High-performance Lithium Metal Batteries Research Articles

Homogeneous deposition of lithium ions enabled by BN coated separator for high-performance lithium-metal batteries

Lithium metal has become one of the most promising anode materials in the field of energy storage due to its ultra-high theoretical capacity, low density and low negative potential. Unfortunately, the uncontrollable growth of lithium dendrites on the surface of lithium metal anodes can cause serious deterioration of battery performance and even cause serious safety problems, which greatly limits the further practical application of lithium metal batteries. In order to regulate the uniform deposition of lithium ions and inhibit the growth of lithium dendrites, we modified the surface of commercial Celgard®2325 battery separator by coated BN nanosheets and compared it with Celgard®2325 and Al2O3 coated separator (Al2O3-Separator). It is found that the structure of the inorganic coating on the surface of the separator affects the morphology of the lithium dendrites. The layered BN coated separator (BN-Separator) has the function of regulating the uniform deposition of lithium ions, which delivers the coulombic efficiency of 84.8% for Li|Cu half-cell after stabilize cycling 80 cycles (Celgard®2325 remains coulombic efficiency of approximately 66.2% after 38 cycles.). In addition, BN coating increases the ionic conductivity of commercial separator from 0.53 mS·cm−1 to 1.03 mS·cm−1, enabling an excellent cyclability of lithium metal batteries with a superior capacity of 159.4 mAh g−1 after 500 cycles at 1C rate and 119.0 mAh g−1 after 200 cycles at 5C rate. This work provides a feasible strategy for the design of separators with dendrite suppression function in lithium metal batteries.

Self-healing polymer electrolytes with nitrogen‑boron coordinated boroxine for all-solid-state lithium metal batteries

Polymer networks with dynamic covalent cross-linked boroxine have received a great deal of attention as recyclable and self-healing materials, but their application was rarely mentioned in all-solid-state polymer electrolytes. In this work, the boroxine-based self-healing solid polymer electrolytes (ONBSPE-x) with nitrogen‑boron (NB) coordination were prepared by the amidation reaction between different molecular weight NH2-PEG-NH2 and ortho-triphenylboroxine with the plasticization of lithium salt. To highlight the effect of NB coordination on the self-healing ability of the polymer electrolytes, PNBSPE-2000 with para-triphenylboroxine structure was prepared for comparison. It was proved that the ortho-triphenylboroxine is conducive to the formation of NB coordination and the NB coordination can accelerate the equilibrium of boroxine, further speeding the self-healing ability of ONBSPE-x without external stimulation at room temperature. More importantly, given the strong electron-withdrawing effect of boroxines groups, the ONBSPE-2000 membranes show an ionic conductivity value up to 0.168 mS cm−1 and comparatively high lithium-ion transference number (0.60) at 25 °C, which will minimize concentration polarization between electrolytes and lithium metal anode, then inhibiting lithium dendrite generation. The NB coordination and the interaction between boroxine groups and anions in ONBSPE-2000 were further studied with density functional theory (DFT). The Li|ONBSPE-2000|LiFePO4 coin cell performs excellent cycling stability with an initial discharge capacity of 130.9 mAh g−1 at 0.1C and coulombic efficiency of 94.8 %. Thus, the self-healing solid polymer electrolytes with nitrogen‑boron coordinated boroxine provide a prospective application for high-performance lithium metal batteries.

Multifunctional and Seamlessly Integrated Soft/Rigid Interphase Realizing a Stable Lithium-Metal Anode for a High-Performance Lithium-Metal Battery under a Lean Electrolyte

Multifunctional and Seamlessly Integrated Soft/Rigid Interphase Realizing a Stable Lithium-Metal Anode for a High-Performance Lithium-Metal Battery under a Lean Electrolyte

Self-healing and robust polymer-based protective interlayer containing boronic esters for stabilizing lithium metal anode

Lithium (Li) metal batteries have attracted wide research interests due to the ultrahigh theoretical capacity of Li anode. However, lithium metal anodes suffer from the inhomogeneous Li deposition, resulting in capacity fade and unacceptable safety hazards. More importantly, the huge volume change of the mechanically fragile solid electrolyte interphase (SEI) further induces the dendrite growth during repeated Li plating. Therefore, it is critical to protect Li metal anodes and inhibit the growth of Li dendrites for stabilizing the Li plating process. Herein, we fabricated a novel polymer-based protective interlayer (LBP) with a stable cross-linked network containing abundant boron moieties via the thiol-ene click reaction. The polymer-based protective interlayer obtains self-healing properties through the boronic ester transesterification and enhances the safety of lithium batteries. Besides, the dense layer with a cross-linked network effectively retards the air corrosion when the Li metal was exposed to the air environment. Furthermore, the vacant p orbital in the boron atoms of boronic ester can trap anions of Li salt and regulate a homogeneous Li deposition, enhancing the interface stability of Li metal. Consequently, the Li|Li symmetric cell with LBP protective interlayer shows stable stripping/plating voltage over 3500 h at 1.0 mA cm−2. The LBP-Li|LFP cell maintains a high capacity of 142.2 mAh/g after 300 cycles, demonstrating the cell with LBP-Li exhibits excellent cycling stability. The design of this advanced protective interlayer with multiple capabilities is potential to shed a light for high-performance lithium metal batteries.

Single-Ion Conductive Polymer-Based Composite Electrolytes for High-Performance Solid-State Lithium Metal Batteries.

Flexible composite polymer electrolytes (CPEs) with inorganic electrolyte fillers dispersed in polymer electrolytes integrate the merits of the polymer and inorganic electrolytes and have attracted much attention in recent years. In order to increase the electrochemical performance, especially the low lithium (Li)-ion transference number in traditional dual-ion Li salt-containing CPEs, single-ion conductive CPEs are synthesized with a single-ion polymer conductor (SIPC) as the matrix and Li6.4 La3 Zr1.4 Ta0.6 O12 (LLZTO) particles as the active fillers. The single-ion conductive CPEs show a high Li-ion transference number (up to 0.96), high room-temperature (RT) ionic conductivity (>1.0 × 10-4 S cm-1 ), wide electrochemical stability window (>5.0V, vs Li/Li+ ), and excellent long-term cycling stability with Li metal at RT (3200h). Based on the SIPC-LLZTO CPE, the solid-state lithium metal batteries with LiFePO4 - and LiCoO2 -based cathodes deliver average discharge capacities of 159 mAh g-1 for 600 cycles and 119 mAh g-1 for 200 cycles at RT, respectively. This study sheds light on the design of high-performance CPEs for next-generation solid-state lithium metal batteries.

Eutectic-Based Polymer Electrolyte with the Enhanced Lithium Salt Dissociation for High-Performance Lithium Metal Batteries.

The deployment of lithium metal anode in solid-state batteries with polymer electrolytes has been recognized as a promising approach to achieving high-energy-density technologies. However, the practical application of the polymer electrolytes is currently constrained by various challenges, including low ionic conductivity, inadequate electrochemical window, and poor interface stability. To address these issues, a novel eutectic-based polymer electrolyte consisting of succinonitrile (SN) and poly (ethylene glycol) methyl ether acrylate (PEGMEA) is developed. The research results demonstrate that the interactions between SN and PEGMEA promote the dissociation of the lithium difluoro(oxalato) borate (LiDFOB) salt and increase the concentration of free Li+ . The well-designed eutectic-based PAN1.2 -SPE (PEGMEA: SN=1: 1.2 mass ratio) exhibits high ionic conductivity of 1.30 mS cm-1 at 30 °C and superior interface stability with Li anode. The Li/Li symmetric cell based on PAN1.2 -SPE enables long-term plating/stripping at 0.3 and 0.5 mA cm-2 , and the Li/LiFePO4 cell achieves superior long-term cycling stability (capacity retention of 80.3 % after 1500 cycles). Moreover, Li/LiFePO4 and Li/LiNi0.6 Co0.2 Mn0.2 O2 pouch cells employing PAN1.2 -SPE demonstrate excellent cycling and safety characteristics. This study presents a new pathway for designing high-performance polymer electrolytes and promotes the practical application of high-stable lithium metal batteries.

A Flexible and Self-Healing Ionic Gel Electrolyte Based on a Zwitterion (ZI) Copolymer for High-Performance Lithium Metal Batteries

Ionic gel electrolyte retains the characteristics of non-volatilization, non-flammability and outstanding electrochemical stability of ionic liquid, and shows good electrochemical performance combined with the excellent characteristics of different matrix materials, which is considered to be the best choice to achieve high energy density and safety at the same time. In this paper, a flexible and self-healing ionic gel electrolyte was prepared using a solvent-assisted method based on a zteric ion (ZI) copolymer. Abundant hydrogen bonds and synergistic interaction of ions in the electrolyte system endowed it with remarkable self-healing ability. An ionic conductivity of 9.06 × 10−4 S cm−1 at room temperature was achieved. Moreover, the lithium-ion transference number was increased to 0.312. The ionic gel electrolyte has a self-healing function which guarantees long-term tolerance during charging and discharging. The capacity retention rate of the Li//LiFePO4 battery was 96% after 155 cycles at 0.1 C at 60 °C. This polymer electrolyte is expected to solve the problem of increasing polarization, which is caused by the low lithium ions migration number in ionic liquid electrolyte. And ultimately, it gave rise to a good rate performance.

Achieving stable interphases toward lithium metal batteries by a dilute and anion-rich electrolyte

It is necessary to find an ideal electrolyte suitable for high performance lithium metal batteries (LMBs). Herein, we construct a novel cluster-like and anion-rich dilute electrolyte system by using LiNO3 and trace lithium trifluoromethanesulfonate (LiOTf) in an ester-based electrolyte. In the designed system, NO3– is used as a modulator to regulate the coordination number of solvents and anions, and LiOTf is applied as a solubilizing agent of LiNO3 and trigger for the generation of large cluster. As a result, an anion-regulated solvation structure (ARSS) is obtained even in a dilute Li-ion concentration (<1.5 M), evidenced by various techniques, enabling the electrolyte a high ion-conductivity which vastly differs from a high concentration electrolyte system. Afterwards, the ARSS facilitates the formation of an inorganic-rich solid electrolyte interface (SEI) on both cathode and anode, ensuring the LMBs high stability and long cycling performance.

In-situ construction of cellulose acetate propionate-based hybrid gel polymer electrolyte for high-performance lithium metal batteries

Quasi-solid-state gel polymer electrolytes (GPEs) have a great deal of promise for usage in future energy systems due to their high safety. However, ex-situ prepared GPEs still suffer from interfacial incompatibility. Herein, to create stable electrolyte-electrode interfaces and ensure adequate contact, a novel GPE was prepared by in-situ polymerization using pentaerythritol tetraacrylate (PETEA) and cellulose acetate propionate (CAP) as raw materials. PETEA and CAP with a certain mass ratio were added into liquid electrolyte, and the in-situ polymerization of PETEA and CAP was initiated by azobisisobutyronitrile (AIBN). The multi-side chain structure of PETEA and the hydrogen bonding interaction between PETEA and CAP contributed to a robust cross-linked framework, while CAP improved Li+ transport through its polar oxygen-containing groups. The obtained GPE 1:1 exhibited high ionic conductivity (1.03 ×10−3 S/cm at 25 ℃), superior Li+ transference number (0.73), and good stability to Li metal. Meanwhile, a stable SEI film with rich LiF was established, ensuring a long-term cycling lifespan. After 500 cycles at 1 C, the assembled LiFePO4/GPE 1:1/Li cell revealed a high capacity retention of 90.6%. These results provide a guideline for the future design of novel cellulose-based GPEs for high performance lithium metal batteries.

(Invited) High-Performance Lithium Metal Batteries

The success of rechargeable lithium-ion batteries (LIBs) has brought evident convenience to human society, but state-of-the-art LIBs with a carbon anode are approaching their energy density limits. Li metal is considered the ultimate anode material due to its ultra-high theoretical specific capacity of 3860 mAh g-1, which is more than 10 times higher than lithiated graphite. Nonetheless, Li anode suffers from poor safety and low cycling efficiency due to its high reactivity. Electrolytes that work with Li anode should possess excellent stability against Li metal or form a highly passivating interface. It is also critical to control the amount of Li in the cell, preferably having no excess Li at the anode side.1 In this presentation, next-generation electrolytes that enable such types of high-performance Li metal batteries will be discussed, including advanced liquid electrolytes,2 garnet-type ceramic electrolytes3–5 and hybrid electrolytes.6,7 References C. Zhou, A. J. Samson, M. A. Garakani, and V. Thangadurai, J. Electrochem. Soc., 168, 060532 (2021).C. Zhou et al., Energy Storage Mater., 42, 295–306 (2021) https://doi.org/10.1016/j.ensm.2021.07.043.S. P. Kammampata, R. H. Basappa, T. Ito, H. Yamada, and V. Thangadurai, ACS Appl. Energy Mater., 2, 1765–1773 (2019).S. P. Kammampata, H. Yamada, T. Ito, R. Paul, and V. Thangadurai, J. Mater. Chem. A, 8, 2581–2590 (2020).C. Zhou, A. J. Samson, K. Hofstetter, and V. Thangadurai, Sustain. Energy Fuels, 2, 2165–2170 (2018).S. Bag, C. Zhou, P. J. Kim, V. G. Pol, and V. Thangadurai, Energy Storage Mater., 24, 198–207 (2019) https://doi.org/10.1016/j.ensm.2019.08.019.C. Zhou, S. Bag, T. He, B. Lv, and V. Thangadurai, Appl. Mater. Today, 19, 100585 (2020) https://doi.org/10.1016/j.apmt.2020.100585.

Probing the Stability of Lithium Carbonate in the Lithium-Metal Solid Electrolyte Interphase

The chemical composition and structure of the solid electrolyte interphase (SEI) are two of the key factors that determine the reversibility of lithium-metal (Li) anodes for next-generation batteries. As a result, much of the research aimed at enabling practical Li-metal batteries emphasizes tuning SEI composition, either via electrolyte formulation1–5 or synthesis of artificial SEIs.6–8 Ideally, the lithium SEI should minimize parasitic side reactions by effectively passivating Li while also promoting facile conduction of lithium ions (Li+). To do this, SEI materials must have high (electro)chemical stability, be ionically conductive, and be sufficiently mechanically robust to accommodate substantial volume changes. However, studying these properties in bulk-scale materials often yields values that diverge by orders of magnitude from those observed in SEIs. For example, typical SEI ionic conductivities lie in the range of 10-7-10-9 S cm-1, yet bulk ionic conductivity measurements of relevant materials such as lithium carbonate, lithium fluoride, and lithium oxide ranges from 10-18 and 10-10 S cm-1.9 Our group has developed a technique to directly study these materials at realistic length scales by synthesizing model interphases through the reaction of gases with Li.10,11 Our previous work on Li2O and LiF revealed that Li2O is a better Li+ conductor than LiF (~1 x 10-9 S cm-1 vs ~5.2 x 10-10 S cm-1),11 and that these species’ chemical stability varies substantially in different electrolytes.12 One of the remaining key SEI materials is lithium carbonate, which has been proposed to act as a metastable phase in the outer portion of the SEI.13 In this work, we have developed a technique to synthesize Li2CO3 films via sequential reaction of oxygen and carbon dioxide with clean lithium surfaces. Using scanning electron microscopy and air-exposure tests, we can confirm that these films are conformal and generally pinhole-free. Titration gas chromatography (TGC)14 was used to quantify relative proportions of lithium carbonate, metallic lithium, and lithium carbide, and X-ray photoelectron spectroscopy (XPS) offers insights into how composition changes across the depth of the film. These films were then used as a platform to further investigate the reactivity of Li2CO3 with different electrolytes, comparing carbonates versus ethers and varying the lithium salt used. Electrochemical impedance spectroscopy (EIS) offers insights into the evolution of transport properties at these interphases, while electrolyte soak tests coupled with gas chromatography of gas-phase products and TGC of solid-phase products can track their chemical evolution. Taken together, this work illuminates how lithium carbonate may evolve during battery cycling, offering perspective that can help guide future design of Li-metal SEIs.References Liu, Y. et al. Solubility-mediated sustained release enabling nitrate additive in carbonate electrolytes for stable lithium metal anode. Nat. Commun. 1–10 (2018).Suo, L. et al. Fluorine-donating electrolytes enable highly reversible 5-V-class Li metal batteries. Proc. Natl. Acad. Sci. 115, 1156–1161 (2018).Chae, O. B., Adiraju, V. A. K. & Lucht, B. L. Lithium Cyano Tris(2,2,2-trifluoroethyl) Borate as a Multifunctional Electrolyte Additive for High-Performance Lithium Metal Batteries. ACS Energy Lett. 6, 3851–3857 (2021).Li, Y. et al. Correlating Structure and Function of Battery Interphases at Atomic Resolution Using Cryoelectron Microscopy. Joule 2, 2167–2177 (2018).Zhao, Q. et al. Upgrading Carbonate Electrolytes for Ultra‐stable Practical Lithium Metal Batteries. Angew. Chemie Int. Ed. 61, e2021162 (2021).Zhao, J. et al. Surface Fluorination of Reactive Battery Anode Materials for Enhanced Stability. J. Am. Chem. Soc. 139, 11550–11558 (2017).Li, Y. et al. Robust Pinhole-free Li3N solid electrolyte grown from molten lithium. ACS Cent. Sci. 4, 97–104 (2018).Kozen, A. C. et al. Next-Generation Lithium Metal Anode Engineering via Atomic Layer Deposition. ACS Nano 9, 5884–5892 (2015).Lorger, S., Narita, K., Usiskin, R. & Maier Films of Li, J. Enhanced ion transport in Li2O and Li2S films. Chem. Commun 57, 6503–6506 (2021).He, M., Guo, R., Hobold, G. M., Gao, H. & Gallant, B. M. The intrinsic behavior of lithium fluoride in solid electrolyte interphases on lithium. PNAS 117, 73–79 (2020).Guo, R. & Gallant, B. M. Li 2 O Solid Electrolyte Interphase: Probing Transport Properties at the Chemical Potential of Lithium. Chem. Mater 32, 5525–5533 (2020).Guo, R., Wang, D., Zuin, L. & Gallant, B. M. Reactivity and Evolution of Ionic Phases in the Lithium Solid−Electrolyte Interphase. ACS Energy Lett. 877–885 (2021) doi:10.1021/acsenergylett.1c00117.Han, B. et al. Poor Stability of Li2CO3 in the Solid Electrolyte Interphase of a Lithium-Metal Anode Revealed by Cryo-Electron Microscopy. Adv. Mater. 33, 2100404 (2021).Hobold, G. M. & Gallant, B. M. Quantifying Capacity Loss Mechanisms of Li Metal Anodes beyond Inactive Li0. ACS Energy Lett. 4, 3458–3466 (2022).

Proximity Matters: Interfacial Solvation Dictates Solid Electrolyte Interphase Composition.

The composition of the solid electrolyte interphase (SEI) plays an important role in controlling Li-electrolyte reactions, but the underlying cause of SEI composition differences between electrolytes remains unclear. Many studies correlate SEI composition with the bulk solvation of Li ions in the electrolyte, but this correlation does not fully capture the interfacial phenomenon of SEI formation. Here, we provide a direct connection between SEI composition and Li-ion solvation by forming SEIs using polar substrates that modify interfacial solvation structures. We circumvent the deposition of Li metal by forming the SEI above Li+/Li redox potential. Using theory, we show that an increase in the probability density of anions near a polar substrate increases anion incorporation within the SEI, providing a direct correlation between interfacial solvation and SEI composition. Finally, we use this concept to form stable anion-rich SEIs, resulting in high performance lithium metal batteries.

A crystalline carbon nitride-based separator for high-performance lithium metal batteries.

Lithium metal anodes with ultrahigh theoretical capacities are very attractive for assembling high-performance batteries. However, uncontrolled Li dendrite growth strongly retards their practical applications. Different from conventional separator modification strategies that are always focused on functional group tuning or mechanical barrier construction, herein, we propose a crystallinity engineering-related tactic by using the highly crystalline carbon nitride as the separator interlayer to suppress dendrite growth. Interestingly, the presence of Cl- intercalation and high-content pyrrolic-N from molten salt treatment along with highly crystalline structure enhanced the interactions of carbon nitride with Li+ and homogenized lithium flux for uniform deposition, as supported by both experimental and theoretical evidences. The Li-Li cell with the modified separator therefore delivered ultrahigh stability even after 3,000 h with dendrite-free cycled electrodes. Meanwhile, the assembled Li-LiFePO4 full-cell also presented high-capacity retention. This work opens up opportunities for design of functional separators through crystallinity engineering and broadens the use of C3N4 for advanced batteries.

Designing F/P Hybrid Polymer as Ultrastable Cationic Shielding Interphase for High-Performance Lithium Metal Batteries.

Dendrite growth on electrode-electrolyte interphase has severely limited applications of lithium metal batteries (LMBs). Here, we developed an ionic alternating polymer with fluorocarbons and phosphonium cations in repeating units to regulate Li deposition for the first time. The combined functionalities in the F/P hybrid polymer exhibit remarkable characteristics as a protective layer on top of Li anode, demonstrating outstanding electrochemical stability, ion flux redistributing capability and adaptive chain mobility. Based on characterizations and simulations, this cationic interlayer could effectively furnish long-standing electrostatic shielding for anodes, allowing restrained coating decomposition and homogenized electric field distribution to induce dendrite-free Li deposition, and enabling full cells with enhanced rate and long-term cycling performance. Given the importance of LMBs, this work will promote polymer design to stabilize anodes with superior electrochemical behavior.

Self-assembly formation of solid-electrolyte interphase in gel polymer electrolytes for high performance lithium metal batteries

Lithium-metal batteries (LMBs) using limited-Li anodes are imperative for realizing high-energy storage. Proper solid-electrolyte interphase (SEI) design to control Li-deposition behavior and enhance deposition reversibility is challenging. We engineer the self-assembly formation of SEI in a gel polymer electrolyte (GPE) comprising poly(vinylidene fluoride-co-hexafluoro propylene) (PVDF-co-HFP) dissolved in a LiPF6-LiNO3 dual-salt solution with multiple solvents. The components of this GPE present critical functions: (1) dielectric (PVDF‐co-HFP) dissociates ion pairs to facilitate Li+ transport in the electrolyte and regulate Li+ diffusion in the SEI to lower Li deposition overpotentials, and endows soft characteristics to the SEI; (2) dual-anion PF6−-NO3− in the Li+ solvation sheath facilitates facile Li+ desolvation and formation of rigid and ion-conductive Li3N–LiF-rich SEI. This GPE exhibits higher ionic conductivity and Li+ transference number than the corresponding liquid electrolytes. The capacity retention of an anode-free Cu|GPE|NMC811 battery, i.e., at an anodic-to-cathodic Li ratio (A/C) of 0, reaches 44% after 100 charge-discharge cycles. An LMB with limited-Li at A/C = 2, having energy of 616 Wh kg−1 based on electrode-material mass, exhibits a retention of 85% after 100 cycles. The strategy to regulate Li+-transport and Li-deposition through GPE is promising for realizing the application of LMBs.

High-Performance Solid Lithium Metal Batteries Enabled by LiF/LiCl/LiIn Hybrid SEI via InCl3 -Driven In Situ Polymerization of 1,3-Dioxolane.

The use of poly(1,3-dioxolane) (PDOL) electrolyte for lithium batteries has gained attention due to its high ionic conductivity, low cost, and potential for large-scale applications. However, its compatibility with Li metal needs improvement to build a stable solid electrolyte interface (SEI) toward metallic Li anode for practical lithium batteries. To address this concern, this study utilized a simple InCl3 -driven strategy for polymerizing DOL and building a stable LiF/LiCl/LiIn hybrid SEI, confirmed through X-ray photoelectron spectroscopy (XPS) and cryogenic-transmission electron microscopy (Cryo-TEM). Furthermore, density functional theory (DFT) calculations and finite element simulation (FES) verify that the hybrid SEI exhibits not only excellent electron insulating properties but also fast transport properties of Li+ . Moreover, the interfacial electric field shows an even potential distribution and larger Li+ flux, resulting in uniform dendrite-free Li deposition. The use of the LiF/LiCl/LiIn hybrid SEI in Li/Li symmetric batteries shows steady cycling for 2000 h, without experiencing a short circuit. The hybrid SEI also provided excellent rate performance and outstanding cycling stability in LiFePO4 /Li batteries, with a high specific capacity of 123.5 mAh g-1 at 10C rate. This study contributes to the design of high-performance solid lithium metal batteries utilizing PDOL electrolytes.

A Chemically Bonded Ultraconformal Layer between the Elastic Solid Electrolyte and Lithium Anode for High-performance Lithium Metal Batteries.

Although high ionic conductivities have been achieved in most solid-state electrolytes used in lithium metal batteries (LMBs), rapid and stable lithium-ion transport between solid-state electrolytes and lithium anodes remains a great challenge due to the high interfacial impedances and infinite volume changes of metallic lithium. In this work, a chemical vapor-phase fluorination approach is developed to establish a lithiophilic surface on rubber-derived electrolytes, which results in the formation of a resilient, ultrathin, and mechanically integral LiF-rich layer after electrochemical cycling. The resulting ultraconformal layer chemically connects the electrolyte and lithium anode and maintains dynamic contact during operation, thus facilitating rapid and stable lithium-ion transport across interfaces, as well as promoting uniform lithium deposition and inhibiting side reactions between electrolyte components and metallic lithium. LMBs containing the novel electrolyte have an ultralong cycling life of 2500 h and deliver a high critical current density of 1.1 mA cm-2 in lithium symmetric cells as well as showing good stability over 300 cycles in a full cell.

Synergistic Effect of Crosslinked Organic–Inorganic Composite Protective Layer for High Performance Lithium Metal Batteries

AbstractMaintaining a stable interface of lithium metal anodes (LMAs) by implementing a protective layer is a promising approach in extending the cycle life of lithium metal batteries (LMBs). Nevertheless, designing a protective layer with desired physicochemical properties is still a challenging task. Herein, an inorganic–organic composite protective layer consisting of fluorinated graphene oxide (FGO) (inorganic part) and polyacrylic acid (PAA) (organic part) that are in situ crosslinked via poly(ethylene glycol) diglycidyl ether (PEGDE) into a robust network is reported. The mechanical strength of FGO and the elasticity of the polymeric network jointly suppress the unwanted dendritic Li growth while fluorine‐functional groups in FGO induce an LiF‐enriched interface. This balanced inorganic–organic composite protective layer facilitates charge transfer kinetics for enhanced lithium‐ion diffusion at the interface. Utilizing this protective layer, LMB full‐cells with LiFePO4 demonstrate negligible capacity loss for 100 cycles even under an extreme negative/positive capacity (N/P) ratio of 1.0. This study uncovers the possibility of highly robust, reliable LMBs by a sophisticatedly designed protective layer of widely used inorganic and organic components.

Effectively Elevating Ceramic Fillers’ Dispersity in Gel Hybrid Electrolyte through Bridge–Linked Construction for High–Performance Lithium Metal Batteries

Gel polymer-ceramic hybrid electrolytes (GHEs) have emerged as desirable candidates for preparing high energy density and excellent practicability gel batteries. However, the agglomeration of ceramic particles in polymer matrix leads to a decrease in cycling stability and low mechanical properties of GHEs. Here, we present a feasible method for improving the dispersity of Li0.24La0.59TiO3 (LLTO) nanorods in the polyvinylidenefluoride (PVDF)/poly(propylene carbonate) (PPC) co-blended matrix (K–LLTO/PVDF/PPC) by γ-(2,3-epoxypropoxy)propytrimethoxysilane (KH560) surface treatment. The as-prepared GHE with 10% K–LLTO filler (10% GHE) exhibits a high ionic conductivity (3.01 mS cm−1) and an appropriate lithium-ion transference number (0.55). The Li|10% GHE|Li symmetric cell shows an exceptional lithium stripping-plating lifetime of &gt; 2000 h at 0.1 mA cm−2. The assembled LiFePO4 (LFP)|10% GHE|Li full cells show satisfactory cycling stability in the 2.5–4.2 V electrochemical window by recovering 84% of the initial capacity at 2 C over 500 cycles. The uniformly dispersed K–LLTO within the polymer matrix is ascribed to the formation of a bridge-linked network via Si–O–Ti bonds between KH560 and LLTO, and plenty of hydrogen bonds within the polymer matrix. This modification method provides a feasible strategy for fabricating GHEs with good repeatability, which may easily adapt to the high requirements of commercial production.

Anion Receptor Enhanced Li Ion Transportation for High-Performance Lithium Metal Batteries.

High-potential lithium metal batteries (LMBs) are still facing many challenges, such as the growth of lithium (Li) dendrites and resultant safety hazards, low-rate capabilities, etc. To this end, electrolyte engineering is believed to be a feasible strategy and interests many researchers. In this work, a novel gel polymer electrolyte membrane, which is composed of polyethyleneimine (PEI)/poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) cross-linked membrane and electrolyte (PPCM GPE), is prepared successfully. Due to the fact that the amine groups on PEI molecular chains can provide the rich anion receptors and strongly pin the anions of electrolytes and thus confine the movement of anions, our designed PPCM GPE owns a high Li+ transference number (0.70) and finally contributes to the uniform Li+ deposition and inhibits the growth of Li dendrites. In addition, the cells with PPCM GPE as a separator behave the impressive electrochemical performances, i.e., a low overpotential and an ultralong and stable cycling performance in Li∥Li cells, a low overvoltage of about 34 mV after a stable cycling for 400 h even at a high current density of 5 mA/cm2, and, in Li∥LFP full batteries, a specific capacity of 78 mAh/g after 250 cycles at a 5 C rate. These excellent results suggest a potential application of our PPCM GPE in developing high-energy-density LMBs.