Room‐Temperature Crosslinkable Natural Polymer Binder for High‐Rate and Stable Silicon Anodes

Polymer electrolytes are considered as solid-state ionic conductors for the next generation of lithium metal batteries. Particularly, poly(ethylene oxide)-based electrolytes have been extensively studied due to their excellent ion conductivity and interfacial compatibility. Since the lithium-ion transport is strongly coupled with segmental motion of polymer chains, there usually exists a dilemma between the ion conductivity and mechanical strength enhancement. Other problems of low ion conductivity at low temperature and low cation transference number further impede their practical applications in batteries. Here, we report a type of polythiourea solid-state electrolyte, which exhibits a superionic ion conducting behavior. The strong supramolecular interaction between the thiourea group and perchlorate anions promotes the dissolution of high concentration lithium salts in polythiourea. The conducting channel composed of high-density thiourea and percolating polar groups enables rapid cation transport along the polymer chain and even working at the glass state. The combined merits of high transference number, good ion conductivity, and excellent mechanical strength are achieved in this class of superionic ionic conductors, shedding light on alternative solutions for solid-state electrolytes in batteries.

Currently, electrolytes used in lithium-ion batteries are flammable and leaky, causing safety problems when used under high temperatures or extreme conditions. Solid electrolytes can fundamentally avoid the occurrence of such issues, at the same time, it can significantly increase the energy density of solid state lithium batteries. Solid electrolytes are classified into inorganic solid electrolytes and solid polymer electrolytes. Although inorganic solid electrolytes have the high mechanical strength and room temperature ionic conductivity, it has poor flexibility and complicated preparation process. In contrast, solid polymer electrolyte has good elasticity and good interface contact, which can overcome many disadvantages of the inorganic solid electrolyte. Among them, polyethylene oxide (PEO) is first proposed as a polymer electrolyte. Due to its excellent mechanical properties, electrochemical stability and thermal stability, it has been a hot topic for polymer solid electrolytes for decades. However, its low room temperature ionic conductivity limits practical application. Given the problems existing in PEO-based polymer electrolytes, several methods for improving ionic conductivity have been proposed. The primary methods include plasticization, the organic-inorganic composite, and polymer blending. Comparing these methods, it can be seen that adding plasticizers to the polymer can effectively increase the conductivity of the electrolyte, but at the same time it will cause a decrease in the mechanical properties, and the safety issues limit its application in lithium-ion batteries. Inorganic fillers can balance the problems of ionic conductivity and mechanical properties, but the construction of a good filler-polymer dispersion system is complicated in preparing such composite electrolytes, design a new type of multi-dimensional the ion transport network also face tremendous challenges. Undoubtedly, in the future research, inorganic fillers will be the dominant means in the modification of composite electrolytes. Compared with the former two modification methods, polymer blending is easy to operate and friendly to industry, but low ionic conductivity at room temperature still exist. To give full play to the advantages of polymer blending, using it as an auxiliary means to improve the performance of composite electrolytes will be the primary development direction of such modification methods. PEO is the most widely studied polymer electrolyte. Even though a large number of modification methods have emerged in its development history, the ionic conductivity at room temperature is still limited to a relatively low level. To meet the needs of the application in lithium-ion batteries, a high operating temperature (50−70℃) is still needed, the biggest problem remains exist. To solve the problems in polymer solid electrolytes, the research directions in the future may mainly focus on: Expanding the modification method of PEO to other polymer electrolyte host materials, broadening the scope of research, and finding the available polymer electrolytes at room temperature. Concerned about the preparation of ultra-thin polymer electrolytes, reducing the ion transmission path to increase the transmission efficiency of lithium ions between positive and negative electrodes. Effectively combines inorganic solid electrolytes and solid polymer electrolytes to give full play to their advantages. In addition, exploring the effect of inorganic filler morphology on the conductivity of the composite electrolyte will also deserve attention. Many one-dimensional, two-dimensional materials can build ion transport networks so that lithium ions can travel rapidly along the path. With the deepening of research, it is expected that PEO-based polymer electrolytes may replace liquid electrolytes and become an essential cornerstone for building the next generation of safe and reliable lithium-ion batteries.

Ultralong hydroxyapatite nanowires-based flow-through reactor with high loading of silver nanoparticles for fast continuous catalytic reduction of organic dyes and disinfection of wastewater

Understanding the Li-ions conduction network and transport dynamics in polymer electrolyte is crucial for developing reliable all-solid-state batteries. In this work, advanced nano- X-ray computed tomography combined with Raman spectroscopy and solid state nuclear magnetic resonance are used to multi-scale qualitatively and quantitatively reveal ion conduction network of poly(ethylene) oxide (PEO)-based electrolyte (from atomic, nano to macroscopic level). With the clear mapping of the microstructural heterogeneities of the polymer segments, aluminium-oxo molecular clusters (AlOC) are used to reconstruct a high-efficient conducting network with high available Li-ions (76.7%) and continuous amorphous domains via the strong supramolecular interactions. Such superionic PEO conductor (PEO-LiTFSI-AlOC) exhibites a molten-like Li-ion conduction behaviour among the whole temperature range and delivers an ionic conductivity of 1.87 × 10-4 S cm-1 at 35 °Ϲ. This further endows Li electrochemical plating/stripping stability under 50 μA cm-2 and 50 μAh cm-2 over 2000 h. The as-built Li|PEO-LiTFSI-AlOC|LiFePO4 full batteries show a high rate performance and a capacity retention more than 90% over 200 cycling at 250 μA cm-2, even enabling a high-loading LiFePO4 cathode of 16.8 mg cm-2 with a specific capacity of 150 mAh g-1 at 50 °Ϲ.

ABSTRACTThree main chain thermotropic liquid crystalline (LC) azobenzene polymers were synthesized using the azobenzene twin molecule (P4P) having the structure Phenylazobenzene‐tetraethyleneglycol‐Phenylazobenzene as the AA monomer and diols like diethylene glycol, tetraethylene glycol (TEG), and hexaethylene glycol as the BB comonomer. Terminal C(O)OMe units on P4P facilitated transesterification with diols to form polyesters. All polymers exhibited stable smectic mesophases. One of the polymers, Poly(P4PTEG) was chosen to prepare composite polymer electrolytes with LiCF3SO3 and ionic conductivity was measured by ac impedance spectroscopy. The polymer/0.3 Li salt complex exhibited a maximum ionic conductivity in the range of 10−5 S cm−1 at room temperature (25 °C), which increased to 10−4 S cm−1 above 65 °C. The temperature dependence of ionic conductivity was compared with the phase transitions occurring in the sample and it was observed that the glass transition had a higher influence on the ionic conductivity compared to the ordered LC phase. Reversible ionic conductivity switching was observed upon irradiation of the polymer/0.3 Li salt complex with alternate UV and visible irradiation. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 629–641

The performance of battery electrolytes depends on three independent transport properties: ionic conductivity, diffusion coefficient, and transference number. While rigorous experimental techniques for measuring conductivity and diffusion coefficients are well-established, popular techniques for measuring the transference number rely on the assumption of ideal solutions. We employ three independent techniques for measuring transference number, t+, in mixtures of polyethylene oxide (PEO) and lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) salt. Transference numbers obtained using the steady-state current method pioneered by Bruce and Vincent, t+,SS, and those obtained by pulsed-field gradient NMR, t+,NMR, are compared against a new approach detailed by Newman and coworkers, t+,Ne, for a range of salt concentrations. The latter approach is rigorous and based on concentrated solution theory, while the other two approaches only yield the true transference number in ideal solutions. Not surprisingly, we find that t+,SS and t+,NMR are positive throughout the entire salt concentration range, and decrease monotonically with increasing salt concentration. In contrast, t+,Ne has a non-monotonic dependence on salt concentration and is negative in the highly-concentrated regime. Our work implies that ion transport in PEO/LiTFSI electrolytes at high salt concentrations is dominated by the transport of ionic clusters.

Effects of Halloysite Nanotubes on Ionic Conductivity, Morphology, Crystallinity and Mechanical Properties of PEO-based Solid Polymer Electrolyte

In recent years, the flexibility of porous organic polymers has demonstrated very unique properties during their applications. This paper reports a novel soluble porous polymer (named BIT-POP-75 and BIT-POP-75-OH) with 1,2-diketone and 1,2-diol subunits in the flexible polymer chain using contorted subunits. The solubility of the porous polymer and the flexible chelating 1,2-diol moiety facilitates the high loading and uniform dispersion of Pd nanoparticles to give the catalyst Pd@BIT-POP-75-OH, which shows high efficiency (kapp = 0.965 min-1) for the catalytic reduction of 4-nitrophenol with good recyclability (10 cycles).

Polymer Ni–MH battery based on PEO–PVA–KOH polymer electrolyte

Synergy of PVDF-HFP and ZIF-8 promotes PEO electrolyte towards all-solid-state lithium battery

EFFORTS to develop a high-voltage, lightweight rechargeable battery for electrically powered vehicles have focused on batteries based on solid electrolytes, which offer good mechanical strength, easy packaging and high energy densities. An important objective is to identify an electrolyte with the desired combination of mechanical properties, electrical conductivity and stability against powerfully oxidizing and reducing electrodes (lithium is preferred for the anode). Among the most promising materials are rubbery 'salt-in-polymer' electrolytes and highly conducting but brittle superionic glass electrolytes. In the latter category are salts with good lithium-ion conductivity, which are compatible with lithium-anode systems. Here we describe new ionic conductors — 'polymer-in-salt' materials — in which lithium salts are mixed with small quantities of the polymers polypropylene oxide and polyethylene oxide. These materials have glass transitions low enough to remain rubbery at room temperature while preserving good lithium-ion conductivities and high electrochemical stability.

Mesoporous silica (MPS) was used for poly(ethylene oxide) (PEO)-based solid polymer electrolytes as novel inorganic filler. For improvement in ionic conductivity in solid state, a room temperature ionic liquid (IL), 1-ethyl-3-methylimidazolium tetrafluoroborate, was introduced into periodic nano-tunnels of MPS, and the modified MPS (IL-MPS) was filled with PEO-LiBF4 electrolyte. Ionic conductivity of neat-MPS-filled composites was approximately 4-fold higher than that of the original electrolyte. On the other hand, the conductivity was more than 11-fold enhanced by addition of IL-MPS, to be more than 10−6 S/cm at 30°C and at least 10 wt% silica contents. The conductivity increased with increasing IL-MPS contents, to be a maximum value of approximately 3×10−6 S/cm at 30°C and at 40 wt%. Dynamic mechanical measurements for neat- and IL-MPS composites revealed that the addition of fillers improves storage modulus of PEO-based electrolytes at room temperature. The addition of IL-MPS was able to realize the improvement in both ionic conductivity and storage modulus.

Development of a new plasticizer for poly(ethylene oxide)-based polymer electrolyte and the investigation of their ion-pair dissociation effect

One pot synthesis of unsymmetrical ketones from carboxylic and boronic acids via PyClU-mediated acylative Suzuki coupling

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