Solid-state Lithium Metal Batteries Research Articles

Molecular Control Based on Electrostatically Driven Modification for Solid-State Lithium Metal Batteries.

With the rapid development of energy vehicles, the demand for high-safety and high-energy-density battery systems, such as solid-state lithium metal batteries, is becoming increasingly urgent. Polyethylene oxide (PEO), as a commonly used electrolyte in solid-state batteries, has the advantages of easy processing and good interface compatibility but also faces the issue of poor ionic conductivity. In this study, we have enhanced the mechanical properties and ion conductivity of PEO electrolytes significantly, stabilizing electrochemical cycling, utilizing positively charged MXene as a modifying material for PEO solid electrolytes and leveraging stronger electrostatic forces. With these enhanced properties, the modified solid electrolyte in Li/Li cells demonstrates excellent cycling stability of over 430 h at 0.1 mA cm-2. Furthermore, the Li/LiFePO4 cells show excellent cycling performance, and the capacity retention rate is 92.1%.

High-Performance Solid-State Lithium Metal Batteries of Garnet/Polymer Composite Thin-Film Electrolyte with Domain-Limited Ion Transport Pathways.

The integrated approach of interfacial engineering and composite electrolytes is crucial for the market application of Li metal batteries (LMBs). A 22 μm thin-film type polymer/Li6.4La3Zr1.4Ta0.6O12 (LLZTO) composite solid-state electrolyte (LPCE) was designed that combines fast ion conduction and stable interfacial evolution, enhancing lithium metal interface stability and cycling performance. The ether-based molecular coordination groups/clusters formed by triethylene glycol dimethyl ether (TGDE) and anions facilitated the movement of Li+ between the polymer chain segments. These specific coordination clusters significantly "constrained" the interaction between anions and Li+, inducing the anions to follow the clusters to the Li metal and preferentially participate in solid electrolyte interface (SEI) derivatization. The inorganic salt-rich gradient SEI modulates Li+ deposition and inhibits uncontrolled dendrite growth, achieving stable cycling of Li symmetric cell at 0.2 mA cm-2 for over 2000 h. Furthermore, the Li||NCM811 cell at a rate of 0.1 C exhibits an initial discharge capacity of 194.5 mAh g-1, maintaining a capacity retention rate of over 90% after 500 cycles. This work demonstrates the importance of domain-limited ion clusters in ion transport and interfacial evolution, providing a perspective for solid-state LMBs.

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.

In Situ Optical Observation of Lithium Dendrite Pattern in Solid Polymer Electrolytes.

Solid polymer electrolytes (SPEs) have been treated as a viable solution to build high-performance solid-state lithium metal batteries (SSLMBs) at the industrial level, bypassing the safety and energy density dilemmas experienced by today's lithium-ion battery technology. To promote a wider application of SPEs-based SSLMBs, the chemical and electrochemical characteristics of lithium metal (Li°) electrode in SPEs have to be clearly elucidated. In this work, the morphological evolution of Li° electrode in the SPEs-based SSLMBs is comprehensively investigated, via a customized electrochemical cell allowing optical microscopic analyses. The results demonstrate that differing from inorganic solid electrolytes, the elastic feature of SPEs eliminates the "memory effect" of the dendrite formation, in which the previously formed dendrites can be dissolved and the resulting space can be simultaneously occupied by electrolyte components, instead of leaving for a second-round growth of Li° dendrites. Furthermore, the largely increased electronic conductivities of the as-formed interphases between Li° electrode and SPEs are found to be responsible for the notoriously soft short-circuit behavior observed during cycling. These findings bring a fresh understanding of the formation and evolution of lithium dendrites in SPE-based cells, which are vital for improving the long-term stability of SSLMBs and other related high-energy battery systems.

Efficient sodium ion transport enhanced by anionophilic sites in polymer-supported plastic crystal electrolyte for high performance sodium metal anode

The design of sodium metal batteries (SMBs) is seen as an excellent solution to solve the request of next-generation energy storage technologies with high energy density, high safety, low cost, and environmental friendliness. However, the direct use of sodium metal as an anode produces the dendritic sodium, which harms the normal operation of battery. Inspired by solid-state lithium metal batteries, solid-state electrolyte (SSE) designed for SMBs effectively solves this shortcoming. Herein, a novel SSE with mask-based polymer membrane supporting plastic crystal electrolyte with ZIF-67 (MPPZ) is designed. The experimental results and density functional theory (DFT) calculations indicate that the addition of ZIF-67 in MPPZ electrolyte availably fixes TFSI− and achieves high Na+ transference number. Additionally, a protective layer of NaF is formed in situ on the surface of sodium metal to avoid side reactions between Na and MPPZ electrolyte while further guide the uniform deposition of Na. Accordingly, Na||Na symmetric battery with NaF-coated Na metal anode and MPPZ electrolyte has a stable deposition and stripping of Na for 3000 h. The assembled room temperature solid-state sodium-sulfur battery (RTSSSSB) exhibits a good cycle stability. This study provides an innovative thinking for the construction of high performance dendrite-free SMBs.

Silica-reinforced Functional Composite Polymer Electrolyte with High Electrochemical Compatibility for Solid-State Lithium Metal Battery

Silica-reinforced Functional Composite Polymer Electrolyte with High Electrochemical Compatibility for Solid-State Lithium Metal Battery

Surface-functionalized metal–organic framework with high specific surface area optimizing composite solid electrolyte for high-performance solid-state lithium metal batteries

Surface-functionalized metal–organic framework with high specific surface area optimizing composite solid electrolyte for high-performance solid-state lithium metal batteries

A near-single-ion conducting polymer-in-ceramic electrolyte for solid-state lithium metal batteries with superior cycle stability and rate capability

Composite solid-state electrolytes (CSE) represent a promising alternative to conventional porous separators and organic liquid electrolyte systems in commercialized lithium metal battery (LMBs), offering effective dendrite suppression, high interfacial compatibility and enhanced cycle life. This study introduces a polymer-in-ceramic electrolyte, which is synthesized by blending perovskite-type inorganic electrolyte Li1.5La1.5TeO6 (LLTeO) with polymethyl methacrylate (PMMA) and polyvinylidene fluoride (PVDF), denoted as PMMA/PVDF-LLTeO. The resulting CSE features a dense, non-porous structure, high mechanical strength, excellent thermal stability, and a broad electrochemical window. Notably, with the incorporation of a high ceramic filler content (up to 70 %), the CSE promotes a hybrid ion transport mechanism, yielding a near-single-ion conducting behavior with an ion transference number of 0.833, and a high elastic modulus of approximately 1 GPa. These attributes collectively contribute to the suppression of dendrite growth, as analyzed through multiphysics-based simulations. Li//Li symmetric cells using PMMA/PVDF-LLTeO-70 exhibit robust lithium stripping-plating stability, with a critical current density of 0.45 mA cm−2. Furthermore, the corresponding Li//LiFePO4 cells exhibit superior rate performance and cyclic stability, achieving over 150 cycles with a capacity retention rate of 92.2 % at high temperatures (60 °C). This research highlights the potential of the proposed CSE with high-temperature applications, significantly improving the safety and performance of LMBs

A Quasi-Solid-State Polymer Lithium-Metal Battery with Minimal Excess Lithium, Ultrathin Separator, and High-Mass Loading NMC811 Cathode.

Solid-state batteries with lithium metal anodes are considered the next major technology leap with respect to today's lithium-ion batteries, as they promise a significant increase in energy density. Expectations for solid-state batteries from the automotive and aviation sectors are high, but their implementation in industrial production remains challenging. Here, we report a solid-state lithium-metal battery enabled by a polymer electrolyte consisting of a poly(DMADAFSI) cationic polymer and LiFSI in Pyr13FSI as plasticizer. The polymer electrolyte is infiltrated and solidified in the pores of a commercial LiNi0.8Mn0.1Co0.1O2 (NMC811) cathode with up to 2.8 mAh cm-2 nominal areal capacity and in the pores of a 25 μm thin commercial polypropylene separator. Cathode and separator are finally laminated into a cell in combination with a commercial 20 μm thin lithium metal anode. Our demonstration of a solid-state polymer battery cycling at full nominal capacity employing exclusively commercially available components available at industrial scale represents a critical step forward toward the commercialization of a competitive all-solid-state battery technology.

Unveiling the Role of Filler Characteristics in Enhancing the High-Voltage Performance of Succinonitrile-Based Solid-State Lithium-Metal Batteries.

For exploiting high-energy lithium-metal batteries, it is of utmost importance to develop electrolytes that possess exceptional ionic conductivity and an extensive electrochemical stability range. In this study, 3D PAN nanofibers and polymer electrolytes incorporating various inorganic fillers with different Lewis acid-base properties were fabricated. PAN@Al-SSE exhibits exceptional ionic conductivity (0.48 mS·cm-2 at room temperature), a high Li+ transference number (0.41), and a wide electrochemical window (5.26 V). The device is able to operate stably in Li symmetric cells for more than 1000 h under a potential of 0.03 V under a current density of 0.2 mA·cm-2. Besides, the groundbreaking technology equips high-voltage Li-LiCoO2 solid-state batteries with exceptional cycling performance (91.3% and 82.1% retention after 100 cycles at 0.2 and 1 C, respectively) at room temperature. Mechanistic studies indicate that the Lewis acid-base properties of surface fillers are instrumental and crucial to form a stable solid-electrolyte interphase layer. γ-Al2O3, in particular, with more Lewis acid sites, ensures the dissociation of LiTFSI and induces the excessive decomposition and polymerization of succinonitrile. There exists an equilibrium effect between dissociation and polymerization in a succinonitrile-based solid electrolyte, which plays a critical role in improving the manifestation of succinonitrile-based solid-state lithium cells, especially under high-voltage conditions.

Single‐Crystalline LiMg Alloy Anode for Deep Cycling All Solid State Lithium Metal Batteries

AbstractAll solid state lithium metal batteries (ASSLMBs) with enhanced energy density has driven the exploration of Li‐alloy anodes such as Li‐Mg alloy owing to its solid‐solution structure and high theoretical specific capacity. But the Li atom diffusion limitation on Li‐Mg electrode surface further leads to sluggish atoms transport dynamics. Herein, single‐crystalline (110)‐oriented Li0.9Mg0.1 (denoted as LiMg(110)) anode is obtained by a tailored melt‐annealing procedure to tackle the above issues. Theoretical analyses and experimental results demonstrate that the crystallographic structural (110) orientation of LiMg anode can facilitate Li atom diffusion and guarantee the electrode stability during deep cycling. As a result, the LiMg(110) electrode exhibits longer cycle life with lower overpotential than polycrystalline LiMg at high current densities and areal capacities in symmetric cells. A critical current density (CCD) at the forefront of 2.5 mA cm−2 is achieved in Li3InCl6 (LIC) solid‐state system. The ASSLMB with high areal capacity (3.8 mAh cm−2), high current density (0.76 mA cm−2), and low negative/positive capacity N/P ratio (2.14) achieves exceptional cyclability over 160 cycles. The outcomes highlight a promising crystallographic regulation strategy toward practical applications of high‐performance lithium metal batteries.

Borophosphate glass based electrolyte composite for high lithium ionic conductivity

The application requirements of solid-state lithium (Li) metal batteries are satisfied by the ionic conductivity of composite solid-state electrolytes, attributed to their minimal interfacial resistance. Herein, composite solid electrolytes were obtained by mixing a crystalline Li0.5La0.5TiO3 (LLTO) perovskite with different amount of 47Li2O-30B2O3-23P2O5 (LBP) glass phase. The results show that the crystal phase of the composite samples exhibit a tetragonal perovskite structure with a P4/mmm space group. Frequency dependent AC conductivity shows that composite containing 1 % LBP glass avoids the phenomenon of charge carrier blocking at low frequency and low temperature at the same time. The room temperature maximum total ionic conductivity was obtained for sample with 0.5 % LBP glass presenting a conductivity that is almost three times higher than that of pure LLTO. The factors influencing ionic conductivity are not only grain morphology and size, and activation energy, but also lithium content, and entropic effects contribute to the facility or difficulty with which Li+ can migrate into the LLTO solid electrolyte.

Stabilizing the Bilateral Interfaces by a PVDF-Based Double-Layer Solid Composite Electrolyte with a Relieved Dehydrofluorination Effect for Solid-State Lithium Metal Batteries.

The dehydrofluorination effect of poly(vinylidene fluoride) (PVDF) induced by ceramic fillers with an alkaline surface compromises the comprehensive properties of the solid composite electrolyte (SCE) and leads to the deficient performance of the solid-state lithium metal batteries (SLMBs). In this work, a unique PVDF-based double-layer solid electrolyte was fabricated, which consisted of a Li6.4La3Zr1.4Ta0.6O12 (LLZTO)-filled SCE with poly(acrylic acid) (PAA) as an alkalinity-scavenging agent in contact with the Li anode, and another SCE with lithium difluoro(oxalato)borate (LiDFOB) as a film-formation additive facing the cathode. It is found that a moderate amount of PAA relieves the dehydrofluorination degree of the PVDF matrix and improves the Li plating/stripping reversibility, and the addition of LiDFOB is involved in the formation of a stable passivation film on the cathode. Consequently, the resultant double-layer SCE holds favorable overall properties, especially being well-compatible with both electrodes, endowing the SLMBs with superior cycle and rate performance at room temperature.

Fabrication of Scalable Covalent Organic Framework Membrane-based Electrolytes for Solid-State Lithium Metal Batteries.

The conventional covalent organic framework (COF)-based electrolytes with tailored ionic conducting behaviors are typically fabricated in the powder morphology, requiring further compaction procedures to operate as solid electrolyte tablets, which hinders the large-scale manufacturing of COF materials. In this study, we present a feasible electrospinning strategy to prepare scalable, self-supporting COF membranes (COMs) that feature a rigid COF skeleton bonded with flexible, lithiophilic polyethylene glycol (PEG) chains, forming an ion conduction network for Li+ transport. The resulting PEG-COM electrolytes exhibit enhanced dendrite inhibition and high ionic conductivity of 0.153 mS cm-1 at 30 °C. The improved Li+ conduction in PEG-COM electrolytes stems from the loose ion pairing in the structure and the production of higher free Li+ content, as confirmed by solid-state 7Li NMR experiments. These changes in the local microenvironment of Li+ facilitate its directional movement within the COM pores. Consequently, solid-state symmetrical Li|Li, Li|LFP, and pouch cells demonstrate excellent electrochemical performance at 60 °C. This strategy offers a universal approach for constructing scalable COM-based electrolytes, thereby broadening the practical applications of COFs in solid-state lithium metal batteries.

Boosting Li-Ion Conductivity of Fluoride Solid Electrolyte by Low-Temperature Molten Salt Ablation and Particle Boundary Doping.

Halide solid electrolytes (SEs) are attracting great attention, owing to their high ionic conductivity and excellent high-voltage compatibility. However, severe moisture sensitivity, poor thermal stability, and instability at the lithium metal anode interface with chloride and bromide SEs retard their applications in solid-state lithium metal batteries. Fluoride SEs are expected to solve these problems, but they are now plagued by inadequate room-temperature (RT) ionic conductivity. Herein, a low-temperature molten salt (LiCl+1.33AlCl3) ablation method is proposed to enhance the ionic conductivity of monoclinic Li3GaF6 by particle boundary doping. The RT ionic conductivity of Li3GaF6 is correspondingly increased by 2 orders of magnitude, and the conductivity reaches 10-4 S cm-1 at 60 °C. The improved ionic conductivity benefits from the enhancement of interfacial ion transport, with the formation of more conductive chlorine-doped Li3GaF6-xClx and in situ binder LiAlCl4 to cement surrounding nanoparticles. The as-synthesized Li3GaF6 demonstrates outstanding humidity tolerance without conductivity degradation after exposure to a relative humidity of up to 35%. It also exhibits the widest electrochemical stability window experimentally (close to 6 V) compared with other state-of-the-art SEs. The solid-state Li/Li3GaF6/LiFePO4 cell with a stable Li+-conductive polymer interface is successfully driven for at least 200 cycles at 0.5C. Our study provides a solution to various chemical and electrochemical stability issues encountered by the halide SE family.

Ionic solid-like conductor-assisted polymer electrolytes for solid-state lithium metal batteries

Ionic solid-like conductor-assisted polymer electrolytes for solid-state lithium metal batteries

Construction of composite lithium with high adhesion work and fast ionic conductivity by black phosphorus for solid-state lithium batteries

Li6.4La3Zr1.4Ta0.6O12 (LLZTO) based solid-state lithium metal batteries (SSLMBs) have a broad application prospect because of the nonflammable nature as well as the high energy density. However, the loose contact and the contact degradation of Li/LLZTO in the stripping process result in the serious lithium dendrites growth. Herein, these issues are addressed by a composite lithium anode (CLA), which is prepared through the reaction between black phosphorus and molten lithium. In comparison to pure lithium, a higher adhesion work (722.67 mJ m−2) and Li+ diffusion coefficient (2.45×10−12 cm2 s−1) are achieved for CLA, thus assuring the intimate interfacial contact of CLA/LLZTO interface during the lithium stripping process. As a result, a small interfacial resistance of 3.7 Ω cm2, a high critical current density of 1.5 mA cm−2, and extra-long cycle life of 8200 h at 0.3 mA cm−2 are achieved for CLA symmetric cell at 25 ºC. More importantly, the full cell coupled with high mass loading LiFePO4 cathode (10.6 mg cm−2) still shows a large discharge capacity of 156.3 mAh g−1 and cycles stably at 25 ºC. This work provides an alternative approach to develop the long lifespan and high capacity of SSLMBs.

The Regulation of Solid Electrolyte Interphase on Composite Lithium Anodes in Solid-State Batteries.

Solid-state lithium metal batteries (SSLMBs) with solid polymer electrolyte (SPE) are highly promising for next-generation energy storage due to their enhanced safety and energy density. However, the stability of the solid electrolyte interphase (SEI) on the lithium metal/SPE interface is a major challenge, as continuous SEI degradation and regeneration during cycling lead to capacity fading. This article investigates the SEI formation on lithium anodes (l-SEI) and composite lithium anodes (c-SEI) in solid-state lithium metal batteries. The composite anodes form a uniform Li2S-rich inorganic SEI layer and a thinner organic SEI layer, effectively passivating the interface for enhanced cycling stability. Specifically, the full cells with c-SEI anodes sustain over 400 cycles at 0.5 C under a high areal capacity of 2.0 mAh cm-2. Moreover, the reversible high-loading solid-state pouch cells exhibit exceptional safety even after curling and cutting. These findings offer valuable insights into developing composite electrodes with robust SEI for solid-state polymer-based lithium metal batteries.

Super SEI-Forming Anion for Enhanced Interfacial Stability in Solid-State Lithium Metal Batteries.

The extremely high chemical reactivity of lithium metal (Li°) electrodes and its enormous volume change during repetitive cycles cause continuous interfacial degradations in prevailing organic electrolytes, thus deteriorating the cycling performances of rechargeable lithium metal batteries (LMBs). Herein, departing from traditional wisdom on the design of electrolyte components, a super SEI-forming anion (SSA), as an efficient percussor for building stable interphases on Li° electrode, is proposed. Comprehensive investigations related to the unique anion chemistry of SSA reveal that the sulfonate and polyfluoroalkyl functionalities synergistically contribute to uniform spatial distributions of designer interfacial species, greatly improving the surface coverage property and conformal ability of the resulting interphases. Consequently, the incorporation of SSA leads to significant improvements in the cyclability of Li° electrode (exceeding 575 mAh cm-2 before failure) and the corresponding rechargeable Li°||LiFePO4 cells [a five-time increase in lifespan as compared to the benchmark cell with the popular SEI-forming anion bis(fluorosulfonyl)imide (FSI)]. The present work offers a paradigm shift to tame the notorious interfacial issues via upgraded anion chemistry, which can promote the practical development of rechargeable LMBs and other kinds of metal batteries.

Understanding Li6.24La3Zr2Al0.24O11.98 effect on poly(ionic liquid)-based electrolytes for high voltage solid-state lithium batteries working at room temperature

Hybrid electrolytes composed of poly(ionic liquid), ionic liquids (ILs), and fillers are very promising candidates for solid-state lithium metal batteries (SSLMBs). However, a significant knowledge gap in the field of hybrid electrolytes lies in the understanding of filler effect on properties and performance. Herein, we have investigated hybrid electrolytes based on poly(diallyldimethylammonium) bis(fluorosulfonyl)imide (PDDA-FSI), N-propyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide (PYR13FSI), lithium bis(fluorosulfonyl)imide (LiFSI) and different loadings (from 0 to 19.2 vol%) of Li6.24La3Zr2Al0.24O11.98 (Al-LLZO) particles. All the electrolytes present a homogeneous morphology and excellent thermal stability. Moreover, our results demonstrate that Al-LLZO particles do not contribute to the ionic conductivity of the hybrid electrolytes. A 2.6 vol% of Al-LLZO led to the excellent performance in full cells at room temperature. Surprisingly, the battery performance was not correlated with the transport properties. Instead, this study found out a mechanical-performance relationship, which follows a master equation: t = A (−12.48 (1-e(1.53x10-4σy))) / P that enables to correlate the effect Al-LLZO particles on the cell performance, and predicts, for the first time, the lifetime of the battery through the mechanical properties.