Conventional Lead-acid Batteries Research Articles

Experimental investigation of longevity and temperature of a lithium-ion battery cell using phase change material based battery thermal management system

Nowadays, conventional lead acid batteries are being replaced by Lithium-ion batteries due to their high energy density, low cost, and high electric capacities. But when subjected to high discharge conditions, these batteries undergo a rapid increase in temperature which can make them unstable and change their internal chemistry to the point of fire or explosion due to thermal runaway and reduce their working life (electrical capacity). To prevent this, battery thermal management systems need to be used. The current work is focused on investigating the performance of a phase change material-based thermal battery management system for controlling battery temperature and battery life. In this experimental study, RT-47 Paraffin phase change material is wrapped around a 1.2Ah, 3.7 V lithium-ion battery cell with a thickness of 4 mm. The results of temperature and electrical current were recorded for 1200 s during which the battery was discharged at a constant resistance load. It was found that using a phase change material based thermal management system the temperature of the battery cell was better maintained and it lasted approximately double the time as compared to a bare battery cell under the same loading conditions.

Recent advancement in rechargeable battery technologies

AbstractThe ongoing energy issues worldwide have led to the continuous growth of the electrochemical energy storage system in recent years, and the battery is a vital part of it. The battery market, mainly rechargeable batteries, is expanding rapidly to cater to the demands of the changing society, along with the utilization of batteries in electric vehicles, the renewable energy sector, and the industrial sector. From the matured technology like the lead–acid battery to the most advanced Li‐ion (Li‐ion) battery, rechargeable battery technology has developed significantly. In comparison to the conventional lead–acid battery, other rechargeable battery technologies such as Li‐ion, nickel–metal hydride (NiMH), and nickel–cadmium (Ni–Cd) batteries are considered as more promising electrochemical energy storage systems. The Li‐ion battery, which has been on the market since 1991, is the most popular rechargeable battery due to its high energy density and good durability. With the growing market demand of battery with superior electrochemical performance in terms of specific energy, cyclability, stability, and better safety, next generation Li‐ion batteries are being widely explored in the recent time. This review discusses various rechargeable batteries which are in trend and the issues and challenges associated with it. The advancements that have taken place primarily in the electrode (both cathode and anode) materials, along with electrolytes, for improving the battery performance from the year 2000 onwards are discussed. Moreover, discussion on next‐generation batteries is also covered in this review.This article is categorized under: Emerging Technologies > Energy Storage

A comparative life cycle assessment of lithium-ion and lead-acid batteries for grid energy storage

Lithium-ion battery technology is one of the innovations gaining interest in utility-scale energy storage. However, there is a lack of scientific studies about its environmental performance. This study aims to evaluate the environmental impacts of lithium-ion batteries and conventional lead-acid batteries for stationary grid storage applications using life cycle assessment. The cradle-to-grave life cycle study shows that the environmental impacts of the lead-acid battery measured in per “kWh energy delivered” are: 2 kg CO2eq (climate change), 33 MJ (fossil fuel use), 0.02 mol H + eq (acidification potential), 10−7 disease incidence (PM2.5 emission), and 8 × 10−4 kg Sbeq (minerals and metals use). The nickel cobalt aluminum battery is the best performer for climate change and resource use (fossil fuels) among the analysed lithium-ion batteries, with 45% less impact. The nickel cobalt manganese battery performs better for the acidification potential and particulate matter impact categories, with 67% and 50% better performance than lead-acid. The lithium iron phosphate battery is the best performer at 94% less impact for the minerals and metals resource use category. The use stage electricity and battery cell manufacturing processes have the highest contribution for the most impact categories. The sensitivity analysis shows that the use-phase environmental impact decreases with an increase in renewable energy contribution in the use phase. The lithium-ion batteries have fewer environmental impacts than lead-acid batteries for the observed environmental impact categories. The study can be used as a reference to decide how to substitute lead-acid batteries with lithium-ion batteries for grid energy storage applications.

Lead acid battery with high resistance to over‐discharge using graphite based materials as cathode current collector

AbstractLead acid battery has been one of the most important battery for industry use. However, conventional lead acid battery cannot be recharged after over discharge and the performance is greatly declined. It has been revealed that the cause of not being able to be recharged is the formation of α‐PbO2 on the surface of β‐PbO2 cathode active material due to local cell reaction between lead current collector and β‐PbO2. Formation of α‐PbO2 is prevented by using gold as the current collector. In this study, we developed the lead acid battery with high resistance to over discharge using graphite materials as current collector. The formation of α‐PbO2 was prevented by using expanded natural graphite sheet as cathode current collector. The lead acid battery with current collector of expanded natural graphite sheet containing 5% polypropylene (PP) can repeat deep charge and discharge between 0 and 2 V for more than about 6 months and showed flat potential area between 1.9 and 1.3 V for every cycle. Furthermore, this battery can be charged again after over discharge for more than 4 month at the open circuit. We have succeeded to develop high performance lead acid battery.

Thickness Effect of Composite Cathode of Active Material and Graphite Current Collector on Performance of Lead Acid Battery

Introduction Lead Acid Batteries (LAB) are used in various fields, due to its low cost, high safety and excellent recyclability. Conventionally, LAB cannot be recharged after over-discharged and its performance is greatly declined. We have found that the above deterioration is caused by the formation of α-PbO2 on the surface of cathode active material β-PbO2 due to the reduction by local cell reaction between β-PbO2 and lead current collector. We also have revealed that the formation of α-PbO2 can be prevented by using gold instead of lead as current collector. In this case, the LAB can be recharged even after either discharging to 0 V or discharging to 0 V followed by 48 h open circuit [1,2]. In the case of carbon, electrode potential does not come out, so we thought that carbon has a role of stopping local cell reaction. We revealed that the LAB using graphite sheet with 5wt% polypropylene as current collector has high resistance to over-discharge [3,4]. This LAB can charge-discharge without performance degradation even after full discharge followed by 48 h rest period.We fabricated composite cathode composed of β-PbO2 as active material and expanded graphite adding 5wt% polypropylene as current collector, in order to have higher performance and ease of fabrication. It was found that the LAB using composite cathode can also be recharged even after full discharge followed by 48 h rest period. High resistance to over-discharge was indicated. Also the discharge characteristics of the LAB using the composite cathode improved, when the content of β-PbO2 was increased. The composite cathode made the LAB not only very durable in over discharge but also highly practical for use [5]. In this study, we fabricated the composite cathode of various thickness and investigated the effect of thickness on the LAB performance. Experiment We made the composite cathode with various thickness composed of expanded graphite, polypropylene 0.05 times the weight to expanded graphite and β-PbO2 1.0 times the weight to expanded graphite by a pressure molding. We used 35 % H2SO4 as electrolyte and lead plate as anode. The composite cathode was processed to 40 mm × 14 mm and the area immersed in sulfuric acid was 10 mm × 14 mm. We conducted charge-discharge experiments by using the LAB constructed as above mentioned. As the stabilization cycle, we repeated discharge at 0.25 mA for 30 min and charge at 2 mA for 20 min for 20 times, then we conducted charge discharge experiment. Results and discussion After the stabilization cycle, we discharged the LAB deep to 0 V and opened the circuit for 48 h, then we resumed charge-discharge cycle. Figure1(a) shows the charge-discharge characteristics of conventional type LAB using lead plate cathode current collector. Conventional type LAB could not resume charge-discharge cycle after full discharge followed by48 h open circuit. Figure1(b) shows the case of the LAB using composite cathode with 1.0 mm thickness. It was indicated that the LAB could resume charge-discharge cycle even after full discharge followed by 48 h open circuit.Figure2 shows detailed discharge curves for the LAB using of the composite cathode with 0.5 mm thickness or 1.0 mm thickness. The charge rate and the discharge rate was 2.0 mA and 0.1 mA, respectively. The composite cathode with 1.0 mm thickness has better characteristics in longer discharge time and higher discharge potential than that with 0.5 mm thickness. Flat discharge potential around at 1.7 V was clearly observed for the LAB using the composite cathode with 1.0 mm thickness. This means the excellence in practical performance. It was indicated that the thickness of the composite cathode is one of key factor to make the LAB highly practical for use. Reference [1] T. Iwai, D. Kitajima, S. Takai, T. Yabutsuka and T. Yao, J. Electrochem. Soc. Vol 163, Issue 14, A3087-A3090 (2016)[2] T. Iwai, M. Murakami, S. Takai, T. Yabutsuka and T. Yao, Journal of Alloys and Compounds, Vol 780, 85-89 (2019)[3] T. Yao, H. Okano, T. Iwai, S. Takai, T. Yabutsuka, T. Hosokawa, N. Misaki, K. Kurihara “Positive Electrode for Lead Storage Battery and Lead Storage Battery Using Same” PCT/JP2018/005947[4] Y. Nakamura, T. Ohkubo, H. Okano, T. Inoue, T. Hosokawa, A. Takeda, T. Iwai, T. Yabutsuka, S. takai and T. Yao, 235th ECS Meeting. Soc. Z01-2143 (2019)[5] K. Sugimoto, F. Ohira, Y. Hano, H. Okano, T. Iwai, T. Yabutsuka, S. Takai, T. Hosokawa, Y. Akamatsu, S. Yoshikawa, M. Miki, M. Kuninaka and T. Yao,239th ECS meeting. Soc. Z01-1989 (2021) Figure 1

Lead Acid Battery with Composite Cathode of Active Material and Graphite Current Collector

Introduction Lead Acid Batteries (LAB) are used in various fields, due to its low cost and excellent recyclability. Conventionally, LAB cannot be recharged after over-discharged and its performance is greatly declined. We have found that the above deterioration is causedby the formation of α-PbO2 on the surface of cathode active material β-PbO2 due to the reduction by local cell reaction between β-PbO2 and lead current collector. We also have revealed that the formation of α-PbO2 can be prevented by using gold instead of lead as current collector. In this case, the LAB can be recharged even after either discharging to 0 V or discharging to 0 V followed by 48 h open circuit [1,2]. In the case of carbon, electrode potential does not come out, so we thought that carbon has a role of stopping local cell reaction. We revealed that the LAB using graphite sheet with 5wt% polypropylene as current collector has high resistance to over-discharge [3,4,5]. This LAB can charge-discharge without performance degradation even after full discharge followed by 48 h rest period. In this study, we fabricated composite cathode composed of β-PbO2 as active material and expanded graphite as current collector, in order to get higher performance and ease of fabrication. We investigated performance of the LAB using the composite cathode. Experiment We made various kind of the composite cathode composed of β-PbO2 of 0.18-3.6 g, expanded graphite of 1.8 g and polypropylene of 0.09 g by a pressure molding. We conducted charge-discharge experiments by using the composite cathode. We used two-electrode glass cell for charge-discharge experiments. We used 35 % H2SO4 as electrolyte and lead plate as anode. Composite cathode was processed to 40 mm × 14 mm and the area immersed in sulfuric acid was 10 mm × 14 mm. As the stabilization cycle, we repeated discharge at 0.25 mA for 30 min and charge at 2 mA for 20 min for 20 times, then we conducted charge discharge experiment. Results and discussion After the stabilization cycle, we discharged LAB deep to 0 V and opened the circuit for 48 h, then we resumed charge-discharge cycle.Figure 1(a) shows the charge-discharge characteristics of conventional type LAB using lead plate cathode current collector. Conventional type LAB could not resume charge-discharge cycle after full discharge followed by48 h open circuit.Figure 1(b) shows the case of the LAB using composite cathode. It is indicated that the LAB can resume charge-discharge cycle even after full discharge followed by 48 h open circuit. It is confirmed that the composite cathode made the LAB so durable to over-discharge.Figure 2 shows detailed discharge curve of the LAB using the composite cathode composed of β-PbO2 of 3.6 g, expanded graphite of 1.8 g and polypropylene of 0.09 g. Weight composition of β-PbO2 in this composite cathode is about 65%. The charge rate was 2 mA, and the discharge rate was 0.1 mA, respectively. The flat discharge potential around at 1.6 V was observed. This means that the LAB using the composite cathode has excellent practical performance.It was indicated that the composite cathode made the LAB not only very durable in over discharge but also highly practical for use. Reference [1] T.Iwai, D.Kitajima, S.Takai, T.Yabutsuka and T.Yao, J. Electrochem. Soc. Vol 163, Issue 14, A3087-A3090 (2016)[2] T.Iwai, M.Murakami, S.Takai, T.Yabutsuka and T.Yao, Journal of Alloys and Compounds, Vol 780, 85-89 (2019)[3] T.Yao, H.Okano, T.Iwai, S.Takai, T.Yabutsuka, T.Hosokawa, N.Misaki, K.Kurihara “Positive Electrode for Lead Storage Battery and Lead Storage Battery Using Same” PCT/JP2018/005947[4] Y.Nakamura, T.Ohkubo, H.Okano, T.Inoue, T.Hosokawa, A.Takeda, T.Iwai, T.Yabutsuka, S.takai and T.Yao, 235th ECS Meeting. Soc. Z01-2143 (2019)[5] Y.Hano, H.Okano, T.Inoue, T. Hosokawa, A.Takeda, T.Iwai, T.Yabutsuka, S.Takai, and T. Yao, PRIME 2020. Soc. Z01-3448 (2020) Figure 1

SIMULASI PENGARUH LUAS PERMUKAAN ELEKTRODA TERHADAP TEGANGAN DAN KONSENTRASI PERMUKAAN ELEKTRODA PADA LEAD ACID REDOX FLOW BATTERY

Energy storage systems (ESS) with large storage capabilities, easy made, and low cost are in high demand. Dynamic lead acid battery (DLAB) as a breakthrough design compared conventional lead acid batteries offers a solution to these problems. Two Dimensional (2D) DLAB simulations with surface area variations of 8 cm2, 12 cm2, 16 cm2 and 20 cm2 were successfully build using the principle of tertiary current distribution and Nerst-Planck Interface. The results for one cycle charge-discharge test showed that the increase in surface area succeeded in increasing the final charging voltage with a value of 2.16 V; 2, 21 V; 2.30 V and 2.32 V and increase the initial discharging voltage by a value of 1.58 V; 1.59 V; 1.60 V and 1.62 V respectively but did not affect the electrode surface concentration. Dynamic lead acid battery has high energy efficiency of 70.6% -71.5%.

Performance benchmark of state-of-the-art high-power lithium-ion cells and implications for their usability in low-voltage applications

For vehicle electrical systems, high-power optimized lithium-ion batteries offer superior cycle stability, compactness and weight compared to conventional lead–acid batteries. To identify lithium-ion cell candidates during early concept and development phases, both performance characteristics and a comparison of commercialized lithium-ion cells covering different cell chemistries are needed. Since the market share of high-power lithium ion cells is limited, scientific studies and extensive characterizations are rare. This study closes the gap by benchmarking state-of-the-art high-power cells considering the requirements of 12V/48V applications. The sensible begin-of-life parameters OCV, internal resistance, and capacity were investigated by stepwise OCV measurement, pulse power characterization and capacity measurement regarding the dimensions: SOC (0% to 100%), temperature (−25°C to +55°C) and current rate (up to 30C). All cells exhibit temperature dependent OCV curves, with ambient temperatures above zero hardly affecting the OCV hysteresis. A SOC dependency of the internal resistance of the tested lithium titanate oxide cell reduces the power capability, available cell capacity and energy efficiency. This cell, in contrast to the graphite-based cells, enables a neglection of a Butler–Volmer dependency and offers high charge acceptance at negative temperatures. The internal resistance of the lithium iron phosphate cell is less affected by SOC which allows for constant power output. Above 25°C and up to 15C, energy efficiencies of the graphite-based cells exceed 95%. We conclude that the lithium iron phosphate cell is best suited for 12V applications due to its voltage band and discharge characteristics. None of the cells stand out for use in 48V applications. Our findings from benchmarking among different cell chemistries are beneficial to other research areas such as battery simulation, battery management systems, or cell/system design.

The Renaissance of Liquid Metal Batteries

Next-generation batteries with long life, high-energy capacity, and high round-trip energy efficiency are essential for future smart grid operation. Recently, Cui et al. demonstrated a battery design meeting all these requirements—a solid electrolyte-based liquid lithium-brass/zinc chloride (SELL-brass/ZnCl2) battery. Such a battery design overcomes some inherent problems of conventional ZEBRA batteries and lithium ion batteries.

Challenges in modeling high power lithium titanate oxide cells in battery management systems

Two of the key requirements in micro-hybrid vehicles are the reduction of CO2 emissions alongside extended fuel savings. These goals are being accomplished by the usage of start-stop-systems, electric boosting while accelerating and recuperation of kinetic energy during braking phases. The latter one is predominantly limited by the charge acceptance of conventional lead-acid starter batteries. Thus, sophisticated power nets are being developed and a new 48 V voltage level has been established in the last years. In comparison to the standard 12 V grid, this new level is characterized by high power capability in order to accept high charging currents during recuperative braking and also provides high discharge currents for boosting.This paper characterizes lithium titanate oxide cells suited for high power applications, such as in automotive 48 V systems, and emphasizes restrictions using state-of-the-art modeling approaches in terms of state of available power and state of charge. Therefore, open circuit behavior is analyzed in dependency on temperature, hysteresis and relaxation. Furthermore, different equivalent circuit models are evaluated regarding their accuracy for different states of charge, temperatures and current rates. It has been found that the HPPC testing procedure is limited in characterizing high current behavior. Furthermore, it is shown that the previous long-term history has a significant impact on voltage responses at certain states of charge and current rates, which originates from an inhomogeneous distribution of charge carriers on the electrode surface.

Active Cell Balancing of Li-Ion Batteries for Electric Vehicles

Electric vehicles (EV) use battery banks containing series-parallel combinations of several small units to meet the high power demand of the drive system. In recent years, lithium-ion (Li-ion) batteries are being popularly used in EVs for energy storage instead of conventional lead acid batteries due to the advantages of higher cell voltage, no memory effect, low self-discharge, longer battery life and reduced size and weight. However, Li-ion battery packs require external power balancing circuits for its protection from getting damaged by overcharge and deep discharge. This work proposes an active circuit for charge balancing of Li-ion battery packs. The proposed charge balancing circuit uses a multi-winding flyback converter with n+1 number of active switches to protect a stack of n number of series connected cells. Performance of the proposed system has been verified through computer simulation in MATLAB with a 4 cell battery pack. Simulated results were found in close agreement with the predicted behaviour of the system.

Lead-Acid Battery Sizing for a DC Auxiliary System in a Substation by the Optimization Method

Lead-acid batteries are the most frequently used energy storage facilities for the provision of a backup supply of DC auxiliary systems in substations and power plants due to their long service life and high reliability. It is possible to define the load in these systems, therefore the IEEE 485 Standard can be used for the selection of batteries according to the conventional method of selection. Special attention is paid in the paper to the technical selection of a lead-acid battery, which depends on its operational reliability that decreases with battery aging. It is defined by the extent of maintenance during its service life. A cost analysis was also carried out, which took into consideration maintenance and procurement costs, as well as the costs of the related air conditioning that keeps the prescribed temperature and ventilates the battery room. The impact is shown of selecting a lead-acid battery on the battery room’s operating safety when charging. The final selection of lead-acid battery is performed using an optimization algorithm of differential evolution. Using the optimization process, the new battery selection method includes the technical sizing criteria of the lead-acid battery, reliability of operation with maintenance, operational safety, and cost analysis. Two cases of selection of lead-acid batteries for the backup supply of a DC auxiliary system in a transmission substation are presented in the paper, where the input data were determined based on measurements in an existing substation. A comparison is made between the existing conventional and new lead-acid battery selection method based on optimization.

Grading of Lithium Ion Battery Module for Public street lighting

A module of lithium ion battery has been constructed to replace ion battery for public street lighting. The module was designed to deliver a power of minimum~120 Wh for running 10 Watt solar street llighting, with a solar panel of 80 Wp. The module consisted of 40 cylinder cells 18650 of LiFePO4. Before designing the module, all the cells have to be formatted, graded and sorted out, to obtain an optimum results. The charge-discharge testing and internal resistance were measured to every single cell using a battery analyzer. The cells grading,sorting and grouping were consecutively done to obtain an optimum LIB module. The results showed each cylinder cell delivering discharge capacity, voltage and internal resistance of ~1.2-1.4 Ah, ~ 3.2-3.3 V, and 50-70 Ω, respectively. The cells were arranged into 4 serial and 10 parallel, to produce LIB module with the power of ~130-140 Wh, which is higher than expected.The LIB module made in Indonesia, with high local content can run the public street lighting and replace the conventional Lead Acid battery.

High charge acceptance through interface reaction on carbon coated negative electrode for advanced lead-carbon battery system

In this research, the interfacial effect between the carbon layer and the negative electrode surface is evaluated as a hybrid electrode with higher charge acceptance for the advanced lead-carbon battery (ALC-battery) system. The P-60 (activated carbon) material, with high specific surface area (1787 m2 g−1) and higher electrical conductivity (98.85 S cm−1), is considered an efficient activated carbon in the present investigations and deposited on the negative electrode. Compared to the conventional lead-acid battery system, the carbon coated negative electrode of ALC-battery system exhibited higher capacity at the applied higher charge/discharge current. The efficient performance of the ALC-battery is mainly influenced by the thin layer of carbon on the active electrode surface, which induces higher charge acceptance. Furthermore, the ALC-battery showed an outstanding lifespan performance compared to the conventional lead-acid battery system in long-term operations. The resulting cycle life stability of lead-acid battery and ALC-battery is 2230 and 6780 cycles, respectively. The significant performance of the ALC-battery is mainly attributed by synergistic mechanism in hybrid electrode, which is resulted from interfacial effect. The likely synergetic reactions arises by carbon layer is (i) higher charge acceptance, (ii) controlled the formation of PbSO4 crystallite in the electrode surfaces, (iii) improved electrochemical performances and Pb redox reaction due to higher electrical conductivity properties. Thus, it can be concluded that the carbon layer deposited on the negative electrode in the ALC-battery is an efficient approach for energy storage, with increased power, capacity, and enhanced cycle life stability.

Performance of recovered and reagent grade electrolyte in a soluble lead redox cell

Abstract This paper presents the performance of ‘recovered’ electrolyte for the soluble lead flow battery, made by recycling conventional lead-acid battery electrodes, and compares it to reagent grade electrolyte for the same system. The two electrolyte compositions were cycled in static and flow cells and their charge, energy, and voltage efficiencies compared. The average charge, energy, and voltage efficiencies of static cells using 1.0 mol·dm¯³ Pb²+ recovered electrolyte were 89%, 86%, and 96%, while cells using reagent grade electrolyte averaged 63%, 49%, and 78%, respectively. The average charge efficiency of flow cells with recovered electrolyte was consistently above 80% and within 10% of the average for cells with reagent grade electrolyte. The average energy and voltage efficiencies were 62% and 73%, respectively, diverting from averages for the reagent grade electrolyte cells by less than 15%. The highest average cycle life was for cells with recovered electrolyte at 187 cycles, while that of cells with reagent grade electrolyte peaked at 102. Trace elements in both electrolyte compositions were analysed and their presence in the recovered electrolyte appears to enhance performance of the soluble lead cells. The recovered electrolyte is an electrochemically viable substitute for the reagent grade electrolyte.

Understanding the functions of carbon in the negative active-mass of the lead–acid battery: A review of progress

Abstract The addition of supplementary carbon to lead–acid batteries that are intended for use in emerging automotive duties can provide improvement in two aspects of performance. (i) In both hybrid electric and battery electric vehicles that are designed to preserve energy through the operation of regenerative-braking, conventional lead–acid batteries exhibit a rapid decline in the efficiency of the recuperative charging (which can involve rates up to 30C1) and fail quickly as a result of an accumulation of lead sulfate on the negative plate. It has been widely reported that supplementary carbon — either intimately mixed with the negative active-material or included as a separate component attached to the plate — can enhance charge-acceptance. (ii) Full-hybrid electric and battery electric vehicles employ high-voltage batteries composed of large numbers of cells connected in series. Consequently, when conventional lead–acid batteries are used in such configurations, the continuous cycling encountered in normal driving will almost certainly lead to divergence in the states-of-charge of the unit cells and thereby demand periodic equalization charges. In this application, it has been demonstrated that lead–acid batteries with supplementary carbon incorporated into the negative plate are rendered immune to the divergence problem and therefore operate without the need for an equalization charge. The inclusion of supplementary carbon does, however, promote hydrogen evolution and failure due to the loss of water from the electrolyte solution. Current research efforts are directed towards methods by which this disadvantage can be mitigated without losing the benefits that the addition of carbon provides. This review covers the extensive research that has been conducted to understand the mechanism by which the additional carbon operates, the additional studies that have sought to identify the best types and optimum amounts of carbon that should be used, together with the most effective manner for their deployment.

Topology Comparison for 48V Battery-Supercapacitor Hybrid Energy Storage System

Simulation results show that a fourfold reduction in peak battery current, and a 40% increase in vehicle range can be achieved by hybridization of a conventional lead acid battery powered neighborhood electric vehicle with supercapacitors and a controlled DC/DC converter. The reduced battery current could lead to lower total vehicle cost of ownership through reduction in the battery replacement cost.

Float-Charging Characteristics of Lithium Iron Phosphate Battery Based on Direct-Current Power Supply System in Substation

AbstractA battery pack system composed of 32 lithium iron phosphate (LiFePO4) batteries and a battery management system (BMS) were assembled according to the actual load demand of a standard 110 kV power substation. Float-charging characteristics of the system were investigated and the results showed that 97% of its initial capacity was retained after a 1-year float-charging test. Even though the voltages of two batteries showed abnormal changes, which indicated that internal changes had occurred after long-term float charging, 94% of the batteries remained stable. All of the results suggested that the use of a lithium iron phosphate battery holds promise as a substitute for the conventional valve-regulated lead-acid (VRLA) battery in a direct-current power supply system.

Nitrogen-Doped Graphene as Electrode Material with Enhanced Energy Density for Next-Generation Supercapacitor Application

Nitrogen-doped graphene (NDG), synthesized from graphene oxide by a hydrothermal process, was used to construct a non-aqueous symmetric supercapacitor. The electrochemical performance of NDG was evaluated using cyclic voltammetry, galvanostatic charge–discharge cycling and impedance analysis in a symmetrical hybrid supercapacitor cell with 1 M tetraethyl ammonium tetrafluoroborate in acetonitrile as the electrolyte. The specific capacitance of NDG is 103 F g−1 at a current density of 0.5 mA cm−2. The NDG product exhibits a remarkably high energy density of 97 Wh kg−1, which is double that of conventional lead-acid batteries. The superior capacitive behavior has also been compared with a few representative capacitor materials.

Analysis of SEI on Graphite Anode in Li Ion Cell Using LiMn2O4 Spinel Cathode

Introduction We have been developing large capacity Li ion batteries for backing up of telecommunication apparatuses. Among the many types of Li ion batteries, The LiMn2O4 is convenient for replacing conventional lead-acid batteries, which have been widely used in such backup systems. This is because the LiMn2O4 has a voltage plateau, which is close to that of lead-acid batteries, due to the combination with a graphite anode. On the other hand, long calendar life of more than 10 years at full charge is also required for backup. Mn2+ ion dissolution from the LiMn2O4 cathode is well known, and we have already reported that calendar life is greatly affected by the concentration of dissolved Mn2+ ions [1]. We have postulated the degradation mechanism by charge exchange between Mn2+and intercalated Li [1]; however, the relationships between the amount of Mn deposited on the anode and that of Li consumption, which are calculated from capacity reduction, are unclear.In this study, we analyzed the solid-electrolyte-interface (SEI) on the anode to investigate the role of Mn in the degradation of Li ion batteries for backup. Experimental We used the 18650-type cylindrical Li-ion cell (capacity: about 0.7 Ah) [2]. The cathode was a Mg-doped manganese-spinel and the anode was carbon-coated graphite. We used an ethylene carbonate and dimethyl carbonate based electrolyte containing phosphazene retardant.Sample cells were charged at four voltages (4.05, 4.10, 4.15, and 4.20 V), and the environmental temperature during float charging was maintained at 50°C. The cells were discharged periodically at a current of 0.2 C (at 25°C) to evaluate their residual capacity.Degraded cells were disassembled and six different points of the anode were analyzed. The Mn content was analyzed using an inductively coupled plasma (ICP) method. We also used Li7-nuclear magnetic resonance(NMR) to identify the species on the anode. A LiCl solution of 1M was used as the standard sample. Results Figure 1 shows the lifetime of each floating charge voltage. Lifetime is defined as the duration at which the discharged capacity remains under 70% initial capacity. We found that lifetime decreased greatly between 4.15 and 4.2 V, presumably due to the phenomenon of deterioration caused by electrolyte decomposition since this test was conducted at 50°C. The lifetime at 4.05 V was slightly shorter compared with those at 4.10 and 4.15 V. The reason for this is uncertain.More than 103 times the amount of Li was observed on the degraded anode compared with that of Mg by using the ICP method. This result shows that the simple charge exchange mechanism between Mn2+ and intercalated Li will be rejected. Figure 2 shows the Li7-NMR spectrum of the anode. Two peaks were identified. One was the broad peak of which the chemical shift was -12.2 ppm. The other was that of which the chemical shift was 2.4 ppm. The area of the former was about 98%, and the latter was identified inorganic Li compound. The former may be an organic Li compound, although the chemical species remains unclear. It is known that SEI forms compact inorganic compounds, such as LiF, and organic Li compounds. The results from this study suggest that the formation of organic Li compounds is the main cause of Li consumption and that Mg deposition may accelerate organic Li compound formation. References (1) T. Tsujikawa, K. Yabuta, T. Matsushita, M. Arakawa, K. Hayashi, J. Electrochem. Soc., 158, 322 (2011).(2) T. Tsujikawa, K. Yabuta, T. Matsushita, T. Matsushima, K. Hayashi, and M. Arakawa, J. Power Sources, 189, pp. 429-434 (2009).