Lithium Iron Phosphate Cathode Research Articles

Differential Analysis of Surface-Dominated vs. Bulk-Dominated Electrochemical Processes in Lithium Iron Phosphate Cathodes

Differential Analysis of Surface-Dominated vs. Bulk-Dominated Electrochemical Processes in Lithium Iron Phosphate Cathodes

Effect of NMC-doping Concentration on the Structural Feature and Electrical Properties of Lithium Iron Phosphate Cathode for Use in Lithium-ion Batteries

T his study investigates the synthesis of Lithium Iron Phosphate (LFP) with NMC-doped cathode materials, aiming to enhance the performance of lithium-ion batteries. The NMC content was varied from 0.02 to 0.10wt%, and 1wt% of (NH4)3PO4 was added to all conditions to prevent phosphate loss during the calcination process. The composite powder was prepared using a straightforward mixed oxide method, with a calcination temperature of 600 °C for 5 hours under an argon gas flow. X-ray diffraction (XRD) analysis confirmed the successful formation of pure LFP with an orthorhombic crystal structure, devoid of any secondary phases. To further explore the impact of NMC doping on the structural characteristics, FTIR and Raman spectroscopy were employed. Results revealed that increasing NMC doping concentration beyond 0.02wt% led to the broadening of the PO43− symmetric stretching band at approximately 947 cm−1, indicating a higher degree of disorder in the LFP structures. This disorder was found to adversely affect electrochemical performance, resulting in decreased discharge capacity and increased impedance, as determined by electrochemical impedance spectroscopy (EIS), with higher concentrations of NMC and (NH4)3PO4. Scanning Electron Microscopy (SEM) analysis unveiled the presence of agglomerated particles ranging in size from 0.5 to 0.9 microns. Optimal conditions were identified with the addition of NMC doped at 0.02wt%, which exhibited a discharge capacity of approximately 119.41 mAh/g at 0.2 C, along with a low impedance of 200 Ohm. Moreover, the 0.02wt% sample demonstrated a promising linear trend in cycle performance, suggesting its potential for future applications in lithium-ion batteries.

An Electrochemical-Cycling-Induced Capacitive Component on the Surface of an Electrophoretic-Deposited Lithium Iron Phosphate Cathode

An Electrochemical-Cycling-Induced Capacitive Component on the Surface of an Electrophoretic-Deposited Lithium Iron Phosphate Cathode

Recycling and Reuse of Spent LIBs: Technological Advances and Future Directions.

Recovering valuable metals from spent lithium-ion batteries (LIBs), a kind of solid waste with high pollution and high-value potential, is very important. In recent years, the extraction of valuable metals from the cathodes of spent LIBs and cathode regeneration technology are still rapidly developing (such as flash Joule heating technology to regenerate cathodes). This review summarized the studies published in the recent ten years to catch the rapid pace of development in this field. The development, structure, and working principle of LIBs were firstly introduced. Subsequently, the recent developments in mechanisms and processes of pyrometallurgy and hydrometallurgy for extracting valuable metals and cathode regeneration were summarized. The commonly used processes, products, and efficiencies for the recycling of nickel-cobalt-manganese cathodes (NCM/LCO/LMO/NCA) and lithium iron phosphate (LFP) cathodes were analyzed and compared. Compared with pyrometallurgy and hydrometallurgy, the regeneration method was a method with a higher resource utilization rate, which has more industrial application prospects. Finally, this paper pointed out the shortcomings of the current research and put forward some suggestions for the recovery and reuse of spent lithium-ion battery cathodes in the future.

Enhanced rate capability and capacity of LIB full cells achieved through aerosol jet printing

Thick lithium-iron phosphate (LFP) cathodes (31 mg cm−2) with rationally engineered pore structure and tortuosity were manufactured with an aerosol jet (AJ) printer. Cathode pore structuring was tuned by controlling the rate at which the printed ink dried. Slow-drying prints yielded smoother cathodes while fast-drying prints resulted in mesoscale structuring with substantial surface roughness. X-ray tomography further revealed that the rapid drying of AJ printed LFP cathodes produced low-tortuosity pore channels which were preserved after calendering. Full cells comprised of AJ print optimized LFP cathodes, with 30 mg cm−2 active material loadings, and capacity-matched, AJ printed lithium titanate anodes were assembled and electrochemically tested. Performance of the AJ printed full cells was compared to tape-cast (TC) full cells. At equivalent electrode loadings, compositions, and thicknesses, the AJ full cells outperformed the TC cells, averaging approximately 14% greater capacity per cycle after 100 cycles at a C/2 rate. Furthermore, at 1C, the AJ printed full cells realized a near two-fold increase in discharge capacity over the TC cells.

Application of cathode materials in lithium ion phosphate battery and its modification

Abstract Lithium ion batteries have been widely used in various fields, such as electric vehicles, due to their excellent electrochemical performance. Especially, introducing some functional materials into batteries can further improve battery performance. This research analyses the application of lithium-ion phosphate as the cathode materials of the batteries, with a particular focus on the structural characteristics and various indices of the modification of lithium iron phosphate battery cathode materials. The electrode material is systematically described, highlighting its advantages, disadvantages, and application range while emphasizing its crucial role in different electrochemical performance such as energy density and recyclability. In addition, the relationship between the electrochemical performance and structure properties of cathode materials in LiFePO4 is summarized by placing emphasis on nanoparticle characteristics, interface environment effects, and electrode structures. This research also presents a series of achievements in modifying lithium iron phosphate cathode materials. And it identifies areas that require improvement and looks forward to future challenges and developments in lithium-ion battery cathode materials.

Composite Ionogel Electrodes for Polymeric Solid-State Li-Ion Batteries.

Realizing rechargeable cells with practical energy and power density requires electrodes with high active material loading, a remaining challenge for solid-state batteries. Here, we present a new strategy based on ionogel-derived solid-state electrolytes (SSEs) to form composite electrodes that enable high active material loading (>10 mg/cm2, ~9 mA/cm2 at 1C) in a scalable approach for fabricating Li-ion cells. By tuning the precursor and active materials composition incorporated into the composite lithium titanate electrodes, we achieve near-theoretical capacity utilization at C/5 rates and cells capable of stable cycling at 5.85 mA/cm2 (11.70 A/g) with over 99% average Coulombic efficiency at room temperature. Finally, we demonstrate a complete polymeric solid-state cell with a composite anode and a composite lithium iron phosphate cathode with ionogel SSEs, which is capable of stable cycling at a 1C rate.

Breaking the “dead Li” Barrier: A cross-stacked dual-function framework by SWNTs in graphite-Li hybrid anodes

The accumulation of “dead Li” between lithiated graphite particles leads to interfacial failure, rapid capacity degradation, and reduced longevity in graphite-Li hybrid anodes. To address this issue, we developed a cross-stacked dual-function framework incorporating single-walled carbon nanotubes (SWNTs) that facilitates efficient electron/ion transmission and creates a quasi-three-dimensional porous structure. This framework establishes unobstructed pathways for electron and ion transport between graphite particles, overcoming transmission barriers caused by “dead Li” accumulation and side reactions. Additionally, the quasi-three-dimensional porous structure accommodates more “dead Li” minimizing its accumulation on graphite particles and preserving the activity of graphite intercalation compounds (GICs: LiC12, LiC6, etc.). The dual-function framework ensures excellent cycling performance, achieving 345 cycles at a lithiation level of 500 mAh·g−1 with an average Coulombic efficiency of 98.7 %. When paired with lithium iron phosphate (LFP) cathodes, the hybrid anode demonstrates remarkable capacity retention of 80 % over 300 cycles. This work presents an effective strategy for enhancing the performance of hybrid anodes through rational optimization of mesoscale interfacial transmission and electrode structure.

Cathode Electrolyte Interphase Engineering for Prussian Blue Analogues in Lithium-Ion Batteries.

The increasing use of low-cost lithium iron phosphate cathodes in low-end electric vehicles has sparked interest in Prussian blue analogues (PBAs) for lithium-ion batteries. A major challenge with iron hexacyanoferrate (FeHCFe), particularly in lithium-ion systems, is its slow kinetics in organic electrolytes and valence state inactivation in aqueous ones. We have addressed these issues by developing a polymeric cathode electrolyte interphase (CEI) layer through a ring-opening reaction of ethylene carbonate triggered by OH- radicals from structural water. This facile approach considerably mitigates the sluggish electrochemical kinetics typically observed in organic electrolytes. As a result, FeHCFe has achieved a specific capacity of 125 mAh g-1 with a stable lifetime over 500 cycles, thanks to the effective activation of Fe low-spin states and the structural integrity of the CEI layers. These advancements shed light on the potential of PBAs to be viable, durable, and efficient cathode materials for commercial use.

A Comparative Study on Electrochemical Performance of Single versus Dual Networks in Lithium Metal/Polysulfide-Polyoxide Co-Network/Lithium Titanium Oxide Cathode

The present article introduces a strategy for controlling oxidation and reduction reactions within polymer electrolyte membrane (PEM) networks as a means of enhancing storage capacity through the complexation of dissociated lithium cations with multifunctional groups of the polymer network. Specifically, co-polymer networks based on polysulfide (PS) and polyoxide (PO) precursors, photo-cured in the presence of succinonitrile (SCN) and lithium bis(trifluoro methane sulfonyl imide) (LiTFSI) salt, exhibited ionic conductivity on the order of mid 10−4 S/cm at ambient temperature in the 30/35/35 (weight %) composition. Lithium titanate (LTO, Li4Ti5O12) electrode was chosen as an anode (i.e., a potential source of Li ions) against lithium iron phosphate (LFP, LiFePO4) cathode in conjunction with polysulfide-co-polyoxide dual polyelectrolyte networks to control viscosity for 3D printability on conformal surfaces of drone and aeronautic vehicles. It was found that the PS-co-PO dual network-based polymer electrolyte containing SCN plasticizer and LiTFSI salt exhibited extra storage capacity (i.e., specific capacity of 44 mAh/g) with the overall specific capacity of 170 mAh/g (i.e., for the combined LTO electrode and PEM) initially that stabilized at 153 mAh/g after 50th cycles with a reasonable capacity retention of over 90% and Coulombic efficiency of over 99%. Of particular interest is the observation of the improved electrochemical performance of the polysulfide-co-polyoxide electrolyte dual-network relative to that of the polyoxide electrolyte single-network.

Leaching of NMC industrial black mass in the presence of LFP

This study focuses on the effect of an emerging source of waste, lithium iron phosphate (LFP) cathode materials, on the hydrometallurgical recycling of the currently dominant industrial battery waste that is rich in transition metals (Ni, Co, Mn, and Li). The effects of the dosage of LFP, initial acidity, and timing of LFP reductant addition were investigated in sulfuric acid (H2SO4) leaching (t = 3 h, T = 60 °C, ω = 300 rpm). The results showed that addition of LFP increased both transition metal extraction and acid consumption. Further, the redox potential was lowered due to the increased presence of Fe2+. An initial acidity of 2.0 mol/L H2SO4 with acid consumption of 1.3 kg H2SO4/kg black mass provided optimal conditions for achieving a high leaching yield (Co = 100%, Ni = 87.6%, Mn = 91.1%, Li = 100%) and creating process solutions (Co 8.8 g/L, Ni 13.8 g/L, Li 6.7 g/L, Mn 7.6 g/L, P 12.1 g/L) favorable for subsequent hydrometallurgical processing. Additionally, the overall efficiency of H2O2 decreased due to its decomposition by high concentrations of Fe2+ and Mn2+ when H2O2 was added after t = 2 h, leading to only a minor increase in final battery metals extraction levels.

Direct regeneration of spent LiFePO4 cathode material via a simple solid-phase method

For realizing the goals of “carbon peak” and “carbon neutrality”, lithium-ion batteries (LIB) with LiFePO4 as the cathode material have been widely applied. However, this has also led to a large number of spent lithium-ion batteries, and the safe disposal of spent lithium-ion batteries is an urgent issue. Currently, the main reason for the capacity decay of LiFePO4 materials is the Li deficiency and the formation of the Fe3+ phase. In order to address this issue, we performed high-temperature calcination of the discarded lithium iron phosphate cathode material in a carbon dioxide environment to reduce or partially remove the carbon coating on its surface. Subsequently, mechanical grinding was conducted to ensure thorough mixing of the lithium source with the discarded lithium iron phosphate. The reaction between CO2 and the carbon coating produced a reducing atmosphere, reducing Fe3+ to Fe2+ and thereby reducing the content of Fe3+. The Fe3+ content in the repaired LiFePO4 material is reduced. The crystal structure of spent LiFePO4 cathode materials was repaired more completely compare with the traditional pretreatment method, and the repaired LiFePO4 material shows good electrochemical performance and cycling stability. Under 0.1 C conditions, the initial capacity can reach 149.1 mAh/g. It can be reintroduced for commercial use.

Nanostructured S@VACNTs Cathode with Lithium Sulfate Barrier Layer for Exceptionally Stable Cycling in Lithium-Sulfur Batteries

Lithium-sulfur technology garners significant interest due to sulfur’s higher specific capacity, cost-effectiveness, and environmentally friendly aspects. However, sulfur’s insulating nature and poor cycle life hinder practical application. To address this, a simple modification to the traditional sulfur electrode configuration is implemented, aiming to achieve high capacity, long cycle life, and rapid charge rates. Binder-free sulfur cathode materials are developed using vertically aligned carbon nanotubes (CNTs) decorated with sulfur and a lithium sulfate barrier layer. The aligned CNT framework provides high conductivity for electron transportation and short lithium-ion pathways. Simultaneously, the sulfate barrier layer significantly suppresses the shuttle of polysulfides. The S@VACNTs with Li2SO4 coating exhibit an extremely stable reversible areal capacity of 0.9 mAh cm−2 after 1600 cycles at 1 C with a capacity retention of 80% after 1200 cycles, over three times higher than lithium iron phosphate cathodes cycled at the same rate. Considering safety concerns related to the formation of lithium dendrite, a full cell Si-Li-S is assembled, displaying good electrochemical performances for up to 100 cycles. The combination of advanced electrode architecture using 1D conductive scaffold with high-specific-capacity active material and the implementation of a novel strategy to suppress polysulfides drastically improves the stability and the performance of Li-S batteries.

Efficient and environmentally friendly separation and recycling of cathode materials and current collectors for lithium-ion batteries by fast Joule heating

Spent Li-ion batteries(LIBs) cathodes possess high recycling value. To improve subsequent recovery efficiency and product purity, separating the cathode materials from the aluminum foil is critical. However, traditional separation methods are characterized by high energy consumption, low recycling efficiency, and environmental pollution. This research presents a novel method that involves injecting Joule heat directly into the aluminum foil in the air, resulting in the melting and slight thermal decomposition of the PVDF binder, which reduces its adhesive properties. Owing to the difference in thermal expansion coefficients between the binder and aluminum foil, an instantaneous thermal stress was generated at the interface of the cathode materials and aluminum foil, resulting in a peeling force. This method enabled a rapid and efficient separation of lithium iron phosphate (LFP) and ternary Li-ion (NCM) battery cathode materials. The optimal separation conditions, separation mechanism, and properties of the recovered products were investigated thoroughly using high-speed camera imaging, temperature rise calculations, and microscopic characterization. This chemical-free method avoids the generation of wastewater and gas emissions. Under optimal experimental parameters, the separation efficiency and purity of cathode material reached 99 % and 99.7 %, respectively. Additionally, this method preserves both the structural integrity of the aluminum foil and the crystalline structure of the cathode materials, offering a new pathway for sustainable recycling of end-of-life LIBs.

Easily accessible linear and hyperbranched polyesters as solid polymer electrolytes

Herein we report synthesis, characterization, thermal properties, ionic conductivity and oxidative stability of novel linear and hyperbranched polyesters. Tri-acrylate ester of commercially available 1,1,1-Tris(hydroxymethyl)propane (M1) was used as the primary building block for the synthesis of linear and hyperbranched polymers. A3 + B2 type polycondensation between M1 and dithiols of two different chain lengths (C3, C6) by 100 % atom efficient thiol-acrylate Michael addition reaction, followed by consumption of the unreacted acrylate esters (in the linear or terminal units) with 1-butane thiol produced two hyperbranched polymer namely HB-P1 and HB-P2. For synthesis of linear analogues, one of the equivalent acrylate esters was reacted first with 1-butane thiol and the resulting di-acrylate monomer was polymerized with the C3 and C6-dithiols, producing linear polymers L-P1 and L-P2. All the polymers showed molecular weight (Mn) in the range of 5000–6000 gmol−1 with low dispersity. TGA analysis revealed sufficient thermal stability of the polymers for the application as solid polymer electrolyte. All the polymers are amorphous, showing only a glass transition in the range of ∼ -45 °C (C3 spacer) to −50 °C (C6 spacer) and no crystallization peak. In presence of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt the Tg increased by ∼ 10 °C. Solid polymer electrolytes were prepared by incorporating LiTFSI at a molar ratio of polymer carbonyl units to lithium of C=O/Li of 10 and ionic conductivity (σ) was evaluated by electrochemical impedance spectroscopy (EIS). Moderate values in the range of 10-7 S cm−1 were obtained at 25 °C with slightly higher values for the linear polymers. The ionic conductivity increased up to ∼ 2 orders of magnitude at higher temperatures. The oxidative stability of the polymer electrolytes against lithium-metal electrodes revealed onset potential for the first degradation in the range of 3.8 V, indicating moderate stability that might be suitable for testing applications in all-solid-state lithium-metal batteries using sulfur or lithium iron phosphate cathodes.

A facile route for the efficient leaching, recovery, and regeneration of lithium and iron from waste lithium iron phosphate cathode materials

The recycling of lithium iron phosphate power batteries that have exploded in retirement is urgent, but the focus and difficulty of the recycling is the effective recovery of lithium and iron elements in the cathode active material. In this study, the cathode sheets and other components of the lithium-ion batteries were obtained by pretreatment, and the cathode active material and the Al foil of the collector were recovered by stirring with dilute alkali solution (optimized conditions of alkali solution concentration 0.075 mol L-1, liquid–solid ratio 20 mL g−1, and stirring time 40 min). The H2SO4-H2O2 system was used to leach used lithium iron phosphate cathode powder, the leaching process conditions were optimized and the leaching mechanism was revealed. The leaching rates of Li and Fe elements reached 98.79 % and 94.97 %, respectively, at a H2SO4 concentration of 2.5 mol L-1, a H2O2 dosage of 6 mL, a liquid–solid ratio of 25 mL g−1, a leaching temperature of 60 °C and a leaching time of 60 min. The pH value was precisely adjusted in the chemical precipitation method to recover lithium and iron elements from cathode active material. The recovered products FePO4 and Li2CO3 were used as the precursors for the regeneration of LiFePO4 cathode material. The electrochemical performance of LiFePO4/C materials regenerated at 700 °C from the raw material with a lithium to iron molar ratio of 1.03:1 was relatively good, with a first discharge specific capacity of 160.1 mAh g-1 at 0.1 C, and a charge/discharge efficiency of 96.70 % for the first cycle. The good electrochemical performance was still maintained at a higher rate, with a capacity retention of 99.7 % after 100 cycles at 1 C.

Electric vehicle battery chemistry affects supply chain disruption vulnerabilities

We examine the relationship between electric vehicle battery chemistry and supply chain disruption vulnerability for four critical minerals: lithium, cobalt, nickel, and manganese. We compare the nickel manganese cobalt (NMC) and lithium iron phosphate (LFP) cathode chemistries by (1) mapping the supply chains for these four materials, (2) calculating a vulnerability index for each cathode chemistry for various focal countries and (3) using network flow optimization to bound uncertainties. World supply is currently vulnerable to disruptions in China for both chemistries: 80% [71% to 100%] of NMC cathodes and 92% [90% to 93%] of LFP cathodes include minerals that pass through China. NMC has additional risks due to concentrations of nickel, cobalt, and manganese in other countries. The combined vulnerability of multiple supply chain stages is substantially larger than at individual steps alone. Our results suggest that reducing risk requires addressing vulnerabilities across the entire battery supply chain.

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.

Low-cost and environmentally friendly physic-mechanical pre-treatments to recycle lithium iron phosphate cathodes

Recycling Lithium Iron Phosphate (LFP) batteries is challenging, as their low economic value hinders the profitability of full-scale processes. Optimized pre-treatments are crucial for the overall efficiency and economic profitability of recycling processes. This study explored chemicals-free physic-mechanical pre-treatment processes aimed to detach waste LFP cathodes (production scraps and end-of-life, EoL) from aluminium current collectors. The technical performances of ultrasounds (35 kHz, in water at 25 °C for 5, 15, 30 min), ball milling (840–1080 rpm for 8, 16, 24 min), and thermal treatment (30 min at 200, 250, 300, 350,°C) coupled with ball milling (840 rpm for 5 min) have been compared. Environmental impacts and economic cost were calculated based on energy demand. The highest separation efficiency achieved were 95 ± 5% for Li, 99 ± 6% for Fe, and 80 ± 3% for P in scrap cathodes, treated at 200 °C for 30 min and ball milled at 840 rpm for 5 min; 93 ± 15% for Li, 97 ± 21% for Fe and 82 ± 20% for P in EoL cathodes, treated at 250 °C for 30 min and ball milled. The global warming impacts were: 3.33 ± 0.55 kg CO2 eq/kg of detached cathode for scraps and 3.08 ± 0.25 kg CO2 eq/kg for EoL cathodes; the costs were 1.45 ± 0.24 €/kg of detached cathode for production scraps samples and 1.34 ± 0.11 €/kg for EOL samples. In conclusion, chemicals-free mechanical detachment was effective both for production scraps and EoL cathodes, while thermal treatment was especially beneficial for EoL cathodes, and reducing milling time improved the environmental impacts and costs of the pre-treatment processes.

Lithium iron phosphate cathode supported solid lithium batteries with dual composite solid electrolytes enabling high energy density and stable cyclability

In this research, we present a report on the fabrication of a Lithium iron phosphate (LFP) cathode using hierarchically structured composite electrolytes. The fabrication steps are rationally designed to involve different coating sequences, considering the requirements for the electrode/electrolyte interfaces. Two layers of composite solid electrolyte, consisting of poly(propylene carbonate) (PPC) + lithium bis (trifluoromethanesulfonyl)imide (LiTFSI) salt and poly(ethylene oxide) (PEO) + LiTFSI + Li7La3Zr2O12 (LLZTO), are employed as hierarchical structured composite electrolytes on the LFP cathode. Experimental results indicate that the optimal combination consists of a thinner PPC + LITFSI layer on the LFP cathode and a thicker PEO + LiTFSI + LLZTO facing Li metal. The Li-metal batteries, equipped with LFP supported hierarchical electrolytes exhibited an ultra-high specific capacity (~155 mAh g−1). Additionally, they demonstrated electrode polarization in the reduced form of −0.15 V, and an excellent cyclic stability with the retention capacity of 87.6 % even in 200 cycles. The ionic conductivity of the dual-layer electrolytes is achieved as high as 1.63–2.60 × 10−4 S cm−1 at ambient temperature. The impressive cycling performance demonstrated in this study is primarily attributed to the significance of the coating sequence in the design of dual composite solid electrolytes. The PPC + LiTFSI composite layer appears to function as a flexible filler on the LFP side. On the other hand, the PEO + LiTFSI + LLZTO composite layer, which faces the Li metal anode, not only provides excellent ionic conductivity but also serves as a barrier against the mechanical stress by the formation of Li-dendrite. The dual-layer electrolyte configuration, as demonstrated in this work, can be engineered to enable high energy density and stable cyclability of Li-metal batteries.