Macromolecular Design of Lithium Conductive Polymer as Electrolyte for Solid-State Lithium Batteries

A Zwitterion Coupled All-Solid-State Single Ion Conducting Polymer Electrolyte via Photoinitiated Thiol-Ene Click Polymerization

The all-solid-state single ion conducting polymer electrolyte has a bottleneck in ionic conductivity even though it can prevent concentration polarization. Here, lithium 3,3'-(diallylammonio)bis(propane-1-sulfonyl(trifluoromethyl sulfonyl)imide) (LiDAA(PSI)2) with a symmetrical "one positive, two negative" structure and unsaturated double bonds for propagation, is synthesized. LiDAA(PSI)2 is copolymerized with 1,2-ethanedithiol and poly(ethylene glycol) diacrylate via photoinitiated thiol-ene click polymerization and forms a random copolymer, SPZ for short. For comparison, lithium 3-(diallylamino)propane-1-sulfonyl(trifluoromethyl sulfonyl)imide) (LiDAAPSI) and corresponding copolymer SP are synthesized. The 7Li resonance peak position of LiDAA(PSI)2 shifts to a low-field compared to that of LiDAAPSI, indicating a weaker electrostatic attraction. The symmetrical "one positive, two negative" structure is responsible for the low-field shift, taking effect of charge conjugation. Unsurprisingly, the ionic conductivity of SPZ is 1.69e-5 S cm-1 at 60 °C, which is 1.9 times that of SP. Lithium electroplating and stripping at 0.0125 mA cm-2@0.05 mAh cm-2 at 60 °C are performed. An all-solid-state single ion conducting lithium metal secondary battery is demonstrated. Zwitterion coupled LiDAA(PSI)2 possesses a symmetrical "one positive, two negative" structure, charge conjugation to weaken electrostatic interaction, and unsaturated double bonds for propagation, which inspires the design and synthesis of single ion conducting polymer electrolytes with zwitterion effect.

Construction of an ultrathin multi-functional polymer electrolyte for safe and stable all-solid-state batteries

The ever-increasing demand for safe and high-energy-density batteries urges the exploration of ultrathin, lightweight solid electrolytes with high ionic conductivity. Solid polymer electrolytes (SPEs) with high flexibility, reduced interfacial resistance and excellent processability have been attracting significant attentions. However, reducing the thickness of SPEs to be comparable with that of commercial separators increases the risk of short-circuiting. Herein, an ultrathin (≈7 μm), flexible and mechanical robust SPE was constructed from a rationally designed multi-functional polymer network, i.e., poly[2,2,2-trifluoroethyl methacrylate-r-(2-ethylhexyl acrylate)-r-methyl methacrylate-r-1,4-bis(acryloyloxy)butane] (PTEM) and porous polyethylene (PE). The resultant PTEM@PE electrolyte possesses a high tensile strength of 128.0 MPa with extensibility up to 34.8%, which could effectively prevent short-circuiting and minimize the interfacial resistance of cells. The obtained all-solid-state Li|PTEM@PE|LiFePO4 cell exhibited stable cycling performance over 1500 cycles at 0.5 C with a capacity retention of 74.4%. With high-voltage NCM811 as the cathode, the cell fabricated with PTEM@PE showed a remarkable capacity retention of 84.2% over 500 cycles. Even with the high-mass loading (≈3 mA h cm-2) NCM811 cathode, the cell could be operated at ambient temperature, demonstrating superior ion-migration kinetics. The current design provides a promising strategy to develop ultrathin and multifunctional solid electrolytes for safe, long-cycling and high-energy-density all-solid-state batteries.

Ultra-robust Single-Ion Conducting Composite Electrolytes for Stable Li-Metal Batteries

With significantly high lithium-ion (Li+) transport efficiency, single-ion conducting polymer electrolytes (SIPEs) often suffer from low ionic conductivity due to the covalently bonded anions to the polymer backbone. Adding plasticizers to SIPEs to improve ionic conductivity usually reduces the polymer matrix's mechanical robustness, negatively affecting overall performance as solid electrolytes. Herein, to surpass such a trade-off relationship, we successfully designed a single-ion conducting composite membrane (c-SIPM60) with cross-linked linear SIPEs and incorporated glass-mesh substrate, which shows a cation transport number close to 1, ultrahigh tensile strength of 22 MPa (modulus of 547.3 MPa), and high ionic conductivity of 1.2 × 10-4 S/cm at 25 °C. The resultant Li/c-SIPM60/Li symmetric cell showed stable cycling performance up to 1200 h, and the LiFePO4/c-SIPM60/Li cell presented good reversibility at C/10. Meanwhile, with additional lithium salts, a high cationic-transport composite membrane (c-HTPM60) was designed to increase the ionic conductivity with retained high Li+ transport efficiency. The LiFePO4/c-HTPM60/Li cell exhibited a stable cycling performance with a capacity retention of >75.6% after 700 cycles at 25 °C. This work provides new insights into designing solid electrolytes with simultaneously high tLi+, ionic conductivity, and mechanical robustness, affording effective Li+ transport for energy storage systems.

Nonionic Amphiphilic Copolymers of Poly(poly(ethylene Glycol) Methacrylate) Brushes with Methyl Methacrylate Prepared by Atom Transfer Radical Polymerization as Dry Solid Polymer Electrolytes for Next Generation Li-ion Battery Applications

Amphiphilic copolymers of comb-like poly(poly(ethylene glycol) methacrylate) (PPEGMA) with methyl methacrylate (MMA) synthesized by one-pot atom transfer radical polymerization were mixed with lithium bis (trifluoromethanesulfonyl) imide salt to formulate dry solid polymer electrolytes (DSPE) for semisolid-state Li-ion battery applications. The PEO-type side chain length (EO monomer's number) in the PEGMA macromonomer units was varied, and its influence on the mechanical and electrochemical characteristics was investigated. It was found that the copolymers, due to the presence of PMMA segments, possess viscoelastic behavior and less change in mechanical properties than a PEO homopolymer with 100 kDa molecular weight in the investigated temperature range. In contrast to the PEO homopolymer, it was found that no crystallization of the copolymers occurs in the presence of the Li-salt. Solid-state NMR and cross-polarization NMR studies revealed that no crystallization (i.e., ion-pair formation) of the Li-salt occurs in the case of the copolymer samples at ambient temperatures; thereby, no phase separation takes place, in contrast to the reference PEO homopolymer sample, which resulted in fairly good ionic conductivity of the copolymers at lower temperatures. The temperature-dependent Li-ion conductivity analyses showed that the conductivity of the copolymers falls in the 10-6-10-3 S/cm range, which is typical for polyether-type DSPEs, but the much lower mass fraction of EO monomers in the copolymers provides the same ionic conductivity values than that of the PEO homopolymer. From a large-scale practical point of view, this clearly indicates reduced Li-salt usage if such copolymer matrices are used instead of PEO homopolymer. Moreover, linear sweep voltammetry (LSV) polarization measurements showed that the PPEGMA-MMA copolymer electrolytes can exhibit a 200-300 mV broader electrochemical stability window than the PEO homopolymer, which is crucial in designing high energy density semisolid-state Li-ion batteries.

Anion Modulation: Enabling Highly Conductive Stable Polymer Electrolytes for Solid-State Li-Metal Batteries

Solid polymer electrolytes (SPEs) are promising ionic conductors for developing high-specific-energy solid-state lithium metal batteries. However, developing SPEs with both high ionic conductivity and interfacial compatibility remains a challenge. Here, we propose a design concept of an anion-modulated polymer electrolyte (termed AMPE) for high-voltage Li metal batteries. Specifically, we design the AMPE by incorporating high-voltage-resistant and high charge density units with an anion receptor unit. The high-voltage-resistant and high charge density segments contribute to achieving a decent voltage tolerance of the polymer chains and ensure sufficient carrier ions. The anion receptor, represented by a boron-containing molecule, promotes the generation of free Li+ by dissociating anion-cation pairs. More importantly, the strong interaction between the electron-deficient B and the TFSI- in the matrix promotes the anion reduction to form a stable anion-derived mosaic-like solid electrolyte interphase on the Li-metal anode. As a result, the AMPE exhibits a high ionic conductivity of 3.80×10-4 S cm-1 and effectively suppresses lithium dendrites, enabling an all-solid-state Li|AMPE|LiCoO2 cell to achieve a cycle life of 700 cycles at an operating voltage of 4.40 V. This design concept would inspire efforts to develop high-performance SPEs for high-specific-energy solid-state lithium metal batteries.

Synergistic effect of Ti3C2Tx MXene/PAN nanofiber and LLZTO particles on high-performance PEO-based solid electrolyte for lithium metal battery

Solid polymer electrolytes (SPEs) have been considered the most promising separators for all-solid-state lithium metal batteries (ASSLMBs) due to their ease of processing and low cost. However, the practical applications of SPEs in ASSLMBs are limited by their low ionic conductivities and mechanical strength. Herein, we developed a three-dimensional (3D) interconnected MXene (Ti3C2Tx) network and Li6.4La3Zr1.4Ta0.6O12 (LLZTO) particles synergistically reinforced polyethylene oxide (PEO)-based SPE, where the association of Li+ with ether-oxygen in PEO could be significantly weakened through the Lewis acid-base interactions between the electron-absorbing group (Ti-F, -O-) of Ti3C2Tx and Li+. Besides, the TFSI- in lithium salts could be immobilized by hydrogen bonds from the Ti-OH of Ti3C2Tx. The 3D interconnected Ti3C2Tx network not only alleviated the agglomeration of inorganic fillers (LLZTO), but also improved the mechanical strength of composite solid electrolyte (CSE). Consequently, the assembled Li||CSE||Li symmetric battery showed excellent cycling stability at 35 ℃ (stable cycling over 3000 h at 0.1 mA cm-2, 0.1 mAh cm-2) and -2 ℃ (stable cycling over 2500 h at 0.05 mA cm-2, 0.05 mAh cm-2). Impressively, the LiFePO4||CSE||Li battery showed a high discharge capacity of 145.3 mAh/g at 0.3 C after 300 cycles at 35 ℃. This rational structural design provided a new strategy for the preparation of high-performance solid-state electrolytes for lithium metal batteries.

Across Interfacial Li+ Conduction Accelerated by a Single-Ion Conducting Polymer in Ceramic-Rich Composite Electrolytes for Solid-State Batteries

Composite electrolytes have been accepted as the most promising species for solid-state batteries, exhibiting the synergistic advantages of solid polymer electrolytes (SPEs) and solid ceramic electrolytes (SCEs). Unfortunately, the interrupted Li+ conduction across the SPE and SCE interface hinders the ionic conductivity improvement of composite electrolytes. In our study on a ceramic-rich composite electrolyte (CRCE) membrane composed of borate polyanion-based lithiated poly(vinyl formal) (LiPVFM) and Li1.3Al0.3Ti1.7(PO4)3 (LATP) particles, it is found that the strong interaction between the polyanions in LiPVFM and LATP particles results in a uniform distribution of ceramic particles at a high proportion of 50 wt % and good robustness of the electrolyte membrane with a Young's modulus of 9.20 GPa. More importantly, ab initio molecular dynamics simulation and experimental results demonstrate that Li+ conduction across the SPE and SCE interface is induced by the polyanion-based polymer due to its high lithium-ion transference number and similar Li+ diffusion coefficient with the SCE. Therefore, the unblocked Li+ conduction among ceramic particles dominates in the CRCE membrane with a high ionic conductivity of 6.60 × 10-4 S cm-1 at 25 °C, a lithium-ion transference number of 0.84, and a wide electrochemical stable window of 5.0 V (vs Li/Li+). Consequently, the high nickel ternary cathode LiNi0.8Mn0.1Co0.1O2-based batteries with CRCE deliver a high-rate capability of 135.08 mAh g-1 at 1.0 C and a prolonged cycle life of 100 cycles at 0.2 C between 3.0 and 4.3 V. The polyanion-induced Li+ conduction across the interface sheds new light on solving composite electrolyte problems for solid-state batteries.

Retarding anion migration for alleviating concentration polarization towards stable polymer lithium-metal batteries

Traditional dual-ion lithium salts have been widely used in solid polymer lithium-metal batteries (LMBs). Nevertheless, concentration polarization caused by uncontrolled migration of free anions has severely caused the growth of lithium dendrites. Although single-ion conductor polymers (SICP) have been developed to reduce concentration polarization, the poor ionic conductivity caused by low carrier concentration limits their application. Herein, a dual-salt quasi-solid polymer electrolyte (QSPE), containing the SICP network as a salt and traditional dual-ion lithium salt, is designed for retarding the movement of free anions and simultaneously providing sufficient effective carriers to alleviate concentration polarization. The dual salt network of this designed QSPE is prepared through in-situ crosslinking copolymerization of SICP monomer, regular ionic conductor, crosslinker with the presence of the dual-ion lithium salt, delivering a high lithium-ion transference number (0.75) and satisfactory ionic conductivity (1.16 × 10-3 S cm-1 at 30 °C). Comprehensive characterizations combined with theoretical calculation demonstrate that polyanions from SICP exerts a potential repulsive effect on the transport of free anions to reduce concentration polarization inhibiting lithium dendrites. As a consequence, the Li||LiFePO4 cell achieves a long-cycle stability for 2000 cycles and a 90% capacity retention at 30 °C. This work provides a new perspective for reducing concentration polarization and simultaneously enabling enough lithium-ions migration for high-performance polymer LMBs.

Aliphatic Hyperbranched Polycarbonates Solid Polymer Electrolytes with High Li-Ion Transference Number for Lithium Metal Batteries

In this work, hyperbranched polycarbonate-poly(ethylene oxide) (PEO)-based solid polymer electrolytes (HBPC-SEs) are successfully synthesized via a straightforward organo-catalyzed "A1"+"B2"-ring-opening polymerization approach. The temperature-dependent ionic conductivity of HBPC-SEs, composed of different polycarbonate linkages and various LiTFSI concentrations, is investigated. The results demonstrate that HBPC-SE with an ether-carbonate alternating structure exhibits superior ionic conductivity, attributed to the solubility of Li salts in the polymer matrix and the mobility of the polymer segments. The HBPC1-SE with 30 wt% LiTFSI presents the highest ionic conductivities of 2.15  × 10-5, 1.78 × 10-4, and 6.07 × 10-4 Scm-1 at 30, 60, and 80 °C, respectively. Compared to traditional PEO-based electrolytes, the incorporation of polycarbonate segments significantly enhances the electrochemical stability window (5 V) and Li+ transference number (0.53) of HBPC-SEs. Furthermore, the LiFePO4/HBPC1-SE-3/Li cell exhibits exceptional rate capability and long-cycling performance, maintaining a discharge capacity of 130 mAh g-1 at 0.5C with a capacity retention of 95% after 300 cycles.

Contributing to the Revolution of Electrolyte Systems via In Situ Polymerization at Different Scales: A Review

Solid-state batteries have become the most anticipated option for compatibility with high-energy density and safety. In situ polymerization, a novel strategy for the construction of solid-state systems, has extended its application from solid polymer electrolyte systems to other solid-state systems. This review summarizes the application of in situ polymerization strategies in solid-state batteries, which covers the construction of polymer, the formation of the electrolyte system, and the design of the full cell. For the polymer skeleton, multiple components and structures are being chosen. In the construction of solid polymer electrolyte systems, the choice of initiator for in situ polymerization is the focus of this review. New initiators, represented by lithium salts and additives, are the preferred choice because of their ability to play more diverse roles, while the coordination with other components can also improve the electrical properties of the system and introduce functionalities. In the construction of entire solid-state battery systems, the application of in situ polymerization to structure construction, interface construction, and the use of separators with multiplex functions has brought more possibilities for the development of various solid-state systems and even the perpetuation of liquid electrolytes.

Toward a molecular understanding of the conductivity of lithium-ion conducting polyanion polymer electrolytes by molecular dynamics simulation

With the improved lithium-ion transference number near unity, the low conductivity of single lithium-ion conducting solid polymer electrolytes (SLIC-SPEs) still hinders their application in high-rate batteries. Though some empirical conclusions on the conducting mechanism of SLIC-SPEs have been obtained, a more comprehensive study on the quantitative relationship between the molecular structure factors and ionic conduction performance is expected. In this study, a model structure that contains adjustable main chain and anion groups in the polyethylene oxide (PEO) matrix was used to clarify the influence of molecular structural factors on ionic conductivity and electrochemical stability of SLIC-SPEs. The anionic group was further disassembled into the intermediate group and end group while the main chain structure was distinguished into different degrees of polymerization and various lengths of the spacers between anions. Therefore, a well-defined molecular structure was employed to describe its relationship with ionic conductivity. In addition, the dissociation degree of salts and mobility of ions changing with the molecular structure were also discussed to explore the fundamental causes of conductivity. It can be concluded that the anion group affects the conductivity mainly via the dissociation degree, while the main chain structure impacts the conductivity by both dissociation degree and mobility.

Garnet/polymer solid electrolytes for high-performance solid-state lithium metal batteries: The role of amorphous Li2O2

Solid-state electrolytes have been widely investigated for lithium batteries since they provide a high degree of safety. However, their low ionic conductivity and substantial growth of lithium dendrites hamper their commercial applications. Garnet-type Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (LLZTO) is one of the most promising active fillers to advance the performance of the solid polymer electrolyte. Nevertheless, their performance is still limited due to their large interfacial resistance. Herein, we embedded the amorphous Li₂O₂ (LO) into LLZTO particles via the quenching process and successfully achieved an interfacial layer of Li₂O₂ around LLZTO particles (LLZTO@LO). Amorphous Li₂O₂ acts as a binder and showed an excellent affinity for Li⁺ ions which promotes their fast transference. Moreover, the stable and dense interfacial Li₂O₂ layer enhances interfacial contact and suppresses the lithium dendrite growth during the long operation cycling process. The PEO/10LLZTO@2LO solid composite polymer electrolyte (SCPE) showed the highest ionic conductivity of 3.2 × 10^-4 S cm^-1 at 40 °C as compared to pristine LLZTO-based SCPE. Moreover, the Li│(PEO/10LLZTO@2LO) │Li symmetric cell showed a stable and smooth long lifespan up to 1100 h at 40 °C. Furthermore, the LiFePO₄//Li full battery with PEO/10LLZTO@2LO SCPE demonstrated stable cycling performance for 400 cycles. These results constitute a significant step toward the practical application of solid-state lithium metal batteries (SS-LMBs).

A self-healing polymerized-ionic-liquid-based polymer electrolyte enables a long lifespan and dendrite-free solid-state Li metal batteries at room temperature

The implementation of high-safety Li metal batteries (LMBs) needs more stable and safer electrolytes. The solid-state electrolytes (SSEs) with their advantageous properties stand out for this purpose. However, low Li/electrolyte interfacial instability and uncontrolled Li dendrites growth trigger unceasing breakage of the solid electrolyte interphase (SEI), leading to fast capacity degradation. In response to these shortcomings, a new type of polymer electrolyte with self-healing capacity is introduced by grafting ionic liquid chain units into the backbones of polymers, which inherits the chemical inertness against the Li anode, allowing high Li⁺ transport, wide electrochemical window, and self-healing traits. Benefiting from the strong external H-bonding interactions, the obtained polymer electrolyte can spontaneously reconstruct dendrite-induced defects and fatigue crack growth at the Li/electrolyte interface, and, in turn, help tailor Li deposition. Owing to the resilient Li/electrolyte interface and dendrite-free Li plating, the equipped Li|LFP batteries display a high initial specific capacity of 134.7 mA h g^-1, rendering a capacity retention of 91.2% after 206 cycles at room temperature. The new polymer electrolyte will undoubtedly bring inspiration for developing practical LMBs with highly improved safety and interfacial stability.

Molecular Self-Assembled Ether-Based Polyrotaxane Solid Electrolyte for Lithium Metal Batteries

Poly(ethylene oxide) has been widely investigated as a potential separator for solid-state lithium metal batteries. However, its applications were significantly restricted by low ionic conductivity and a narrow electrochemical stability window (<4.0 V vs Li/Li⁺) at room temperature. Herein, a novel molecular self-assembled ether-based polyrotaxane electrolyte was designed using different functional units and prepared by threading cyclic 18-crown ether-6 (18C6) to linear poly(ethylene glycol) (PEG) via intermolecular hydrogen bond and terminating with hexamethylene diisocyanate trimer (HDIt), which was strongly confirmed by local structure-sensitive solid/liquid-state nuclear magnetic resonance (NMR) techniques. The designed electrolyte has shown an obviously increased room-temperature ionic conductivity of 3.48 × 10^-4 S cm^-1 compared to 1.12 × 10^-5 S cm^-1 without assembling polyrotaxane functional units, contributing to the enhanced cycling stability of batteries with both LiFePO₄ and LiNi_0.8Co_0.15Al_0.05O₂ cathode materials. This advanced molecular self-assembled strategy provides a new paradigm in designing solid polymer electrolytes with demanded performance for lithium metal batteries.

An Asymmetric Cross-Linked Ionic Copolymer Hybrid Solid Electrolyte with Super Stretchability for Lithium-Ion Batteries

Composite solid electrolytes are recommended to be the most promissing strategy for solid-state batteries because they combine the advantages of inorganic ceramics and polymers. However, the huge interfacial resistance between the inorganic ceramic and polymer results in low ionic conductivity, which is still the major impediment that limits their applications. Herein, a novel highly elastic and weakly coordinated ionic copolymer hybrid electrolyte with asymmetric structure based on surface-modified Li_1.5 Al_0.5 Ge_1.5 (PO₄ )₃ by "in situ" polymerization is proposed to improve ionic conductivity and mechanical properties simultaneously. The all-solid hybrids electrolytes exhibit room-temperature ionic conductivity up to 2.61 × 10^-4 S cm^-1 and lithium-ion transference number of 0.41. The hybrids electrolytes can be repeatedly stretching-releasing-stretching, showing a super stretchability with the elongation at break up to 496%. The Li symmetrical cells assembled with the hybrid electrolytes can continuously operate for 800 h at 0.1 mA cm^-2 without discernable dendrites, indicating good interfacial compatibility between the hybrid electrolytes and lithium electrodes. The Li|LiFePO₄ batteries assembled with the hybrid electrolytes deliver an initial discharge specific capacity of 165.5 mAh g^-1 with an initial coulombic efficiency of 94.8% and 154 mAh g^-1 after 100 cycles at 0.1 C, and maintain 95.4% capacity retention after 100 cycles at 0.5 C.

Quasi-Solid-State Ion-Conducting Arrays Composite Electrolytes with Fast Ion Transport Vertical-Aligned Interfaces for All-Weather Practical Lithium-Metal Batteries

The rapid improvement in the gel polymer electrolytes (GPEs) with high ionic conductivity brought it closer to practical applications in solid-state Li-metal batteries. The combination of solvent and polymer enables quasi-liquid fast ion transport in the GPEs. However, different ion transport capacity between solvent and polymer will cause local nonuniform Li⁺ distribution, leading to severe dendrite growth. In addition, the poor thermal stability of the solvent also limits the operating-temperature window of the electrolytes. Optimizing the ion transport environment and enhancing the thermal stability are two major challenges that hinder the application of GPEs. Here, a strategy by introducing ion-conducting arrays (ICA) is created by vertical-aligned montmorillonite into GPE. Rapid ion transport on the ICA was demonstrated by ⁶Li solid-state nuclear magnetic resonance and synchrotron X-ray diffraction, combined with computer simulations to visualize the transport process. Compared with conventional randomly dispersed fillers, ICA provides continuous interfaces to regulate the ion transport environment and enhances the tolerance of GPEs to extreme temperatures. Therefore, GPE/ICA exhibits high room-temperature ionic conductivity (1.08 mS cm^-1) and long-term stable Li deposition/stripping cycles (> 1000 h). As a final proof, Li||GPE/ICA||LiFePO₄ cells exhibit excellent cycle performance at wide temperature range (from 0 to 60 °C), which shows a promising path toward all-weather practical solid-state batteries.

Understanding a Single-Li-Ion COF Conductor for Being Dendrite Free in a Li-Organic Battery

In addition to improving ion conductivity and the transference number, single-Li-ion conductors (SLCs) also enable the elimination of interfacial side reactions and concentration difference polarization. Therefore, the SLCs can achieve high performance in solid-state batteries with Li metal as anode and organic molecule as cathode. Covalent organic frameworks (COFs) are leading candidates for constructing SLCs because of the excellent 1D channels and accurate chemical-modification skeleton. Herein, various contents of lithium-sulfonated covalently anchored COFs (denoted as LiO3S-COF1 and LiO3S-COF2) are controllably synthesized as SLCs. Due to the directional ion channels, high Li contents, and single-ion frameworks, LiO3S-COF2 shows exceptional Li-ion conductivity of 5.47×10−5 S·cm−1, high transference number of 0.93, and low activation energy of 0.15 eV at room temperature. Such preeminent Li-ion-transported properties of LiO3S-COF2 permit stable Li+ plating/stripping in a symmetric lithium metal battery, effectively impeding the Li dendrite growth in a liquid cell. Moreover, the designed quasi-solid-state cell (organic anthraquinone (AQ) as cathode, Li metal as anode, and LiO3S-COF2 as electrolyte) shows high-capacity retention and rate behavior. Consequently, LiO3S-COF2 implies a potential value restraining the dissolution of small organic molecules and Li dendrite growth.

Solid Polymer Electrolytes for Lithium Batteries: A Tribute to Michel Armand

In a previous publication, a tribute to Michel Armand was provided, which highlighted his outstanding contribution to all aspects of research and development of lithium-metal and lithium-ion batteries. This area is in constant progress and rather than an overview of the work of Armand et al. since the seventies, we mainly restrict this review to his contribution to advances in solid polymer electrolytes (SPEs) and their performance in all-solid-state lithium-metal batteries in recent years.

Fabrication and Investigation of PE-SiO2@PZS Composite Separator for Lithium-Ion Batteries

Commercial polyolefin separators exhibit problems including shrinkage under high temperatures and poor electrolyte wettability and uptake, resulting in low ionic conductivity and safety problems. In this work, core–shell silica-polyphosphazene nanoparticles (SiO₂@PZS) with different PZS layer thicknesses were synthesized and coated onto both sides of polyethylene (PE) microporous membranes to prepare composite membranes. Compared to pure silica-coated membranes and PE membranes, the PE-SiO₂@PZS composite membrane had higher ionic conductivity. With the increase in the SiO₂@PZS shell thickness, the electrolyte uptake, ionic conductivity and discharge capacity gradually increased. The discharge capacity of the PE-SiO₂@PZS composite membrane at 8 C rate was 129 mAh/g, which was higher than the values of 107 mAh/g for the PE-SiO₂ composite membrane and 104 mAh/g for the PE membrane.

Solid-State Lithium Metal Battery of Low Capacity Fade Enabled by a Composite Electrolyte with Sulfur-Containing Oligomers

A solid-state lithium metal battery of low capacity fade is acquired using the electrolyte membrane of a polyurethane-acrylate-thiocarbonate (PUAT) oligomer, macromolecules, lithium salt, and an oxide additive. Two types of composite electrolytes have been prepared: the free-standing electrolyte (PUAT-FS) and the electrode-coated electrolyte (PUAT-EC). Featuring a less PUAT content and a finer granular size, PUAT-FS is less ion-conductive than PUAT-EC; 0.44 mS cm^-1 in contrast to 0.51 mS cm^-1 at room temperature. Nonetheless, the lithium iron phosphate battery of PUAT-FS is far superior to that of PUAT-EC in terms of cycling stability. When cycled at 0.1C and room temperature, the PUAT-FS battery reaches a maximum discharge capacity of 169.7 mAh g^-1 at its 20th cycle and decreases to 141.0 mAh g^-1 at the 500th cycle, 83.1% retention. The capacity fading rate of the PUAT-FS battery is 0.034% per cycle at 0.1C, significantly less than that of the PUAT-EC battery, 0.138% per cycle. Other maximum capacities and fading rates of the PUAT-FS battery are 152.5 mAh g^-1 and 0.050% per cycle at 0.2C in 800 cycles and 126.1 mAh g^-1 and 0.051% per cycle at 0.5C in 1000 cycles. These features of a low fading rate and high capacity are attributed to a balanced ratio of oligomer to macromolecule (1:1 w/w) in the free-standing electrolyte and the sulfur-containing oligomer.

Lithium Salt-Induced In-Situ Polymerizations Enable Double Network Polymer Electrolytes

Structural design is an intriguing strategy to improve the physical and electrochemical performance of polymer electrolytes (PEs) for lithium-ion batteries. However, the complex synthetic process and introduction of non-electrolyte composition severely limit the development and practical application of PEs. Here we report a facile method for the fabrication of a double network polymer electrolyte (DN-PE) through combining the lithium salt-accelerated thiol-Michael addition and lithium salt-catalyzed radical polymerization. By adjusting the reaction temperature, the double network with the crosslinking structure could be in-situ formed step by step at room temperature and 80 °C. Notably, using lithium salt as the accelerator and catalyst avoids the addition of extra species and the related side reactions in the electrolyte system. Compared with single network polymer electrolyte (SN-PE), DN-PE has a distinctly improved mechanical strength and a better interfacial compatibility with the electrode, which leads to a stable cycling of the symmetric Li|DN-PE|Li cell over 1000 h at a current density of 0.05 mA cm^-2 . In addition, the Li|DN-PE|LiFePO₄ cell shows a high discharge specific capacity of 150.3 mAh g^-1 at 0.1 C and coulomb efficiency of 99%. This article is protected by copyright. All rights reserved.

Investigating miscibility and lithium ion transport in blends of poly(ethylene oxide) with a polyanion containing precisely-spaced delocalized charges

Synthesis of a precision single ion conductor with a phenylsulfonyl (TFSI) lithium salt pendant at every 5th carbon is reported and miscibility, conductivity, and transference studies are performed upon blending with PEO at varying compositions.

Recent Advances in Functional Polymer Materials for Energy, Water, and Biomedical Applications: A Review

Academic research regarding polymeric materials has been of great interest. Likewise, polymer industries are considered as the most familiar petrochemical industries. Despite the valuable and continuous advancements in various polymeric material technologies over the last century, many varieties and advances related to the field of polymer science and engineering still promise a great potential for exciting new applications. Research, development, and industrial support have been the key factors behind the great progress in the field of polymer applications. This work provides insight into the recent energy applications of polymers, including energy storage and production. The study of polymeric materials in the field of enhanced oil recovery and water treatment technologies will be presented and evaluated. In addition, in this review, we wish to emphasize the great importance of various functional polymers as effective adsorbents of organic pollutants from industrial wastewater. Furthermore, recent advances in biomedical applications are reviewed and discussed.

Single-ion conducting polymer electrolytes as a key jigsaw piece for next-generation battery applications

As lithium-ion batteries have been the state-of-the-art electrochemical energy storage technology, the overwhelming demand for energy storage on a larger scale has triggered the development of next-generation battery technologies possessing high energy density, longer cycle lives, and enhanced safety. However, commercial liquid electrolytes have been plagued by safety issues due to their flammability and instability in contact with electrodes. Efforts have focused on developing such electrolytes by covalently immobilizing anionic groups onto a polymer backbone, which only allows Li+ cations to be mobile through the polymer matrix. Such ion-selective polymers provide many advantages over binary ionic conductors in battery operation, such as minimization of cell polarization and dendrite growth. In this review, the design, synthesis, fabrication, and class are reviewed to give insight into the physicochemical properties of single-ion conducting polymer electrolytes. The standard characterization method and remarkable electrochemical properties are further highlighted, and perspectives on current challenges and future directions are also discussed.

Vertical Channels Design for Polymer Electrolyte to Enhance Mechanical Strength and Ion Conductivity

Polymer electrolytes are the key candidates for solid-state batteries benefiting from their intrinsic advantages over inorganic electrolytes in terms of flexibility and easy processability. However, they suffer from low ionic conductivity and poor mechanical strength, which restrict their wide utilization. Conventional ceramic fillers are used to improve the mechanical properties of polymer electrolytes but lack sufficient Li⁺ conductivity. In this work, a framework with vertical channels that possess fast Li⁺ movement is designed. It is found that the poly(ethylene oxide) (PEO) compound in the vertical channel framework benefits to improve the ionic conductivity and mechanical strength synchronously. The framework in which ionic liquids are loaded on a zirconium dioxide surface (ZrO₂@ILs) helps to improve ionic conductivity by 2 orders of magnitude compared with PEO, which is due to the enhanced orientation of ion transport. By optimizing the content of ZrO₂@ILs, the elastic modulus is also tripled. Therefore, the symmetric lithium battery can cycle stably for more than 800 h at a current density of 0.25 mA cm^-1, whereas the lithium metal battery has a specific capacity of 135 mAh g^-1 at a current density of 2C and can cycle stably for more than 200 cycles at 60 °C.