Stable Solid Electrolyte Interface Research Articles

Double Confined MoO2/Sn/NC@NC Nanotubes: Solid-Liquid Synthesis, Conformal Transformation, and Excellent Lithium-Ion Storage.

The rational design of a hollow heterostructure promotes the development of highly durable anode materials for lithium-ion batteries. Herein, carbon-confined MoO2/Sn/NC@NC heterostructured nanotubes evolving from MoO3 nanorods have been successfully synthesized for the first time. In the growth of the Mo/Sn precursor, a peculiar microstructure evolution occurs from solid rods to hollow tubes through a solid-liquid reaction. The MoO2/Sn composite is restricted within the double carbon layer after subsequent annealing and carbonization that distinctly inherits the morphology of the Mo/Sn precursor. The resulting electrode shows good capacities with hardly any attenuation (925.4 mA h g-1 after 100 cycles at 100 mA g-1) and excellent long cycle life (620.1 mA h g-1 after 1000 cycles at 2 A g-1). The MoO2/Sn/NC@NC nanotubes contain the synergistic effect, elaborate core-shell structure, large specific surface areas, and abundant voids. These superiorities not only provide beneficial channels for the electrolyte to fully come into contact with electrode materials and more active sites for redox reactions but also effectively alleviate the volume fluctuation and sustain the electrical connectivity to retain a stable solid-electrolyte interface layer, indeed, bringing about the prominent Li-storage performance. The present study paves a feasible avenue to prepare core-shell structures with high reversible capacity and long-term cycle performance for energy storage devices.

Novel synthesis and electrochemical properties of fluoride cathode with a yolk–shell structure for K-ion battery

K-ion batteries (KIBs) have attracted considerable attention because of their unique advantages. Manganese-containing electrode materials have poor cycle performance due to the dissolution of manganese in the electrolyte. Here, manganese-containing KIB cathode with a yolk–shell structure is synthesised by a homogeneous precipitation method. In addition, large charge–discharge capacity and good cycle stability are obtained. Electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS) are used to understand the improvement in the electrochemical performance caused by the developed material. Due to the volume-buffering effect, the yolk–shell structure does not cause particle rupture, which helps form a stable solid–electrolyte interface (SEI) film. This reduces the number of Mn ions exposed to the electrolyte and results in long-term cycle stability. This work provides a universal route to improve the cycling performance of manganese-containing cathode for KIBs applications.

Double-network composite solid electrolyte with stable interface for dendrite-free Li metal anode

The application of solid polymer electrolytes for Li metal batteries (LMBs) is hindered by the Li/electrolyte interface instability and poor mechanical strength. Herein, a flexible composite solid electrolyte with a cross-linked double-network structure of inorganic particles and polymer was constructed by an in situ gel-sol method. The as-prepared electrolyte promoted the formation of a stable solid electrolyte interface on the Li metal surface and suppressed the formation of Li dendrites more than pure polymer electrolytes. Particularly, X-ray photoelectron spectroscopy results demonstrated the beneficial effect of inorganic particles for suppressing the side reactions between the Li metal and polymer. Additionally, the as-prepared electrolyte exhibited a reduction of polymer crystallinity, which can facilitate Li+ transport by weaking the interactions between Li+ and the polymer chains. The Li|Li symmetric batteries were stabilized to maintain successive electrodeposition over 1400 h of the plating/stripping process. Furthermore, the Li|LiFePO4 batteries displayed excellent cycling performance at a rate of 0.3 C, revealing tremendous potential in promoting the large-scale application of future LMBs.

Effects of charging protocols on the cycling performance for high-energy lithium-ion batteries using a graphite-SiOx composite anode and Li-rich layered oxide cathode

High-energy lithium-ion batteries (LIBs) using Si-based anode and Li-rich layered oxide (LLO) cathode suffer severe capacity degradation during cycling, which is directly affected by the charging protocols. In this paper, the effect of constant current (CC) and constant current-constant voltage (CC-CV) charging on the cycling performance of graphite-SiOx/LLO pouch-type batteries is studied. Unexpectedly, after 300 cycles, the batteries under the CC-CV protocol show capacity retention of 71.22%, batteries under the CC protocol, however, show capacity retention of only 64.02%. For the batteries using the CC protocol, the electrochemical test results reveal an unstable change in the electrode/electrolyte interface resistance and bigger lithium ion diffusion resistance. The postmortem analyses further indicate a solid electrolyte interface (SEI) film with lower chemical stability and a greater loss of active lithium and Si in the anode. Compared with the CC protocol, the batteries under the CC-CV protocol possess a more stable SEI film and a smaller loss of active lithium and Si. This work has certain reference significance for optimizing the charging protocol.

Building stable solid electrolyte interphases (SEI) for microsized silicon anode and 5V-class cathode with salt engineered nonflammable phosphate-based lithium-ion battery electrolyte

Silicon is one of the most promising anode materials for lithium-ion batteries due to its low cost, high energy density and abundant resources. However, fast capacity decay caused by the huge volume changes and the unstable solid electrolyte interface (SEI) limits its commercial applications. In this work, the effects of lithium hexafluorophosphate (LiPF6) and lithium difluoroacetate borate (LiDFOB) on the performance of microsized silicon anode were compared using nonflammable pure trimethyl phosphate (TMP) as the solvent. It is found that microsized silicon anode with 1 M LiDFOB/TMP electrolyte can produce a more stable solid electrolyte interface (SEI), which effectively prevents capacity loss. The capacity has a high retention even after 100 cycles with nearly 100% coulombic efficiency. Moreover, 5V-class cathode shows a better cycling stability with LiDFOB salt. This work may provide a novel direction for expanding the fields of lithium-ion batteries anode which has high safety and high energy density.

Highly Stable Cycling of Silicon-Nanographite Aerogel-Based Anode for Lithium-Ion Batteries.

Silicon anodes are considered as promising electrode materials for next-generation high capacity lithium-ion batteries (LIBs). However, the capacity fading due to the large volume changes (∼300%) of silicon particles during the charge–discharge cycles is still a bottleneck. The volume changes of silicon lead to a fracture of the silicon particles, resulting in recurrent formation of a solid electrolyte interface (SEI) layer, leading to poor capacity retention and short cycle life. Nanometer-scaled silicon particles are the favorable anode material to reduce some of the problems related to the volume changes, but problems related to SEI layer formation still need to be addressed. Herein, we address these issues by developing a composite anode material comprising silicon nanoparticles and nanographite. The method developed is simple, cost-efficient, and based on an aerogel process. The electrodes produced by this aerogel fabrication route formed a stable SEI layer and showed high specific capacity and improved cyclability even at high current rates. The capacity retentions were 92 and 72% of the initial specific capacity at the 171st and the 500th cycle, respectively.

Artificial SEI for Superhigh-Performance K-Graphite Anode.

Although graphite with its merits of low cost, abundance, and environmental friendliness is a potential anode material for potassium ion batteries (PIBs), it suffers from a limited cycle life due to a severe decomposition of the solid electrolyte interface (SEI) in organic electrolytes. Herein, a simple and viable method is demonstrated for the first time through which an ultra‐thin, uniform, dense, and stable artificial inorganic SEI film can be prepared on commercial graphite anodes and used with traditional carbonate electrolytes to achieve PIBs with long‐cycle stability and high initial Coulombic efficiency (ICE). Specifically, such commercial graphite anodes exhibit a long‐term cycling stability for more than 1000 cycles at 100 mA g−1 (a reversible capacity of around 260 mAh g−1) and a high average CE (around 99.9%) in traditional carbonate electrolytes with no discernable decay in capacity. More importantly, the commercial graphite anodes with the artificial inorganic SEI film in traditional carbonate electrolytes can deliver a high ICE of 93% (the highest ICE ever reported for PIBs anodes until now), which improves the performance of the PIB full cell. Considering the high ICE and long cycle stability performance, this study can promote the rapid deployment of PIBs on a commercial scale.

Synergistic Effects on Lithium Metal Batteries by Preferential Ionic Interactions in Concentrated Bisalt Electrolytes

AbstractLithium metal batteries (LMBs) have the potential to deliver a greater specific capacity than any commercially used lithium battery. However, excessive dendrite growth and low Coulombic efficiencies (CEs) are major hurdles preventing the commercialization of LMBs. In this study, two different salts, lithium difluorophosphate (LiDFP) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), are chosen for use in concentrated electrolytic systems. By mixing salts with vastly different cation–anion interaction energies, the ion solvation structures in the electrolyte can be modulated to enhance the physical/electrochemical properties and suppress Li dendrite growth in LMBs. Among the investigated electrolyte systems, 2.2 m LiDFP + 1.23 m LiTFSI in 1,2‐dimethoxyethane is proposed as a highly promising electrolyte system because of its high conductivity (6.57 mS cm−1), CE (98.3%), and the formation of an extremely stable solid–electrolyte interface layer. The bisalt electrolyte presented herein, as well as the associated concepts, provide a new avenue toward commercial LMBs.

Research progress of fluorine-containing electrolyte additives for lithium ion batteries

The construction of Solid Electrolyte Interface (SEI) film in Li-ion batteries with functional electrolyte additives is able to passivate the active material surface and inhibit the decomposition of the electrolyte continuously. In addition, safety issue is also an important factor restricting the large scale application of present lithium-ion batteries. Therefore, the additives for film-forming and safety enhancement are a class of cost-effective components that promote the application and development of batteries. Fluorine is a kind of “bipolar” element, which has strong electronegativity and weak polarity. Fluorine-containing electrolyte additives have excellent kinetic reactivity, which can preferentially generate stable SEI films and uniform Cathode-Electrolyte Interface (CEI) films to effectively improve the electrochemical performance of the batteries. Meanwhile, fluorine-containing electrolyte additives can also be used as flame-retardants to improve safety performance. In this review, we summarize the research status of fluorine-containing additives in recent years and elaborate its reaction mechanisms of improving battery performance. Finally, a personal perspective on the future of the development of fluorine-containing additives is presented.

Organoboron‐Containing Polymer Electrolytes for High‐Performance Lithium Batteries

AbstractPolymer electrolytes (PEs) have been deemed as a sought‐after candidate for next‐generation lithium batteries. Substantial effort has been dedicated to exploiting PEs with improved comprehensive performance. Organoboron compounds have aroused great interest in PEs due to their distinct characteristics such as high design diversity, excellent thermal stability, promoting lithium‐ion transportation, and raising Li+ transference number. Organoboron compounds also have unique functions that facilitate the development of a stable solid electrolyte interface on the electrode surface. Their diversified structures and multiple functions are fundamentally associated with boron's hybridization form that determines the electronic structure of boron as a central atom. Here, recent advancement in organoboron‐containing PEs is reviewed in the aspect of polymer matrixes with boron moieties and organoboron additives for PEs. This review aims to highlight the diverse roles and high application potentials of organoboron compounds utilized in PEs. It is anticipated to provide a clear perspective of organoboron‐containing PEs and to spur more research interests for the exploration of safe and efficient lithium batteries.

Characteristics and electrochemical performances of silicon/carbon nanofiber/graphene composite films as anode materials for binder-free lithium-ion batteries

We report the interfacial study of a silicon/carbon nanofiber/graphene composite as a potentially high-performance anode for rechargeable lithium-ion batteries (LIBs). Silicon nanoparticle (Si)/carbon nanofiber (CNF)/reduced graphene oxide (rGO) composite films were prepared by simple physical filtration and an environmentally-friendly thermal reduction treatment. The films were used as high-performance anode materials for self-supporting, binder-free LIBs. Reducing graphene oxide improves the electron conductivity and adjusts to the volume change during repeated charge/discharge processes. CNFs can help maintain the structural stability and prevent the peeling off of silicon nanoparticles from the electrodes. When the fabricated Si/CNF/rGO composites were used as anodes of LIBs, the initial specific capacity was measured to be 1894.54 mAh/g at a current density of 0.1 A/g. After 100 cycles, the reversible specific capacity was maintained at 964.68 mAh/g, and the coulombic efficiency could reach 93.8% at the same current density. The Si/CNF/rGO composite electrode exhibited a higher specific capacity and cycle stability than an Si/rGO composite electrode. The Si/CNF/rGO composite films can effectively accommodate and buffer changes in the volume of silicon nanoparticles, form a stable solid–electrolyte interface, improve the conductivity of the electrode, and provide a fast and efficient channel for electron and ion transport.

A new strategic approach to modify electrode and electrolyte for high performance Li–S battery

Lithium-sulfur batteries have been strongly advocated as prominent candidate for the next-generation energy storage device. The shuttling of lithium polysulfide (LiPS) during cycling is inherent problem in these batteries which results in huge capacity fading and impede their practical applications. A simple but effective method is adopted to synthesize polypyrrole coated sulfur nanoparticle which retard the LiPS dissolution in electrolyte. The polypyrrole coated continuous conducting network cathode with nano size (~70 nm) sulfur particle and a stable solid electrolyte interface (SEI) layer protected anode for high performance Li–S battery is demonstrated in this study. Such engineered structure can minimize the fast capacity fading considerably and nano size sulfur makes themselves more accessible to ions and electrons. Strategically, for Li anode protection, LiPS based ternary salt electrolyte (Li2S6, LiNO3 and LiTFSI) is used which form a stable SEI-layer on Li anode during initial cycles. The composite cathode exhibit an initial discharge capacity of 1085 mAh g−1 at 0.2 Ag-1 current density with a low capacity decay of 0.31% per cycles and cycled up to 165 cycles. The post-mortem analysis validates efficient trapping of LiPS in the cathode side and formation of a stable protective SEI layer on Li anode.

Constructing multifunctional solid electrolyte interface via in-situ polymerization for dendrite-free and low N/P ratio lithium metal batteries

Stable solid electrolyte interface (SEI) is highly sought after for lithium metal batteries (LMB) owing to its efficient electrolyte consumption suppression and Li dendrite growth inhibition. However, current design strategies can hardly endow a multifunctional SEI formation due to the non-uniform, low flexible film formation and limited capability to alter Li nucleation/growth orientation, which results in unconstrained dendrite growth and short cycling stability. Herein, we present a novel strategy to employ electrolyte additives containing catechol and acrylic groups to construct a stable multifunctional SEI by in-situ anionic polymerization. This self-smoothing and robust SEI offers multiple sites for Li adsorption and steric repulsion to constrain nucleation/growth process, leading to homogenized Li nanosphere formation. This isotropic nanosphere offers non-preferred Li growth orientation, rendering uniform Li deposition to achieve a dendrite-free anode. Attributed to these superiorities, a remarkable cycling performance can be obtained, i.e., high current density up to 10 mA cm−2, ultra-long cycle life over 8500 hrs operation, high cumulative capacity over 4.25 Ah cm−2 and stable cycling under 60 °C. A prolonged lifespan can also be achieved in Li-S and Li-LiFePO4 cells under lean electrolyte content, low N/P ratio or high temperature conditions. This facile strategy also promotes the practical application of LMB and enlightens the SEI design in related fields.

Ternary Cross-Linked Multi-Functional Blended Polymers for High-Performance Silicon Anodes in Lithium-Ion Batteries

Silicon (Si) based anode material is highly attractive for next-generation lithium‐ion batteries (LIBs) due to its unparalleledtheoretical capacity and abundance. However, a severe problem of Si is the significant volume change associated with thelithiation processes, resulting in reduced capacity retention. Researchers have traditionally considered the roles ofinteractive binders and conductive additives as separate entities. These two components often lead to remarkablydecreased mass ratio of Si to nonactive material, which inevitably limits the electrode capacity. To achieve an enhanceutilization efficiency, herein, we have developed a multifunctional nanocomposite binder for high capacity nano-size Sibasedmaterial through a cross-linked polymer of carboxymethylcellulose (CMC), polyacrylic acid (PAA) spine withgraphenized polyacrylonitrile (PAN) through a gradual carbonizing route. This nanocomposite strongly interacts with Simaterial, providing a robust nanoarchitecture with abundant conductive pathways for Li-ion transport. CMC and PAA with alarge number of carboxyl groups provide binding ability by sturdy three-dimensional (3D) cross-linked network with relativelya thin SiO2 mechanical binding film on the surface of Si nanoparticles onto a highly porous carbon and forming a stablesolid electrolyte interface (SEI) layer. Meanwhile, graphenized PAN provides a highly interconnected conductivenanoarchitecture of a nitrogen-doped graphenized-like structure (NG), which provides enhanced pathways for lithium iondiffusion. Without any conductive additives, this nanocomposite material not only shows a high superior 1st dischargecapacity of 3473 mAh g-1, high initial Coulombic efficiency of 89%, excellent rate capability, and remarkable cycling life formore 600 cycles when cycled at high current density of 3000 mA g-1, but also maintaining good cyclability with a constanthigh areal capacity of ~ 2.7 mAh cm-2. Together with the ease of fabrication, this provides a promising avenue forcommercial LIBs. Figure 1

(Invited) Various Strategies Using Protective Coating Layers for High-Performance Lithium Metal Batteries

Recently, a consensus has been reached that using lithium metal as an anode in rechargeable Li-ion batteries is the best way to obtain the high energy density necessary to power electronic devices. Challenges remain, however, with respect to controlling dendritic Li growth on these electrodes, enhancing compatibility with carbonate-based electrolytes, and forming a stable solid–electrolyte interface layer.Herein, we suggest a groundbreaking solution to these challenges consisting in the preparation of a Li2TiO3 (LT) layer that can be used to cover Li electrodes via a simple and scalable fabrication method. Not only does this LT layer impede direct contact between electrode and electrolyte, thus avoiding side reactions, but it assists and expedites Li-ion flux in batteries, thus suppressing Li dendrite growth. Other effects of the LT layer on electrochemical performance were investigated by scanning electron microscopy, electrochemical impedance spectroscopy, and galvanostatic intermittent titration technique analyses. Notably, LT layer-incorporating Li cells comprising high-capacity/voltage cathodes with reasonably high mass loading (LiNi0.8Co0.1Mn0.1O2, LiNi0.5Mn1.5O4, and LiMn2O4) showed highly stable cycling performance in a carbonate-based electrolyte. Therefore, we believe that our approach based on the LT layer can boost the realization of high energy density lithium metal batteries and next-generation batteries.Furthermore, functional organic protective layers are helpful to suppress the dendritic growth of Li metal. We would like to introduce two different polymer systems including ferroelectric poly(vinylidene fluoride) fiber mats and elastic polymer, poly(styrene-b-butadient-b-styrene) copolymer for this purpose.

Vanadium diphosphide as a negative electrode material for sodium secondary batteries

The abundance of sodium resources has sparked interest in the development of sodium-ion batteries for large-scale energy storage systems, amplifying the need for high-performance negative electrodes. Although transition metal phosphide electrodes have shown remarkable performance and great versatility for both lithium and sodium batteries, their electrochemical mechanisms in sodium batteries, particularly vanadium phosphides, remain largely elusive. Herein, we delineate the performance of VP2 as a negative electrode alongside ionic liquids in sodium-ion batteries. The polycrystalline VP2 is synthesized via one-step high energy ball-milling and characterized using X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. Electrochemical tests ascertained improved performance at intermediate temperatures, where the initial cycle was conducted at 100 mA g−1 yielded a significantly higher discharge capacity of 243 mAh g−1 at 90 °C compared to the limited capacity of 49 mAh g−1 at 25 °C. Enhanced rate and cycle performance are also achieved at 90 °C. Electrochemical impedance spectroscopy and scanning electron microscopy further reveal a reduced charge transfer resistance at 90 °C and the formation of a uniform and stable solid electrolyte interface (SEI) layer after cycling. X-ray diffraction and nuclear magnetic resonance spectroscopy are used to confirm the conversion-based mechanism forming Na3P after charging.

Oriented-Redox Induced Uniform MnO2 Coating on Ni3S2 Nanorod Arrays as a Stable Anode for Enhanced Performances of Lithium Ion Battery.

Cost-effective transition metal chalcogenides have aroused wide consideration as alternative anode materials in lithium ion batteries (LIBs) on account of their elevated lithium activity and considerable theoretical capacity. However, the significant challenge caused by the large volume change and shuttle effect of polysulfides during Li ion insertion/extraction severely restricts their practical application. In this work, the uniform MnO2 coating layer with a tunable thickness on Ni3S2 nanorod arrays has been achieved through a mild oriented-redox reaction by taking advantage of the mixing valence of Ni in Ni3S2 [(Ni2+)2(Ni0)(S2-)2]. The core/shell structured nanorod arrays directly used as anode materials of LIBs demonstrate remarkably improved lithium storage performance including high rate capacity and long cycle life, which deliver a discharge capacity of 662 mA h g-1 for 150 cycles at 0.5 C, corresponding to an elevated capacity retention of 90.7%. The improved electrochemical performances can be assigned to the generation of stable solid electrolyte interface films and suppression of the shuttle behavior with the protection of the MnO2 coating layer on Ni3S2 nanorod arrays.

Insight into pre-sodiation in Na3V2(PO4)2F3/C @ hard carbon full cells for promoting the development of sodium-ion battery

Sodium-ion battery has been put into an eager consideration in the large-scale energy storage system, owing to its inexpensive cost ($/kWh) than that of the lithium-ion battery. The gap from research to industry still exists, however, including low energy density and unsatisfactory cycling lifespan in full cells. Here we report a Na-ion full cell with spray-dried Na3V2(PO4)2F3/C (NVPF/C) cathode and pre-sodiated hard carbon (HC) anode. It is demonstrated that the full cells (NVPF-HC), assembled with 100% presodiated HC anode, exhibits the best energy storage capability and rate performance. A remarkable reversible capacity of 114.1 mA h g−1 at 0.5C (attaining 95% of capacity for NVPF-Na anode half-cell), a desirable power performance with 90.6 mA h g−1 at a high rate of 20C, and an impressive cycling life (71.8% capacity retention after 600 cycles at 10C) are achieved. The outstanding battery performance is ascribed to that the electroactivity Na+ in HC can maximize the scavenger effect and forms the more stable solid-electrolyte interface (SEI). Moreover, an HC pre-sodiation degree dependent Na-ion battery performance is proofed. The findings in this paper offer new insights on the electrode design strategy, which facilitates the development of sodium-ion technology.

Rational Design of Sb@C@TiO2 Triple-Shell Nanoboxes for High-Performance Sodium-Ion Batteries.

Antimony is an attractive anode material for sodium-ion batteries (SIBs) owing to its high theoretical capacity and appropriate sodiation potential. However, its practical application is severely impeded by its poor cycling stability caused by dramatic volumetric variations during sodium uptake and release processes. Here, to circumvent this obstacle, Sb@C@TiO2 triple-shell nanoboxes (TSNBs) are synthesized through a template-engaged galvanic replacement approach. The TSNB structure consists of an inner Sb hollow nanobox protected by a conductive carbon middle shell and a TiO2 -nanosheet-constructed outer shell. This structure offers dual protection to the inner Sb and enough room to accommodate volume expansion, thus promoting the structural integrity of the electrode and the formation of a stable solid-electrolyte interface film. Benefiting from the rational structural design and synergistic effects of Sb, carbon, and TiO2 , the Sb@C@TiO2 electrode exhibits superior rate performance (212 mAh g-1 at 10 A g-1 ) and outstanding long-term cycling stability (193 mAh g-1 at 1 A g-1 after 4000 cycles). Moreover, a full cell assembled with a configuration of Sb@C@TiO2 //Na3 (VOPO4 )2 F displays a high output voltage of 2.8V and a high energy density of 179Wh kg-1 , revealing the great promise of Sb@C@TiO2 TSNBs as the electrode in SIBs.

Bi-Sb Nanocrystals Embedded in Phosphorus as High-Performance Potassium Ion Battery Electrodes.

The development of high-performance potassium ion battery (KIB) electrodes requires a nanoengineering design aimed at optimizing the construction of active material/buffer material nanocomposites. These nanocomposites will alleviate the stress resulting from large volume changes induced by K+ ion insertion/extraction and enhance the electrical and ion conductivity. We report the synthesis of phosphorus-embedded ultrasmall bismuth-antimony nanocrystals (BixSb1-x@P, (0 ≤ x ≤ 1)) for KIB anodes via a facile solution precipitation at room temperature. BixSb1-x@P nanocomposites can enhance potassiation-depotassiation reactions with K+ ions, owing to several attributes. First, by adjusting the feed ratios of the Bi/Sb reactants, the composition of BixSb1-x nanocrystals can be systematically tuned for the best KIB anode performance. Second, extremely small (diameter ≈ 3 nm) BixSb1-x nanocrystals were obtained after cycling and were fixed firmly inside the P matrix. These nanocrystals were effective in buffering the large volume change and preventing the collapse of the electrode. Third, the P matrix served as a good medium for both electron and K+ ion transport to enable rapid charge and discharge processes. Fourth, thin and stable solid electrolyte interface (SEI) layers that formed on the surface of the cycled BixSb1-x@P electrodes resulted in low resistance of the overall battery electrode. Lastly, in situ X-ray diffraction analysis of K+ ion insertion/extraction into/from the BixSb1-x@P electrodes revealed that the potassium storage mechanism involves a simple, direct, and reversible reaction pathway: (Bi, Sb) ↔ K(Bi, Sb) ↔ K3(Bi, Sb). Therefore, electrodes with the optimized composition, i.e., Bi0.5Sb0.5@P, exhibited excellent electrochemical performance (in terms of specific capacity, rate capacities, and cycling stability) as KIB anodes. Bi0.5Sb0.5@P anodes retained specific capacities of 295.4 mA h g-1 at 500 mA g-1 and 339.1 mA h g-1 at 1 A g-1 after 800 and 550 cycles, respectively. Furthermore, a capacity of 258.5 mA h g-1 even at 6.5 A g-1 revealed the outstanding rate capability of the Sb-based KIB anodes. Proof-of-concept KIBs utilizing Bi0.5Sb0.5@P as an anode and PTCDA (perylenetetracarboxylic dianhydride) as a cathode were used to demonstrate the applicability of Bi0.5Sb0.5@P electrodes to full cells. This study shows that BixSb1-x@P nanocomposites are promising carbon-free anode materials for KIB anodes and are readily compatible with the commercial slurry-coating process applied in the battery manufacturing industry.