Safety and Quality Issues of Counterfeit Lithium-Ion Cells.

Lithium-ion batteries continue to transform consumer electronics, mobility, and energy storage sectors, and the applications and demands for batteries keep growing. Supply limitations and costs may lead to counterfeit cells in the supply chain that could affect quality, safety, and reliability of batteries. Our research included studies of counterfeit and low-quality lithium-ion cells, and our observations on the differences between these and original ones, as well as the significant safety implications, are discussed. The counterfeit cells did not include internal protective devices such as the positive temperature coefficient or current interrupt devices that typically offer protection against external short circuits and overcharge conditions, respectively, in cells from original manufacturers. Poor-quality materials and lack of engineering knowledge were also evident on analyses of the electrodes and separators from low-quality manufacturers. When the low-quality cells were subjected to off-nominal conditions, they experienced high temperature, electrolyte leakage, thermal runaway, and fire. In contrast, the authentic lithium-ion cells performed as expected. Recommendations are provided to identify and avoid counterfeit and low-quality lithium-ion cells and batteries.

In Situ Gas Analysis and Fire Characterization of Lithium-Ion Cells During Thermal Runaway Using an Environmental Chamber.

An experimental apparatus and a standard operating procedure (SOP) are developed to collect time-resolved data on the gas compositions and fire characteristics during and post-thermal runaway of lithium-ion battery (LIB) cells. A 18650 cylindrical cell is conditioned to a desired state-of-charge (SOC; 30%, 50%, 75%, and 100%) before each experiment. The conditioned cell is forced into a thermal runaway by an electrical heating tape at a constant heating rate (10 °C/min) in an environmental chamber (volume: ~600 L). The chamber is connected to a Fourier transform infrared (FTIR) gas analyzer for real-time concentration measurements. Two camcorders are used to record major events, such as cell venting, thermal runaway, and the subsequent burning process. The conditions of the cell, such as surface temperature, mass loss, and voltage, are also recorded. With the data obtained, cell pseudo-properties, venting gas compositions, and venting mass rate can be deduced as functions of cell temperature and cell SOC. While the test procedure is developed for a single cylindrical cell, it can be readily extended to test different cell formats and study fire propagation between multiple cells. The collected experimental data can also be used for the development of numerical models for LIB fires.

Elucidating Lithium Alloying-Induced Degradation Evolution in High-Capacity Electrodes.

Alloy electrode materials offer high capacity in lithium-ion batteries; however, they exhibit rapid degradation resulting in particle disintegration and electrochemical performance decay. In this study, the evolution of lithium alloying-induced degradation due to electrochemomechanical interactions is examined based on a multipronged electrochemical and microstructural analysis. Copper-tin (Cu6Sn5) is chosen as an exemplary alloy electrode material. Electrodes with compositional variations were fabricated, and electrochemical performance was examined under varying conditions including voltage window, C-rate, and short- and long-term cycling. Morphology and composition analyses of pristine and cycled electrodes were conducted using micrography and spectroscopy techniques. Alloying-induced electrode microstructural evolution was probed using X-ray microtomography. The rapid capacity fading was found to be caused by mechanical degradation of the electrode. Driving the electrode to a lower potential ( E ≈ 0.2 V vs Li/Li+) induced Li-Sn alloy formation and provided the characteristic large capacity; however, this led to a large volume expansion and active particle cracking and disintegration. Copper expulsion was found to be a consequence of the alloy formation; however, it was not the primary contributor to the dramatic electrochemical performance decay.

Three-electrode Coin Cell Preparation and Electrodeposition Analytics for Lithium-ion Batteries.

As lithium-ion batteries find use in high energy and power applications, such as in electric and hybrid-electric vehicles, monitoring the degradation and subsequent safety issues becomes increasingly important. In a Li-ion cell setup, the voltage measurement across the positive and negative terminals inherently includes the effect of the cathode and anode which are coupled and sum to the total cell performance. Accordingly, the ability to monitor the degradation aspects associated with a specific electrode is extremely difficult because the electrodes are fundamentally coupled. A three-electrode setup can overcome this problem. By introducing a third (reference) electrode, the influence of each electrode can be decoupled, and the electrochemical properties can be measured independently. The reference electrode (RE) must have a stable potential that can then be calibrated against a known reference, for example, lithium metal. The three-electrode cell can be used to run electrochemical tests such as cycling, cyclic voltammetry, and electrochemical impedance spectroscopy (EIS). Three-electrode cell EIS measurements can elucidate the contribution of individual electrode impedance to the full cell. In addition, monitoring the anode potential allows the detection of electrodeposition due to lithium plating, which can cause safety concerns. This is especially important for the fast charging of Li-ion batteries in electric vehicles. In order to monitor and characterize the safety and degradation aspects of an electrochemical cell, a three-electrode setup can prove invaluable. This paper aims to provide a guide to constructing a three-electrode coin cell setup using the 2032-coin cell architecture, which is easy to produce, reliable, and cost-effective.

Hierarchical Structured Cu/Ni/TiO2 Nanocomposites as Electrodes for Lithium-Ion Batteries.

The electrochemical performance of anodes made of transition metal oxides (TMOs) in lithium-ion batteries (LIBs) often suffers from their chemical and mechanical instability. In this research, a novel electrode with a hierarchical current collector for TMO active materials is successfully fabricated. It consists of porous nickel as current collector on a copper substrate. The copper has vertically aligned microchannels. Anatase titanium dioxide (TiO2) nanoparticles of ∼100 nm are directly synthesized and cast on the porous Ni using a one-step process. Characterization indicates that this electrode exhibits excellent performance in terms of capacity, reliable rate, and long cyclic stability. The maximum insertion coefficient for the reaction product of LixTiO2 is ∼0.85, a desirable value as an anode of LIBs. Cross-sectional SEM and EDS analysis confirmed the uniform and stable distribution of nanosized TiO2 nanoparticles inside the Ni microchannels during cycling. This is due to the synergistic effect of nano-TiO2 and the hierarchical Cu/Ni current collector. The advantages of the Cu/Ni/TiO2 anode include enhanced activity of electrochemical reactions, shortened lithium ion diffusion pathways, ultrahigh specific surface area, effective accommodation of volume changes of TiO2 nanoparticles, and optimized routes for electrons transport.