Boehmite-based Microcapsules as Flame-retardants for Lithium-ion Batteries

Bio-Inspired Core-Shell Structured Electrode Particles with Protective Mechanisms for Lithium-Ion Batteries

Lithium-ion batteries (LIBs), as predominant energy storage devices, are applied to electric vehicles, which is an effective way to achieve carbon neutrality. However, the major obstructions to their applications are two dilemmas: enhanced cyclic life and thermal stability. Taking advantage of bio-inspired core-shell structures to optimize the self-protective mechanisms of the mercantile electrode particles, LIBs can improve electrochemical performance and thermal stability simultaneously. The favorable core-shell structures suppress volume expansion to stabilize electrode-electrolyte interfaces (EEIs), mitigate direct contact between the electrode material and electrolyte, and promote electrical connectivity. They possess wide operating temperatures, high-voltage resistance, and inhibit short circuits. During cycling, the cathode and anode generate a cathode-electrolyte interface (CEI) and a solid-electrolyte interface (SEI), respectively. Applying multitudinous coating approaches can generate multifarious bio-inspired core-shell structured electrode particles, which is helpful for the generation of the EEIs, self-healing the surface cracks, and maintaining the structural integrities of electrodes. The protected shells act as barriers to minimize unwanted side reactions and enhance thermal stability. These in-depth understandings of the bio-inspired evolution for electrode particles can inspire further enhancements in LIB lifetime and thermal safety, especially for bio-inspired core-shell structured electrodes possessing high-performance protective mechanisms.

Sapiential battery systems: beyond traditional electrochemical energy

As indispensable energy-storage technology in modern society, batteries play a crucial role in diverse fields of 3C products, electric vehicles, and electrochemical energy storage. However, with the growing demand for future electrochemical energy devices, lithium-ion batteries as an existing advanced battery system face a series of significant challenges, such as time-consuming manual material screening, safety concerns, performance degradation, non-access in the off-grid state, poor environmental adaptability, and pollution from waste batteries. Accordingly, incorporating the characteristics of sapiential life into batteries to construct sapiential systems is one of the most engaging tactics to tackle the above issues. In this review, we introduce the concept of sapiential battery systems and provide a comprehensive overview of their core sapiential features, including materials genomics, non-destructive testing, self-healing, self-sustaining capabilities, temperature adaptation, and degradability, which endow batteries with higher performance and more functions. Moreover, the possible future research directions on sapiential battery systems are deeply discussed. This review aims to offer insights for designing beyond traditional electrochemical energy, meeting broader application scenarios such as ultra-long-endurance electric vehicles, wide-temperature energy storage, space exploration, and wearable electronic devices.

Bionic Capsule Lithium-Ion Battery Anodes for Efficiently Inhibiting Volume Expansion

Magnetite (Fe3O4) has a large theoretical reversible capacity and rich Earth abundance, making it a promising anode material for LIBs. However, it suffers from drastic volume changes during the lithiation process, which lead to poor cycle stability and low-rate performance. Hence, there is an urgent need for a solution to address the issue of volume expansion. Taking inspiration from how glycophyte cells mitigate excessive water uptake/loss through their cell wall to preserve the structural integrity of cells, we designed Fe3O4@PMMA multi-core capsules by microemulsion polymerization as a kind of anode materials, also proposed a new evaluation method for real-time repair effect of the battery capacity. The Fe3O4@PMMA anode shows a high reversible specific capacity (858.0 mAh g-1 at 0.1 C after 300 cycles) and an excellent cycle stability (450.99 mAh g-1 at 0.5 C after 450 cycles). Furthermore, the LiNi0.8Co0.1Mn0.1O2/Fe3O4@PMMA pouch cells exhibit a stable capacity (200.6 mAh) and high-capacity retention rate (95.5 %) after 450 cycles at 0.5 C. Compared to the original battery, the capacity repair rate of this battery is as high as 93.4 %. This kind of bionic capsules provide an innovative solution for improving the electrochemical performance of Fe3O4 anodes to promote their industrial applications.

Bio-Inspired Electrodes with Rational Spatiotemporal Management for Lithium-Ion Batteries

Lithium-ion batteries (LIBs) are currently the predominant energy storage power source. However, the urgent issues of enhancing electrochemical performance, prolonging lifetime, preventing thermal runaway-caused fires, and intelligent application are obstacles to their applications. Herein, bio-inspired electrodes owning spatiotemporal management of self-healing, fast ion transport, fire-extinguishing, thermoresponsive switching, recycling, and flexibility are overviewed comprehensively, showing great promising potentials in practical application due to the significantly enhanced durability and thermal safety of LIBs. Taking advantage of the self-healing core-shell structures, binders, capsules, or liquid metal alloys, these electrodes can maintain the mechanical integrity during the lithiation-delithiation cycling. After the incorporation of fire-extinguishing binders, current collectors, or capsules, flame retardants can be released spatiotemporally during thermal runaway to ensure safety. Thermoresponsive switching electrodes are also constructed though adding thermally responsive components, which can rapidly switch LIB off under abnormal conditions and resume their functions quickly when normal operating conditions return. Finally, the challenges of bio-inspired electrode designs are presented to optimize the spatiotemporal management of LIBs. It is anticipated that the proposed electrodes with spatiotemporal management will not only promote industrial application, but also strengthen the fundamental research of bionics in energy storage.

Side Reactions/Changes in Lithium-Ion Batteries: Mechanisms and Strategies for Creating Safer and Better Batteries

Lithium-ion batteries (LIBs), in which lithium ions function as charge carriers, are considered the most competitive energy storage devices due to their high energy and power density. However, battery materials, especially with high capacity undergo side reactions and changes that result in capacity decay and safety issues. A deep understanding of the reactions that cause changes in the battery's internal components and the mechanisms of those reactions is needed to build safer and better batteries. This review focuses on the processes of battery failures, with voltage and temperature as the underlying factors. Voltage-induced failures result from anode interfacial reactions, current collector corrosion, cathode interfacial reactions, overcharge, and over-discharge, while temperature-induced failure mechanisms include SEI decomposition, separator damage, and interfacial reactions between electrodes and electrolytes. The review also presents protective strategies for controlling these reactions. As a result, the reader is offered a comprehensive overview of the safety features and failure mechanisms of various LIB components.

Class of Boehmite/Polyacrylonitrile Membranes with Different Thermal Shutdown Temperatures for High-Performance Lithium-Ion Batteries

Nowadays, lithium-ion batteries are required to have a higher energy density and safety because of their wide applications. Current commercial separators have poor wettability and thermal stability, which significantly impact the performance and safety of batteries. In this study, a class of boehmite particles with different grain sizes was synthesized by adjusting hydrothermal temperatures and used to fabricate boehmite/polyacrylonitrile (BM/PAN) membranes. All of these BM/PAN membranes can not only maintain excellent thermal dimensional stability above 200 °C but also have good electrolyte wettability and high porosity. More interestingly, the BM/PAN membranes' thermal shutdown temperature can be adjusted by changing the grain size of boehmite particles. The lithium-ion batteries assembled with BM/PAN separators exhibit different thermal stability phenomena at 150 °C and have excellent rate performance and cycle stability at room temperature. After 120 cycles at 1C, the LiFePO₄ half-cell assembled by the best BM/PAN separator has almost unchanged discharge capacity, whereas the capacity retention of Celgard 2325 is only about 85%. Meanwhile, the NCM523 half-cell assembled with the best BM/PAN separator shows superb cycle stability after 500 cycles at 8C, with a capacity retention of 79% compared with 56% for Celgard 2325.

A Review of Environmentally Friendly Approaches in Fire Extinguishing: From Chemical Sciences to Innovations in Electrical Engineering

After the invention of fire, the fight against fire probably started, and it has been going on for thousands of years. During this time, the aim has always been to extinguish the fire as soon as possible and to produce fire-resistant materials. Symmetry plays an important role in reducing problems, as it is a common feature of modern life. Multidimensional signal processing has many applications, an example of which is the use of appropriately timed acoustic waves to extinguish flames. This article provides a brief review of issues related to the use of acoustic waves for flame suppression based on studies in the literature. In addition, measurement results available in the literature obtained using a high-power acoustic extinguisher are discussed as a review of the scientific literature. Furthermore, we provide the latest information on the situation of flame retardants, including the latest innovations in basic sciences. In this sense, from intrinsically fire-resistant materials to flame-retardant additives and nanocomposites, new processes and applications are briefly mentioned.

Bioinspired Thermal Runaway Retardant Capsules for Improved Safety and Electrochemical Performance in Lithium-Ion Batteries

Vigorous development of electric vehicles is one way to achieve global carbon reduction goals. However, fires caused by thermal runaway of the power battery has seriously hindered large-scale development. Adding thermal runaway retardants (TRRs) to electrolytes is an effective way to improve battery safety, but it often reduces electrochemical performance. Therefore, it is difficult to apply in practice. TRR encapsulation is inspired by the core-shell structures such as cells, seeds, eggs, and fruits in nature. In these natural products, the shell isolates the core from the outside, and has to break as needed to expose the core, such as in seed germination, chicken hatching, etc. Similarly, TRR encapsulation avoids direct contact between the TRR and the electrolyte, so it does not affect the electrochemical performance of the battery during normal operation. When lithium-ion battery (LIB) thermal runaway occurs, the capsules release TRRs to slow down and even prevent further thermal runaway. This review aims to summarize the fundamentals of bioinspired TRR capsules and highlight recent key progress in LIBs with TRR capsules to improve LIB safety. It is anticipated that this review will inspire further improvement in battery safety, especially for emerging LIBs with high-electrochemical performance.

High-Safety and Long-Life Silicon-Based Lithium-Ion Batteries via a Multifunctional Binder

Lithium-ion batteries with high energy density and good safety are in urgent demand nowadays. Silicon has the advantages of high theoretical capacity, low cost, and vast reserves. It is regarded as an ideal anode material for high-energy lithium-ion batteries. Unfortunately, its huge volume change during cycling results in unstable cycle behavior and limits its application. To develop a robust electrode by employing effective binders is still a big challenge. Furthermore, both conventional binders and organic liquid electrolytes bring serious safety risks due to their flammability. Herein, a flame-retardant binder is designed and prepared by cross-linking polyacrylic acid (PAA) with a flame-retardant epoxy resin (FREP) containing phosphorus and nitrogen elements. Compared with PAA, it has better wettability to liquid electrolytes. Moreover, the three-dimensional PAA-FREP polymer binder not only provides sufficient mechanical strength to buffer the volume change of Si powders but also enhances the interfacial adhesion between the active film and Cu current collector via epoxy groups. Most importantly, the FREP component in the binder leads to admirable flame retardance. In these ways, the multifunctional binder exhibits excellent mechanical, electrochemical, and safety performances.

New Approach for the Synthesis of Nanozirconia Fortified Microcapsules

Robust poly(urea-formaldehyde) (PUF) microcapsules with composite shells comprising zirconia (ZrO₂) nanopowder incorporated in PUF were fabricated via a novel and facile one-pot synthesis. ZrO₂ nanopowder was chosen because it owns one of the highest mechanical strengths among ceramics. The nanopowder was predispersed in the core material to combine encapsulation and fortification into a single process. In the core, the well-dispersed nanopowder migrated to the interface, where PUF polymerization took place. The mechanical strength of the microcapsule with nano-ZrO₂ incorporated in the shell (42% by weight) is three times greater than that of the microcapsule without ZrO₂. In a preliminary application wherein the microcapsules were embedded in a model of poly(vinyl alcohol) (PVA) membrane, the PVA specimen exhibited a higher ultimate tensile strength when fortified microcapsules were embedded than when unfortified microcapsules were used.