Li Cells Research Articles

External Pressure in Polymer-Based Lithium Metal Batteries: An Often-Neglected Criterion When Evaluating Cycling Performance?

Solid-state batteries based on lithium metal anodes, solid electrolytes, and composite cathodes constitute a promising battery concept for achieving high energy density. Charge carrier transport within the cells is governed by solid-solid contacts, emphasizing the importance of well-designed interfaces. A key parameter for enhancing the interfacial contacts among electrode active materials and electrolytes comprises externally applied pressure onto the cell stack, particularly in the case of ceramic electrolytes. Reports exploring the impact of external pressure on polymer-based cells are, however, scarce due to overall better wetting behavior. In this work, the consequences of externally applied pressure in view of key performance indicators, including cell longevity, rate capability, and limiting current density in single-layer pouch-type NMC622||Li cells, are evaluated employing cross-linked poly(ethylene oxide), xPEO, and cross-linked cyclodextrin grafted poly(caprolactone), xGCD-PCL. Notably, externally applied pressure substantially changes the cell's electrochemical cycling performance, strongly depending on the mechanical properties of the considered polymers. Higher external pressure potentially enhances electrode-electrolyte interfaces, thereby boosting the rate capability of pouch-type cells, despite the fact that the cell longevity may be reduced upon plastic deformation of the polymer electrolytes when passing beyond intrinsic thresholds of compressive stress. For the softer xGCD-PCL membrane, cycling of cells is only feasible in the absence of external pressure, whereas in the case of xPEO, a trade-off between enhanced rate capability and minimal membrane deformation is achieved at cell pressures of ≤0.43 MPa, which is considerably lower and more practical compared to cells employing ceramic electrolytes with ≥5 MPa external pressure.

Nonflammable in situ PDOL‐based gel polymer electrolyte for high‐energy‐density and high safety lithium metal batteries

AbstractDue to its high energy density and low interface impedance, in situ polymerized gel electrolytes were considered as a promising electrolyte candidate for lithium metal batteries (LMBs). In this work, a new flame‐retardant gel electrolyte was prepared via in situ ring‐opening polymerization of DOL and TEP. The PDOL–TEP electrolyte exhibits excellent room temperature ionic conductivity (0.38 mS cm−1), wide electrochemical window (4.4 V), high Li+ transference number (0.57), and enhanced safety. Thus, the NCM811||Li cells with PDOL–TEP electrolyte exhibit excellent cycle stability (82.7% of capacity retention rate after 300 cycles at 0.5 C) and rate performance (156 and 119 mAh g−1 at 0.5 and 1 C). Furthermore, phosphorus radicals decomposed from TEP can combine with hydrogen radicals to block the combustion reaction. This work provides an effective method for the preparation of solid‐state LMBs with high voltage, high energy density, and high safety.

Composite Electrolytes with Li2CO3‐Free Garnets Achieved by One‐Step Poly(propylene carbonate) Treatment for High‐Rate and Long‐Life Solid Lithium Batteries

AbstractGarnet‐based composite electrolytes show great potential in building high‐energy‐density solid lithium batteries. However, naturally formed Li2CO3 on garnets owing to air exposure hinders the Li‐ion transport and triggers undesirable performance deterioration. Based on the reaction between basic Li2CO3 and poly(propylene carbonate) (PPC) with a product of propylene carbonate (PC), composite electrolytes with homogeneously distributed Li2CO3‐free garnets as well as PC are fabricated in one step without the post‐treatment of garnet powders in both polyethylene oxide (PEO) and polyvinylidene fluoride (PVDF)‐based electrolytes. The formed PC component further decreases the crystallization of PEO and reduces the grain size of PVDF, leading to improved ion transport in PEO and the suppression of PVDF dehydrofluorination. Consequently, the PPC‐treated garnets enable high ionic conductivities of 3.40 × 10−4 and 1.75 × 10−4 S cm−1 at 30 °C, respectively, in PEO:garnet and PVDF:garnet electrolytes, as well as great electrochemical stability against Li‐metal with a lifespan over 1000 h in Li symmetrical cells at 0.1 mA cm−2. Superior stable cycles are thus realized in both LiFePO4|PEO:garnet|Li and LiNi0.6Co0.2Mn0.2O2|PVDF:garnet|Li cells. These above results demonstrate that the one‐step treatment used here helps the enhancement of Li‐ion transport in composite electrolytes, thus essential for building high‐rate and long‐life solid lithium batteries (SLBs).

Engineering Ion Conduction Nanodomain Spacing and Interface Environment for Ultrastable All‐Solid‐State Lithium Metal Batteries

AbstractBlock copolymer electrolytes are of great interest due to the combination merits of ion conduction and mechanical strength. However, there lacks a comprehensive understanding on the role of nanodomain spacing in ion‐dipole coordinating environment and interface environment. Herein, the lithium salts with varied binding energy are chosen to tune nanodomain spacing in Polyether‐block‐Polyamide (PEO‐PA) polymer. Spectra characterizations in combination with molecular dynamic simulations systematically demonstrate adding LiFSI salts with lower binding energy contributes to forming larger PEO nanodomain spacing and clarifies the relationship between nanodomain spacing and ion‐dipole coordinating environment as well as interface environment. The larger PEO nanodomain spacing in LiFSI doping PEO‐PA electrolytes (AEOF) creates a loosely Li+‐EO group coordinating environment and improves pristine interface contact. In addition, the formation of solid‐electrolyte interphase rich in LiF and Li3N enhances interfacial stability. Therefore, the ionic conductivity of AEOF electrolytes is significantly improved. Furthermore, the Li||AEOF||Li cells exhibit extraordinary cycling life over 10000 h (416 days) at 0.1 mA cm−2 with a capacity of 0.1 mAh cm−2. This study provides a new insight into the ion‐dipole coordinating environment and interface environment, which benefits the theory‐guided design of all‐solid‐state polymer electrolytes.

Hybrid-Electrolytes System Established by Dual Super-lyophobic Membrane Enabling High-Voltage Aqueous Lithium Metal Batteries.

Aqueous electrolytes and related aqueous rechargeable batteries own unique advantage on safety and environmental friendliness, but coupling high energy density Li-metal batteries with aqueous electrolyte still represent challenging and not yet reported. Here, this work makes a breakthrough in "high-voltage aqueous Li-metal batteries" (HVALMBs) by adopting a brilliant hybrid-electrolytes strategy. Concentrated ternary-salts ether-based electrolyte (CTE) acts as the anolyte to ensure the stability and reversibility of Li-metal plating/stripping. Eco-friendly water-in-salt (WiS) electrolyte acts as catholyte to support the healthy operation of high-voltage cathodes. Most importantly, the aqueous catholyte and non-aqueous anolyte are isolated in each independent chamber without any crosstalk. Aqueous catholyte permeation toward Li anode can be completely prohibited without proton-induced corrosion, which is enabled by the introduction of under-liquid dual super-lyophobic membrane-based separator, which can realize the segregation of the most effective immiscible electrolytes with a surface tension difference as small as 6 mJ m-2. As a result, the aqueous electrolyte can be successfully coupled with Li-metal anode and achieve the fabrication of HVALMBs (hybrid-electrolytes system), which presents long-term cycle stability with a capacity retention of 81.0% after 300 cycles (LiNi0.8Mn0.1Co0.1O2 || Li (limited) cell) and high energy density (682Whkg-1).

Dynamic Anion Enables Self‐Healing Single‐Ion Conductor Polymer Electrolyte for Lithium‐Metal Batteries

AbstractLithium‐metal batteries (LMBs) are regarded as a promising option for high‐energy‐density storage systems. However, lithium dendrite growth in LMBs can damage electrolytes and cause short circuits, which severely limits the practical application of LMBs. It is highly desired to develop an advanced polymer electrolyte with self‐healing capability and the ability to inhibit the growth of lithium dendrites for enhancing safety and prolonging the cycle life of the LMBs. Herein, sp3 boron‐based single‐ion conductor polymer electrolytes (B‐SIPEs) with excellent self‐healing capability and interfacial stability are constructed. The rapid bond exchange reactions of dynamic borate anions enable B‐SIPE to fast self‐heal in mild conditions, with a high self‐healing efficiency of 87% within 30 min at an ambient temperature. In particular, B‐SIPE displays a high Li+ transference number (0.88) and excellent lithium dendrite inhibition ability. The Li|B‐SIPE|Li cells exhibit a stable overpotential over 2000 h without short‐circuit. Additionally, the LiFePO4||Li cells with B‐SIPE exhibit superior long‐term cycling performance, with 93.5% capacity retention for 500 cycles. Significantly, B‐SIPE is capable of self‐healing the fracture in LiFePO4||Li cells and recovering the battery performance. These results demonstrate that the advanced self‐healing single‐ion conductor polymer electrolytes effectively promote the reliability and safety of LMBs.

In situ polymerization design of a quasi-solid electrolyte enhanced by NMP additive for lithium metal batteries

Solid polymer electrolytes (SPEs) are considered one promising candidate for lithium metal batteries due to their high flexibility, low cost, and roll-to-roll scalability. However, conventional SPEs prepared via ex situ methods are confronted with challenges such as poor contact and high resistance at the electrode|SPE interface, as well as low ionic conductivity at room temperature. In this study, we developed a quasi-solid electrolyte (QSE) using an in situ polymerization approach, employing butyl acrylate as the monomer and incorporating NMP as an additive. Spectroscopic investigations and DFT calculations revealed that NMP tends to form an overleaf-structured [Li(NMP)3][TFSI] complex with LiTFSI, promoting lithium salt dissociation. Owing to this advantage, the QSE exhibits high room-temperature ionic conductivity (6.94 × 10−4 S cm−1) and an extensive electrochemical stability window (5.01 V vs. Li+/Li). Furthermore, the in situ polymerization method facilitates full contact at the interface, enhancing the interfacial stability and reducing the interface resistance, thus resulting in stable cycling of Li|Built-in QSE|Li symmetric cell for 1100 h at 0.1 mA cm−2. The assembled LiFePO4|Built-in QSE|Li cell also demonstrates excellent rate and long-term cycling performance. Our findings offer valuable insights into the interaction between organic additives and lithium salts and present a novel strategy for the development of polymer electrolytes.

Nitrogen‐Doped Anodic Li Oxide Films as Robust Li Metal Anodes and Solid‐State Electrolytes

AbstractThe performance of the lithium (Li) metal anode in rechargeable batteries has been hampered by the formation of unstable solid‐electrolyte interphase layers, which compromise cycle life and pose significant safety concerns. Herein, for the first time, the anodizing oxidation of pure Li in a liquid electrolyte is developed by using tetrahydrofuran with LiNO3. With this novel process, thickness‐controllable Li oxide films with in situ nitrogen doping during the anodizing process can be obtained. The resulting nitrogen‐doped Li oxide film (NLO) exhibits a uniform surface of the Li metal anode, effectively suppressing Li dendrite growth and simultaneously improving Li ionic conductivity. In addition, the Li metal full cells with Li/NLO anodes perform a long stable life of 1100 cycles at 5C. More importantly, this work demonstrates the great potential of NLO films as a solid‐state electrolyte in solid‐state Li metal batteries. The symmetric Li cells with NLO films perform excellent cycling stability for 300 h at 2 mA cm−2 current density and high Li+ ion conductivity of ≈3 ×10−4 S cm−1 at room temperature. This research not only provides a novel Li anodizing process and a stable Li metal anode but also opens up new possibilities for new solid‐state Li metal battery technologies.

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.

Excellent Stable Cycle Performance of Polyethylene Oxide‐Based 3D Solid Dual‐Salt Composite Electrolyte with Porous Polyimide Thin Films Host

AbstractPolyethylene oxide composite electrolytes are widely used in lithium‐ion batteries because of their excellent moldability, good flexibility, and favorable chemical compatibility. However, they still suffer from low ionic conductivity and weak mechanical strength. Herein, a 3D nanofiber‐reinforced dual‐salt composite solid electrolyte (PI@PCB) is synthesized. Benefiting from the support of the porous polyimide films and the addition of lithium bis(oxalate)borate, the obtained PI@PCB electrolyte exhibits high mechanical strength, good thermal stability, excellent electrochemical stability, and a high lithium ion transference number (0.70). In addition, the assembled Li/PI@PCB/Li cell shows the lowest overpotential of 200 mV at the initial cycling stage and increases to 246 mV slightly after 1500 h. The capacity retention rate of Li/PI@PCB/LFP battery is about 88.3% after 500 cycles at 60 °C.

Covalent Organic Framework Enhanced Solid Polymer Electrolyte for Lithium Metal Batteries.

High ionic conductivity, outstanding mechanical stability, and a wide electrochemical window are the keys to the application of solid-state lithium metal batteries (LMBs). Due to their regular channels for ion transport and tailored functional groups, covalent organic frameworks (COFs) have been applied to solid electrolytes to improve their performance. Herein, we report a flexible polyethylene oxide-COF-LZU1 (abbreviated as PEO-COF) electrolyte membrane with a high lithium ion transference number and satisfactory mechanical strength, allowing for dendrite-free and long-time cycling for LMBs. Benefiting from the interaction between bis(triflfluoromethanesulonyl)imide anions (TFSI-) and aldehyde groups in COF-LZU1, the Li+ transference number of the PEO-5% COF-LZU1 electrolyte reached up to 0.43, much higher than that of neat PEO electrolyte (0.18). Orderly channels are conducive to the homogenous Li-+ deposition, thereby inhibiting the lithium dendrites. The assembled LiFePO4|PEO-5% COF-LZU1/Li cells delivered a discharge specific capacity of 146 mAh g-1 and displayed a capacity retention of 80% after 200 cycles at 0.1 C (60 °C). The Li/Li symmetrical cells of the PEO-5% COF-LZU1 electrolyte presented a longer working stability at different current densities compared to that of the PEO electrolyte. Therefore, the enhanced comprehensive performance of the solid electrolyte shows potential application prospects for use in LMBs.

Self-repaired cathode electrolyte interphase to stabilize the high-nickel cathode interface by a sustained-release multifunctional electrolyte additive

Increasing the nickel content in high-nickel LiNixCoyMn1-x-yO2 cathode materials (NCM) can boost their energy density. However, the consequence of rising Ni content in NCM consists in the heightened stress buildup, intensified irreversible phase transition and severe electrolyte decomposition, and consequently accelerating the battery’s degradation. In the current study, we have revealed that the 4-fluoro-N, N dimethylbenzenesulfonamide (FBSN) as an electrolyte additive can refrain the typical dehydrogenation of EC. Furthermore, a continuously repaired cathode electrolyte interphase (CEI) is designed elaborately on LiNi0.9Co0.05Mn0.05O2 (NCM90) surface by employing the FBSN as a sustained-release electrolyte additive to enhance cycling stability of NCM90||Li cells. This CEI, composed of high mechanical strength LiF and benzene ring skeleton, along with conductive Li+ moieties (S-rich and N-rich species), can be effectively self-repaired in time when damaged, reduce the interaction between the NCM90 and sensitive electrolyte, and mitigate the devastation to the NCM90 cathode surface. As a result, the NCM90||Li cells with 2 % FBSN-containing electrolyte delivers a capacity retention of 90.2 % after 200 cycles at 1C, and 83.1 % after 200 cycles even at higher voltage of 4.5 V, superior than that of Base electrolyte (70.0 % at 4.3 V and 68.0 % at 4.5 V). This study provides an engaging approach to design electrolytes for high-nickel cathodes by autonomously interfacial repair.

Strongly solvating triglyme-based electrolyte realizes stable lithium metal batteries at high-voltage and high-temperature

The electrolyte in lithium-metal batteries (LMBs) plays a pivotal role in stabilizing the surface of the lithium metal anode (LMA) and high-voltage cathode. However, currently widely studied ether-based electrolytes, although it has good compatibility with LMA due to their lower reactivity, are facing significant challenges related to poor oxidation resistance and cathode/electrolyte interface (CEI) instability when combined with the high-voltage cathode, particularly at elevated temperatures. Therefore, there is an urgent need to design advanced electrolytes capable of maintaining high stability under high-voltage and high-temperature conditions. Here, we have developed an ultra-stable localized high-concentration electrolyte (LHCE) by introducing triethylene glycol dimethyl ether (TG), which exhibits strong solvation ability. Computational and experimental results demonstrate that the designed TG-based dilute high-concentration electrolyte (TG-DHCE) possesses a stable solvation structure, high oxidation resistance, and thermal stability, making it ideal for LMBs. Furthermore, the unique solvation structure of TG-DHCE promotes the preferential decomposition of anions while facilitating the formation of stable, inorganic-rich electrode/electrolyte interfaces on the anode and cathode. Consequently, equipped with TG-DHCE, Li||Li cells (more than 1600 h) and Li||NCM523 cells (80.6%, 250 cycles) show superior stability and also demonstrate remarkable performance even at elevated temperatures (60 °C). Additionally, under the harsh conditions of ultrahigh loading NCM523 cathode (19.7 mg/cm2) and limited Li reservoir (twice excess Li was deposited on Cu, Li@Cu) (N/P = 2), Li@Cu||NCM523 cells still maintain stable operation. This work pioneers a new path by choosing strongly solvating solvents, effectively enhancing the cycle life of LMBs under high-voltage and high-temperature conditions.

SiO2-Decorated-Montmorillonite reinforced Poly(1,3-dioxolane) as a multifunctional solid electrolyte for High-Performance lithium batteries

Solid polymer electrolytes (SPEs) have garnered considerable attention owing to their remarkable flexibility, manufacturability, and cost-effectiveness. However, SPEs are hampered by critical limitations such as inadequate ionic conductivity at room temperature and issues related to lithium-ion migration, which curtail their practical applications. To tackle these challenges, the incorporation of inorganic additives into SPEs is considered as an effective strategy. Montmorillonite (MMT), a typical two-dimensional material, has emerged as an advanced filler for SPEs, displaying increased ionic conductivity, lithium-ion transference, and electrochemical stability. Herein, siliconized-modified montmorillonite (SiO2-MMT) nanosheets are synthesized and incorporated into poly(1,3-dioxolane) (PDOL)-based SPEs, resulting in a multifunctional composite solid electrolyte (CSE). The CSE shows an ionic conductivity as high as 5.58 × 10−4 S cm−1 at 30 °C, with a lithium-ion transference number close to 0.58. Symmetrical Li||Li cells utilizing the CSE exhibits stable performance for over 1200 h at a current density of 0.2 mA cm−2. Additionally, the CSE contributes to the stability of electrolytes, facilitates superior Li+ mobility and uniform deposition, thereby forming a stable solid electrolyte interface (SEI). Density functional theory (DFT) simulation confirms that SiO2-MMT, containing a large number of adsorption sites, facilitated fast reaction kinetics and effective anchoring of lithium polysulfides (LiPSs). As a result, the composite electrolyte is cycled in Lithium-sulfur (Li-S) batteries at 200 mA g−1 and 30 °C for 250 cycles, achieving a high coulombic efficiency (CE > 99.4 %) and a capacity decay rate of 0.15 %. Additionally, when paired with high-voltage Li(Ni0.8Co0.1Mn0.1)O2 (NCM811) cathodes and LiFePO4 (LFP) cathodes, both display excellent electrochemical performance. This research presents a highly promising approach for constructing multifunctional solid electrolytes for high-performance lithium batteries.

Manipulating the ionic conductivity and interfacial compatibility of polymer-in-dual-salt electrolytes enables extended-temperature quasi-solid metal batteries

Solid polymer electrolytes (SPEs) have shown great promise in the development of lithium-metal batteries (LMBs), but SPEs’ interfacial instability and limited ionic conductivity still prevent their widespread applications. Herein, high-concentration hybrid dual-salt “polymer-in-salt” electrolytes (HDPEs) through formulation optimization were facilely prepared to simultaneously boost ionic conductivity, improve interfacial compatibility, and ensure a wide-temperature-range operation with high safety. An optimized electrolyte (HDPE-0.6) shows negligible corrosion to the aluminum current collector after manipulating the salt ratio of lithium bis(trifluoromethane)sulfonimide and lithium bis(oxalato)borate. In addition, HDPE-0.6 has excellent ionic conductivity (i.e., ∼0.536, ∼0.898, and ∼1.28 mS cm−1 at 0, 30, and 60 °C), approaching 1 mS cm−1 at room temperature. Furthermore, HDPE-0.6 exhibits a high lithium transference number of 0.6 and a high electrochemical oxidation stability potential of > 4.8 V vs. Li/Li+. Additionally, due to the formulation of high-concentration thermally stable lithium salts and the employment of flame-retardant trimethyl phosphate as the solvent, HDPE-0.6 has no safety issues. The resultant LiFePO4|HDPE-0.6|Li cell exhibits high discharge capacity, good rate capability, and excellent cycle stability at extended temperatures of 0, 30, and 60 °C. By coupling theoretical calculations and in-depth X-ray photoelectron spectroscopy, we attribute the excellent cycle stability to the formation of a stable interphase. Moreover, our formulation strategy is suitable for the Na3V2(PO4)3//Na battery when replacing the lithium salts with sodium salts (i.e., sodium bis(trifluoromethane)sulfonimide and sodium bis(oxalato)borate) to yield HDPE-0.6-Na, as demonstrated by excellent cycle stability (e.g., 98.6 % of capacity retention after 300 cycles). Our work demonstrates that the as-developed quasi-solid HDPEs are suitable for LMBs and sodium-metal batteries, and HDPEs can function normally in a wide temperature range.

Biopolymer Binders for Low‐Temperature Operation of TiNb2O7 Anode in Li‐Ion Batteries

The widespread use of lithium‐ion batteries underlines the criticality of a more sustainable cell fabrication. Here, three biopolymers gelatin, pectin, and deoxyribonucleic acid (DNA) are investigated as binders for the TiNb2O7 anode material in Li cells in a temperature range between 0 and 60 ºC and compared to conventional binder polyvinylidene fluoride (PVDF). The use of biopolymers is motivated by their own environmental friendliness and the possibility to implement an aqueous electrode processing. A specific charge capacity of at least 200 mAh g−1 is found for all binders at 0 °C when testing the cycling performance of TiNb2O7 at 77.5 mA g−1 (1C rate). However, low‐rate cycling at 60 °C shows decreasing capacity for all biopolymers due to the swelling effect and continuous contact loss to the current collector, what also reflects in lowering the overall Li‐diffusion coefficient. This effect becomes less pronounced at 0 °C and high current densities, making biopolymers competitive with commercial PVDF. The electrodes with DNA binder demonstrate overall the most stable performance, arising from the biopolymer intactness and a thin solid–electrolyte interface layer. At 0 °C, the electrode with DNA provides 150 mAh g−1 at 775 mA g−1 for at least 500 discharge–charge cycles.

A siloxane-based self-healing gel electrolyte with deep eutectic solvents for safe quasi-solid-state lithium metal batteries

Due to the safety problems caused by the use of flammable organic electrolytes in lithium batteries, it is urgent to develop new solid electrolytes with higher safety. Deep eutectic solvent (DES), as a very promising flame-retardant electrolyte system, has limited its application due to its liquid properties and poor compatibility with lithium metal. Herein, we report a DES-based self-healing polymer (DSHP) electrolyte for quasi-solid-state lithium metal batteries. The electrolyte was prepared by in-situ polymerization of bis (3-amino-propyl)-terminated polydimethylsiloxane (PDMS-NH2) and toluene 2,4-diisocyanate (TDI) monomers in a DES-based electrolyte with fluoroethylene carbonate (FEC) as an additive. The polymer network effectively improves the compatibility of DES with lithium metal and maintains a high ionic conductivity (0.60 mS cm−1 at 30 °C). At the same time, the well-designed siloxane-based DSHP electrolyte not only exhibits self-healing property, but also demonstrates non-flammability advantage with a wide electrochemical voltage window (4.5 V vs Li/Li+) and a high Li+ migration number (0.69). Therefore, the symmetric Li | DSHP | Li cell exhibits long-term cycle stability (>1400 h). The quasi-solid-state lithium battery with DSHP electrolyte coupled with lithium anode and LiFePO4 cathode demonstrates a high specific capacity of 151.6 mA h g−1. More importantly, the DSHP-based pouch cell exhibits excellent flexibility during the deformation process. This work provides a valuable method to design safe and high energy quasi-solid-state lithium batteries.

Sandwich-type composited solid polymer electrolytes to strengthen the interfacial ionic transportation and bulk conductivity for all-solid-state lithium batteries from room temperature to 120 °C

The insurmountable charge transfer impedance at the Li metal/ solid polymer electrolytes (SPEs) interface at room temperature as well as the ascending risk of short circuits at the operating temperature higher than the melting point, dominantly limits their applications in solid-state batteries (SSBs). Although the inorganic filler such as CeO2 nanoparticle content of composite solid polymer electrolytes (CSPEs) can significantly reduce the enormous charge transfer impedance at the Li metal/SPEs interface, we found that the required content of CeO2 nanoparticles in SPEs varies for achieving a decent interfacial charge transfer impedance and the bulk ionic conductivity in CSPEs. In this regard, a sandwich-type composited solid polymer electrolyte with a 10% CeO2 CSPEs interlayer sandwiched between two 50% CeO2 CSPEs thin layers (sandwiched CSPEs) is constructed to simultaneously achieve low charge transfer impedance and superior ionic conductivity at 30 °C. The sandwiched CSPEs allow for stable cycling of Li plating and stripping for 1000 h with 129 mV polarized voltage at 0.1 mA cm−2 and 30 °C. In addition, the LiFePO4/Sandwiched CSPEs /Li cell also exhibits exceptional cycle performance at 30 °C and even elevated 120 °C without short circuits. Constructing multi-layered CSPEs with optimized contents of the inorganic fillers can be an efficient method for developing all solid-state PEO-based batteries with high performance at a wide range of temperatures.

The Versatile Establishment of Charge Storage in Polymer Solid Electrolyte with Enhanced Charge Transfer for LiF‐Rich SEI Generation in Lithium Metal Batteries

AbstractThe solid‐state electrolyte interface (SEI) between the solid‐state polymer electrolyte and the lithium metal anode dramatically affects the overall battery performance. Increasing the content of lithium fluoride (LiF) in SEI can help the uniform deposition of lithium and inhibit the growth of lithium dendrites, thus improving the cycle stability performance of lithium batteries. Currently, most methods of constructing LiF SEI involve decomposing the lithium salt by the polar groups of the filler. However, there is a lack of research reports on how to affect the SEI layer of Li‐ion batteries by increasing the charge transfer number. In this study, a porous organic polymer with “charge storage” properties was prepared and doped into a polymer composite solid electrolyte to study the effect of sufficient charge transfer on the decomposition of lithium salts. The results show in contrast to porphyrins, the unique structure of POF allows for charge transfer between each individual porphyrin. Therefore, during TFSI− decomposition to the formation of LiF, TFSI− can obtain sufficient charge, thereby promoting the break of C−F and forming the LiF‐rich SEI. Compared with single porphyrin (0.423 e−), POF provides 2.7 times more charge transfer to LiTFSI (1.147 e−). The experimental results show that Li//Li symmetric batteries equipped with PEO‐POF can be operated stably for more than 2700 h at 60 °C. Even the Li//Li (45 μm) symmetric cells are stable for more than 1100 h at 0.1 mA cm−1. In addition, LiFePO4//PEO‐POF//Li batteries have excellent cycling performance at 2 C (80 % capacity retention after 750 cycles). Even LiFePO4//PEO‐POF//Li (45 μm) cells have excellent cycling performance at 1 C (96 % capacity retention after 300 cycles). Even when the PEO‐base is replaced with a PEG‐base and a PVDF‐base, the performance of the cell is still significantly improved. Therefore, we believe that the concept of charge transfer offers a novel perspective for the preparation of high‐performance assemblies.

The Versatile Establishment of Charge Storage in Polymer Solid Electrolyte with Enhanced Charge Transfer for LiF-Rich SEI Generation in Lithium Metal Batteries.

The solid-state electrolyte interface (SEI) between the solid-state polymer electrolyte and the lithium metal anode dramatically affects the overall battery performance. Increasing the content of lithium fluoride (LiF) in SEI can help the uniform deposition of lithium and inhibit the growth of lithium dendrites, thus improving the cycle stability performance of lithium batteries. Currently, most methods of constructing LiF SEI involve decomposing the lithium salt by the polar groups of the filler. However, there is a lack of research reports on how to affect the SEI layer of Li-ion batteries by increasing the charge transfer number. In this study, a porous organic polymer with "charge storage" properties was prepared and doped into a polymer composite solid electrolyte to study the effect of sufficient charge transfer on the decomposition of lithium salts. The results show in contrast to porphyrins, the unique structure of POF allows for charge transfer between each individual porphyrin. Therefore, during TFSI- decomposition to the formation of LiF, TFSI- can obtain sufficient charge, thereby promoting the break of C-F and forming the LiF-rich SEI. Compared with single porphyrin (0.423 e-), POF provides 2.7 times more charge transfer to LiTFSI (1.147 e-). The experimental results show that Li//Li symmetric batteries equipped with PEO-POF can be operated stably for more than 2700 h at 60 °C. Even the Li//Li (45 μm) symmetric cells are stable for more than 1100 h at 0.1 mA cm-1. In addition, LiFePO4//PEO-POF//Li batteries have excellent cycling performance at 2 C (80 % capacity retention after 750 cycles). Even LiFePO4//PEO-POF//Li (45 μm) cells have excellent cycling performance at 1 C (96 % capacity retention after 300 cycles). Even when the PEO-base is replaced with a PEG-base and a PVDF-base, the performance of the cell is still significantly improved. Therefore, we believe that the concept of charge transfer offers a novel perspective for the preparation of high-performance assemblies.