Anode Material For Potassium-ion Batteries Research Articles

BeN4 monolayer as an excellent Dirac anode material for potassium-ion batteries

Rapid development of anode materials with good stability, high capacity, low diffusion barrier and excellent cyclability is an important challenge for the further enhancement of the battery industry today. Recently, a novel stable two-dimensional (2-D) material named beryllonitrene (BeN4) has been experimentally synthesized. Considering its lightweight and porous structure, we systematically investigate the feasibility of BeN4 monolayer as an anode material for metal ion batteries (MIBs) based on first-principles calculations. We investigate the adsorption behavior of Li/Na/K on BeN4 monolayer surfaces, and find that BeN4 monolayer with Dirac cone can only stably adsorb potassium and possess good electrical conductivity before and after adsorption of potassium. More noteworthy is that BeN4 monolayer has fairly low diffusion barrier (62 meV) and open circuit voltage (0.084–0.179 V), as well as very high storage capacity (842 mA h g−1), which are superior to most 2-D anode materials for potassium-ion batteries (PIBs). Moreover, BeN4 monolayer is also demonstrated to have great cycle stability and long-term cycle life. Therefore, our results suggest that BeN4 monolayer is expected to become a pretty perfect Dirac anode material for PIBs.

Encapsulation of KTi2(PO4)3 nanoparticles in porous N-doped carbon nanofibers as a free-standing electrode for superior Na/K-storage performance

Herein, a self-supporting electrospinning film of porous N-doped carbon nanofibers impregnated with KTi2(PO4)3 nanoparticles (abbreviated as NF-KTP) is constructed. The free-standing NF-KTP exhibits excellent flexibility and is directly adopted as a binder-free anode for sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs). The introduction of conductive N-doped carbon matrix enables enhanced intrinsic electronic conductivity and fast ion diffusion kinetics, as well as the fabrication of porous nitrogen-doped interconnected carbon fibers impregnated with KTi2(PO4)3 nanoparticles can offer a short transport path of sodium/potassium ions and buffer the volume expansion during repetitive intercalation/deintercalation. Therefore, the NF-KTP electrode delivers an initial charge capacity of 116.8 mAh g−1 at 0.2 C, superb rate capability of 107.8 mAh g−1 at 50 C and impressive cycling stability with a capacity retention of 92.8 % for 1000 cycles at 5 C in SIBs. Even at 0 °C and 50 °C, it still retains marvelous rate performance with capacities of 99.8 and 106.3 mAh g−1 at 50 C, respectively. Meanwhile, as an anode material for PIBs, NF-KTP also displays good electrochemical performances, as reflected by its exceptional rate performance (99.3 mA h g−1 at 10 C) and superb cycling performance (with no capacity fading after 300 cycles at 5 C). These satisfactory electrochemical properties can be ascribed to the superiority of the stable 3D network formed by KTP nanofibers. Such a simple and effective strategy may provide a new vision for other materials applied in energy storage systems.

Synergistic strategy of the phosphorus anode decorated by LiF and combined with KFSI-based electrolyte against shuttle effect of dissoluble polyphosphides for boosting potassium-storage performance

Phosphorus is a promising anode material for potassium-ion batteries due to the highest theoretical-specific capacity among all the proposed anode materials. So far, it is considered to have similar disadvantages to silicon anode, such as poor electronic conductivity and huge volumetric change, thus, lots of efforts have been devoted to synthesizing phosphorus/carbon hybrids. However, the electrochemical performance is still unsatisfied, due to the unclear capacity decay mechanism. Here we reveal that soluble potassium polyphosphides are generated during potassiation process and shuttle to the counter electrode where the side effects occur, leading to the loss of active phosphorus and the failure of counter electrode. To address this issue, we developed the P/CNT-LiF electrode in combination with the replacement of conventional KPF 6 by potassium bis(fluorosulfonyl)imide (KFSI) in electrolyte, in which KFSI contributes to the formation of stable and tough solid electrolyte interface (SEI), meanwhile LiF can prevent polyphosphides from diffusing to the electrolyte before and after the formation of SEI. Thus, the thin, stable and uniform SEI layer can be generated at the surface of the electrode particles, inhibiting the polyphosphides’ shuttle, contributing to the improved initial coulomb efficiency (73.7%) and reversible specific capacity (507.6 mAh g −1 after 100 cycles at 50 mA g −1 ).

Nitrogen and Fluorine Codoped Graphite Derived from Microcrystalline Graphite ore as a High-performance Anode Material for Potassium-Ion Batteries

Nitrogen and Fluorine Codoped Graphite Derived from Microcrystalline Graphite ore as a High-performance Anode Material for Potassium-Ion Batteries

Air-stabilized pore structure engineering of antimony-based anode by electrospinning for potassium ion batteries

Due to the large ionic radius and associated slow reaction kinetics of potassium ions, it is a major challenge to find suitable anode materials for potassium-ion batteries. Herein, we design porous antimony-based nanofibres via a simple, low-cost and large scalable method to promote the electrochemical performance of potassium-ion batteries. Unlike those traditionally treated in inert atmospheres, using the different decomposition processes of polyacrylonitrile and polyvinylpyrrolidone in air, we obtain antimony trioxide embedded in porous carbon nanofibres (Sb2O3@PCN). The porous structure can promote the permeation of electrolyte into electrode materials and increase the active sites of the redox reaction. The porous carbonaceous fibre skeleton structure establishes a fast ion transport channel and enhances the kinetic performance. In a concentrated 5 M potassium bis(fluorosulfonyl)-imide/dimethyl carbonate electrolyte, Sb2O3@PCN exhibits a stable discharge specific capacity of 437.3 mAh g-1 at a current density of 100 mA g−1 after 50 cycles, which is much higher than that treated in a N2 atmosphere (247.5 mAh g-1). This method provides a new approach for the preparation of efficient potassium-ion battery electrode materials.

In situ construction of hollow Ni3S2-Co9S8 heterostructures with enhanced reaction kinetics for potassium ion storage

Owing to high theoretical capacity, nickel sulfide and cobalt sulfide were highly competitive anode materials for potassium ion batteries (PIBs). However, the slow reaction kinetics and poor structural stability during the cycle hinder its application in the anode materials of PIBs. An exquisite heterogeneous structure of bimetal sulfide Ni3S2-Co9S8 nanotube wrapped with a nitrogen-doped carbon layer is prepared by in situ growth and solvothermal strategies. Such a well-designed structural provides a channel for the rapid diffusion of potassium ions, promotes charge transfer at the heterojunction interface and effectively improves the reaction kinetics. When used as the anode for PIBs, the Ni3S2-Co9S8@NSC exhibits an excellent capacity of 419 mA h g−1 after 200 cycles at 0.1 A g−1 and an excellent rate performance of 220 mA h g−1 at 5 A g−1. And after 200 cycles at 1 A g−1 and 2 A g−1, there are 285 mA h g−1 and 238 mA h g−1 high reversible capacities, respectively. Moreover, potassium ion hybrid capacitor can provide good energy density (148 Wh kg−1), power density (6639.3 W kg−1) and excellent cycle reversibility. Based on experiments and DFT calculations, the heterojunction structure in the composite can not only optimize the electronic structure and distribution to improve the conductivity, but also improve the potassium ion adsorption energy to accelerate the reaction kinetics. The excellent electrochemical properties reveal the advantages of reasonably designing carbon coated hollow heterostructures for energy storage.

Carbon-Coated Flower-Like TiO2 Nanosphere as an Ultrastable Anode Material for Potassium-Ion Batteries: Structure Design and Mechanism Study

Carbon-Coated Flower-Like TiO₂ Nanosphere as an Ultrastable Anode Material for Potassium-Ion Batteries: Structure Design and Mechanism Study

A mushroom derived biomass carbon as high-stability anode for potassium ion battery

As an alternative to Li-ion batteries, potassium-ion batteries have attracted increasing research interest due to the natural abundance of potassium and low cost. However, the larger ionic radius of the potassium easily causes a large volume expansion of the anode materials, eventually hindering the practical application of potassium-ion batteries. Here, we reported a heteroatomic doping mushroom biomass carbon (HDMC) as anode material for potassium-ion batteries. With high surface area and rich heteroatomic doping (N, S, and P), the as-prepared porous HDMC not only provides sufficient void space to relieve volume expansion of electrode but also offers highly efficient channels for fast transport of both electrons and potassium ions. The results demonstrated that the HDMC showed relatively high specific capacity (290 mAh g−1 at 500 mA g−1) and outstanding cycling stability after 2000 cycles. In-situ Raman spectroscopy and galvanostatic intermittent titration confirmed its surface-dominated potassium storage behavior with fast de-/potassiation kinetics, satisfactory reversibility, and fast ion/electron transport. This work guides an effective bionic strategy for the preparation of biomass carbon as high-performance anode materials.

Non-negligible Influence of Oxygen in Hard Carbon as an Anode Material for Potassium-Ion Batteries.

The development of potassium-ion batteries (PIBs) has been impeded by the lack of an appropriate carbon anode material that could accommodate K+ with a large ionic radius. Hard carbon with low cost and larger interlayer spacing is a promising anode material for PIBs. However, the impact of oxygen-containing functional groups in hard carbon (HC) is less reported. Herein, a hypercrosslinked polymer (HCLP) is prepared and used for the synthesis of microporous hard carbons with superior structural stability and abundant oxygen-containing functional groups and defects, in which the crosslinking agent provided copious oxygen atoms. It is found that a large number of C═O groups and micropores provide more storage sites for K+. The surface-controlled process is dominated by the reversible reaction of C═O + K+ + e- ↔ C-O-K, which directly increases the capacity contribution. The HCs obtained at 600 °C exhibit good cycling and rate performance with an initial specific capacity of about 254.3 mAh g-1 and the capacity retention of 83.2% after 200 cycles at 50 mA g-1. The capacity reached up to 121 mAh g-1 at 2 A g-1. A possible capacitive-adsorption mechanism is proposed by kinetic analysis. The redox reaction mechanism between C═O and K+ at the HC is clearly also revealed.

Self-templated anchor of FeS2 nanoparticles on porous carbon matrix as highly reversible K-storage anode

Owing to the high theoretical capacity and low cost, transition metal disulfides have been regarded as promising high-capacity anode materials for potassium-ion batteries (PIBs). However, the practical application is hindered by poor electrical conductivity and volume expansion during electrochemical cycle process, generating fast capacity decay and poor cycle stability. Herein, we propose anchoring FeS2 nanoparticles on N-doped porous carbon (FeS2@NPC) via a self-templated method. The reversible K-storage in FeS2 was guaranteed by the confinement in the porous NPC matrix which significantly enhanced the reaction kinetics via improving the electron/K+ transporting. As a result, FeS2@NPC exhibited superior-rate properties (451.6 and 331.2 mA h/g at 0.1 and 1 A/g, respectively) and long-term cycle stability (capacity attenuation is 0.055 % per cycle). These discoveries provide fundamental references for designing advanced Fe-based anodes for PIBs.

Construction of strongly coupled few-layer FePSe3-CNT hybrids for high performance potassium-ion storage devices

Given the layered crystal structure and tunable composition, ternary metal phosphorus trichalcogenides (MPCh3) is an attractive anode material for potassium-ion batteries with higher surface activity and mobility than their binary analogues. However, how to improve the electronic conductivity, ion diffusion, and maintain high reversible potassiation/depotassiation processes are the main key issues for the development of MPCh3-based electrodes with high rate and long cycle life. For example, theoretically, FePSe3 has a layered crystal structure with high electronic conductivity and low diffusion barrier, yet their K+-based electrochemical performance not well demonstrated. Here, we report a mechanical exfoliation method to prepare few-layer FePSe3-carbon nanotube (f-FePSe3/CNT) hybrids for use as high-efficiency K+ storage anodes. Electrochemical performance, kinetic analysis, reaction mechanism analysis, and density functional theory calculations show that this strongly coupled 1D-2D hybrids promotes the reaction and diffusion of potassium ions, giving full play to the inherent advantages of materials with different dimensions. Therefore, the f-FePSe3/CNT PIB anodes exhibit high capacity (472.1 mA h g−1, 0.05 A/g), high rate (124.9 mA h g−1, 10 A/g), and cycling stability (>1000 cycles), which significantly exceeds the performance of its binary analogue, here FeSe. In addition, the full cells of potassium-ion battery and hybrid capacitor coupled with f-FePSe3/CNT anodes exhibit good cycling stability (500 cycles) and high energy/power density of 54.7 W h kg−1/5790.8 W kg−1, respectively, revealing its practical applications in a wide range of K+-based storage systems. We believe that this work will provide a universal strategy for effectively activating the K+ electrochemical performance on a wide range of layered materials.

Cellulose/lignin-based carbon nanobelt aerogels coating on VSe2 nanosheets as anode for high performance potassium-ion batteries

Potassium-ion batteries (PIBs) have attracted high attention in recent years due to the low cost, low redox potential and abundant naturally storage. However, PIBs has been hampered by the large K+ ion and huge volumetric change, which lead to the poor electrochemical kinetic and cycling performance. Herein, the cellulose/lignin-based carbon nanobelt aerogels coating on VSe2 nanosheets (VSe2@CNB) as anode materials for PIBs has been fabricated for the first time by the selenization of VO(acac)2 and subsequent polymerization and coating by carbon nanobelt aerogels. The enhancing in the conductivity and the structural protection have been provided by the interlinked, high surface area and porosity carbon nanobelt aerogels, the VSe2@CNB shows improved potassium-storage performance, obtains high reversible capacity of 227.4 mAhg−1 at 100 mAg−1 after 100 cycles, as well as delivering long-term cycling stability of 125 mAhg−1 at 500 mAg−1 after 1000 cycles with high columbic efficiency (99%). Ex situ X-ray diffraction (XRD) and transmission electron microscope (TEM) measurement indicate that the reversible phase evolution for the storage potassium mechanism of the VSe2@CNB composite consists of K+ insertion into the layer of VSe2 nanosheets and conversion reaction of VSe2 transfer into K2Se.

Porous Structures Formed by Fluorine-Doped Reduced Graphene Oxide Sheets as High-Performance Anodes for Potassium-Ion Batteries

Polyvinylidene fluoride pyrolysis into fluorocarbon (CF) and the insertion of reduced graphene oxide (RGO) nanosheets to form porous CF@RGO nanocomposites and their application as anode materials for potassium-ion batteries were investigated. First, RGO serves as a foundation for CF nanoparticles and provides a good conductive network for improving the electrode conductivity and capacity of the electrode. In the meantime, it also functions as a buffer against volume changes during charging and discharging. Fluorine-doped mesoporous carbon can not only improve electrical conductivity and enhance long-term cyclic stability but also increase rate capacity. In addition, the higher electron cloud density of CF nanoparticles further enhances electronic interactions and provides more active sites for K+ embedding in the charge and discharge processes to maintain structural stability. Synergy between RGO and CF effectively relieves electric stress and provides a pathway for rapid electron and ion transport. The sheet structure of porous CF@RGO contributes to the stability of the SEI film, triggering excellent material retention and improving the electrochemical performance. Therefore, the porous CF@RGO electrode exhibits a high reversible capacity of 209.2 mA h g–1 after 200 cycles of 0.1 A g–1 and a high stable capacity of 338.0 mA h g–1 after 1000 cycles of 0.5 A g–1. Porous CF@RGO composites remain structurally stable and agglomeration free after 1000 charge and discharge cycles. This work provides a new strategy to construct carbon materials for reversible potassium ion storage.

Multidimensional antimony nanomaterials tailored by electrochemical engineering for advanced sodium-ion and potassium-ion batteries

Downsizing the dimensions of materials holds great importance for promoting the alkali-ion storage properties, which is considered to be one of the most efficient methods for improving the cycling stability and rate capability of alloy anodes. Nevertheless, efficient, affordable, and scalable methods to prepare low-dimensional electrode materials are lacking. In this study, we developed a tunable electrochemical strategy for synthesizing multidimensional antimony (Sb) nanomaterials. Depending on different reaction mechanisms in different electrolytes, we fabricated zero-dimensional Sb nanoparticles, two-dimensional (2D) antimonene nanosheets, and a three-dimensional porous Sb network through the electrochemical delamination of bulk Sb in lithium hexafluorophosphate in propylene carbonate, tetraethylammonium hydroxide aqueous solution, and tetraethylammonium hexafluorophosphate in N, N-dimethylformamide, respectively. In the preferred electrolyte, 2D antimonene nanosheets deliver a large sodium storage capacity of 572.5 mAh g−1 after 200 cycles at 0.2 A g−1 and an excellent rate capability of 553.6 mAh g−1 at 5 A g−1. When used as anode materials for potassium-ion batteries, we obtained a high capacity of 550.3 mAh g−1 after 300 cycles, and observed a high rate capability of 302.3 mAh g−1 at 4 A g−1. These results provide an easy and tunable strategy for designing high-performance low-dimensional materials for next-generation batteries.

Enhanced potassium storage property of copper phosphide anode by simultaneous carbon hybridization and porosity construction

Phosphorus-rich metal phosphide CuP2 promises low-cost and high-capacity anode materials for potassium-ion batteries (PIBs). Nonetheless, it suffers from poor electrochemical reversibility because of the dramatic volume effect during cycling. Herein, we construct a three-dimensional (3D) macroporous CuP2/carbon (t-CuP2/C) by a facile in-situ salt template strategy for the first time. The potassium ion storage mechanism of t-CuP2/C anode is preliminarily probed through ex-situ X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. It is found that CuP2 undergoes a displacement reaction with potassium, leading to microscopic phase separation between the discharge products Cu and KP. Percolated through the electrode, Cu forms a secondary conductive network around active P component, enhancing potassium storage performance. The as-synthesized t-CuP2/C electrode benefits from 3D porous carbon framework and microscopic displacement reaction, exhibiting a high reversible capacity of 479 mAh g−1 at 0.05 A g−1 and superior capacity retention of 83.5% after 1000 cycles at 2 A g−1. Furthermore, a full battery coupled with a potassium Prussian blue cathode achieves excellent cycle stability with 84.7% capacity retention after 100 cycles at 0.1 A g−1. The redox mechanistic understanding and modification methodology regarding CuP2 anode may provide insights into developing high-performance and low-cost PIBs.

Initial development of multiple anionic transition metal hydroxy selenide—A novel negative electrode material for potassium‐ion batteries

Multiple anionic anode materials for alkali metal-ion storage systems have received attention because of their remarkable electrochemical behavior in fabricating heterostructures after the initial cycle, which can provide an affirmative effect on ionic/electronic conductivity during cycling. Herein, for the first time, cobalt hydroxy selenide (Co(OH)Se) containing OH− and Se2− ions is prepared via a simple and facile liquid-phase selenization process using NaHSe solution, and its structural and chemical properties are studied by scanning transmission electron microscopy and X-ray photoelectron spectroscopy analyses. The electrochemical mechanisms of Co(OH)Se with potassium ions are investigated systematically through various ex situ and in situ techniques. The conversion reaction between Co(OH)Se and potassium ions can be proposed as the following equation; Co(OH)Se + 3 K+ + 3 e− → Co + KOH + K2Se ↔ ½ Co(OH)2 + ½ CoSe2 + 3 K+ + 3 e−. As an anode material for potassium-ion batteries, Co(OH)Se exhibited excellent cycling stability (414.7 mA h g−1 at 0.1 A g−1 after 60 cycles) and rate capability (194.7 mA h g−1 at 5.0 A g−1). Moreover, carbon-material composited Co(OH)Se@C delivered specific discharge capacity of 353.9 mA h g−1 at 0.1 A g−1 after 150 cycles. This study is a novel approach to the anion regulation strategy, which can be utilized for the synthesis of energy storage materials, electrocatalysts, etc.

Ultrathin Metallic NbS2 Nanosheets with Unusual Intercalation Mechanism for Ultra‐Stable Potassium‐Ion Storage

AbstractTransition metal dichalcogenides (TMDs) show great potential as anodes for potassium‐ion batteries (PIBs) due to their high theoretical capacity and relatively low working potential. However, usually the conversion mechanism seriously hinders the long‐term cycle stability for PIBs due to the huge structural change. Herein, the synthesis of a class of ultrathin metallic 2H‐phase NbS2 nanosheets with large expanded interlayer spacing of 0.65 nm and high conductivity for boosting the potassium ion storage is reported. It is demonstrated that the as‐prepared NbS2 nanosheets show an unexpected intercalation mechanism for potassium ion storage, which is conceptually different from the well‐known intercalation‐conversion mechanism of typical TMDs. As a consequence, the ultrathin NbS2 nanosheets deliver superior rate capability (205.5 mAh g−1 at ultrahigh current density of 10 A g−1) and outstanding long‐term cycling performance (169.5 mAh g−1 at 5 A g−1 after 4000 cycles with a very low decay rate of 0.005% per cycle), representing the most stable TMD‐based anode materials for PIBs. Ex situ measurements and first‐principles calculations disclose and interpret that NbS2 nanosheets store potassium ions through only the intercalation mechanism without any conversion reaction taking place in the potassiation/depotassiation process, which highly improves the structural stability of electrode materials, hence promoting the long‐term cycle performance.

In-situ synthesis of antimony nanoparticles encapsulated in nitrogen-doped porous carbon framework as high performance anode material for potassium-ion batteries

Antimony anodes for potassium-ion batteries (PIBs) have garnered considerable scholarly interest owing to their high theoretical specific capacity and low operation potential for alloying with potassium. However, the large volume expansion during alloying in Sb anodes results in rapid capacity fading. Thus, in this study, we proposed a simple, one-step, cost-effective carbothermal reduction method to synthesize a nanostructured Sb encapsulated in an N-doped porous carbon framework (Sb@NPC). The optimized Sb@NPC-2 electrode, which was obtained using a Sb2O3:polyvinylpyrrolidone (PVP) molar ratio of 1:3, offered a high reversible capacity of 587.7 mAh g−1 at 100 mA g−1 over 50 cycles, 492 mAh g−1 at 200 mA g−1 over 100 cycles, and 360.8 mAh g−1 at 800 mA g−1 with a capacity retention of 75.7% over 500 cycles. Even at a high specific current of 4000 mA g−1, the electrode maintained a high reversible capacity of 385 mAh g−1, implying adequate rate capability. In addition, a full cell composed of Sb@NPC-2 anode and KFe[Fe(CN)6⋅xH2O] cathode exhibited excellent cycling stability by showing an exceptional reversible capacity of 432.5 mAh g−1, corresponding to a high capacity retention of 98% over 150 cycles. These excellent results were primarily attributed to the successful encapsulation of nanostructured Sb nanoparticles in the NPC, as well as the formation of a KF-rich solid electrolyte interphase film on the electrode surface. Furthermore, the simulation result based on density functional theory (DFT) revealed that N-doping in the porous carbon framework enhanced the electrical conductivity and Sb−K binding.

Low-cost and high-rate porous carbon anode material for potassium-ion batteries

Potassium enhances the advantages of abundant reserves, low cost, and low standard electrode potential. Therefore, potassium ion batteries have recently received a lot of attention and research as an ideal low-cost secondary battery system. In this paper, the template method is utilized to prepare porous carbon anode material for potassium ion batteries using low-cost calcium carbonate as the template and sucrose as the carbon source. The material has unordered microstructure, large specific surface area, and hierarchical porous structure formed by “macropore-mesopore-micropore”. Electrochemical test results show that the prepared porous carbon anode material has a specific capacity of 259.5 mAh·g−1 at a current density of 50 mA·g−1, and the capacity retention rate is 92.8% after 100 cycles. After the cycle, the pole piece has a flat surface without obvious cracks, indicating that the material experienced a small volume change during the potassium ion intercalation/deintercalation process. Porous carbon material exhibits good rate performance at a high current density of 2000 mAh·g−1, with a specific capacity of 129.6 mAh·g−1 after 10,000 cycles.

An α-MnSe nanorod as anode for superior potassium-ion storage via synergistic effects of physical encapsulation and chemical bonding

Conversion mechanism anode materials have been widely employed for potassium ion batteries (PIBs) due to high theoretical specific capacities. However, large volume expansion and poor electrochemical kinetics have become the key bottlenecks hindering its further development. Herein, α-MnSe nanorods wrapped by N-doped carbon and graphene (α-MnSe@NC@graphene) are constructed as anode materials for PIBs. The architecture can not only provide superior electrode integrity to buffer volume variation and maintain structure stability via synergistic effects of physical encapsulation and Mn-C chemical bonding, but also serve as conductive network to accelerate the electron transfer and K-ion diffusion. As a result, α-MnSe@NC@graphene composite delivers high initial charge specific capacity of 307.9 mAh·g−1 and great cycling stability over 250 cycles with the capacity retention of 232.8 mAh·g−1 at 50 mA·g−1. Besides, superior rate capability (91.1 mAh·g−1 at 2.0 A·g−1) and long lifespan over 700 cycles at 1.0 A·g−1 with the low capacities decay rate of 0.064% per cycle can be acquired. Ex situ TEM and XPS results verify that K-ion insert into/extract from α-MnSe@NC@graphene through a conversion mechanism based on the Mn-ion redox site (MnSe + 2 K+ + 2e- ↔ Mn + K2Se).