Extreme Fast Charging Research Articles

Extreme Fast Charging Capability in Graphite Anode via a Lithium Borate Type Biobased Polymer as Aqueous Polyelectrolyte Binder

Desolvation of lithium ions and diffusion of Li+ through the solid electrolyte interface (SEI) play an important role in determining the extreme fast-charging ability of graphite for electric vehicle (EV) application. For this reason, a novel aqueous borate type bio-based polymer with inherent Li ions was designed as an SEI forming binder for graphite. The low lying LUMO energy level enabled the preferential reduction of the binder prior to the degradation of the electrolyte or salt to form a thinner and highly conducting borate rich SEI. A robust boron rich SEI and a binder with inherent Li ions improved the kinetics with low activation energy for lithiation/desolvation (22.56 kJ/mol), lower SEI resistance, and a high Li+ diffusion coefficient across the graphite galleries (7.24 × 10–9 cm2 s–1). Anodic half-cells with the novel binder delivered a discharge capacity of 73 mAh/g at 10 C, which is three times higher than the those of the polyvinylidene fluoride (PVDF) and sodium carboxymethyl cellulose/polystyrene-polybutadiene rubber (CMC-SBR) counterparts, with a high capacity retention for more than 1000 cycles.

Unlocking Charge Transfer Limitations for Extreme Fast Charging of Li-Ion Batteries.

Extreme fast charging (XFC) of high-energy Li-ion batteries is a key enabler of electrified transportation. While previous studies mainly focused on improving Li ion mass transport in electrodes and electrolytes, the limitations of charge transfer across electrode-electrolyte interfaces remain underexplored. Herein we unravel how charge transfer kinetics dictates the fast rechargeability of Li-ion cells. Li ion transfer across the cathode-electrolyte interface is found to be rate-limiting during XFC, but the charge transfer energy barrier at both the cathode and anode have to be reduced simultaneously to prevent Li plating, which is achieved through electrolyte engineering. By unlocking charge transfer limitations, 184 Wh kg-1 pouch cells demonstrate stable XFC (10-min charge to 80 %) which is otherwise unachievable, and the lifetime of 245 Wh kg-1 21700 cells is quintupled during fast charging (25-min charge to 80 %).

Unlocking Charge Transfer Limitations for Extreme Fast Charging of Li‐Ion Batteries

AbstractExtreme fast charging (XFC) of high‐energy Li‐ion batteries is a key enabler of electrified transportation. While previous studies mainly focused on improving Li ion mass transport in electrodes and electrolytes, the limitations of charge transfer across electrode–electrolyte interfaces remain underexplored. Herein we unravel how charge transfer kinetics dictates the fast rechargeability of Li‐ion cells. Li ion transfer across the cathode–electrolyte interface is found to be rate‐limiting during XFC, but the charge transfer energy barrier at both the cathode and anode have to be reduced simultaneously to prevent Li plating, which is achieved through electrolyte engineering. By unlocking charge transfer limitations, 184 Wh kg−1 pouch cells demonstrate stable XFC (10‐min charge to 80 %) which is otherwise unachievable, and the lifetime of 245 Wh kg−1 21700 cells is quintupled during fast charging (25‐min charge to 80 %).

The In-situ Characterization of Fast-charging Degradation Modes in Li-ion Batteries Using High-resolution Neutron Imaging

Extreme fast charging (XFC) of lithium-ion batteries (LIBs) in 10 minutes is one of the main goals of the US Advanced Battery Consortium for low-cost, fast-charged electric vehicles by 2023. However, existing LIBs cannot achieve these XFC goals without significant capacity fade over cycling due to complex XFC degradation modes. One of the key XFC failure mechanisms is dead Li plating on the graphite anode. While numerous methods have detected Li plating, they lack three-dimensional non-invasive visualization of dead Li on graphite anodes in full cells during battery cycling. Herein, we demonstrate the viability of high-resolution (spatial resolution: 10–15 μm) neutron micro-computed tomography (μCT) for in-situ characterization of dead Li on graphite anodes (thickness: ~130 μm) in full cells containing NMC cathode, that were cycled at 1C and 6C.

Design, development, and techno-economic analysis of extreme fast charging topologies using Super Capacitor and Li-Ion Battery combinations

In the past few decades, it has been observed that Renewable Energy System (RES) coupled with a grid is a potential option for fulfilling the fast-growing load demand. However, the intermittent nature of renewable energy resources limits the performance of RES and prevents it from being properly utilized. This results in power quality issues and grid system instability. To address this issue, it is a common practice to combine RES with effective energy storage technologies, including the latest storage system based on Lithium-Ion Batteries (LIB) and Super Capacitors (SC). However, the fast charging of LIB and slow discharging of SC are still debatable. Time taken for charging LIB is usually sky-high that the Cost of Energy (CoE) becomes unprofitable. On the other side, although the charging of SC is faster, but undergoes quick discharging. Hence, in this paper, a cutting-edge model of LIB, i.e., an extreme Fast Charging LIB (FCLIB) is developed, where LIB is integrated with fast charging SC. This reduces the charging time of storage systems in comparison with conventional systems. In the current paper, six alternative topologies of FCLIB are developed and analyzed for CoE estimation, using real commercial load profiles and resource data. It is observed that the proposed FCLIB with the best topology is achieving 80 % of its State of Charge (SoC) in 5.84 min and 100 % of SoC in 13.5 min. The Optimized Electric Renewable Model (OERM) was employed to analyze the techno-economic analysis of the proposed FCLIB. It is estimated that the proposed topology of FCLIB has a CoE of 0.32$/kWh with fast charging, which is approximately equal to the CoE of a conventional slow charging LIB (estimated as 0.33$/kWh). Thus, the designed FCLIB provides an optimal storage solution for RES to overcome the intermittent nature of renewable energy resources to meet the load demand.

Extreme Fast Charging: Effect of Positive Electrode Material on Crosstalk

Extreme fast charging (XFC) is a key requirement for the adoption of battery-based electric vehicles by the transportation sector. However, XFC has been shown to accelerate degradation, causing the capacity, life, and safety of batteries to deteriorate. We tested cells containing five positive electrode chemistries, LFP (olivine structure), LMO (spinel), LCO (layered), NMC811 (layered) and NCA (layered), using fast-charging protocols. After testing, the negative electrodes from cells containing positive electrodes crystallizing with a layered structure were found to have more lithium deposited on their surfaces. Those crystallizing with a layered structure also tended to have a larger increase in impedance than those crystallizing with a spinel or olivine structure. Characterization of the negative electrodes by X-ray photoelectron spectroscopy showed that using the concentrations of LiF and LixPOyFz as metrics, the concentration of LiF in the SEI from the cell with different positive electrodes is LFP > LMO > LCO ∼ NMC811 > NCA; and for LixPOyFz, the order is LMO > LFP > NCA > NMC811 > LCO. Clearly, the positive-electrode material was influencing the amounts of these materials formed.

Simultaneous neutron and X-ray tomography for visualization of graphite electrode degradation in fast-charged lithium-ion batteries

Advanced battery characterization using neutron and X-ray-based imaging modalities is crucial to reveal fundamental degradation modes of lithium-ion batteries (LIBs). Taking advantage of the sensitivity of neutrons to some low-Z (Li) and X-rays to high-Z materials (Cu), here we demonstrate the viability of simultaneous neutron- and X-ray-based tomography (NeXT) as a non-destructive imaging platform for ex situ 3D visualization of graphite electrode degradation following extreme fast charging (XFC). In addition, we underscore the benefits of the simultaneous nature of NeXT by combining the neutron and X-ray data from the same sample location for material identification and segmentation of one pristine and two XFC-cycled graphite electrodes (9C charge for 450 cycles). Our ex situ results and methodology development pave the way for the design of NeXT-friendly LIB geometries that will allow operando and/or in situ three-dimensional (3D) visualization of electrode degradation during XFC. • Simultaneous neutron and X-ray tomography (NeXT) is a non-invasive imaging method • NeXT enables visualization of graphite electrode degradation after fast charging • NeXT overlaps neutron and X-ray data from same sample area to identify materials • NeXT shows qualitative correlation between electrode degradation and plated Li Advanced battery characterization is critical to reveal fundamental degradation modes of lithium-ion batteries. Using the sensitivity of neutrons to lithium and X-rays to copper, Yusuf et al. demonstrate the viability of simultaneous neutron and X-ray tomography as a non-invasive imaging modality for visualization of graphite electrode degradation following fast charging.

Mitigating Heterogeneities in Lithium-Ion Battery Modules Under Fast Charging

Temperature control is essential for fast-charging performance of Li-ion battery. Cold temperature leads to sluggish ion transportation of electrolyte, brittle polymeric cell components, changes in solid electrolyte interface (SEI) properties and associated resistance build-up, and Li plating and dendrite growth [1]. High temperature boosts fast charging but can also accelerate battery degradation and increase the rise of battery thermal failure. This is caused by the increased rate of side-reactions, resulting in loss of cyclable lithium and higher rate of attrition of active materials at higher temperatures.Temperature and its gradient in a battery unit strongly affect performance and life of battery units [2]. It is recommended that pack temperature uniformity of a li-ion battery pack in electric vehicles shall be less than 3 ºC [3]. Battery thermal management systems (BTMS) are important for controlling battery pack temperature and minimizing temperature gradients to prevent thermal-related issues in Battery Energy Storage Systems (BESS). This thermal management goal is more critical for fast charging of battery modules made of large format, high-energy-density cells. Current BTMS in battery electric vehicles (BEVs) are inadequate in limiting the maximum temperature rise of the battery during extreme fast charge (i.e., 6C charge). To achieve fast-charge, the size of the battery thermal management system needs to increase from today’s BEV average size of 1–5 kW to around 15–25 kW [4].A combined experimental and modelling approach is employed to access thermal and electrochemical heterogeneities of a battery module under extreme fast charge conditions and develop corresponding mitigation approaches. The electrochemical-thermal model was built based on electrical characterization of 32 mAh pouch cells, including constant-current 1C to 9C rates of charging at varying temperatures. Predictive performance of the model in heat generation was validated by comparing results against measurements conducted using a microcalorimeter. Thereafter, the validated model is used to predict performance of a battery module consisting of six large format pouch cells. The large pouch cell has a capacity of 25 Ah and the identical electrode design of the 32 mAh cells. 3D simulation results suggest significant temperature and charge differences can be produced. The heterogeneous behavior was enlarged along charging. As shown in Figure 1, it was found that electrodes close to the tabs were preferentially charged.Cell electrochemical heterogeneity can be reduced by reducing cell temperature difference. Two potential solutions are investigated using the developed 3D model, including the enhancement of heat transfer within cells, such as increasing cell thermal conductivities with thicker current collectors, and the optimal design of thermal management systems. The feasibility of state-of-the-art thermal management strategies for fast charging is evaluated, including liquid cooling using cold plate devices and direct liquid cooling.

Key Aging Modes and Mechanisms for Extreme Fast Charging of Lithium-Ion Batteries

Enabling extreme fast charging (XFC, charging in 10 to 15 minutes) in a lithium-ion battery (LiB) could play a key role in subsiding consumer’s range anxiety and spur the widespread adoption of electric vehicles (EVs).1,2 Such a high rate of charging induces unique aging modes in LiBs, thereby requiring a comprehensive understanding to enable effective solution strategies to minimize the negative effects of life and performance. This presentation will present a comprehensive understanding of the dominating aging modes and mechanisms of XFC in low- and moderate-loading Gr/NMC LiBs.We will discuss the major limitations of XFC in LiBs by first using experimental and modeling results followed by a comprehensive electrochemical analysis of cycle life aging implications for different charging conditions (e.g., 1C to 9C rate conditions). We will then discuss the aging mechanisms using comprehensive post-testing as well as multimodal and multi-scale microscopy techniques.Solid state diffusion in the negative electrode is not a key limiting factor for the fast charge conditions evaluated. Inadequate Li+ transport through the electrolyte primarily causes performance and distinct aging phenomena in LiBs. Eliminating the Li+ transport limitation within the electrolyte can offer a distinct increase in material utilization, avoiding Li deposition. Under such circumstances, the cathode could degrade in distinct ways depending on the particular NMC (e.g., NMC532 vs. NMC811) variants.NMC811 experiences a greater subsurface crystallographic degradation and interfacial degradation and displays similar extents of sub-particle cracking as compared to NMC532 under comparable charging conditions. Surprisingly, the NMC811 maintains superior electrochemical performance despite the more aggressive degradations. We found the better cycle life performance of NMC811 to be related to its inherently better solid state diffusion, electronic conduction, and radially oriented grain architecture. References S. Ahmed et al., J. Power Sources, 367, 250–262 (2017).Y. Liu, Y. Zhu, and Y. Cui, Nat. Energy, 4, 540–550 (2019).

Carbon-Binder Optimization for Lithium-Ion Battery Extreme Fast Charge

Battery performance is strongly correlated with electrode microstructure and weight loading of the electrode components. Among them are the carbon-black and binder additives that enhance effective conductivity and provide mechanical integrity. However, these both reduce effective ionic transport in the electrolyte phase and reduce energy density. Therefore, an optimal additive loading is required to maximize performance, especially for fast charging where ionic transport is essential. Such optimization analysis is however challenging due to the nanoscale imaging limitations that prevent characterizing this additive phase and thus quantifying its impact on performance.In this work [1], an additive-phase generation algorithm [2] has been developed to remedy this limitation and identify percolation threshold used to define a minimal additive loading (cf. figure, left). Impact of carbon-black binder (CBD) loading on electrochemical performance has been investigated through a wide array of numerical methods and experiments on NMC/graphite cells. These range from the representation, characterization, and homogenization of electrode microstructures, battery macroscale modeling, and impedance and rate capabilities measurements on various cell formats. The combined work provides information on connectivity/percolation of the solid network, effective solid conductivity and ionic diffusivity, interfacial area, cell capacity, lithium plating, impedance, and transport polarization at the beginning of life (BOL) [1]. Rate capability test demonstrates capacity improvement at fast charge at BOL (cf. figure, right), from 37% to 55%, respectively for high (10%wt) and low (4%wt) additive loading during 6C CC charging (and from 80% to 86% at the end of 10 min 6 CC-CV), in agreement with macroscale model. Improvements are attributed to a combination of lower cathode impedance, reduced electrode tortuosity and cathode thickness [1].[1] F. Usseglio-Viretta et. al., Carbon-binder Weight Loading Optimization for Improved Lithium-ion Battery Rate Capability, submitted to Journal of the Electrochemical Society [2] F. Usseglio-Viretta et. al., SoftwareX, 17, 100915 (2022), https://doi.org/10.1016/j.softx.2021.100915 Figure 1

50C Fast-Charge Li-Ion Batteries using a Graphite Anode.

Li-ion batteries have made inroads into the electric vehicle market with high energy densities, yet they still suffer from slow kinetics limited by the graphite anode. Here, electrolytes enabling extreme fast charging (XFC) of a microsized graphite anode without Li plating are designed. Comprehensive characterization and simulations on the diffusion of Li+ in the bulk electrolyte, charge-transfer process, and the solid electrolyte interphase (SEI) demonstrate that high ionic conductivity, low desolvation energy of Li+ , and protective SEI are essential for XFC. Based on the criterion, two fast-charging electrolytes are designed: low-voltage 1.8m LiFSI in 1,3-dioxolane (for LiFePO4 ||graphite cells) and high-voltage 1.0m LiPF6 in a mixture of 4-fluoroethylene carbonate and acetonitrile (7:3 by vol) (for LiNi0.8 Co0.1 Mn0.1 O2 ||graphite cells). The former electrolyte enables the graphite electrode to achieve 180 mAh g-1 at 50C (1C = 370 mAh g-1 ), which is 10 times higher than that of a conventional electrolyte. The latter electrolyte enables LiNi0.8 Co0.1 Mn0.1 O2 ||graphite cells (2 mAh cm-2 , N/P ratio = 1) to provide a record-breaking reversible capacity of 170 mAh g-1 at 4C charge and 0.3C discharge. This work unveils the key mechanisms for XFC and provides instructive electrolyte design principles for practical fast-charging LIBs with graphite anodes.

Extreme fast charge aging: Effect of electrode loading and NMC composition on inhomogeneous degradation in graphite bulk and electrode/electrolyte interface

Empowering extreme fast charging (XFC) requires a comprehensive understanding of its application with advanced anode and cathode materials in lithium-ion batteries. No report exists for the full extent of limitations for the anode with crosstalk effect from paired cathode as well as Li plating due to electrode loading under XFC. In this study, a combination of cell testing and multiple length characterization is used to investigate XFC aging mechanism in cells with a low loading of 1.5 mAh cm−2 and high loading of 2.5 mAh cm−2 for graphite (Gr)/Ni-rich LiNixMnyCo1-x-yO2 (NMCs). Operando XRD mappings show 1.5 mAh cm−2 loadings result in higher strain in graphite for all three cathode types. Among the three NMC cathodes, the graphite from NMC532 and NMC811 cells show comparable strain. Scanning electron microscopy (SEM) images show distinct differences between 6-C-charged anodes in two loadings. Significantly increased electrode thickness can be seen due to more damage in the graphite bulk and accumulation of the electrolyte decomposition products in electrode pores. X-ray photoelectron spectroscopy (XPS) reveals both cathode chemistry and Li plating influence the non-uniform SEI composition on graphite surface. Higher Ni content in NMC811 promotes the higher levels of salt decomposition on the SEI and formation of higher mass of electrolyte aging products.

Hidden Markov Models-Based Anomaly Correlations for the Cyber-Physical Security of EV Charging Stations

Over recent years, we have seen a significant rise in electric mobility to overcome the anthropogenic emissions by conventional gasoline vehicles. However, the prerequisite of smoothening of peaks and imbalances through bidirectional charging is concatenated with the undesired impacts on reliability and security of power system operation when there are probable intrusions in the eXtreme Fast Charging (XFC) station, hence destabilizing the charging networks. So this paper applies STRIDE based threat modeling to analyze and identify multiple potential threats endured by the cyber-physical system (CPS) of XFC station by using weighted attack defense tree. Potential mitigation strategies are then suggested for the identified severe threats. In addition, this paper also develops a stochastic probabilistic tool, the Hidden Markov Model (HMM) for modeling the security attacks for a given range of identified attack vectors and hence employing an appropriate defense strategy against the malicious hacker. Also, a weighted attack defense tree has been developed to generate various attack scenarios. In the end, the results of the proposed work are substantiated and validated if it is able to considerably improve overall charging efficiency and cyber-physical security of the charging station network.

Microstructure engineering of nickel-rich oxide/carbon composite cathodes for fast charging of lithium-ion batteries

Notwithstanding the rapid advances in electric vehicles for supplanting internal combustion engines, the widespread adoption of lithium-ion battery-powered electric vehicles remains hindered owing to their relatively low power density, which correlates with their charging time. In this study, the ionic and electronic conduction properties of electrodes were balanced by rationally designing the physical properties of the electrodes. The optimized NCA/conductive additive composite electrode required only 8.2 min for charging to 80% of the state of charge. This work paves the way to achieve extreme fast charging, thus helping to usher in a new era of electric vehicles.

(Invited) Battery Design for Fast Charging

Lithium-ion batteries (LIBs) has been broadly applied in electric vehicles (EVs) and the market adoption of EVs can be further improved with enhanced fast charging capabilities. The state-of-the-art chemistries, such as LiNixMnyCo1-x-yO2 (NMC) and graphite, are capable for fast charging. However, the electrodes are limited to thin coating due to mass transport limitation, which results in low energy density and high cost [1]. For example, the United States Department of Energy (DOE) issued a call for proposal in 2017 to enable extreme fast charging with a target of cell energy density higher than 180 Wh/kg which is much lower than that under normal application.The energy density of LIBs depends on the materials properties and cell engineering. In this presentation, the impact of cell design on energy density under fast charging will be discussed. Specifically, design in electrodes, current collectors, electrolyte, and separator will be elaborated to show their correlation to fast charging application [2-3]. Acknowledgment This research at Oak Ridge National Laboratory (ORNL), managed by UT Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725, was sponsored by the Office of Energy Efficiency and Renewable Energy (EERE) Vehicle Technologies Office (VTO) and Advanced Manufacturing Office (AMO).

Cylindrical Battery Fault Detection Under Extreme Fast Charging: A Physics-Based Learning Approach

High power operation in extreme fast charging significantly increases the risk of internal faults in Electric Vehicle batteries which can lead to accelerated battery failure. Early detection of these faults is crucial for battery safety and widespread deployment of fast charging. In this setting, we propose a real-time {detection} framework for battery voltage and thermal faults. A major challenge in battery fault detection arises from the effect of uncertainties originating from sensor inaccuracies, nominal aging, or unmodelled dynamics. Inspired by physics-based learning, we explore a detection paradigm that combines physics-based models, model-based detection observers, and data-driven learning techniques to address this challenge. Specifically, we construct the {detection} observers based on an experimentally identified electrochemical-thermal model, and subsequently design the observer tuning parameters following Lyapunov's stability theory. Furthermore, we utilize Gaussian Process Regression technique to learn the model and measurement uncertainties which in turn aid the {detection} observers in distinguishing faults and uncertainties. Such uncertainty learning essentially helps suppressing their effects, potentially enabling early detection of faults. We perform simulation and experimental case studies on the proposed fault {detection} scheme verifying the potential of physics-based learning in early detection of battery faults.

Bilayer hybrid graphite anodes via freeze tape casting for extreme fast charging applications

Extreme fast charging (XFC) of lithium-ion batteries is critical for continuous market adoption of electric vehicles. However, mass transport limitations and sluggish kinetics lead to lithium plating in graphite anodes under fast charging conditions. One approach to address the mass transport limitation in graphite is to design low-tortuosity electrodes to enhance ionic transport. In this study, a bilayer hybrid structured electrode with directionally aligned channels was developed via freeze tape casting, which enables faster lithium ion diffusion through the graphite electrode. A scalable roll-to-roll process was designed in which slurry can be cast on any substrates for simple processing. Electrochemical impedance spectroscopy measurements indicated that the bilayer hybrid coating had both low tortuosity and short diffusion pathways, enabling XFC charging. Rate testing for the bilayer hybrid electrode indicated superior performance over the other coatings, exhibiting a ∼20% improvement in the charge capacity compared with the conventional coating at 5C and 10 min total charging time. The bilayer hybrid electrode also demonstrated a 10% improvement in capacity retention compared with the conventional electrode after 1000 cycles at XFC conditions. This study demonstrates freeze tape casting as a scalable way to fabricate low-tortuosity electrodes for XFC applications.

A Comprehensive Understanding of the Aging Effects of Extreme Fast Charging on High Ni NMC Cathode

AbstractAs the battery industry shifts toward high Ni content cathodes, such as LiNi0.8Mn0.1Co0.1O2 [NMC811], a complete understanding of the degradation mechanisms of NMC811 under extreme fast charging (XFC) (XFC, ≤10–15 min charging) conditions is needed. Such comprehensive understanding would identify the most critical materials gaps that need to be addressed for enabling XFC long‐life cells for electric vehicles. This study maps out the key aging mechanisms for NMC811 cycled at different XFC conditions (between 1C and 9C) for up to 1000 cycles. To acquire a fundamental understanding of utilization and degradation, cells are evaluated using a range of electrochemical techniques, and multimodal and multiscale microscopy techniques to quantify chemical, structural, and crystallographic degradation as a function of cycling conditions for the NMC cathode. When comparing NMC811 to NMC532, it is observed that NMC811 has a greater subsurface crystallographic degradation and displays a similar magnitude of subparticle cracking. However, the NMC811 maintains superior performance despite those advanced degradations. The superior cycle life performance is attributed to the NMC811 particles having radially oriented grains and improved transport properties. NMC811 shows between 4.6× and 3.15× reduction in capacity fade than NMC532 for charging rates between 4C (e.g., 15‐min charging) and 6C (10‐min charging).

Probing the Role of Multi-scale Heterogeneity in Graphite Electrodes for Extreme Fast Charging.

Electrode-scale heterogeneity can combine with complex electrochemical interactions to impede lithium-ion battery performance, particularly during fast charging. This study investigates the influence of electrode heterogeneity at different scales on the lithium-ion battery electrochemical performance under operational extremes. We employ image-based mesoscale simulation in conjunction with a three-dimensional electrochemical model to predict performance variability in 14 graphite electrode X-ray computed tomography data sets. Our analysis reveals that the tortuous anisotropy stemming from the variable particle morphology has a dominating influence on the overall cell performance. Cells with platelet morphology achieve lower capacity, higher heat generation rates, and severe plating under extreme fast charge conditions. On the contrary, the heterogeneity due to the active material clustering alone has minimal impact. Our work suggests that manufacturing electrodes with more homogeneous and isotropic particle morphology will improve electrochemical performance and improve safety, enabling electromobility.

Sizing battery energy storage and PV system in an extreme fast charging station considering uncertainties and battery degradation

This paper presents mixed integer linear programming (MILP) formulations to obtain optimal sizing for a battery energy storage system (BESS) and solar generation system in an extreme fast charging station (XFCS) to reduce the annualized total cost. The proposed model characterizes a typical year with eight representative scenarios and obtains the optimal energy management for the station and BESS operation to exploit the energy arbitrage for each scenario. Contrasting extant literature, this paper proposes a constant power constant voltage (CPCV) based improved probabilistic approach to model the XFCS charging demand for weekdays and weekends. This paper also accounts for the monthly and annual demand charges based on realistic utility tariffs. Furthermore, BESS life degradation is considered in the model to ensure no replacement is needed during the considered planning horizon. Different from the literature, this paper offers pragmatic MILP formulations to tally BESS charge/discharge cycles using the cumulative charge/discharge energy concept. McCormick relaxations and the Big-M method are utilized to relax the bi-linear terms in the BESS operational constraints. Finally, a robust optimization-based MILP model is proposed and leveraged to account for uncertainties in electricity price, solar generation, and XFCS demand. Case studies were performed to signify the efficacy of the proposed formulations.