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This work developed a novel experiment in order to determine the operational effects on a Lithium-ion battery (LIB) when a test resulting in non-catastrophic damage is performed. Accepted industry standards were used as a basis to develop a nail penetration test that would puncture a cell approximately halfway through during normal cycling at a rate of 1C, then allow the cell to continue cycling to determine how its operation was affected. The cells under test continued cycling after the punctures, showing that the experiment would be able to provide useful information on the topic. The experiment was found to be successful in simulating the operation of a cell in an abusive environment, such as those seen in electric vehicles and aerospace applications.<div><br></div><div>The results of these experiments showed that a sharp increase in temperature is observed immediately after the puncture, similar to cells that underwent tests with full penetrations. The temperatures then slowly decreased during the first few cycles after the puncture as the generated heat was dissipated through convection. The experiments also showed that it is possible for a LIB under test to continue operating for a short time after being punctured. However, the capacity and useful life of the cells were greatly reduced. The initial capacity of each cell decreased by approximately 11% after the initial impact, then continued decreasing at an accelerated rate during the ensuing cycling. The lifetime of the cells was also greatly reduced, with each cell reaching its end of life within approximately 15-75 cycles after the punctures. An analysis of the incremental capacity curves of the cells indicated that accelerated aging occurred due to both a loss of active material and a loss of lithium inventory. The information gained from the experiments gives insight into the operation of cells that experience abusive environments and will be useful in designing improved control systems, as well as promoting the development of more robust testing and safety standards for different types of cells.<br></div>

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Indiana University-Purdue University Indianapolis (IUPUI) / In the last years, lithium-ion batteries (LIBs) have become the most important energy storage system for consumer electronics, electric vehicles, and smart grids. The development of lithium-ion batteries (LIBs) based on current practice allows an energy density increase estimated at 10% per year. However, the required power for portable electronic devices is predicted to increase at a much faster rate, namely 20% per year. Similarly, the global electric vehicle battery capacity is expected to increase from around 170 GWh per year today to 1.5 TWh per year in 2030--this is an increase of 125% per year. Without a breakthrough in battery design technology, it will be difficult to keep up with the increasing energy demand. To that end, a design methodology to accelerate the LIB development is needed. This can be achieved through the integration of electro-chemical numerical simulations and machine learning algorithms. To help this cause, this study develops a design methodology and framework using Simcenter Battery Design Studio® (BDS) and Bayesian optimization for design and optimization of cylindrical cell type 18650. The materials of the cathode are Nickel-Cobalt-Aluminum (NCA)/Nickel-Manganese-Cobalt-Aluminum (NMCA), anode is graphite, and electrolyte is Lithium hexafluorophosphate (LiPF6). Bayesian optimization has emerged as a powerful gradient-free optimization methodology to solve optimization problems that involve the evaluation of expensive black-box functions. The black-box functions are simulations of the cyclic performance test in Simcenter Battery Design Studio. The physics model used for this study is based on full system model described by Fuller and Newman. It uses Butler-Volmer Equation for ion-transportation across an interface and solvent diffusion model (Ploehn Model) for Aging of Lithium-Ion Battery Cells. The BDS model considers effects of SEI, cell electrode and microstructure dimensions, and charge-discharge rates to simulate battery degradation. Two objectives are optimized: maximization of the specific energy and minimization of the capacity fade. We perform global sensitivity analysis and see that thickness and porosity of the coating of the LIB electrodes that affect the objective functions the most. As such the design variables selected for this study are thickness and porosity of the electrodes. The thickness is restricted to vary from 22microns to 240microns and the porosity varies from 0.22 to 0.54. Two case studies are carried out using the above-mentioned objective functions and parameters. In the first study, cycling tests of 18650 NCA cathode Li-ion cells are simulated. The cells are charged and discharged using a constant 0.2C rate for 500 cycles. In the second case study a cathode active material more relevant to the electric vehicle industry, Nickel-Manganese-Cobalt-Aluminum (NMCA), is used. Here, the cells are cycled for 5 different charge-discharge scenarios to replicate charge-discharge scenario that an EVs battery module experiences. The results show that the design and optimization methodology can identify cells to satisfy the design objective that extend and improve the pareto front outside the original sampling plan for several practical charge-discharge scenarios which maximize energy density and minimize capacity fade.

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Det överhängande behovet av att minska utsläppen av växthusgaser för att uppfylla Parisavtalet har väckt ett ökat intresse för elektrifiering som en strategi för att mildra klimatförändringarna. Litiumjonbatterier spelar en central roll vid elektrifiering och har framträtt som det primära alternativet för batteridrivna elfordon. Batteriernas livstidsprestanda är dock en avgörande faktor för att bestämma deras kostnad och miljömässiga hållbarhet. Även om snabbladdning är ett gångbart alternativ för de kunder som vill maximera drifttiden så leder laddning vid höga strömmar till förhöjd åldring genom nedbrytning av elektrodmaterialet och elektrolyten. Nyligen genomförda studier har visat att pulsade laddningscykler kan förlänga livslängden för litiumjonbatterier. Mot bakgrund av detta har denna studie genomförts för att undersöka effekterna av pulsad laddning på bibehållande av kapacitet samt inre motstånd hos litiumjonbatterier. Cylindriska NMC-celler har cyklats med laddningsprofilen PPC-CV (Positive Pulsed Current-Constant Voltage) och deras prestanda har jämförts med motsvarande hos konventionell konstant ström-konstant spänning-laddning (CC-CV). En ny metod utvecklades och implementerades för att utföra en pulsad laddningsprofil inom ett definierat SoC-fönster (State-of-Charge). Testobjekten cyklades kontinuerligt under intervaller om 4 veckor med avbrott för standardiserade referensprestandatester (RPT) för att beräkna standardkapaciteten och det inre motståndet. Därutöver utfördes inkrementell kapacitetsanalys (ICA) och elektrokemisk impedansspektroskopi (EIS) för att utöka analysen. Enligt resultat visar de celler som cyklats med PPC-CV-profilen liknande eller något minskad kapacitetsminskning samt en lägre ökning av internt motstånd efter ungefär 700 ekvivalenta cykler. 0,01-Hz PPC-CV-profilen uppvisade en kapacitetsminskning på 3,65%, 1-Hz PPC-CV-profilen en på 3,75%, 100-Hz PPC-CV- profilen en på 4,06% och CC-CV-profilen en på 4,05%. De interna resistanserna förblev lägre än BOL-mätningarna i PPC-CV-testfallen, medan CC-CV-läget visar en snabbare ökning av internt motstånd. Batteriets hälsotillstånd (SoH) hade dock bara nått 95% under denna testfas, vilket innebär att ytterligare studier krävs för att dra definitiva slutsatser om pulsladdningens effekt på batteriets livslängd. För att ytterligare förstå effekten av pulsade laddningsprofiler på livslängden hos litiumjonbatterier kan textmatrisen utökas till ett bredare spektrum av testförhållanden, såsom temperatur, strömamplitud, arbetscykel och SoC-fönster. / The urgent need to reduce greenhouse gas emissions in order to comply with the Paris Agreement has sparked an increased interest in electrification as a strategy to mitigate climate change. Li-ion batteries play a crucial role in electrification, and have emerged as the primary option for battery electric vehicles. However, their lifetime performance is a critical factor in determining their cost and environmental sustainability. Although fast charging presents a viable option for customers wishing to maximize operational time, charging at high currents accelerate aging through degradation of the electrode material and the electrolyte. Recent studies have found that pulse charging protocols can extend the cycle life of Li-ion batteries. In light of this, this study has been conducted to investigate the effects of pulse charging on the capacity retention and internal resistance of Li-ion batteries. Prismatic NMC Li-ion battery cells were cycled using the Positive Pulsed Current-Constant Voltage (PPC-CV) charging mode, and their performance has been compared to that of conventional Constant Current-Constant Voltage (CC-CV) charging. A novel method was developed and implemented to execute a pulse charging profile within a defined State-of-Charge (SoC) window. The test objects were continuously cycled over intervals of 4 weeks with interruptions for standardized Reference Performance Tests (RPTs) to calculate the stan- dard capacity and internal resistance. In addition, Incremental Capacity Analysis (ICA) and Electrochemical Impedance Spectroscopy (EIS) were performed to ex- tend the analysis. According to results, cells cycled using the PPC-CV mode show similar or slightly reduced capacity fade and a lower increase in internal resistance after roughly 700 equivalent cycles. The 0.01-Hz PPC-CV mode exhibited a capacity fade of 3.65%, the 1-Hz PPC-CV mode 3.75%, the 100-Hz PPC-CV mode 4.06% and the CC-CV mode 4.05%. Internal resistances remained lower than the beginning of life measurements in the PPC-CV test cases, while the CC-CV mode shows a quicker increase in internal resistance. However, the battery State-of-Health (SoH) had only reached 95% during this testing phase, requiring further study to draw definitive conclusions regarding the impact of pulse charging on battery life performance. To further understand the impact of pulsed charging modes on Li-ion battery life performance, the text matrix may be extended to incorporate a broader range of test conditions, such as temperature, current amplitude, duty cycle and State-of-Charge (SoC) window.