Fresh Battery Research Articles

Neutron Dark-Field Analysis of Commercial Lithium-Ion Batteries

Neutrons uniquely probe matter since the interaction is primarily mediated through the strong nuclear force. Neutron imaging uses this complementarity to create unique views of systems. For batteries, neutrons strongly interact with hydrogen and lithium, so that conventional neutron imaging readily measures the change in either electrolyte concentrations or ion migration in the case of lithium-ion batteries. A novel imaging mode, neutron dark field imaging, extends the capability of neutron imaging to enable one to measure the microstructure, that is length scales from the nm to µm [1]. The dark field is a measure of the pair correlation function, which is linked to conventional small angle scattering through the Hankel transform [2]. Thus, neutron dark field images of lithium-ion batteries can provide spatially resolved measurements (with resolution ~100 µm) of the particle distribution along the path of the neutron beam. Further, dark-field images are not strictly limited to thin sections as is typical of small angle scattering, and one can form tomographic dark-field images. The dark-field image is the change in the visibility (or amplitude) of a moiré pattern with period Pd. The dark-field probes the pair correlation function at the correlation length, ξ, related to Pd, the wavelength of the radiation, λ, and sample-detector separation, Z by ξ = λ Z / Pd [3]. To probe a broad range of correlation lengths, we formed our neutron dark field images with a neutron far field interferometer [4]. The period of the moiré pattern formed by this interferometer is tuned by changing the distance, D, between two phase modulating gratings, where Pd is inversely proportional to D. We applied neutron dark imaging to commercial lithium-ion batteries with different capacities of stored energy. Further, batteries from each capacity were subjected to wear, with 1790 cycles, labeled as worn, 125 cycles as slightly worn, and the battery with 1 charge/discharge cycle is labeled fresh. We acquired neutron dark field images, probing length scales from 100 nm to 3 µm with the batteries in both the fully charged and fully discharged states. As shown in Figure 1, we observe a more-or-less uniform dark field signal across the fresh battery in both charge states. This is contrasted with the worn batteries, which show clear inhomogeneities in the dark field signal, which indicates that the underlying electrode structures have changed in a non-uniform fashion. Our use of commercial batteries limits further quantitative analysis. Further details of the measurement process and the potential to acquire tomographic reconstructions of the microstructure will be presented. Figure 1: Neutron dark-field images at two autocorrelation lengths, xi, for three 43 mAh batteries subjected to different levels of cycling and states of charge.

The Comparison of Thermal Stability and Safety between Fresh and Aging Large Capacity Lithium Ion Battery with Silicon Carbon Anode

Due to the high energy density, lithium ion battery (LIB) plays an important role in electric vehicle (EV). However, the requirement to the energy density keeps increasing. More and more materials are selected to improve the energy density to provide more distance for EV. Silicon, as a famous anode material, provides much higher specific capacity (3579-4200 mAh/g) than graphite (372 mAh/g) does. This research focused on thermal stability and safety of a 30Ah battery with silicon carbon anode. Aging battery would also be compared with the fresh battery after several cycles to different state of health (SOH). The batteries would be analyzed by accelerating rate colorimeter (ARC) to determine the safety. The differential scanning colorimeter (DSC) evaluated the thermal stability of the batteries. The thermal stability of ARC is decided by T1, T2 and T3 which are the self-heating temperature, thermal runaway triggered temperature and the highest temperature, respectively. The scanning electron microscope (SEM) could observe the surface differences with different SOH and various silicon proportion. The research revealed an overall safety assessment of the lithium ion battery with different content of silicon anode under different SOH. Keywords: Lithium ion battery, silicon carbon, thermal runaway, thermal stability Figure 1

Capacity estimation algorithm with a second-order differential voltage curve for Li-ion batteries with NMC cathodes

Accurate diagnosis of battery degradation is important for safe and efficient battery management. Capacity is a reliable index to describe the state of health (SOH) in batteries. In this paper, a capacity estimation algorithm for Li-ion batteries with nickel, manganese, and cobalt (NMC) cathodes based on a second-order differential voltage is proposed. A reference voltage curve was obtained during the CC charging phase from a fresh battery beforehand, and the input voltage curve was measured and compared, under the same operating conditions, from an aged battery. The input voltage curve is aligned to the reference curve to minimize the error of the second-order differential voltage. The compensated charging time of the aligned curve has a linear relation with the battery capacity until capacity reduction reaches 23.5%. From the linear model, the capacity can be estimated easily. This method is verified for five packs aged with different discharge currents. In the aging cycle and the initial SOC variation test, the capacity estimation error is less than 2% until it reaches 76.5% capacity. The proposed method does not require a complete aging test (for the table) to relate the charging time and the capacity.

Li transport in fresh and aged LiMn2O4 cathodes via electrochemical strain microscopy

Transport properties of Li+ mobile ions in fresh and aged LiMn2O4 battery cathodes were studied at the nanoscale via electrochemical strain microscopy (ESM), time spectroscopy, and voltage spectroscopy mapping. Both Vegard and plausible non-Vegard contributions to the ESM signal were identified in electrochemical hysteresis loops obtained on fresh and aged samples. In the fresh cathodes, the Vegard contribution dominates the signal, while in the aged samples different shape of hysteresis loops indicates an additional plausible non-Vegard contribution. Non-uniform spatial distribution of the electrochemical loop opening in LiMn2O4 particles studied in the aged samples indicates stronger variation of the Li diffusion coefficient at the microscale as compared to the fresh specimens. Time spectroscopy measurements revealed a suppression of the local Li diffusivity in aged samples. The mechanisms of the cathode aging are discussed in the context of observed nanoscale ESM response.

The Effect of Discharge Products on the Impedance Spectra in Li-Air Batteries with Organic Electrolyte

The effects of discharge products on the impedance spectra of Li-air batteries with organic electrolyte are studied using finite element simulations. The finite element simulations are based on the theory of concentrated solutions and the complex impedance spectra are computed by linearizing the partial differential equations that describe the mass and charge transport in Li-air batteries. These equations include the oxygen diffusion equation, the Li drift-diffusion equation, and the electron conduction equation. The reaction at the anode and cathode are described by Butler-Volmer kinetics. The total impedance of a Li-air battery increases by more than 200% when the response is measured near the end of the discharge cycle as compared to on a fresh battery. The resistivity of the deposition layer significantly affects the deposition profile and the total impedance. Using electrolytes with high oxygen solubility and concentrated oxygen gas at high pressures will reduce the total impedance of Li-air batteries.

Characterization of Lithium Thin Film Batteries by Electrochemical Impedance Spectroscopy

In this study, lithium thin film batteries were characterized using Electrochemical Impedance Spectroscopy (EIS) to analyze the interfaces evolution during cycling and aging. Firstly, the conception of symmetrical Pt/LiPON/Pt blocking cells shows the resistive contribution of the solid electrolyte and let us access to the ionic transport parameters such as the ionic conductivity and the dielectric constant, respectively of 2.10-6 S.cm-1 and 20. Moreover, EIS performed on fresh and aged battery highlights an increase of LiPON/Lithium interface resistivity, which may be caused by a lithium metal degradation or oxidation at the interface. This observation was confirmed by a cycle inducing the creation of a fresh LiPON/Lithium interface and a decrease of the corresponding EIS response. Further works will focus on the understanding of the origin and the evolution of each contribution thanks to impedance characterization of half-cells.

Reduced-Order Electrochemical Model Parameters Identification and SOC Estimation for Healthy and Aged Li-Ion Batteries Part I: Parameterization Model Development for Healthy Batteries

The current phase in our transportation system represents a paradigm shift from conventional, fossil-fuel-based vehicles into the second-generation electric and hybrid vehicles. Electric vehicles (EVs) provide numerous advantages compared with conventional vehicles because they are more efficient, sustainable, greener, and cleaner. The commercial market penetration and success of EVs depend on the efficiency, safety, cost, and lifetime of the traction battery pack. One of the current key electrification challenges is to accurately estimate the battery pack state of charge (SOC) and state of health (SOH), and therefore provide an estimate of the remaining driving range at various battery states of life. To estimate the battery SOC, a high-fidelity battery model along with a robust, accurate estimation strategy is necessary. This paper provides three main contributions: 1) introducing a new SOC parameterization strategy and employing it in setting up optimizer constraints to estimate battery parameters; 2) identification of the full-set of the reduced-order electrochemical battery model parameters by using noninvasive genetic algorithm optimization on a fresh battery; and 3) model validation by using real-world driving cycles. Extensive tests have been conducted on lithium iron phosphate-based cells widely used in high-power automotive applications. Models can be effectively used onboard of battery management system.

In-situ observation of inhomogeneous degradation in large format Li-ion cells by neutron diffraction

This work presents a non-destructive in-situ method for probing degradation mechanisms in large format, operating, commercial lithium-ion batteries by neutron diffraction. A fresh battery (15 Ah capacity) was shown to have a uniform (homogeneous) local state of charge (SOC) at 4.0 V (9 Ah SOC) and 4.2 V (15 Ah SOC), with 1.33 C and 2.67 C charging rates, respectively. This battery was then aggressively cycled until it retained only a 9 Ah capacity, 60% of its original value. Inhomogeneous deterioration in the battery was observed: near the edges, both the graphite anode and the spinel-based cathode showed a significant loss of capacity, while near the central area, both electrodes functioned properly. An SOC mapping measurement of the degraded battery in the fully charged state (4.2 V) indicated that the loss of local capacity of the anode and cathode is coupled.

Simulation-Based Policy Improvement for Energy Management in Commercial Office Buildings

Many commercial office buildings have become micro smart grids with on-site power generations, storage devices, and uncertain demands. Due to the pervasive nonlinearity and randomness of such a multi-energy system, simulation is usually the only faithful way to accurately describe the system dynamics and for performance evaluation. However, simulation is usually time-consuming and each sample path provides only noisy observations. Thus finding the optimal energy management policy is nontrivial. In this paper, a joint schedule problem is considered to schedule solar power, wind power, combined cooling, heating, and power generation, high temperature chiller, liquid desiccant fresh air unit, battery, and power grid in order to satisfy the electricity load, sensible heat load, and latent heat load in buildings with the minimal expected cost. We make two major contributions in this paper. First, three simulation-based policy improvement (SBPI) methods are developed to improve from given base policies. Second, the performance of these methods are systematically analyzed through numerical experiments. We show that when there are sufficient computing budget, the SBPI methods improve the given base policies. Different methods are recommended for problems with different computing budget. Sensitivity analysis of the policy and the value of accurate information are also discussed.

Recovery of discarded sulfated lead-acid batteries by inverse charge

The aim of this research is to recover discarded sulfated lead-acid batteries in order to save the energy. In this work, the effect of inverse charge on the reactivation of sulfated active materials has been investigated. At first, the battery is deeply discharged and the electrolyte of battery is replaced with a new sulfuric acid solution of 1.28 g/cm 3. Then, the battery is inversely charged with constant current method (2 A for the battery with the nominal capacity of 40 A h) for 24 h. At the final stage, the inversely charged battery is directly charged for 48 h. Through these processes, a discarded battery can recover its capacity to more than 80% of a similar fresh and non-sulfated battery. Inverse oxidation and reduction of battery’s active materials can transform inactive sulfates into active sulfates. Discharge and cycle-life behaviors of the recovered batteries were investigated and compared with similar healthy battery. The morphology and structure of plates was studied by scanning electron microscopy (SEM) before and after inverse charge.

Recovery of discarded sulfated lead-acid batteries

The aim of this research is to recover discarded sulfated lead-acid batteries. In this work, the effect of two methods (inverse charge and chemical charge) on the reactivation of sulfated active materials was investigated. At the inverse charge, the battery is deeply discharged and the electrolyte of battery is replaced with a new sulfuric acid solution of 1.28 g cm −3. Then, the battery is inversely charged with constant current method (2 A for the battery with the nominal capacity of 40 Ah) for 24 h. At the final stage, the inversely charged battery is directly charged for 48 h. Through these processes, a discarded battery can recover its capacity to more than 80% of a similar fresh and non-sulfated battery. At the chemical charge method, there are some effective parameters that including ammonium persulfate [(NH 4) 2S 2O 8] concentration, recovery temperature and recovery time. The effect of all parameters was optimized by one at a time method. The sulfated battery is deeply discharged and then, its electrolyte was replaced by a 40% ammonium persulfate solution (as oxidant) at temperature of 50 °C. By adding of oxidant solution, the chemical charging of positive and negative plates was performed for optimum time of 1 h. The chemically charged batteries were charged with constant voltage method (2.66 V for the battery with nominal voltage and nominal capacity of 2 V and 10 Ah, respectively) for 24 h. By performing of these processes, a discarded battery can recovers its capacity to more than 84% of the similar fresh and non-sulfated battery. Discharge and cyclelife behaviors of the recovered batteries were investigated and compared with similar healthy battery. The morphology and structure of plates was studied by scanning electron microscopy (SEM) before and after recovery.

5508597 Quick exchange battery apparatus for battery powered vehicles and method therefor

An apparatus for storing and changing battery packs from a battery powered vehicle. The battery powered vehicle drives toward a light source which aligns the battery powered vehicle with the apparatus. The apparatus is moved in a horizontal plane to a position underneath a battery holding location on the battery powered vehicle. An operator moves pneumatic carrier to a position directly underneath a battery pack located in the battery holding location. The apparatus is then moved in a vertical plane so that the pneumatic carrier engages a bottom section of the battery pack. The pneumatic carrier is then activated thereby lifting the battery pack on a cushion of air. This allows the operator to move the battery pack out of the battery holding location, across a platform deck of the apparatus, and to a storage location. The operator can then use the pneumatic carrier to move a fresh battery pack located in a different storage location to the battery powered vehicle.