Fast Charging Operations Research Articles

Thermal management of Li-ion batteries in electric vehicles by nanofluid-filled loop heat pipes

An analytical model is developed to determine the thermal performance of a Loop Heat Pipe filled (LHP) with copper oxide–water and alumina–water nanofluids for battery thermal management in electric vehicles. The thermal performances of the LHP are predicted for different heat loads and nanoparticle concentrations. It is demonstrated that for fast charging operation corresponding to a heat load of 150 W, the LHP ensures evaporator temperatures of less than 60 °C for a heat sink temperature of 40 °C. The heat transport capacity of the LHP is enhanced and the evaporator temperature is deceased by augmenting the nanoparticle concentration. The water–CuO nanofluid-filled LHP performs better than the water–Al2O3 nanofluid-filled one. The addition of the nanoparticles increases the LHP total pressure drop and the driving capillary pressure. The capillary limit of the water–CuO nanofluid-filled LHP is hardly affected by CuO nanoparticle concentration until 6% beyond which the capillary limit starts decreasing. For the water–Al2O3 nanofluid-filled LHP, the capillary limit decreases when Al2O3 nanoparticle concentration increases. Beyond 6% Al2O3 nanoparticle concentration, the capillary limit of the Al2O3-filled LHP becomes lower than the water-filled one.

Fast Charging Station for Electric Vehicles Based on DC Microgrid

Increasing numbers of electric vehicles (EVs) have led to an increased power demand from the grid. The fast-charging station requires very high power for charging the EVs in a short time (30mins). The rapid high-power (80-240kW) demand results in voltage instability in the power grid. It is important to reduce the impact on the grid due to fast charging of EVs. The effect on the grid due to EVs fast charging is included in this paper. The grid instability is visible during the fast-charging period of the battery. As a solution, a renewable energy source integrated DC microgrid using a multi-step constant current fast charging method is proposed to reduce the effect on the grid. Additionally, the proposed system provides solar PV and/or vehicle to grid power transfer during the no charging/the peak demand period of the grid. The simulation and analysis of the proposed system using the coulomb counting based state of charge estimation method is implemented to show the grid impact and reduction using DC microgrid. A hardware prototype is developed to validate the proposed fast charging method and also to reduce grid impact during the fast-charging operation.

Unlocking Liquid Sulfur Chemistry for Fast-Charging Lithium-Sulfur Batteries.

A recent study of liquid sulfur produced in an electrochemical cell has prompted further investigation into regulating Li-S oxidation chemistry. In this research, we examined the liquid-to-solid sulfur transition dynamics by visually observing the electrochemical generation of sulfur on a graphene-based substrate. We investigated the charging of polysulfides at various current densities and discovered a quantitative correlation between the size and number density of liquid sulfur droplets and the applied current. However, the areal capacities exhibited less sensitivity. This observation offers valuable insights for designing fast-charging sulfur cathodes. By incorporating liquid sulfur into Li-S batteries with a high sulfur loading of 4.2 mg cm-2, the capacity retention can reach ∼100%, even when increasing the rate from 0.1 to 3 C. This study contributes to a better understanding of the kinetics involved in the liquid-solid sulfur growth in Li-S chemistry and presents viable strategies for optimizing fast-charging operations.

Electrical Vehicle Battery Charger Based on Smart Microgrid

The need to reduce pollution and the shortage of fossil fuels has led to the increased development of hybrid and full electric vehicles. There is also increased development and an increased use of renewable energy resources such as photovoltaic, wind, tidal, etc. These two trends pose serious challenges to the existing grids: a lack of supply power when the demand is high, deficient management of excess power, an increased number off grid faults, grid instabilities and others. One way to increase the penetration of electric vehicles (EV) into the market and to keep the existing grid infrastructure is to combine renewable energy resources with the grid and local battery packs to make EV charging stations. This paper focuses on developing such an EV charging station. The main advantages of the proposed EV charger include the fact that it uses only off-the-shelf inverters, and it is intended to be used in households where the maximum installed power is 3.6 kW to enable fast-charging operation modes or to reduce the costs of energy while charging the EV battery; it can reduce the energy demand from the grid during peak power consumption; it has the potential to lower electrical energy costs; it offers the possibility of vehicle-to-home (V2H) implementation; it is modular (if other technologies become available and more affordable, the consumers can easily update the system, adding more power or adding other types of renewable resources).

Probing depth-dependent inhomogeneous lithium concentration in thick LiNi0.88Co0.09Al0.03O2 cathodes for lithium-ion batteries

A high energy density is an essential requirement for commercial lithium-ion batteries (LIBs) in electric vehicles (EVs) because it directly affects driving range. In addition, the fast charging performance of LIBs, which determines the charging time, is critical in the EV industry. A common approach to enhance the energy density of LIBs is to increase the active material loading by increasing the electrode thickness. However, there is limited scope for increasing the thickness of LIB electrodes in fast charging operations because the power density characteristics of LIB cells are degraded with increasing electrode thickness. Here, we estimate the lithium concentration distribution within thick LIB cathodes after charging/discharging by studying the work function distribution within the thick electrodes using Kelvin probe force microscopy (KPFM). First, to determine the relationship between the work function and lithium content in LIB cathodes, we measure the work function of thin LiNi0.88Co0.09Al0.03O2 (NCA) electrodes under various state-of-charge (SOC) conditions. From these measurements, it is demonstrated that the work function of the NCA electrodes is proportional to the SOC. The results suggest that the work function measurements obtained using KPFM can be used to estimate the Li concentration of NCA electrodes. Next, we perform depth-dependent KPFM measurements in thick NCA samples, which can provide depth profiles of the work function depending on the C-rate conditions. The work function shows a monotonic increase along the depth direction of the thick NCA cathodes, implying a depth-dependent inhomogeneous distribution of lithium concentrations.

Interfacial Model Deciphering High-Voltage Electrolytes for High Energy Density, High Safety, and Fast-Charging Lithium-Ion Batteries.

High-voltage lithium-ion batteries (LIBs) enabled by high-voltage electrolytes can effectively boost energy density and power density, which are critical requirements to achieve long travel distances, fast-charging, and reliable safety performance for electric vehicles. However, operating these batteries beyond the typical conditions of LIBs (4.3Vvs Li/Li+ ) leads to severe electrolyte decomposition, while interfacial side reactions remain elusive. These critical issues have become a bottleneck for developing electrolytes for applications in extreme conditions. Herein, an additive-free electrolyte is presented that affords high stability at high voltage (4.5VvsLi/Li+ ), lithium-dendrite-free features upon fast-charging operations (e.g., 162mAhg-1 at 3C), and superior long-term battery performance at low temperature. More importantly, a new solvation structure-related interfacial model is presented, incorporating molecular-scale interactions between the lithium-ion, anion, and solvents at the electrolyte-electrode interfaces to help interpret battery performance. This report is a pioneering study that explores the dynamic mutual-interaction interfacial behaviors on the lithium layered oxide cathode and graphite anode simultaneously in the battery. This interfacial model enables new insights into electrode performances that differ from the known solid electrolyte interphase approach to be revealed, and sets new guidelines for the design of versatile electrolytes for metal-ion batteries.

Modeling of thermal runaway propagation of NMC battery packs after fast charging operation

This study presents a mathematical model and experimental verification of factors influencing thermal runaway propagation of NCM811/C lithium-ion battery module after fast charging operation. The key factors considered for the thermal runaway propagation include charging C-rate, battery spacing, triggering temperature, speed, and interval of the thermal runaway propagation. The analysis of the 3D model shows that increasing the spacing and triggering temperature of the battery will reduce the risk of thermal runaway propagation of the battery module and change the order of thermal runaway propagation. Further, the thermal runaway propagation speed increases gradually with the propagation process; however, it is inhibited by increasing triggering temperature and battery spacing and the decrease of charging C-rate. These observations play a critical role in the lithium-ion battery pack design.

High Frequency MOSFET Charging Circuit Using Series Parallel DC-DC Resonant Converter for Wireless Power Application

This paper proposes a new circuit topology of high frequency switching DC-DC Series Parallel Loaded Resonant Converter (SPLRC). The circuit is proposed to be used for a wireless power transmission application that required fast-charging operation. Most of the components used here are low-cost and commercially available in the market. Then, the purpose circuit is transformed into a different equivalent circuit that can efficiently analyze AC and DC modes. For each model, the operation for the converter is first described and explained. A full detailed circuit simulation is then carried out to find out the workability of the purpose converter. From the simulation, optimization is carried out. Here the components value is obtained. MATLAB R2018A is used for simulation purposes rather than being tested again using PSIM software to further prove the validity of the model. All the finding is explained and discussed, here, from the simulation result, it is confirmed that a high-frequency switching circuit is operated as expected.

Experimental study of a DC charging station for full electric and plug in hybrid vehicles

Abstract This paper is aimed to analyze design criteria, setting up, control strategies and experimental tests related to a power configuration of DC micro-grid for fast charging of full electric and plug in hybrid vehicles. The proposed DC fast charging architecture is derived by an analysis comparing the main characteristics of well known architectures, mainly based on AC and DC bus, taking also into account the integration of renewable energy sources (RESs) with stationary energy storage systems and fleets of road electric/hybrid vehicles. On the base of the proposed architecture a laboratory prototype of charging station has been realized by means of a 20 kW AC/DC bidirectional grid tie converter interconnected with two different power DC/DC converters of similar rated power. In this micro-grid architecture the AC/DC converter realizes a conversion stage at 790 V DC, whereas other two converters allow either the electric vehicle battery packs to be charged or an energy storage buffer to save electric energy and support the main grid during the fast charging operations. The laboratory tests described in this paper are mainly devoted to characterize the laboratory demonstrator, in different operative conditions, such as vehicle-to-grid (V2G), charging/discharging operations of different types of storage systems and fast charging operations of road electric vehicles. Then the study of the proposed power conversion architecture is focused on the evaluation of charging/discharging power, efficiency, energy flux management and its impact on the main grid. In addition proper control strategies are evaluated and implemented, allowing the proposed architecture to follow the required operations. The obtained experimental results demonstrate real advantages in terms of charging times and power requirements from the main grid, when adopting DC buffer architecture for fast charging operations. Finally, these results support the identification of a knowledge base, useful to evaluate energy management and control strategies to be adopted for DC charging stations and each one of their power converters in a smart grid scenario with distributed generation systems.

Investigation on the stability of two-strand superconducting cable related with ramp-rate limitation

Ramp-rate limitation, which is known as the serious obstacle for fast charging operation of superconducting magnet, is investigated by the experiment of a two-strand sample conductor and the numerical analysis. During this ramp-rate limitation experiment, the sample showed quench recovery by current redistribution or irreversible `cable quench' depending on the operation conditions. To investigate the recovery or the quench criterion, we performed precise numerical analysis considering both electro-magnetic and thermal interactions of the cable. With the minimal assumed parameters, the simulation result shows that the status of the low-current strand determines `recovery' or `cable quench' when the `local quench' first occurs at the high-current strand. Heat transfer conditions of the cable such as boiling heat transfer and contact heat transfer between the strands as well as the current non-uniformity are critical factors for the stability criterion. This paper describes the most fundamental cable quench recovery process that is influenced by field-ramping condition of the superconducting cable.

Investigation on the stability of two-strand superconducting cable related with ramp-rate limitation

Ramp-rate limitation, which is known as the serious obstacle for fast charging operation of superconducting magnet, is investigated by the experiment of a two-strand sample conductor and the numerical analysis. During this ramp-rate limitation experiment, the sample showed quench recovery by current redistribution or irreversible `cable quench' depending on the operation conditions. To investigate the recovery or the quench criterion, we performed precise numerical analysis considering both electro-magnetic and thermal interactions of the cable. With the minimal assumed parameters, the simulation result shows that the status of the low-current strand determines `recovery' or `cable quench' when the `local quench' first occurs at the high-current strand. Heat transfer conditions of the cable such as boiling heat transfer and contact heat transfer between the strands as well as the current non-uniformity are critical factors for the stability criterion. This paper describes the most fundamental cable quench recovery process that is influenced by field-ramping condition of the superconducting cable.