Smart Solid-State Interphases Enable High-Safety and High-Energy Practical Lithium Batteries.

With the electrochemical performance of batteries approaching the bottleneck gradually, it is increasingly urgent to solve the safety issue. Herein, all-in-one strategy is ingeniously developed to design smart, safe, and simple (3S) practical pouch-type LiNi0.8Co0.1Mn0.1O2||Graphite@SiO (NCM811||Gr@SiO) cell, taking full advantage of liquid and solid-state electrolytes. Even under the harsh thermal abuse and high voltage condition (100 °C, 3-4.5 V), the pouch-type 3S NCM811||Gr@SiO cell can present superior capacity retention of 84.6% after 250 cycles (based pouch cell: 47.8% after 250 cycles). More surprisingly, the designed 3S NCM811||Gr@SiO cell can efficiently improve self-generated heat T1 by 45 °C, increase TR triggering temperature T2 by 40 °C, and decrease the TR highest T3 by 118 °C. These superior electrochemical and safety performances of practical 3S pouch-type cells are attributed to the robust and stable anion-induced electrode-electrolyte interphases and local solid-state electrolyte protection layer. All the fundamental findings break the conventional battery design guidelines and open up a new direction to develop practical high-performance batteries.

In Situ Polymerization Facilitating Practical High-Safety Quasi-Solid-State Batteries.

Quasi-solid-state batteries (QSSBs) are gaining widespread attention as a promising solution to improve battery safety performance. However, the safety improvement and the underlying mechanisms of QSSBs remain elusive. Herein, a novel strategy combining high-safety ethylene carbonate-free liquid electrolyte and in situ polymerization technique is proposed to prepare practical QSSBs. The Ah-level QSSBs with LiNi0.83Co0.11Mn0.06O2 cathode and graphite-silicon anode demonstrate significantly improved safety features without sacrificing electrochemical performance. As evidenced by accelerating rate calorimetry tests, the QSSBs exhibit increased self-heating temperature and onset temperature (T2), and decreased temperature rise rate during thermal runaway (TR). The T2 has a maximum increase of 48.4 °C compared to the conventional liquid batteries. Moreover, the QSSBs do not undergo TR until 180 °C (even 200 °C) during the hot-box tests, presenting significant improvement compared to the liquid batteries that run into TR at 130 °C. Systematic investigations show that the in situ formed polymer skeleton effectively mitigates the exothermic reactions between lithium salts and lithiated anode, retards the oxygen release from cathode, and inhibits crosstalk reactions between cathode and anode at elevated temperatures. The findings offer an innovative solution for practical high-safety QSSBs and open up a new sight for building safer high-energy-density batteries.

Sub-millisecond lithiothermal synthesis of graphitic meso-microporous carbon.

Porous carbons with concurrently high specific surface area and electronic conductivity are desirable by virtue of their desirable electron and ion transport ability, but conventional preparing methods suffer from either low yield or inferior quality carbons. Here we developed a lithiothermal approach to bottom-up synthesize highly meso-microporous graphitized carbon (MGC). The preparation can be finished in a few milliseconds by the self-propagating reaction between polytetrafluoroethylene powder and molten lithium (Li) metal, during which instant ultra-high temperature (>3000 K) was produced. This instantaneous carbon vaporization and condensation at ultra-high temperatures and in ultra-short duration enable the MGC to show a highly graphitized and continuously cross-coupled open pore structure. MGC displays superior electrochemical capacitor performance of exceptional power capability and ultralong-term cyclability. The processes used to make this carbon are readily scalable to industrial levels.

Large-scale assembly of isotropic nanofiber aerogels based on columnar-equiaxed crystal transition.

Ice-templating technology holds great potential to construct industrial porous materials from nanometers to the macroscopic scale for tailoring thermal, electronic, or acoustic transport. Herein, we describe a general ice-templating technology through freezing the material on a rotating cryogenic drum surface, crushing it, and then re-casting the nanofiber slurry. Through decoupling the ice nucleation and growth processes, we achieved the columnar-equiaxed crystal transition in the freezing procedure. The highly random stacking and integrating of equiaxed ice crystals can organize nanofibers into thousands of repeating microscale units with a tortuous channel topology. Owing to the spatially well-defined isotropic structure, the obtained Al2O3·SiO2 nanofiber aerogels exhibit ultralow thermal conductivity, superelasticity, good damage tolerance, and fatigue resistance. These features, together with their natural stability up to 1200 °C, make them highly robust for thermal insulation under extreme thermomechanical environments. Cascading thermal runaway propagation in a high-capacity lithium-ion battery module consisting of LiNi0.8Co0.1Mn0.1O2 cathode, with ultrahigh thermal shock power of 215 kW, can be completely prevented by a thin nanofiber aerogel layer. These findings not only establish a general production route for nanomaterial assemblies that is conventionally challenging, but also demonstrate a high-energy-density battery module configuration with a high safety standard that is critical for practical applications.

All-temperature area battery application mechanism, performance, and strategies.

Further applications of electric vehicles (EVs) and energy storage stations are limited because of the thermal sensitivity, volatility, and poor durability of lithium-ion batteries (LIBs), especially given the urgent requirements for all-climate utilization and fast charging. This study comprehensively reviews the thermal characteristics and management of LIBs in an all-temperature area based on the performance, mechanism, and thermal management strategy levels. At the performance level, the external features of the batteries were analyzed and compared in cold and hot environments. At the mechanism level, the heat generation principles and thermal features of LIBs under different temperature conditions were summarized from the perspectives of thermal and electrothermal mechanisms. At the strategy level, to maintain the temperature/thermal consistency and prevent poor subzero temperature performance and local/global overheating, conventional and novel battery thermal management systems (BTMSs) are discussed from the perspective of temperature control, thermal consistency, and power cost. Moreover, future countermeasures to enhance the performance of all-climate areas at the material, cell, and system levels are discussed. This study provides insights and methodologies to guarantee the performance and safety of LIBs used in EVs and energy storage stations.

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.

Thermal Runaway of Nonflammable Localized High-Concentration Electrolytes for Practical LiNi0.8 Mn0.1 Co0.1 O2 |Graphite-SiO Pouch Cells.

With continuous improvement of batteries in energy density, enhancing their safety is becoming increasingly urgent. Herein, practical high energy density LiNi0.8 Mn0.1 Co0.1 O2 |graphite-SiO pouch cell with nonflammable localized high concentration electrolyte (LHCE) is proposed that presents unique self-discharge characteristic before thermal runaway (TR), thus effectively reducing safety hazards. Compared with the reference electrolyte, pouch cell with nonflammable LHCE can increase self-generated heat temperature by 4.4 °C, increase TR triggering temperature by 47.3 °C, decrease the TR highest temperature by 71.8 °C, and extend the time from self-generated heat to triggering TR by ≈8 h. In addition, the cell with nonflammable LHCE presents superior high voltage cycle stability, attributed to the formation of robust inorganic-rich electrode-electrolyte interphase. The strategy represents a pivotal step forward for practical high energy and high safety batteries.

Thermal-Switchable, Trifunctional Ceramic-Hydrogel Nanocomposites Enable Full-Lifecycle Security in Practical Battery Systems.

Thermal runaway (TR) failures of large-format lithium-ion battery systems related to fires and explosions have become a growing concern. Here, we design a smart ceramic-hydrogel nanocomposite that provides integrated thermal management, cooling, and fire insulation functionalities and enables full-lifecycle security. The glass-ceramic nanobelt sponges exhibit high mechanical flexibility with 80% reversible compressibility and high fatigue resistance, which can firmly couple with the polymer-nanoparticle hydrogels and form thermal-switchable nanocomposites. In the operating mode, the high enthalpy of the nanocomposites enables efficient thermal management, thereby preventing local temperature spikes and overheating under extremely fast charging conditions. In the case of mechanical or thermal abuse, the stored water can be immediately released, leaving behind a highly flexible ceramic matrix with low thermal conductivity (42 mW m-1 K-1 at 200 °C) and high-temperature resistance (up to 1300 °C), thus effectively cooling the TR battery and alleviating the devastating TR propagation. The versatility, self-adaptivity, environmental friendliness, and manufacturing scalability make this material highly attractive for practical safety assurance applications.

High stability and high performance nitrogen doped carbon containers for lithium-ion batteries.

For a long time, carbon has been an ideal material for various electrochemical energy storage devices and a key component in electrochemical energy storage systems due to its advantages of rich surface states, easy tenability, and good chemical stability. Stable and high-performance carbon materials can support future applications of high specific energy electrodes. Herein and for the first time, we have designed nitrogen-doped carbon hollow containers using oleylamine-coating TiO2 mesocrystals as a precursor with a high specific surface area of 1231 m2 g-1. When applied as an anode for lithium-ion storage, a reversible capacity of 774.5 mA h g-1 is obtained at a rate of 0.5 A g-1 after 200 cycles. Meanwhile, at an even higher rate of 2 A g-1, a capacity of 721.1 mA h g-1 is still achieved after 500 cycles. Moreover, the carbon containers remain structurally intact after a series of cycles. This may be attributed to the nitrogen atoms doped on the carbon surface that can absorb multiple lithium ions and enhance the structural stability. These results provide technical support for the development of high specific energy electrode materials.

Synergistic Dual-Salt Electrolyte for Safe and High-Voltage LiNi0.8Co0.1Mn0.1O2//Graphite Pouch Cells.

Concerns about thermal safety and unresolved high-voltage stability have impeded the commercialization of high-energy lithium-ion batteries bearing LiNi0.8Co0.1Mn0.1O2 (NCM811) cathodes. Enhancing the cathode structure and optimizing the electrolyte formula have demonstrated significant potential in improving the high-voltage properties of batteries while simultaneously minimizing thermal hazards. The current study reports the development of a high-voltage lithium-ion battery that is both safe and reliable, using single-crystal NCM811 and a dual-salt electrolyte (DSE). After 200 cycles at high voltage (up to 4.5 V), the capacity retention of the battery with DSE was 98.80%, while that for the battery with a traditional electrolyte was merely 86.14%. Additionally, in comparison to the traditional electrolyte, the DSE could raise the tipping temperature of a battery's thermal runaway (TR) by 31.1 °C and lower the maximum failure temperature by 76.1 °C. Moreover, the DSE could effectively reduce the battery's TR heat release rate (by 23.08%) as well as eliminate concerns relating to fire hazards (no fire during TR). Based on material characterization, the LiDFOB and LiBF4 salts were found to facilitate the in situ formation of an F- and B-rich cathode-electrolyte interphase, which aids in inhibiting oxygen and interfacial side reactions, thereby reducing the intensity of redox reactions within the battery. Therefore, the findings indicate that DSE is promising as a safe and high-voltage lithium-ion battery material.

Drive circuitry of an electric vehicle enabling rapid heating of the battery pack at low temperatures.

Heating battery at low temperatures is fundamental to avoiding the range anxiety and the time-consuming charging associated with electric vehicles (EVs). One method for achieving fast and uniform battery heating is to polarize the cell under pulse currents. However, the on-board implementation of this method leads to an increase in the cost and size. Therefore, in this study, an adapted EV circuitry compatible with the existing one and an optimized operating condition are proposed to enable rapid battery heating. With this circuit, electricity transfer between the cells can be realized through a motor, leading to remarkably higher battery currents than those of the conventional circuit. The increase in the maximum heating currents (from 1.41C to 4C) resulted in a battery temperature rise of 8.6°C/min at low temperatures. This heating method exhibits low cost, high efficiency, and negligible effects on battery degradation, practical and promising on battery heating of EVs.

Thermal runaway of Lithium-ion batteries employing LiN(SO2F)2-based concentrated electrolytes.

Concentrated electrolytes usually demonstrate good electrochemical performance and thermal stability, and are also supposed to be promising when it comes to improving the safety of lithium-ion batteries due to their low flammability. Here, we show that LiN(SO2F)2-based concentrated electrolytes are incapable of solving the safety issues of lithium-ion batteries. To illustrate, a mechanism based on battery material and characterizations reveals that the tremendous heat in lithium-ion batteries is released due to the reaction between the lithiated graphite and LiN(SO2F)2 triggered thermal runaway of batteries, even if the concentrated electrolyte is non-flammable or low-flammable. Generally, the flammability of an electrolyte represents its behaviors when oxidized by oxygen, while it is the electrolyte reduction that triggers the chain of exothermic reactions in a battery. Thus, this study lights the way to a deeper understanding of the thermal runaway mechanism in batteries as well as the design philosophy of electrolytes for safer lithium-ion batteries.

A comparative analysis on thermal runaway behavior of Li (NixCoyMnz) O2 battery with different nickel contents at cell and module level.

The problem of thermal runaway (TR) propagation challenges the safety design of battery packs, because it aggravates the thermal hazards to accidents. There are many unsolved scientific questions in understanding the mechanisms of TR and its propagation behavior for large format lithium-ion batteries (LIBs). LiNixCoyMnzO2(NCM) is considered as one of the most promising cathode materials for lithium-ion batteries LIBs, given its higher energy design and lower cost. However, higher Nickel (Ni) content of cathode material worsens the thermal stability of LIBs. This paper provides a comparative analysis on the TR propagation behavior of NCM battery with different Ni ratios. Results have shown that when the characteristic temperatures of TR {T1, T2, T3}and the specific electrochemical energy of the cell are similar, TR propagation behavior will be similar, no matter what kinds of chemistry the cell has. Observation suggests that the average propagation time within a large format cell is 7-10 s in module tests. Besides, the internal temperature of the cell has an order of NCM622 ≥ NCM523 ≥ NCM111,whereas the mass is ordered by NCM622 > NCM523 > NCM111.This work firstly reports the TR feature in large format LIBs with different Ni ratios, both at cell and module level, providing the guidelines for engineering practice and further theoretical researches.

Thermal Runaway Triggered by Plated Lithium on the Anode after Fast Charging.

Battery safety, at the foundation of fast charging, is critical to the application of lithium-ion batteries, especially for high energy density cells applied in electric vehicles. In this paper, an earlier thermal runaway of cells after fast charging application is illustrated. Under this condition, the reaction between the plated lithium and electrolyte is revealed to be the mechanism of thermal runaway triggering. The mechanism is proved by the accelerated rate calorimetry tests for partial cells, which determine the triggering reactions of thermal runaway in the anode-electrolyte thermodynamic system. The reactants in this system are analyzed by nuclear magnetic resonance and differential scanning calorimetry, proving that the vigorous exothermic reaction is induced by the interaction between the plated lithium and electrolyte. As a result, the finding of thermal runaway triggered by the plated lithium on anode surface of cells after fast charging promotes the understanding of thermal runaway mechanisms, which warns of the danger of plated lithium in the utilization of lithium-ion batteries.

Mechanism of the entire overdischarge process and overdischarge-induced internal short circuit in lithium-ion batteries.

Lithium-ion batteries connected in series are prone to be overdischarged. Overdischarge results in various side effects, such as capacity degradation and internal short circuit (ISCr). However, most of previous research on the overdischarge of a cell was terminated when the cell voltage dropped to 0 V, leaving the further impacts of overdischarge unclear. This paper investigates the entire overdischarge process of large-format lithium-ion batteries by discharging the cell to -100% state of charge (SOC). A significant voltage platform is observed at approximately -12% SOC, and ISCr is detected after the cell is overdischarged when passing the platform. The scanning electron microscopy (SEM) and X-ray diffraction (XRD) results indicate that the overdischarge-induced ISCr is caused by Cu deposition on electrodes, suggesting possible Cu collector dissolution at the voltage platform near -12% SOC. A prognostic/mechanistic model considering ISCr is used to evaluate the resistance of ISCr (RISCr), the value of which decreases sharply at the beginning of ISCr formation. Inducing the ISCr by overdischarge is effective and well controlled without any mechanical deformation or the use of a foreign substance.