Uniform Li-ion Research Articles

Lithiophilic Protective Dual Layer Enabling Stable Electrodeposition of Lithium at High Current Density

Lithium (Li) is an ideal anode material for rechargeable batteries and thus manufacturing Li metal is crucial for the practical development of Li metal batteries. Electrodeposition is an efficient technique for producing ultrathin and scalable Li metal electrodes. However, the dendritic growth and the side reactions of Li with electrolyte during the electrodeposition are the main obstacles to overcome. In this study, we designed a pre-coated protective dual layer (PDL) composed of a poly(ethylene oxide)-based solid polymer electrolyte (SPE) and a polydopamine-coated cellulose membrane (PD-CM). The adhesive and ion-conductive SPE layer suppressed the growth of Li dendrites and side reactions with liquid electrolyte. The PD-CM layer with high porosity and lithiophilicity promoted a facile and uniform Li-ion flux. By applying the pre-coated PDL, Li was uniformly electrodeposited on the Ag-coated Cu at a high current density of 6 mA cm−2. The Li/LiFePO4 cell composed of an electrodeposited Li anode with PDL and a LiFePO4 cathode was assembled without an additional separator, and its cycling performance was evaluated. The cell initially delivered a high discharge capacity of 154.8 mAh g−1 at 45 °C and exhibited excellent cycling stability with a capacity retention of 97.0% after 200 cycles.

Surface fluorination of nickel nanowires enabling LiF-rich nanoscale solid electrolyte interface for stable lithium anodes

Lithium (Li) metal has become a research hotspot for anodes materials due to its ultra-high theoretical capacity and the lowest redox potential. However, the practical application of Li metal batteries is hampered by the formation of uncontrollable Li dendrites and the irreversible structural changes during long-term charge/discharge processes. Developing stable Li metal anode with uniform Li deposition is highly desirable. Herein, surface fluorination of nickel nanowires enabling LiF-rich nanoscale solid electrolyte interface was demonstrated for stable Li anodes. Free-standing three-dimensional (3D) nickel nanowires (NiNWs) current collector decorated with lithiophilic NiF2 nanosheets (NiNWs@NiF2) was constructed via a simple and scalable fluorination strategy. Theoretical and experimental analysis confirmed that the lithiophilic surface of NiF2 nanosheets could reduce the Li nucleation barrier, facilitating uniform Li ion deposition. The 3D conductive NiNWs network enabled fast electron transfer and mitigated volume changes during cycling. Additionally, a LiF-rich nanoscale solid electrolyte interface (SEI) layer formed between Li and the electrolyte significantly improved the interfacial stability. As a result, the as-assembled Li-NiNWs@NiF2 symmetrical cell provided a superior electrochemical performance, maintaining stability for 2500 h at 1.0 mA cm−2 and 900 h at 5.0 mA cm−2. Furthermore, the assembled Li-NiNWs@NiF2|| LiFePO4 (LFP) full cell demonstrated exceptional capacity retention of 93.9 % after 2000 cycles at a rate of 5C. Overall, the unique structure of NiNWs@NiF2 not only offers a straightforward method for designing a 3D lithiophilic host, but also provides the concept of interfacial engineering through the in-situ construction of an artificial LiF-rich nanoscale SEI layer.

Lithiophilic Multichannel Layer to Simultaneously Control the Li-Ion Flux and Li Nucleation for Stable Lithium Metal Batteries.

Although the Li metal has been gaining attention as a promising anode material for the next-generation high-energy-density rechargeable batteries owing to its high theoretical specific capacity (3860 mAh g-1), its practical use remains challenging owing to inherent issues related to Li nucleation and growth. This paper reports the fabrication of a lithiophilic multichannel layer (LML) that enables the simultaneous control of Li nucleation and growth in Li-metal batteries. The LML, composed of lithiophilic ceramic composite nanoparticles (Ag-plated Al2O3 particles), is fabricated using the electroless plating method. This LML provides numerous channels for a uniform Li-ion diffusion on a nonwoven separator. Furthermore, the lithiophilic Ag on the Li metal anode surface facing the LML induces a low overpotential during Li nucleation, resulting in a dense Li deposition. The LML enables the LiNi0.8Co0.1Mn0.1O2|| Li cells to maintain a capacity higher than 75% after 100 cycles, even at high charge/discharge rates of 5.0 C at a cutoff voltage of 4.4 V, and achieve an ultrahigh energy density of 1164 Wh kg-1. These results demonstrate that the LML is a promising solution enabling the application of Li metal as an anode material in the next-generation Li-ion batteries.

Dynamic physical network constructed by tripartite H-bonds in artificial SEI to shape ultra-long life dendrite-free lithium-metal anodes

Constructing artificial solid electrolyte interfaces (SEIs) to shape dendrite-free lithium (Li)-metal anodes remains challenges. Herein, we designed dynamic physical network (DPN) with abundant lithiophilic/anionphilic groups through tripartite hydrogen bonds (H-bonds), serving as artificial SEIs in high-loading NCM811-Li metal batteries. The formation and dissociation of DPN endowed by tripartite H-bonds under tension release during Li plating/stripping cycling skillfully balance the contradiction between mechanical robustness and deformability. LiO bonds between lithiophilic sites and Li ions, and extra H-bonds between hydroxyl and electrolyte anions, endow DPN with functions of homogenizing Li-ion flux and accelerating its desolvation, synergistically achieving the uniform Li-ion deposition and weakening the charge shielding. The artificial SEI enhanced Li-anode (DPN@Li) withstood repeated Li ions plating/stripping processes for over 1000 h, which is 5 times longer than pure Li-anodes, and maintained low overpotential at a high current density of 10 mA cm−2. DPN@Li-based NCM811 full cells deliver high specific capacities and outstanding cycle life over 3000 cycles. Further, DPN@Li possesses excellent electrochemical performance in the high active material loading (7.84 mg cm−2) and foldable pouch cells. This work provides a conceptual framework of DPN constructed by multiple weak intermolecular interaction for artificial SEI to shape anode performance, and achieves the idea with a facile manner and simple chemical substances to promote practical applications of LMBs.

A Star-StructuredPolymer Electrolyte for Low-Temperature Solid-State Lithium Batteries.

Solid-state polymer lithium metal batteries (SSLMBs) have attracted considerable attention because of their excellent safety and high energy density. However, the application of SSLMBs is significantly impeded by uneven Li deposition at the interface between solid-state electrolytes and lithium metal anode, especially at a low temperature. Herein, this issue is addressed by designing an agarose-based solid polymer electrolyte containing branched structure. The star-structured polymer is synthesized by grafting poly (ethylene glycol) monomethyl-ether methacrylate and lithium 2-acrylamido-2-methylpropanesulfonate onto tannic acid. The star structure regulates Li-ion flux in the bulk of the electrolyte and at the electrolyte/electrodeinterfaces. This unique omnidirectional Li-ion transportation effectively improves ionic conductivity, facilitates a uniform Li-ion flux, inhibits Li dendrite growth, and alleviates polarization. As a result, a solid-state LiFePO4||Li battery with the electrolyte exhibits outstanding cyclability with a specific capacity of 134 mAh g-1 at 0.5C after 800 cycles. The battery shows a high discharge capacity of 145 mAh g-1 at 0.1 C after 200 cycles, even at 0°C. The study offers a promising strategy to address the uneven Li deposition at the solid-state electrolyte/electrode interface, which has potential applications in long-life solid-state lithium metal batteries at a low temperature.

Regulating Metal Centers of MOF-74 Promotes PEO-Based Electrolytes for All-Solid-State Lithium-Metal Batteries.

Poly(ethylene oxide) (PEO)-based electrolytes have been extensively studied for all-solid-state lithium-metal batteries due to their excellent film-forming capabilities and low cost. However, the limited ionic conductivity and poor mechanical strength of the PEO-based electrolytes cannot prevent the growth of undesirable lithium dendrites, leading to the failure of batteries. Metal-organic frameworks (MOFs) are functional materials with a periodic porous structure that can improve the electrochemical performance of PEO-based electrolytes. However, the enhancement effect of MOFs with different metal centers and the interaction mechanism with PEO remain unclear. Herein, MOF-74s with Cu or Ni centers are prepared and used as fillers of PEO-based electrolytes. Adding 15 wt % of Cu-MOF-74 to the PEO-based electrolyte (15%Cu-MOF/P-Li) effectively improves the ionic conductivity, lithium transference number, and mechanical strength of the PEO-based electrolyte simultaneously. Furthermore, the ordered pore channels of Cu-MOF-74 provide uniform Li-ion transport pathways, facilitating homogeneous Li+ deposition. As a result, the lithium symmetric cell with 15%Cu-MOF/P-Li shows stable cycles for 1080 h at 0.1 mA cm-2 and 0.1 mAh cm-2, and the Li | 15% Cu-MOF/P-Li | LFP full cell exhibits a long cycle life up to 200 cycles at 60 °C and 0.5 C, with a capacity retention rate of 89.7%.

Recent Progress of Advanced Functional Separators in Lithium Metal Batteries.

As a representative in the post-lithium-ion batteries (LIBs) landscape, lithium metal batteries (LMBs) exhibit high-energy densities but suffer from low coulombic efficiencies and short cycling lifetimes due to dendrite formation and complex side reactions. Separator modification holds the most promise in overcoming these challenges because it utilizes the original elements of LMBs. In this review, separators designed to address critical issues in LMBs that are fatal to their destiny according to the target electrodes are focused on. On the lithium anode side, functional separators reduce dendrite propagation with a conductive lithiophilic layer and a uniform Li-ion channel or form a stable solid electrolyte interphase layer through the continuous release of active agents. The classification of functional separators solving the degradation stemming from the cathodes, which has often been overlooked, is summarized. Structural deterioration and the resulting leakage from cathode materials are suppressed by acidic impurity scavenging, transition metal ion capture, and polysulfide shuttle effect inhibition from functional separators. Furthermore, flame-retardant separators for preventing LMB safety issues and multifunctional separators are discussed. Further expansion of functional separators can be effectively utilized in other types of batteries, indicating that intensive and extensive research on functional separators is expected to continue in LIBs.

An electrolyte additive of bromoxoindole enables uniform Li-ion flux and tunable Li2S deposition for high-performance lithium–sulfur batteries

6-Bromoxoindole, an electrolyte additive, enables the lithium–sulfur battery to operate stably under high-loading, lean-electrolyte, and low-temperature conditions simultaneously.

Projection Micro Stereolithography of Skin Layered Microporous Polymer Membranes As a Separator for Li-Ion Batteries

Commercial liquid electrolyte lithium-ion batteries (LIBs) traditionally incorporate microporous polymer membranes, or separators, to isolate electrode contact and enable ionic transport. Although they do not actively participate in cell chemistry, well-designed separators can influence cell performance and safety, and thus, are essential components of a cell. Current separator manufacturing processes include "wet" or "dry" mechanical stretching , phase inversion, and evaporation-induced phase separation. However, these processes have limited morphological control of geometry and layered structures. Additive manufacturing techniques have been used to rapidly prototype materials that have both high customizability and fine microstructural control. We investigate hexanediol diacrylate (HDDA) as a polymer system using projection micro-stereolithography, a layer-by-layer photopolymerization technique, to develop separators with controlled microstructures for Li-ion batteries. We successfully fabricate a unique polymer architecture of alternating nanometer thin skin layers and microporous network. The fine control of printing parameters (i.e., printing platform, skin layers, and exposure time), results in tunable porosity and morphology. This unique approach to manufacturing LIB separators provides hierarchical homogeneity for more uniform Li-ion transport. It’s potential as a LIB separator is explored by characterizing its electrolyte wettability, thermal tolerance, electrochemical properties, and mechanical stability. Finally, lithium symmetric cells using the HDDA microporous membranes are evaluated against Celgard 2325 separators. This work provides a promising new route for developing separators using additive manufacturing techniques to enable high performance Li-ion batteries.

Amorphous Chloride Solid Electrolytes with High Li-Ion Conductivity for Stable Cycling of All-Solid-State High-Nickel Cathodes.

Solid electrolytes (SEs) are central components that enable high-performance, all-solid-state lithium batteries (ASSLBs). Amorphous SEs hold great potential for ASSLBs because their grain-boundary-free characteristics facilitate intact solid-solid contact and uniform Li-ion conduction for high-performance cathodes. However, amorphous oxide SEs with limited ionic conductivities and glassy sulfide SEs with narrow electrochemical windows cannot sustain high-nickel cathodes. Herein, we report a class of amorphous Li-Ta-Cl-based chloride SEs possessing high Li-ion conductivity (up to 7.16 mS cm-1) and low Young's modulus (approximately 3 GPa) to enable excellent Li-ion conduction and intact physical contact among rigid components in ASSLBs. We reveal that the amorphous Li-Ta-Cl matrix is composed of LiCl43-, LiCl54-, LiCl65- polyhedra, and TaCl6- octahedra via machine-learning simulation, solid-state 7Li nuclear magnetic resonance, and X-ray absorption analysis. Attractively, our amorphous chloride SEs exhibit excellent compatibility with high-nickel cathodes. We demonstrate that ASSLBs comprising amorphous chloride SEs and high-nickel single-crystal cathodes (LiNi0.88Co0.07Mn0.05O2) exhibit ∼99% capacity retention after 800 cycles at ∼3 C under 1 mA h cm-2 and ∼80% capacity retention after 75 cycles at 0.2 C under a high areal capacity of 5 mA h cm-2. Most importantly, a stable operation of up to 9800 cycles with a capacity retention of ∼77% at a high rate of 3.4 C can be achieved in a freezing environment of -10 °C. Our amorphous chloride SEs will pave the way to realize high-performance high-nickel cathodes for high-energy-density ASSLBs.

A LiF-Rich Solid Electrolyte Interphase in a Routine Carbonate Electrolyte by Tuning the Interfacial Chemistry Behavior of LiPF6 for Stable Li Metal Anodes.

Lithium (Li) dendrite growth in a routine carbonate electrolyte (RCE) is the main culprit hindering the practical application of Li metal anodes. Herein, we realize the regulation of the LiPF6 decomposition pathway in RCE containing 1.0 M LiPF6 by introducing a "self-polymerizing" additive, ethyl isothiocyanate (EITC), resulting in a robust LiF-rich solid electrolyte interphase (SEI). The effect of 1 vol % EITC on the electrode/electrolyte interfacial chemistry slows the formation of the byproduct LixPOFy. Such a LiF-rich SEI with EITC polymer winding exhibits a high Young's modulus and a uniform Li-ion flux, which suppresses dendrite growth and interface fluctuation. The EITC-based Li metal cell using a Li4Ti5O12 cathode delivers a capacity retention of 81.4% over 1000 cycles at 10 C, outperforming its counterpart. The cycling stability of 1 Ah pouch cells was further evaluated under EITC. We believe that this work provides a new method for tuning the interfacial chemistry of Li metal through electrolyte additives.

Borate-Based Artificial Solid-Electrolyte Interphase Enabling Stable Lithium Metal Anodes.

Lithium (Li) metal is considered as the "holy grail" of anode materials for next-generation high energy batteries. However, notorious dendrite growth and interfacial instability could induce irreversible capacity loss and safety issues, limiting the practical application of Li metal anodes. Herein, we develop a novel approach to construct a borate-based artificial solid-electrolyte interphase (designated as B-SEI) through the reaction of metallic Li with triethylamine borane (TEAB). According to our cryogenic electron microscopy (Cryo-EM) characterization results, the artificial SEI adopts a glass-crystal bilayer structure, which facilitates uniform Li-ion transport and inhibits dendrite growth during Li plating. Benefiting from such an artificial SEI, the Li anode delivers an improved rate performance and prolonged cycle life. The symmetric Li/B-SEI||Li/B-SEI cell can maintain stable cycling for 700 h at a high current density of 3 mA cm-2. The full-cell pairing Li/B-SEI with LiFePO4 only exhibits minimal capacity decay after 500 cycles in a conventional carbonate-based electrolyte. This work demonstrates the feasibility of building a boride-based artificial SEI to stabilize the Li metal anode based on microscopic characterization results and comprehensive electrochemical data, which represents a promising avenue to develop practical Li metal batteries.

An optimizing hybrid interface architecture for unleashing the potential of sulfide-based all-solid-state battery

Sulfide-based all-solid-state lithium metal batteries are received tremendous focus due to the potential to deliver high energy density. Nevertheless, extremely unstable lithium/sulfide interface reaction and growth of unfavorable Li dendrites upon cycling remain challenging aspects and not yet fully settled. In this work, a lithophilic and high interfacial-energy hybrid interphase rich in chloride and Li-Ga alloy was in-situ constructed at Li/Li7P3S11 interface to tackle the vexing issue. Benefiting from the high interfacial energy and electronic insulation of LiCl in the hybrid interphase, lithium dendrites were effectively inhibited. In addition, the Li-Ga alloy-rich layer possesses excellent lithiophilicity and low diffusion energy, which can provide a uniform electric field distribution and induce rapid conduction of Li-ions. Consequently, the densification of Li/Li7P3S11 interface is achieved, which contributes to the decrease of interfacial impedance, uniform Li-ion flux and inhibition of continuous side reactions. Exalting, the Li symmetric cells with the Li-Ga alloy/LiCl (LGC) interlayer display high critical current density of 1.5 mA cm−2 and steady cycle for 1000 h at 0.3 mA cm−2 (0.3 mAh cm−2) at room temperature. Furthermore, the modified all-solid-state lithium battery also demonstrates an ultra-stable cycling. This work provides a reasonable design approach for the selection of interface layers in the all-solid-state lithium metal batteries (ASSLMBs) based on theoretical calculations, with the objective of attaining a stable Li/sulfide solid electrolyte interface.

Uniform Li-ion diffusion and robust solid electrolyte interface construction for kilogram-scale Si@ZIF powder as the anode in Li-ion batteries

The zeolitic imidazolate framework (ZIF) is characterized by a highly ordered structure, large cavities, and thermal/chemical stabilities and has been widely researched for energy storage. In this study, using commercial Si powder with a diameter of 50–200 nm at a kilogram scale, Si@ZIF core-shell particles with dispersed ZIF-8 rhombic dodecahedrons were fabricated by a one-pot method and achieved excellent electrochemical performance. With the specific pore diameter and ordered network formed by membered rings, experimental results demonstrated that the ZIF-8 shell realized a uniform and accelerated Li+ diffusion route, alleviated volumetric expansion of the Si core, and constructed a LiF-concentrated robust solid electrolyte interface film with less unnecessary consumption of electrolyte and Li+. Density functional theory calculations verified the higher adsorption energy for Li-solvated clusters and the de-solvation effect on the surface of ZIF-8, which can increase Li+ concentration along the one-dimensional channels of 4-membered ring with a diameter similar to that of Li+ for high-speed and uniform Li+ intercalation. Furthermore, the large and elastic rhombic dodecahedrons formed by pure ZIF-8 buffered the volume change and maintained the integrity of the Si electrode during cycling. As a result, the Si@8Z anode achieved a reversible capacity of 818.5 mAh g−1 after 650 cycles at 1 A g−1 with a high initial coulombic efficiency of 88.2 % and outstanding rater performance even at 8 A g−1. Nevertheless, the capacity of the Si anode decreased to 0 mAh g−1 after 200 cycles. The present work clarifies the effect of ZIF on the performance of Si anodes and provides a simple method to modify commercial Si powder.

Dual-Protective Artificial Layer on Lithium Metal Anodes for Improved Electrochemical Performance – an in-Depth Morphological and Electrochemical Characterization

The energy density of traditional lithium ion batteries (LIB) based on graphite intercalation compounds as negative active material is approaching the theoretical limit and are restricting the increasing demand of high energy battery systems for various mobile and stationary applications.[1] Consequently, the implementation of active materials with high specific energies became prerequisite for future battery technologies. Therein, lithium metal is one of the most promising anode active materials to replace state-of-the-art graphite active materials, due to its high theoretical capacity and low electrode potential.[2]However, poor cycling performance, low Coulombic efficiency, and the uncontrollable Li dendrite growth during lithium electrodeposition/dissolution processes remain as predominant challenges.[3] Several approaches were proposed to eliminate dendrite formation by implementing a mechanically and electrochemically stable artificial solid electrolyte interphase or artificial protective coatings (aPC) by in-situ or ex-situ surface modifications.[4] These designed aPCs should feature an increased and uniform Li-ion flux, mechanical robustness and/or protection against electrolyte decomposition, during substantial volume changes upon electrodeposition/dissolution. However, aPCs fail to support long term cycling stability in lithium metal batteries since they cannot cover all requirements.[5] Therefore, it is crucial to design and understand dual- and multilayer system that address multiple aforementioned requisites.[6] In this contribution, a dual-protective artificial layer is constructed on Li metal by physical vapor deposition consisting of an intermetallic LiZn-layer, providing a uniform Li-ion flux, and an inorganic Li3N-layer, which is electron-blocking, thus reveal surface protective properties. In addition to electrochemical characterization, the Li electrodeposition/dissolution behavior was investigated by cryo-FIB/SEM analysis to unravel the mechanism behind the enhanced cycling stability in symmetrical Li||Li cells and cells with a layered oxide-based positive electrode.[1] R. Schmuch, R. Wagner, G. Hörpel, T. Placke, M. Winter, Nature Energy 2018, 3, 267.[2] J. Liu, Z. Bao, Y. Cui, E. J. Dufek, J. B. Goodenough, P. Khalifah, Q. Li, B. Y. Liaw, P. Liu, A. Manthiram, Y. S. Meng, V. R. Subramanian, M. F. Toney, V. V. Viswanathan, M. S. Whittingham, J. Xiao, W. Xu, J. Yang, X.-Q. Yang, J.-G. Zhang, Nature Energy 2019, 4, 180.[3] T. Placke, R. Kloepsch, S. Dühnen, M. Winter, Journal of Solid State Electrochemistry 2017, 21, 1939.[4] N. Delaporte, Y. Wang, K. Zaghib, Frontiers in Materials 2019, 6.[5] D. Lin, Y. Liu, Y. Cui, Nature Nanotechnology 2017, 12, 194.[6] S. Lee, K.-s. Lee, S. Kim, K. Yoon, S. Han, M. H. Lee, Y. Ko, J. H. Noh, W. Kim, K. Kang, Science Advances 2022, 8, 1.

High Performance Anode-Free Lithium Pouch Cells Employing Lithiophilic Gel Polymer Electrolyte with Ion Conductive Network

Anode-free lithium metal batteries have recently emerged as a next generation battery due to increased energy density by adopting bare current collector as an anode without excess lithium source. However, lithium tends to grow in uncontrolled dendritic form when depositied on a heterogeneous current collector, which eventually leads to low coloumbic efficiency and poor life span of the battery. Recent studies have attempted to apply artificial solid electrolyte interphase (SEI) on the current collector to solve theses problems. PEO-based polymeric artificial SEI is commonly used due to high lithium ion conductivity and flexiblility, but its weak physical properties limit its practical application. Herein, we report a chemically cross-linked poly (ethylene glycol) diacrylate (PEGDA)-based gel polymer electrolyte containing AgNO3 as Li nucleation seed for uniform Li deposition. It guides uniform Li-ion flux at the electrode/electrolyte interface and provides mechanical strength to suppress lithium dendrite growth. The gel polymer electrolyte was applied to anode free pouch cell and its cycling performance was investigated in the voltage range of 3.6 - 4.3 V at 0.5 C rate. Our results demonstrate that the proper combination of electrolyte and current collector can increase the conversion of polymerization and achieve stable interfacial properties with electrodes, resulting in improvement of the cycle life of anode free lithium pouch cell.

Polydopamine layer-coated porous Ni foam host for Li metal batteries under lean electrolytic cell operations

Li metal batteries (LMBs) face challenges such as volume change, dendrite growth, electrolyte depletion, and safety concerns. To address these issues, employing three-dimensional (3D) porous substrates and artificial solid electrolyte interphase (SEI) layers has been proposed for uniform Li ion distribution and interfacial stability. Here, we present a dendrite-free Li metal anode for LMBs operating under lean electrolytic conditions. This is achieved by synergistically combining oxidized 3D Ni foam as a conductive substrate and polydopamine (PDA) coating as an artificial SEI layer. The oxidized 3D Ni foam provides abundant lithiophilic sites with a large surface area for Li-ion deposition, effectively mitigating volume expansion due to its high elastic modulus. The PDA artificial SEI layer acts as a protective barrier, enhancing electrolyte wettability and preventing direct contact with Li metal surface. The PDA-coated oxidized 3D Ni foam demonstrates stabilized operation in full cell even with a small amount of electrolyte, achieving a Coulombic efficiency of approximately 99 % over 150 cycles and an exceptionally low voltage hysteresis (∼10 mV) for over 400 h. Our approach utilizing the highly conductive 3D foam substrate and the passivating PDA SEI layer enables outstanding electrochemical performance, opening avenues for future research on commercially viable LMBs.

Single-ion conductors functionalized graphene oxide enabling solid polymer electrolytes with uniform Li-ion transport toward stable and dendrite-free lithium metal batteries

The utilization of poly(ethylene oxide) (PEO)-based solid polymer electrolytes (SPEs) has long been deemed promising for the application of state-of-the-art lithium metal metals (LMBs), but still severely impeded by the insufficient Li-ion transporting channels and inhomogeneous Li deposition. Herein, the design of single-ion conductors (PSLi) modified graphene oxide nanosheets (GO-PSLi)-reinforced PEO-based SPEs to address these long-standing issues is proposed. The electronegative sulfonate-rich groups with lithiophilic features on GO-PSLi surface not only effectively enhance the dispersion of nanoparticles within the PEO matrix, but also provide fast Li-ion diffusion pathways. Meanwhile, introducing PSLi chains is also favorable to highly reducing the crystallization of composite SPEs through hydrogen interactions derived from the desired amide functional groups. This, in turn, facilitates segmental relaxation of the PEO backbone, leading to accelerates the Li-ion migration. As a proof of concept, the as-prepared composite SPEs demonstrate a good ionic conductivity of 2.2 × 10−4 S cm−1 and a high lithium transference number of 0.53, significantly outperforming the pure PEO SPEs (1.0 × 10−4 S cm−1 and 0.28, respectively) at 60 °C. In addition, the symmetrical Li||Li cells based on the composite SPEs show excellent reversible lithium plating/stripping performances with dendrite-free uniform lithium deposition over 1100 h under a current of 0.1 mA cm−2 at 60 °C. The Li||LiFePO4 batteries also achieve an impressive capacity of 120.2 mAh g−1 at a high current density of 4C and deliver remarkable cycling abilities with 84.6% retention after 250 cycles under 1C at 60 °C. This study offers a facile and practical strategy to develop advanced composite PEO-based SPEs for safe and dendrite-free solid-state LMBs.

Li Plating Regulation on Fast-Charging Graphite Anodes by a Triglyme-LiNO3 Synergistic Electrolyte Additive.

Graphite anodes are prone to dangerous Li plating during fast charging, but the difficulty to identify the rate-limiting step has made a challenging to eliminate Li plating thoroughly. Thus, the inherent thinking on inhibiting Li plating needs to be compromised. Herein, an elastic solid electrolyte interphase (SEI) with uniform Li-ion flux is constructed on graphite anode by introducing a triglyme (G3)-LiNO3 synergistic additive (GLN) to commercial carbonate electrolyte, for realizing a dendrite-free and highly-reversible Li plating under high rates. The cross-linked oligomeric ether and Li3N particles derived from the GLN greatly improve the stability of the SEI before and after Li plating and facilitate the uniform Li deposition. When 51% of lithiation capacity is contributed from Li plating, the graphite anode in the electrolyte with 5 vol.% GLN achieved an average 99.6% Li plating reversibility over 100 cycles. In addition, the 1.2-Ah LiFePO4 | graphite pouch cell with GLN-added electrolyte stably operated over 150 cycles at 3 C, firmly demonstrating the promise of GLN in commercial Li-ion batteries for fast-charging applications.

Multifunctional electrospun PVDF-HFP gel polymer electrolyte membrane suppresses dendrite growth in anode-free li metal battery

It is widely accepted that high electrolyte consumption due to decomposition leads to rapid capacity fading in anode-free Li metal batteries (AFLMBs). Here, we report an electrospun gel polymer electrolyte (GPE) membrane, unpeeled-off and integrated with its Cu foil collector (Cu@GPE), prepared using a novel method. The Cu@GPE provides bifunctional applications; as electrolytes and an artificial solid-electrolyte interphase (ASEI). Interestingly, the strong electrostatic interaction between the fiber sheet and the Cu foil collector reconstructs the Cu surface structure, confirmed by grazing angle X-ray diffraction, which positively influences the fluidity of deposited Li. X-ray absorption, depth profile of X-ray photoelectron, Raman and infrared spectroscopies analyses showed the formation of pure β-phase PVDF-HFP as ASEI in which the F elements are aligned toward the Cu surface. These lead to a uniform Li-ion flux and regulate the Li nucleation due to the strong binding between Li and electronegative C-F functional groups promoting uniform Li deposition. The Cu@GPE|Li cell achieved outstanding performance even at a high current density of up to 5 mA cm−2 (coulombic efficiency, 97.14%) after 200 cycles relative to the GPE prepared by the conventional method (cGPE) (90.08%) after 100 cycles. Coupling with LiNi0.33Mn0.33Co0.33O2 (NMC), the Cu@GPE|NMC AFLMB delivered superior performance than Cu|cGPE|NMC.