Calendar Life Tests Research Articles

Transition Metal Dissolution: Impacts on Cell Performance and Mitigation by Electrolyte Formulation

Layered lithium transition metal oxides with nickel, cobalt, and/or manganese are nearly ubiquitous as cathodes in lithium-ion batteries for high energy density applications. As the cells age through cycling or exposure to high temperatures, degradation mechanisms within the battery can lead to release of transition metals from the cathode lattice. The dissolution of transition metals from the cathode and deposition on the anode have been linked to increased capacity fade and poor coulombic efficiency, attributed to constant degradation of electrolyte at the anode interface and lithium inventory loss.1 Orbia’s Battery Materials Innovation Center (formerly known as Silatronix) specializes in the design, synthesis, formulation, and optimization of electrolyte components for specific applications, as well as electrolyte performance cell testing and cell post-mortem analyses. In this study, we explored modification of the electrolyte composition as a method to reduce transition metal dissolution in Gr/NMC811 multi-layer pouch cells. Battery tests under a variety of aging conditions such as high temperature cycling, low temperature cycling, calendar life, and high-rate tests were studied to understand the conditions that lead to transition metal dissolution, which was quantified by ICP-OES. The relationships between transition metal dissolution and cell performance were investigated, including correlations between capacity fade, cell impedance, voltage hysteresis, and lithium plating. Next, a wide range of electrolyte formulations were tested under the above aging conditions and the effects of electrolyte composition were assessed, including the selection and concentration of solvents, additives, and salts, on transition metal dissolution and performance impacts. Electrolyte components that consistently reduce manganese dissolution and improve cell performance under a wide range of conditions were identified and are discussed in this presentation. These results provide insights into the practical design of electrolytes for reducing transition metal dissolution in a manner that is specifically correlated with performance improvements.

Nondestructive diagnosis technique for LiFePO4/graphite cells based on the internal resistance curve analysis

To explain the degradation mechanism of lithium-ion batteries, a nondestructive diagnosis technology to estimate the degree of degradation of the cell components is required. A technology that satisfies that requirement is widely used to analyze the open-circuit voltage (OCV) curve of a cell and estimate the positive-electrode and negative-electrode capacities and the amount of deactivated lithium. However, it has been difficult to estimate the degradation of electrodes composed of active materials with flat electrode potentials, such as lithium iron phosphate (LFP). The novel nondestructive method developed in this study can estimate the degradation state of battery components using LFP by analyzing the “internal resistance curve” of the battery. This method is used to determine the degradation parameters that explain both the measured OCV curve and the measured internal resistance curves of the cell by comparing the internal resistance curves of the cells with those of the positive and negative electrodes. The results of calendar life tests of lithium-ion batteries using LFP at elevated temperature and high voltage were analyzed by using this method, and the results of the analysis show that the degradation of the LFP positive electrode was progressing.

Solid State Li-Metal Battery Based on Novel Polymer Electrolyte

Conventional Li-ion batteries (LIBs) with unique advantages, exhibit a limited cycle life and significant safety problems due to the flammable organic solvent electrolytes. A solid-state battery (SSB) utilizing a solid electrolyte can potentially address the above issues. However, despite recent advancements, a truly commercially viable candidate for SSB electrolyte remains elusive. Although inorganic lithium-ion conductors are available, their practical applications have been mainly hindered by interfacial issues, since it is very challenging to construct intimate contact between the solid electrode and solid electrolyte due to their rigidity in conventional SSBs, leading to high polarization and low utilization of active materials. Storagenergy Technologies, Inc. has developed a novel polymer electrolyte that exhibits high Li+ conductivity, wide electrochemical window, and wide operational temperature. We also demonstrated a simple but effective interfacial engineering approach to improve the active material utilization via in-situ polymerization process. Complete characterization including cycling life, rate capability, thermal stability, calendar life and safety testing of coin cells and pouch cells with develop polymer electrolyte will be presented.

(Invited) Extend Calendar Life of Si Based Li-Ion Batteries

Although significant progress has been made in increasing the specific energy and cycle life of silicon (Si) based Li-ion batteries (Si-LIBs), calendar life of these batteries is still less than two years, which is far less than the 10 year life-time required for electrical vehicle applications.1 Graphite anodes undergo only ~10% volume change during cycling, so SEI formed during the initial process does not experience significant mechanical stress during the subsequent cycles. However, the SEI layer formed on Si anodes experiences tremendous mechanical stress during repeated cycles. Most SEI layers formed on the Si surface in conventional electrolytes break down, exposing fresh, lithiated Si or SiO to electrolyte. Thus, significant Si corrosion and electrolyte consumption continuously occur during battery storage, especially in the fully lithiated conditions and elevated temperatures required for the accelerated calendar life test.2 As a result, the impedance of the Si anode will increase much faster than a graphite anode and shorten its calendar life, as observed in nearly all Si-LIBs. In this work, we will report the results of our recent investigation on the fundamental mechanism behind the limited calendar life of Si-LIBs. Several approaches that alleviated degradation of SEI layer and increasing cycle life of Si-LIBs will be discussed, including the nanostructured Si designs that can minimize the external size expansion, minimized particle surface area, and formation of stable SEI layers by localized high concentration electrolyte tailored for Si anode. The combination of these methods can largely extend the calendar life of Si-LIBs and accelerate the application of these batteries for large-scale electrical vehicles and consumer electronics applications.

Experimental analysis of commercial LiFePO4 battery life span used in electric vehicle under extremely cold and hot thermal conditions

To widely commercialize electric vehicles more efforts for their life improvement seem extremely inevitable. Thermal conditions can have profound and nonlinear effects on the degradation rate of an electric vehicle battery pack as well as its performance and safety level. In the current study, both cycle life and calendar life of a commercial LiFePO4 cell are investigated experimentally by means of capacity fading and resistance increment evaluation for 4 different thermal conditions from extremely cold condition of − 20 °C—which is not well studied in the literature—till hot condition of 55 °C. The calendar life tests show that the best condition for storing cells is at 5 °C and 50% SOC and the cycle life tests demonstrate that the best operating temperature is 25 °C based on the dynamic stress test discharge/charge profile (a test profile for electric vehicles). It is also found that the capacity fading and resistance increment at a high temperature such as 50 °C are destructively significant. The presented curves in this paper can also serve as an aging data source for further work on battery lifetime modeling and diagnostics. The role of temperature on the degradation level is also discovered via scanning electron microscopy.

Life Prediction of Lithium Ion Battery for Grid Scale Energy Storage System

As renewable energy with large output fluctuation increases, adoption of a large power storage system in which lithium ion secondary batteries are series-parallelized has been started for stabilization of grid power. However, stationary storage systems may be charged and discharged under more severe conditions than batteries for electric vehicles, and may deteriorate in a short period of time. In this research, while analyzing the change of capacity and internal resistance of the lithium ion secondary battery which uses LFP for the cathode and carbon anode. We estimated the life when charging and discharging under the conditions of ancillary service*, and considered the proposed measures for prolonging the life. * ancillary service; A power adjustment method for stabilizing grid transmission Experiment A sample cell using an electrode (57 mm × 40 mm) including LiFePO4 for the positive electrode and carbon for the negative electrode was used. As evaluation methods, temperature and charge / discharge cycle tests with different charge / discharge rates and calendar life tests were conducted to analyze cycle characteristics and time characteristics of capacity and internal resistance. Results and Discussion 2.1 Cell performance The LFP cell produced in this study had an average voltage of 3.05 V (during 1 C discharge), an initial capacity of 1.0 Ah (during 1 C discharge), and a DC resistance of 16 mΩ (SOC 50%). When 1 C charge and discharge were repeated in the initial cell, the temperature rose to 31.1 °C. under natural cooling conditions of 24.9 ° C. outside temperature. 2.2 Degradation characteristics The capacity decrease is highly dependent on SOC, and in the state of 90% of SOC, the capacity decrease was about twice as fast as 50% of SOC. On the other hand, the increase in resistance was highly temperature-dependent, and the capacity decrease was about twice as fast as at 25 ° C. at 45 ° C. conditions. Also, multiple degradation mechanisms exist because at least two or more inflection points exist, not following the 1/2 power of time, which is the degradation tendency of a general lithium ion secondary battery. 2.3 Life prediction of LIB for grid scale energy storage system There are many ways to operate the stationary storage system, but as a power adjustment method to stabilize power transmission of the system, the result of predicting the degradation behavior when the battery is operated under the test condition of ancillary service reported by PJM. It has been found that if the number of cells in parallel is reduced to increase the output power per unit cell, the deterioration is accelerated due to the influence of the temperature rise of the cells. Figure 1

Influence of Li Content on Structure and Electrochemical Performance of Lithium-Rich Cathode Materials for Lithium-Secondary Batteries

Li- and Mn-rich cathode materials win huge attentions due to their extremely high capacity and unique solid solution composite structure. As a composition contains two or more phase, the compatibility of these phases would be critical points to promise high capacity output. We chose both layered structures which have similar oxygen ion arrangement as framework and distinct cations distribution, 1 to found the xLi2MnO3-yLiNi1/3Co1/3Mn1/3O2 cathode materials. From former researches, 2 Li was always used to adjust the ratio of the layered and monoclinic phase. Thus, in this paper the Li content was changed to adjust the composition of the two contained phase. All the precursors of three samples were synthetized though co-precipitation route, after drying and mixing with lithium, the powders were sintered at 900 oC for 15h to obtain the final products. The XRD (X-ray diffraction) were used to investigate the order of crystal structure of these cathode materials, indicating that the ordering of the layered structure was improved with Li content decreased. The intensity of characteristic peaks for monoclinic phase increases with increasing Li content while the ratio of W rohom /W mono decrease from 4.1565 through 3.240 and 3.0789 to 2.44, these results combined with the broaden and split more clearly of (006)/(102) and (108)/(110) doublets indicate the formation of more ordered layered structure as more Li sites were occupied. Electrochemical performance was evaluated by galvanostatic mode at C/10 with cutoff voltage of 4.8V. Results show that the more Li in the structure, the lower polarizing voltage can be obtained, otherwise, the much lower first cycle coulombic efficiency accompanied. Rate capability (not shown) can be improved but with much faster capacity fade and voltage decay. Reference Chen, Y.; Chen, Z.; Xie, K., Effect of Annealing on the First Cycle Performance and Reversible Capabilities of Lithium-Rich Layered Oxide Cathodes. The Journal of Physical Chemistry C 2014.Watanabe, S.; Kinoshita, M.; Nakura, K., Capacity fade of LiNi(1−x−y)CoxAlyO2 cathode for lithium-ion batteries during accelerated calendar and cycle life test. I. Comparison analysis between LiNi(1−x−y)CoxAlyO2 and LiCoO2 cathodes in cylindrical lithium-ion cells during long term storage test. J. Power Sources 2014, 247 (0), 412-422. Figure 1

Temperature Effects on Calendar Aging of Lithium-Ion and Nickel Metal Hydride Batteries

The effect of temperature on the calendar aging of commercially available 3.25 Ah Lithium-Ion (Li-Ion) and 2.30 Ah Nickel Metal Hydride (Ni-MH) batteries were investigated. Calendar life tests were carried out using open circuit method at -20°C, 20°C and 55°C temperatures and initial state of charge (100% SOC). It is found that the aging of the batteries increases with increasing temperature and storage time.

Novel estimation method of operating life in lithium-ion pouch cells

Herein, a novel operating life (OL) test method was evaluated with 200mAh pouch-type lithium-ion batteries. By combining the calendar life (CL) test with intermediate pulse power cycling, more realistic life prediction was possible, which encompassed real operation of batteries accompanying with thermal acceleration. Larger capacity decrease and resistance increase of pouch cell were observed in the OL test, which was well explained using the SEI film growth model. After dissemble of pouch cell, capacity loss and resistance increase mostly occurred within anode, reflecting that SEI film growth on anode surface was highly attributable to cell degradation.

LiNi0.8Co0.2O2-based high power lithium-ion battery positive electrodes analyzed by x-ray photoelectron spectroscopy: 6. Following calendar-life test for 2 weeks at 70 °C, 60% state-of-charge (3.747 V)

X-ray photoelectron spectroscopy(XPS) was used to analyze rinsed and not rinsed LiNi0.8Co0.2O2-based high power lithium-ion battery cathodes following calendar-life testing at 70 °C, 60% state-of-charge. XP spectra were obtained using incident monochromatic AlKα radiation at 0.83401 nm. A survey spectrum together with F 1s, O 1s, C 1s, P 2p, and Li 1s are presented. The spectra indicate the principal core level photoelectron and Auger electron signals.

LiNi0.8Co0.2O2-based high power lithium-ion battery positive electrodes analyzed by x-ray photoelectron spectroscopy: 5. Following calendar-life test for 8 weeks at 60 °C, 60% state-of-charge (3.747 V)

X-ray photoelectron spectroscopy(XPS) was used to analyze rinsed and not rinsed LiNi0.8Co0.2O2-based high power lithium-ion battery cathodes following calendar-life testing at 60 °C, 60% state-of-charge. XP spectra were obtained using incident monochromatic AlKα radiation at 0.83401 nm. A survey spectrum together with F 1s, O 1s, C 1s, P 2p and Li 1s are presented. The spectra indicate the principal core level photoelectron and Auger electron signals.

LiNi0.8Co0.2O2-based high power lithium-ion battery positive electrodes analyzed by x-ray photoelectron spectroscopy: 3. Following calendar-life test for 12 weeks at 40 °C, 60% state-of-charge (3.747 V)

X-ray photoelectron spectroscopy(XPS) was used to analyze rinsed and not rinsed LiNi0.8Co0.2O2-based high power lithium-ion battery cathodes following calendar-life testing at 40 °C, 60% state-of-charge. XP spectra were obtained using incident monochromatic AlKα radiation at 0.83401 nm. A survey spectrum together with F 1s, O 1s, C 1s, P 2p, and Li 1s are presented. The spectra indicate the principal core level photoelectron and Auger electron signals. Both cathodes show only minor nitrogen contamination.

LiNi0.8Co0.2O2-based high power lithium-ion battery positive electrodes analyzed by x-ray photoelectron spectroscopy: 4. Following calendar-life test for 8 weeks at 50 °C, 60% state-of-charge (3.747 V)

X-ray photoelectron spectroscopy(XPS) was used to analyze rinsed and not rinsed LiNi0.8Co0.2O2-based high power lithium-ion battery cathodes following calendar-life testing at 50 °C, 60% state-of-charge. XP spectra were obtained using incident monochromatic AlKα radiation at 0.83401 nm. A survey spectrum together with F 1s, O 1s, C 1s, P 2p and Li 1s are presented. The spectra indicate the principal core level photoelectron and Auger electron signals.

Calendar Degradation Mechanism of Lithium Ion Batteries with a LiMn2O4 and LiNi0.5Co0.2Mn0.3O2 Blended Cathode

Introduction In recent years, the degradation of lithium-ion batteries (LIBs) has been intensively analyzed to improve the life expectancy of LIBs in electronic vehicles (EVs). Lifetime tests must be conducted under various conditions that simulate the various real environments of EVs. The degradation phenomena of LIBs are classified into cycle and calendar degradation. Most EVs are exposed to longer parking than driving periods; therefore, suppressing the calendar deterioration of LIBs during parking is important. Recently, LIBs with a mixed-phase blended cathode have been employed as energy storage devices. However, the effect of the cathode composition on performance degradation remains unclear. In this study, we conducted systematic calendar life tests at six SOCs and four temperatures using commercial 18650-type lithium-ion batteries with a Li1-x Mn2O4 and Li1-y Ni0.5Co0.2Mn0.3O2 blended cathode. To understand the degradation mechanism, we adopted nondestructive dV/dQ curve analyses[1]. Experimental Calendar life tests were conducted on commercially available lithium-ion cells with a blended cathode (18650-type, 1.4 Ah). The active cathode and anode materials are Li1-x Mn2O4 + Li1-y Ni0.5Co0.2Mn0.3O2 (25:75 wt.%) and graphite, respectively. Calendar life tests were conducted at six SOCs (0%, 40%, 60%, 70%, 80%, 100%) and four temperatures (0°C, 25°C, 45°C, 60°C). The battery performance was periodically measured in low-current (C/20) charge/discharge tests over the full SOC range (0%–100%) at 25°C (measurement interval was approximately 2 months). The dV/dQ curves were calculated from the discharge curve. The cathode and anode dV/dQ curves were also obtained from the discharge curves of the half-cell against lithium metal electrode with 1 mol dm− 3 LiPF6in ethylene carbonate and diethyl carbonate (1:1 in vol.). Results and discussion The capacity retentions during the calendar life tests are shown in Fig. 1. At 25°C, the capacity decreased fast with the increase of SOC. Moreover, at 60°C, the capacity decreased more rapidly at 60% and 70% SOC than at 80% and 100% SOC. The dV/dQ curve changes during the calendar life tests are shown in Fig. 2. Two of the four peaks in the dV/dQ curve are attributable to phase transitions of the cathode (C1 and C2); the others arise from phase transitions of the anode (A1 and A2)[2]. At 25°C, a slip (decrease of the distance between A1(A2) and C1(C2)) occurred in the cathode/anode reaction region and accelerated at higher SOC. Conversely, at 60°C, negative shifts of C1 and C2 occurred. These shifts, indicating cathode degradation, were specific to 60% and 70% SOC and were accompanied by larger cathode/anode reaction region slips than that at 25°C. From the dV/dQ curves, the lithium composition of spinel type Li1-x Mn2O4 at 60% and 70% SOC was estimated as x ~ 0.2. This fraction is the manganese dissolvable composition[3] and manganese dissolution was confirmed in electrolyte analyses. According to these results, the calendar degradation mechanisms of blended cathode LIB are affected by two mechanisms: cathode/anode reaction region slip induced by electrolyte decomposition at high SOCs, and degradation of cathode by manganese dissolution of the spinel-type Li1-x Mn2O4at intermediate SOCs. Acknowledgement This study was supported in part by the New Energy and Industrial Technology Development Organization (NEDO). Reference [1] I. Bloom, et al., J. Power Sources, 139, 295 (2005). [2] K. Ando, et al., 228th ECS Meeting , No 130 (2015). [3] T. Saito, et al., 200th ECS Meeting , No. 180 (2001). Figure 1

Supercapacitor Degradation Assesment by Power Cycling and Calendar Life Tests

Abstract Degradation of Supercapacitors (SC) is quantified by accelerated ageing tests. Energy cycling tests and calendar life tests are used since they address the real operating modes. The periodic characterization is used to analyse evolution of the SC parameters as a whole, and its Helmholtz and diffusion capacitances. These parameters are determined before the ageing tests and during 3 × 105 cycles of both 75% and 100% energy cycling, respectively. Precise evaluation of the capacitance and Equivalent Series Resistance (ESR) is based on fitting the experimental data by an exponential function of voltage vs. time. The ESR increases linearly with the number (No) of cycles for both 75% and 100% energy cycling, whereas a super-linear increase of ESR vs. time of cycling is observed for the 100% energy cycling. A decrease of capacitance in time had been evaluated for 2000 hours of ageing of SC. A relative change of capacitance is ΔC/C0 = 16% for the 75% energy cycling test and ΔC/C0 = 20% for the 100% energy cycling test at temperature 25°C, while ΔC/C0 = 6% for the calendar test at temperature 22°C for a voltage bias V = 1.0 Vop. The energy cycling causes a greater decrease of capacitance in comparison with the calendar test; such results may be a consequence of increasing the temperature due to the Joule heat created in the SC structure. The charge/discharge current value is the same for both 75% and 100% energy cycling tests, so it is the Joule heat created on both the equivalent series resistance and time-dependent diffuse resistance that should be the source of degradation of the SC structure. The diffuse resistance reaches a value of up to 30Ω within each 75% energy cycle and up to about 43Ω within each 100% energy cycle.

Capacity fading of LiAlyNi1−x−yCoxO2 cathode for lithium-ion batteries during accelerated calendar and cycle life tests (effect of depth of discharge in charge–discharge cycling on the suppression of the micro-crack generation of LiAlyNi1−x−yCoxO2 particle)

Cycle performance of a LiAl0.10Ni0.76Co0.14O2 (NCA) cathode/graphite cell closely depended on the range of depth of discharge in charge–discharge processes (ΔDOD). When ΔDOD was 10–70%, cycle performance at 25 °C was maintained even at 60 °C. Deterioration phenomena were analyzed by electrochemical method, X-ray photoelectron spectroscopy (XPS), X-ray diffractometry (XRD), and micro-cracks in NCA particles were analyzed with cross-sectional views by scanning electron microscopy (SEM). Many micro-cracks were observed only after a 0–100% DOD region cycle test. Cycle tests in several restricted ΔDOD conditions showed that the deterioration was closely related to not the upper and lower limits of DOD or operation voltage but the width of ΔDOD.

Capacity fade of LiAlyNi1−x−yCoxO2 cathode for lithium-ion batteries during accelerated calendar and cycle life tests (surface analysis of LiAlyNi1−x−yCoxO2 cathode after cycle tests in restricted depth of discharge ranges)

Cycle performance at 60 °C for a Li Al0.10Ni0.76Co0.14O2 (NCA) cathode/graphite cell was greatly improved when a DOD range in charge–discharge cycling (ΔDOD) was restricted. The deterioration mechanism was analyzed by X-ray photoelectron spectroscopy (XPS), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and scanning transmission electron microscopy-electron energy-loss spectroscopy (STEM-EELS). Only after the cycle test in the ΔDOD of 0–100%, many micro-cracks were generated in the inter-surface between the primary particles which aggregated to form the secondary particles, and a NiO-like resistance layer with Fm3m rock salt structure was formed on each primary particle which was contact with other primary particles and electrolyte. It can be concluded that the lack of contact between the primary particles with the micro-crack generation and the formation of the new resistance layer are responsible for the capacity fading and the rise in impedance during charge–discharge cycle in the wide ΔDOD.

Surface Degradation of Mixed LiMn2O4/LiNiO2 Cathode Particles and Capacity Fade in Li-Ion Batteries During Accelerated Calendar Life Test

not Available.

Calendar and cycle life study of Li(NiMnCo)O2-based 18650 lithium-ion batteries

An extensive set of accelerated aging tests has been carried out employing a Li-ion high energy 18650 system (2.05 Ah), negative electrode: carbon, positive electrode: Li(NiMnCo)O2). It is manufactured by Sanyo, labeled UR18650E, and is a commercial off-the-shelf product. The tests comprise both calendar life tests at different ambient temperatures and constant cell voltages and cycle life tests operating the cells within several voltage ranges and levels using standard test profiles. In total, 73 cells have been tested. The calendar life test matrix especially investigates the influence of SOC on aging in detail, whereas the cycle life matrix focuses on a detailed analysis of the influence of cycle depth. The study shows significant impact of the staging behavior of the carbon electrode on cycle life. Furthermore a strong influence of the carbon potential on calendar aging has been detected. Observed relations between aging and the different influence factors as well as possible degradation mechanisms are discussed. Analysis of C/4 discharge voltage curves suggests that cycle aging results in different aging processes and changes in material properties compared to calendar aging. Cycling, especially with cycles crossing transitions between voltage plateaus of the carbon electrode seems to destroy the carbon structure.

Capacity fade of LiNi(1−x−y)CoxAlyO2 cathode for lithium-ion batteries during accelerated calendar and cycle life test. I. Comparison analysis between LiNi(1−x−y)CoxAlyO2 and LiCoO2 cathodes in cylindrical lithium-ion cells during long term storage test

Ni-based LiNi(1−x−y)CoxAlyO2 (NCA) and LiCoO2 (LCO) cathode materials taken out of lithium-ion cells after storage for 2 years at 45 °C were analyzed by various spectroscopic techniques. X-ray photoelectron spectroscopy exhibited that there was no difference between NCA and LCO. On the other hand, scanning transmission electron microscopy–electron energy-loss spectroscopy demonstrated there was a remarkably large difference between the two cathode materials. Ni-L2,3 energy-loss near-edge structure (ELNES) spectra of the NCA showed a peak at about 856.5 eV, which was assigned to trivalent nickel, was maintained even after storage, indicating that the NCA had no significant change in its surface structure during storage. On the other hand, in the Co-L2,3 ELNES spectra of the LCO a peak at about 782.5 eV, which was assigned to trivalent cobalt, significantly shifted to the lower energies after storage. These results suggest that crystal structure change of the active material surface is a predominant reason of deterioration during the storage test.