Potassium Resources Research Articles

Vacancy engineering in WS2 nanosheets for enhanced potassium‐ion storage

As a promising energy storage technology, potassium-ion batteries (PIBs) have received extensive attention because of the cheap and abundant potassium resources. To date, developing anodes for fast and reversible potassiation/depotassiation is in its infancy. This study reports WS2 nanosheets modified by abundant sulfur vacancies (denoted as Sv-WS2) as anode for PIBs for the first time. Benefiting from the synergistic effects of improved electronic conductivity and more active sites produced by sulfur vacancies, and rich interspace acquired by the connection of adjacent nanosheets, the Sv-WS2 anode displays a high reversible capacity of 303.3 mAh g−1 at 0.05 A g−1 and a high rate performance of 136.6 mAh g−1 at 2.0 A g−1, as compared with that (216.5 and 45.5 mAh g−1) of pristine WS2 (P-WS2). Ex situ characterizations confirm that the Sv-WS2 anode undergoes an intercalation-conversion reaction mechanism. First principles calculations further reveal that the creation of sulfur vacancies can availably lower K-insertion energy barriers and increase the electrical conductivity. This study demonstrates a further direction to effectively enhance the potassium storage capability of transition metal dichalcogenides.

In Situ Atomic-Scale Observation of Electrochemical (De)potassiation in Te Nanowires.

Potassium-ion batteries (PIBs) have great potential in energy storage due to their high abundance and low cost of potassium resources. Tellurium (Te) is a promising PIB cathode due to its high volumetric capacity and good electronic conductivity. However, the electrochemical (de)potassiation mechanism of Te remains elusive due to the lack of an effective method of directly observing the dynamic reaction at atomic resolution. Here, the phase transformations of single crystal Te on (de)potassiation are clearly revealed by in situ high-resolution transmission electron microscopy and electron diffraction. Te undergoes a consecutive phase transformation during potassiation: from Te to K2 Te3 in the initial potassiation, and then part of the K2 Te3 to K5 Te3 on further potassiation. The reaction has extremely high reversibility in the following depotassiation. By atomic-scale observation, an anisotropic reaction mechanism where K+ intercalates into Te crystalline lattice preferentially through the (001) plane (having a large d-spacing) is established during potassiation. While in the depotassiation process, K ions extract from the polycrystalline Kx Te along the same diffusion path to form single crystal Te, indicating the potassium storage is highly reversible. The strong orientation-dependent (de)potassiation mechanism revealed by this work provides implications for the future design of nanostructured cathodes for high-performance PIBs.

Insight into a Nitrogen-Doping Mechanism in a Hard-Carbon-Microsphere Anode Material for the Long-Term Cycling of Potassium-Ion Batteries.

To investigate the alternatives to lithium-ion batteries, potassium-ion batteries have attracted considerable interest due to the cost-efficiency of potassium resources and the relatively lower standard redox potential of K+/K. Among various alternative anode materials, hard carbon has the advantages of extensive resources, low cost, and environmental protection. In the present study, we synthesize a nitrogen-doping hard-carbon-microsphere (N-SHC) material as an anode for potassium-ion batteries. N-SHC delivers a high reversible capacity of 248 mAh g−1 and a promoted rate performance (93 mAh g−1 at 2 A g−1). Additionally, the nitrogen-doping N-SHC material also exhibits superior cycling long-term stability, where the N-SHC electrode maintains a high reversible capacity at 200 mAh g−1 with a capacity retention of 81% after 600 cycles. DFT calculations assess the change in K ions’ absorption energy and diffusion barriers at different N-doping effects. Compared with an original hard-carbon material, pyridinic-N and pyrrolic-N defects introduced by N-doping display a positive effect on both K ions’ absorption and diffusion.

Sn-, Sb- and Bi-Based Anodes for Potassium Ion Battery.

Owing to the abundant resources of potassium resources, potassium ion batteries (PIBs) hold great potential in various energy storage devices. However, the poor lifespan of PIBs anodes limit their merchant applications. The exploitation of anode materials with high performance is one of the critical factors to the development of PIBs. Metallic Sn-, Sb-, and Bi-based materials, show promising future thanks to their high theoretical capacities and safe working voltage. However, the rapid capacity decay caused by the large K+ is still a pivotal challenge. In this review, recent progresses on alloying anodes were summarized. Schemes, such as ultra-small nanoparticles, hetero-element doping, and electrolyte optimization are effective strategies to improve their electrochemical properties. This review provides an outlook on the nanostructures and their synthesis methods for the alloying-type materials, and will stimulate their intensive study for practical application in the near future.

Dynamic potassium flows analysis in China for 2010–2019

China is the largest potassic fertilizer user, but with very limited potassium reserve. This study aims to present an accurate and dynamic potassium inventory from a life cycle perspective. The spatiotemporal features of the main anthropogenic potassium flows and stocks are uncovered by applying substance flow analysis (SFA). Results show that China's potassium demand had doubled and domestic extraction of potassium resources had increased by 44%, from 2.89 Mt in 2010 to 4.15 Mt in 2019, due to the increasing population and rapid agricultural development. In terms of potassium usage, regional disparity existed and the overall usage efficiency was low. A total of 63.18 megatons (Mt) potassium was discharged into local environment as wastes, and a surplus of 24.89 Mt potassium was kept in soil as stock during the study period. Scenarios analysis results show that the total potassium demand will reach 9.56 Mt, 10.34 Mt, 11.32 Mt, 9.09 Mt, and 9.80 Mt under SSP1, SSP2, SSP3, SSP4 and SSP5 scenarios, respectively. Such findings indicate that China's potassium reserve will be quickly depleted. Based upon these findings, several policy recommendations are raised, including sustainable potassium resource supply, the recycling of potassium resources, and advanced technologies to further improve potassium resource efficiency.

Dual-Ion Stabilized Layered Structure of OVO for Zero-Strain Potassium Insertion and Extraction.

Potassium‐ion batteries (KIB) have similar energy storage mechanism with lithium‐ion battery, but the potassium (K) resource is rich, which shows great potential for large‐scale energy storage system. Recently, the anode materials of KIB studied mainly include carbon materials, transition metal oxides, and alloy materials. The amorphous hard carbon shows the best comprehensive performance, but its intercalation potential is close to 0 V (versus K+/K), which is easy to cause K dendrite and brings security risks. The oxide materials have high capacity but high intercalation potential, low first cycle efficiency, and unstable cycle. Here, based on the understanding of the K intercalation mechanism of vanadium oxides, a novel zero strain anode material with layered structure of dual‐ions (Na+/K+) is designed (NaK(VO3)2—V2O5). The introduction of Na/K ion contributed to the transmission and further stabilized the structure. It has an excellent rate performance (10 A g−1, up to 25 000th cycle), and its special K storage mechanism and zero‐strain characteristics are revealed for the first time by ex situ scanning electron microscope, X‐ray powder diffraction, X‐ray photoelectron spectroscopy, and other test methods. Considering the excellent performance endowed by these unique inherent properties, NaK(VO3)2—V2O5 shows great potential for commercial anode materials and may promote the innovation of KIB.

VN nanoparticle-assembled hollow microspheres/N-doped carbon nanofibers: An anode material for superior potassium storage

Thanks to inexpensive and bountiful potassium resources, potassium ion batteries (PIBs) have come into the spotlight as viable alternatives for next-generation battery systems. However, poor electrochemical kinetics due to the large size of the K+ is a major challenge for PIB anodes. In this paper, an ingenious design of VN nanoparticle-assembled hollow microspheres within N-containing intertwined carbon nanofibers (VN-NPs/N-CNFs) via an electrospinning process is reported. Employed as PIB anodes, VN-NPs/N-CNFs exhibit a superb rate property and prolonged cyclability, surpassing that of other reported metal nitride-based anodes. This is ascribed to: (i) the VN NP-assembled hollow microspheres, which shorten the K+ diffusion distance, and mitigate volume expansion; and (ii) the interconnected N-CNFs, which supply numerous active sites for K+ adsorption and facilitate rapid electron/ion transport.

Petroleum pitch derived carbon as both cathode and anode materials for advanced potassium-ion hybrid capacitors

Potassium-ion hybrid capacitors (PIHCs) are considered as ideal devices for large-scale electrochemical energy storage because of their low reduction potential, environmental-friendly and abundant potassium resources in the earth. However, the simple and eco-friendly preparation of well-matched cathode and anode materials is still with great challenges. With the same petroleum pitch (with asphaltenes removed by n-heptane) as carbon source, herein we reported low-cost and non-corrosive processes to construct two carbon materials, namely soft carbon nanosheets (SCNs) and active carbon nanosheets (ACNs), as anode and cathode materials, respectively, to assemble high performance PIHCs. The SCNs with expanded graphitic interlayer spacing of 0.396 nm and abundant surface defects present super rate capability and high pseudocapacitive proportion. In addition, the ACNs with hierarchical pores structure, which accelerates the adsorption and transport of electrolyte ions, exhibit outstanding capacitive performance. By optimizing the voltage window and mass ratio of cathode and anode, the SCNs//ACNs PIHCs deliver a high energy density of 124.0 Wh kg−1 at a power density output of 198.9 W kg−1 and an ultralong lifespan over 9000 cycles. This work opens a new avenue to increase the value-added utilization of petroleum pitch for innovative potassium-based energy storage technology.

Heterostructured Ni3S4/Co9S8 Encapsulated in Nitrogen-Doped Carbon Nanocubes for Advanced Potassium Storage

Potassium-ion batteries (PIBs), act as an emerging renewable secondary battery technology, have drawn substantial attention because of the easily available potassium resources and excellent electrochemical properties. At present, exploiting desirable anode materials is still a challenge. Transition metal sulfides (TMSs) are considered as the advanced anode materials for PIBs due to the high theoretical specific capacity and abundant resources. But they experience large deformation during the potassiation/depotassiation process resulting in the unsatisfying long-term cyclability, which impedes their widespread applications in PIBs. Hence, we report a bimetallic sulfide heterostructure confined in nitrogen-doped carbon nanocubes (NCS@NC) as the host for PIBs, which delivers an inspiring capacity (637.5 mAh g−1 at 0.1 A g−1) and the remarkable lifespan (417.7 mAh g−1 at 2 A g−1 after 1000 cycles). We show that the nano-heterojunction can not only accelerate the K+ diffusion, but also promote charge transfer at heterointerfaces. Moreover, scanning electron microscopy after cycling reveals that the carbon shell can tolerate the volume expansion during cycling, resulting in the robust structural stability. NCS@NC anode experiences a four-stage K+-storage mechanism of combined intercalation and conversion reactions, as demonstrated by in-situ X-ray diffraction and ex-situ transmission electron microscopy techniques. This strategy of combining morphology engineering with heterostructure construction may enlighten the design of desirable anode materials towards the development of advanced PIBs.

Charge–Discharge Behavior of Graphite Negative Electrodes in FSA-Based Ionic Liquid Electrolytes: Comparative Study of Li-, Na-, K-Ion Systems

K-ion batteries utilizing ionic liquid (IL) electrolytes are promising candidates for next-generation batteries because of the abundance of potassium resources, low redox potential of potassium, and high safety of ILs. Our major interest is in the comprehensive understanding of electrochemical alkali metal intercalation/deintercalation into graphite negative electrodes, because graphite can easily form graphite intercalation compounds (GICs) with various ionic species, but not with sodium. In this study, we investigated the potassium storage mechanism of graphite negative electrodes in bis(fluorosulfonyl)amide (FSA)-based ILs, and compared the electrochemical GIC formation of Li-, Na-, and K-ion systems. Charge–discharge tests of graphite in K[FSA]–[C3C1pyrr][FSA] IL (C3C1pyrr = N-methyl-N-propylpyrrolidinium) at 313 K yielded an initial discharge capacity as high as 268 mAh (g-C)−1, leading to the formation of several K-GICs including stage-3 KC36, stage-2 KC24, and stage-1 KC8. The rate capability and long-term cycling tests indicated stable potassiation/depotassiation behavior for 225 cycles. A comparison of the electrochemical behavior of graphite among M[FSA]–[C3C1pyrr][FSA] (M = Li, Na, and K) ILs at 298 K indicated that the formation of binary M-GICs is localized in the potential range below −2.85 V vs. Fc+/Fc (Fc = ferrocene), which possibly hinders Na-GIC formation.

Homologous Strategy: Fabrication of a High-Performance Dual-Carbon Potassium Ion Hybrid Capacitor

Potassium ion hybrid capacitors (PIHC) have attracted a significant amount of interest in recent years because of their excellent overall performance and the abundance of potassium resources. The search for kinetically matched and high-performing anode and cathode materials is the key to the development of PIHCs. Hereby, we present a homologous preparation method for dual-carbon electrode materials of PIHCs with the single precursor nitrilotriacetic acid trisodium salt (NTA-3Na) by different preparation routes. The 3NaC-700 obtained by high-temperature calcination as the anode exhibits excellent kinetics performance for potassium ion storage due to its three-dimensional, large layer spacing and N-doped structure. 3NaC can be converted to a 3NaAC cathode with a high specific surface area (SSA, 3014 m2 g–1) and superior capacitance properties by further KOH activation. As a result of the advantages of the 3NaC and 3NaAC electrodes mentioned above, a high-performance dual-carbon PIHC is fabricated. It delivers a high energy and power density of 149.2 Wh kg–1 at 200 W kg–1. A high energy density of 67.2 Wh kg–1 is maintained even at a high power density of 20 kW kg–1. The PIHC device also exhibits excellent cycling stability with 81% capacity retention after 8000 cycles at a current density of 2.0 A g–1.

Dynamic Reversible Evolution of Solid Electrolyte Interface in Nonflammable Triethyl Phosphate Electrolyte Enabling Safe and Stable Potassium‐Ion Batteries

AbstractPotassium‐ion batteries (PIBs) are a favorable alternative to lithium‐ion batteries (LIBs) for the large‐scale electrochemical storage devices because of the high natural abundance of potassium resources. However, conventional PIB electrodes usually exhibit low actual capacities and poor cyclic stability due to the large radius of potassium ions (1.39 Å). In addition, the high reactivity of potassium metal raises serious safety concerns. These characteristics seriously inhibit the practical use of PIB electrodes. Here, zinc phosphide composites are rationally designed as PIB anodes for operation in a nonflammable triethyl phosphate (TEP) electrolyte to solve the above‐mentioned issues. The optimized zinc phosphide composite with 20 wt% zinc phosphate presents a high specific capacity (571.1 mA h g−1 at 0.1 A g−1) and excellent cycling performance (484.9 mA h g−1 with the capacity retention of 94.5% after 1000 cycles at 0.5 A g−1) in the KFSI‐TEP electrolyte. XPS depth profile analysis shows that the improved cycling stability of the composite is closely related to the reversible dynamic evolutions and conversions of the sulfur‐containing species in the solid electrolyte interphase (SEI) during the charge/discharge process. This dynamic reversible SEI concept may provide a new strategy for the design of superior electrodes for PIBs.

Controllable construction of hierarchically porous carbon composite of nanosheet network for advanced dual-carbon potassium-ion capacitors

Benefitting from the abundance and inexpensive nature of potassium resources, potassium-ion energy storage technology is considered a potential alternative to current lithium-ion systems. Potassium-ion capacitors (PICs) as a burgeoning K-ion electrochemical energy storage device, are capable of delivering high energy at high power without sacrificing lifespan. However, owing to the sluggish kinetics and significant volume change induced by the large K+-diameter, matched electrode materials with good ion accessibility and fast K+ intercalation/deintercalation capability are urgently desired. In this work, pine needles and graphene oxide (GO) are utilized as precursors to fabricate oxygen-doped activated carbon/graphene (OAC/G) porous nanosheet composites. The introduction of GO not only induces the generation of interconnected nanosheet network, but also increases the oxygen-doping content of the composite, thus expanding the graphite interlayer spacing. Experimental analysis combined with first-principle calculations reveal the transport/storage mechanism of K+ in the OAC/G composite anode, demonstrating that the high surface area, sufficient reactive sites, enlarged interlayer distance and open channels in the porous nanosheet network contribute to rapid and effective K+ diffusion and storage. When incorporated with pine needle-activated carbon as cathode, the assembled dual-carbon PICs can function at a high voltage of 5 V, exhibiting a high energy density of 156.7 Wh kg−1 at a power density of 500 W kg−1 along with a satisfied cycle life, which highlights their potential application in economic and advanced PICs.

Strategies for Harnessing High Rate and Cycle Performance from Graphite Electrodes in Potassium-Ion Batteries.

Potassium-ion batteries (PIBs) have been lauded as the next-generation energy storage systems on account of their high voltage capabilities and low costs and the high abundance of potassium resources. However, the practical utility of PIBs has been heavily encumbered by severe K metal dendrite formation, safety issues, and insufficient electrochemical performance during operations─indeed critical issues that underpin the need for functional electrolytes with high thermal stability, robust solid-electrolyte interphase (SEI)-forming capabilities, and high electrochemical performance. In a bid to establish a knowledge framework for harnessing high rate capabilities and long cycle life from graphite negative electrodes, this study presents the physical properties and electrochemical behavior of a high K+ concentration inorganic ionic liquid (IL) electrolyte, K[FSA]-Cs[FSA] (FSA- = bis(fluorosulfonyl)amide) (54:46 in mol), at an intermediate temperature of 70 °C. This IL electrolyte demonstrates an ionic conductivity of 2.54 mS cm-1 and a wide electrochemical window of 5.82 V. Charge-discharge tests performed on a graphite negative electrode manifest a high discharge capacity of 278 mAh g-1 (0.5 C) at 70 °C, a high rate capability (106 mAh g-1 at 100 C), and a long cyclability (98.7% after 450 cycles). Stable interfacial properties observed by electrochemical impedance spectroscopy during cycling are attributed to the formation of sulfide-rich all-inorganic SEI, which was examined through X-ray photoelectron spectroscopy. The performance of the IL is collated with that of an N-methyl-N-propylpyrrolidinium-based organic IL to provide insight into the synergism between the highly concentrated K+ electrolyte at intermediate temperatures and the all-inorganic SEI during electrochemical operations of the graphite negative electrode.

Soft carbon-coated bulk graphite for improved potassium ion storage

Potassium-ion batteries (PIBs) have attracted tremendous attention for large-scale energy storage fields based on abundant potassium resources. Graphite is a promising anode material for PIBs due to its low potassium ion intercalation voltage and mature industrialized preparation technology. However, the inability of graphitic structures to endure large volume change during charge/discharge cycles is a major limitation in their advancement for practical PIBs. Herein, a soft carbon-coated bulk graphite composite is synthesized using PTCDA as a carbon precursor. The PTCDA-derived soft carbon coating layer with large interlayer distance facilities fast potassium ion intercalation/extraction in the BG@C composite and buffers severe volume change during the charge/discharge cycles. When tested as anode for PIBs, the composite realizes enhanced rate capability (131.3 mAh/g at 2 C, 1 C = 279 mA/g) and cycling performance (capacity retention of 76.1% after 150 cycles at 0.5 C). In general, the surface modification route to engineer graphite anode could inherently improve the electrochemical performance without any structural alteration.

Hollow MoS2 Spheres Confined in Carbon Fibers for Ultralong-life Potassium Storage

Potassium-ion energy storage systems are gradually showing their status due to abundant potassium resources and low cost. Unfortunately, K+ storage materials are still an exigent issue due to the large radius and sluggish kinetics of K+. Herein, a composite electrode (H-MoS2@CNFs) built by electrospun carbon fibers (CNFs) as the frame and the hollow MoS2 spherical shell as the inner core is designed. H-MoS2@CNFs is endowed with the following preponderance: the outside CNFs interlocked with the MoS2 nanosheets play a triple role in conducting electrons, buffering the volume expansion of MoS2, and maintaining the structural stability of the electrode; the exposed edges of the (002) plane of MoS2 nanosheets in direct contact with the electrolyte stored in the internal cavity facilitate the K+ reaction kinetics. As the anode of potassium-ion batteries, H-MoS2@CNFs delivers an excellent cyclic performance (187.7 mAh g–1 at 2.0 A g–1 after 5000 cycles with 0.0037% decay per cycle) and high rate capability (184.7 mAh g–1 at 10.0 A g–1). Furthermore, owing to the superior potassium storage and freestanding characteristics without the binder and conductive additives, the potassium-ion capacitor (PIC) based on the anode exhibits a high energy density of 165 Wh kg–1 at a power density of 378 W kg–1, which furnishes a reliable basis for the development of two-dimensional materials for the PIC.

Electrolyte formulation strategies for potassium-based batteries.

Potassium (K)-based batteries are viewed as the most promising alternatives to lithium-based batteries, owing to their abundant potassium resource, lower redox potentials (-2.97V vs. SHE), and low cost. Recently, significant achievements on electrode materials have boosted the development of potassium-based batteries. However, the poor interfacial compatibility between electrode and electrolyte hinders their practical. Hence, rational design of electrolyte/electrode interface by electrolytes is the key to develop K-based batteries. In this review, the principles for formulating organic electrolytes are comprehensively summarized. Then, recent progress of various liquid organic and solid-state K+ electrolytes for potassium-ion batteries and beyond are discussed. Finally, we offer the current challenges that need to be addressed for advanced K-based batteries.

Engineering of Crosslinked Network and Functional Interlayer to Boost Cathode Performance of Tannin for Potassium Metal Batteries

AbstractPotassium metal batteries (PMBs) are a compelling technology for large‐scale energy storage due to the abundance of potassium resources and high energy density. A vital obstacle to construct high‐performance PMBs is developing superior cathode materials. Tannin, a plant polyphenol, holding many active sites for redox reactions, is an auspicious high‐capacity cathode. However, the relatively poor conductivity and slight solubility in electrolyte deteriorate its capacity and cycle stability. Herein, the tannin is activated through a crosslinking reaction with polyaniline to obtain a composite cathode (i.e., ATN). It exhibits a high initial capacity of 172 mAh g−1 at 50 mA g−1, based on the electrochemical reaction mechanisms of embedding/releasing of K+ on CO and PF6− on NH. Moreover, to improve the cycling performance, a graphene oxide modified separator is developed to effectively retard the ATN shuttle. As a result, the capacity retention is significantly enhanced, for example, 82% over 300 cycles at 50 mA g−1. From a practical aspect, a full PMB of K@KxPy||ATN is built up, displaying high energy/power density and superior cycling stability, which is a step forward in the development of PMBs.

WO3-x@W2N heterogeneous nanorods cross-linked in carbon nanosheets for electrochemical potassium storage

Potassium-ion batteries (PIBs) are highly desirable as large-scale sustainable battery systems due to the high working potential and low-cost potassium resources. However, the large radius of potassium ion inevitably causes huge volume expansions and rapid capacity decay of electrodes, so the development of long-life anodes still remains at its infancy. Herein, the nonstoichiometric heterostructures with bimetallic characteristics (WO3-x@W2N) are rationally constructed on mono-faceted nanorods and in-situ cross-linked in nitrogen-doped carbon nanosheets (WO3-x@W2N/CNSs). The mono-faceted WO3-x nanorods endow oxygen vacancies with abundant unsaturated active sites and dangling bonds in their directional charge-transfer paths. The heterostructures with rich self-built electric fields can regulate electronic structures of oxygen-vacancy/metallic WO3-x and metallic W2N, and notably enhance the efficiency of charge transfer and storage under the protection of highly conductive CNSs. Utilizing the vacancy, phase and interface engineering, the WO3-x@W2N/CNSs deliver a large reversible capacity (366.6 mAh g−1 at 0.1 A g−1), with high-rate capacity and ultralong lifespan (113.2 mAh g−1 after 12,000 cycles at 10.0 A g−1). These findings, storage mechanisms and kinetics behaviors are elucidated in detail via the advanced techniques and first-principles calculations, demonstrating that the nonstoichiometric and metallic heterostructures have promising potentials in high-performance metal ion batteries.

Rational design of hierarchical Ni-Mo bimetallic Selenide/N-doped carbon microspheres toward high–performance potassium ion batteries

Potassium ion batteries (KIBs) have received a lot of attention in large-scale energy storage applications because of abundant potassium resources. However, owing to the poor structural durability of electrode materials and sluggish reaction kinetics, the commercialization of KIBs is challenging. Herein, we design a hierarchically structured Ni–Mo bimetallic selenide/N-doped carbon microsphere (NMSe/NC) as an advanced anode material for KIBs. The hierarchical Ni-Mo/polydopamine microsphere precursor, obtained from the spontaneous chemical reaction of NiMoO4 nanorods with dopamine hydrochloride, is converted into heterostructured-Ni–Mo selenide crystals confined in a hierarchical NC matrix via a two-step thermal treatment. The unique hierarchical surface structure and the synergistic effect of Mo and Ni species provide sufficient electrochemical reaction sites and promote the reaction kinetics. Furthermore, the proximate contact between the active materials and the N-doped carbon matrix can facilitate electron transportation and enhance the structural robustness of the electrode. Consequently, the resulting NMSe/NC hierarchical microspheres delivered a high reversible capacity of 332 mA h g−1 after 200 cycles (current density: 0.5 A g−1) and a remarkable rate capability of 206 mA h g−1 (current density: 2.0 A g−1). The excellent electrochemical performance of NMSe/NC indicates their potential for KIB commercialization in large-scale energy storage systems in the future.