Solid-state Li Metal Batteries Research Articles

Anion Modulation: Enabling Highly Conductive Stable Polymer Electrolytes for Solid-State Li-Metal Batteries.

Solid polymer electrolytes (SPEs) are promising ionic conductors for developing high-specific-energy solid-state lithium metal batteries. However, developing SPEs with both high ionic conductivity and interfacial compatibility remains a challenge. Here, we propose a design concept of an anion-modulated polymer electrolyte (termed AMPE) for high-voltage Li metal batteries. Specifically, we design the AMPE by incorporating high-voltage-resistant and high charge density units with an anion receptor unit. The high-voltage-resistant and high charge density segments contribute to achieving a decent voltage tolerance of the polymer chains and ensure sufficient carrier ions. The anion receptor, represented by a boron-containing molecule, promotes the generation of free Li+ by dissociating anion-cation pairs. More importantly, the strong interaction between the electron-deficient B and the TFSI- in the matrix promotes the anion reduction to form a stable anion-derived mosaic-like solid electrolyte interphase on the Li-metal anode. As a result, the AMPE exhibits a high Li+ conductivity of 3.80×10-4 S cm-1 and effectively suppresses lithium dendrites, enabling an all-solid-state Li|AMPE|LiCoO2 cell to achieve a cycle life of 700 cycles at an operating voltage of 4.40 V. This design concept would inspire efforts to develop high-performance SPEs for high-specific-energy solid-state lithium metal batteries.

Isocyanurate‐Derivative Enables Highly Compatible Poly‐Dioxane Electrolyte for Dendrite‐Free Li Metal Batteries

AbstractThe Li+ transport kinetics and electrochemical stability of advanced solid‐state Li metal batteries (SLMBs) are seriously limited by the actual electrolyte compositions. Here, a novel polyether‐based electrolyte (PTGDOX) is presented through in situ co‐polymerization by integrating 1,3‐dioxane with a multifunctional 1,3,5‐triglycidyl isocyanurate additive. The isocyanurate group in PTGDOX not only provides abundant coordinating sites for Li+ transfer and restricts the movement of anions, but also prompts a beneficial inorganic‐rich solid electrolyte interface on the Li electrode. As a result, PTGDOX exhibits a remarkably increased ionic conductivity of 0.48 mS cm−1 at 30 °C and a reasonable Li‐ion transference number of 0.68, enabling the Li||Li symmetric cells to stably cycle for over 2000 h at 1 mAh cm−2. Meanwhile, the assembled Li||LiFePO4 exhibit a 97.4% capacity retention after 700 cycles at 3 C with excellent thermal stability. Moreover, PTGDOX also demonstrates excellent interfacial compatibility with high‐voltage LiNi0.8Co0.1Mn0.1O2 cathode. As such, this work provides a facile and accessible strategy for designing interface‐stable polymer electrolytes and achieving practical dendrite‐free SLMBs.

Rhombohedral Li1-xZr2-xSbx(PO4)3 electrolytes with improved Li+ conductivity for high-performance solid-state Li-metal battery

Recent studies on solid electrolytes have promoted the development of solid-state Li-metal batteries (SSLBs). The NASICON-type LiZr2(PO4)3 (LZP) electrolyte has received less attention due to its low conductivity and the existence of several crystal forms, which have impeded the development of LZP-based materials for SSLBs. Herein, Li1-xZr2-xSbx(PO4)3 (LZSP) ceramics were synthesized by solid-state method, and the cycle performances of symmetrical cell and Li-metal battery using LZSP electrolyte were characterized for the first time. The Sb5+ doping stabilizes the rhombohedral phase at room temperature and results in distortions in the ZrO6 octahedron and PO4 tetrahedron, which lead to variations of bond length and bond angle. The room temperature total conductivity of Li0.94Zr1.94Sb0.06(PO4)3 (LZSP-0.06) increased to 6.53 × 10−5 S·cm−1. This rise can be attributed to a reduction of the Li+ ions transport barrier originated from variations of bond length, bond angle and Raman vibrations mode. The Li/LZSP-0.06/Li symmetrical cell maintains a stable cycle duration of 670 h at a current density of 0.12 mA cm−2. The specific capacity of Li/LZSP-0.06/LiFePO4 battery reaches 140.1 mAh g−1 at 0.5C and the coulombic efficiency is 99.8 %. This battery maintains 80 % capacity after 105 cycles. These results provide reference significance for the research on SSLBs using LZP-based electrolytes. In general, the Li0.94Zr1.94Sb0.06(PO4)3 ceramic appears to be a promising solid electrolyte for SSLBs.

Constructing Donor–Acceptor-Linked COFs Electrolytes to Regulate Electron Density and Accelerate the Li+ Migration in Quasi-Solid-State Battery

HighlightsDonor–acceptor-linked covalent organic framework (COF)-based electrolyte can not only fulfill highly-selective Li+ conduction, but also offer a crucial opportunity to understand the role of electronic density in quasi-solid-state Li metal batteries.Donor–acceptor-linked COF electrolyte results in Li+ transference number 0.83, high ionic conductivity 6.7 × 10–4 S cm−1 and excellent cyclic ability in Li metal batteries.In situ characterizations, density functional theory calculation and time-of-flight secondary ion mass spectrometry are adopted to expound the mechanism of the rapid migration of Li+ in the “donor–acceptor” electrolyte system.

Interfacial challenges and recent advances of solid‐state lithium metal batteries

AbstractGrowing market demands on portable electronics, electric vehicles, and energy storage system calls for the development of high‐energy density lithium (Li) batteries. Li metal is considered as a promising anode material owing to their high capacity and low electrochemical potential. However, high reactivity of Li metal with conventional flammable liquid electrolytes easily forms Li dendrites, which may cause short‐circuit and even catching fire, obstructing the wide application of Li metal batteries. Although non−/less‐flammable solid electrolytes have replaced the conventional liquid electrolytes, solid‐state Li metal batteries (SSLMBs) suffer from lower Li+ conductivities, chemical/electrochemical incompatibilities toward Li metal, and inhomogeneous Li+ flux at the interfaces. Therefore, many researchers have devoted themselves to solve these problems. For a better understanding on the current issues and recent advances, this article provides (1) a review on various solid electrolytes with high Li+ conductivity and their interfacial issues in SSLMBs, and (2) recent progress in stabilization of the interface between the Li node and solid electrolytes, including an electrolyte modification (e.g., composition, additives) and introduction of an interlayer.

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.

Stable cycling of halide solid state electrolyte enabled by a dynamic layered solid electrolyte interphase between Li metal and Li3YCl4Br2

Halides are potential electrolytes for Li metal solid state batteries owing to their combination of high ionic conductivity, ductility and electrochemical stability against oxidation. However, their reactivity with the Li metal electrode may result in the formation of secondary compounds hindering their practical utility in terms of cycling performance as key indicator in battery operation. In this work, we investigate the high performance of symmetric cells with Li3YCl4Br2 halide and bare Li-metal electrode, able to withstand 1000 h of Li electrodeposition-dissolution with an overpotential as low as 46 mV. Through a comprehensive analysis employing physico-chemical and electrochemical characterizations, complemented by computational methodologies, we unravel the dynamics of the complex of the Li/halide interface and its evolution during cycling. The reactivity between Li3YCl4Br2 with metallic Li results in the reduction of the halide into LiCl, LiBr and Y metal. Surprisingly, during cycling, those secondary products from the reduction of the halide build a structured solid electrolyte interphase, containing a Y-rich electronic conductive and LiCl and LiBr ionic conductive layers. The particular chemistry and robustness of this solid electrolyte interphase exhibiting a mixed ionic and electronic conductivity appears to be responsible for the outstanding cycling stability.

The construction of concentration gradient inducing low resistance for Li7La3Zr2O12-based thermal battery

Ta-doped Li7La3Zr2O12 (LLZTO) electrolytes not only show considerable potentials in solid-state Li metal batteries, but also display great possibility in thermal battery working at elevated temperature with high security. However, the great resistance of the single cell has hindered its practical application for the large interfacial resistance and high Li+ transport pressure. Herein, a new effective approach to construct intense interface and distinct concentration gradient of O2– and Cl- through pre-discharge state at small current (PDS) was successfully employed to decline the resistance of the LLZTO-based thermal battery under thermal and electric field. The formed intense interface is conductive under the thermal field than the pristine poor contact at the interface. The obtained significant and distinct concentration gradient of O2– and Cl- under the joint function of thermal and electric field achieves larger effective charge transport after PDS, suggesting lower polarization and resistance of the single cell owing to the relaxing burden of Li+. Consequently, the resistance of the single cell decreases to 2.4 Ω from 3.7 Ω, coming with larger specific energy at 500 °C (from 444 Wh kg−1 to 1038 Wh kg−1). This work provides a facile strategy to decline the resistance of the battery through the construction of concentration gradient, which is also promising to be used for battery whose materials are sensitive to electric or thermal field.

Void Evolution on the Li-Solid Electrolyte Interface in Solid-State Batteries: A Parametric Study Under Varied Mechanical and Electrochemical Conditions

Void growth during the plating and stripping process is an important interfacial phenomenon that hinders the development of Li-metal solid-state batteries (SSBs) because it can potentially result in inter-component delamination or growth of Li dendrites. Behind the void growth is the complex interaction between electrochemistry and mechanics. Voids usually grow from micro- or nanoscale initial imperfections on the Li-solid electrolyte (SE) interface. It is, therefore, important to analyze the stress concentration at the initial void tips, which largely determines the growth/shrinking of the void as well as the consequent changes in the internal resistance and overall battery efficiency. Recently, the development of in situ operando experimental technology has enabled the electro-chemo-mechanical characterization of the void growth phenomenon on the Li-SE interface. In this study, we explore how voids in SSBs evolve with a multi-physics model in COMSOL Multiphysics. Based on this model, we perform a systematic parametric study in the space of the mechanical stack pressure and the applied current density. The simulation results show different deformation patterns and potential failure mechanisms under different combination of stack pressure and current density. To better understand the phenomena, we develop an analytical solution to understand the void deformation induced by the inhomogeneous Li-ion concentration field under stack pressure. This analytical approach offers a complementary and intuitive perspective on the mechanical aspect of our simulation findings. By combining the simulation and analytical solutions, we depict a phase diagram, in which we identify the “safe zone” that will not result in void growth. The new insights of this research hold the promise of guiding the development of stabilized SSB interfaces.

Giant dielectric ceramic of Li0.3Ti0.02Ni0.68O with abundant oxygen vacancies enabling high lithium-ion conductivity in composite solid-state electrolyte

The low ionic conductivity of composite solid-state electrolytes due to the lack of free Li-ions and Li dendrite growth induced by the low transference number seriously hinder their application. Herein, we find that the giant dielectric ceramic of Li0.3Ti0.02Ni0.68O (LTNO) with ultra-high dielectric constant can greatly promote the dissociation of Li salt to generate abundant movable Li-ions and realize a high room-temperature ionic conductivity (4.09 × 10–4 S cm−1) as well as a low activation energy (0.16 eV). The oxygen vacancies on the surface of LTNO can effectively immobilize the anions to achieve a high Li transference number (0.61). Furthermore, the enhanced dielectric properties of the composite electrolyte induce homogenous Li plating/stripping to suppress the growth of Li dendrites. As a result, the Li||Li symmetric cells exhibit long lifespan of 2400 h and 1150 h at 0.1 mA cm−2 and 0.2 mA cm−2, respectively. The Li||LiNi0.8Co0.1Mn0.1O2 solid-state full cells show a high capacity retention of 83% after 430 cycles at 2C. This work highlights the critical role of high dielectric property and oxygen defects of fillers in composite solid-state electrolytes, and provides a demonstration for the application of giant dielectric materials in solid-state Li metal batteries.

Flexible ionic liquid aided “LAGP in PVDF” quasi-solid-state electrolyte for high performance and stable Li metal batteries

The NASICON-type ceramic Li1·5Al0.5Ge1.5(PO4)3 (LAGP) electrolyte has been proposed as the most competitive candidates of electrolyte materials toward solid-state Li metal batteries (LMBs) by reason of its high ionic conductivity, cyclic stability under extreme temperatures and wide voltage window. However, poor interface contact, high interfacial resistance and intractable mechanical properties greatly limit its practical applications. In this work, an inorganic-polymer “LAGP in PVDF” quasi-solid-state electrolyte (QSSE) is developed via solution casting method, in which pyr14TFSI ionic liquid (IL) and LiTFSI are combined as functional wetting interface. Benefiting from the coherent interaction of LAGP nanoparticles incorporated into the polymer matrix, and inherent protection of IL, the overall performance of the optimized QSSE include thermal stability, dense structure, flexibility and electrochemical properties. The XRD, SEM, XPS tests demonstrate that the IL using as a solid/electrolyte modified interlayer can enhance Li+ transport, interfacial infiltration and homogenize lithium deposition. The LiFePO4|PL-25LAGP|Li solid-state battery presents an excellent circulation performance under ambient temperature, which displayed an initial discharge specific capacity of 146.8 mAh g−1 at 0.5C and capacity retention of 96.25 % after 150 cycles. The flexibility PL-LAGP CSE shows superior safety and greater development potential for the “LAGP in PVDF” composite electrolyte in solid state LMBs.

Resolving electrochemical incompatibility between LATP and Li-metal using tri-layer composite solid electrolyte approaches for solid-state Li-metal batteries

Due to its excellent air stability, low cost, and high ionic conductivity, Li1.3Al0.3Ti1.7(PO4)3 (LATP) has emerged as a viable option for solid-state lithium batteries (SSLBs). However, the irreversible reactivity between LATP and the Li-metal anode severely restrict its electrochemical performances. Herein, a tri-layer composite solid electrolyte (t-CSE1) comprised of LATP, PVDF-HFP, SN, and LiTFSI as the middle layer and Al-LLZO, PVDF-HFP, SN, and LiTFSI as the top and bottom layers is prepared to solve these prominent limitations since Al-LLZO is stable towards Li metal anode. As a result, the lithium plating-stripping lifetimes for the Li||Li symmetry cell is prolonged from 550 to 1950 h at 0.1 mA cm−2 without any residual redox products. In addition, the as-prepared t-CSE1 exhibited excellent ionic conductivity (ca. 6.46 × 10−4 S cm−1 at room temperature), high lithium-ion transference number (ca. 0.69) and remarkable mechanical strength (ca. 12.82 MPa). Furthermore, the Li||LiFePO4 (Li||LFP) full cell achieved significantly improved long cycle performances of 500 cycles with 80.31 % capacity retention and 99.93 % average coulombic efficiency at 0.2C. Moreover, the Li||LFP full cell showed 85.53 % capacity retention and 99.95 % coulombic efficiency after 200 cycles at 0.5C at room temperature. Thus, this study gives an insight into how to prevent the electrochemical incompatibility between LATP and Li metal for SSLBs.

Polymer solid electrolytes with ultra-stable cycles and high-capacity retention for all-solid-state Li-metal battery

Polymer electrolytes have become widely popular on account of their low expenses, reduced weight, simple processing, and excellent safety features. However, polymer electrolytes have yet to find use in commercial batteries because of their limited mechanical durability and poor ionic conductivity. In this paper, an ultra-stable cycles and interfaces blending polymer electrolyte (BPE) suitable for all solid-state Li metal batteries was prepared by blending three polymers: polymethyl methacrylate (PMMA), polyvinylidene fluoride hexafluoropropylene (PVDF-HFP), and polyethylene oxide (PEO). Microstructure characterization showed numerous amorphous areas with strong interfacial strength of the BPE. The BPE3 exhibited a maximum of 15.65 MPa in tensile strength. BPE2 have excellent electrochemical performance, such as wide electrochemical windows (up to 4.7 V vs Li/Li+), high lithium ion transference numbers (up to 0.75), high ion conductivity (up to 1.87 × 10-4 S cm−1 at 60 °C), and excellent interface stability. By assembling all state-solid LiFePO4/BPE2/Li batteries for electrochemical testing, BPE2 exhibit high electrochemical characteristics. BPE2 discharge specific capacity is as high as 154.7 mAh g−1 at 1C. The BPE2 underwent 200 cycles at 0.5C and 400 cycles at 1C, with capacity retention rates of 95.7 % and 96.6 %, respectively. BPE is a promising electrolyte candidate for flexible lithium metal batteries.

Ultrathin, Mechanically Durable, and Scalable Polymer-in-Salt Solid Electrolyte for High-Rate Lithium Metal Batteries.

Polymer-in-salt solid-state electrolytes (PIS SSEs) are emerging for high room-temperature ionic conductivity and facile handling, but suffer from poor mechanical durability and large thickness. Here, Al2O3-coated PE (PE/AO) separators are proposed as robust and large-scale substrates to trim the thickness of PIS SSEs without compromising mechanical durability. Various characterizations unravel that introducing Al2O3 coating on PE separators efficiently improves the wettability, thermal stability, and Li-dendrite resistance of PIS SSEs. The resulting PE/AO@PIS demonstrates ultra-small thickness (25µm), exceptional mechanical durability (55.1MPa), high decomposition temperature (330°C), and favorable ionic conductivity (0.12 mS cm-1 at 25°C). Consequently, the symmetrical Li cells remain stable at 0.1mA cm-2 for 3000 h, without Li dendrite formation. Besides, the LiFePO4|Li full cells showcase excellent rate capability (131.0 mAh g-1 at 10C) and cyclability (93.6% capacity retention at 2C after 400 cycles), and high-mass-loading performance (7.5mg cm-2). Moreover, the PE/AO@PIS can also pair with nickel-rich layered oxides (NCM811 and NCM9055), showing a remarkable specific capacity of 165.3 and 175.4 mAh g-1 at 0.2C after 100 cycles, respectively. This work presents an effective large-scale preparation approach for mechanically durable and ultrathin PIS SSEs, driving their practical applications for next-generation solid-state Li-metal batteries.

Li Stripping Behavior of Anode‐Free Solid‐State Batteries Under Intermittent‐Current Discharge Conditions

AbstractAnode‐free manufacturing holds promise to enable high energy densities and lower Lithium (Li)‐metal solid‐state batteries (LMSSBs). Nevertheless, in contrast to thick Li foil (>50 µm), the stripping capacity of in situ‐formed Li (10–30 µm) is limited due to diminished creep flow, resulting in reduced accessible capacity. This study explores the correlation between stripping capacity and surface roughness of garnet Li7La3Zr2O12 (LLZO) solid electrolyte. The results reveal that stripping capacity can be enhanced through the surface modification of solid electrolytes. Additionally, this study scrutinizes the stripping behavior of in situ Li under intermittent‐current discharge conditions, which are more relevant to the operational conditions of electric vehicles (EVs). It is demonstrated that, when compared to constant‐current stripping, intermittent‐current stripping effectively suppresses void formation and enhances the stripping capacity of in situ Li by 40%. It is considered that the intermittent current inhibits the accumulation of Li vacancies, thereby delaying the void formation. These findings provide valuable insights into the development of high‐performance anode‐free LMSSBs for EVs.

Effects of H2O on Improving the Performance of a Solid Composite Electrolyte Fabricated via an Air-Processable Technique.

Inert atmosphere is normally necessary for fabrication of solid composite electrolytes (SCEs) as a crucial part of solid-state Li-metal batteries in order to avoid undesirable reactions induced by ambient moisture. Herein, we developed an air-processable technique to fabricate SCEs by employing LiCF3SO3 (LiOTf) as the Li salt, which was combined with Li6.4La3Zr1.4Ta0.6O12 (LLZTO) as the fast Li-conductor and polyvinylidene difluoroethylene/polyvinyl acetate (PVDF/PVAC) as the polymer matrix. With the assistance of trace H2O dissolved in electrolyte solution, the room-temperature Li+ conductivity of the obtained aSCE reached as high as 5.09 × 10-4 S cm-1, which was over 3 orders of magnitude higher than that of the one (iSCE, 1.93 × 10-7 S cm-1) cast by the electrolyte solution prepared in an inert atmosphere. The theoretical calculation results reveal that the oxygen atom of H2O exhibits a high propensity to interact with the Li atom in LiOTf (Li···O), thereby establishing a hydrogen bond with the oxygen atom (H···O) in N,N-dimethylformamide (solvent). Such interactions promoted the dissociation of LiOTf and led to the formation of uniform Li+ transportation channels. Simultaneously, the composition distribution was also altered, resulting in a smoother surface of aSCE and lowered crystallinity of PVDF. On this basis, the LiOTf/LLZTO/PVDF/PVAC solution at 60 °C was directly coated onto the surface of the LiFePO4 (LFP) cathode to fabricate the LFP-aSCE film after drying in an oven. The assembled LFP-aSCE/Li battery wetted by trace sulfolane exhibited an initial Coulombic efficiency of 94.7% and a capacity retention rate of up to 96% at 0.2 C (137 mAh g-1) after 180 cycles and a high capacity of 143.7 mAh g-1 at 0.5 C (150 cycles). Overall, this work could pave the way for the facile fabrication of solid electrolytes.

Rationally coordinating polymer enabling effective Li-ion percolation network in composite electrolyte for solid-state Li-metal batteries

The sluggish lithium-ion mobility and inferior electrolyte/electrode interfacial compatibility of composite solid electrolytes greatly hinder the practical application of solid-state lithium-metal batteries. Here, a novel composite polymer electrolyte (CPE) with effective Li+ percolation network is synthesized based on single-ion conductive polymer lithiated polyvinyl formal (LiPVFM) and garnet Li6.4La3Zr2Ga0.2O12 (LLZGO) nanoparticles. The supramolecular interaction between the branched hydroxyl in LiPVFM and the lattice oxygen in LLZGO fillers endows CPE with a continuous percolation structure and improved toughness. Meanwhile, the rational O-Li+ coordination in the LiPVFM random polymer significantly enhances Li+ transfer within the percolation network. Therefore, this as-prepared CPE presents a lithium-ion transference number of 0.75 and an ionic conductivity of 0.527 mS cm−1 at 30 °C, alongside an electrochemical stability window of 4.6 V and a substantial suppression of Li dendrite growth. In addition, ultra-stable interfaces between this CPE and high-voltage LiNi0.6Mn0.2Co0.2O2 (NMC) cathode during cycling can be determined by in-situ electrochemical impedance spectroscopy and in-situ differential electrochemical mass spectrometry characterization. This work is a new exploration for the structural design of CPEs and highlights the importance of “rational coordination” of alkali cation in solid batteries.

A Stable Matrix Assisting Highly Compatible and Maintainable Lithium-Garnet Interface for Solid-State Batteries.

Solid-state Li metal batteries (SSLMBs) are attractive due to their capability to simultaneously offer high energy density and high-level safety when combining Li metal anodes, solid-state electrolytes (SSEs), and high-voltage cathodes together. However, SSLMBs may well incur short circuits caused by Li dendrites penetrations, which mainly originate from the instability and poor contact between Li metal and SSEs. Herein, by taking full advantage of the reaction products of Li and Li1.3Al0.3Ti1.7(PO4)3 (LATP), a lithium-LATP composite anode (Li-LATP) is obtained, in which a stable matrix is formed to enhance the contact between Li and the garnet-type SSEs, alleviating the volume change and preserving an intact interface during the charge/discharge process. Consequently, the Li-LATP/garnet/Li-LATP symmetric cell displays a fairly low interfacial resistance of 6Ωcm2 and stable cycling performance for over 2500h with a low overpotential. Furthermore, the LiCoO2/garnet/Li-LATP full cell also shows a high discharge capacity of 159mAhg-1 and great cycling performance.

Polyethylene oxide-Based solid electrolytes with fast Li-ion transport channels constructed from 2D montmorillonite for solid-state lithium-metal batteries

Polyethylene oxide (PEO)-based solid-state electrolytes (SSEs) typically struggle with poor ionic conductivity, low lithium (Li)-ion transference number, and narrow electrochemical window. For overcoming these drawbacks, we designed a promising composite SSE (CSSE), i.e., a Li-containing ionic liquid (LiIL) was inserted into the Li-montmorillonite (LiMNT) layered structure to form an active filler (LiIL@LiMNT), involving two-dimensional (2D) fast transport channels of Li-ion inside PEO electrolyte. Benefitting from an enhancement of the 2D Li-ion transport channels, the obtained CSSE exhibited an excellent ion conductivity of 1.38 × 10−4 S cm−1 at 30 °C as well as a satisfactory Li-ion transference number (0.38). A Li symmetric battery with the CSSE exhibited a steady cycle for 3000 h with 0.2 mA cm−2 at 60 °C. Under the rate of 0.5C at 60 °C, the solid-state Li-metal batteries (SSLMBs) assembled with LiFePO4 and LiNi0.33Co0.33Mn0.33O2 cathodes maintained a considerable reversible capacity after 400 and 100 cycles, respectively. The assembled SSLMB also achieved a satisfactory performance at 40 °C. The 2D active filler prepared in this work forms efficient 2D Li-ion transport channels inside the CSSE while maintaining a tight interfacial contact with electrodes, which is crucial to achieve a superior performance for CSSEs. This strategy of constructing 2D ion transport channels in polymer electrolytes also provides another way for the design of other CSSEs.

Understanding the complexities of Li metal for solid-state Li-metal batteries

Understanding the complexities of Li metal for solid-state Li-metal batteries