Full Cell System Research Articles

Investigating the Catalyst/Ionomer Interface in PEM Water Electrolysis Using Microelectrodes

Low temperature zero-gap PEM water electrolyzers are promising devices which are still in development. Water electrolyzers have the potential to be a critical part of the energy transition as a method to use renewable electricity to produce hydrogen which can feed into the hydrogen economy. When paired with renewable sources of electricity, electrolyzers will be subjected to variable power loads, which places a large stress on the systems. This stress causes increased degradation of many components, including the catalyst layers. It can be challenging to study the impact of degradation of the catalyst layer in an electrolysis cell, due to the many coupled degradation phenomenon occurring in the full cell system. Microelectrodes can be used to investigate the catalyst layer under electrolysis operating conditions, but in a simplified system which can more easily isolate the catalyst layer and kinetics. One of the limiting factors in water electrolyzer performance is the oxygen evolution reaction (OER) due to the sluggish kinetics. If the OER kinetics could be improved, it would greatly reduce the cost of the electrolyzer system. The ionomer forms a thin film in the catalyst layer, and controls the local conditions surrounding the catalyst. The local conditions and interactions of the ionomer with the active catalyst sites still aren't well understood, as well as the contribution of the ionomer to catalyst degradation. In this study, cavity microelectrodes will be used to investigate the impact of ionomer on IrOx catalyst OER performance and durability.

Ultrathin carbon film as ultrafast rechargeable cathode for hybrid sodium dual-ion capacitor

The development of electrochemical energy storage devices has a decisive impact on clean renewable energy. Herein, novel ultrafast rechargeable hybrid sodium dual-ion capacitors (HSDICs) were designed by using ultrathin carbon film (UCF) as the cathode material. The UCF is synthesized by a simple low temperature catalytic route followed by an acid leaching process. UCF owns a large adsorption interface and number of additional active sites, which is due to the nitrogen doping. In addition, there exists several short-range order carbons on the surface of UCF, which are beneficial for anionic storage. An ultrafast rechargeable remarkable performance, remarkable anion hybrid storage capability and outstanding structure stability is fully tapped employing UCF as cathode for HSDICs. The electrochemical performance of UCF in a half-cell system at the operating voltage between 1.0 and 4.8 V, achieving an admirable specific discharge capacity of 358.52 mAh·g−1 at 500 mA·g−1, and a high capacity retention ratio of 98.42% after cycling 2500 times at 1000 mA·g−1, respectively. Besides, with the support of ex-situ TEM and EDS mapping, the structural stability principle and anionic hybrid storage mechanism of UCF electrode are investigated in depth. In the full-cell system, HSDICs with the UCF as cathode and hard carbon as anode also presents a super-long cycle stability (80.62% capacity retention ratio after cycling 1300 times at 1000 mA·g−1).

Lamellar sulfonated acid polymer-initiated in situ construction of robust LiF-rich SEI enabling superior charge transport for ultrastable and fast charging silicon anodes

The extreme volume expansion of the silicon (Si) anodes during repeated cycles seriously induces undesirable interfacial side reactions, forming an unstable solid electrolyte interphase (SEI) that degrades the electrode integrity and cycle stability in lithium-ion batteries, limiting their practical applications. Despite considerable efforts to stabilize the SEI through surface modification, challenges persist in the development of high-performance Si anodes that effectively regulate intrinsic SEI properties and simultaneously facilitate electron/ion transport. Here, a highly conductive and organic electrolyte-compatible lamellar p-toluenesulfonic acid-doped polyaniline (pTAP) layer is proposed for constructing a robust artificial SEI on Si nanoparticles to achieve fast charging, long-term cycle lifespan and high areal capacity. The spatially uniform pTAP layer, formed through a facile direct-encapsulation approach assisted by enriched hydrogen bonding, contributes to the effective formation of in situ SEI with an even distribution of the LiF-rich phase in its interlamination spaces. Furthermore, the integrated artificial SEI facilitates isotropic ion/electron transport, increased robustness, and effectively dissipates stress from volume changes. Consequently, a notably high rate performance of 570 mA h g−1, even at a substantially high current density of 10 A g−1, is achieved with excellent cyclic stability by showing a superior capacity over 1430 mA h g−1 at 1 A g−1 after 250 cycles and a high areal capacity of ca. 2 mA h cm−2 at 0.5 C in a full cell system. This study demonstrates that the rational design of conductive polymers with SEI modulation for surface protection has great potential for use in high-energy-density Si anodes.

Regulating sodium deposition by specific surface area composite ratio for anode-free Na metal batteries

Anode-free sodium metal batteries (AFSMBs) have greater potential to be one of the electrochemical storage technology choices for high energy density. However, the anode-free current collector is more likely to grow dendrites than the metal anode. Here we report a transformative structural combination strategy to build an anode-free current collector with an ultraconformal structure between the conducting network and metallic sodium deposition space in anode-free metal batteries. The reversibility of the sodium plating/stripping process is significantly enhanced using this strategy, achieving stable operation for more than 2100 cycles at current density (1 mA cm−2) with 1 mA h cm−2 while maintaining an average coulombic efficiency of 99.5 %. The Na-diffused ZnIn2S4 current collector delivers an excellent maximum current density of 10 mA cm−2. In addition, optimization of the structure in the ZnIn2S4||Na3V2(PO4)3 full cell system leads to the successful realization of high-energy-density anode-free sodium cells. These cells exhibit excellent cycling stability under high-rate discharge conditions (5 C), with a capacity retention rate of 91 % after more than 500 cycles. The study presents a promising strategy for constructing an ultraconformal structural framework for high-performance AFSMBs.

High Safety Electrolyte Design for Enabling High Energy-Density System of LiNi0.8Co0.1Mn0.1O2//Phosphorus by Simultaneously Adjusting Dual Electrode/Electrolyte Interfaces.

The demand for state-of-the-art high-energy-density lithium-ion batteries is increasing. However, the low specific capacity of electrode materials in conventional full-cell systems cannot meet the requirements. Ni-rich layered oxide cathodes such as Li(Ni0.8Co0.1Mn0.1)O2 (NCM811) have a high theoretical specific capacity of 200 mAh g-1, but it is always accompanied by side reactions on the electrode/electrolyte interface. Phosphorus anode possesses a high theoretical specific capacity of 2596 mAh g-1, but it has a huge volume expansion (≈300%). Herein, a highly compatible and secure electrolyte is reported via introducing an additive with a narrow electrochemical window, Lithium difluoro(oxalato)borate (LiDFOB), into 1m LiPF6 EC/DMC with tris (2,2,2-trifluoroethyl) phosphate (TFEP) as a cosolvent. LiDFOB participates in the formation of organic/inorganic hybrid electrode/electrolyte interface layers at both the cathode and anode sides. The side reactions on the surface of the NCM811 cathode and the volume expansion of the phosphorus anode are effectively alleviated. The NCM811//RP full cell in this electrolyte shows high capacity retention of 82% after 150 cycles at a 0.5C rate. Meanwhile, the electrolyte shows non-flammability. This work highlights the importance of manipulating the electrode/electrolyte interface layers for the design of lithium-ion batteries with high energy density.

Enhancing Electrochemical Stability of Silicon-Carbon and NMC based Lithium-Ion Batteries through the Synergistic Impact of Charge Balance and Direct-Contact Pre-Lithiation Strategy

The commercial feasibility of silicon (Si) anodes (≥ 30%) in full-cell systems is constrained by poor cyclic stability and capacity balancing due to continuous active lithium (Li) consumption in each cycle. We proposed a capacity balancing approach by adding additional Li at the cathode side (i.e., ratio of capacity at negative to positive electrode (N/P) ∼ 0.9) and anode side (i.e., pre-lithiated Si) before full-cell fabrication. This approach provided a capacity-balanced full-cell with 91.7% of initial Coulombic efficiency (ICE) and stability up to 50 cycles. In-situ electrochemical impedance spectroscopy (EIS) and distribution of relaxation times (DRT) analysis have been utilized to examine the interface of bare and balanced full cells. In a large format cell, electrolyte wettability is an issue and it has been investigated even at high temperature (50 °C). The post-cycle investigation also indicates the Si particles retained their integrity after cycling. A 110 mAh pouch cell has been constructed, and the pouch cell demonstrated exceptional cyclic stability up to 200 cycles, with a capacity retention of 83.2% at a current rate of 0.1 C. These findings present a capacity balancing approach for high-loading silicon-based anodes that eventually can scale up to high-quality and long-cycle life lithium-ion batteries.

Low-coordination Nanocrystalline Copper-based Catalysts through Theory-guided Electrochemical Restructuring for Selective CO2 Reduction to Ethylene.

Revealing the dynamic reconstruction process and tailoring advanced copper (Cu) catalysts is of paramount significance for promoting the conversion of CO2 into ethylene (C2H4), paving the way for carbon neutralization and facilitating renewable energy storage. In this study, we initially employed density functional theory (DFT) and molecular dynamics (MD) simulations to elucidate the restructuring behavior of a catalyst under electrochemical conditions and delineated its restructuring patterns. Leveraging insights into this restructuring behavior, we devised an efficient, low-coordination copper-based catalyst. The resulting synthesized catalyst demonstrated an impressive Faradaic efficiency (FE) exceeding 70 % for ethylene generation at a current density of 800 mA cm-2. Furthermore, it showed robust stability, maintaining consistent performance for 230 hours at a cell voltage of 3.5 V in a full-cell system. Our research not only deepens the understanding of the active sites involved in designing efficient carbon dioxide reduction reaction (CO2RR) catalysts but also advances CO2 electrolysis technologies for industrial application.

MOF-derived cobalt nanoparticles in silicon suboxide-based anodes for enhanced lithium storage

The ultra-high theoretical capacity of silicon-based (Si) materials makes them promising anode materials for high energy density lithium-ion batteries. Unfortunately, the dramatic volume change (∼300%) and low electrical conductivity of silicon have severely hindered the commercial use of silicon anodes. Silicon suboxide (SiOx) is one of the ideal candidates for high energy density batteries due to its reduced swelling and lower cost as compared to silicon. However, it remains a huge challenge to address the low conductivity, low (initial) coulombic efficiency and apparent volume effects of SiOx. In this paper, SiOx/Co@C composite anode materials loaded with metal Co nanoparticles were uniformly and efficiently prepared by using 3-aminopropyl triethoxysilane (APTES) as silicon source and Co-MOF as Co source via molecular self-assembly strategy. The experimental results and density functional theory (DFT) calculation showed that the catalytic action of embedded Co nanoparticles had activated the silico-oxygen bond of SiOx and the irreversible product Li2O, thereby improving the initial coulombic efficiency (ICE) and enhancing the reversible capacity. At the same time, the metal Co with mechanical rigidity and electrical conductivity alleviated the volume fluctuation during alloying and improved the charge transfer capacity and ion transport rate of the composite. When compared with SiOx@C anodes, SiOx/Co@C-600 composites showed higher initial CE, superior cyclic stability and good rate performance. In particular, the successful matching of the anode with the lithium iron phosphate (LFP) cathode in full cell systems validated the possibility of its practical application. This work provides important insights into the application of Si-based materials in lithium-ion battery electrode materials and the development of high energy density batteries.

Constructing a rapid ion-transport anode interface protective layer for zinc ion batteries to suppress solvation and improve surface electronic structure

Rechargeable Aqueous Zinc-Ion Batteries (AZIBs) have attracted significant attention in recent years due to their high energy density, safety, and cost-effectiveness. However, despite these advantages, AZIBs face challenges such as anode side reactions, passivation, corrosion, hydrogen evolution, and the growth of zinc dendrites, which hinder their widespread use. To address these issues, this study involves the creation of a zinc-affinitive coating using a WSe2/ZIF composite on zinc foils. The amorphous WSe2 protective layer, formed through electrochemical induction as ZnSe, enhances the anode's zinc affinity, accelerates Zn2+ transfer at the interface, and effectively inhibits zinc dendrite growth. Additionally, the coating improves electrolyte wettability, reducing interface resistance. Compared to pure zinc, anodes with a WSe2/ZIF protective layer exhibit excellent performance in both symmetric cells and full-cell systems using MXene/MnO2 as the cathode. Symmetric cells can cycle for over 1000 h at a current density of 5 mA/cm2, and the full cell maintains a capacity retention of 91.4 % after 2000 charge-discharge cycles. This interface engineering strategy, supported by density functional theory calculations, provides a strong foundation for practical applications.

Bi2Se3@SWCNT heterostructures with beyond theoretical capacity as perspective binder-free anodes for lithium-ion batteries

Bi2Se3 has shown potential for implementation as an anode material for lithium-ion batteries (LIBs), however, the significant volume expansion and dissolution of selenium pose major challenges. In this work, Bi2Se3 nanostructures are synthesized by physical vapor deposition directly on top of a single-wall carbon nanotube (SWCNT) network to fabricate a binder-free Bi2Se3@SWCNT anode materials with different Bi2Se3/SWCNT ratios. Nanostructuring the Bi2Se3 directly on the top of the SWCNT network provides a large accessible contact area and improves mechanical and electrical contact. The heterostructures exhibit capacity, that is beyond the theoretical of pristine Bi2Se3, which can be attributed to the binding of the Se to C, resulting in the resilience against the dissolution of Se, while providing additional electron transport pathways and increased capacitive contribution. A Bi2Se3@SWCNT anode with a mass ratio of (1:1) has the highest capacity in a half-cell after 100 cycles (523 mAh g−1 at 0.1 A g−1) and shows excellent capacity retention after 500 cycles at large current densities (2 A g−1 and 5 A g−1): 1080 mAh g−1 and 809 mAh g−1 respectively. In addition, in a full-cell system Bi2Se3@SWCNT (1:1) delivers high reversible capacity after 150 cycles (484 mAh g−1) at 0.4 A g−1.

Designing functional Li2CuO2-coated separators from Cu foil towards spent LiFePO4 cathode regeneration.

A chemical-physical investigation proved that the loss of active Li represents the main mechanism of capacity-fading in spent LiFePO4. Given this, functional Li2CuO2-coated separators were fabricated from spent Cu foil and found to contribute to the regeneration of spent LiFePO4 in a full-cell system. This study presents a novel method for cathode/Cu foil recovery.

Niobate Anodes for High Rate Lithium-Ion Batteries

Fast charging is one of the key performance requirements for next generation lithium ion batteries, and is directly related to the ease of ionic and electronic transport. However, lithium ion diffusion rates of promising anode materials, such as Li4Ti5O12, anatase TiO2, T-Nb2O5 and Nb18W16O93, are still insufficient. Therefore, nanosizing of the active electrode material is a common strategy to increase the effective lithium ion diffusion transport rate, which unfortunately also decreases the volumetric energy/power density and stability of the battery.Recently, we demonstrated nickel niobate, NiNb2O6, for the first time as a new intrinsic high-rate electrode material,[1] which exhibits an intrinsic high rate performance enabled by its suitable host crystal structure without the requirement of realizing nano-architectures. The NiNb2O6 host crystal structure exhibits only a single type of channel for lithium ion intercalation and can be fully lithiated up to Li3NiNb2O6 with a capacity of about 244 mAh/g at low current densities. Interestingly, a high diffusion coefficient of 10-12 cm2/s at 300 K enables fast (dis)charging at high current densities resulting in high capacities of 140 and 50 mAh/g for respectively 10C and 100C. The minimal volume change during lithiation is the origin of the stable reversible lithiation process in NiNb2O6 and leads to a capacity retention of 81% after 20.000 cycles at 100C. The structural stability and electrochemical behaviour were investigated by various experimental techniques and confirmed by density functional theory (DFT) calculations. Finally, full cell systems against LiFePO4 and NCM811 cathodes demonstrate the promising energy storage performance of nickel niobate anodes in practical battery devices.Our results strongly suggest that niobate-based materials are intrinsic high-rate anode materials without the requirement of realizing nano-architectures as typical for numerous titanium- and niobium-based oxides through complex synthesis procedures to minimize the length scales for lithium diffusion. Recently, we have replaced nickel by other transition metal ions to widen the exploration of niobate compounds for fast lithium ion diffusion. Large variations in electrochemical performance are observed, and the latest results will be presented. This will provide a new perspective on the role of intrinsic high-rate electrode materials for realizing ultrafast anode materials for future energy storage devices.[1] R. Xia et al., Advanced Energy Materials 12 (2022) 2102972.

Increasing the Sodium Content in P2-Type Layered Oxides As Cathode Materials for Sodium-Ion Batteries

P2-type layered oxides exhibit superior Na ion conductivity and structural stability compared to their O3 analogues, making them promising candidate materials for next generation batteries. However, their lower initial Na contents (Na/transition metals < 1) restrict their capacity during the first charge process, and the transitions between P- and O2-type structures during cycling further deteriorate their stability.[1,2] Our work aims to increase the Na inventory in pristine cathode compositions, especially relevant for full cell systems, while maintaining their cycling stability. We started with the well-studied P2 material Na2/3Ni1/3Mn2/3O2 and have worked on incorporating Li in the transition metal layers to stabilize the structure, while at the same time increasing the Na content.[3,4] In this respect, a great challenge is to control the phase formation during the synthesis. When the Na content exceeds a certain limit, an O3 structure is more likely to form than a P2 structure.[1] On the other hand, at too low temperatures, a P3 polymorph is preferred.[5] By regulating the synthesis conditions, Na contents have been successfully increased in a series of materials between two end compositions, Na2/3Ni1/3Mn2/3O2 and Na5/6Li5/18Mn13/18O2.In this presentation, we report on unpublished in situ XRD characterizationsof these compositions during their solid-state synthesis, as well as on their crystal structures and electrochemical behavior, which involves varying amount of Ni redox. These time-resolved studies of structural evolutions provide guidance for further synthesis of desired phases and compositions. Along with the electrochemical results, we also aim to answer the questions on the charge compensation mechanisms that sustain the electrochemical performance as the amount of Li increases and Ni decreases. Finally, we also explore which amount of Li substitution can best balance the structural stability and capacity retention of the cathode material.

Full‐Cell Presodiation Strategy to Enable High‐Performance Na‐Ion Batteries

AbstractAs promising alternatives to lithium‐ion batteries, sodium‐ion batteries suffer from low coulombic efficiency, which stems from Na‐deficiency and unstable interfaces for both cathode and anode materials. Exhibiting a favorable solvation structure, Na‐naphthalene/tetrahydropyran (Na‐NP/THP) is screened and selected as a full‐cell presodiation solution for hard carbon (HC) anodes and a P‐2 type Na0.67Fe0.1Al0.1Mn0.8O2 (NFAM) cathode, which are both Na‐deficient. Through a wealth of characterizations, it is revealed that the proposed presodiation agent not only boosts the initial coulombic efficiency of both HC and NFAM electrodes effectively, but also facilitates robust solid–electrolyte interphase (SEI) and cathode–electrolyte interphase (CEI) on both electrodes. Consequently, the long‐term cycling and rate performance are greatly improved thanks to the stabilized structures of electrode materials. Furthermore, a proof‐of‐concept NFAM||HC pouch cell based on this presodiation strategy is assembled, showing a high reversible capacity and superior cycling performance. By offering a remedy to a full cell system subjected to severe Na‐deficiency, this work conceptually demonstrates a feasible strategy to fully tap the potential of high‐energy‐density materials in sodium‐ion batteries.

Multifunctional Additive Ethoxy(pentafluoro)cyclotriphosphazene Enables Safe Carbonate Electrolyte for SiOx‐Graphite/NMC811 Batteries

AbstractThe silicon (Si) or silicon monoxide (SiOx)‐graphite (Gr)/nickel‐rich LiNixMnyCozO2 (NMC, x+y+z=1, with x≥80 %) cell chemistry is currently regarded as a promising candidate to further improve the energy density of rechargeable lithium‐ion batteries, but is confronted with safety and cycling stability issues. Here, the flame retardant ethoxy(pentafluoro)cyclotriphosphazene (PFPN) is studied as electrolyte additive in the SiOx‐Gr/NMC811 full cell system. We find that PFPN in combination with an increased lithium hexafluorophosphate (LiPF6) concentration renders carbonate‐based electrolytes non‐flammable based on a very low self‐extinguishing time of 3.1 s g−1 while the electrolyte maintains a high ionic conductivity of 8.4 mS cm−1 at 25 °C. Importantly, PFPN in combination with fluoroethylene carbonate (FEC) also stabilizes the solid‐electrolyte interphase of Si‐based anodes beyond the level achieved only with FEC. Furthermore, PFPN improves the wetting property of the electrolyte, rendering it a multifunctional additive. As a result, excellent capacity retention of 87 % after 200 cycles at 1 C was achieved for SiOx‐Gr/NMC811 pouch cells with a relatively high SiOx content of 20 %. Our work provides a promising avenue for developing safe and high‐performance electrolytes for lithium‐ion batteries with silicon‐based anodes.

Bi/Bi3Se4 nanoparticles embedded in hollow porous carbon nanorod: High rate capability material for potassium-ion batteries

Considering their superior theoretical capacity and low voltage plateau, bismuth (Bi)-based materials are being widely explored for application in potassium-ion batteries (PIBs). Unfortunately, pure Bi and Bi-based compounds suffer from severe electrochemical polarization, agglomeration, and dramatic volume fluctuations. To develop an advanced bismuth-based anode material with high reactivity and durability, in this work, the pyrolysis of Bi-based metal–organic frameworks and in-situ selenization techniques have been successfully used to produce a Bi-based composite with high capacity and unique structure, in which Bi/Bi3Se4 nanoparticles are encapsulated in carbon nanorods (Bi/Bi3Se4@CNR). Applied as the anode material of PIBs, the Bi/Bi3Se4@CNR displays fast potassium storage capability with 307.5 mA h g−1 at 20 A g−1 and durable cycle performance of 2000 cycles at 5 A g−1. Notably, the Bi/Bi3Se4@CNR also showed long cycle stability over 1600 cycles when working in a full cell system with potassium vanadate as the cathode material, which further demonstrates its promising potential in the field of PIBs. Additionally, the dual potassium storage mechanism of the Bi/Bi3Se4@CNR based on conversion and alloying reaction has also been revealed by in-situ X-ray diffraction.

Recycle waste washcloth to design Fe3O4/FeS2/C heterojunction membrane as high-area capacity freestanding anode for sodium-ion batteries

Rechargeable sodium-ion batteries (SIBs) with high-area specific capacity and low cost have attracted increasing attention for large-scale energy storage. In this work, Fe3O4/FeS2 heterojunction encapsulated in carbon membrane (FOSM) was rationally designed as freestanding anode for SIBs by taking the waste washcloth as the carbon supporter following calcined at 650 °C (FOSM-650). The porous carbon fiber skeleton inner could support the outer Fe3O4/FeS2 heterojunction to cast excellent flexibility, providing a bridge for fast electron transfer and relieving volume expansion during the charging/discharging process. Meanwhile, the direct contact of outer Fe3O4/FeS2 particles with electrolyte shortened the diffusion path of Na+, and the Fe3O4/FeS2 heterojunction can also foster fast electron diffusion at the interface. Therefore, as a freestanding anode of SIBs, the FOSM-650 electrode exhibited a specific capacity of 1.25 mAh cm−2 at 0.5 A cm−2 in a half-cell system, 0.5 mAh cm−2 was achieved even at a high current density of 2 A cm−2, and still 0.47 mAh cm−2 was retained after 1000 cycles. Especially, in a FOSM-650//NVP@C full-cell system, the specific capacity was stabilized at 0.58 mAh cm−2 after 10 cycles at a current density of 2 A cm−2, 0.21 mAh cm−2 was still achieved after 1000 cycles. This work not only promotes the development of Fe-based freestanding materials with high area-specific capacity, excellent cycling stability and rate capability, and high energy density for SIBs but also provides an effective and high added-value approach for recycling the waste washcloth for forest protection.

Nanostructured Manganese Dioxide for Hybrid Supercapacitor Electrodes

Hybrid supercapacitors, as emerging energy storage devices, have gained much attention in recent years due to their high energy density, fast charge/discharge and long cyclabilities. Among the wide range of systems covered by this topic, low cost, environmental friendliness and high power provide MnO2 with great characteristics to be a competitive candidate. The present work reports a hybrid aqueous supercapacitor system using a commercial activated carbon as the negative electrode and a synthesized manganese dioxide as the positive electrode. Two manganese dioxide polymorphs (α-MnO2 and δ-MnO2) were tested in different neutral and basic aqueous electrolytes. In this way, full cell systems that reached an energy density of 15.6 Wh kg−1 at a power density of 1 kW kg−1 were achieved. The electrode–electrolyte combination explored in this study exhibits excellent performance without losing capacity after 5000 charge/discharge cycles, leading to a promising approach towards more sustainable, high-performance energy storage systems.

Zinc atoms introduction alloying to the artificial interface protection layer for ultra-stable LiB alloy anodes

The lithium-boron (LiB) alloy has more excellent electrochemical performance and more practical applied prospects than pure Li as anode due to its three-dimensional skeleton with a low mass burden. Nevertheless, its rectification ability of Li ions (Li+) flux remains to be further improved. Herein, a low-cost and convenient solution immersion strategy focusing on LiB alloy is developed to obtain lithium-boron-zinc (LiBZn) alloy. The lithium-zinc (LiZn) alloy can make up for the insufficiency of LiB alloy from the point of unifying Li+ flux. The experimental and theoretical simulations prove that the LiZn alloy protection layer can guide homogeneous Li+ distribution and regulate Li deposition on the interface to inhibit dendrite growth effectively. Specifically, the pre-prepared LiBZn can cycle stably for 1800 h with a minimum overpotential of 14 mV at 1 mA cm−2 and 1 mAh cm−2, exhibiting relatively low overpotential and stability in the rate performance (the maximum current density up to 5 mA cm−2), and the enhanced cyclability in the full cell system paired with NCM811 demonstrates its practical application effect. This facile and controllable strategy illuminates a more applicatory technical path for Li metal-based alloy anodes.

Pseudocapacitance-Enhanced Storage Kinetics of 3D Anhydrous Iron (III) Fluoride as a Cathode for Li/Na-Ion Batteries.

Transition metal fluoride (TMF) conversion cathodes, with high energy density, are recognized as promising candidates for next-generation high-energy Li/Na-ion batteries (LIBs/SIBs). Unfortunately, the poor electronic conductivity and detrimental active material dissolution of TMFs seriously limit the performance of TMF-LIBs/SIBs. A variety of FeF3-based composites are designed to improve their electrochemical characteristics. However, the storage mechanism of the conversion-type cathode for Li+ and Na+ co-storage is still unclear. Here, the storage mechanism of honeycomb iron (III) fluoride and carbon (FeF3@C) as a general cathode for LIBs/SIBs is analyzed by kinetics. In addition, the FeF3@C cathode shows high electrochemical performance in a full-cell system. The results show that the honeycomb FeF3@C shows excellent long-term cycle stability in LIBs (208.3 mA h g-1 at 1.0 C after 100 cycles with a capacity retention of 98.1%). As a cathode of SIBs, the rate performance is unexpectedly stable. The kinetic analysis reveals that the FeF3@C cathode exhibit distinct ion-dependent charge storage mechanisms and exceptional long-durability cyclic performance in the storage of Li+/Na+, benefiting from the synergistic contribution of pseudocapacitive and reversible redox behavior. The work deepens the understanding of the conversion-type cathode in Li+/Na+ storage.