Safety Performance Of Lithium-ion Batteries Research Articles

Characterization of Breakdown Arcs Induced by Venting Particles Generated by Thermal Runaway of Large-Capacity Ternary Lithium-Ion Batteries

In recent years, with the continuous growth in power demand, lithium-ion batteries (LIBs) have become an indispensable component of various electronic devices, transportation vehicles, and energy systems. The safety performance of LIBs is one of the most significant issues facing their continued development. In battery systems, the presence of arcs constitutes a significant safety hazard that necessitates attention; the thermal runaway (TR) of LIBs releases a large quantity of particles with elevated temperature and high velocity, probably resulting in arc failures. Changes in the insulation structure inside battery packs and the accumulation of particulate matter resulting from the TR of battery cells are potential causes of arc-induced disasters. In this study, we utilized fully charged 71 Ah ternary LIB Li (Ni0.8Co0.1Mn0.1) O2 (NCM811) pouch cell samples and collected the vented particles in an inert atmosphere after TR. All the settled particles were classified into six groups; by conducting experiments with different particle sizes, electrode spacings, and circuit loads, the patterns of the particle-induced arcs were understood. The results indicate that as the particle size increases, the critical breakdown voltage decreases. Regarding electrode spacing and circuit load resistance, larger values require higher critical breakdown voltages. The research results provide valuable guidance for the electrical protection and safety design of battery systems.

Research on thermal runaway characteristics and mechanism of NCM811 Lithium-ion batteries under cross-seasonal and wide-temperature condition at −10 °C ∼ 33 °C: A case study in Qingdao, China

Multiple heat sources and extreme ambient temperatures pose more severe challenges to the safety performance of lithium-ion batteries (LIBs), and the kinetic characterization of thermal runaway (TR) of LIBs at extreme temperatures has yet to be improved. Through the establishment of a dual heat source coupled stimulation experimental platform, this study investigates the TR mechanism and flame jet dynamics of LIBs under broad temperature ranges corresponding to spring, summer, autumn, and winter (−10 °C ∼ 30 °C). The results indicate that the increase in ambient temperature leads to a gradual reduction in the TR onset time (tonset), in the order of Tonset-Winter>Tonset-Spring>Tonset-Autumn>Tonset-Summer; for example, with 100% SOC (State of Charge), Tonset-Winter = 2528 s, Tonset-Summer = 2211 s, which was accelerated by 14.3%. However, TR maximum temperature (Tmax) showed the opposite trend, Tmax-summer = 687.2 °C, Tmax-winter = 796.5 °C, which decreased by 15.9%. When SOC ≥ 75%, the average warning time for TR disaster of LIB (from venting to the beginning of TR) is 254 s less than that of winter in the summer with higher temperature, which makes the adoption of emergency measures and escape more urgent. When SOC ≥ 50%, the TR process was accompanied by flame generation, and the flame eruption process was the most intense at 100% SOC, with a maximum flame area of about 4400 cm2, and its flame temperature was likewise the highest at 986.4 °C. Carbon and metal oxides were detected in the TR ejecta, and the lower the ambient temperature, the finer the ejecta particles were. The results of the study provide an important scientific reference for improving the theory of TR of LIBs, guiding the investigation of TR and fire in new energy vehicles, and formulating relevant standards.

Influence of ambient temperature on multidimensional signal dynamics and safety performance in lithium-ion batteries during overcharging process

Ambient temperature significantly influences the safety performance of lithium-ion batteries (LIBs), particularly their thermal runaway (TR) behaviors. Yet, the complexities of multidimensional signal dynamics in overcharged LIBs under different ambient temperatures are not well understood. In this study, we performed comprehensive overcharging abuse tests under cold (-10 °C and 0 °C), normal (20 °C), and high ambient temperatures (60 °C), to investigate the evolution of multidimensional signals of expansion force, gas concentration, surface temperature, and voltage. Results show that TR events are not triggered at ambient temperatures of −10 °C and 0 °C, with the maximum temperatures and corresponding rise rate reaching only 125 °C and 0.5 °C/s, respectively. In contrast, for batteries undergoing TR, the maximum temperatures and rates of temperature increase peaked at 410.3 °C and 20.6 °C/s, respectively. The ambient temperature has a minimal impact on the venting force of the battery, which varies from approximately 9500 N to 10000 N, primarily driven by an increase in internal gas pressure during overcharging—a factor relatively unaffected by temperature changes. After safety valve activation during overcharging, Hydrogen (H2) is consistently the first gas detected immediately across all ambient temperature scenarios. Additionally, an increase in ambient temperature results in earlier detection of abnormal expansion and venting behaviors, characterized by lower venting voltages and higher venting temperatures. This study contributes to a deeper understanding of battery failure mechanisms under various ambient temperatures and informs the development of early safety warning strategies for LIBs during the charging process.

Multi-innovation and strong tracking based H[formula omitted] filter for state of charge estimation of lithium-ion batteries

Accurate state of charge (SOC) is a crucial indicator of the battery management system, which ensures the safety performance of lithium-ion batteries (LiBs). However, traditional SOC estimation methods such as extended Kalman filter and H∞ filter (HIF) do not perform satisfactorily when dealing with sudden state changes, which pose a safety hazard to the normal operation of LiBs. This paper proposes two effective strategies to endow the HIF with the strong tracking capability to react to state mutations. Initially, the single innovation in the HIF is extended to the multi-innovation so that the estimation accuracy is ameliorated by incorporating the historical data. Additionally, a suboptimal fading factor is introduced into the HIF to adjust the gain matrix online by forcing the innovation sequence to keep orthogonal. The fading factor fully utilizes the rich information in the innovation sequence, enabling the filter to track changing states well. Finally, the discharge experiments and dynamic stress tests are conducted to verify that the proposed strategy can ameliorate the precision and robustness without bringing extra computational burden.

A Novel Leak-Proof Thermal Conduction Slot Battery Thermal Management System Coupled with Phase Change Materials and Liquid-Cooling Strategies

Electric vehicles (EVs) are experiencing explosive developments due to their advantages in energy conservation and environmental protection. As a pivotal component of EVs, the safety performance of lithium-ion batteries directly affects driving miles and even safety; hence, a battery thermal management system (BTMS) is especially important. To improve the thermal safety performance of power battery modules, first, a new leak-proof phase change material (PCM)-coupled liquid-cooled composite BTMS for large-scale battery modules is proposed in this research. Second, the numerical simulation analysis method was utilized to analyze the influences of the fluid flow channel shape, working fluid inlet temperature, inlet velocity, and reverse flow conditions on the BTMS. Eventually, the abovementioned performances were compared with the traditional PCM-coupled liquid-cooling strategy. The relative data indicated that the Tmax was reduced by 17.5% and the ΔTmax was decreased by 19.5% compared to the liquid-cooling approach. Further, compared with conventionally designed PCM composite liquid cooling, the ΔTmax was reduced by 34.9%. The corresponding data showed that, when using the e-type flow channel, reverse flow II, the inlet flow velocity was 0.001–0.005 m/s, and the inlet temperature was the ambient temperature of the working condition. The thermal performance of the anti-leakage system with a thermal conduction slot PCM-coupled liquid-cooling composite BTMS reached optimal thermal performance. The outcome proved the superiority of the proposed BTMS regarding temperature control and temperature equalization capabilities. It also further reduced the demand for liquid-cooling components, avoided the problem of the easy leakage of the PCM, and decreased energy consumption.

Lithium-ion battery thermal safety evolution during high-temperature nonlinear aging

The thermal safety performance of lithium-ion batteries is significantly affected by high-temperature conditions. This work deeply investigates the evolution and degradation mechanism of thermal safety for lithium-ion batteries during the nonlinear aging process at high temperature. Through a comprehensive analysis from multiple perspectives, it has been revealed that lithium plating and R-H+ reduction are the primary factors contributing to the notable deterioration for battery safety performance during high-temperature aging. Side reactions, such as lithium plating and R-H+ reduction, occurring with aging, not only result in the thickening of the interfacial film but also generate a significant amount of reductive gas. Consequently, these results in a significant increase in cell impedance and a notable decrease in cell thermal stability. These findings offer valuable insights for the development and optimization of safer cell designs.

SIS-Based Electrostatic Spinning High-Safety Lithium-Ion Battery Separators.

As an important component, the properties of separators directly affect the capacity, life, and safety performance of lithium-ion batteries (LIBs). The high thermal stability and safety application value of the thermoplastic elastomer poly(styrene-b-isoprene-b-styrene) block copolymer (SIS) with different block ratios were explored to enhance the thermal stability and mechanical strength of the cross-linked polyacrylonitrile (PAN) membranes by vulcanization cross-linking and heat treatment. Among these membranes, the sample named the S/PAN/SIS-4019 separator was confirmed to be a self-closing separator that can cope with the thermal runaway, attributing to the continued fusion of the SIS soft and hard segments in the cross-linked structure under high-temperature heat treatment. Moreover, the tensile strength of S/PAN/SIS-4019 separator increased to 17.49 MPa, which was better than that of Celgard 2400, PAN, and other inlay separators. Using S/PAN/SIS-4019 as a battery separator, lithium-ion batteries showed a superior electrochemical performance compared to the usage of Celgard 2400. Owing to the stable pore structure and thermally protected self-shutdown mechanism, the overall properties of the obtained cross-linked separator were improved in terms of higher thermal stability, high ionic conductivity, and electrochemical properties.

Organic phase change composite separators to enhance the safety performance of lithium-ion batteries

Lithium-ion batteries have received a great deal of attention on the world stage due to their high-power density and superior electronic properties. Herein, a novel phase change composite separator was successfully fabricated into lithium-ion battery cells by microfluidic technology. The phase change material composite separator was manufactured with polyethylene (PE) as the base film and employing the crystalline phase change property of polyethylene oxide (PEO). The phase change solution was atomized and delivered to the surface of the separator using high-pressure inert gases, and then crystallized on the separator substrate by controlling the temperature difference. The capacity retention and capacity recovery of the manufactured phase change material composite separator cells were 96.9% and 97.8%, respectively. In addition, the cells demonstrated superior multiplier performance (∼98% capacity retention at 1C). Additionally, the phase change material was introduced into the separator coating layer to increase the heat resistance of the separator, while the electrochemical performance was exceptional and the safety performance was favorable, thus alleviating the heat accumulation inside the battery at the source and effectively enhancing the safety of lithium-ion batteries.

Safety Performance and Failure Criteria of Lithium-Ion Batteries under Mechanical Abuse

With the increasing global focus on environmental issues, controlling carbon dioxide emissions has become an important global agenda. In this context, the development of new energy vehicles, such as electric vehicles, is flourishing. However, as a crucial power source for electric vehicles, the safety performance of lithium-ion batteries under mechanical abuse has drawn widespread attention. Evaluating the safety performance of lithium-ion batteries requires in-depth research. This paper provides a review of recent experimental and numerical simulation studies on the mechanical abuse of lithium-ion batteries. It showcases the main methods and conclusions of experimental research, compares different response forms under quasi-static and dynamic loading, discusses the causes of strain-rate dependence in lithium-ion batteries, and briefly describes the impact of the state of charge (SOC) on safety performance under mechanical abuse, as well as the influence of mechanical abuse on battery capacity and impedance characteristics. Furthermore, this paper summarizes the methods of numerical simulation research, analyzes the advantages and disadvantages of detailed modeling and homogenized modeling methods, summarizes the strain-based internal short circuit failure criteria, and reviews numerical predictive models based on multiphysics coupling. Finally, it presents the latest progress in studying the safety performance of battery packs through numerical simulations.

Thermal performance of cold plate based on phase change emulsion for Li-ion battery

A battery thermal management system (BTMS) is responsible for the safety performance of lithium-ion batteries. In this paper, different cooling methods based on phase change emulsion (PCE) containing 10 wt% to 40 wt% paraffin were investigated and compared with a water-cooling system. The three-dimensional thermal simulation results showed that the cooling performance of the mini-channel configuration was better than the baffle plate, fin cooling and jacket cooling methods. Based on the optimized structure of the mini-channel cold plate, the operation conditions for cooling Li-ion batteries were determined to keep the maximum temperature limit of 313 K and maximum temperature difference of 5 K at various discharge rates. There was advantage for the PCE cooling in reducing the pump energy consumption for high discharging rates compared with water cooling. The pump power declined by 24% and 36% for 2.0C discharging when applying the PCE with 25 wt% and 40 wt% paraffin as the coolant, respectively. The cooling with the PCE containing 25 wt% paraffin had 16% less energy consumption for 3.0C discharging.

Evaluation of composite flame-retardant electrolyte additives improvement on the safety performance of lithium-ion batteries

Safety requirements for lithium-ion batteries (LIBs) have become increasingly stringent with the rapid development of LIBs. We synthesize composite flame-retardant electrolyte additives (pentafluoroethoxy cyclotriphosphazene and dimethylacetamide) for LIBs to improve the safety performance of LIBs during use. The study tests the electrochemical performance of LIBs whose electrolytes contain the aforementioned additives using an electrochemical workstation and a LIB parameter tester. An experiment on self-extinguishing time is conducted to test the flame retardancy and ionic conductivity of the prepared composite flame-retardant electrolytes. Differential scanning calorimetry (DSC) and thermogravimetry are conducted to test the cathode materials of the LIBs after cycling at different heating rates. Various nonisothermal thermodynamic models are used to analyze the experimental DSC data, and the cathode materials’ apparent activation energy and thermodynamic parameters are obtained. Finally, multivariate linear fitting is conducted to simulate the thermal decomposition reaction of the cathode materials.

Temperature-Shift-Induced Mechanical Property Evolution of Lithium-Ion Battery Separator Using Cyclic Nanoindentation.

The evolution of mechanical properties of separators affected by temperature shifts is imperative for the performance of the lithium-ion battery. The flexible film characteristics hinder the evaluation of the micromechanical properties of separators. In the present study, considering the susceptibility of separators to temperature fluctuations, the temperature distribution of the battery during the discharging process at subzero temperature is obtained. Three sets of separator samples subjected to various temperature shifts are prepared. Through multicycle depth-sensitive nanoindentation, the temperature-dependent weakening of elastic modulus and hardness of separators is experimentally verified. Moreover, the variation trends of elastic modulus, hardness, and hysteresis response of the separator specimens in terms of temperature are investigated via extracting from the multicycle loading-unloading nanoindentation responses. The temperature-dependent variations in the elastic modulus of the separator were investigated by following heating, cooling, and thermostatic processes. Meanwhile, the indentation tests also verify that the effect of temperature shifts on the hardness exhibits an attenuation trend when heating or cooling is followed by a thermostatic process. The variation analysis of nanoindentation hardness as a function of temperature shifts shows typical size effects dependent on the nanoindentation depth. The temperature-induced residual stress and elemental distribution are also analyzed through characterization using X-ray diffraction and energy-dispersive X-ray spectroscopy, respectively. The obtained evolution law of temperature shift-induced mechanical properties of a separator could facilitate the optimal design of the separators and provide the supporting data to enhance the safety performance of lithium-ion batteries.

The influence of overcharge and discharge rate on the thermal safety performance of lithium-ion battery under low air pressure

The influence of overcharge and discharge rate on the thermal safety performance of lithium-ion battery under low air pressure

Mechanical-electrical-thermal responses of lithium-ion pouch cells under dynamic loading: A comparative study between fresh cells and aged ones

Mechanical integrity is one of the study focuses of lithium-ion batteries, which is greatly influenced by the loading rate and the cycling ageing level. This paper investigates how dynamic loading and low-temperature ageing collectively affect the safety performance of lithium-ion batteries under indentation loadings, by monitoring and comparing the in-situ mechanical-electrical-thermal responses. For the mechanical response, results show that dynamic loading increases the battery stiffness while low-temperature ageing alleviates that. During the intrusion process, the electrical response is mostly influenced by the loading rate. Fast voltage dropping and recovering occur under dynamic loading scenarios, leaving a downward trench in the voltage profile. The higher the loading rate, the earlier the short circuit and the faster the voltage dropping. After the termination of the loading, the voltage dropping is mostly affected by the ageing level. Low-temperature ageing accelerates the long-term voltage dropping rate. As for the thermal response, it is highly related to the short circuit behavior. Upward temperature peaks are formed right after the short circuit under dynamic loadings, corresponding to the voltage trenches. Besides, aged cells have higher long-term temperature profiles, corresponding to the accelerated long-term voltage dropping rates.

Electrolyte Additives for Improving the High-Temperature Storage Performance of Li-Ion Battery NCM523∥Graphite with Overcharge Protection.

The overcharge safety performance of lithium-ion batteries has been the major bottleneck in the widespread deployment of this promising technology. Pushing the limitations further may jeopardize cell safety when it is performed at high-temperature storage. On the basis of the lacking systematic research on overcharge protection electrolyte additives with high-temperature storage capacity, we explore the promotion effect of overcharge additives on electrolyte decomposition at 60 °C. Specifically, the addition of tris(trimethylsily) phosphite (TMSP) and lithium difluoro(oxalato)borate (LiDFOB) in the electrolyte can not only form the robust cathode electrolyte interface/solid electrolyte interphase (CEI/SEI) but also improve the thermal stability of the electrolyte. Therefore, we promote the electrolyte system to realize the 18,650 LIB storage at 60 °C for 50 days by optimizing the formula in the electrolyte containing biphenyl (BP) and cyclohexylbenzene (CHB) overcharge protection additives, and the capacity retention rate can reach more than 90% with overcharge safety. Further, the optimized electrolyte system has also been implemented to commercial 18,650 LIBs and demonstrates the widening of the route to the widespread application of the electrolyte under extreme conditions.

Deformation and Failure Properties of High-Ni Lithium-Ion Battery under Axial Loads.

To explore the failure modes of high-Ni batteries under different axial loads, quasi-static compression and dynamic impact tests were carried out. The characteristics of voltage, load, and temperature of a battery cell with different states of charge (SOCs) were investigated in quasi-static tests. The mechanical response and safety performance of lithium-ion batteries subjected to axial shock wave impact load were also investigated by using a split Hopkinson pressure bar (SHPB) system. Different failure modes of the battery were identified. Under quasi-static axial compression, the intensity of thermal runaway becomes more severe with the increase in SOC and loading speed, and the time for lithium-ion batteries to reach complete failure decreases with the increase in SOC. In comparison, under dynamic SHPB experiments, an internal short circuit occurred after impact, but no violent thermal runaway was observed.

Comprehensive Insight into the Probability of Cyclotriphosphazene Derivatives as the Functional Electrolyte Additives in Lithium-Ion Batteries: Which Is Better and Why?

Enhancing the flame retardancy of electrolytes and the quality of interface films is of great significance to improve the safety performance of lithium-ion batteries (LIBs). In this work, the effects of (ethoxy)pentafluorocyclotriphosphazene (PFPN), hexafluorocyclotriphosphazene (FPPN), and pentafluoro(phenoxy)cyclotriphosphazene (HFPN) as flame-retardant additives in the functional electrolyte on the performances of LiNi0.6Mn0.2Co0.2O2 (NCM622)/graphite pouch cells are comprehensively investigated. It is indicated that the contents of PFPN, FPPN, and HFPN, respectively, reach 5, 8, and 8% to achieve the purpose of flame retardancy in the 1 M LiPF6/EC + EMC (EC/EMC = 1:2 in weight) system. When the cells without and with PFPN, FPPN, and HFPN additives are, respectively, charge–discharged in the voltage range of 3.0–4.4 V at 1C, their capacity retentions are 36.1, 60.7, 74.7, and 73.8% after 150 cycles. The interface analysis and theoretical calculation show that PFPN, FPPN, and HFPN can facilitate the formation of stable interface films on two electrodes and subsequently improve the battery performance. The addition of cyclotriphosphazene flame retardant in the electrolyte ultimately improves the safety of NCM622/graphite pouch cells without sacrificing electrochemical performance. The as-prepared additive-containing electrolyte exhibits promising prospects in the application, and the evaluation method is also useful to develop the functional electrolyte with flame retardant and film-forming properties.

Effect of low-temperature aging on the safety performance of lithium-ion pouch cells under mechanical abuse condition: A comprehensive experimental investigation

Understanding how aging affects the safety performance of lithium-ion batteries under mechanical abuse is of great importance. In this study, pouch cell batteries with four different aging levels (0%, 10%, 20% and 30% capacity fading), which respectively represent fresh, prior-scrapped, normally scrapped and over-scrapped batteries, are prepared at 0 °C and subjected to indentation loading. Mechanical-electrical-thermal responses of these batteries are compared. Results show that aged pouch cells have right-shifted force-displacement curves, higher inflection force and higher peak force. After short circuit, voltage dropping is faster and electric energy is released in a shorter duration for aged ones, leading to a higher temperature for the whole battery cell. For cells with 30% capacity fading, the voltage dropping and temperature increasing are in a steep behavior. And the generated heat after short circuit is concentrated in the indented area, resulting a localized peak temperature of 117∘C. To clarify the observations, mechanical tests in the component level are carried out. Results reveal that the response changes in cell tests are mainly from the anode. Compression test of aged anode electrode shows consistent mechanical response changes with cell test. The delay of anode fracture under compression loading lead to the enlargement of the shear fracture zone, together with the formation of sharp lithium dendrite, resulting in more severe short circuit.

Oriented PAN/PVDF/PAN laminated nanofiber separator for lithium-ion batteries

Electrospun nanofiber separators have excellent properties in terms of large surface area and high porosity, which benefits the rate capability, electrochemical stability, and safety performance of lithium-ion batteries. Herein, a 0°PAN/PVDF/90°PAN-oriented composite nanofiber separator is prepared, which is prepared layer by layer by electrospinning technology and drum orientation collector. The results show that when the rotating speed of the drum is 600 r min−1, the 0°PAN/PVDF/90°PAN-oriented composite nanofiber separator has high porosity (about 85%), improved transverse and longitudinal tensile properties (10.33 MPa and 11.03 MPa, respectively), good dimensional stability at 160°C, and good electrochemical performance (specific charge capacity of 165 mAh g−1 at 0.5C and 142.7 mAh g−1 at 1C, capacity retention of 90% after 100 cycles).

Influence of Bi2O3 additive on the electrochemical performance of Na3.1Y0.1Zr1.9Si2PO12 inorganic solid electrolyte

Owing to the flammability of dendrites and organic liquid electrolytes, the safety performance of lithium-ion batteries cannot be effectively ensured. The sodium-ion solid electrolyte is anticipated to become the leading next generation battery in commercial applications due to the high thermal stability and low price. Yet, the insufficient ionic conductivity of Na3Zr2Si2PO12 solid electrolytes, along with the large interfacial resistance between the cathode material and the solid electrolyte, substantially restricts the performance of room-temperature all-solid-state sodium rechargeable batteries. In the present study, the effects of Bi2O3 additive on the phase, microstructure and ionic conductivity of Na3.1Y0.1Zr1.9Si2PO12 ceramic electrolyte are reported. Moreover, a significant room temperature conductivity of 1.21 × 10-3 S cm-1 and the dense microstructure was attained by adding 1 wt% Bi2O3 to Na3.1Y0.1Zr1.9Si2PO12 sintered at 1100 °C for 6 h. Simultaneously, an electrochemical test exhibited that the electrochemical stability window increased to 4.8 V and revealed good cycle stability.