Query: solid lithium ion pulse current

title: Analysis on pulse charging discharging strategies for improving capacity retention rates of lithium ion batteries
abstract: The capacity fade of lithium ion batteries (LIBs) are intimately dependent upon charging discharging strategies. In this work, a pseudo two dimensional model coupled with thermal effects was developed to investigate the effects of pulse current charging discharging strategies on the capacity fade for LIBs, in which the growth of solid electrolyte interphase (SEI) and the lithium ion migration process are highlighted. LiFePO 4 /graphite (LFP) batteries were taken as samples. The capacity fading processes of the LFP batteries under different pulse current charging discharging strategies were studied by numerical simulations. The impacts of the growth of the SEI layer at the negative electrode on the capacity degradation were studied by using eleven charging discharging cases. The results show that, compared with the constant current constant voltage (CC CV) strategy, the pulse current constant voltage (PC CV) strategies can effectively alleviate the capacity fade of the LFP batteries due to the relaxation process in the pulse charging process. Under the PC CV strategies, the relaxation duration and the peak current were altered. The relaxation process renders the decrease of the current density of side reactions in the batteries, which is conducive to the recovery of the aged batteries, thus improving the capacity retention rates of the batteries. The advantages of the PC CV strategies were demonstrated in this work. The results will provide theoretical guidance for the rapid charging discharging strategies of LIBs.

title: Effects of pulse charging by triboelectric nanogenerators on the performance of solid state lithium metal batteries.
abstract: Solid state lithium metal batteries (SSLMBs) are an emerging technology since they can effectively solve the safety problem facing the lithium ion batteries with non aqueous liquid electrolyte. However, the lithium dendrite problem in SSLMBs can still occur at the sites of grain boundaries and defects. It is reported that effective charge procedures enable to suppress the growth of lithium dendrite, especially pulse charging mode. In this work, solid state lithium metal batteries were charged by a vertical contact separation triboelectric nanogenerator (TENG) The effects of pulse current on lithium dendrite growth of SSLMBs are studied. It is found that the lithium ions can diffuse uniformly during the intermittent period of the pulse current compared to the constant current charge, so the growth rate of the lithium dendrites is effectively inhibited by the pulse current. At the same time, it is found that the lower the frequency of TENG is, the slower the growth rate of lithium dendrites is. This work provides a guideline for designing appropriate charging method for durable solid state lithium metal batteries.

title: Experimental and numerical analysis to identify the performance limiting mechanisms in solid state lithium cells under pulse operating conditions.
abstract: Solid state lithium batteries could reduce the safety concern due to thermal runaway while improving the gravimetric and volumetric energy density beyond the existing practical limits of lithium ion batteries. The successful commercialisation of solid state lithium batteries depends on understanding and addressing the bottlenecks limiting the cell performance under realistic operational conditions such as dynamic current profiles of different pulse amplitudes. This study focuses on experimental analysis and continuum modelling of cell behaviour under pulse operating conditions, with most model parameters estimated from experimental measurements. By using a combined impedance and distribution of relaxation times analysis, we show that charge transfer at both interfaces occurs between the microseconds and milliseconds timescale. We also demonstrate that a simplified set of governing equations, rather than the conventional Poisson Nernst Planck equations, are sufficient to reproduce the experimentally observed behaviour during pulse discharge, pulse charging and dynamic pulse. Our simulation results suggest that solid diffusion in bulk LiCoO2 is the performance limiting mechanism under pulse operating conditions, with increasing voltage loss for lower states of charge. If bulk electrode forms the positive electrode, improvement in the ionic conductivity of the solid electrolyte beyond 10 4 S cm 1 yields marginal overall performance gains due to this solid diffusion limitation. Instead of further increasing the electrode thickness or improving the ionic conductivity on their own, we propose a holistic model based approach to cell design, in order to achieve optimum performance for known operating conditions.

title: Lithium ion Battery SoC Estimation of an Order reduced Electrochemical Model Using SMO URL in EVs
abstract: To estimate lithium ion battery SoC accurately, a lithium ion battery electrochemical model is adopted in this paper. Firstly, the electrochemical model is reasonable order reduced to an average electrode model (AEM) Secondly, sliding mode observer (SMO) with a uniform reaching law (URL) combined with AEM is developed to estimate SoC of lithium ion cell from external measured voltage and current value. An estimation scheme is designed. The observer estimates the SoC by using lithium ion solid electrolyte concentration. To demonstrate the performance of the proposed scheme, the simulations are verified by experiments from a 2.3Ah high power LiFePO4/graphite cell used in electric vehicles (EVs) The results show that the proposed estimation scheme with the SMO URL algorithm performs well with initial error values. The maximum SoC estimation errors are less than 2% under Hybrid Pulse Power Characteristic (HPPC) Test.

title: ifferential pulse effects of solid electrolyte interface formation for improving erformance on high power lithium ion battery u
abstract: Solid electrolyte interface (SEI) formation is a key that utilizes to protect the structure of graphite anode and enhances the redox stability of lithium ion batteries before entering the market. The effect of SEI formation applies a differential pulse (DP) and constant current (CC) charging on charge discharge performance and cycling behavior into brand new commercial lithium ion batteries is investigated. The morphologies and electrochemical properties on the anode surface are also inspected by employing SEM

title: Parameter estimation of an electrochemistry based lithium ion battery model using a two step procedure and a parameter sensitivity analysis
abstract: Lithium ion batteries are indispensable in various applications owing to their high specific energy and long service life. Lithium ion battery models are used for investigating the behavior of the battery and enabling power control in applications. The Doyle Fuller Newman (DFN) model is a popular electrochemistry based model, which characterizes the dynamics in the battery through diffusions in solid and electrolyte and predicts current/voltage response. However, the DFN model contains a large number of parameters that need to be estimated to obtain an accurate battery model. In this paper, a computationally feasible two step estimation approach is proposed that only uses voltage and current measurements of the battery under consideration. In the two step procedure, the parameters are divided into 2 groups. The first group contains thermodynamic parameters, which are estimated using low current discharges, while the second group contains kinetic parameters, which are estimated using a well designed highly dynamic pulse (dis )charge current. A parameter sensitivity analysis is done to find a subset of parameters that can be reliably estimated using current and voltage measurements only. Experimental data are collected for 12 Ah nickel cobalt aluminum pouch lithium ion cell. The voltage predictions of the identified model are compared with several experimental data sets to validate the model. A root mean square error between model predictions and experimental data smaller than 16 mV is achieved.

title: Understanding the limitations of lithium ion batteries at high rates
abstract: Commercial lithium ion cells with different power: energy ratios were disassembled, to allow the electrochemical performance of their electrodes to be evaluated. Tests on coin cell half cells included rate tests (continuous and pulsed) resistance measurements, and extended pulse tests. Pulse power tests at high rates typically showed three limiting processes within a 10 s pulse; an instantaneous resistance increase, a solid state diffusion limited stage, and then electrolyte depletion/saturation. On anodes, the third process can also be lithium plating. Most of the cells were rated for a 10 C continuous discharge, and the cathode charging voltage at 10 C was around 4.2 V. For anodes, the maximum charge current to avoid a negative voltage was 3 5 C. Negative anode voltages do not necessarily mean that lithium plating has occurred. However, lithium deposits were observed on all the anodes after 5000 pulse sequences with 10 s pulses at 20 C.

title: Analysis of pulse and relaxation behavior in lithium ion batteries
abstract: A mathematical model of a lithium ion cell is used to analyze pulse and relaxation behavior in cells designed for hybrid electric vehicle propulsion. Predictions of cell voltage show good agreement with experimental results. Model results indicate the ohmic voltage loss in the positive electrode is the dominant contributor to cell overvoltage in the first instances of a pulse. The concentration overvoltage associated with the reduced lithium in the solid phase of the positive is of secondary importance through pulse duration, but dominates after current interruption. Effects of anisotropy in the particle diffusion coefficient are also studied. Heaviside mollification functions are utilized to describe the thermodynamic open circuit voltage of lithiated graphite, and the "pleated layer model" is extended to realize the phase behavior of primary particle aggregates during cell operation. The negative electrode contributes little to the cell overvoltage, and two phase behavior results in a reaction front within the electrode. No voltage relaxation is associated with the negative electrode, and after full relaxation, a stable composition gradient of lithium exists throughout the solid phase. Internal galvanic coupling removes the composition gradients in the positive electrode during relaxation.

title: Dynamics of a Blended Lithium Ion Battery Electrode During Galvanostatic Intermittent Titration Technique
abstract: A multi particle model is developed and applied to the data from galvanostatic intermittent titration technique (GITT) experiments with varying pulse currents and relaxation periods on a LiNi1/3Mn1/3Co1/3O2 LiMn2O4 (NMC LMO) blended lithium ion electrode. The good agreement between the simulated and experimental potential time curves shows that the model is applicable for all GITT conditions considered, but more accurate for the case of small current pulse discharges with long relaxation times. Analysis of the current contribution and the solid state surface concentration of each active component in the blended electrode shows a dynamic lithiation/delithiation interaction between the two components and between micron and submicron NMC particles during the relaxation periods in the GITT experiments. The interaction is attributed to the difference in the equilibrium potentials of the two components at any given stoichiometry which redistributes the lithium among LMO and NMC particles until a common equilibrium potential is reached.

title: Solid state diffusion limitations on pulse operation of a lithium ion cell for hybrid electric vehicles
abstract: A 1D model based on physical and electrochemical processes of a lithium ion cell is used to describe constant current and hybrid pulse power characterization (HPPC) data from a 6 Ah cell designed for hybrid electric vehicle (HEV) application. An approximate solution method for the diffusion of lithium ions within active material particles is formulated using the finite element method and implemented in the previously developed 1D electrochemical model as an explicit difference equation. Reaction current distribution and redistribution processes occurring during discharge and current interrupt, respectively, are driven by gradients in equilibrium potential that arise due to solid diffusion limitations. The model is extrapolated to predict voltage response at discharge rates up to 40 C where end of discharge is caused by negative electrode active material surface concentrations near depletion. Simple expressions are derived from an analytical solution to describe solid state diffusion limited current for short duration, high rate pulses.