Chemical-Free Recycling of Cathode Material and Aluminum Foil from Waste Lithium-Ion Batteries by Combining Plasma and Ultrasonic Technology.

With the rapid demand for lithium-ion batteries due to the widespread application of electric vehicles, a significant amount of battery electrode pieces requiring urgent treatment are generated during battery production and disposal. The strong bonding caused by the presence of binders makes it challenging to achieve thorough separation between the cathode active materials and Al foil, posing difficulties in efficient battery material recycling. To address this issue, a plasma-ultrasonically combined physical separation method is proposed in this study. This method utilizes plasma-generated excited-state radicals assisted by ultrasonic waves to separate active materials and current collectors. The results indicate that the binders are effectively decomposed under plasma treatment at 13.56 MHz, 100 W, and 10 min in an oxygen atmosphere, resulting in a separation efficiency of 96.8 wt % for the cathode materials. Characterization results demonstrate that the morphology, crystal structure, and chemical composition of the recycled cathode active materials remain unchanged, facilitating subsequent direct restoration and hydrometallurgical recycling. Simultaneously, the Al foil is also completely recycled for subsequent reuse. Compared with traditional methods of separating cathode active materials and aluminum foil, the method proposed in this study has significant economic and environmental potential. It can promote the recycling of battery materials and the development of sustainable transportation.

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.

Enabling Electrochemical-Mechanical Robustness of Ultra-High Ni Cathode via Self-Supported Primary-Grain-Alignment Strategy.

The electrochemical-mechanical degradation of ultrahigh Ni cathode for lithium-ion batteries is a crucial aspect that limits the cycle life and safety of devices. Herein, the study reports a facile strategy involving rational design of primary grain crystallographic orientation within polycrystalline cathode, which well enhanced its electro-mechanical strength and Li+ transfer kinetics. Ex situ and in situ experiments/simulations including cross-sectional particle electron backscatter diffraction (EBSD), single-particle micro-compression, thermogravimetric analysis combined with mass spectrometry (TGA-MS), and finite element modeling reveal that, the primary-grain-alignment strategy effectively mitigates the particle pulverization, lattice oxygen release thereby enhances battery cycle life and safety. Besides the preexisting doping and coating methodologies to improve the stability of Ni-rich cathode, the primary-grain-alignment strategy, with no foreign elements or heterophase layers, is unprecedently proposed here. The results shed new light on the study of electrochemical-mechanical strain alleviation for electrode materials.

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.

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.

Probing the Thermal-Driven Structural and Chemical Degradation of Ni-Rich Layered Cathodes by Co/Mn Exchange.

The intrinsic poor thermal stability of layered LiNixCoyMn1-x-yO2 (NCM) cathodes and the exothermic side reactions triggered by the associated oxygen release are the main safety threats for their large-scale implantation. In the NCM family, it is widely accepted that Ni is the stability troublemaker, while Mn has long been considered as a structure stabilizer, whereas the role of Co remains elusive. Here, via Co/Mn exchange in a Ni-rich LiNi0.83Co0.11Mn0.06O2 cathode, we demonstrate that the chemical and structural stability of the deep delithiated NCM cathodes are significantly dominated by Co rather than the widely reported Mn. Operando synchrotron X-ray characterization coupling with in situ mass spectrometry reveal that the Co4+ reduces prior to the reduction of Ni4+ and could thus prolong the Ni migration by occupying the tetrahedra sites and, hence, postpone the oxygen release and thermal failure. In contrast, the Mn itself is stable, but barely stabilizes the Ni4+. Our results highlight the importance of evaluating the intrinsic role of compositional tuning on the Ni-rich/Co-free layered oxide cathode materials to guarantee the safe operation of high-energy Li-ion batteries.

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.

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.