PEO Electrolyte Research Articles

Halogen-Bonding Nanoarchitectonics in Supramolecular Plasticizers for Breaking the Trade-Off between Ion Transport and Mechanical Strength of Polymer Electrolytes for High-Voltage Li-Metal Batteries.

The low ionic conductivity of poly(ethylene oxide) (PEO)-based polymer electrolytes at room temperature impedes their practical applications. The addition of a plasticizer into polymer electrolytes could significantly promote ion transport while inevitably decreasing their mechanical strength. Herein, we report a supramolecular plasticizer (SMP) to break the trade-off effect between ionic conductivity and mechanical properties in PEO-based polymer electrolytes. Accordingly, the SMP is constructed by tetraethylene glycol dimethyl ether (G4) and SbF3 through halogen bonds. The SMP-plasticized PEO electrolyte (PEO/SMP) presents a simultaneously enhanced ionic conductivity of 2.4 × 10-4 S cm-1 (25 °C) and a high mechanical strength of 8.1 MPa, compared to those of pristine PEO-based electrolytes. Benefiting from the halogen bonds between G4 and SbF3, the Li-O coordination in PEO/SMP is evidently weakened, and thus rapid Li+ transport is achieved. Furthermore, the PEO/SMP electrolyte possesses a wide electrochemical stability window of 4.5 V and, importantly, derives an inorganic-rich SEI with a low interfacial resistance on a lithium metal surface. By using PEO/SMP, the lithium-metal battery with the LiNi0.5Co0.2Mn0.3O2 cathode exhibits a good rate and long-term cycling performance with a capacity retention of 75.3% (500 cycles). This work offers a rational guideline for the design of polymer electrolytes suitable for high-performance lithium-metal batteries.

Porous Lithium‐Doped ZnO Nanosheets with Abundant Oxygen Vacancies for Accelerating Li+ Transport in Solid‐State Composite Electrolyte

The flexible Li‐ion conducting solid polymer electrolyte (SPE) endows a stable long‐term cycling to Li‐metal anode to significantly improve the energy density of solid‐state lithium batteries; however, the practical application of the SPE is limited by its low ionic conductivity and small critical current density for dendrite nucleation. Herein, Li+‐doped porous ZnO (LZO) nanosheets are introduced into the poly(ethylene oxide) (PEO)‐based SPE, releasing more mobile Li ions for faster Li‐ion transport due to the enhanced interaction between abundant oxygen vacancies and anions of Li‐salt. As a result, the optimized LZO/PEO composite polymer electrolyte exhibits a high Li‐ion conductivity of 3.3 × 10−4 S cm−1 at 50 °C, 4 times higher than the pure PEO electrolyte. The solid‐state LiFePO4/Li cell shows extraordinarily long‐term stable cycling, up to 1500 cycles with a high average Coulombic efficiency of 99.8%. In addition, the cycling stability of the high‐voltage LiNi0.8Mn0.1Co0.1O2 (NMC811)/Li cell was also obviously improved compared to the nondoped pure PEO electrolyte, indicating the positive contribution of the LZO on interfacial stability.

Lithium-rich high entropy oxide with abundant oxygen vacancies for composite polymer all-solid-state Li-S batteries

Poly(ethylene-oxide) (PEO)-based all-solid-state lithium-sulfur (Li-S) batteries simultaneously possess the advantage of extraordinary theoretical energy density and high safety, high machinability. However, the challenges of lithium polysulfide (LiPS) shuttling and insufficient Li+ conductivity hinder the batteries from practical application. In this work, a lithium-rich high entropy oxide with abundant oxygen vacancies (HL30) is developed as an active filler in PEO to concurrently address the two issues. Specifically, the addition of HL30 promotes the mobility of Li+ in PEO electrolyte as well as provides an extra high-efficiency pathway for Li+ transport, leading to large enhancement of the Li+ ionic conductivity. The metal species in HL30 could anchor the LiPS via bonding interaction while the surface oxygen vacancies further increase the bonding energy. As a result, the ionic conductivity of HL30-containing electrolyte reaches 5.06 × 10−4 S cm−1 at 60 °C, exceeding that of pure PEO electrolyte (2.45 × 10−4 S cm−1) to a considerable extent. The coulombic efficiency of Li-S full battery decreases from 113 % to 103 %, revealing an efficient restriction of shuttling effect. This work provides a novel method of composite polymer electrolyte design to achieve the practical application of high-performance solid-state Li-S batteries.

Conducting Composite Polymer-Based Solid-State Electrolyte with High Ion Conductivity via Amorphous Condensed Structure and Multiple Li+ Transport Channels.

Traditional PEOelectrolyte has high crystallinity which hinders the transmission of Li+, resulting in poor ion conductivity and complicated processing technology. Herein, a polymer electrolyte (p-electrolyte) with a wide electrochemical window and high ionic conductivity is designed, which possesses an amorphous condensed structure. The amorphous structure provides fast transport channels for Li+, so the p-electrolyte possesses an electrochemical window of 4.2V, and high ionic conductivity of 1.58 × 10-5Scm-1 at room temperature, which is 1-2 orders of magnitude higher than that of traditional PEO electrolyte. By using the designed polymer electrolyte as the foundation, an in situ curable composite polymer electrolyte (CPE-L) with multiple Li+ transport channels is elaborately constructed. The Cu-BTC MOF stores abundant Li+, which is introduced into the p-electrolyte. The rich unsaturated Cu2+ coordination sites of Cu-BTC can anchor TFSI- to release Li+, and the pore structure of Cu-BTC MOF cooperates with LLZTO nanoparticles to provide multiple fast transport channel for Li+, resulting in remarkable ionic conductivity (1.02 × 10-3Scm-1) and Li+ transference number (0.58). The Li||CPE-L||Li symmetric battery cycles stably for more than 700h at 0.1mAcm-2, while the specific capacity of full battery is ≈153mAhg-1 (RT, 0.2C).

Bridge for the thermodynamics and kinetics of electrochemical corrosion: The design of self-densified plasma electrolytic oxidation coating on Mg alloys

A new perspective was reported to design the self-densified plasma electrolytic oxidation (SDF-PEO) coatings on magnesium alloys based on the dissolution-ionization-diffusion-deposition (DIDD) model. The main considerations of the new PEO electrolyte include the establishment of a thermodynamics diagram, the construction of a liquid-solid sintering system and the regulation of plasma sparkling kinetics. The SDF-PEO coating exhibited a homogeneous and dense microstructure, superior corrosion resistance and good technological adaptability. This work offers a novel theory to design surface treatment solutions with superior corrosion resistance and promising application prospects.

SiO with ZSM-5 to regulate interfacial stability for fast-charging lithium-ion batteries

Silicon monoxide (SiO) anodes hold great promise for the high-energy advanced battery systems. However, their rate and cycling behavior confront rapid capacity degradation due to the sluggish charge transfer kinetic and serious volume expansion. Though different tactics mitigate this degradation, the effective strategy is still needed to further improve the charge diffusion and mass shift. Here, it is suggested that the stable and fast ion transfer channels are established and dominated by the ZSM-5, combining with PEO, which depresses the volume expansion and leads to the enhanced tolerance during cycling for the SiO anodes. The different molar ratio of ZSM-5/PEO solid state electrolyte impacts greatly the battery performance. This study conducts the interface issues and proposes the integration of ZSM-5 molecular sieve to improve the contact between the solid electrolyte PEO and electrode active material SiO. This resulted in the enhanced ion conductivity and superior hardness in comparison to the pure SiO anodes, correspondingly, an increase in the diffusion coefficient and the electronic conductivity of the fabricated SiO electrode is realized. The optimized anodes, achieves 5.0 A/g rate property with 300 cycles stable cycling and a capacity retention ratio of 82%. This study offers valuable insights into the rational design of cost-effective and high specific energy SiO-based solid-state lithium-ion batteries.

Capacity Degradation of Zero-Excess All-Solid-State Li Metal Batteries Using a Poly(ethylene oxide) Based Solid Electrolyte.

Solid-state polymer electrolytes (SPEs), such as poly(ethylene oxide) (PEO), have good flexibility when compared to ceramic-type solid electrolytes. Therefore, it could be an ideal solid electrolyte for zero-excess all-solid-state Li metal battery (ZESSLB), also known as anode-free all-solid-state Li battery, development by offering better contact to the Cu current collector. However, the low Coulombic efficiencies observed from polymer type solid-state Li batteries (SSLBs) raise the concern that PEO may consume the limited amount of Li in ZESSLB to fail the system. Here, we designed ZESSLBs by using all-ceramic half-cells and an extra PEO electrolyte interlayer to study the reactivity between PEO and freshly deposited Li under a real battery operating conduction. By shuttling active Li back from the anode to the cathode, the PEO SPEs can be separated from the ZESSLBs for experimental studies without the influence from cathode materials or possible contamination from the usage of Li foil as the anode. Electrochemical cycling of ZESSLBs shows that the capacities of ZESSLBs with solvent-free and solvent-casted PEO SPEs significantly degraded compared to the ones with Li metal as the anode for the all-solid-state Li batteries. The fast capacity degradation of ZESSLBs using different types of PEO SPEs is evidenced to be associated with Li reacting with PEO, residual solvent, and water in PEO and dead Li formation upon the presence or absence of residual solvent. The results suggest that avoiding direct contact between the PEO electrolyte and deposited lithium is necessary when there is only a limited amount of Li available in ZESSLBs.

Modulating Ionic Conduction and Accelerating Sulfur Conversion Kinetics through Oxygen Vacancy Engineering for High‐Performance Solid‐State Lithium‐Sulfur Batteries

AbstractPoly(ethylene oxide) (PEO)‐based solid‐state lithium‐sulfur batteries (SSLSBs) have garnered considerable attention as potential energy storage solutions owing to their exceptional specific energy, ease of processing, and economic viability. Nevertheless, the inherently low Li+ conductivity of the PEO electrolyte and the inevitable dissolution of lithium polysulfides (LiPSs) within the sulfur cathode hinder the solid‐state sulfur conversion kinetics and lead to significant loss of active materials, thus posing challenges for practical applications. Herein, these concerns are addressed by incorporating oxygen vacancy enriched‐Nb22W20O102‐x (NWOx) nanorods as cathode additives in high‐performance PEO‐based SSLSBs. The uniformly dispersed NWOx nanorods effectively modify the coordination environment of Li ions by increasing the concentration of free Li ions in the PEO catholyte and alleviating the shuttle effect of dissolved LiPSs. Consequently, the developed SSLSB demonstrates excellent cyclic stability and rate capability. Specifically, it achieves a high discharge capacity of 1208.6 mAh g−1 during the initial cycle and maintains 927.8 mAh g−1 after 200 cycles at 0.1 C. Moreover, such a configuration can accommodate a high loading of active materials with stable capacity retention. Overall, this study presents an effective approach for developing solid‐state sulfur cathodes in PEO‐based SSLSBs.

How do high-voltage cathode and PEO electrolyte get along well? EIS analysis mechanism & potentiometric control strategy

PEO-based all-solid-state electrolytes are extensively utilized and researched owing to their exceptional safety, low-mass-density, and cost-effectiveness. However, the low oxidation potential of PEO makes the interface problem with the high-voltage cathode extremely severe. In this work, the impedance of PEO-based all-solid-state batteries with high-voltage cathode (NCM811) was studied at different potentials. The Nyquist plots displayed a gyrate arc at low-frequencies for NCM811/PEO interface. Based on the kinetic modeling, it was deduced that there is a decomposition reaction of PEO-matrix in addition to de-embedded reaction of NCM811, and the PEO intermediate product (dehydra-PEO) adsorbed on the electrode surface leading to low-frequency inductive arcs. Furthermore, the distribution of relaxation time shows the dehydra-PEO results in the kinetic tardiness of the charge transfer process in the temporal dimension. Hence, an artificial interface layer (CEIx) was modified on the surface of NCM811 to regulate the potential of cathode/electrolyte interface to prevent the high-voltage deterioration of PEO. NCM/CEIx/PEO batteries exhibit capacity retentions of 96.0%, 84.6%, and 76.8% after undergoing 100 cycles at cut-off voltages of 4.1, 4.2, and 4.3 V, respectively. Therefore, here the failure mechanism of high-voltage PEO electrolyte is investigated by EIS and a proposed solving strategy is presented.

Enhancing High Voltage Stability via Fluorination of Functionalized Metal Organic Framework Electrolyte in Lithium Metal Batteries

AbstractThe electrolyte stability under high‐voltage conditions considerably limits the upper cut‐off potential of solid‐state electrolytes (SSEs) and therefore the energy density of all‐solid‐state batteries (ASSBs). In this work, metal‐organic frameworks (MOFs) were fluorinated to lower the energy level of HOMO orbital and allow access to a 4F‐MOF that exhibit enhanced anodic stability. The composited 4F‐MOF/PEO electrolyte could not only transport Li+ ions in the ordered framework channels, but also provide a remarkable high‐voltage stability up to 5.0 V, shielding oxidative decomposition that would otherwise occur at around 3.9 V for conventional PEO electrolytes. In addition, stable lithium deposition was demonstrated for more than 1,300 hours at 0.1 mA ⋅ cm−2, while reversible charge‐discharge cycling performance was delivered in assembled Li||LiNi0.5Mn1.5O4 (LNMO) ASSBs up to 5.0 V. Post‐mortem X‐ray photoelectron spectroscopy (XPS) investigation on cathodes revealed presence of a LiF‐rich cathode electrolyte interface (CEI), supporting promoted stability towards high‐voltage ASSBs.

Multifunctional Additive Enables a "5H" PEO Solid Electrolyte for High-Performance Lithium Metal Batteries.

The solid-state battery with a lithium metal anode is a promising candidate for next-generation batteries with improved energy density and safety. However, the current polymer electrolytes still cannot fulfill the demands of solid-state batteries. In this work, we propose a "5H" poly(ethylene oxide) (PEO) electrolyte via introducing a multifunctional additive of tris(pentafluorophenyl)borane (TPFPB) for high-performance lithium metal batteries. The addition of TPFPB improves the ionic conductivity from 6.08 × 10-5 to 1.54 × 10-4 S cm-1 via reducing the crystallinity of the PEO electrolyte and enhances the lithium-ion transference number from 0.19 to 0.53 via anion trapping due to its Lewis acid nature. Furthermore, the fluorine and boron segments from TPFPB can optimize the composition of the solid-electrolyte interphase and cathode-electrolyte interphase, providing a high electrochemical stability window over 4.6 V of the PEO electrolyte along with significantly improved interface stability. At last, TPFPB can ensure improved safety through a self-extinguishing effect. As a result, the "5H" electrolyte enables the Li/Li symmetric cells to achieve a stable cycle over 2200 h at the current density of 0.2 mA cm-2 with a capacity of 0.2 mA h cm-2; the LiFePO4/Li full cells with a high LFP loading of 8 mg cm-2 exhibits decay-free capacity of 140 mA h g-1 (99% capacity retention) after 100 cycles; and the NCM811/Li cells exhibit a high capacity of 160 mA h g-1 after 50 cycles at 0.5 C. This work presents an innovative approach to utilizing a "5H" electrolyte for high-performance solid-state lithium batteries.

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.

An asymmetric double-layer poly(ethylene oxide)/inorganic composite electrolyte for stable and dendrite-suppressing all-solid-state Li metal battery

Poly (ethylene oxide) (PEO)-based electrolytes are promising in all-solid-state Li metal batteries on account of their distinct merits of cost-effectiveness, good chemical stability against Li metal and facile large-scale membrane fabrication. However, the application of PEO-based electrolytes is mainly hindered by their low ionic conductivity and the risk of short circuit derived from lithium dendrite growth. In this study, we report an asymmetric composite PEO-based solid electrolyte with a bilayer structure, i.e. Li6PS5Cl-PEO-LiTFSI/Li1.3Al0.3Ti1.7(PO4)3-PEO-LiTFSI (LPSCl-PEO/LATP-PEO) composite electrolyte, in which the LATP-PEO layer as the main part of electrolyte faces toward the LiFePO4 cathode and the LPSCl-PEO layer contacts with Li metal. The ionic conductivity of LPSCl-PEO/LATP-PEO based on 2 % of LPSCl nanoparticles and containing 15 % of LATP nanoparticles reaches up to 3.37 × 10−4 S cm−1, comparable to that of other modified PEO-base electrolyte. Benefiting from the excellent ionic transport capacity and interfacial stability, the Li/Li batteries based on the optimal LPSCl-PEO/LATP-PEO stably cycles over 2000 h with no short-circuit at a current density of 0.2 mA cm−2, which is significantly better than pure PEO and unmodified LATP-PEO single-layer electrolyte. Moreover, Li/LiFePO4 all-solid-state battery with the LPSCl-PEO/LATP-PEO electrolyte has a highest capacity of 156.3 mAh g−1 with a capacity decay rate of 0.0375 % per cycle after 400 cycles at 0.5C, and its coulombic efficiency approaching 100 %. This asymmetric double-layer structure electrolyte prepared by a simple and scalable solution casting method provides a feasible solution for the application in stable and dendrite-suppressing all-solid-state Li metal battery.

Advanced Composite Solid Electrolyte Architecture Constructed with Amino‐Modified Cellulose and Carbon Nitride via Biosynthetic Avenue

AbstractPolyethylene oxide (PEO) solid electrolytes are regarded as a promising candidate for all‐solid‐state lithium batteries owing to their high safety and interfacial compatibility. However, PEO electrolyte is plagued by relatively weak structural strength and unsatisfactory Li+ conductivity. Herein, a mechanically strong and Li+ conductively favorable cellulosic scaffold of PEO is fabricated through amino (‐NH2) modification and g‐C3N4 (CN) incorporation of bacterial cellulose (BC) under a microbial circumstance. The biologically ‐NH2 modified BC (B‐NBC) is entangled with CN nanosheets (CN@B‐NBC) through an in situ secretion of nanocellulose followed by hydrogen bond‐induced self‐assembly. The ‐NH2 groups from B‐NBC weaken the complexation of Li+ with its counterpart, thus facilitating the release of more free Li+. CN with strong C‐N covalence and extra lone electrons of N further strengthens the BC skeleton and meanwhile offers sufficient anchors for Li+ migration. After infiltrating by LiTFSI/PEO (LP), the LP/CN@B‐NBC composite solid electrolyte (CSE) exhibits high lithium transference number and ionic conductivity. Upon coupling with LiFePO4 cathode, the full battery exhibits a remarkably high specific capacity, superior rate capability, and decent cycling stability. This work pioneers the attempts of chemical decoration and ingredient incorporation of BC architecture in CSE with the aid of a bottom‐up biosynthetic avenue.

Electrophoretic Deposition of Polyethylene Oxide-Based Gel-Polymer Electrolyte for 3D Lithium-Ion Batteries

Despite the advances made in lithium-ion batteries (LIBs) over the last few decades, improved energy and power density is still required for portable devices, transit, and stationary applications [1-3]. Along with developing new materials, optimizing the shape of the battery electrodes is critical for improving the battery performance since the structure of these electrodes has a large impact on ion movement and reaction kinetics. The appeal of 3D structured batteries comes from certain operating features that are not available with conventional 2D geometries. One important feature is the ability to increase areal capacity (mAh cm−2) within a given footprint area of the electrode .Up to today, various methods were employed to coat the foam-type 3D electrodes with polymer or solid-state electrolytes: spin coating, layer-by-layer, and drop coating. Nonetheless, only a number of full-cell operation cases were disclosed, which led to the conclusion that, despite many attempts, drawbacks still exist in solving the homogeneous coating problem of polymer electrolytes.In this work, we report on the simple and facile coating process of polymer electrolyte on the intricate 3D structured NiO@Ni foam anode with the electrophoretic technique. To the best of our knowledge, it was not yet reported in the literature. The conformally coated polymer layer is proven to be very thin and homogeneous without any defects. The NiO@Ni foam/PEO configuration without the use of a commercial separator displayed stable cyclability up to 100 cycles with capacity retention of 88% and coulombic efficiency of 99%. The results are very promising for solving the problem of integrating polymer electrolytes onto any 3D structured anodes.In summary, a facile and simple electrophoretic technique was employed to conformally coat PEO gel-polymer electrolyte onto foam-type NiO/Ni anode for LIBs for the first time. Two electrodes of NiO/Ni foam as a working electrode and Pt metal as a counter electrode were used for the EPD process. Where the PEO solution acted as an electrolyte and, in the end, formed on the NiO/Ni foam surface. Through investigating various layers of PEO, it was concluded that the method allowed obtaining homogeneous thin films of around 2.66 μm for optimal 10 layers, which were free of cracks and defects. The electrochemical performance of the gel-polymer electrolyte PEO with commercially available liquid electrolyte 1M LiPF6 electrolyte solution in EC/EMC/DC was comparable to the traditional separator when used without it in a half-cell with lithium. The cycling stability results displayed an outstanding performance for the PEO electrolyte, delivering a capacity of 406 mAh g-1 at a 0.1 C rate after the 100th cycle. The stability of the formed PEO on the surface of the anode was demonstrated by FTIR analysis after 100 cycles. The stated simple approach allowed a cell operation at room temperature without a commercial separator, which is an excellent result for further developing high-energy-density full 3D batteries.

(Invited) Advancing Understanding of Composite Polymer Electrolytes with LLZO Nanofibers

Ceramic Li6.55Al0.2La3Zr2O12 (LLZO) is one of the most attractive electrolyte materials for solid-state batteries that combined with metallic Li anodes holds the promise for safer and more energetically dense battery, but its performance is limited by the increases in electrolyte-electrode interfacial resistances upon cycling. The combination of Li+-conducting ceramics and polymers offers a new pathway to create better electrolytes with both high ionic conductivity and good (electro)mechanical interfacial properties. We optimized two-step annealing processing conditions for the fabrication of low temperature cubic-LLZO nanofibers and Li2CO3 removal from the surface of the nanofibers. Using industrially relevant roll-to-roll electrospinning and slot-die coating, we fabricated thin composite membranes with reproducible thickness down to 50 microns. We investigated PEO based composite polymer electrolyte (CPE) with a high, 50 wt% loading of Al-doped LLZO nanofibers in comparison with nanofiber-free PEO electrolyte. XPS measurements show that LLZO is not present at the composite electrolyte surface, and solid electrolyte interphase (SEI) formation is dictated solely by PEO and LiTFSI when reacting with Li metal. Electrochemical SEI formation, studied by cyclic voltammetry, shows SEI formation is identical with and without up to 75 wt% LLZO in the electrolyte. Galvanostatic cycling with lithium symmetric cells shows that the critical current density (CCD) can be tripled by including 50 wt% LLZO, but half cell cycling reveals this comes at the cost of CE. Varying the LLZO loading shows that even a small amount of LLZO drastically lowers the CE, from 88% at 0 wt% LLZO to 77% at just 2 wt% LLZO. Mesoscale modelling reveals that the increase in CCD cannot be explained by an increase in the macroscopic or microscopic stiffness of the electrolyte; only the microstructure of the LLZO nanofibers in the PEO-LiTFSI matrix slows dendrite growth by presenting physical barriers that the dendrites must push or grow around. This tortuous lithium growth mechanism around the LLZO is corroborated with mass spectrometry imaging. Electrochemical impedance spectroscopy (EIS) analysis showed comparable bulk ionic and interfacial resistances with and without nanofibers, indicating that PEO dominates Li+ transport and interfacial chemistry. The total Li-ion conductivity of the composite is still governed by the polymer matrix due to high interfacial resistance between the garnet particles and the PEO/LiTFSI matrix. This work highlights important elements to consider in the design of CPEs for high-efficiency lithium metal batteries.

Construction of Stable Li2O‐Rich Solid Electrolyte Interphase for Practical PEO‐Based Li‐Metal Batteries

AbstractPolyethylene oxide (PEO)‐based solid polymer electrolytes (SPE) have garnered recognition as highly promising candidates for advanced lithium‐metal batteries. However, the practical application of PEO‐based SPE is hindered by its low critical current density (CCD) resulting from undesired dendrite growth. In this study, a PEO‐based SPE that exhibits an ultra‐high CCD (4 mA cm−2) is presented and enhanced lithium ionic conductivity through the incorporation of small amounts of P2S5 (PS). The crystalline Li2O‐rich and P/S‐containing solid electrolyte interphase (SEI) is revealed by cryo‐electron microscope (cryo‐EM) and Time of flight secondary ion mass spectrometry (TOF‐SIMS), which inhibits dendrite growth and adverse reactions between SPE and reductive lithium, thus offering a spherical growth behavior for dendrite‐free lithium metal anode. Consequently, utilizing the PS‐integrated SPE, a Li‐Li symmetric cell demonstrates reduced resistance during operation, enabling stable cycles exceeding 200 hours at 0.5 mA cm−2 and 0.5 mAh cm−2, a stringent test condition for PEO‐based electrolytes. Moreover, a Li/SPE/LiFePO4 (LFP) pouch cell exhibits 80% capacity retention after 100 cycles with 50 µm Li and 30 µm PEO electrolyte, showcasing its potential for practical applications.

Developing flexible and safety-reinforced 3D polymer electrolytes based on polyethylene oxide for solid-state lithium metal batteries

Poly (ethylene oxide) (PEO) is a potential material for solid-state lithium batteries. However, the present polymer electrolyte is hampered by its low ionic conductivity at room temperature and poor mechanical properties, which are significant barriers to its practical application. Herein, we designed a high-performance composite solid electrolyte (PLSP) by incorporating PEO, LiTFSI, and the solid plasticizer butanedinitrile into a 3D polyethylene terephthalate (PET) nonwoven framework with excellent mechanical properties. The PLSP achieved an impressive ionic conductivity of 5.45 × 10−4S cm−1, nearly 100 times higher than the original PEO electrolyte (6.1 × 10−6 S cm−1) at room temperature. Additionally, the optimized composite electrolyte exhibited an extended electrochemical window of up to 5.2 V vs. Li+/Li and a remarkable tensile strength exceeding 8.55 MPa. The stability of the lithium symmetrical battery's charge and discharge voltage platform after 400 h of cycling indicated favorable interfacial compatibility between the PLSP and lithium metal. Furthermore, the assembled Li/PLSP/LFP configuration displayed a discharge specific capacity of 131.4 mA h g−1 and a capacity retention of 93.8 % after 100 cycles at 1C at room temperature, highlighting the promising potential of the composite electrolyte for solid-state lithium batteries.

Ultrathin solid polymer electrolyte enabling mechanically-strong energy storing fiber reinforced composites

Structural batteries attract enormous research interest due to their advantages of integrated energy storage function in structure. Superior to the co-cured composite structural batteries based on glass fiber supported/reinforced liquid/low-strength polymer electrolyte, enhanced mechanical strength of solid polymer electrolyte would enable the facile fabrication of composite structural batteries through layer-by-layer stack up of composites and solid-state batteries. This work encloses a mechanically strong and self-supportive solid polymer electrolyte with a tensile strength of 9.28 MPa, significantly superior to the traditional PEO (Lithium salt) electrolyte. Systematic analysis of phase-microstructure-mechanical/electrochemical properties relationship of SPE with different fluoroethylene carbonate (FEC) amounts helps to find out a solid polymer electrolyte (SPE) with satisfactory ionic conductivity (0.35 × 10−4 S/cm) and high electrochemical stability window (4.6 V vs Li/Li+), based on which dimension-adaptable and mechanically-strong energy storing laminates which have high tensile strength of 343 MPa, tensile modulus of 30.6 GPa, flexural strength of 308 MPa, and high impact resistance have been successfully fabricated. The most surprising result is a capacity retention of as high as 67% of the original capacity in the 1st cycle and stable cycling of composite structural batteries over 50 cycles for the failed tensile sample, which points out its potential application in emergency rescue. We believe this work not only presents a facile method to fabricate solid polymer electrolytes but demonstrates the potential of this solid polymer electrolyte in facile fabrication of mechanically-strong composite structural batteries.

An ameliorated interface between PEO electrolyte and Li anode by Li1.3Al0.3Ti1.7(PO4)3 nanoparticles

An ameliorated interface between PEO electrolyte and Li anode by Li1.3Al0.3Ti1.7(PO4)3 nanoparticles