Capacity Fading Mechanism in Lithium-Sulfur Battery using Poly(ionic liquid) Gel Electrolyte

Tuning the D-Band Center of Bi2S3─MoS2 Heterostructure Towards Superior Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries are one of the most promising energy storage devices due to their environmental friendliness, low cost, and high specific capacity. However, the slow electrochemical kinetics and the "shuttle effect" have seriously hindered their commercialization. Herein, the nanoflower Bi2S3─MoS2 (BMS) heterostructure is synthesized by a two-step hydrothermal method, and then the Bi2S3─MoS2-Polypropylene (BMS-PP) interlayer is constructed. The heterostructure is rich in active sites, in which BMS has strong adsorption to lithium polysulfides (LiPSs) and can effectively anchor LiPSs while catalyzing LiPSs and promote the redox of Li2S at the same time, which can improve the utilization of active substances. More importantly, the d-band center can be tuned by the formation of Bi2S3─MoS2 heterostructure. Thus, Li-S batteries containing the BMS-PP interlayer show excellent rate performance (841.6 mAh g-1 at 5 C) and cycling performance (70.3% capacity retention after 500 cycles at 3 C). This work provides a new route for high-performance lithium-sulfur batteries.

Effect of Cross-Linking and Surface Treatment on the Functional Properties of Electrospun Polybenzimidazole Separators for Lithium Metal Batteries

In this work, electrospun PBI separators with a highly porous structure and nanofiber diameter of about 90-150 nm are prepared using a multi-nozzle under controlled conditions for lithium metal batteries. Cross-linking with α, α-dibromo-p-xylene and surface treatment using 4-(chloromethyl) benzoic acid successfully improve the electrochemical as well as mechanical properties of the separators. The resulting separator is endowed with high thermal stability and excellent wettability (1080 to 1150%) with commercial liquid electrolyte than PE and PP (Celgard 2400) separators. Besides, attractive cycling stability and rate capability in LiFePO₄/Li cells are attained with the modified separators. Prominently, CROSSLINK PBI exhibits a stable Coulombic efficiency of more than 99% over 100 charge-discharge cycles at 0.5 C, which is superior to the value of cells using commercial PE and PP (Celgard 2400) separators. The half cells assembled using the CROSSLINK PBI separator can deliver a discharge capacity of 150.3 mAh g^-1 at 0.2 C after 50 cycles corresponding to 88.4% of the theoretical value of LiFePO₄ (170 mAh g^-1). This work offers a worthwhile method to produce thermally stable separators with noteworthy electrochemical performances which opens new possibilities to improve the safe operation of batteries.

A Novel Zwitterionic Ionic Liquid-Based Electrolyte for More Efficient and Safer Lithium-Sulfur Batteries

The shuttle effect of polysulfide and the flammability of the conventional electrolyte are the two major obstacles restricting the development progress of lithium-sulfur batteries. Exploring highly efficient electrolyte components coupled with the conventional electrolyte is a reliable strategy to solve these issues. However, the current electrolyte components usually relieve these issues at the expense of the sacrificed electrochemical performance. Herein, a novel zwitterionic ionic liquid named as TLTFSI is reported, which exhibits a high ionic conductivity of 3.7 × 10^-3 S cm^-1, a wide electrochemical potential window from 1.51 to 4.82 V at 25 °C, and a high thermal decomposition temperature of 275 °C. The optimized TLTFSI-based electrolyte is nonflammable and performs superior electrochemical performance in terms of larger capacity, better rate capability, and longer cyclic life compared with the conventional organic electrolyte. The robust performance is attributed to the high intrinsic ionic conductivity, the suppressed polysulfide dissolution/diffusion, and the high interface compatibility toward the lithium anode of the TLTFSI-based electrolytes. This present work represents the first demonstration of the zwitterionic ionic liquid to efficiently improve the overall electrochemical performance and the safety of lithium-sulfur batteries.

Reduced graphene oxide/TiO2(B) nanocomposite-modified separator as an efficient inhibitor of polysulfide shuttling in Li-S batteries

The shutting effect in lithium–sulfur (Li–S) batteries hinders their widespread application, which can be restrained effectively by a modified separator. In this work, a composite of reduced graphene oxide and beta-phase TiO₂ nanoparticles (RGO/TiO₂(B)) is designed as a separator modification material for improving the electrochemical behavior of Li–S batteries. The TiO₂(B) nanoparticles are in situ prepared and tightly adhere to the RGO layer. A series of examinations demonstrated that the RGO/TiO₂(B)-coated separator efficiently inhibits the polysulfide shuttling phenomenon by the cooperative effect of physical adsorption and chemical binding. Specifically, as modified separators, a comparison between TiO₂(B) and anatase TiO₂(A) each composited with RGO has been conducted. The TiO₂(B) sample not only exhibits a superior blocking character of migrating polysulfides, but also enhances battery electrochemical kinetics by fast Li ion diffusion.

Beta-phase TiO₂ nanoparticles were adhered onto RGO in situ to fabricate a multi-functional separator for high-performance lithium–sulfur (Li–S) batteries.

Sodium Batteries: A Review on Sodium-Sulfur and Sodium-Air Batteries

Lithium-ion batteries are currently used for various applications since they are lightweight, stable, and flexible. With the increased demand for portable electronics and electric vehicles, it has become necessary to develop newer, smaller, and lighter batteries with increased cycle life, high energy density, and overall better battery performance. Since the sources of lithium are limited and also because of the high cost of the metal, it is necessary to find alternatives. Sodium batteries have shown great potential, and hence several researchers are working on improving the battery performance of the various sodium batteries. This paper is a brief review of the current research in sodium-sulfur and sodium-air batteries.

Polycarboxylate Functionalized Graphene/S Composite Cathodes and Modified Cathode-Facing Side Coated Separators for Advanced Lithium-Sulfur Batteries

Sulfur-hosting novel materials as a cathode for lithium-sulfur batteries are in the focus of many research to enhance the specific capacity and cycling stability. Herein, we developed composite cathodes consisting of polycarboxylate functionalized graphene (PC-FGF) doped with TiO₂ nanoparticles or poly1,5-diaminoanthraquinone (PDAAQ) and sulfur to enhance chemisorption property toward polysulfides. Additionally, PC-FGF/sulfur composite cathode functions as an efficient trapping site for polysulfides spices as well as contributes to facilitate electron and Li-ions movement toward or from the cathode. In the first experiment, the cell with sulfur incorporated TiO₂/PC-FGF cathode is assembled with three different cathode-facing side-coated glass fiber separators. At the second test, PDAAQ/PC-FGF cathode is assembled with the same separator materials as before.The best electrochemical performance observed was sulfur incorporated TiO₂/PC-FGF cathode with PDAAQ/PC-FGF-coated separator having a high discharge capacity of 1100 mAh g^- 1 at 0.5 C after 100 cycles. It is found that the combination of TiO₂/PC-FGF/sulfur cathode and PDAAQ/PC-FCF separator could serve as promising cathode and separator material due to high cycling stability and rate capability for advanced Li-S batteries.

Energy-Density Improvement in Li-Ion Rechargeable Batteries Based on LiCoO2 + LiV3O8 and Graphite + Li-Metal Hybrid Electrodes

We developed a novel battery system consisting of a hybrid (LiCoO₂ + LiV₃O₈) cathode in a cell with a hybrid (graphite + Li-metal) anode and compared it with currently used systems. The hybrid cathode was synthesized using various ratios of LiCoO₂:LiV₃O₈, where the 80:20 wt% ratio yielded the best electrochemical performance. The graphite and Li-metal hybrid anode, the composition of which was calculated based on the amount of non-lithiated cathode material (LiV₃O₈), was used to synthesize a full cell. With the addition of LiV₃O₈, the discharge capacity of the LiCoO₂ + LiV₃O₈ hybrid cathode increased from 142.03 to 182.88 mA h g⁻¹ (a 28.76% improvement). The energy density of this cathode also increased significantly, from 545.96 to 629.24 W h kg⁻¹ (a 15.21% improvement). The LiCoO₂ + LiV₃O₈ hybrid cathode was characterized through X-ray diffraction analysis, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. Its electrochemical performance was analyzed using a battery-testing system and electrochemical impedance spectroscopy. We expect that optimized synthesis conditions will enable the development of a novel battery system with an increase in energy density and discharge capacity.

An Optimized Impedance Model for the Estimation of the State-of-Charge of a Li-Ion Cell: The Case of a LiFePO4 (ANR26650)

This article focused on the estimation of the state of charge (SoC) of a Li-con Cell by carrying out a series of experimental tests at various operating temperatures and SoC. The cell was characterized by electrochemical impedance spectroscopy (EIS) tests, from which the impedance frequency spectrum for different SoC and temperatures was obtained. Indeed, the cell model consisted of a modified Randles circuit type that included a constant phase element so-called Warburg impedance. Each circuit parameter was obtained from the EIS tests. The obtained were been used to develop two numerical models for each parameter, i.e., one based on numerical correlations and the other based on the artificial neural network (ANN) method. A genetic algorithm was used to solve and optimize the numerical models. The accuracy of the models was examined and the results showed that the ANN-based model was more accurate than the correlations-based model. The root mean square relative error (RMSRE) of the parameters Rs, R1, C1 and W for the ANN-based model were: 4.63%, 13.65%, 10.96% and 4.4%, respectively, compared to 7.09%, 27.45%, 34.36% and 7.07% for the correlations-based model, respectively. The SoC was estimated using the extended Kalman filter based on a Randles model, with an estimation RMSRE of about 1.19%.

Recent Advances in Non-Flammable Electrolytes for Safer Lithium-Ion Batteries

Lithium-ion batteries are the most commonly used source of power for modern electronic devices. However, their safety became a topic of concern after reports of the devices catching fire due to battery failure. Making safer batteries is of utmost importance, and several researchers are trying to modify various aspects in the battery to make it safer without affecting the performance of the battery. Electrolytes are one of the most important parts of the battery since they are responsible for the conduction of ions between the electrodes. In this paper, we discuss the different non-flammable electrolytes that were developed recently for safer lithium-ion battery applications.

Towards a Smarter Battery Management System for Electric Vehicle Applications: A Critical Review of Lithium-Ion Battery State of Charge Estimation

Energy storage system (ESS) technology is still the logjam for the electric vehicle (EV) industry. Lithium-ion (Li-ion) batteries have attracted considerable attention in the EV industry owing to their high energy density, lifespan, nominal voltage, power density, and cost. In EVs, a smart battery management system (BMS) is one of the essential components; it not only measures the states of battery accurately, but also ensures safe operation and prolongs the battery life. The accurate estimation of the state of charge (SOC) of a Li-ion battery is a very challenging task because the Li-ion battery is a highly time variant, non-linear, and complex electrochemical system. This paper explains the workings of a Li-ion battery, provides the main features of a smart BMS, and comprehensively reviews its SOC estimation methods. These SOC estimation methods have been classified into four main categories depending on their nature. A critical explanation, including their merits, limitations, and their estimation errors from other studies, is provided. Some recommendations depending on the development of technology are suggested to improve the online estimation.

Mechanism of Ionic Impedance Growth for Palladium-Containing CNT Electrodes in Lithium-Oxygen Battery Electrodes and its Contribution to Battery Failure

The electrochemical oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) and on CNT (carbon nanotube) cathode with a palladium catalyst, palladium-coated CNT (PC-CNT), and palladium-filled CNT (PF-CNT) are assessed in an ether-based electrolyte solution in order to fabricate a lithium-oxygen battery with high specific energy. The electrochemical properties of the CNT cathodes were studied using electrochemical impedance spectroscopy (EIS). Palladium-filled cathodes displayed better performance as compared to the palladium-coated ones due to the shielding of the catalysts. The mechanism of the improvement was associated to the reduction of the rate of resistances growth in the batteries, especially the ionic resistances in the electrolyte and electrodes. The scanning electron microscopy (SEM) and spectroscopy were used to analyze the products of the reaction that were adsorbed on the electrode surface of the battery, which was fabricated using palladium-coated and palladium-filled CNTs as cathodes and an ether-based electrolyte.

A 3D MoS₂/Graphene Microsphere Coated Separator for Excellent Performance Li-S Batteries

Lithium-sulfur (Li-S) batteries are the most prospective energy storage devices. Nevertheless, the poor conductivity of sulfur and the shuttling phenomenon of polysulfides hinder its application. In this paper, flower-like MoS₂/graphene nanocomposite is prepared and deposited on a multi-functional separator to enhance the electrochemical behavior of Li-S batteries. The results demonstrated that the MoS₂/graphene-coated separator is contributing to inhibit the shuttling phenomenon of polysulfides and improve the integrity of sulfur electrode. The initial discharge capacity of the battery using MoS₂/graphene-coated separator at 0.2 C was up to 1516 mAh g⁻¹. After 100 cycles, a reversible capacity of 880 mAh g⁻¹ and a coulombic efficiency of 98.7% were obtained. The improved electrochemical behavior can be due to the nanostructure and Mo-S bond of the MoS₂/graphene composite, which can combine physical shielding and chemisorption to prohibit the shuttle effect of polysulfides. The results prove that the MoS₂/graphene-coated separator has the potential for feasible application in Li-S batteries to enhance their electrochemical performance.