Lithium Nickel Cobalt Aluminum Research Articles

A routine for the determination of the microstructure of stacking-faulted nickel cobalt aluminium hydroxide precursors for lithium nickel cobalt aluminium oxide battery materials.

The microstructures of six stacking-faulted industrially produced cobalt- and aluminium-bearing nickel layered double hydroxide (LDH) samples that are used as precursors for Li(Ni1-x-yCo x Al y )O2 battery materials were investigated. Shifts from the brucite-type (AγB)□(AγB)□ stacking pattern to the CdCl2-type (AγB)□(CβA)□(BαC)□ and the CrOOH-type (BγA)□(AβC)□(CαB)□ stacking order, as well as random intercalation of water molecules and carbonate ions, were found to be the main features of the microstructures. A recursive routine for generating and averaging supercells of stacking-faulted layered substances implemented in the TOPAS software was used to calculate diffraction patterns of the LDH phases as a function of the degree of faulting and to refine them against the measured diffraction data. The microstructures of the precursor materials were described by a model containing three parameters: transition probabilities for generating CdCl2-type and CrOOH-type faults and a transition probability for the random intercalation of water/carbonate layers. Automated series of simulations and refinements were performed, in which the transition probabilities were modified incrementally and thus the microstructures optimized by a grid search. All samples were found to exhibit the same fraction of CdCl2-type and CrOOH-type stacking faults, which indicates that they have identical Ni, Co and Al contents. Different degrees of interstratification faulting were determined, which could be correlated to different heights of intercalation-water-related mass-loss steps in the thermal analyses.

Using In-Situ Methods to Characterize Phase Changes in Charged Lithium Nickel Cobalt Aluminum Oxide Cathode Materials

Using In-Situ Methods to Characterize Phase Changes in Charged Lithium Nickel Cobalt Aluminum Oxide Cathode Materials

Lattice doping regulated interfacial reactions in cathode for enhanced cycling stability

Interfacial reactions between electrode and electrolyte are critical, either beneficial or detrimental, for the performance of rechargeable batteries. The general approaches of controlling interfacial reactions are either applying a coating layer on cathode or modifying the electrolyte chemistry. Here we demonstrate an approach of modification of interfacial reactions through dilute lattice doping for enhanced battery properties. Using atomic level imaging, spectroscopic analysis and density functional theory calculation, we reveal aluminum dopants in lithium nickel cobalt aluminum oxide are partially dissolved in the bulk lattice with a tendency of enrichment near the primary particle surface and partially exist as aluminum oxide nano-islands that are epitaxially dressed on the primary particle surface. The aluminum concentrated surface lowers transition metal redox energy level and consequently promotes the formation of a stable cathode-electrolyte interphase. The present observations demonstrate a general principle as how the trace dopants modify the solid-liquid interfacial reactions for enhanced performance.

High-Performance Li-Ion Batteries Using Nickel-Rich Lithium Nickel Cobalt Aluminium Oxide-Nanocarbon Core-Shell Cathode: In Operando X-ray Diffraction.

Nickel-rich layered, mixed lithium transition-metal oxides have been pursued as a propitious cathode material for the future-generation lithium-ion batteries due to their high energy density and low cost. Nevertheless, acute side reactions between Ni4+ and carbonate electrolyte lead to poor cycling as well as rate performance, which limits their large-scale applications. Here, core-shell like LiNi0.8Co0.15Al0.05O2 (NCA)-carbon composite synthesized by a solvent-free mechanofusion method is reported to solve this issue. Such a core-shell structure exhibits a splendid rate as well as stable cycling when compared to the physically blended NCA. In operando X-ray diffraction studies show that both materials experience anisotropic structural change, i.e., stacking c-axis undergoes a gradual expansion followed by an abrupt shrinkage; meanwhile, the a-axis contracts during the charging process and vice versa. Interestingly, the core-shell material displays a significantly high reversible capacity of 91% in the formation cycle at 0.1C and a retention of 84% at 0.5C after 250 cycles, whereas pristine NCA retains 71%. The robust mechanical force assisted dry coating obtained by the mechanofusion method shows improved electrochemical performance and demonstrates its practical feasibility.

Development of gel polymer electrolyte based on LiTFSI and EMIMFSI for application in rechargeable lithium metal battery with GO-LFP and NCA cathodes

In this paper, we report the effect of ionic liquid 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EMIMFSI) on polymer poly(ethylene oxide) (PEO) and salt lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) electrolyte system. The glass transition temperature and degree of crystallinity decreased with an increasing amount of EMIMFSI resulting in an increase in the ionic conductivity. The highest room temperature ionic conductivity and Li+ transference number are observed for PEO + 20 wt% LiTFSI + 10 wt% EMIMFSI. These prepared gel polymer electrolytes (GPEs) are thermally and electrochemically stable enough for battery application. Two different cells with graphene oxide-doped lithium iron phosphate, LiFePO4 (GO-LFP) and lithium nickel cobalt aluminum oxide, LiNi0.80Co0.15Al0.05O2 (NCA) cathodes were tested with prepared GPEs. GO-LFP showed more predictable and consistent nature of capacity fading and good discharge capacity. However, NCA showed higher discharge capacity, better cyclic performance, lower capacity fading, and better performance at high C rates.

Comparing Operando XRD and Dems to Investigate Metal-Substituted LiNiO2

LiNiO₂ (LNO) has been introduced as cathode active material for Li‐ion batteries in 1990 [1]. After years of intensive research, it emerged that several instability issues plague the material, so that it was abandoned in favor of isostructural metal‐substituted compounds called NCA (for lithium nickel cobalt aluminum oxide) and NCM (lithium nickel cobalt manganese oxide). These sacrifice a certain amount of specific energy in exchange for stability, durability and safety [2]. With few exceptions, NCA and NCM are nowadays the industrial standard when it comes to automotive applications. However, the continuous push towards electric cars with longer driving range is synonym, for these compounds, with increasing the nickel content (which is already beyond 80%), eventually leading back again to LiNiO₂. For this reason, we synthesized a series of LiNiO2 samples, where Ni is substituted by low amounts of other elements (< 5%). We implement a characterization strategy based on operando XRD, differential electrochemical mass spectrometry (DEMS) and ex situ TEM, enabling us to track, in real time upon battery charge and discharge (i.e., as Li is extracted/inserted from/into LNO, respectively), the evolution of the material´s crystal structure, the transformation of its surface and the evolution of gaseous products. We place particular emphasis on the behavior of LNO at high state of charge (> 4.1 V), where the transition between the hexagonal phases H2 and H3, whose unit cell volume is very different, induces significant mechanical strain in the material [3]. The H2 and H3 phases are also thermodynamically metastable [4] and decompose towards off-stoichiometric Li1-zNi1+zO2, with release of O2[5], a reaction we can observe by DEMS and TEM. With this combined strategy, we aim at understanding which element, if any, can sufficiently stabilize LNO in the charged state. Bibliography Dahn, J.R., U. Vonsacken, and C.A. Michal, Structure and Electrochemistry of Li1+-yNiO2 and a New Li2NiO2 Phase with the Ni(OH)2 Structure. Solid State Ionics, 1990. 44(1-2): p. 87-97. Myung, S.-T., et al., Nickel-Rich Layered Cathode Materials for Automotive Lithium-Ion Batteries: Achievements and Perspectives. ACS Energy Letters, 2017. 2(1): p. 196-223. Yoon, C.S., et al., Structural Stability of LiNiO2 Cycled above 4.2 V. ACS Energy Letters, 2017. 2(5): p. 1150-1155. Das, H., et al., First-Principles Simulation of the (Li–Ni–Vacancy)O Phase Diagram and Its Relevance for the Surface Phases in Ni-Rich Li-Ion Cathode Materials. Chemistry of Materials, 2017. 29(18): p. 7840-7851. Bianchini, M., et al., There and back again - The journey of LiNiO2 as cathode active material. Angew Chem Int Ed Engl, 2018: p. 10.1002/anie.201812472.

Optimized PV-coupled battery systems for combining applications: Impact of battery technology and geography

Interest in residential batteries to supply photovoltaic (PV) electricity on demand is increasing, however they are not profitable yet. Combining applications has been suggested as a way to increase their attractiveness, but the extent to which this can be achieved, as well as how the different value propositions may affect the optimal battery technology, remain unclear. In this study, we develop an open-source optimization framework to determine the best-suited battery technology depending on the size and the applications combined, including PV self-consumption, demand load-shifting, demand peak shaving and avoidance of PV curtailment. Moreover, we evaluate the impact of the annual demand and electricity prices by applying our method to representative dwellings in Geneva (Switzerland) and Austin (United States). Our results indicate that the combination of applications help batteries to become close to break-even by improving the net present value by up to 66% when compared with batteries performing PV self-consumption only. Interestingly, we find that the best-suited battery technology in Austin is lithium nickel cobalt aluminum oxide (NCA) as for Geneva lithium nickel manganese cobalt oxide (NMC) batteries reach in average a higher net present value than NCA-based batteries. However, NCA-based batteries could be a more promising alternative when applications are combined.

A Fast Metals Recovery Method for the Synthesis of Lithium Nickel Cobalt Aluminum Oxide Material from Cathode Waste

An approach for a fast recycling process for Lithium Nickel Cobalt Aluminum Oxide (NCA) cathode scrap material without the presence of a reducing agent was proposed. The combination of metal leaching using strong acids (HCl, H2SO4, HNO3) and mixed metal hydroxide co-precipitation followed by heat treatment was investigated to resynthesize NCA. The most efficient leaching with a high solid loading rate (100 g/L) was obtained using HCl, resulting in Ni, Co, and Al leaching efficiencies of 99.8%, 95.6%, and 99.5%, respectively. The recycled NCA (RNCA) was successfully synthesized and in good agreement with JCPDS Card #87-1562. The highly crystalline RNCA presents the highest specific discharge capacity of a full cell (RNCA vs. Graphite) of 124.2 mAh/g with capacity retention of 96% after 40 cycles. This result is comparable with commercial NCA. Overall, this approach is faster than that in the previous study, resulting in more efficient and facile treatment of the recycling process for NCA waste and providing 35 times faster processing.

Life cycle inventories of the commonly used materials for lithium-ion batteries in China

With the fast growing of the electric vehicle (EV) market and soaring production of the EV lithium-ion batteries (LiBs) in China, more and more life cycle assessment (LCA) studies has been focused on their impacts towards resources, energy and environment in recent years. As the indispensable background data, the life cycle inventories (LCIs) of the cradle-to-gate stage of the commonly used materials for the production of LiBs play an important role in the related LCA studies, since their accuracy and reliability can affect the results and conclusions greatly. However, LCIs of the LiB materials produced in China are in scarcity nowadays, which has become an obstacle for the further understanding of the eco-performances of EVs and LiBs. In this study, a general unit-process model was established firstly, and then a variety of foreground data were collected from the representative manufacturers of LiB materials in China. With a sequential calculation procedure carried out step by step, the targeted LCIs of the materials were obtained, along with the corresponding 95% confidential intervals through Monte-Carlo simulations. According to the inventories analysis, it was found that among the materials studied, the polyethylene separator made by wet drawing process, lithium hexafluorophosphate, carbon nanotubes, lithium nickel manganese cobalt oxide and nickel cobalt aluminum are with relatively higher primary energy demands and greenhouse gas emissions in their cradle-to-gate stage. Besides, among the cathode materials studied, lithium iron phosphate consumes the lowest non renewable mineral resources. In addition, through a comparison with GREET, we found that the energy consumptions and greenhouse gas emissions of the LiB materials in this study are significantly higher than that drawn from GREET. This will lead to 62–91% more greenhouse gas emissions from materials made in China than those in the United States in order to produce LiB cells of the same capacity. However, it was also found the discrepancies may be stemmed from many difference in the processes of modeling and data acquisition between this study and the supportive studies for GREET.

Examining different recycling processes for lithium-ion batteries

Finding scalable lithium-ion battery recycling processes is important as gigawatt hours of batteries are deployed in electric vehicles. Governing bodies have taken notice and have begun to enact recycling targets. While several battery recycling processes exist, the greenhouse gas emissions impacts and economic prospects of these processes differ, and could vary by specific battery chemistry. Here we use an attributional life-cycle analysis, and process-based cost models, to examine the greenhouse gas emissions, energy inputs and costs associated with producing and recycling lithium-ion cells with three common cathode chemistries: lithium nickel manganese cobalt oxide (NMC-622), lithium nickel cobalt aluminium oxide and lithium iron phosphate. We compare three recycling processes: pyrometallurgical and hydrometallurgical recycling processes, which reduce cells to elemental products, and direct cathode recycling, which recovers and reconditions ceramic powder cathode material for use in subsequent batteries—retaining a substantial fraction of the energy embodied in the material from their primal manufacturing process. While pyrometallurgical and hydrometallurgical processes do not significantly reduce life-cycle greenhouse gas emissions, direct cathode recycling has the potential to reduce emissions and be economically competitive. Recycling policies should incentivize battery collection and emissions reductions through energetically efficient recycling processes. Various battery recycling processes exist, but the related environmental and economic implications can vary by specific battery chemistry. This study examines the greenhouse gas emissions, energy inputs and costs associated with producing and recycling lithium-ion cells with different cathode chemistries.

The Life Cycle of Energy Consumption and Greenhouse Gas Emissions from Critical Minerals Recycling: Case of Lithium-ion Batteries

Sometimes the applications of lithium-ion batteries (LIBs) are labeled as “zero emissions”. However, the emissions generated in the procurement and production stage of supply chain is not considered. Battery production is one of the main contributors to emitting greenhouse gas (GHG) emissions through electric vehicle (EV) manufacturing. In this case, recycling of LIBs is recommended to reduce energy consumption and mitigate GHG emissions as well as result in considerable natural resource saving compared to landfill. Also, accelerating production of LIBs in the line of clean-energy technologies has led to a sharply increasing criticality of minerals such as lithium (Li), cobalt (Co) and manganese (Mn). The spent LIBs could consider the secondary source of these minerals. The environmental sustainable way of recovering critical minerals from this waste is very important. Therefore, the primary aim of this paper is to answer the question if recycling of LIBs to recover the mentioned critical minerals is an environmentally sustainable option. To address this question, two aspects are analyzed: energy consumption and GHG emissions. These aspects were analyzed through a dynamic simulation model based on the principles of the system dynamics methodology. We provide an environmental analysis of recycling of critical minerals from spent LIBs including LMO, lithium manganese oxide; LCO, lithium cobalt oxide; LFP, lithium iron phosphate; NMC, lithium nickel manganese cobalt oxide; and LiNCA, Lithium nickel cobalt aluminum oxide. The results show that recycling of LIBs helps to prevent the shortage of critical minerals from a mass flow perspective. However, from an environmental perspective, the current technology is not recommended to recover lithium from LIBs which leads 38-45% more consumption of energy and 16-20% higher air emissions than its primary production.

Italian Experience on Electrical Storage Ageing for Primary Frequency Regulation

The paper describes the results of different types of ageing tests performed by Terna (the Italian Transmission System Operator) applied to several electrochemical technologies, namely lithium-based and sodium-nickel chloride-based technologies. In particular, the tested lithium-based technologies exploit a graphite-based anode and the following cathode electrochemistries: lithium iron phosphate, lithium nickel cobalt aluminium, lithium nickel cobalt manganese, and lithium titanate. These tests have been performed in the storage labs located in Sardinia (Codrongianos) and Sicily (Ciminna). The aim of the storage labs is intended to give the electrical grid ancillary services, for example, primary frequency regulation, secondary frequency regulation, voltage regulation, synthetic rotational inertia provision, and many more. For the primary frequency regulation service, the ageing of the batteries is difficult to foresee as the ageing tests are not standardized. The authors proposed some novel cycle types, which showed that, in several cases, the frequency regulation cycle ages the batteries much more than the standard cycle. The standard cycle definition has been adopted in the paper to identify a battery cycle test that was carried out to uniformly compare and rank the different technologies. Moreover, sodium-nickel chloride batteries are unaffected by the types of cycle and have a negligible ageing. In addition, lithium manganese oxide and lithium titanate batteries show very good behaviour with a slight degradation of the dischargeable energy, irrespectively of the type of cycle. Inversely, lithium nickel cobalt aluminium technology shows a considerable ageing and a strong dependence on the cycle types. Even if the theoretical explanations of such aging behaviours need time to be understood and expounded, the authors are convinced that the scientific community should become aware of these experimental results.

Going Green By Going Blue: Recycling Li-Ion Batteries By Extracting Cobalt and Nickel Using Deep Eutectic Solvents

With the ever-imminent electrification of the transportation sector, the growth of renewable energy systems requiring better storage units, and the desire for smaller, faster, and smarter consumer electronics, the demand for Li-ion batteries (LIBs) to power the needs of the world is higher than ever. Over the past ten years, while battery prices have plummeted by a factor of four going from about $800/kWh to now $200/kWh for current chemistries1,2, costs of valuable metals within the batteries themselves have surged—notably in the most expensive part of the battery, the cathode, commonly made of cobalt-rich compounds. Cobalt in particular poses not only an economical burden, but a social and environmental one as well, instigating efforts to reduce the reliance on the conflict mineral while still maintaining high performance. Such efforts have led to the development of chemistries using other metals such as manganese and nickel, and has also pushed researchers to pursue more battery recycling options. In this work, a process to extract and reuse cobalt from LIBs containing lithium cobalt (III) oxide (LCO) has been developed using deep eutectic solvents (DESs), a “green” alternative to traditionally toxic solvents. DESs are solutions of two or more Lewis or Brønsted acids and bases that exhibit a deeply depressed freezing point; they can additionally made from cheap and potentially renewable materials3. Nickel metal was also tested in these eutectics, as the nickel manganese cobalt oxide (NMC) and lithium nickel cobalt aluminum oxide (NCA) batteries are projected to play a more prominent role in the future of Li-ion battery technology. The objective is to sustainably recycle these metals from LIBs and then repurpose it in other energy applications. In dissolution experiments simulating the extraction of cobalt from the traditional LIBs, LCO powder was mixed directly with the DES under heat, resulting in a vibrant aqua-blue solution indicating the presence of Co2+ ions. The solubilized metal was filtered and subsequently electrodeposited. Inductively coupled plasma optical emission spectrometry results showed record solubility values for a metal oxide in the presence of a DES. Similarly, experiments done using the nickel-based compounds showed promise for further development, leading to the eventual testing on spent Li-ion cathodes as well. Usage of the recovered metal in a supercapacitor and a new LIB cell demonstrates that such recycling can indeed apply sustainable means to a sustainable end—or rather a new beginning. References Opitz, A. et al., Can Li-Ion batteries be the panacea for automotive applications? Renewable and Sustainable Energy Reviews 2017, 68 (1), 685-692.“After electric cars, what more will it take for batteries to change the face of energy?” The Economist [London] 12 Aug. 2017. Electronic.Smith, E., et al. Deep Eutectic Solvents (DESs) and Their Applications. Rev. 2014, 114, 11060-11082.

Iron Fluoride–Carbon Nanocomposite Nanofibers as Free‐Standing Cathodes for High‐Energy Lithium Batteries

AbstractThe development of low‐cost, high‐energy cathodes from nontoxic, broadly available resources is a big challenge for the next‐generation rechargeable lithium or lithium‐ion batteries. As a promising alternative to traditional intercalation‐type chemistries, conversion‐type metal fluorides offer much higher theoretical capacity and energy density than conventional cathodes. Unfortunately, these still suffer from irreversible structural degradation and rapid capacity fading upon cycling. To address these challenges, here a versatile and effective strategy is harnessed for the development of metal fluoride–carbon (C) nanocomposite nanofibers as flexible, free‐standing cathodes. By taking iron trifluoride (FeF3) as a successful example, assembled FeF3–C/Li cells with a high reversible FeF3 capacity of 550 mAh g−1 at 100 mA g−1 (three times that of traditional cathodes, such as lithium cobalt oxide, lithium nickel cobalt aluminum oxide, and lithium nickel cobalt manganese oxide) and excellent stability (400+ cycles with little‐to‐no degradation) are demonstrated. The promising characteristics can be attributed to the nanoconfinement of FeF3 nanoparticles, which minimizes the segregation of Fe and LiF upon cycling, the robustness of the electrically conductive C network and the prevention of undesirable reactions between the active material and the liquid electrolyte using the composite design and electrolyte selection.

Improved cycle performance of nitrogen and phosphorus co-doped carbon coatings on lithium nickel cobalt aluminum oxide battery material

Nitrogen–phosphorus co-doped nanoscale carbon coating (N/P–C) was constructed on the surface of LiNi0.8Co0.15Al0.05O2 (NCA). The coated material showed a shell–core structure, the core layer was NCA, the shell layer was N/P–C, and the coating was evenly distributed on the surface of the material. The coating improves electron transport path in the structure of NCA, increases conductivity, protects the electrode material, suppresses dissolution of the metal ions and improves stability. In this experiment, aniline (ani) was used as the carbon source and the nitrogen source, and phytic acid was used as the carbon source and the phosphorus source. They were mixed at a mass ratio of m (NCA)/m (C) = 100:0.5, 100:1.0 and 100:2.0, respectively, and then annealed to form a uniform coating. By comparison, it can be concluded that the coating has the best electrochemical performance when the coating mass fraction is 1.0%. At the current density of 1 C, the capacity retention rate was 90.7% after 200 cycles, higher than uncoated material (70%).

Experimental investigation of the thermal and cycling behavior of a lithium titanate-based lithium-ion pouch cell

Lithium-ion pouch cells with lithium titanate (Li4Ti5O12, LTO) anode and lithium nickel cobalt aluminum oxide (LiNi0.8Co0.15Al0.05O2, NCA) cathode were investigated experimentally with respect to their electrical (0.1C…4C), thermal (5 °C…50 °C) and long-time cycling behavior. The 16 Ah cell exhibits an asymmetric charge/discharge behavior which leads to a strong capacity-rate effect, as well as a significantly temperature-dependent capacity (0.37 Ah ∙ K−1) which expresses as additional high-temperature feature in the differential voltage plot. The cell was cycled for 10,000 cycles inbetween the nominal voltage limits (1.7–2.7 V) with a symmetric 4C constant-current charge/discharge protocol, corresponding to approx. 3400 equivalent full cycles. A small (0.192 mΩ/1000 cycles) but continuous increase of internal resistance was observed. Using electrochemical impedance spectroscopy (EIS), this could be identified to be caused by the NCA cathode, while the LTO anode showed only minor changes during cycling. The temperature-corrected capacity during 4C cycling exhibited a decrease of 1.28%/1000 cycles. The 1C discharge capacity faded by only 4.0% for CC discharge and 2.3% for CCCV discharge after 10,000 cycles. The cell thus exhibits very good internal-resistance stability and excellent capacity retention even under harsh (4C continuous) cycling, demonstrating the excellent stability of LTO as anode material.

Comparison of off-grid power supply systems using lead-acid and lithium-ion batteries

Solar home systems (SHS) and solar photovoltaic village power supply systems can play an important role in the supply of electrical energy to off-grid areas. This paper presents a comparison of solar home systems and village power supply systems using two different types of battery technologies, namely lithium nickel cobalt aluminum oxide (NCA) and lead-acid (Pb) batteries. The developed models were implemented in Matlab/Simulink where solar radiation, temperature and electrical load data from Dodoma, the capital of Tanzania were used as model inputs.Two topologies were analyzed for SHS: A system which is directly coupled to the battery and another system which uses a Maximum Power Point Tracker (MPPT) charge controller. The main idea of analyzing these two topologies was to find an affordable solution for off-grid population, but at the same time the selected topology should have the ability of extracting maximum output from the PV panel.Since most of the off-grid settlements in Tanzania today use SHS with lead-acid batteries as storage, analysis was carried out for SHS with lead-acid batteries and SHS with lithium-ion batteries by simulating and optimizing the systems for 20 years. The levelized cost of electricity (LCOE) for both storage systems was compared and it was found that the SHS with lithium-ion (NCA) battery generally had a lower LCOE compared to the SHS with lead-acid battery. This is mainly due to both the longer life time of NCA batteries and the reduction of the price of NCA batteries as a result of significantly increasing global production scales.For the case of solar photovoltaic village power supply systems, an energy management system was implemented to optimize power flows in a hybrid storage system containing both lead-acid and lithium-ion batteries. Optimization of this “hybrid” system led to a selection of both types of batteries with small capacity of lead-acid battery (0.24kW h) compared to NCA battery (1.44kW h) backed up with diesel generator. Further analysis was done regarding the benefits of village power supply systems over individual SHS, and it was found that the LCOE for solar PV village power supply systems was lower than the LCOE for single SHS.

Optimal Experimental Design for Parameterization of an Electrochemical Lithium-Ion Battery Model

We consider the problem of optimally designing an excitation input for parameter identification of an electrochemical Li-ion battery model. The conventional approach to performing parameter identification uses standard test cycles. In contrast, we optimally design the input trajectory to maximize parameter identifiability in the sense of Fisher information. Specifically, we derive sensitivity equations for the electrochemical model. This approach enables parameter sensitivity analysis and optimal parameter fitting via gradient-based algorithms. This paper presents a general systematic approach to identify the electrochemical parameters in a non-invasive way. First, we group parameters into two sets: (i) equilibrium parameters, and (ii) dynamical parameters. We also divide the dynamical parameters into subsets by calculating orthogonalized sensitivity, which mitigates linear dependence between parameters. A large number of input profiles have been devised to constitute an input library. Then, the optimal inputs are selected from the input library to maximize the Fisher information, via convex programming. Using this framework a number of relevant experiments are obtained to parameterize. To validate our approach experimentally, we consider a 18650 Lithium nickel cobalt aluminum oxide battery. Compared to the conventional approach, our proposal achieves lower voltage RMSE across all experimental testing cycles.

Factors Limiting Li+ Charge Transfer Kinetics in Li-Ion Batteries

Understanding the factors limiting Li+ charge transfer kinetics in Li-ion batteries is essential in improving the rate performance, especially at lower temperatures. The Li+ charge transfer process involved in the lithium intercalation of graphite anode includes the step of de-solvation of the solvated Li+ in the liquid electrolyte and the step of transport of Li+ in the preformed solid electrolyte interphase (SEI) on electrodes until the Li+ accepts an electron at the electrode and becomes a Li in the electrode. Whether the de-solvation process or the Li+ transport through the SEI is a limiting step depends on the nature of the interphases at the electrode and electrolyte interfaces. Several examples involving the electrode materials such as graphite, lithium titanate (LTO), lithium iron phosphate (LFP), lithium nickel cobalt aluminum oxide (NCA) and solid Li+ conductor such as lithium lanthanum titanate or Li-Al-Ti-phosphate are reviewed and discussed to clarify the conditions at which either the de-solvation or the transport of Li+ in SEI is dominating and how the electrolyte components affect the activation energy of Li+ charge transfer kinetics. How the electrolyte additives impact the Li+ charge transfer kinetics at both the anode and the cathode has been examined at the same time in 3-electrode full cells. The resulting impact on Li+ charge transfer resistance, Rct, and activation energy, Ea, at both electrodes are reported and discussed.

Aging of ceramic coated graphitic negative and NCA positive electrodes in commercial lithium-ion battery cells – An ex-situ study of different states of health for identification and quantification of aging influencing parameters

An ex-situ aging study was carried out using commercial lithium-ion battery cells with lithium nickel cobalt aluminum oxide (NCA) positive electrodes and aluminum oxide (Al2O3) surface coated graphitic negative electrodes at various states of health (SOHs): 100%, 80% and 10%. The lowest SOH-value was chosen in order to understand and to quantify the aging mechanisms in lithium-ion batteries. The electrodes were analyzed by different techniques: SEM/EDX, ICP-OES, XPS, XRD and BET. Significant changes in positive and negative morphology, elemental composition and surface area were observed depending on the SOH value and the positioning of the sample in the jelly roll. We discuss in the context of well-known aging mechanisms further aging effects. The cell capacity is limited by the amount of immobilized lithium. Lithium loss of the positive electrode is directly correlated with a lithium increase of the negative electrode. The linearity of the lithium content in the electrodes is a function of SOH over the whole SOH-range while the lithium content in the electrodes is an exponential function of the porosity. Another aging effect is the degradation of the ceramic coating on the graphite and the migration of the ceramic coating from the surface of the negative electrode to the bulk.