Explosion characteristics for Li-ion battery electrolytes at elevated temperatures

Thermal stability analysis of nitrile additives in LiFSI for lithium-ion batteries: An accelerating rate calorimetry study

Although lithium-ion batteries (LIBs) are extensively used as secondary storage energy devices, they also pose a significant fire and explosion hazard. Subsequently, thermal stability studies for LiPF6- and LiFSI-type electrolytes have been conducted extensively. However, the thermal characteristics of these electrolytes with thermally stable additives in a full cell assembly have yet to be explored. This study presents a comprehensive accelerating rate calorimetry (ARC) study. First, 1.2-Ah cells were prepared using a control commercial LiPF6 electrolyte and LiFSI with a specific succinonitrile additive and ethyl-methyl carbonate as a thermally stable electrolyte additive. The kinetic parameters involved in heat generation and their effects on the thermal properties of the ARC module were analyzed from the heat-wait-seek (HWS), self-heating (SH), and thermal runaway (TR) stages. The results indicate that the addition of a succinonitrile additive to the LiFSI electrolyte lowers the decomposition temperatures of the solid electrolyte interface (SEI) owing to polymerization with Li at the anode, while simultaneously increasing the activation energy of reaction temperatures at SEI between the separator and the electrolyte. The maximum thermal-runaway temperature decreased from 417 °C (ΔH = 5.26 kJ) (LiPF6) to 285 °C (ΔH = 2.068 kJ) (LiFSI + succinonitrile). This study provides key insights to the thermal characteristics of LiPF6 and LiFSI during the self-heating and thermal runaway stages and indicates a practical method for achieving thermally stable LIBs.

Lyotropic Lamellar Nanostructures Enabled High-Voltage Windows, Efficient Charge Transport, and Thermally Safe Solid-State Electrolytes for Lithium-Ion Batteries

Developing electrolytes combining solid-like instinct stability and liquid-like conducting performance will be satisfactory for efficient and durable Li-ion batteries. Herein lamellar lyotropic liquid crystals (LLCs) demonstrate high-voltage windows, efficient charge transport, and inherent thermal safety as solid-state electrolytes in lithium-ion batteries. Lamellar LLCs are simply prepared by nanosegregation of [C16Mim][BF4] and LiBF4/Propylene carbonate (PC) liquid solutions, which induce lamellar assembly of the liquids as dynamic conducting pathways. Broadened liquid conducting pathways will boost the conducting performance of the LLC electrolytes. The lyotropic lamellar nanostructures enable liquid-like ion conductivity of the LLC electrolytes at ambient temperatures, as well as provide solid-like stability for the electrolytes to resist high voltage and flammability overwhelming to LiBF4/PC liquid electrolytes. Despite minor consumption of PC solvents (34.5 wt.%), the lamellar electrolytes show energy conversion efficiency comparable to the liquid electrolytes (PC wt. 92.8%) in Li/LiFePO4 batteries under ambient temperatures even at a 2 C current density, and exhibit attractively robust stability after 200th cyclic charge/discharge even under 60 °C. The work demonstrates LLC electrolytes have great potential to supersede traditional liquid electrolytes for efficient and durable Lithium-ion (Li-ion) batteries.

Imidazole-Intercalated Cobalt Hydroxide Enabling the Li+ Desolvation/Diffusion Reaction and Flame Retardant Catalytic Dynamics for Lithium Ion Batteries

Lithium-ion batteries have found extensive applications due to their high energy density and low self-discharge rates, spanning from compact consumer electronics to large-scale energy storage facilities. Despite their widespread use, challenges such as inherent capacity degradation and the potential for thermal runaway hinder sustainable development. In this study, we introduce a unique approach to synthesize anode materials for lithium-ion batteries, specifically imidazole-intercalated cobalt hydroxide. This innovative material significantly enhances the Li+ desolvation/diffusion reaction and flame-retardant dynamics through complexing and catalytic synergetic effects. The lithium-ion batteries incorporating these materials demonstrate exceptional performance, boasting an impressive capacity retention of 997.91 mAh g-1 after 500 cycles. This achievement can be attributed to the optimization of the solid electrolyte interphase (SEI) interface engineering, effectively mitigating anode degradation and minimizing electrolyte consumption. Experimental and theoretical calculations validate these improvements. Importantly, imidazole intercalated Co(OH)2 (MI-Co(OH)2) exhibits a remarkable catalytic effect on electrolyte carbonization and the conversion of CO to CO2. This dual action suppresses smoke and reduces toxicity significantly. The presented work introduces a novel approach to realizing high-performance and safe lithium-ion batteries, addressing key challenges in the pursuit of sustainable energy solutions.

Layered porous Mn0.18V2O5@C with manganese and carbon provided by a metal-organic framework precursor as a cathode material for aqueous zinc-ion batteries

At present, vanadium-based cathodes for aqueous zinc-ion batteries (AZIBs) are limited by their slow reaction kinetics, poor electrical conductivity, and low capacity retention. To overcome these problems, here, we design a layered porous Mn0.18V2O5@C as the cathode material for AZIBs using a manganese-containing metal-organic framework as a template through a simple solvothermal method. Such an electrode delivers an excellent specific capacity (380 mA h g-1 at 0.1 A g-1) accompanied by superior cycling stability (about 85% capacity retention for 2000 cycles at 6 A g-1). The excellent electrochemical performance of Mn0.18V2O5@C is ascribed to the improved interface activity including smooth zinc ion transport, abundant ion reaction active sites and accelerated charge transfer resulting from the coordination of the porous structure, doped conductive carbon, and the stable channel structure derived from the pillar effect of doping manganese ions, preventing a premature collapse of the electrode structure. It is also revealed by structural evolution analysis that the residual zinc ions also combine with the original Mn0.18V2O5 to form a ZnxMnyV2O5 phase, which serves as an additional structural pillar and in the meantime, also participates in the following cycles. These favorable electrochemical results suggest that Mn0.18V2O5@C is a suitable cathode material for AZIBs.

Detailed characterization of particle emissions due to thermal failure of batteries with different cathodes

Sufficient levels of thermal, electrical, mechanical, or electrochemical abuse can cause thermal runaway in lithium-ion batteries, leading to the release of electrolyte vapor, combustible gas mixtures, and high-temperature particles. Particle emissions due to thermal failure of batteries may cause serious pollution of the atmosphere, water sources, and soil as well as enter the human biological chain through crops, posing a potential threat to human health. Furthermore, high-temperature particle emissions may ignite the flammable gas mixtures produced during the thermal runaway process, resulting in combustion and explosions. This research focused on determining the particle size distribution, elemental composition, morphology, and crystal structure of particles released from different cathode batteries after thermal runaway. Accelerated adiabatic calorimetry tests were performed on a fully charged Li(Ni0.3Co0.3Mn0.3)O2 battery (NCM111), Li(Ni0.5Co0.2Mn0.3)O2 battery (NCM523), and Li(Ni0.6Co0.2Mn0.2)O2 battery (NCM622). Results of all three batteries indicate that particles with a diameter less than or equal to 0.85 mm exhibit an increase in volume distribution followed by a decrease in volume distribution as the diameter increases. F, S, P, Cr, Ge, and Ge were detected in particle emissions with mass percentages ranging from 6.5% to 43.3%, 0.76-1.20%, 2.41-4.83%,1.8-3.7%, and 0-0.14%, respectively. When present in high concentrations, these may have negative impacts on human health and the environment. In addition, the diffraction patterns of the particle emissions were approximately the same for NC111, NCM523, and NCM622, with emissions primarily composed of Ni/Co elemental, graphite, Li2CO3, NiO, LiF, MnO, and LiNiO2. This study can provide important insights into the potential environmental and health risks associated with particle emissions from thermal runaway in lithium-ion batteries.

Non-Newtonian fluid gating membranes with acoustically responsive and self-protective gas transport control

Control of gas transport through porous media is desired in multifarious processes such as chemical reactions, interface absorption, and medical treatment. Liquid gating technology, based on dynamically adaptive interfaces, has been developed in recent years and has shown excellent control capability in gas manipulation-the reversible opening and closing of a liquid gate for gas transport as the applied pressure changes. Here, we report a new strategy to achieve self-protective gas transport control by regulating the dynamic porous interface in a non-Newtonian fluid gating membrane based on the shear thickening fluid. The gas transport process can be suspended and restored via modulation of the acoustic field, owing to the transition of particle-to-particle interactions in a confined geometry. Our experimental and theoretical results support the stability and tunability of the gas transport control. In addition, relying on the shear thickening behaviour of the gating fluid, the transient response can be achieved to resist high-impact pressure. This strategy could be utilized to design integrated smart materials used in complex and extreme environments such as hazardous and explosive gas transportation.

From symmetry breaking in the bulk to phase transitions at the surface: a quantum-mechanical exploration of Li6PS5Cl argyrodite superionic conductor

Lithium superionic conductor electrolytes may enable the safe use of metallic lithium anodes in all-solid-state batteries. The key to a successful application is a high Li conductivity in the electrolyte material, to be achieved through the maintenance of intimate contact with the electrodes and the knowledge of the chemical nature of that contact. In this manuscript, we tackle this issue by a theoretical ab initio approach. Focusing on the Li₆PS₅Cl, a thiophosphate with high ionic conductivity, we carry on thorough modeling of the surfaces together with the prediction of the thermal and elastic behaviour. Our investigation leads to some new findings: the bulk structure, as reported in the literature, appears to be metastable, with spontaneous symmetry breaking. Moreover, the relevant stoichiometric surfaces identified for stable and metastable crystal structures are not up-down symmetry related and they expose from one side Li₂S and LiCl. Surface reconstructions can be interpreted as local phase transitions. We also predict entirely ab initio the morphology of crystallites, charge, and electrostatic potential at surfaces, together with the effect of temperature on structural properties and the elastic behaviour of this material. Such findings may constitute the relevant groundwork for a better understanding of ionic transport in Li-ion conductors at the electrolyte/anode and electrolyte/cathode interfaces.

Sensing Leakage of Electrolytes from Magnesium Batteries Enabled by Natural AIEgens

The potential for leakage of liquid electrolytes from magnesium (Mg) batteries represents a large hurdle to future application. Despite this, there are no efficient sensing technologies to detect the leakage of liquid electrolytes. Here, we developed a sensor using laccaic acid (L-AIEgen), a naturally occurring aggregation-induced emission luminogen (AIEgens) isolated from the beetle Laccifer lacca. L-AIEgen showed good selectivity and sensitivity for Mg²⁺, a universal component of electrolytes in Mg batteries. Using L-AIEgen, we then produced a smart film (L-AIE-F) that was able to sense leakage of electrolytes from Mg batteries. L-AIE-F showed a strong "turn-on" AIE-active fluorescence at the leakage point of electrolyte from model Mg batteries. To the best of our knowledge, this is the first time that AIE technology has been used to sense the leakage of electrolytes.

Fast Ionic Storage in Aqueous Rechargeable Batteries: From Fundamentals to Applications

The highly dynamic nature of grid-scale energy systems necessitates fast kinetics in energy storage and conversion systems. Rechargeable aqueous batteries are a promising energy-storage solution for renewable-energy grids as the ionic diffusivity in aqueous electrolytes can be up to 1-2 orders of magnitude higher than in organic systems, in addition to being highly safe and low cost. Recent research in this regard has focussed on developing suitable electrode materials for fast ionic storage in aqueous electrolytes. In this review, breakthroughs in the field of fast ionic storage in aqueous battery materials, and 1D/2D/3D and over-3D-tunnel materials are summarized, and tunnels in over-3D materials are not oriented in any direction in particular. Various materials with different tunnel sizes are developed to be suitable for the different ionic radii of Li⁺ , Na⁺ , K⁺ , H⁺ , NH₄ ⁺ , and Zn²⁺ , which show significant differences in the reaction kinetics of ionic storage. New topochemical paths for ion insertion/extraction, which provide superfast ionic storage, are also discussed.

Electrochemical Corrosion Behavior of Iron in Lithium-ion Battery Electrolyte

The element iron (Fe) is affordable and abundantly available, and thus, it finds use in a wide range of applications. As regards its application in rechargeable lithium-ion batteries (LIBs), the electrochemical reactions of Fe must be clearly understood during battery charging and discharging with the LIB electrolyte. In this study, we conducted systematic electrochemical analyses under various voltage conditions to determine the voltage at which Fe corrosion begins in general lithium salts and organic solvents used in LIBs. During cyclic voltammetry (CV) experiments, we observed a large corrosion current above 4.0 V (vs. Li/Li+). When a constant voltage of 3.7 V (vs. Li/Li+), was applied, the current did not increase significantly at the beginning, similar to the CV scenario; on the other hand, at a voltage of 3.8 V (vs. Li/Li+), the current increased rapidly. The impact of this difference was visually confirmed via scanning electron microscopy and optical microscopy. Our X-ray photoelectron spectroscopy measurements showed that at 3.7 V, a thick organic solid electrolyte interphase (SEI) was formed atop a thin fluoride SEI, which means that at ≥3.8 V, the SEI cannot prevent Fe corrosion. This result confirms that Fe corrosion begins at 3.7 V, beyond which Fe is easily corrodible.

A comparative study on the thermal runaway inhibition of 18650 lithium-ion batteries by different fire extinguishing agents

Safety issue of lithium-ion batteries (LIBs) is always a concern. We have studied the inhabitation on thermal runaway (TR) and propagation of 18,650 LIBs in an enclosed space systematically. LIBs at 70% state of charge are chosen for testing. Four fire extinguishing agents are applied on LIB arrays for 20 s, and the inhibiting effects are different. The cooling efficiency varies with the surface temperatures of LIBs. Water spray has the highest cooling efficiency and inhibits the TR propagation among LIB arrays successfully. Three LIBs undergo TR for the releasing of ABC ultrafine dry powder. BC ultrafine dry powder and Novec 1230 are failed to inhibit the TR propagation. Nevertheless, Novec 1230 shows the best on inhibiting fire occurring and the generation of toxic gas. Generally, this study provides valuable information for the choice of fire extinguishing agents.

Infiltrated and Isostatic Laminated NCM and LTO Electrodes with Plastic Crystal Electrolyte Based on Succinonitrile for Lithium-Ion Solid State Batteries

We report a new process technique for electrode manufacturing for all solid-state batteries. Porous electrodes are manufactured by a tape casting process and subsequently infiltrated by a plastic crystal polymer electrolyte (PCPE). With a following isostatic lamination process, the PCPE was further integrated deeply into the porous electrode layer, forming a composite electrode. The PCPE comprises the plastic crystal succinonitrile (SN), lithium conductive salt LiTFSI and polyacrylonitrile (PAN) and exhibits suitable thermal, rheological (ƞ = 0.6 Pa s @ 80 °C 1 s−1) and electrochemical properties (σ > 10−4 S/cm @ 45 °C). We detected a lowered porosity of infiltrated and laminated electrodes through Hg porosimetry, showing a reduction from 25.6% to 2.6% (NCM infiltrated to laminated) and 32.9% to 4.0% (LTO infiltrated to laminated). Infiltration of PCPE into the electrodes was further verified by FESEM images and EDS mapping of sulfur content of the conductive salt. Cycling tests of full cells with NCM and LTO electrodes with PCPE separator at 45 °C showed up to 165 mAh/g at 0.03C over 20 cycles, which is about 97% of the total usable LTO capacity with a coulomb efficiency of between 98 and 99%. Cycling tests at 0.1C showed a capacity of ~128 mAh/g after 40 cycles. The C-rate of 0.2C showed a mean capacity of 127 mAh/g. In summary, we could manufacture full cells using a plastic crystal polymer electrolyte suitable for NCM and LTO active material, which is easily to be integrated into porous electrodes and which is being able to be used in future cell concepts like bipolar stacked cells.

A Novel Silicon/Phosphorus Co-Flame Retardant Polymer Electrolyte for High-Safety All-Solid-State Lithium Ion Batteries

Developing a solid polymer electrolyte with superior flame retardancy and lithium-ion transportation properties is still a challenge. Herein, an intrinsic silicon/phosphorus co-flame retardant polymer solid electrolyte was prepared by using polyethylene glycol (PEG) co-polymerized with silicon and phosphorus-containing monomers. Due to the synergistic flame-retardant effect of silicon and phosphorus elements, this polymer electrolyte exhibits excellent thermal stability and flame resistance. Moreover, the ionic conductivity of the electrolyte at 25 °C is as high as 2.98 × 10⁻⁵ S/cm when the mass ratio of LiN(SO₂CF₃)₂ (LiTFSI) and the prepared polymer electrolyte is 10:1. What is more, the LiFePO₄/Li all-solid-state battery assembled with this solid electrolyte can work stably at a high temperature of 60 °C and exhibits a specific capacity of 129.2 mAh/g at 0.2 C after 100 cycles, providing a promising application prospect for high-safety lithium-ion batteries.