Supramolecular polymer cross-linking gel electrolyte for highly stable quasi-solid-state lithium metal batteries.

Lithium (Li) metal batteries have the advantage of high energy density, but the Li dendrites risk piercing the separator and causing a short circuit in the battery. Replacing the liquid electrolytes with gel electrolytes is considered an effective strategy to solve the issues. Herein, a poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)-based gel electrolyte, improved with multifunctional supramolecular polymer (MSP), was prepared to enhance the cycling stability and energy density of quasi-solid-state Li metal batteries. The MSP addictive constructs a cross-linked network structure with PVDF-HFP matrix and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) through hydrogen bonding, improving the mechanical strength of the composite gel electrolyte (PH-10%MSP-GE) to against the growth of Li dendrites. Moreover, the pre-lithiated sulfonic acid groups, conductive polyether groups of MSP, and the attraction of TFSI- anions, promote the Li-ion transportation of the composite gel electrolyte. Finally, the Li||Li symmetric cell cycle stably for over 450 h. The Li||LiFePO4 full cell demonstrates a high energy density and excellent cycling stability for over 600 cycles, with a capacity retention rate of up to 98.7%. This work provides valuable insights into the preparation of multifunctional composite gel polymer electrolytes and competitive quasi-solid-state Li metal batteries.

Boron Surface Treatment of Li7La3Zr2O12 Enabling Solid Composite Electrolytes for Li-metal Battery Applications.

Despite being promoted as a superior Li-ion conductor, lithium lanthanum zirconium oxide (LLZO) still suffers from a number of shortcomings when employed as an active ceramic filler in composite polymer-ceramic solid electrolytes for rechargeable all-solid-state lithium metal batteries. One of the main limitations is the detrimental presence of Li2CO3 on the surface of LLZO particles, restricting Li-ion transport at the polymer-ceramic interfaces. In this work, a facile way to improve this interface is presented, by purposely engineering the LLZO particle surfaces for better compatibility with a PEO:LiTFSI solid polymer electrolyte matrix. It is shown that an surface treatment based on immersing LLZO particles in a boric acid solution can improve the LLZO surface chemistry, resulting in an enhancement in the ionic conductivity and cation transference number of the CPE with 20 wt.% of boron-treated LLZO particles compared to the analogous CPE with non-treated LLZO. Ultimately, an improved cycling performance and stability in Li // LiFePO4 cells was also demonstrated for the modified material.

Li2ZnCu3 modified Cu current collector to regulate Li deposition.

Rationally designing a current collector that can maintain low lithium (Li) porosity and smooth morphology while enduring high-loading Li deposition is crucial for realizing the high energy density of Li metal batteries, but it is still challengeable. Herein, a Li2ZnCu3 alloy-modified Cu foil is reported as a stable current collector to fulfill the stable high-loading Li deposition. Benefiting from the in-situ alloying, the generated numerous Li2ZnCu3@Cu heterojunctions induce a homogeneous Li nucleation and dense growth even at an ultrahigh capacity of 12 mAh cm-2. Such a spatial structure endows the overall Li2ZnCu3@Cu electrode with the manipulated steric hindrance and outmost surface electric potential to suppress the side reactions during Li stripping and plating. The resultant Li||Li2ZnCu3@Cu asymmetric cell preserves an ultrahigh average Coulombic efficiency of 99.2% at 3 mA cm-2/6 mAh cm-2 over 200 cycles. Moreover, the Li-Li2ZnCu3@Cu||LiFePO4 cell maintains a cycling stability of 87.5% after 300 cycles. After coupling with the LiCoO2 cathode (4 mAh cm-2), the cell exhibits a high energy density of 407.4 Wh kg-1 with remarkable cycling reversibility at an N/P ratio of 3. All these findings present a doable way to realize the high-capacity, dendrite-free, and dense Li deposition for high-performance Li metal batteries.

High Young's Modulus LixTiO2 Layer Suppressing the Pulverization and Deactivation of Lithiophilic Ag Nanoparticles.

Anode-free Lithium metal batteries, with their high energy density (>500 Wh/kg), are emerging as a promising solution for high-energy-density rechargeable batteries. However, the Coulombic Efficiency and capacity often decline due to interface side reactions. To address this, a lithiophilic layer is introduced, promoting stable and uniform Li deposition. Despite its effectiveness, this layer often undergoes electrochemical deactivation over time. This work investigates lithiophilic silver (Ag), prepared via magnetron sputtering on a copper (Cu) current collector. Finite element simulations identify stress changes from alloying reactions as a key cause of Ag particle pulverization and deactivation. A high Young's modulus coating layer is proposed to mitigate this. The Ag2TiO3@Ag@TiO2@Cu composite electrode, designed with multi-layer structures, demonstrates a slower deactivation process through galvanostatic electrochemical cycling. Characterization methods such as SEM, AFM, and TEM confirm the suppression of Ag particle pulverization, while uncoated Ag fractures and deactivates. This work uncovers a potential failure mechanism of lithiophilic metallic nanoparticles and proposes a strategy for deactivation suppression using an artificial coating layer.

In Situ Inorganic/Organic Protective Layer on Carbon Paper as Advanced Current Collector for Robust Li Metal Anode.

Lithium (Li) metal is regarded as the most promising anode for next-generation batteries with high energy density. However, the uncontrolled dendrite growth and infinite volume expansion during cycling seriously hinder the application of Li metal batteries (LMBs). Herein, an inorganic/organic protective layer (labeled as BPH), composed of in situ formed inorganic constituents and PVDF-HFP, is designed on the 3D carbon paper (CP) surface by hot-dipping method. The BPH layer can effectively improve the mechanical strength and ionic conductivity of the SEI layer, which is beneficial to expedite the Li-ion transfer of the entire framework and achieve stable Li plating/stripping behavior. As a result, the modified 3D CP (BPH-CP) exhibits an ultrahigh average Coulombic efficiency (CE) of ≈99.7% over 400 cycles. Further, the Li||LiFePO4 (LFP) cell exhibits an extremely long-term cycle life of over 3000 cycles at 5 C. Importantly, the full cell with high mass loading LiFePO4 (20 mg cm-2) or LiNi0.8Co0.1Mn0.1O2 (NCM, 16 mg cm-2) cathode exhibits stable cycling for 100 or 150 cycles at 0.5 C with high-capacity retention of 86.5% or 82.0% even at extremely low N/P ratio of 0.88 or 0.94. believe that this work enlightens a simple and effective strategy for the application of high-energy-density and high-rate-C LMBs.

Enhancing Anion-Selective Catalysis for Stable Lithium Metal Pouch Cells through Charge Separated COF Interlayer.

Regulating the composition of solid-electrolyte-interphase (SEI) is the key to construct high-energy density lithium metal batteries. Here we report a selective catalysis anionic decomposition strategy to achieve a lithium fluoride (LiF)-rich SEI for stable lithium metal batteries. To accomplish this, the tris(4-aminophenyl) amine-pyromeletic dianhydride covalent organic frameworks (TP-COF) was adopted as an interlayer on lithium metal anode. The strong donor-acceptor unit structure of TP-COF induces local charge separation, resulting in electron depletion and thus boosting its affinity to FSI-. The strong interaction between TP-COF and FSI- lowers the lowest unoccupied molecular orbital (LUMO) energy level of FSI-, accelerating the decomposition of FSI- and generating a stable LiF-rich SEI. This feature facilitates rapid Li+ transfer and suppresses dendritic Li growth. Notably, we demonstrate a 6.5 Ah LiNi0.8Co0.1Mn0.1O2|TP-COF@Li pouch cell with high energy density (473.4 Wh kg-1) and excellent cycling stability (97.4 %, 95 cycles) under lean electrolyte 1.39 g Ah-1, high areal capacity 5.7 mAh cm-2, and high current density 2.7 mA cm-2. Our selective catalysis strategy opens a promising avenue toward the practical applications of high energy-density rechargeable batteries.

Dual Ionic Pathways in Semi-Solid Electrolyte based on Binary Metal-Organic Frameworks Enable Stable Operation of Li-Metal Batteries at Extremely High Temperatures.

The rapid development of the electronics market necessitates energy storage devices characterized by high energy density and capacity, alongside the ability to maintain stable and safe operation under harsh conditions, particularly elevated temperatures. In this study, a semi-solid-state electrolyte (SSSE) for Li-metal batteries (LMB) is synthesized by integrating metal-organic frameworks (MOFs) as host materials featuring a hierarchical pore structure. A trace amount of liquid electrolyte (LE) is entrapped within these pores through electrochemical activation. These findings demonstrate that this structure exhibits outstanding properties, including remarkably high thermal stability, an extended electrochemical window (5.25 V vs Li/Li+), and robust lithium-ion conductivity (2.04 × 10-4 S cm-1), owing to the synergistic effect of the hierarchical MOF pores facilitating the storage and transport of Li ions. The Li//LiFePO4 cell incorporating prepared SSSE shows excellent capacity retention, retaining 97% (162.8 mAh g-1) of their initial capacity after 100 cycles at 1 C rate at an extremely high temperature of 95 °C. It is believed that this study not only advances the understanding of ion transport in MOF-based SSSE but also significantly contributes to the development of LMB capable of stable and safe operation even under extremely high temperatures.

ZnS Nanoseeds Sealed in N, P, S Co-Doped Carbon Hollow Rhombic Dodecahedra as a Superlithiophilic Host for Dendrite-Free Lithium Metal Anodes.

Lithium (Li) metal is considered a hopeful anode for next-generation Li-ion batteries thanks to its ultra-high theoretical specific capacity, extra-low theoretical density, and low negative potential. However, the uncontrolled growth of Li dendrites and volume fluctuation during plating/stripping processes severely hamper its commercial application. Herein, ZnS seeds sealed in N, P, S co-doped carbon hollow rhombic dodecahedra (ZnS@NPS-C HRD) is fabricated as a superlithiophilic host for Li metal anodes (LMAs) to solve the above problems. In addition, the Li nucleation and deposition mechanism on ZnS@NPS-C HRD is investigated by in situ optical microscopy, ex-situ X-ray diffraction, scanning electron microscopy, and theoretical calculations. Owing to the synergistic strategy of ZnS seeds-inducing nucleation and Li-limited growth, the as-prepared composite exhibits stability for 300 cycles in asymmetric cells and a long lifespan over 1100 h in symmetric cells. Moreover, the ZnS@NPS-C HRD@Li|LiFePO4 full cell demonstrates a reversible capacity of 100.91 mAh g-1 after 400 cycles at 1 C.

Designing Cooperative Ion Transport Pathway in Ultra-Thin Solid-State Electrolytes toward Practical Lithium Metal Batteries.

Solid polymer electrolytes (SPEs) are promising for high-energy-density solid-state Li metal batteries due to their decent flexibility, safety, and interfacial stability. However, their development was seriously hindered by the interfacial instability and limited conductivity, leading to inferior electrochemical performance.  Herein, we proposed to design ultra-thin solid-state electrolyte with long-range cooperative ion transport pathway to effectively increase the ionic conductivity and stability. The impregnation of PVDF-HFP inside pores of  fluorinated covalent organic framework (CF3-COF) can disrupt its symmetry, rendering rapid ion transportation and inhibited anion imigration. The functional groups of CF3-COF can interact with PVDF-HFP to form fast Li+ transport channels, which enables the uniform and confined Li+ conduction within the electrolyte. The introduction of CF3-COF also enhances the mechanical strength and flexibility of SPEs, as well as ensures homogeneous Li deposition and inhibited dendrite growth.  Hence, a remarkably high conductivity of 1.21×10-3 S cm-1 can be achieved. Finally, the ultra-thin SPEs with an extremely long cycle life exceed 9000 h can be obtained (the longest cycle life reported until now) while the NCM523/Li pouch cell demonstrates a high capacity of 760 mAh and 96% capacity retention after cycling, holding great promises to be utilized for practical solid-state Li metal batteries.

Eliminating Hydrogen Fluoride through Piperidine-Doped Separators for Stable Li Metal Batteries with Nickel-Rich Cathodes.

Hydrofluoric acid (HF)-induced electrode and interfacial structure degeneration poses a significant challenge for high-voltage lithium metal batteries (LMBs). To address this issue, we propose a separator strategy that involves decorating a regular polyethylene (PE) separator with molecular sieves (TW) impregnated with piperidine (PI). The porous structure of the TW serves as a reaction chamber for PI and HF. As a result, the HF content in the controlled electrolyte with 500 ppm H2O (ELE-500) is notably reduced when using TW@PI-PE separators, thereby shielding nickel-rich cathodes from HF etching. Simultaneously, due to the hydrolysis of Li salts, and the inertness of PI towards H2O, a uniform lithium fluoride (LiF)-rich solid electrolyte interphase can form on the Li metal anode, further mitigating dendrite formation. The lifespan of the symmetric Li cell using the TW@PI-PE separator is doubled in ELE-500, exhibiting stable 500-hour cycles at 3 mA cm-2 and 3 mAh cm-2. Additionally, with the effective limitation of transition metal (TM) dissolution, the 4.6-V LMBs employing a LiNi0.8Co0.1Mn0.1O2 cathode maintain an 81% capacity retention over 100 cycles, even in ELE-1000. The innovative TW@PI system presented here offers a fresh perspective for future research aimed at eliminating HF in LMBs.

Asymmetrical Functionalization of Polarizable Interface Restructuring Molecules for Rapid and Longer Operative Lithium Metal Batteries.

Lithium metal batteries (LMBs) have been recognized as high-energy storage alternatives; however, problematic surface reactions due to dendritic Li growth are major obstacles to their widespread utilization. Herein, a 3-mercapto-1-propanesulfonic acid sodium salt (MPS) with asymmetrically functionalized thiol and sulfonate groups as polarizable interface-restructuring molecules is proposed to achieve rapid and longer-operating LMBs. Under a harsh condition of 5 mA cm-2, Li-Li symmetric cells employing MPS can be cycled over 1200 cycles, outperforming those employing other molecules symmetrically functionalized by thiol or sulfonate groups. The improved performance of the Li|V2O5 full cell is demonstrated by introducing MPS additives. MPS additives offer advantages by flattening the surface, reconfiguring Li nucleation and growth along the stable (110) plane, and forming a durable and conductive solid-electrolyte interface layer (SEI). This study suggests an effective way to develop a new class of electrolyte additives for LMBs by controlling engineering factors, such as functional groups and polarizable properties.

Solvation Regulation Reinforces Anion-Derived Inorganic-Rich Interphase for High-Performance Quasi-Solid-State Li Metal Batteries.

Solid-state polymer lithium metal batteries are an important strategy for achieving high safety and high energy density. However, the issue of Li dendrites and inherent inferior interface greatly restricts practical application. Herein, this study introduces tris(2,2,2-trifluoroethyl)phosphate solvent with moderate solvation ability, which can not only complex with Li+ to promote the in-situ ring-opening polymerization of 1,3-dioxolane (DOL), but also build solvated structure models to explore the effect of different solvation structures in the polymer electrolyte. Thereinto, it is dominated by the contact ion pair solvated structure with pDOL chain segments forming less lithium bonds, exhibiting faster kinetic process and constructing a robust anion-derived inorganic-rich interphase, which significantly improves the utilization rate of active Li and the high-voltage resistance of pDOL. As a result, it exhibits stable cycling at ultra-high areal capacity of 20 mAh cm-2 in half cells, and an ultra-long lifetime of over 2000 h in symmetric cells can be realized. Furthermore, matched with LiNi0.9Co0.05Mn0.05O2 cathode, the capacity retention after 60 cycles is as high as 96.8% at N/P value of 3.33. Remarkably, 0.7 Ah Li||LiNi0.9Co0.05Mn0.05O2 pouch cell with an energy density of 461 Wh kg-1 can be stably cycled for five cycles at 100% depth of discharge.

Covalent Triazine Based Frameworks with Donor-Donor-π-Acceptor Structures for Dendrite-Free Lithium Metal Batteries.

The appearance of disordered lithium dendrites and fragile solid electrolyte interfaces (SEI) significantly hinder the serviceability of lithium metal batteries. Herein, guided by theoretical predictions, a multi-component covalent triazine framework with partially electronegative channels (4C-TA0.5TF0.5-CTF) is incorporated as a protective layer to modulate the interface stability of the lithium metal batteries. Notably, the 4C-TA0.5TF0.5-CTF with optimized electronic structure at the molecular level by fine-tuning the local acceptor-donor functionalities not only enhances the intermolecular interaction thereby providing larger dipole moment and improved crystallinity and mechanical stress, but also facilitates the beneficial effect of lithiophilic sites (C-F bonds, triazine cores, C=N linkages and aromatic rings) to further regulate the migration of Li+ and achieve a uniform lithium deposition behavior as determined by various in-depth in/ex situ characterizations. Due to the synergistic effect of multi-component organic functionalities, the 4C-TA0.5TF0.5-CTF modified full cells perform significantly better than the common two/three-component 2C-TA-CTF and 3C-TF-CTF electrodes, delivering an excellent capacity of 116.3 mAh g-1 (capacity retention ratio: 86.8 %) after 1000 cycles at 5 C and improved rate capability. This work lays a platform for the prospective molecular design of improved organic framework relative artificial SEI for highly stable lithium metal batteries.

Gradient Lithium Ion Regulation Current Collectors for High-Performance and Dendrite-Free Li Metal Batteries.

Lithium metal anode has attracted wide attention due to its ultrahigh theoretical specific capacity, lowest reduction potential, and low density. However, uncontrollable dendritic growth and volume change caused by uneven Li+ deposition still seriously hinder the large-scale commercial application of lithium metal batteries, even causing serious battery explosions and other safety problems. Hence, gold nanoparticles with a gradient distribution anchored on 3D carbon fiber paper (CP) current collectors followed by the encapsulation of polydopamine (PDA) (CP/Au/PDA) are constructed for stable and dendrite-free Li metal anodes for the first time. Significantly, lithiophilic Au nanoparticles showing a gradient distribution in the carbon fiber paper could guide the transfer of Li+ from the outside to the inside of the CP/Au/PDA electrode as well as lower the nucleation overpotential of Li, thereby obtaining the uniform Li deposition. Meanwhile, the PDA layer could in situ be converted to Li-PDA which could serve as an efficient Li+ conductor to further facilitate uniform Li+ transport among the whole CP/Au/PDA electrode. Besides, 3D carbon fiber paper could effectively accommodate the volume change during the plating/stripping process of Li metal. As a result, CP/Au/PDA electrodes deliver a low nucleation overpotential (∼9 mV) and a high Coulombic efficiency (mean value of ∼98.8%) at a current density of 1 mA cm-2 with the capacity of 1 mA h cm-2. Furthermore, Li@CP/Au/PDA electrodes also can demonstrate an ultralow voltage hysteresis (∼20 mV) and a long cycle life (1000 h) in symmetric cells. Finally, with LiFePO4 (LFP) as the cathode, the Li@CP/Au/PDA-LFP full cell delivers a high discharge capacity of 136 mA h g-1 even after 350 cycles at 1C, exhibiting a per cycle loss as low as 0.01%. This gradient lithium ion regulation current collector is of great significance for the development of lithium metal anodes.

Enhanced Free Li-Ion Mobility in Solid-State Electrolytes via Long-Range Assembly of Porous Materials.

Metal-organic frameworks (MOFs), with their tunable pore sizes and high surface areas, are gaining prominence in Li metal battery applications, including their use as nanofillers in solid composite electrolytes (SCEs) for enhanced ionic conductivity. Yet, when used in SCEs, individual dispersed MOF particles in isolation as nanofillers can impede efficient ion transport in all-solid-state batteries due to the insufficient supply of ionic transport pathways within SCEs. Here, we introduced a continuous SCE nanofiller with long-range assembly interconnected porous MOFs (IMOF_SCE) for effective ion transport pathway supply along the interface between the nanofiller and the polymer matrix. IMOF_SCE achieved Li-ion conductivity (6.72 × 10-5 S cm-1 at 20 °C) and Li-ion transference number (tLi+ = 0.855), resulting in the improved electrochemical performance of Li metal batteries. Additionally, the Li/LiFePO4 full cell integrated with IMOF_SCE achieved an outstanding stable capacity retention of 98.8% in 300 cycles. This work offers insights into the design strategy of effective nanofillers for SCEs and can be adapted for other porous materials.

Sustaining Surface Lithiophilicity of Ultrathin Li-Alloy Coating Layers on Current Collector for Zero-Excess Li-Metal Batteries.

Zero-excess Li-metal batteries (ZE-LMBs) have emerged as the ultimate battery platform, offering an exceptionally high energy density. However, the absence of Li-hosting materials results in uncontrolled dendritic Li deposition on the Cu current collector, leading to chronic loss of Li inventory and severe electrolyte decomposition, limiting its full utilization upon cycling. This study presents the application of ultrathin (≈50 nm) coatings comprising six metallic layers (Cu, Ag, Au, Pt, W, and Fe) on Cu substrates in order to provide insights into the design of Li-depositing current collectors for stable ZE-LMB operation. In contrast to non-alloy Cu, W, and Fe coatings, Ag, Au, and Pt coatings can enhance surface lithiophilicity, effectively suppressing Li dendrite growth, thereby improving Li reversibility. Considering the distinct Li-alloying behaviors, particularly solid-solution and/or intermetallic phase formation, Pt-coated Cu current collectors maintain surface lithiophilicity over repeated Li plating/stripping cycles by preserving the original coating layer, thereby attaining better cycling performance of ZE-LMBs. This highlights the importance of selecting suitable Li-alloy metals to sustain surface lithiophilicity throughout cycling to regulate dendrite-less Li plating and improve the electrochemical stability of ZE-LMBs.

The Dependence of Solid Electrolyte Interphase on the Crystal Facet of Current Collector in Li Metal Battery.

The continuous electrolyte decomposition and uncontrolled dendrite growth caused by the unstable solid electrolyte interphase (SEI) have largely hindered the development of Li metal batteries. Here, we demonstrate that tuning the facet of current collector can regulate the composition of SEI and the subsequent Li deposition behavior using single-crystal Cu foils as an ideal platform. The theoretical and experimental studies reveal that the (100) facet of Cu possesses strong adsorption to anions, guiding more anions to participate preferentially in the inner Helmholtz plane and further promoting the formation of the stable inorganic-rich SEI. Consequently, the single-crystal Cu foils with a single [100] orientation (s-Cu(100)) achieve the dendrite-free Li deposition with enhanced Li plating/stripping reversibility. Moreover, the Li anode deposited on s-Cu(100) can stabilize the operation of an Ah-level pouch cell (350 Wh kg-1) with a low negative/positive capacity ratio (~2) and lean electrolyte (2.4 g Ah-1) for 150 cycles. Impressively, this strategy demonstrates universality in a series of electrolytes employed different anions. This work provides new insights into the correlation between the SEI and current collector, opening a universal avenue towards high-performance Li metal batteries.

Dual-Salts Localized High-Concentration Electrolyte for Li- and Mn-Rich High-Voltage Cathodes in Lithium Metal Batteries.

Limited electrochemical stability windows of conventional carbonate-based electrolytes pose a challenge to support the Lithium (Li)- and manganese (Mn)-rich (LMR) high-voltage cathodes in rechargeable Li-metal batteries (LMBs). To address this issue, a novel localized high-concentration electrolyte (LHCE) composition incorporating LiPF6 and LiTFSI as dual-salts (D-LHCE), tailored for high-voltage (>4.6 Vvs.Li) operation of LMR cathodes in LMBs is introduced. 7Li nuclear magnetic resonance and Raman spectroscopy revealed the characteristics of the solvation structure of D-LHCE. The addition of LiPF6 provides stable Al-current-collector passivation while the addition of LiTFSI improves the stability of D-LHCE by producing a more robust cathode-electrolyte interphase (CEI) on LMR cathode and solid-electrolyte interphase (SEI) on Li-metal anode. As a result, LMR/Li cell, using the D-LHCE, achieved 72.5% capacity retention after 300 cycles, a significant improvement compared to the conventional electrolyte (21.9% after 100 cycles). The stabilities of LMR CEI and Li-metal SEI are systematically analyzed through combined applications of electrochemical impedance spectroscopy and distribution of relaxation times techniques. The results present that D-LHCE concept represents an effective strategy for designing next-generation electrolytes for high-energy and high-voltage LMB cells.

Chemical Prelithiated 3D Lithiophilic/-Phobic Interlayer Enables Long-Term Li Plating/Stripping.

The up-to-date lifespan of zero-excess lithium (Li) metal batteries is limited to a few dozen cycles due to irreversible Li-ion loss caused by interfacial reactions during cycling. Herein, a chemical prelithiated composite interlayer, made of lithiophilic silver (Ag) and lithiophobic copper (Cu) in a 3D porous carbon fiber matrix, is applied on a planar Cu current collector to regulate Li plating and stripping and prevent undesired reactions. The Li-rich surface coating of lithium oxide (Li2O), lithium carboxylate (RCO2Li), lithium carbonates (ROCO2Li), and lithium hydride (LiH) is formed by soaking and directly heating the interlayer in n-butyllithium hexane solution. Although only a thin coating of ∼10 nm is created, it effectively regulates the ionic and electronic conductivity of the interlayer via these surface compounds and reduces defect sites by reactions of n-butyllithium with heteroatoms in the carbon fibers during formation. The spontaneously formed lithiophilic-lithiophobic gradient across individual carbon fiber provides homogeneous Li-ion deposition, preventing concentrated Li deposition. The porous structure of the composite interlayer eliminates the built-in stress upon Li deposition, and the anisotropically distributed carbon fibers enable uniform charge compensation. These features synergistically minimize the side reactions and compensate for Li-ion loss while cycling. The prepared zero-excess Li metal batteries could be cycled 300 times at 1.17 C with negligible capacity fading.

A Comparatively Low Cost, Easy-To-Fabricate, and Environmentally Friendly PVDF/Garnet Composite Solid Electrolyte for Use in Lithium Metal Cells Paired with Lithium Iron Phosphate and Silicon.

Solid electrolytes may be the answer to overcome many obstacles in developing the next generation of renewable batteries. A novel composite solid electrolyte (CSE) composed of a poly(vinylidene fluoride) (PVDF) base with an active nanofiber filler of aluminum-doped garnet Li ceramic, Li salt lithium bis-(trifluoromethanesulfonyl)imide (LiTFSI), Li fluoride (LiF) stabilizing additive, and plasticizer sulfolane was fabricated. In a Li|CSE|LFP cell with this CSE, a high capacity of 168 mAh g-1 with a retention of 98% after 200 cycles was obtained, representing the best performance to date of a solid electrolyte with a PVDF base and a garnet inorganic filler. In a Li metal cell with Si and Li, it yielded a discharge capacity of 2867 mAh g-1 and was cycled 60 times at a current density of 100 mAh g-1, a significant step forward in utilizing a solid electrolyte of any kind with the desirable Si anode. In producing this CSE, the components and fabrication process were chosen to have a lower cost and improved safety and environmental impact compared with the current state-of-the-art Li-ion battery.