Functional lithium borate salts and their potential application in high performance lithium batteries

Designer Anions for Better Rechargeable Lithium Batteries and Beyond

Non-aqueous electrolytes, generally consisting of metal salts and solvating media, are indispensable elements for building rechargeable batteries. As the major sources of ionic charges, the intrinsic characters of salt anions are of particular importance in determining the fundamental properties of bulk electrolyte, as well as the features of the resulting electrode-electrolyte interphases/interfaces. To cope with the increasing demand for better rechargeable batteries requested by emerging application domains, the structural design and modifications of salt anions are highly desired. Here, salt anions for lithium and other monovalent (e.g., sodium and potassium) and multivalent (e.g., magnesium, calcium, zinc, and aluminum) rechargeable batteries are outlined. Fundamental considerations on the design of salt anions are provided, particularly involving specific requirements imposed by different cell chemistries. Historical evolution and possible synthetic methodologies for metal salts with representative salt anions are reviewed. Recent advances in tailoring the anionic structures for rechargeable batteries are scrutinized, and due attention is paid to the paradigm shift from liquid to solid electrolytes, from intercalation to conversion/alloying-type electrodes, from lithium to other kinds of rechargeable batteries. The remaining challenges and key research directions in the development of robust salt anions are also discussed.

A B- and F-enriched buffering interphase enables a high-rate and high-stability SiOx/C anode

A facile, universal surface engineering strategy is proposed to address the volume expansion and slow kinetic issues encountered by SiOx/C anodes. A B-/F-enriched buffering interphase is introduced onto SiOx/C by thermal treatment of pre-adsorbed lithium salts at 400 °C. The as-prepared anode integrates both high-rate performance and long-term cycling durability.

Highly Oxidative-Resistant Cyano-Functionalized Lithium Borate Salt for Enhanced Cycling Performance of Practical Lithium-Ion Batteries

Lithium difluoro(oxalato) borate (LiDFOB) has been widely investigated in lithium-ion batteries (LIBs) owing to its advantageous thermal stability and excellent aluminum passivation property. However, LiDFOB tends to suffer from severe decomposition and generate a lot of gas species (e.g., CO2 ). Herein, a novel cyano-functionalized lithium borate salt, namely lithium difluoro(1,2-dihydroxyethane-1,1,2,2-tetracarbonitrile) borate (LiDFTCB), is innovatively synthesized as a highly oxidative-resistant salt to alleviate above dilemma. It is revealed that the LiDFTCB-based electrolyte enables LiCoO2 /graphite cells with superior capacity retention at both room and elevated temperatures (e.g., 80 % after 600 cycles) with barely any CO2 gas evolution. Systematic studies reveal that LiDFTCB tends to form thin and robust interfacial layers at both electrodes. This work emphasizes the crucial role of cyano-functionalized anions in improving cycle lifespan and safety of practical LIBs.

Opportunities of Flexible and Portable Electrochemical Devices for Energy Storage: Expanding the Spotlight onto Semi-solid/Solid Electrolytes

The ever-increasing demand for flexible and portable electronics has stimulated research and development in building advanced electrochemical energy devices which are lightweight, ultrathin, small in size, bendable, foldable, knittable, wearable, and/or stretchable. In such flexible and portable devices, semi-solid/solid electrolytes besides anodes and cathodes are the necessary components determining the energy/power performances. By serving as the ion transport channels, such semi-solid/solid electrolytes may be beneficial to resolving the issues of leakage, electrode corrosion, and metal electrode dendrite growth. In this paper, the fundamentals of semi-solid/solid electrolytes (e.g., chemical composition, ionic conductivity, electrochemical window, mechanical strength, thermal stability, and other attractive features), the electrode-electrolyte interfacial properties, and their relationships with the performance of various energy devices (e.g., supercapacitors, secondary ion batteries, metal-sulfur batteries, and metal-air batteries) are comprehensively reviewed in terms of materials synthesis and/or characterization, functional mechanisms, and device assembling for performance validation. The most recent advancements in improving the performance of electrochemical energy devices are summarized with focuses on analyzing the existing technical challenges (e.g., solid electrolyte interphase formation, metal electrode dendrite growth, polysulfide shuttle issue, electrolyte instability in half-open battery structure) and the strategies for overcoming these challenges through modification of semi-solid/solid electrolyte materials. Several possible directions for future research and development are proposed for going beyond existing technological bottlenecks and achieving desirable flexible and portable electrochemical energy devices to fulfill their practical applications. It is expected that this review may provide the readers with a comprehensive cross-technology understanding of the semi-solid/solid electrolytes for facilitating their current and future researches on the flexible and portable electrochemical energy devices.

Multifunctional Electrolyte Additive for Bi-electrode Interphase Regulation and Electrolyte Stabilization in Li/LiNi0.8Co0.1Mn0.1O2 Batteries

Rechargeable lithium metal batteries (LMBs) with high energy densities can be achieved by coupling a lithium metal anode (LMA) and a LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) cathode. Nevertheless, Li dendrite growth on the LMA surface and structural collapse of the NCM811 material, closely tied with the fragile cathode-/solid-electrolyte interphases (CEI/SEI) and corrosive hydrogen fluoride (HF), seriously deteriorate their performances. Herein, trimethylsilyl trifluoroacetate (TMSTFA) as a multifunctional electrolyte additive is proposed for regulation of the CEI/SEI films and elimination of HF. For one thing, the TMSTFA-derived CEI film rich in C-O species is conductive to Li⁺ transport and structural stability of NCM811 materials, and the TMSTFA-derived SEI film mainly consisting of inorganics (Li₂CO₃ and LiF) and organics (C-O and O-C═O species) can significantly promote Li⁺ homogeneous deposition and impede the Li dendrite growth. For another thing, the undesired reactions of the solvents and LiPF₆ salt are effectively retarded by the TMSTFA additive. Consequently, in the presence of TMSTFA, the capacity retention of Li/NCM811 cell is increased by 17% after 200 cycles at 1C, and the lifespan of symmetrical Li/Li cells is prolonged beyond 600 h at 0.5 mA cm^-2.

The Effect of LiBOB Addition on Solid Polymer Electrolyte (SPE) Production based PVDF-HFP/TiO2/LiTFSI on Ionic Conductivity for Lithium-Ion Battery Applications

SPE (Solid Polymer Electrolyte) is an alternative to substitute conventional liquid electrolytes as it has a better safety level and has been produced using the solution casting method. An effort to increase the SPE conductivity of the PVDF-HFP/TiO2/ LiTFSI system has been carried out by adding LiBOB as an additive. LiBOB (lithium bis(oxalate) borate) is a salt compound that can interfere with the crystallization process of polymer chains, so it is expected to increase ion conductivity. However, the results showed a decrease in the conductivity from 3.643 x 10-5 S/cm to 8.658 x 10-6 S/cm. These results were proven by the XRD, FTIR, SEM, and TGA characterization. Based on XRD (X-ray Diffraction) analysis, the addition of LiBOB increased the crystallinity phase. The results of the SEM (Scanning Electron Microscope) analysis showed that the pore size was partially reduced, the distance between the pores became longer, and the pore closure occurred due to agglomeration. The FTIR (Fourier Transform Infrared spectroscopy) analysis showed the interaction of LiBOB salts in the PVDF-HFP/LiTFSI/TiO2 system, and based on TGA (Thermogravimetric Analysis) analysis, the addition of LiBOB affected the heat stability of the SPE. The CV (Cyclic Voltammetry) analysis showed that the addition of LiBOB in the SPE system could reduce the reversibility and magnitude of the current.

Designing Versatile Polymers for Lithium-Ion Battery Applications: A Review

Solid-state electrolytes are a promising family of materials for the next generation of high-energy rechargeable lithium batteries. Polymer electrolytes (PEs) have been widely investigated due to their main advantages, which include easy processability, high safety, good mechanical flexibility, and low weight. This review presents recent scientific advances in the design of versatile polymer-based electrolytes and composite electrolytes, underlining the current limitations and remaining challenges while highlighting their technical accomplishments. The recent advances in PEs as a promising application in structural batteries are also emphasized.

Uncovering LiH Triggered Thermal Runaway Mechanism of a High-Energy LiNi0.5 Co0.2 Mn0.3 O2 /Graphite Pouch Cell

The continuous energy density increase of lithium ion batteries (LIBs) inevitably accompanies with the rising of safety concerns. Here, the thermal runaway characteristics of a high-energy 5 Ah LiNi0.5 Co0.2 Mn0.3 O2 /graphite pouch cell using a thermally stable dual-salt electrolyte are analyzed. The existence of LiH in the graphite anode side is innovatively identified in this study, and the LiH/electrolyte exothermic reactions and H2 migration from anode to cathode side are proved to contribute on triggering the thermal runaway of the pouch cell, while the phase transformation of lithiated graphite anode and the O2 -releasing from cathode are just accelerating factors for thermal runaway. In addition, heat determination during cycling at two boundary scenarios of adiabatic and isothermal environment clearly states the necessity of designing an efficient and smart battery thermal management system for avoiding heat accumulation. These findings will shed promising lights on thermal runaway route map depiction and thermal runaway prevention, as well as formulation of electrolyte for high energy safer LIBs.

The Necessity of Recycling of Waste Li-Ion Batteries Used in Electric Vehicles as Objects Posing a Threat to Human Health and the Environment

The automotive industry is one of the fastest-growing sectors of the modern economy. Growing customer expectations, implementing solutions related to electromobility, and increasingly stringent legal restrictions in the field of environmental protection, determine the development and introduction of innovative technologies in the field of car production. To power the most modern vehicles that include electric and hybrid cars, packages of various types of lithium-ion cells are used, the number of which is constantly growing. After use, these batteries, due to their complex chemical composition, constitute hazardous waste that is difficult to manage and must be recycled in modern technological lines. The article presents the morphological characteristics of the currently used types of Li-ion cells, and the threats to the safety of people and the environment that may occur in the event of improper use of Li-ion batteries and accumulators have been identified and described on the basis of the Regulation of the European Parliament and Council (EC) No. 1272/2008 of 16 December 2008 and No. 1907/2006 of 18 December 2006 on the classification, labeling and packaging of substances and mixtures and the registration, evaluation, authorization and restriction of chemicals (REACH), establishing the European Chemicals Agency.

Alkoxycyanoborates: metal salts and low-viscosity ionic liquids

Alkoxycyanoborates including low-viscosity ionic liquids which are promising materials in particular for electrochemical applications and Li[CH3OB(CN)3], which is a potential conducting salt, are presented.

Boron: Its Role in Energy-Related Processes and Applications

Boron's unique position in the Periodic Table, that is, at the apex of the line separating metals and nonmetals, makes it highly versatile in chemical reactions and applications. Contemporary demand for renewable and clean energy as well as energy-efficient products has seen boron playing key roles in energy-related research, such as 1) activating and synthesizing energy-rich small molecules, 2) storing chemical and electrical energy, and 3) converting electrical energy into light. These applications are fundamentally associated with boron's unique characteristics, such as its electron-deficiency and the availability of an unoccupied p orbital, which allow the formation of a myriad of compounds with a wide range of chemical and physical properties. For example, boron's ability to achieve a full octet of electrons with four covalent bonds and a negative charge has led to the synthesis of a wide variety of borate anions of high chemical and electrochemical stability-in particular, weakly coordinating anions. This Review summarizes recent advances in the study of boron compounds for energy-related processes and applications.

Single Lithium-Ion Conducting Solid Polymer Electrolyte with Superior Electrochemical Stability and Interfacial Compatibility for Solid-State Lithium Metal Batteries

Lithium metal batteries are being explored in meeting ever-increasing energy density needs. Because of serious dendritic lithium issues in liquid-state electrolytes, it is generally thought that solid-state electrolytes are potential alternatives for lithium metal batteries. Herein, we design a new single lithium-ion conducting lithium poly[(cyano)(4-styrenesulfonyl)imide] (LiPCSI) to replace the conventional dual-ion conducting salt for use in solid polymer electrolytes (SPEs) that successfully suppress the growth of lithium dendrites. Owing to highly delocalized anion moiety and oxidation-resistant cyano group, the tailored PEO₈-LiPCSI SPE exhibits extremely high Li⁺ transference number (0.84) as well as oxidation potential (5.53 V vs Li⁺/Li). The symmetric Li/PEO₈-LiPCSI/Li cell runs for 1000 h at 60 °C without a short circuit. The rechargeable solid-state Li/PEO₈-LiPCSI/LiFePO₄ cell discharges a capacity of 141 mAh g^-1 with retention over 85% during 80 cycles. These merits enable the proposed PEO₈-LiPCSI SPE to be very promising for solid-state lithium metal battery applications.

Degradation and Aging Routes of Ni-Rich Cathode Based Li-Ion Batteries

Driven by the increasing plea for greener transportation and efficient integration of renewable energy sources, Ni-rich metal layered oxides, namely NMC, Li [Ni1−x−yCoyMnz] O2 (x + y ≤ 0.4), and NCA, Li [Ni1−x−yCoxAly] O2, cathode materials have garnered huge attention for the development of Next-Generation lithium-ion batteries (LIBs). The impetus behind such huge celebrity includes their higher capacity and cost effectiveness when compared to the-state-of-the-art LiCoO2 (LCO) and other low Ni content NMC versions. However, despite all the beneficial attributes, the large-scale deployment of Ni-rich NMC based LIBs poses a technical challenge due to less stability of the cathode/electrolyte interphase (CEI) and diverse degradation processes that are associated with electrolyte decomposition, transition metal cation dissolution, cation–mixing, oxygen release reaction etc. Here, the potential degradation routes, recent efforts and enabling strategies for mitigating the core challenges of Ni-rich NMC cathode materials are presented and assessed. In the end, the review shed light on the perspectives for the future research directions of Ni-rich cathode materials.

Effect of anion dimensionality on optical properties: the ∞[B7O10(OH)2] layer in CsB7O10(OH)2vs. the ∞[B7O12] framework in CsBaB7O12

CsB₇O₁₀(OH)₂ with new FBB features a 2D anionic structure whose band gap is about 6.6 eV and CsBaB₇O₁₂ features a 3D anionic structure whose band gap is 5.6 eV. And their simulated birefringence are about 0.08 and 0.05 at 1064 nm, respectively.

Carboxylation Reactions with Carbon Dioxide Using N-Heterocyclic Carbene-Copper Catalysts

The development of versatile catalyst systems and new transformations for the utilization of carbon dioxide (CO₂ ) is of great interest and significance. This Personal Account reviews our studies on the exploration of the reactions of CO₂ with various substrates by the use of N-heterocyclic carbene (NHC)-copper catalysts. The carboxylation of organoboron compounds gave access to a wide range of carboxylic acids with excellent functional group tolerance. The C-H bond carboxylation with CO₂ emerged as a straightforward protocol for the preparation of a series of aromatic carboxylic esters and butenoates from simple substrates. The hydrosilylation of CO₂ with hydrosilanes provided an efficient method for the synthesis of silyl formate on gram scale. The hydrogenative or alkylative carboxylation of alkynes, ynamides and allenamides yielded useful α,β-unsaturated carboxylic acids and α,β-dehydro amino acid esters. The boracarboxylation of alkynes or aldehydes afforded the novel lithium cyclic boralactone or boracarbonate products, respectively. The NHC-copper catalysts generally featured excellent functional group compatibility, broad substrate scope, high efficiency, and high regio- and stereoselectivity. The unique electronic and steric properties of the NHC-copper units also enabled the isolation and structural characterization of some key intermediates for better understanding of the catalytic reaction mechanisms.

Additive-Assisted Novel Dual-Salt Electrolyte Addresses Wide Temperature Operation of Lithium-Metal Batteries

In this study, self-synthesized lithium trifluoro(perfluoro-tert-butyloxyl)borate (LiTFPFB) is combined with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) to formulate a novel 1 m dual-salt electrolyte, which contains lithium difluorophosphate (LiPO₂ F₂ ) additive and dominant carbonate solvents with low melting point and high boiling point. The addition of LiPO₂ F₂ into this novel dual-salt electrolyte dramatically improves cycleability and rate capability of a LiNi_0.5 Mn_0.3 Co_0.2 O₂ /Li (NMC/Li) battery, ranging from -40 to 90 °C. The NMC/Li batteries adopt a Li-metal anode with low thickness of 100 µm (even 50 µm) and a moderately high cathode mass loading level of 10 mg cm^-2 . For the first time, this paper provides valuable perspectives for developing practical lithium-metal batteries over a wide temperature range.

Effect of standard light illumination on electrolyte's stability of lithium-ion batteries based on ethylene and di-methyl carbonates

Combining energy conversion and storage at a device and/or at a molecular level constitutes a new research field raising interest. This work aims at investigating how prolonged standard light exposure (A.M. 1.5G) interacts with conventional batteries electrolyte, commonly used in the photo-assisted or photo-rechargeable batteries, based on 1 mol.L^-1 LiPF₆ EC/DMC electrolyte. We demonstrate the intrinsic chemical robustness of this class of electrolyte in absence of any photo-electrodes. However, based on different steady-state and time-resolved spectroscopic techniques, it is for the first time highlighted that the solvation of lithium and hexafluorophosphate ions by the carbonates are modified by light exposure leading to absorbance and ionic conductivity modifications without detrimental effects onto the electrochemical properties.

Dendrite-Free Lithium Deposition via Flexible-Rigid Coupling Composite Network for LiNi0.5 Mn1.5 O4 /Li Metal Batteries

Notorious lithium dendrite causes severe capacity fade and harsh safety issues of lithium metal batteries, which hinder the practical applications of lithium metal electrodes in higher energy rechargeable batteries. Here, a kind of 3D-cross-linked composite network is successfully employed as a flexible-rigid coupling protective layer on a lithium metal electrode. During the plating/stripping process, the composite protective layer would enable uniform distribution of lithium ions in the adjacent regions of the lithium electrode, resulting in a dendrite-free deposition at a current density of 2 mA cm^-2 . The LiNi_0.5 Mn_1.5 O₄ -based lithium metal battery presents an excellent cycling stability at a voltage range of 3.5-5.0 V with the induction of 3D-cross-linked composite protective layer. From an industrial field application of view, thin lithium metal electrodes (40 µm, with 4 times excess lithium) can be used in LiNi_0.5 Mn_1.5 O₄ (with industrially significant loading of 18 mg cm^-2 and 2.6 mAh cm^-2 )-based lithium metal batteries, which reveals a promising opportunity for practical applicability in high energy lithium metal batteries.

High Electrochemical Performance of Nanotube Structured ZnS as Anode Material for Lithium⁻Ion Batteries

By using ZnO nanorods as an ideal sacrificial template, one-dimensional (1-D) ZnS nanotubes with a mean diameter of 10 nm were successfully synthesized by hydrothermal method. The phase composition and microstructure of the ZnS nanotubes were characterized by using XRD (X-ray diffraction), SEM (scanning electron micrograph), and TEM (transmission electronic microscopy) analysis. X-ray photoelectron spectroscopy (XPS) and nitrogen sorption isotherms measurements were also used to study the information on the surface chemical compositions and specific surface area of the sample. The prepared ZnS nanotubes were used as anode materials in lithium-ion batteries. Results show that the ZnS nanotubes deliver an impressive prime discharge capacity as high as 950 mAh/g. The ZnS nanotubes also exhibit an enhanced cyclic performance. Even after 100 charge/discharge cycles, the discharge capacity could still remain at 450 mAh/g. Moreover, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements were also carried out to evaluate the ZnS electrodes.

Active Mechanism of the Interphase Film-Forming Process for an Electrolyte Based on a Sulfolane Solvent and a Chelato-Borate Complex

Electrolytes based on sulfolane (SL) solvents and lithium bis(oxalato)borate (LiBOB) chelato-borate complexes have been reported many times for use in advanced lithium-ion batteries due to their many advantages. This study aims to clarify the active mechanism of the interphase film-forming process to optimize the properties of these batteries by experimental analysis and theoretical calculations. The results indicate that the self-repairing film-forming process during the first cycle is divided into three stages: the initial film formation with an electric field force of ∼1.80 V, the further growth of the preformation solid electrolyte interphase (SEI) film at ∼1.73 V, and the final formation of a complete SEI film at a potential below 0.7 V. Additionally, we can deduce that the decomposition of LiBOB and SL occurs throughout nearly the entire process of the formation of the SEI film. The decomposition product of BOB^- anions tends to form films with an irregular structure, whereas the decomposition product of SL is in favor of the formation of a uniform SEI film.

Reviving lithium cobalt oxide-based lithium secondary batteries-toward a higher energy density

This review summarizes the key challenges, effective modification strategies and perspectives regarding reviving lithium cobalt oxide-based lithium secondary batteries-toward a higher energy density.

Two Players Make a Formidable Combination: In Situ Generated Poly(acrylic anhydride-2-methyl-acrylic acid-2-oxirane-ethyl ester-methyl methacrylate) Cross-Linking Gel Polymer Electrolyte toward 5 V High-Voltage Batteries

Electrochemical performance of high-voltage lithium batteries with high energy density is limited because of the electrolyte instability and the electrode/electrolyte interfacial reactivity. Hence, a cross-linking polymer network of poly(acrylic anhydride-2-methyl-acrylic acid-2-oxirane-ethyl ester-methyl methacrylate) (PAMM)-based electrolyte was introduced via in situ polymerization inspired by "shuangjian hebi", which is a statement in a traditional Chinese Kungfu story similar to the synergetic effect of 1 + 1 > 2. A poly(acrylic anhydride) and poly(methyl methacrylate)-based system is very promising as electrolyte materials for lithium-ion batteries, in which the anhydride and acrylate groups can provide high voltage resistance and fast ionic conductivity, respectively. As a result, the cross-linking PAMM-based electrolyte possesses a significant comprehensive enhancement, including electrochemical stability window exceeding 5 V vs Li⁺/Li, an ionic conductivity of 6.79 × 10^-4 S cm^-1 at room temperature, high mechanical strength (27.5 MPa), good flame resistance, and excellent interface compatibility with Li metal. It is also demonstrated that this gel polymer electrolyte suppresses the negative effect resulting from dissolution of Mn²⁺ ions at 25 and 55 °C. Thus, the LiNi_0.5Mn_1.5O₄/Li and LiNi_0.5Mn_1.5O₄/Li₄Ti₅O₁₂ cells using the optimized in situ polymerized cross-linking PAMM-based gel polymer electrolyte deliver stable charging/discharging profiles and excellent rate performance at room temperature and even at 55 °C. These findings suggest that the cross-linking PAMM is an intriguing candidate for 5 V class high-voltage gel polymer electrolyte toward high-energy lithium-on batteries.

Transport and Association of Ions in Lithium Battery Electrolytes Based on Glycol Ether Mixed with Halogen-Free Orthoborate Ionic Liquid

Ion transport behaviour of halogen-free hybrid electrolytes for lithium-ion batteries based on phosphonium bis(salicylato)borate [P_4,4,4,8][BScB] ionic liquid mixed with diethylene glycol dibutyl ether (DEGDBE) is investigated. The Li[BScB] salt is dissolved at different concentrations in the range from 0.15 mol kg⁻¹ to 1.0 mol kg⁻¹ in a mixture of [P_4,4,4,8][BScB] and DEGDBE in 1:5 molar ratio. The ion transport properties of the resulting electrolytes are investigated using viscosity, electrical impedance spectroscopy and pulsed-Field Gradient (PFG) NMR. The apparent transfer numbers of ions are calculated from the diffusion coefficients measured by using PFG NMR. PFG NMR data suggested ion association upon addition of Li salt to the [P_4,4,4,8][BScB] in DEGDBE solution. This is further confirmed by liquid state ⁷Li and ¹¹B NMR, and FTIR spectroscopic techniques, which suggest strong interactions between the lithium cation and oxygen atoms of the [BScB]⁻ anion in the hybrid electrolytes.

A Superior Polymer Electrolyte with Rigid Cyclic Carbonate Backbone for Rechargeable Lithium Ion Batteries

The fabricating process of well-known Bellcore poly(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP)-based polymer electrolytes is very complicated, tedious, and expensive owing to containing a large amount of fluorine substituents. Herein, a novel kind of poly(vinylene carbonate) (PVCA)-based polymer electrolyte is developed via a facile in situ polymerization method, which possesses the merits of good interfacial compatibility with electrodes. In addition, this polymer electrolyte presents a high ionic conductivity of 5.59 × 10^-4 S cm^-1 and a wide electrochemical stability window exceeding 4.8 V vs Li⁺/Li at ambient temperature. In addition, the rigid cyclic carbonate backbone of poly(vinylene carbonate) endows polymer electrolyte a superior mechanical property. The LiFe_0.2Mn_0.8PO₄/graphite lithium ion batteries using this polymer electrolyte deliver good rate capability and excellent cyclability at room temperature. The superior performance demonstrates that the PVCA-based electrolyte via in situ polymerization is a potential alternative polymer electrolyte for high-performance rechargeable lithium ion batteries.

High-performance spinel-rich Li1.5MnTiO4+δ ultralong nanofibers as cathode materials for Li-ion batteries

Recently, composite materials based on Li-Mn-Ti-O system were developed to target low cost and environmentally benign cathodes for Li-ion batteries. The spinel-layered Li_1.5MnTiO_4+δ bulk particles showed excellent cycle stability but poor rate performance. To address this drawback, ultralong nanofibers of a Li_1.5MnTiO_4+δ spinel-layered heterostructure were synthesized by electrospinning. Uniform nanofibers with diameters of about 80 nm were formed of tiny octahedral particles wrapped together into 30 μm long fibers. The Li_1.5MnTiO_4+δ nanofibers exhibited an improved rate capability compared to both Li_1.5MnTiO_4+δ nanoparticles and bulk particles. The uniform one-dimensional nanostructure of the composite cathode exhibited enhanced capacities of 235 and 170 mAh g⁻¹ at C/5 and 1 C rates, respectively. Its unique structure provided a large effective contact area for Li⁺ diffusion, and low charge transfer resistance. Moreover, the layered phase contributed to its capacity in over 3 V region, which increased specific energy (726 Wh kg⁻¹) compared to the bulk particles (534 Wh kg⁻¹).

Facile and Reliable in Situ Polymerization of Poly(Ethyl Cyanoacrylate)-Based Polymer Electrolytes toward Flexible Lithium Batteries

Polycyanoacrylate is a very promising matrix for polymer electrolyte, which possesses advantages of strong binding and high electrochemical stability owing to the functional nitrile groups. Herein, a facile and reliable in situ polymerization strategy of poly(ethyl cyanoacrylate) (PECA) based gel polymer electrolytes (GPE) via a high efficient anionic polymerization was introduced consisting of PECA and 4 M LiClO₄ in carbonate solvents. The in situ polymerized PECA gel polymer electrolyte achieved an excellent ionic conductivity (2.7 × 10^-3 S cm^-1) at room temperature, and exhibited a considerable electrochemical stability window up to 4.8 V vs Li/Li⁺. The LiFePO₄/PECA-GPE/Li and LiNi_1.5Mn_0.5O₄/PECA-GPE/Li batteries using this in-situ-polymerized GPE delivered stable charge/discharge profiles, considerable rate capability, and excellent cycling performance. These results demonstrated this reliable in situ polymerization process is a very promising strategy to prepare high performance polymer electrolytes for flexible thin-film batteries, micropower lithium batteries, and deformable lithium batteries for special purpose.

New lithium borates with bistetrazolato2- and pyrazinediolato2- ligands - potentially interesting lithium electrolyte additives

We present a convenient synthesis of the first silylated bistetrazole via a catalyzed twin [2 + 3] cycloaddition of TMS-azide at cyanogen and its application to access bistetrazolatoborates, structurally characterized by a unique unsaturated ten-membered B₂N₄C₄ heterocyclic system. Furthermore, new borate anions with two pyrazine-2,3-diolato ligands were synthesized from tetrafluoroborate salts and structurally characterized. Their organic cation can be exchanged for Li⁺via cation exchange. The conceptual relation of these new salts to lithium ion battery bisoxalalatoborate additive LiBOB, a prominent solid electrolyte interface (SEI) generator, is discussed.

In Situ Generation of Poly (Vinylene Carbonate) Based Solid Electrolyte with Interfacial Stability for LiCoO2 Lithium Batteries

Nowadays it is extremely urgent to seek high performance solid polymer electrolyte that possesses both interfacial stability toward lithium/graphitic anodes and high voltage cathodes for high energy density solid state batteries. Inspired by the positive interfacial effect of vinylene carbonate additive on solid electrolyte interface, a novel poly (vinylene carbonate) based solid polymer electrolyte is presented via a facile in situ polymerization process in this paper. It is manifested that poly (vinylene carbonate) based solid polymer electrolyte possess a superior electrochemical stability window up to 4.5 V versus Li/Li+ and considerable ionic conductivity of 9.82 × 10-5 S cm-1 at 50 °C. Moreover, it is demonstrated that high voltage LiCoO2/Li batteries using this solid polymer electrolyte display stable charge/discharge profiles, considerable rate capability, excellent cycling performance, and decent safety characteristic. It is believed that poly (vinylene carbonate) based electrolyte can be a very promising solid polymer electrolyte candidate for high energy density lithium batteries.

Protic organic ionic plastic crystals based on a difunctional cation and the triflate anion: a new solid-state proton conductor

A new family of ammonium based organic ionic plastic crystals exhibits exciting solid-state proton conductivity.

A Gel-Polymer Sn-C/LiMn0.5Fe0.5PO4 Battery Using a Fluorine-Free Salt

Safety and environmental issues, because of the contemporary use of common liquid electrolytes, fluorinated salts, and LiCoO2-based cathodes in commercial Li-ion batteries, might be efficiently mitigated by employing alternative gel-polymer battery configurations and new electrode materials. Herein we study a lithium-ion polymer cell formed by combining a LiMn0.5Fe0.5PO4 olivine cathode, prepared by simple solvothermal pathway, a nanostructured Sn-C anode, and a LiBOB-containing PVdF-based gel electrolyte. The polymer electrolyte, here analyzed in terms of electrochemical stability by impedance spectroscopy (EIS) and voltammetry, reveals full compatibility for cell application. The LiBOB electrolyte salt and the electrochemically delithiaded Mn0.5Fe0.5PO4 have a higher thermal stability compared to conventional LiPF6 and Li0.5CoO2, as confirmed by thermogravimetric analysis (TGA) and by galvanostatic cycling at high temperature. LiMn0.5Fe0.5PO4 and Sn-C, showing in lithium half-cell a capacity of about 120 and 350 mAh g(-1), respectively, within the gelled electrolyte configuration are combined in a full Li-ion polymer battery delivering a stable capacity of about 110 mAh g(-1), with working voltage ranging from 2.8 to 3.6 V.