Anode For Potassium-ion Batteries Research Articles

Confined Bismuth-Organic Framework Anode for High-Energy Potassium-Ion Batteries.

Metal-organic frameworks (MOFs) with inherent porosity, controllable structures, and designable components are recognized as attractive platforms for designing advanced electrodes of high-performance potassium-ion batteries (PIBs). However, the poor electrical conductivity and low theoretical capacity of many MOFs lead to inferior electrochemical performance. Herein, for the first time, a confined bismuth-organic framework with 3D porous matrix structure (Bi-MOF) as anode for PIBs via a facile wet-chemical approach is reported. Such a porous structure design with double active centers can simultaneously ensure the structure integrity and efficient charge transport to enable high-capacity electrode with super cycling life. As a result, the Bi-MOF for PIBs exhibits high reversible capacity (419 mAh g-1 at 0.1 A g-1 ), outstanding cycling stability (315 mAh g-1 at 0.5 A g-1 after 1200 cycles), and excellent full battery performance (a high energy density of 183Wh kg-1 is achieved, outperforming all reported metal-based anodes for PIBs). Moreover, the K+ storage mechanisms of the Bi-MOF are further unveiled by in situ Raman, ex situ high-resolution transmission electron microscopy, and ex situ Fourier-transform infrared spectroscopy. This ingenious electrode design may provide further guidance for the application of MOF in energy storage systems.

Turbostratic Lattice and Electronegativity Modification Jointly Enabled an Ultra-High-Rate and Long-Lived Carbon Anode for Potassium-Ion Batteries

Potassium-ion batteries (PIBs) are considered as a promising technology alternative to lithium-ion batteries due to more abundance of potassium than lithium and a lower redox potential of K/K+ than that of Na/Na+. The critical limitation in PIBs is the electrode with poor rate capability and cycling stability induced by the sluggish reaction kinetics and large volume change during potassiation and depotassiation. In this work, we report a turbostratic lattice iodine-doped carbon (TLIC) nanosheet as an advanced innovative anode for PIBs displaying fast charge/discharge and electrode stability. The turbostratic lattice caused by doping of large-sized iodine and the unique charge transfer between iodine/carbon atoms creates more active sites and a shorter transport distance for K ions, improves the electrochemical activity, promotes rapid ion diffusion, and enhances pseudocapacitive behavior. The TLIC exhibits a high capacity of 433.5 mAh g-1 at 50 mA g-1, an ultrahigh rate capability of 162.1 mAh g-1 at 20 A g-1, and an excellent capacity retention of ∼96% (206 mAh g-1) after 4000 cycles. The combination of turbostratic lattice and pseudocapactive storage is an effective approach to designing carbon electrodes with the transformational performance of high capacity, rate performance, and long lifetime for practical applications of PIBs.

A New Candidate in Polyanionic Compounds for Potassium Ion Battery Anode: MXene Derived Carbon Coated π‐Ti2O(PO4)2

AbstractIntercalation‐type reaction that occurs in polyanion materials is considered to be a facile way to counter the mismatched relationship between the large K+ and compact host structure for potassium ion batteries (PIBs). However, the large “dead” weight and poor conductivity introduced by the polyanion framework severely limit the electrochemical performance of polyanion anodes. Herein, a new rigid K+ host of 1D π‐Ti2O(PO4)2 with carbon‐coated (TOP@C) is simply synthesized through a simple Ti3C2Tx‐derived method. The density functional theory (DFT) calculations and experimental results show that the potassium storage properties are unquestionably improved by the small cell volume change during cycling, the intercalation pseudo‐capacitance energy storage mechanism, and the large K‐storage tunnels with lower migration energy (0.23 eV) of TOP@C anode (134.5 mAh g‐1 after 2000 cycles at 1.0 A g‐1). The TOP@C//PTCDA full batteries, which clearly illustrate their promising application in advanced PIBs, successfully achieved a high energy density of 119.4 Wh kg‐1 and a power density up to 632.8 W kg‐1 with regard to the total mass of TOP@C and PTCDA.

Enhanced electrochemical and environmental stability of black phosphorus-derived phosphorus composite anode for safe potassium-ion battery using amorphous zinc phosphate as a multi-functional additive

Black phosphorus (BP) presents high theoretical capacity as potassium-ion battery (PIB) anode, while low ionic/electronic conductivity for bulk phase and high volume expansion and extremely sensitivity to humid environment for its nanomaterial hinder its practical applications. Here, we propose BP nanocomposites with amorphous zinc phosphate to tackle above problems. The amorphous zinc phosphate plays multifunctional roles in weakening the agglomeration of BP nanomaterials, reducing the volume expansion and improving the environmental stability of BP nanocomposite electrodes in humid air. The optimized amorphous BP nanocomposite anode with 30wt% zinc phosphate, [email protected]@ZPO(30), retains capacity of 369.0 mA h g–1 after 500 cycles at 0.5 A g–1 in a noninflammable triethyl phosphate (TEP) electrolyte, and the volume expansion rate of the [email protected]@ZPO(30) electrode is reduced to 47% compared with [email protected]@ZPO(0) electrode of 100%. More attractively, the amorphous zinc phosphate improves the environmental stability of the nanocomposite electrode in humid air dut to its features of strong and fast physical absorption to water. Consequently, the [email protected]@ZPO(30) electrode delivers a reversible capacity of 629.2 mA h g–1 (200 cycles at 0.2 A g–1) even after exposing the electrode to humid air for two days. Such nanocompositing strategy may accelerate the practical application of phosphorus electrode.

Tailoring stress-relieved structure for ternary cobalt Phosphoselenide@N/P codoped carbon towards high-performance potassium-ion hybrid capacitors and potassium-ion batteries

The sluggish redox kinetics and severe volume changes of potassium-ion hosts are the challenging issues for potassium ion hybrid capacitors (PIHCs) and potassium-ion batteries (PIBs). Herein, a novel ternary cobalt phosphoselenide (CoPSe)@N/P co-doped carbon (NPC) composite with stress-relieved structure is introduced as anodes for PIHCs and PIBs. The ultrafine CoPSe nanocrystallites are embedded in the N and P codoped carbon matrix to form the spherical units. Then the resultant “nano-balls” are encapsulated in the tyre-like hollow framework to construct the “ball-in-tyre” (BIT) structure. Both dual carbon decorations and ultrafine crystals of BIT structure favor the fast electron/ion transports and significantly depress the internal stress. Meanwhile, the strong interfacial interaction between the ternary CoPSe crystal and N/P codopant carbon matrix favor the fast kinetics and high stability of the composite. For the first time, the [email protected] BIT composite is constructed via a facile bio-cooperated approach, where the local bio-combustion, in-situ phosphorization and selenization synchronize. Density function theory (DFT) result reveals the improved intrinsic conductivity, enhanced potassium adsorption and diffusion capabilities of the [email protected] heterostructure. Finite element simulations (FEA) suggest the depressed stress with uniform distributions internal the BIT structure during ion insertion/deinsertion processes. Electrochemical results demonstrate the superior high-rate capability and excellent cycling stability of [email protected] BIT composite in potassium-ion systems. Moreover, the PIHCs and PIBs full cell are fabricated based on the [email protected] BIT anodes. They exhibit the high energy density, high power density and high durability over long-term cycles. More impressively, both devices exhibit good abuse tolerance under diverse outside deformations or in a wide temperature range, which enable them promising power sources for diverse applications.

A high-tortuosity holey graphene in-situ derived from cytomembrane/cytoderm boosts ultrastable potassium storage

• A high-tortuosity holey graphene was successfully prepared based on the unique flake structure and chemical composition of cytomembrane and cytoderm. • Benefiting from the unique nanoholes shortening the ion-diffusion length, the synergy of wrinkled and holey structure stabilizing volume fluctuation, the enhanced electronic conductivity and specific surface area. • The anode achieves excellent reversible capacity, and exceptional rate capability with an ultra-long cycle lifespan in PIBs. • The anode exhibits a high energy density as well as considerable cycling stability for potassium-ion full cells. The sluggish K + kinetics and structural instability of the generally-used graphite and other carbon-based materials hinder the development of potassium-ion batteries (PIBs) for high-rate capability and long-term cycling. Herein, inspired by the unique flake structure and chemical composition of cytomembrane and cytoderm, we design high-tortuosity holey graphene as a highly efficient anode for PIBs. The flake cytomembrane and cytoderm shrink into wrinkled morphology during drying and sintering and then convert into high-tortuosity graphene after oxidative exfoliating and thermal reducing process. Meanwhile, the proteins, sugars, and glycolipids embedded in cytomembrane and cytoderm can in-situ form nanoholes with highly abundant oxygenic groups and heteroatoms around, which can be easily removed and finally the high-tortuosity holey graphene is obtained after a thermal reducing process. The stress distribution after K + intercalation confirms the optimized release of strain caused by the volume change through the finite element method. Benefiting from the unique nanoholes shortening the ion-diffusion length, the synergy of wrinkled and holey structure stabilizing volume fluctuation, and the enhanced electronic conductivity and specific surface area, the high-tortuosity holey graphene demonstrates high reversible capacities of 410 mAh g –1 at 25 mA g –1 after 150 cycles and retains 91.5% at 2 A g –1 after 2500 cycles.

Edge Coordination of Ni Single Atoms on Hard Carbon Promotes the Potassium Storage and Reversibility.

Hard carbon is the most promising anode for potassium-ion batteries (PIBs) due to its low cost and abundance, but its limited storage capacity remains a major challenge. Herein, edge coordination of metal single atoms is proved to be an effective strategy for promoting potassium storage in hard carbon for the first time, taking B, N co-doped hard carbon nanotubes anchored by edge Ni-N4 -B atomic sites (Ni@BNHC) as an example. It is revealed that edge Ni-N4 -B can provide active sites for interlayer adsorption of K+ and that Ni atoms can facilitate the reversibility of K+ storage on N and B atoms. Furthermore, an unprecedentedly reversible K+ storage capacity of 694mAhg-1 at 0.05Ag-1 is realized by introducing commercial carbon nanotubes. This work provides a new perspective for the application of single-atom engineering and the design of high-performance carbon anodes for PIBs.

Achieving Stable and Ultrafast Potassium Storage of Antimony Anode via Dual Confinement of MXene@Carbon Framework.

Antimony-based anode materials are recognized for their high potassium storage capacities and appropriate operating potentials. However, the large volume expansion of Sb during the potassiation/depotassiation process, which results in a quick capacity decay, severely limits its practical application in potassium-ion batteries (PIBs). Here, a carbon-coated Sb/MXene heterostructure composite (CSM) is synthesized by adsorption of Sb3+ on MXene nanosheets via Sb-O-Ti bonds followed by carbothermic reduction to construct dual-confined MXene@carbon conductive framework capable of withstanding high volume expansion of Sb and conducive to enabling accelerated electron transfer kinetics. The CSM composite, particularly CSM-700, when configured as an anode for PIBs, realized high capacity (484.4mAh g-1 at 0.1A g-1 ), an ultra-stable cycling performance with a high reversible capacity of 435.9mAh g-1 at 0.1A g-1 after 100 cycles corresponding to a capacity retention rate of 90.0%, and superior rate performance of 323.0mAh g-1 at 1A g-1 . The proposed strategy offers a simple route to construct high-performance Sb-based anodes for advanced PIBs.

Sulfur-grafted hard carbon with expanded interlayer spacing and increased defects for high stability potassium-ion batteries

Carbon materials have been proven to be an effective anode for potassium-ion batteries (PIBs) due to their high safety, low cost, and environmental benignity. However, the repeated insertion/extraction of K-ions with a larger size into/from electrode at low voltage region will inevitably cause obvious volume expansion, easily resulting in poor cycle stability. Hence, we synthesize S-doped hard carbon material (NSHCM2) using biomass as carbon and thiourea as S sources. Various characterizations demonstrate that the introduced S-heteroatom not only expands the distance between carbon layers, but also creates more defects. The former ensures the free intercalation/deintercalation of K-ions without structure deformation, while the latter can provide numerous active sites to adsorb K-ions, all these together contribute to structure stability and reversible capacity. As a result, the optimized NSHCM2 electrode delivers a high capacity of 294 mAh g−1 at 200 mA g−1 and an ultra-long cycling stability by achieving 220 mAh g−1 at 2000 mA g−1 over 5000 cycles. This simple and high effective synthesis route makes durable and fast potassium storage possible.

Sb2Te3 hexagonal nanoplates as conversion-alloying anode materials for superior potassium-ion storage via physicochemical confinement effect of dual carbon matrix

Anode materials with conversion-alloying dual mechanism are crucial for the development of high energy density potassium-ion batteries (PIBs), while large volume expansion and poor dynamic behavior hinder its development. Herein, nanoplate-structured Sb2Te3 anchored on graphene and N-doped C (Sb2Te3@rGO@NC) is regarded as anode material for PIBs for the first time. The dual encapsulation effect of Sb2Te3@rGO@NC composite with strong chemical bonding of Sb—C can not only significantly restrain the large volume expansion to maintain the electrode integrity, but also efficiently enhance the electronic transfer, K-ion adsorption and diffusion ability, verified by first principles calculations and electrochemical kinetics study. As a result, the resultant Sb2Te3@rGO@NC electrode delivers a high initial charge specific capacity of 384.9 mAh·g−1 at 50 mA·g−1, great rate capability and long-term lifetime over 200 cycles at 200 mA·g−1. Ex situ TEM and XPS results clarify that the electrode undergoes typical conversion-alloying dual-mechanisms with 12 mol K-ion transfer per formula employing Sb-ion as redox site (Sb2Te3 + 12 K+ + 12e- ↔ 3K2Te + 2K3Sb). This work could pave the way for the fast development of Sb2Te3-based anode for PIBs, and help to understand the K-ion storage mechanism.

Templated synthesis of imine-based covalent organic framework hollow nanospheres for stable potassium-ion batteries

Covalent organic frameworks (COFs), as highly tunable porous crystalline materials, have promising applications in potassium-ion batteries (PIBs) due to their abundant charge carrier transport channels and excellent structural stability. However, the excessive stacking of interlayer electron clouds makes it difficult to expose internal active sites. Strategies to design functional COFs with controllable morphology and copious active sites are promising but still challenging. Herein, by utilizing the condensation between 1,3,5-triformylbenzene (TFB) and p-phenylenediamine (PPD) and using amino-modified SiO2 nanospheres as templates, we synthesize core-shell NH2-SiO2@TP-COF. Through NaOH etching of NH2-SiO2@TP-COF, we obtain imine-based TP-COF hollow nanospheres, which shows excellent potassium storage performance when applied to the anode for PIBs. Ex-situ analysis and density functional theory calculations reveal that CN groups and benzenes are active sites for K+ storage.

Growth confinement and ion transportation acceleration via an in-situ formed Bi4Se3 layer for potassium ion battery anodes

Bismuth has gained increasing attention as anodes for advanced potassium-ion batteries because of its high theoretical capacity and suitable voltage plateaus. Although nanosized Bi structures display better properties, their syntheses still remain a great challenge because the low melting point of Bi makes it easily to aggregate into large ingots. Herein, the thin Bi4Se3 coating layer combined with N-doped carbon was introduced onto the Bi nanospheres to chemically confine their overgrowth via an in-situ selenization process. Theoretical calculation and experimental results indicated that the Bi4Se3 coating layer not only exhibits better affinity towards Bi-atoms compared with that of carbon sheet, but also can boost the K-ion diffusion kinetics. In addition, the Bi4Se3 coating layer was unraveled to undergo a reversible conversion/alloying mechanism with unique final discharged products of K3BiSe3 and K3Bi, which was responsible for the improved discharge capacity and better cycle properties (A higher capacity of 300 mAh/g maintained after 50 cycles, while it was only 210 mAh/g for the Bi@C electrode). Our work presents an effective and general approach to circumvent the overgrowth issues of bismuth anodes and other metal anodes with low melting points for advanced battery applications.

Bimetal heterostructure NiCo2Se4 anode confined by carbon nano boxes for ultrafast and stable potassium storage

Transition metal selenides (TMSes) are regarded as promising anodes for potassium ion batteries (PIBs) benefit from their high theoretical capacity. However, the slow kinetics of potassium ion transport, poor charge transfer ability and short cycle life limit the development of transition metal selenide anode. In this article, the dice-shaped NiCo2Se4@N-doped carbon (NCS@NC) nanocomposite is designed for efficient and stable potassium storage. The in-situ formed carbon shell can not only act as a highly conductive framework to accelerate charge transfer, but also limit the volume fluctuation caused by the potassium ion repeated insertion/ extraction process. The in-situ and ex-situ characterization as well as theoretical calculation show that the heterogeneous interface formed by the heterogeneous metal species in NCS@NC spontaneously establish internal electric fields, which significantly accelerates the ion transport. As results, advanced NCS@NC anode with greatly enhanced electrochemical performance is obtained due to the synergy between the three-dimensional structure design and the heterogeneous interface strategy. NCS@NC anode displays extraordinary rate capacity (471.9 mAh g-1 at 2 A g-1) and ultralong cycle life at high current density (454.5 mAh g-1 at 2 A g-1 after 1000 cycles), which indicates that our modification strategy provides an alternative solution for designing advanced PIBs anodes.

A comparison of the electrochemical performance of graphitized coal prepared by high-temperature heating and flash Joule heating as an anode material for lithium and potassium ion batteries

Natural graphite, commonly used in energy storage applications such as the battery industry, is marked as a supply-risk material due to the elevated demand and limited resources. The synthetic graphite process is inefficient, so there is a highly required for alternative methods of making graphite as anode material. In this study, we report two efficient methods for catalytic graphitization of coal using high-temperature heating and flash Joule heating (FJH). Using both methods, the structure and morphology characterizations have demonstrated the successful structural conversion of coal from an amorphous structure into a crystalline structure. When the obtained graphitized coal samples via the high-temperature heating method (HTC) and via the FJH method (FHC) were used as anodes for lithium-ion batteries (LIBs) and potassium-ion batteries (PIBs), the HTC and FHC presented outstanding rate capability and remarkable stable cycling performance. The HTC and FHC anodes delivered initial charge capacities of 322.5 and 321.3 mAh·g−1, respectively, at a current density of 0.1C. for LIBs. When used as anodes in PIBs, the HTC and FHC delivered initial charge capacities of 265.4 and 262.2 mAh·g−1 at 0.1C current density. These results make the HTC and FHC promising materials for developing energy storage applications. Therefore, this work exploited the low price of coal and its abundant reserves, combined with the FJH technique, which is an effective method for saving energy and time, to produce high-quality graphitized coal materials, which can make this process green and economically attractive.

Research Progress of Constructing Anode Materials for Potassium Ion Batteries Based on Electrospinning Technology

Potassium offers the benefits of plentiful supplies, widespread availability, and inexpensive cost. Potassium-ion batteries (KIBs) are thought to be one of the best energy storage technologies to take the place of lithium-ion batteries in the future since potassium has a low electrode potential and rapid ion transport kinetics in the electrochemical system. As opposed to lithium-ion batteries, potassium-ion battery research is still in its early stages, and the system has issues with low capacity, inferior rate performance, and short cycle life. As a result, creating safe, dependable, and high-performance charge-discharge potassium-ion batteries still presents several difficulties. One of the main elements promoting the development of potassium-ion batteries is the development of anode materials for these batteries. At present, there are various methods for constructing potassium-ion battery anode materials, including hydrothermal method, solid phase reaction, electrospinning method, etc. The advancement of electrospinning and the creation of potassium-ion battery anode materials based on electrospinning are the main topics of this review article. This report also anticipates the direction of research and development for high-performance, low-cost anode materials.

In-situ catalytic mechanism coupling quantum dot effect for achieving high-performance sulfide anode in potassium-ion batteries

Though numerous framework structures have been constructed to strengthen the reaction kinetics and durability, the inevitable generation of polysulfide dissolution during conversion-process can cause irreparable destruction to ion-channel and crystal structure integrality, which has become a huge obstacle to the application of metal-sulfide in potassium-ion batteries. Herein, the quantum dot structure with catalytic conversion capability is synchronously introduced into the design of FeS2 anode materials to heighten its K+-storage performance. The constructed quantum dot structure anchored by the graphene with space-confinement effect can shorten the ion diffusion path and enlarge the active area, thus accelerating the K+-ions transmission kinetics and absorption action, respectively. The intermediate phase of formed Fe-nanoclusters possesses high-active catalysis ability, which can effectively suppress the polysulfide shuttle combined with the enhanced absorption effect, fully guaranteeing the structure stability and cycling reversibility. Predictably, the fabricated quantum dot FeS2 can express a prominent advantage in rapid potassiation/depotassiation processes (518.1 mAh g−1, 10 A g−1) and a superior cycling lifespan with gratifying reversible capacity at superhigh rate (177.7 mAh g−1, 9000 cycles, 5 A g−1). Therefore, engineering quantum dot structure with self-induced catalysis action for detrimental polysulfide is an achievable strategy to implement high-performance sulfide anode materials for K-ions accommodation.

3D Porous Co3O4/MXene Foam Fabricated via a Sulfur Template Strategy for Enhanced Li/K-Ion Storage.

Co3O4 is a potential high-capacity anode material for lithium-ion batteries (LIBs) and potassium-ion batteries (PIBs), but the poor electrical conductivity and large volume fluctuations during long-term cycling severely limit its cycle durability and rate capabilities, especially for PIBs with large K-ion size. Here, we propose a sulfur template route to fabricate an integral 3D porous Co3O4/MXene (Ti3C2Tx) foam using simple vacuum co-filtrating an aqueous dispersion of Co3O4, S and MXene followed by calcining to remove the S template. The 3D porous structure can easily accommodate the large volume changes of Co3O4 while maintains electrode structural integrity, allowing to realize outstanding long-term cycle stability when tested as anodes for both LIBs (620.4 mA h g-1 after 1000 cycles at 1 A g-1) and PIBs (134.1 mA h g-1 after 1000 cycles at 0.5 A g-1). The high metallic conductivity of the 3D porous MXene network further facilitates the electron/ion transmission, resulting in an improved rate capability of 390 mA h g-1 at 13 A g-1 for LIBs and 125.3 mA h g-1 at 1 A g-1 for PIBs. The robust performance of the 3D porous Co3O4/MXene foam reflects its perspective as a high-performance anode material for both LIBs and PIBs.

Spatially dual-confined metallic selenide double active centers for boosting potassium ion storage

Potassium-ion batteries (PIBs) have received increased attention for grid-scale energy storage applications; however, their practical development is still hindered by the lack of advanced anode materials to overcome the slow kinetics and huge volume expansion. Herein, a multi-interface engineered iron-nickel bimetallic selenide (NiSe2/FeSe2, NFS) space-confined in a dual-carbon structure is designed as an efficient anode for PIBs. The NFS heterostructure with different band structures endows a built-in electric field, which facilitates fast interfacial electron transport and reduced ionic diffusion resistance. Moreover, the NC@C matrix further accelerates the charge carrier transport dynamics of NFS while suppressing the huge volume change to ensure good cycling performance. Consequently, the as-prepared NFS@NC@C exhibits a high initial specific capacity of 349.6 mA h g−1 at 0.1 A/g, good rate capability, and ultra-low capacity degradation rate of 0.021 % per cycle after 1200 cycles at 5 A/g. Further ex/in-situ investigations and theoretical calculations unveil the K+ storage mechanism of NFS@NC@C, which involves a phase conversion reaction for K+-ions migration with a low diffusion energy barrier. This work heralds the prospect of space-confined multi-heterointerface design for high-performance PIBs electrode materials.

Reduced graphene oxide coated modified SnO2 forms excellent potassium storage properties

In this work, SnO2 and Sn nanoparticles adhered to the surface of rGO (SnO2/Sn/rGO) applied as potassium ion batteries (KIBs) anode materials were synthesized via thermal reduction. Preparing SnO2 material into a nanostructure for modification can reduce ion diffusion distance to improve the number of active sites appropriate for K+ adsorption, and efficiently reduce the volume change which is conducive to enhancing the potassium storage capacity. Besides, layered rGO inhibits SnO2/Sn aggregation, while increased surface area also reduces diffusion channel and electrolyte contact. However, larger specific surface area result in a lower initial Coulomb efficiency (ICE). The approach adopted here is to force the solid electrolyte interface (SEI) to fully emerge during the first charge-discharge cycle by using electrolytes containing 1 M KFSI in EC and DEC (1:1, v/v). According to density functional theory (DFT) analysis, the doping of rGO and SnO2 effectively enhanced the adsorption of potassium atoms and reduced the diffusion barrier of K+. Therefore, SnO2/Sn/rGO nanocomposites have a high specific capacity (325.8 mAhg−1 after 350 cycles at 0.1 Ag-1), an excellent ICE (66.57%), and a long cycle life (203.6 mAhg−1 after 1000 cycles at 0.5 Ag-1).

Controllable Synthesis of Carbon Yolk-Shell Microsphere and Application of Metal Compound-Carbon Yolk-Shell as Effective Anode Material for Alkali-Ion Batteries.

Recently, nanostructured carbon materials, such as hollow-, yolk-, and core-shell-configuration, have attracted attention in various fields owing to their unique physical and chemical properties. Among them, yolk-shell structured carbon is considered as a noteworthy material for energy storage due to its fast electron transfer, structural robustness, and plentiful active reaction sites. However, the difficulty of the synthesis for controllable carbon yolk-shell has been raised as a limitation. In this study, novel synthesis strategy of nanostructured carbon yolk-shell microspheres that enable to control morphology and size of the yolk part is proposed for the first time. To apply in the appropriate field, cobalt compounds-carbon yolk-shell composites are applied as the anode of alkali-ion batteries and exhibit superior electrochemical performances to those of core-shell structures owing to their unique structural merits. Co3 O4 -C hollow yolk-shell as a lithium-ion battery anode exhibits a long cycling lifetime (619mA h g-1 for 400 cycles at 2 A g-1 ) and excellent rate capability (286mA h g-1 at 10 A g-1 ). The discharge capacities of CoSe2 -C hollow yolk-shell as sodium- and potassium-ion battery anodes at the 200th cycle are 311mA h g-1 at 0.5 A g-1 and 268mA h g-1 at 0.2 A g-1 , respectively.