interphase (CEI) on the surface of the electrode material to achieve long-cycle and high-capacity sodium-ion batteries. PFPN can form a stable SEI rich in inorganic components at the anode interface. ClO4- can first reach the cathode surface to create a NaCl and polymer-like chain CEI with sodium ions and solvents, and then the PFPN derivatives are migrated to the cathode surface to open the ring and decompose, thus forming a double-layer stable CEI. Therefore, the PEDN electrolyte can simultaneously improve the interface stability of the battery's cathode and anode solid electrolyte. Hence, the capacity retention rate of the 4.5 Ah Na3Fe2(PO4)P2O7 (NFP)||hard carbon (HC) pouch cell after 2500 cycles at 1C is 88.26%.

Guo W., Chen Z., Sun Z., Geng C., Jiang J., Ju Z., Feng P.

Carbon-based materials are regarded as promising anode materials for potassium-ion batteries. However, owing to the limited storage sites and worse diffusion kinetics of K+, leading to inferior potassium ion storage ability. Herein, a creative strategy for molecule-microstructure modification focusing on oxygen vacancy-rich, high-internal spacial scale is proposed, which has employed to prepare porous amorphous SiOx@C composite anode for enhanced potassium-ion storage. In particular, SiOx functions as the inner porous skeleton of composites and contributes to storage activity. The oxygen vacancy with C-Si-(O) accelerates the electron and ion transfer and generates the active sites with enhanced concentration, and the carbon defect enlarges the interlayer spacing, resulting in rapid dynamics and greater storage capacity. As expected, the optimized SiOx@C anode delivers a superior rate performance of 265 mAh g−1 at 2 A g−1. As a practical device application, the assembled potassium-ion hybrid capacitors (SiOx@C//AC) deliver a maximum energy density of 100 Wh kg−1 and a satisfactory cycle stability (5000 cycles). This work sheds light on carbonaceous anode based on oxygen vacancy composite as a promising support to design efficient potassium storage systems.

Li P., Chen P., Zhang W., Kang K., Duan J., Wang H., Yuan Q., Wang J., Liu Y.

Pitch is a commonly used industrial by-product precursor in the production of anode materials for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). However, achieving efficient utilization of waste pitch poses a challenge for recycled materials. To address this issue, we used simple multielement modification and obtain the pitch-based carbon doped with oxygen (O), nitrogen (N), and sulfur (S). Our work reveals that pitch with high softening point tends to form the crosslinked structure during pre-oxidation. Moreover, in proximity to the defects induced by oxygen functionalities, the introduction of nitrogen and sulfur can jointly impact on the diffusion kinetics of lithium/sodium, and it is demonstrated by enhancing lithium adsorption and sodium desorption from the defects. In comparison to the conventional one-step carbonization approach, the modified anodes significantly improve the rate performance of the LIBs (61.11 mAh g−1 to 222.90 mAh g−1 at 5 A g−1) and the initial Coulombic efficiency (ICE) of SIBs (41.74%–66.40%). Our study explores the link between softening points and oxygen functionalities, as well as the effect of introducing various heteroatoms on the properties and diffusion kinetics of LIBs and SIBs, providing a reference for other materials to obtain anodes with high compatibility.

Wang B., Yao Y., Wang W., Xu Y., Wan Y., Sun Y., Li Q., Hu H., Wu M.

Hard carbon (HC) has emerged as a highly promising anode material for sodium ion batteries, drawing tremendous interest in producing this material with low-cost and easily accessible precursors. The determination of the crucial parameters of precursors influencing the formation of key structures, such as closed pores, in the HC is of paramount importance. Considering the potential role of free radicals in the structural evolution of the precursors, we, for the first time, delve into the impact of radical species on the development of closed pores by electron paramagnetic resonance spectroscopy, with petroleum asphalt as the model system. Our findings reveal that carbon centred radicals, with the g value close to that of the free electron (2.0023), exhibit a propensity to form long-range, well-ordered graphitic structures with lower sodium storage capacity. Conversely, the deliberately incorporated oxygen radicals with the g value over 2.005 require a higher energy for ordering the graphitic structures, leading to the creation of closed pores. As a result, the optimal sample showcases a four-fold increase in plateau capacity for sodium ion storage due to the pore filling process. Our research underscores the pivotal role of employing electron paramagnetic resonance spectroscopy studying the critical structural evolution of functional carbon materials.

Wang A., Zhang G., Li M., Sun Y., Tang Y., Sun K., Lee J., Fu G., Jiang J.

Sun C., Du W., Sun Q.

Jing Z., Mamoor M., Kong L., Wang L., Wang B., Chen M., Wang F., Qu G., Kong Y., Wang D., He X., Wang C., Zhang X., Zhang Y., Wang G., et. al.

AbstractUnderstanding the relationship between structure regulation and electrochemical performance is key to developing efficient and sustainable sodium‐ion batteries (SIBs) materials. Herein, seven Cobalt‐M‐based (M=V, Mn, Fe, Co, Ni, Cu, Zn) Prussian blue analogues (CoM‐PBAs) are designed as anodes for SIBs via a universal low‐energy co‐precipitation approach with the strategic inclusion of 3d transition metals. Density Functional Theory (DFT) simulation and experimental validation reveal that a moderate p‐band center of cyanide linkages (−CN−) is more favorable for Na+ intercalation and diffusion, while the d‐band center of metal cations is linearly related to electrode stability. Among seven CoM‐based PBAs, CoV‐PBAs possess the best sodium‐ion adsorption/diffusion kinetics and overall cycling performance, including high specific capacity (565 mAh/g at 0.1 A/g), cycling stability (over 15000 cycles with 97.7 % capacity retention), and superior rate capability (174.7 mAh/g at 30 A/g). In situ/ex situ techniques further demonstrate that the π‐electron regulation by V introduction enhances the reversibility and kinetics of redox reactions. Moreover, the study identified the “p‐band center” and “d‐band center” may serve as key descriptors for quantifying the capability and stability of other‐type bimetal Co‐based anodes (oxides, phosphides, sulfides, and selenides) with similar theoretical capacity, offering a potentially transformative approach for selecting practical SIB electrode materials.

Jing Z., Mamoor M., Kong L., Wang L., Wang B., Chen M., Wang F., Qu G., Kong Y., Wang D., He X., Wang C., Zhang X., Zhang Y., Wang G., et. al.

AbstractUnderstanding the relationship between structure regulation and electrochemical performance is key to developing efficient and sustainable sodium‐ion batteries (SIBs) materials. Herein, seven Cobalt‐M‐based (M=V, Mn, Fe, Co, Ni, Cu, Zn) Prussian blue analogues (CoM‐PBAs) are designed as anodes for SIBs via a universal low‐energy co‐precipitation approach with the strategic inclusion of 3d transition metals. Density Functional Theory (DFT) simulation and experimental validation reveal that a moderate p‐band center of cyanide linkages (−CN−) is more favorable for Na+ intercalation and diffusion, while the d‐band center of metal cations is linearly related to electrode stability. Among seven CoM‐based PBAs, CoV‐PBAs possess the best sodium‐ion adsorption/diffusion kinetics and overall cycling performance, including high specific capacity (565 mAh/g at 0.1 A/g), cycling stability (over 15000 cycles with 97.7 % capacity retention), and superior rate capability (174.7 mAh/g at 30 A/g). In situ/ex situ techniques further demonstrate that the π‐electron regulation by V introduction enhances the reversibility and kinetics of redox reactions. Moreover, the study identified the “p‐band center” and “d‐band center” may serve as key descriptors for quantifying the capability and stability of other‐type bimetal Co‐based anodes (oxides, phosphides, sulfides, and selenides) with similar theoretical capacity, offering a potentially transformative approach for selecting practical SIB electrode materials.

Meng X., Xiao N., Gao C., Zhang R., Sun Z., Cheng Y., Zhang N., Li W., Chen B., He C.

AbstractLithium metal anode (LMA) is expected to be the ideal anode material for future high‐energy‐density batteries, but regulating the complex electrolyte–anode interface remains a challenge. In this work, a stable Li2Te coating is formed on the surface of commercial copper mesh (LTCM) using a simple and quick method to improve lithium metal anode interfacial kinetics. Li2Te possesses a strong affinity for both Li+ and TFSI− anions, which reduces the lithium nucleation barrier and guides the formation of inorganic‐rich SEI, accelerates the diffusion of Li+, and promotes the growth of lithium metal along the plane. The highly conductive Li2Te and Cu generated by in situ lithiation reaction together constitute an effective electron‐conducting network, which synergistically enhances the interfacial kinetics and the cycling stability of LMA. As a result, the LTCM maintains high Coulombic efficiency (98%) even after 2200 cycles at 1 mA cm−2, whereas the symmetric cell has a long cycle life of over 5400 h at 1 mA cm−2. In addition, the full cells with LFP display a high capacity retention ratio (80%) after 480 cycles at 1 C and the corresponding pouch cell can cycle steadily more than 464 cycles at 1 C, which has good application prospects.