Solvation-Tailored PVDF-Based Solid-State Electrolyte for High-Voltage Lithium Metal Batteries.

The development of lithium metal batteries (LMBs) relies on advanced solid-state electrolytes. Solid-state polymer electrolytes (SPEs) offer advantages such as cost-effectiveness, mechanical flexibility, and light weight; however, their practical use is hindered by limited ionic conductivity, narrow electrochemical stability window, and suboptimal cycling performance. Herein, we present a class of weakly-solvating dinitrile-based SPEs (DBSPEs) composed of a poly(2-(2-(2-methoxyethoxy)ethoxy)ethyl acrylate) network coupled with structurally modulated dinitrile solvents. Through rationale molecular engineering, the synergistic combination of short ethylene oxide side chains and weakly coordinating dinitrile solvents enables weak hybrid solvation of lithium ions, thereby facilitating rapid ion migration and uniform lithium deposition. The optimized DBSPE-2 exhibits a high ionic conductivity (∼2.2×10-3Scm-1) and an extremely wide electrochemical window (∼5.7V). Notably, the Li||DBSPE-2||Li symmetric cell yields stable lithium plating/stripping over 6900 h at 0.1mAcm⁻2 under ambient conditions (26°C). When paired with LiFePO₄ in a full cell, the LMBs deliver a superior fast-charging capability, realizing 80.78% capacity retention after 1500 cycles at 2.0 C rate. This work provides fundamental insights into the solvation structure and accordingly realizes long-lasting LMBs with weak solvents.

An ultrathin polymer-based solid-state electrolyte membrane with high conductivity for lithium metal batteries operable at -25°C.

Enabling high-areal-capacity all-solid-state lithium-metal batteries by tri-layer electrolyte architectures

In the development of the next-generation safe solid-state supercapacitors with high energy density, durability, and flexibility, the synthesis of high ion-conducting solid-state electrolytes with electrochemical and mechanical stabilities is a great challenge. Solid-state polymer electrolytes (SSPEs) are of great interest as materials in energy storage devices because ion-conducting SSPEs enable good adherence to electrodes and excellent processability for being made into a thin film. The key challenge facing the SSPE development for all-solid-state supercapacitors is to achieve high mechanical performance without sacrificing the requisite ionic conductivity. To overcome the issue, we synthesized networked polymer electrolytes in both aqueous- and non-aqueous forms, using UV or thermal cross-linking methods. The aqueous versions comprise nanohybrid polymer electrolytes (NPEs), salt-in-polyampholoytes (SIPAs), and triple-network polymer electrolytes (TNPEs). Meanwhile, the non-aqueous type features branched network structures endowed with hierarchical nano-canyon characteristics. To tune and understand the SSPE physical and electrochemical properties, the effects of electrolyte type and concentration on morphologic, dielectric, and mechanical properties were thoroughly explored by microstructural, dielectric relaxation, and mechanical measurements. We found that intermolecular interactions within the electrolyte play a vital role in the formation of a nanoscale ion channel confined in the polymer matrix, allowing for a simultaneous increase in the ionic conductivity and mechanical modulus. Tuning the SSPE morphology can also control the microscopic ion migration rate as well as the macroscopic flexibility of the SSPE. To further introduce multifunctional properties, nanocomposite SSPEs were also prepared by combining aqueous SSPEs with inorganic nanoparticles, and their physical properties were investigated using dielectric relaxation spectroscopy, oscillatory shear, and DFT calculation. The principal focus of this presentation is on the insight about our understanding of ion and polymer dynamics of the SSPEs for high-performance supercapacitors.

Solid-state polymer electrolytes can enable the safe operation of high energy density lithium metal batteries; unfortunately, they have low ionic conductivity and poor redox stability at electrode interfaces. Fluorinated ether polymer electrolytes are a promising approach because the ether units can solvate and conduct ions, while the fluorinated moieties can increase oxidative stability. However, current perfluoropolyether (PFPE) electrolytes exhibit deficient lithium-ion coordination and ion transport. Here, we incorporate cross-linked poly(ethylene glycol) (PEG) units within the PFPE matrix and increase the polymer blend electrolyte conductivity by 6 orders of magnitude as compared to pure PFPE at 60 °C from 1.55 × 10-11 to 2.26 × 10-5 S/cm. Blending varying ratios of PEG and PFPE induces microscale phase separation, and we show the impact of morphology on ion solvation and dynamics in the electrolyte. Spectroscopy and simulations show weak ion-PFPE interactions, which promote salt phase segregation into-and ion transport within-the PEG domain. These polymer electrolytes show promise for use in high-voltage lithium metal batteries with improved Li|Li cycling due to enhanced mechanical properties and high-voltage stability beyond 6 V versus Li/Li+. Our work provides insights into transport and stability in fluorinated polymer electrolytes for next-generation batteries.

Solid-state lithium metal batteries (LMBs) have been extensively investigated owing to their safer and higher energy density. In this work, we prepared a novel elastic solid-state polymer electrolyte based on an in situ-formed elastomer polymer matrix with ion-conductive plasticizer crystal embedded with Li6.5La3Zr1.5Ta0.5O12 (LLZTO) nanoparticles, denoted as LZT/SN-SPE. The unique structure of LZT/SN-SPE shows excellent elasticity and flexibility, good electrochemical oxidation tolerance, high ionic conductivity, and high Li+ transference number. The role of LLZTO filler in suppressing the side reactions between succinonitrile (SN) and the lithium metal anode and propelling the Li+ diffusion kinetics can be affirmed. The Li symmetric cells with LZT/SN-SPE cycled stably over 1100 h under a current density of 5 mA cm-2, and Li||LiFePO4 cells realized an excellent rate (92.40 mAh g-1 at 5 C) and long-term cycling performance (98.6% retention after 420 cycles at 1 C). Hence, it can provide a promising strategy for achieving high energy density solid-state LMBs.

Solid‐state electrolytes (SSEs) are pivotal to advancing lithium metal batteries (LMBs). Electrochemically active LiCoO 2 (LCO) has high ionic conductivity (1.45 × 10 −3 S cm −1 at 35 °C), but its inherent electronic conductivity limits its application as an SSE. To address this limitation, a sandwich‐structured composite solid electrolyte (SSCSE) is presented by integrating an LCO layer between non‐electron‐conducting porous polypropylene (PP). This design decouples the electronic and ionic conductivities of LCO, enabling LCO to be an SSE for LMBs for the first time. Meanwhile, the intermediate fast‐ion conductor layer homogenizes Li⁺ flux and enhances mechanical strength, suppressing lithium dendrites growth and improving safety. Li||Li symmetric cell and Li||LFP full cell using LCO as the SSE achieve excellent performance (800 h at 0.5 mA cm −2 and 0.5 mAh cm −2 ; 93.6% capacity retention after 800 cycles with 99.8% coulombic efficiency). This breakthrough in utilizing LCO with high ionic conductivity as an SSE promotes the development of safer and higher energy‐density batteries.

Solid‐state lithium metal batteries (SSLMBs) have gained extensive attraction as one kind of next‐generation energy storage device. However, the drawbacks of flammability, low mechanical strength, and low ionic conductivity limit the further development of solid‐state polymer electrolytes (SPEs). In this work, a reactive flame‐retardant unit into the polymer framework via covalent bonding to create a nonflammable and stretchable polyurethane‐based SPEs is introduced. Meanwhile, the mechanical strength of the polymer backbone is increased by grafting a rigid benzene ring unit, which remarkably suppresses the lithium‐dendrite growth. As a result, these inflammable SPEs do not burn after contact with flames for 6 s. Furthermore, the obtained SPE expands the electrochemical stability window up to 5.1 V. Small monomers containing bromine decompose on the surface of lithium metal creating a LiBr riched solid electrolyte interface (SEI). Li|SPEs|Li symmetric battery offers a stable cycling life for more than 2100 h at 0.2 mA cm−2 and 0.2 mAh cm−2. The LiNi0.6Co0.2Mn0.2O2|SPEs|Li cell equipped with the integrated cathode delivers a 142.1 mAh g−1 capacity after 330 cycles at 0.3 C with 85.2% capacity retention.

Lithium metal batteries (LMBs) have generally become potential candidates for energy storage devices because of their high energy density. However, the practical applications of LMBs have been limited due to the low safety of liquid electrolytes. Compared to liquid electrolytes, solid-state polymer electrolytes (SPEs) have excellent mechanical strength. However, there is room for improvement because traditional PEO-based SPEs need more mechanical properties and electrode contacts for flexible energy device applications. Self-healing solid polymer electrolytes (SHSPEs) have excellent flexibility and healing ability and can also suppress dendrite formation to increase the safety of LMBs. In this study, a novel SHSPE is designed by a combination of the zwitterionic copolymer, SBMA ([2-(methacryloyloxy) ethyl] dimethyl-(3-sulfopropyl) ammonium hydroxide)-co-BA (Butyl Acrylate), and a lithium salt, LiTFSI. We explored their solvation structures and reactivity on the Li metal anode using Density functional theory (DFT) and ab initio molecular dynamics (AIMD) methods. Besides, we also studied the reactivity of the considered SHSPE on the Cu (100) surface to explore the SEI formation mechanisms. The cationic NR4 + and anionic SO3 - groups of SBMA interact electrostatically and form cross-linked network structures within the electrolyte framework, providing the designed SHSPE with prominent self-healing capacity. The decomposition reactions of SHSPE on the Li metal anode are explored, and the resultant decomposition products that contribute to the formation of the solid electrolyte interphase (SEI) are identified. Furthermore, AIMD results indicate that highly concentrated SO3 - groups in the SHSPE promote Li ion diffusion, which increases Li ionic conductivity. The present findings provide design criteria for developing highly conductive self-healing SPEs.

Single-ion conductors with immobile anions can suppress concentration polarization during the cycling in lithium metal batteries (LMBs), thereby inhibiting lithium (Li) dendrite formation. However, strong binding interactions between the anion and Li+ cation can hinder ion dissociation and transport within polymer electrolytes. Herein, weak-binding single-ion gel polymer electrolytes (WSGPE) are designed to enable fast ion transport while maintaining a high electrochemical stability window. The unique delocalized charge distribution of the weakly binding cyanamide-containing monomer, combined with the high dipole moment of the zwitterionic monomer as a decoupling agent, facilitates Li+ ion dissociation and reduces the activation energy for ion hopping. Consequently, the optimized WSGPE exhibits an ionic conductivity of 0.87 mS cm-1, a near-unity transference number of 0.79, and a shear storage modulus of 0.27 MPa at room temperature. These exceptional ion transport and mechanical properties enable stable Li plating/stripping for over 500 h at 0.1 mA cm-2 in Li symmetric cells, effectively suppressing dendrite growth. The design of weakly coordinating structures and the optimization process between ionic conductivity and the modulus is believed to facilitate the design of single-ion polymer electrolytes and the achievement of high-performance LMBs.

Solid-state batteries enabled by solid-state polymer electrolytes (SPEs) are under active consideration for their promise as cost-effective platforms that simultaneously support high-energy and safe electrochemical energy storage. The limited oxidative stability and poor interfacial charge transport in conventional polymer electrolytes are well known, but difficult challenges must be addressed if high-voltage intercalating cathodes are to be used in such batteries. Here, ether-based electrolytes are in situ polymerized by a ring-opening reaction in the presence of aluminum fluoride (AlF3 ) to create SPEs inside LiNi0.6 Co0.2 Mn0.2 O2 (NCM) || Li batteries that are able to overcome both challenges. AlF3 plays a dual role as a Lewis acid catalyst and for the building of fluoridized cathode-electrolyte interphases, protecting both the electrolyte and aluminum current collector from degradation reactions. The solid-state NCM || Li metal batteries exhibit enhanced specific capacity of 153 mAh g-1 under high areal capacity of 3.0 mAh cm-2 . This work offers an important pathway toward solid-state polymer electrolytes for high-voltage solid-state batteries.

Poly(ethylene oxide) (PEO)-based solid-state polymer electrolytes have emerged as one of the most promising candidates for high-energy-density lithium-metal batteries in energy storage applications. However, their notably low ionic conductivity has significantly hindered PEO-based polymer electrolytes' practical application and development, particularly at room temperature (RT). To address the critical challenge of low RT ionic conductivity in PEO-based solid-state electrolytes, this study develops a composite solid electrolyte (CSE) synergistically reinforced by high-concentration lithium salts and Al2O3 filler. The "polymer-in-salt" strategy disrupts PEO crystallinity via concentrated Li salt to form continuous ion channels, while Al2O3 further suppresses crystallization and bridges ionic cluster transport. This dual optimization achieves an ultrahigh ionic conductivity of 9.62 × 10-4 S cm-1 and a 4.8 V electrochemical stability window at RT. The Li symmetric cell exhibits stable cycling for 1000 h at 1 mA cm-2/1 mAh cm-2, and the all-solid-state Li//LiFePO4 coin cell retains 70.7% capacity after 300 cycles at 0.1C. Moreover, Li//LiFePO4 pouch cell maintains 96.4% capacity over 100 cycles at RT. This work establishes a new paradigm for material design and performance enhancement in practical solid-state lithium batteries.

In solid-state lithium metal batteries (SSLMBs), the inhomogeneous electrolyte-electrode interphase layer aggravates the interfacial stability, leading to discontinuous interfacial ion/charge transport and continuous degradation of the electrolyte. Herein, we constructed an anion-modulated ionic conductor (AMIC) that enables in situ construction of electrolyte/electrode interphases for high-voltage SSLMBs by exploiting conformational transitions under multiple interactions between polymer and lithium salt anions. Anions modulate the decomposition behavior of supramolecular poly (vinylene carbonate) (PVC) at the electrode interface by changing the spatial conformation of the polymer chains, which further enhances ion transport and stabilizes the interfacial morphology. In addition, the AMIC weakens the "Li+-solvation" and increases Li+ vehicle sites, thereby enhancing the lithium-ion transport number (tLi +=~0.67). Consequently, Li || LiNi0.8Co0.1Mn0.1O2 cell maintains about 85 % capacity retention and Coulombic efficiency >99.8 % in 200 cycles at a charge cut-off voltage of 4.5 V. This study provides a new understanding of lithium salt anions regulating polymer chain segment behavior in the solid-state polymer electrolyte (SPE) and highlights the importance of the ion environment in the construction of interfacial phases and ionic conduction.

ETPTA polymer network confined amide-based eutectic electrolyte for safe and long- life lithium metal battery

Quasi solid-state polymer electrolytes struggle with a mechanical-ionic conductivity trade-off: rigid polymers enhance mechanical stability but hinder ionic transport, while liquid-like plasticizers improve ionic conductivity but lack mechanical robustness. This work addresses this dilemma by designing a nanostructured semiphase separated electrolyte via in situ copolymerization of solvophobic monomer and solvophilic monomer within a deep eutectic electrolyte. Fluorinated solvophobic monomers create cross-linked networks by excluding Li+-polymer interactions and enhance chemical stability, while solvophilic monomer containing polyether side chains improves ionic conductivity by connecting isolated Li+-rich phases at the nanoscale. Therefore, the optimized polymer electrolyte exhibits high tensile strain (570%), superior ionic conductivity (1.69 mS cm-1 at 30 °C), high Li+ transference number (0.655), and excellent oxidation stability (4.95 V). Based on a mechanochemical synergistic interface stabilization mechanism derived from the carefully designed molecular structure, it also enables ultrastable lithium plating/stripping (3000 h) and a 4.1 mA cm-2 critical current density, and supports 4.5 V NCM811 coin cells and a 307 Wh kg-1 Li metal pouch cell. These advancements deepen the understanding of bridging the inherent mechanical-ionic conductivity trade-off, thereby accelerating the development of high-safety and high-energy-density lithium metal batteries.