2,3,4,5,6-Pentafluorophenyl Methanesulfonate as a Versatile Electrolyte Additive Matches LiNi0.5Co0.2Mn0.3O2/Graphite Batteries Working in a Wide-Temperature Range

A Functional Electrolyte Containing P-Phenyl Diisothiocyanate (PDITC) Additive Achieves the Interphase Stability of High Nickel Cathode in a Wide Temperature Range

The lithium-ion batteries (LIBs) with high nickel cathode have high specific energy, but as the nickel content in the cathode active material increases, batteries are suffering from temperature limitations, unstable performance, and transition metal dissolution during long cycling. In this work, a functional electrolyte with P-phenyl diisothiocyanate (PDITC) additive is developed to stabilize the performance of LiNi0.8 Co0.1 Mn0.1 O2 (NCM811)/graphite LIBs over a wide temperature range. Compared to the batteries without the additive, the capacity retention of the batteries with PDITC-containing electrolyte increases from 23 % to 74 % after 1400 cycles at 25 °C, and from 15 % to 85 % after 300 cycles at 45 °C. After being stored at 60 °C, the capacity retention rate and capacity recovery rate of the battery are also improved. In addition, the PDITC-containing battery has a higher discharge capacity at -20 °C, and the capacity retention rate increases from 79 % to 90 % after 500 cycles at 0 °C. Both theoretical calculations and spectroscopic results demonstrate that PDITC is involved in constructing a dense interphase, inhibiting the decomposition of the electrolyte and reducing the interfacial impedance. The application of PDITC provides a new strategy to improve the wide-temperature performance of the NCM811/graphite LIBs.

Electrolyte Design for Lithium-Ion Batteries for Extreme Temperature Applications

With increasing energy storage demands across various applications, reliable batteries capable of performing in harsh environments, such as extreme temperatures, are crucial. However, current lithium-ion batteries (LIBs) exhibit limitations in both low and high-temperature performance, restricting their use in critical fields like defense, military, and aerospace. These challenges stem from the narrow operational temperature range and safety concerns of existing electrolyte systems. To enable LIBs to function effectively under extreme temperatures, the optimization and design of novel electrolytes are essential. Given the urgency for LIBs operating in extreme temperatures and the notable progress in this research field, a comprehensive and timely review is imperative. This article presents an overview of challenges associated with extreme temperature applications and strategies used to design electrolytes with enhanced performance. Additionally, the significance of understanding underlying electrolyte behavior mechanisms and the role of different electrolyte components in determining battery performance are emphasized. Last, future research directions and perspectives on electrolyte design for LIBs under extreme temperatures are discussed. Overall, this article offers valuable insights into the development of electrolytes for LIBs capable of reliable operation in extreme conditions.

Laser-Triggered High Graphitization of Mo2C@C: High Rate Performance and Excellent Cycling Stability as Anode of Lithium Ion Batteries

Fast electron/ion transport and cycling stability of anode materials are key factors for achieving a high rate performance of battery materials. Herein, we successfully fabricated a carbon-coated Mo2C nanofiber (denoted as laser Mo2C@C) as the lithium ion battery anode material by laser carbonization of PAN-PMo12 (PAN = Polyacrylonitrile; PMo12 = H3PMo12O40). The highly graphitized carbon layer in laser Mo2C@C effectively protects Mo2C from agglomeration and flaking while facilitating electron transfer. As such, the laser Mo2C@C electrode displays an excellent electrochemical stability under 5 A g-1, with a capacity up to 300 mA h g-1 after 3000 cycles. Furthermore, the extended X-ray absorption fine structure results show the existence of some Mo vacancies in Mo2C@C. Density functional theory calculations further prove that such vacancies make the defective Mo2C@C composites energetically more favorable for lithium storage in comparison with the intact Mo2C.

Organosulfur Materials for Rechargeable Batteries: Structure, Mechanism, and Application

Lithium-ion batteries have received significant attention over the last decades due to the wide application of portable electronics and increasing deployment of electric vehicles. In order to further enhance the performance of the batteries and overcome the capacity limitations of inorganic electrode materials, it is imperative to explore new cathode and functional materials for rechargeable lithium batteries. Organosulfur materials containing sulfur-sulfur bonds as a kind of promising organic electrode materials have the advantages of high capacities, abundant resources, tunable structures, and environmental benignity. In addition, organosulfur materials have been widely used in almost every aspect of rechargeable batteries because of their multiple functionalities. This review aims to provide a comprehensive overview on the development of organosulfur materials including the synthesis and application as cathode materials, electrolyte additives, electrolytes, binders, active materials in lithium redox flow batteries, and other metal battery systems. We also give an in-depth analysis of structure-property-performance relationship of organosulfur materials, and guidance for the future development of organosulfur materials for next generation rechargeable lithium batteries and beyond.

Lithium-Ion Batteries under Low-Temperature Environment: Challenges and Prospects

Lithium-ion batteries (LIBs) are at the forefront of energy storage and highly demanded in consumer electronics due to their high energy density, long battery life, and great flexibility. However, LIBs usually suffer from obvious capacity reduction, security problems, and a sharp decline in cycle life under low temperatures, especially below 0 °C, which can be mainly ascribed to the decrease in Li⁺ diffusion coefficient in both electrodes and electrolyte, poor transfer kinetics on the interphase, high Li⁺ desolvation barrier in the electrolyte, and severe Li plating and dendrite. Targeting such issues, approaches to improve the kinetics and stability of cathodes are also dissected, followed by the evaluation of the application prospects and modifications between various anodes and the strategies of electrolyte design including cosolvent, blended Li salts, high-concentration electrolyte, and additive introduction. Such designs elucidate the successful exploration of low-temperature LIBs with high energy density and long lifespan. This review prospects the future paths of research for LIBs under cold environments, aiming to provide insightful guidance for the reasonable design of LIBs under low temperature, accelerating their widespread application and commercialization.

Stabilizing the cycling stability of rechargeable lithium metal batteries with tris(hexafluoroisopropyl)phosphate additive

The application of rechargeable lithium metal batteries (LMBs) has been hindered by the fast growth of lithium dendrites during charge and the limited cycling life because of the decomposition of the electrolyte at the interface. Here, we have developed a non-flammable triethyl phosphate (TEP)-based electrolyte with tris(hexafluoroisopropyl)phosphate (THFP) as an additive. The polar nature of the C-F bonding and the rich CF₃ groups in THFP lowers its LUMO energy and HOMO energy to help form a stable, LiF-rich solid electrolyte interphase (SEI) layer through the reduction of THFP and increases the binding ability of the PF₆^- anions, which significantly suppresses lithium dendrite growth and reduces the electrolyte decomposition. Moreover, THFP participates in the formation of a thin, C-F rich electrolyte interphase (CEI) layer to provide the stable cycling of the cathode at a high voltage. The symmetric Li||Li and full Li/NCM622 cells with THFP additive have small polarization and long cycling life, which demonstrates the importance of the additive to the application of the LMBs.

Stable Electrode/Electrolyte Interface for High-Voltage NCM 523 Cathode Constructed by Synergistic Positive and Passive Approaches

Increasing the working voltage of lithium-ion batteries (LIBs) is an efficient way to increase energy density. However, high voltage triggers excessive electrolyte decomposition at the electrode-electrolyte interfaces, where the electrochemical performance such as cyclic stability and rate capability is seriously deteriorated. A new synergistic positive and passive approach is proposed in this work to construct a stable electrode-electrolyte interface at high voltage. As a positive approach, inorganic lithium sulfide salt (Li₂S) is used as an electrolyte additive to build a stable cathode electrolyte interface (CEI) at the LiNi_0.5Co_0.2Mn_0.3O₂ (NCM523) cathode surface. In a passive way, acetonitrile (AN) is applied as a solvent additive to suppress oxidative decomposition of a carbonate electrolyte via preferential solvation with a lithium ion. Because of the synergistic interaction between the positive and passive approaches, the cyclic stabilities of NCM523/Li cells improved with a tiny amount of Li₂S (0.01 mg mL^-1) and AN (0.5 vol %). The capacity retention increased to 80.74% after 200 cycles compared to the cells with the blank electrolyte (67.98%) and AN-containing electrolyte (75.8%). What is more, the capacity retention of the NCM523/graphite full cell is increased from 65 to 81% with the addition of the same amount of Li₂S and AN after 180 cycles. The mechanism is revealed on the basis of the theoretical calculations and various characterizations. The products derived from the preferential adsorption and oxidation of Li₂S on the surface of NCM523 effectively increase the content of inorganic ingredients. However, the presence of AN prevents oxidation of the solvent. This study provides new principle guiding studies on a high-voltage lithium-ion battery with excellent electrochemical performance.

Low-Temperature Electrolyte Design for Lithium-Ion Batteries: Prospect and Challenges

Lithium-ion batteries have dominated the energy market from portable electronic devices to electric vehicles. However, the LIBs applications are limited seriously when they were operated in the cold regions and seasons if there is no thermal protection. This is because the Li+ transportation capability within the electrode and particularly in the electrolyte dropped significantly due to the decreased electrolyte liquidity, leading to a sudden decline in performance and short cycle-life. Thus, design a low-temperature electrolyte becomes ever more important to enable the further applications of LIBs. Herein, we summarize the low-temperature electrolyte development from the aspects of solvent, salt, additives, electrolyte analysis, and performance in the different battery systems. Then, we also introduce the recent new insight about the cation solvation structure, which is significant to understand the interfacial behaviors at the low temperature, aiming to guide the design of a low-temperature electrolyte more effectively.

Electrolyte Design for Lithium Metal Anode-Based Batteries Toward Extreme Temperature Application

Lithium anode-based batteries (LBs) are highly demanded in society owing to the high theoretical capacity and low reduction potential of metallic lithium. They are expected to see increasing deployment in performance critical areas including electric vehicles, grid storage, space, and sea vehicle operations. Unfortunately, competitive performance cannot be achieved when LBs operating under extreme temperature conditions where the lithium-ion chemistry fail to perform optimally. In this review, a brief overview of the challenges in developing LBs for low temperature (<0 °C) and high temperature (>60 °C) operation are provided followed by electrolyte design strategies involving Li salt modification, solvation structure optimization, additive introduction, and solid-state electrolyte utilization for LBs are introduced. Specifically, the prospects of using lithium metal batteries (LMBs), lithium sulfur (Li-S) batteries, and lithium oxygen (Li-O2 ) batteries for performance under low and high temperature applications are evaluated. These three chemistries are presented as prototypical examples of how the conventional low temperature charge transfer resistances and high temperature side reactions can be overcome. This review also points out the research direction of extreme temperature electrolyte design toward practical applications.

Novel Low-Temperature Electrolyte Using Isoxazole as the Main Solvent for Lithium-Ion Batteries

A novel electrolyte system with an excellent low-temperature performance for lithium-ion batteries (LIBs) has been developed and studied. It was discovered for the first time, in this work, that when isoxazole (IZ) was used as the main solvent, the ionic conductivity of the electrolyte for LIBs is more than doubled in a temperature range between -20 and 20 °C compared to the baseline electrolyte using ethylene carbonate-ethyl methyl carbonate as solvents. To solve the problem of solvent co-intercalation into the graphite anode and/or electrolyte decomposition, the lithium difluoro(oxalato)borate (LiDFOB) salt and fluoroethylene carbonate (FEC) additive were used to form a stable solid electrolyte interphase on the surface of the graphite anode. Benefitting from the high ionic conductivity at low temperature, cells using a new electrolyte with 1 M LiDFOB in FEC/IZ (1:10, vol %) solvents demonstrated a very high reversible capacity of 187.5 mAh g^-1 at -20 °C, while the baseline electrolyte only delivered a reversible capacity of 23.1 mAh g^-1.

A Novel Electrolyte Additive Enables High-Voltage Operation of Nickel-Rich Oxide/Graphite Cells

Nickel-rich oxide/graphite cells under high voltage operation provide high energy density but present short cycle life because of the parasitic electrolyte decomposition reactions. In this work, we report a novel electrolyte additive, N,O-bis(trimehylsilyl)-trifluoroacetamide (NOB), which enables nickel-rich oxide/graphite cells to operate stably under high voltage. When evaluated in a nickel-rich oxide-based full cell, LiNi_0.5Co_0.2Mn_0.3O₂ (NCM523)/graphite using a carbonate electrolyte, 1 wt % NOB provides the cell with capacity retention improved from 38% to 73% after 100 cycles at 1C under 4.5 V. It is found that NOB is able to eliminate hydrogen fluoride in the electrolyte. The radicals resulting from the interaction of NOB with the fluoride ion can be preferentially oxidized on the cathode compared with the electrolyte solvents, with its reaction products constructing N-containing interphases simultaneously on the cathode and anode, which suppress the parasitic electrolyte decomposition reactions, leading to the significantly improved cycle stability of nickel-rich oxide/graphite cells under high voltage.

Benzoic Anhydride as a Bifunctional Electrolyte Additive for Hydrogen Fluoride Capture and Robust Film Construction over High-Voltage Li-Ion Batteries

High-voltage LiNi_0.8 Co_0.1 Mn_0.1 O₂ (NCM811)-based Li-ion batteries (LIBs) with enhanced performance can be achieved by properly tailoring the electrolyte systems. Benzoic anhydride (BA) was proposed here as a promising bifunctional electrolyte additive that can not only construct a robust cathode-electrolyte interface (CEI) film on the electrode surface but also capture HF/H₂ O in the electrolyte effectively. Compared to the cell without the BA additive, the capacity of Li/NCM811 half-cell with 1.0 wt % BA was increased from 128.5 to 149.6 mAh g^-1 after 200 cycles at 1 C between 3.0 and 4.3 V. Even at a higher cut-off voltage of 4.5 V, the BA-containing Li/NCM811 half-cell delivered a capacity retention of 69 % after 200 cycles, much higher than that of the half-cell without the additive (56 %). Both theoretical calculation and experimental results verified that the BA additive could be preferentially oxidized to form a stable interface film with high conductivity that protected the NCM811 cathode and suppressed the decomposition of the electrolyte.

1-(2-Cyanoethyl)pyrrole enables excellent battery performance at high temperature via the synergistic effect of Lewis base and C[triple bond, length as m-dash]N functional groups

The electrolyte of a lithium ion battery is unstable and is easily decomposed at high temperature, which can lead to the degradation of battery performance. To solve this problem, herein a novel electrolyte additive 1-(2-cyanoethyl)pyrrole (CP) has been proposed to improve the electrochemical performance of LiFePO4 batteries at high temperature. The capacity retention of the battery with 1 wt% CP is 76.7%, while that of the battery without the additive is 38.1% after 200 cycles at 60 °C. Theoretical calculation results reveal that the binding energy of CP and PF5/HF is much higher than that of the solvents in the electrolyte. Surface analysis of the electrodes demonstrates that CP can reduce the decomposition of the electrolyte, and restrain the dissolution of transition metals in the electrolyte at high temperature. TEM/XPS results indicate that CP can modify the protective film on the surface of the cathode material and promote the formation of more regular and thinner CEI films. The promotion of the CP additive is of great significance for improving the high temperature performance of lithium ion batteries and is expected to be applied on a large scale.

Tailoring Low-Temperature Performance of a Lithium-Ion Battery via Rational Designing Interphase on an Anode

Performances of lithium-ion batteries at subambient temperatures are extremely restricted by the resistive interphases originated from electrolyte decomposition, especially on the anode surface. This work reports a novel strategy that an anode interphase of low impedance is constructed by applying an electrolyte additive dimethyl sulfite (DMS). Electrochemical measurements indicate that the as-constructed interphase provides graphite/LiNi_0.5Co_0.2Mn_0.3O₂ pouch cells with excellent low-temperature performance, outperforming the interphase constructed by 1,3,2-dioxathiolane 2,2-dioxide (DTD), a common commercially used electrolyte additive. Spectral characterizations in combination with theoretical calculations demonstrate that the improved performance is attributed to the unique molecular structure of DMS, which presents appropriate reduction activity and constructs the more stable and ionically conductive anode interphase due to the weaker combination of its reduction product with lithium ions than DTD. This rational design of interphases via an additive structure has been proven to be a low cost but rather an effective approach to tailor the performances of lithium-ion batteries.

A Simple Method for the Complete Performance Recovery of Degraded Ni-rich LiNi0.70Co0.15Mn0.15O2 Cathode via Surface Reconstruction

The highly active surfaces of Ni-rich cathodes usually result in rapid surface degradation, which is manifested by poor cycle and rate capabilities. In this work, we propose a simple method to restore those degraded surfaces after storage. More importantly, the mechanism of surface degradation and recovery are investigated thoroughly. As storage in moist air, a lithium carbonate (Li₂CO₃) dominated impurity layer formed and tightly coated on the surface of the LiNi_0.70Co_0.15Mn_0.15O₂ particles. Except for the Li₂CO₃ layer, a NiO rock-salt structure was also found at near surface region by high-resolution transmission electron microscopy. These two inert species together impedance the transport of lithium ions and electrons, which result in no capacity at 4.3 V charge cutoff voltage of the stored material. We proposed a simple and effective method, i.e., three h calcination at 800 °C under oxygen flow. The restored LiNi_0.70Co_0.15Mn_0.15O₂ shows equivalent electrochemical performance compared to the pristine one. This is because the lithium ions in Li₂CO₃ layer return to the surface lattice of LiNi_0.70Co_0.15Mn_0.15O₂, and the NiO cubic phase transforms back to the layered structure with the oxidation of Ni²⁺. This method is not only insightful for cathode material design but also beneficial for practical application.