Cost Of Lithium-ion Batteries Research Articles

(Invited) Delineating the Intricacies Involved in the Synthesis of Cobalt-Free High-Nickel Layered Oxide Cathodes for Lithium-Ion Batteries

Improving the energy density and cost of lithium-ion batteries (LIBs) requires a rational compositional design of layered oxide LiNi1-x-yMnxCoyO2 (NMC) cathodes. The prevailing trend is to increase the nickel content in the cathode to maximize energy density, but high-nickel NMC generally suffers from surface and bulk instabilities that shorten battery life. Dopants, such as cobalt, can help mitigate these issues, but its supply shortage issue prohibits its usage especially in the massive electric vehicle market. Our recent finding suggests that a combination of manganese and aluminum in LiNi0.9Mn0.05Al0.05O2 (NMA-90) promotes attractive energy density, cycle life, rate capability and thermal stability, proving that cobalt can be eliminated in high-nickel cathodes. Post-mortem analysis further reveals that the Mn-Al combination provides synergistic improvements in structural and surface stabilities compared to LiNi0.9Mn0.05Co0.05O2 (NMC-90) and LiNi0.9Co0.05Al0.05O2 (NCA-90). A thorough understanding of the relationship between the synthesis condition and optimal materials properties of NMA-90 is necessary to enable its large-scale deployment. We will present findings from the calcination and coprecipitation study of several cobalt-free cathodes to elucidate this relationship. It is revealed that the cycle stability of LiNi0.9Mn0.1O2 (NM-90) is not dependent on Li/Ni mixing or primary particle size, but is dependent on the calcination temperature. Incorporating Al into NM-90 during coprecipitation reactions cause high internal porosity in the hydroxide precursor, which impacts the final morphology of the calcined cathodes and thus their electrochemical stability. The ongoing work in our lab provides insight on the synthesis sensitivity of NMA and strategizes methods to control its electrochemical properties.

Sepion Technologies

The transition to electric vehicles is not happening fast enough for Pete Frischmann, cofounder and CEO of the California-based start-up Sepion Technologies. “The shift from combustion engine vehicles to electric vehicles is arguably the largest change in how raw materials, especially metals, move around the globe in the past century,” he says. “I don’t think people fully appreciate how massive the shift is and how important establishing new mines and supply chains is for combating climate change.” The cost of lithium-ion batteries is a key hurdle to making electric vehicles more affordable and hence more ubiquitous. The battery pack accounts for up to a third of the cost of an electric vehicle, according to Frischmann. Sepion reckons it can change the game by helping manufacturers switch from incumbent lithium-ion batteries to the firm’s lithium-metal battery approach. The start-up is promising automakers that its technology will cut cost per kilowatt-hour by

Tuning interface stability of nickel-rich LiNi0.9Co0.05Mn0.05O2 cathode via a novel bis(vinylsulphonyl)methane additive

By increasing the nickle content in LiNi x Mn y Co 1-x-y O 2 cathodes, the energy density and cost of lithium ion batteries (LIBs) could be further optimized. However, the structural/interfacial instability of nickel-rich cathode extremely challenges its cycling life. Here, we demonstrate a novel electrolyte additive bis(vinylsulphonyl)methane (BVSM) to enhance the cycling stability and rate capability of LiNi 0.9 Co 0.05 Mn 0.05 O 2 (NCM90) cathode. Detailed surface characterizations prove the construction of a robust sulfur-incorporated and inorganic fluorides-enriched cathode-electrolyte interphase (CEI) film on the NCM90 surface. This BVSM-derived CEI contributes to a more reliable NCM90 cathode with suppressed interfacial side reactions, limited growth of interfacial resistance, fast electrode kinetics, less transition metal (TM) dissolution and more reversible phase transition. More importantly, first-principles calculations unravel the competitive coordination among solvents, BVSM and anions, rationalizing the CEI composition and electrochemical performance. Furthermore, the better cycling stability and stabilized average discharge voltage for graphite||NCM90 full cells are enabled by BVSM additive. • A novel electrolyte additive BVSM to stabilize NCM90 cathode. • A robust sulfur-involved and inorganic fluorides-enriched CEI with BVSM additive. • Competitive coordination among solvents, BVSM and anions revealed by DFT. • Improved cycling stability and fast kinetics enabled by BVSM additive.

Construction of a new levelled cost model for energy storage based on LCOE and learning curve

New energy storage is essential to the realization of the “dual carbon” goal and the new power system with new energy as the main body, but its cost is relatively high and the economy is poor at present. This paper studies the levelized cost of new energy storage based on the whole life cycle perspective. Based on LCOE and learning curve methods, a new levelled cost estimation model and prediction model for energy storage are constructed. Based on the latest development status of electrochemical new energy storage, the levelized cost of energy of lithium-ion batteries, flow-aluminum batteries, and flow-zinc batteries were measured, the cost composition and proportion of various types of energy storage are analyzed, and on this basis, the levelized cost of lithium-ion batteries was predicted. Comparative analysis shows that the levelized cost per kilowatt-hour of lithium-ion batteries is the lowest. This article provides a certain reference for the construction and layout of energy storage on three sides of the source network and load.

Advanced Electrode Materials for Lithium-ion Battery: Silicon-based Anodes and Co-less-Ni-rich Cathodes

The development of higher-performance rechargeable lithium-ion batteries (LIBs) is critical to the substantial development of electric vehicles and portable electronic devices. The cost of lithium-ion batteries needs to be decreased more and the specific energy as well as recycling degradation rate needs to be enhanced further. Silicon anodes and cobalt-free nickel-rich cathodes are widely regarded as promising materials for the next generation of lithium-ion batteries. This review discusses the current state of research on silicon anode nanomaterials and nickel-rich cathode materials without cobalt.

Coupled Simulation of Electric Flight Dynamics and Physics Based Battery Model for Electric Aircraft Battery Pack Sizing Analysis

Electrification of aircraft and aviation systems is a thriving area of research and technology development in recent years1. According to the Airbus Global Market Forecast, air traffic will double every 15 years, leading to increasing fuel consumption causing severe impact due to greenhouse gases and carbon emission2. Besides the environmental impact, as the international demand for fuel increases, and the fact that petroleum resources are limited, fuel prices are projected to rise. On the other side, the drop in the cost of lithium ion batteries makes electric aircraft feasible to commercialize now. This necessitates studying the battery pack sizing problem to build efficient Energy Management System (EMS) for electric aircraft.There is a significant amount of research on EMS for electric aircraft. Most of the current literature related to electric aircraft modeling considers the battery voltage to be linear3. This may lead to inaccurate estimation of state of charge (SOC), a key state variable for batteries and battery pack. In this work, we perform coupled simulation studies of the longitudinal flight dynamics and physics-based battery model (single particle model)4 ,5. This coupling enables accurate estimation of battery pack state of charge. The simulation studies are performed to understand the interplay between battery pack configuration/design parameters and variables/parameters related to flight dynamics, such as altitude, distance, flight path angle, and velocity. We also compare the SOC prediction of the battery pack using single particle model and dynamic empirical battery model. This work will be extended to develop efficient and robust EMS for electric aircraft. Acknowledgements This research was supported by the Texas Materials Institute (TMI) at The University of Texas at Austin. References J. A. Rosero, J. A. Ortega, E. Aldabas, and L. Romeral, IEEE Aerosp. Electron. Syst. Mag., 22, 3–9 (2007).Airbus global market forecase. [Online]., https://www.airbus.com/aircraft/market/global-market-forecast.html.M. Kaptsov and L. Rodrigues, J. Guid. Control. Dyn., 41, 285–290 (2018).S. Santhanagopalan, Q. Guo, P. Ramadass, and R. E. White, J. Power Sources, 156, 620–628 (2006).V. Ramadesigan, P. W. C. Northrop, S. De, S. Santhanagopalan, R. D. Braatz, and V. R. Subramanian, J. Electrochem. Soc., 159, R31–R45 (2012).

Promises and Challenges of Next-Generation "Beyond Li-ion" Batteries for Electric Vehicles and Grid Decarbonization.

The tremendous improvement in performance and cost of lithium-ion batteries (LIBs) have made them the technology of choice for electrical energy storage. While established battery chemistries and cell architectures for Li-ion batteries achieve good power and energy density, LIBs are unlikely to meet all the performance, cost, and scaling targets required for energy storage, in particular, in large-scale applications such as electrified transportation and grids. The demand to further reduce cost and/or increase energy density, as well as the growing concern related to natural resource needs for Li-ion have accelerated the investigation of so-called "beyond Li-ion" technologies. In this review, we will discuss the recent achievements, challenges, and opportunities of four important "beyond Li-ion" technologies: Na-ion batteries, K-ion batteries, all-solid-state batteries, and multivalent batteries. The fundamental science behind the challenges, and potential solutions toward the goals of a low-cost and/or high-energy-density future, are discussed in detail for each technology. While it is unlikely that any given new technology will fully replace Li-ion in the near future, "beyond Li-ion" technologies should be thought of as opportunities for energy storage to grow into mid/large-scale applications.

Estimating Degradation Costs for Non-Cyclic Usage of Lithium-Ion Batteries

Estimating the degradation costs of lithium-ion batteries is essential to the designs of many systems because batteries are increasingly used in diverse applications. In this study, cyclic and calendar degradation models of lithium batteries were considered in optimization problems with randomized non-cyclic batteries use. Such models offer realistic results. Electrical, thermal, and degradation models were applied for lithium nickel cobalt manganese oxide (NMC) and lithium iron phosphate (LFP) technologies. Three possible strategies were identified to estimate degradation costs based on cell models. All three strategies were evaluated via simulations and validated by comparing the results with those obtained by other authors. One strategy was discarded because it overestimates costs, while the other two strategies give good results, and are suitable for estimating battery degradation costs in optimization problems that require deterministic models.

Embedded ZnO nanoparticles in N-doped carbon nanoplate arrays grown on N-doped carbon paper as low-cost and lightweight electrodes for high-performance lithium storage

Traditional slurry-based electrodes consist of heavy current collectors and electroactive materials with a low weight percentage, which inevitably increase the total weight and cost of lithium-ion batteries (LIBs). Consequently, the development of low-cost, lightweight, flexible and binder-free electrodes for LIBs is highly desirable but also greatly challenging. In this work, we report the synthesis of small ZnO nanoparticles uniformly embedded in N-doped carbon (NC) nanoplate arrays (NPAs) tightly grown on a N-doped carbon paper (NCP) substrate (ZnO/NC NPAs@NCP) through a facile metal-organic framework-engaged strategy. This electrode design not only avoids the utilisation of insulating polymer binders but also offers other advantages, including large electrode/electrolyte contact areas, abundant electroactive sites, good wettability of the electrolyte, fast electron/ion transport and efficient volume accommodation. Notably, the freestanding ZnO/NC NPAs@NCP electrode displays a high reversible capacity of 610 mA h g−1 (based on the mass of entire electrode) at a current density of 100 mA g−1 for 50 cycles and excellent long-term cycling stability (363 mA h g−1 at 500 mA g−1 for 200 cycles). Furthermore, a full cell employing ZnO/NC NPAs@NCP as the anode and commercial LiFePO4 as the cathode is constructed, indicating the feasibility for practical application. Moreover, an analysis of the electrode kinetics confirms the favourable lithium-ion storage kinetics within the ZnO/NC NPAs@NCP electrode. The present work could provide a new approach to develop low-cost, lightweight and flexible electrodes for advanced energy storage.

Synthesis of High Surface Area α-KyMnO2 Nanoneedles Using Extract of Broccoli as Bioactive Reducing Agent and Application in Lithium Battery.

With the aim to reduce the entire cost of lithium-ion batteries and to diminish the environmental impact, the extract of broccoli is used as a strong benign reducing agent for potassium permanganate to synthesize α-KyMnO2 cathode material with pure nanostructured phase. Material purity is confirmed by X-ray powder diffraction and thermogravimetric analyses. Images of transmission electron microscopy show samples with a spider-net shape consisting of very fine interconnected nanoneedles. The nanostructure is characterized by crystallite of 4.4 nm in diameter and large surface area of 160.7 m2 g−1. The material delivers an initial capacity of 211 mAh g−1 with high Coulombic efficiency of 99% and 82% capacity retention after 100 cycles. Thus, α-KyMnO2 synthesized via a green process exhibits very promising electrochemical performance in terms of initial capacity, cycling stability and rate capability.

Rate and Voltage Dependence of the Electrode-Electrolyte Interface in Ni Containing Lithium-Ion Cathode Materials

Performance, safety, lifetime, and cost of lithium-ion batteries (LIB) are strongly influenced by the active materials used. As a result, cell chemistries are selected with the end goal in mind. For applications requiring superior power and safety, cells containing LiFePO4 cathodes and graphite anodes with an organic liquid electrolyte are frequently used. The major drawback of LIB cells designed for high-power is a relatively low energy density compared to high-energy cells, which conversely have poor rate capability. While graphite anodes remain a constant in most commercial LIB, recent research has identified cathode materials which would potentially mitigate the tradeoff between power, energy, and safety. In particular, spinel structured “LNMO” (LiNi0.5Mn1.5O4) and layered nickel-rich “NCM” compounds (LiNixMnyCozO2, X ≥ 0.5) have reportedly high energy densities relative to LiFePO4 while maintaining good power capability and thermal stability (1) (2). While LNMO and NCM compounds have similar composition and produce Ni4+ when fully charged, several reports have highlighted variations in surface chemistry resulting from electrolyte-electrode interactions as a function of cathode stoichiometry (3; 4; 5). One issue known to influence the surface chemistry and associated cycling stability of transition metal oxide cathode materials is the upper voltage cutoff needed to extract lithium during charge. Layered compounds can typically be reversibly delithiated within a voltage range of 4.2 to 4.6 V vs. Li/Li+ depending on the specific stoichiometry, while the spinel must be charged in excess of 4.8 V vs. Li/Li+, which historically has been a major hurdle to application. These upper voltage cutoff are already within the range of expected electrolyte oxidation, which is exacerbated by over potentials produced when charging at high current densities which further increase the upper voltage cutoff required to fully delithiate the cathode. This presentation will focus on analysis of the electrode-electrolyte interface, which is known to be a critical indicator of cell safety and lifetime, as a function of high-rate cycling and upper voltage cutoff. Composite cathodes containing spinel LNMO and layered NCM523 were cycled in a conventional lithium-ion electrolyte at various rates of charge and discharge, then disassembled in an inert atmosphere for analysis by X-ray Photoelectron Spectroscopy (XPS). Capacity and electrochemical impedance measurements were correlated with XPS analysis. Our results indicated that even when cycled in identical electrolytes spinel and layered compounds have notably different responses to an increased charge rate, specifically high rate charging (5C rate) is actually found to benefit LNMO, leading to lower impedance rise and associated formation of LiF, while the opposite is true for NCM523. One complicating factor in the XPS analysis of composite electrode is the presence of inactive components, specifically the binder and conductive additive. Both of these compounds dilute the overall signal detected from the active material, and some reports suggest may even contribute to the specific surface chemistry observed. To remove these effects, sol-gel films of identical composition to the composite electrode active materials were also synthesized and subjected to electrochemical cycling in the same electrolyte. [1] Review-Li-Rich Layered Oxide Cathodes for Next-Generation Li-Ion Batteries: Chances and Challenges. Rozier, P and Tarascon, JM. 14, 2015, Journal of the Electrochemical Society, Vol. 162, pp. A2490-A2499. [2] Spinel LiNi0.5Mn1.5O4 and its derivates as cathodes for high-voltage Li-ion batteries. Liu, G Q, Wen, L and Liu, Y M. 2010, Journal of Solid State Electrochemistry, Vol. 14, pp. 2191-2202. [3] Coupled LiPF6 Decomposition and Carbonate Dehydrogenation Enhanced by Highly Covalent Metal Oxides in High-Energy Li-Ion Batteries. Yu, Y, et al. 2018, Journal of Physical Chemistry C, Vol. 122, pp. 27368-27382. [4] XPS Studies of Surface Chemistry Changes of LiNi0.5Mn0.5O2 Electrodes during High-Voltage Cycling. Quinlan, RA, et al. 4, 2013, Journal of the Electrochemical Society, Vol. 160, pp. A669-A677. [5] Probing the Electrode-Electrolyte Interface in Cycled LiNi0.5Mn1.5O4 by XPS Using Mg and Synchrotron X-rays. Mansour, AN, et al. 14, 2016, Journal of the Electrochemical Society, Vol. 163, pp. A2911-A2918.

Influence of Conductive Agent in C/Si-Composite Electrodes for High-Energy Lithium Ion Batteries

Lithium ion batteries outperform other energy storage technologies in the combination of specific power and specific energy [1]. However, continuous improvement is necessary regarding the ever-increasing demands in terms of high energy densities, long cycle life and improved safety properties. One strategy to increase the specific energy density and decrease the overall cost of lithium ion batteries is the partial substitution of graphite with silicon in the negative electrode. Silicon forms alloys with lithium and offers an extremely high theoretical capacity (3579 mAh g-1) [2, 3]. However, the lithiation and delithiation process of silicon generates mechanical stress due to particle swelling and contraction (∆V ≥ 300%). This stress eventually causes mechanical fracture and pulverization, which in turn leads to active material loss. Inactive materials and the use of a composite of active materials, silicon and graphite (C/Si), can help to mitigate these degradation effects. The binder ensures adhesion and cohesion of and within the electrode and its different components. Conductive agents improve the electrical conductivity and provide inter-particle as well as particle-current collector contacts. Therefore, the electrode and cell design can largely influence the electrochemical performance and cycle life. Different applications require different ratios of active material, conductive agent and binder. Especially considering the low electrical conductivity of silicon [4], the use of conductive carbon is inevitable to increase electrical conductivity within the composite electrode. However, with C/Si electrodes, the necessity of conductive agent is questionable, since the graphite present in the composite might be able to provide sufficient electrical conductivity. Furthermore, an excessive amount of inactive material reduces the energy density of the electrode and has to be optimized. This study focuses on the impact of conductive agent in high energy C/Si composite electrodes. To ensure a high loading and high energy density, the amount of inactive materials were optimized. For that, electrodes were prepared with different amounts of conductive agent and electrochemically tested in coin cells (charge/discharge cycle). Internationl Energy Agency Technology Roadmap Electric and plug-in hybridelectric devices: Technical report 2011.Sharma, R. A. and Seefurth R. N. J. Electrochem. Soc. 1976 volume 123 , 1763-1768. 1976, 123 (12), 1763.Boukamp, B.A., et al. J Electrochem Soc 1981, 128, 725-729Pollak, E.,et al. J. Phys. Chem. C 2007, 111, 30, 11437-11444

Microwave Synthesized TiP2O7/Carbon Composites for Use in Aqueous Lithium-Ion Batteries

Nowadays, Lithium ion batteries (LIBs) can be found in every corner of our daily life. However, safety and cost of lithium ion batteries are the two major issues. Aqueous rechargeable lithium ion batteries are believed to be the promising candidates for LIBs due to nonflammable，low cost higher ionic conductivity of aqueous electrolyte [1]. To reduce the cost of aqueous lithium-ion cells, researchers focus on developing methods to synthesize electrode material in an energy efficient way. It has been reported that TiP2O7 has a low intercalation /de-intercalation potential (2.6 V versus Li/Li+) [2], which makes it a promising anode material for aqueous lithium-ion batteries [3,4]. One report demonstrated a solid-state synthesis method annealing at 300◦C for 2 hours, annealing at 800◦C for 3 hours and cooling to room temperature for 4 hours [5]. The solid-state synthesis route is very common in industrial applications due to its simplicity. However, the long calcining duration and high temperature requirement increases the processing cost for the electrode materials. One report applied microwave to synthesize C-NaTi2(PO4)2, the negative electrode for aqueous sodium ion batteries [6]. Functional electrode materials can be synthesized in less than 20 minutes. In this work, a very fast microwave synthesis method was developed to produce C-TiP2O7 (Carbon and TiP2O7 Composite material). The precursor consists of (NH4)2HPO4 and anatase TiO2 in a molar ratio of 2:1, with 10wt%, 15wt% and 20wt%(the weight percent is relative to the precursor mixture) graphite added. After being ball milled together for 1 hour, the mixture was heated in a microwave oven (CEM Discover Proteomics System) for 10 minutes at 150W. The SEM figure shows the surface of Graphite-TiP2O7 composite, and the particle size of Graphite-TiP2O7 composite is around 40nm (Figure 1a). In XRD test (Figure 1b), the pattern of product matches with the reference pattern (JCPDS #38-1468) at major peaks (511), (600), (630), (721), (660), (933). The products we get from this method are tested in cyclic voltammetry tests, which shows promising electrochemical performance (Figure 2a); after ten cycles, the specific capacity of 10% Graphite-TiP2O7 composite maintains 107.4 mAh/g. (Figure 2b). Figure 1 a) SEM of Graphite-TiP2O7 composite. B) XRD patterns of Graphite-TiP2O7 composite and reference peaks. Figure 2 a) Second cycles of cyclic voltammetry curves of 10% Graphite-TiP2O7 composite, 15% Graphite-TiP2O7 composite and 20% Graphite-TiP2O7 composite in 1 M Li2SO4 at scan rate 0.5 mV/s in range of −0.5 V and −1.6 V versus MSE. b) Discharge cycling performance of Graphite-TiP2O7 composite. The total synthesis time is only 10 minutes for heating and 30 minutes for cooling, which is much less than for traditional solid state synthetic methods. Reference: Kim H, Hong J, Park K Y, et al. Aqueous Rechargeable Li and Na Ion Batteries[J]. Chemical Reviews, 2014, 114(23):11788.Aravindan V, Reddy M V, Madhavi S, et al. Hybrid supercapacitor with nano-TiP2O7, as intercalation electrode[J]. Journal of Power Sources, 2011, 196(20):8850-8854.Wang H, Huang K, Zeng Y, et al. Electrochemical properties of TiP2O7, and LiTi2(PO4)3, as anode material for lithium ion battery with aqueous solution electrolyte[J]. Electrochemical Acta, 2007, 52(9):3280-3285.Rai A K, Gim J, Song J, et al. Electrochemical and safety characteristics of TiP2O7 –graphene nanocomposite anode for rechargeable lithium-ion batteries[J]. Electrochemical Acta, 2012, 75(4):247-253.Wu W, Shanbhag S, Wise A, et al. High Performance TiP2O7 Based Intercalation Negative Electrode for Aqueous Lithium-Ion Batteries via a Facile Synthetic Route[J]. Journal of the Electrochemical Society, 2015, 162(9): A1921-A1926.Wu W, Mohamed A, Whitacre J F. Microwave Synthesized NaTi2(PO4)3 as an Aqueous Sodium-Ion Negative Electrode[J]. Journal of the Electrochemical Society, 2013, 160(3): A497-A504. Figure 1

Battery energy storage systems as a way to integrate renewable energy in small isolated power systems

Isolated power systems present high levels of Renewable Energy Sources (RES) curtailment as intermittency and isolation impose challenging difficulties regarding the integration of this energy into the electrical grid. The recent developments in electrical vehicles have decreased the kWh cost of lithium-ion batteries below a threshold value that was previously prohibitive for grid-scale applications. Therefore, the integration of RES considering the installation of a Battery Energy Storage System (BESS) into an isolated power grid is an up-to-date research topic and is assessed in this paper. The BESS is inserted into the Unit Commitment and Economic Dispatch (UC + ED) platform and regarded as another dispatchable generator. To keeps the costs down, the BESS is mainly used to provide a portion of the spinning reserve needs and secondly to alleviate the load of the thermal generators, using the free modules. The BESS configurations that maximises the economic viability and minimises the RES curtailment are presented. The results suggest that the investment in this technology may be profitable and considerably decreases the levels of RES curtailment.

Impact of the Synthesis Conditions on the Performance of LiNixCoyAlzO2 with High Ni and Low Co Content

One way to lower the cost of lithium ion batteries using LiNixMnyCozO2 (NMC) or LiNi0.80Co0.15Al0.05O2 is to lower the Co content in the positive electrode materials. This work systematically studied the impact of the synthesis conditions on the performance of LiNixCoyAlzO2 (x ≥ 0.8, z ≤ 0.05 and x + y + z = 1) (NCA) with high Ni and low Co content. The impacts of oxygen flow rate, sintering temperature, initial Li/TM ratio and sintering time on the structural and electrochemical properties of NCA were systematically studied. The conditions when impurity phases such as Li2CO3 and Li5AlO4 appear were carefully examined. The impact of residual lithium compounds on the electrochemical performance was also discussed. It was found that the synthesis conditions, which affect the a-axis, c-axis and NiLi content of the NCA samples, have strong impacts on the lithium diffusion at low and high states of charge based on differential capacity vs. voltage (dQ/dV vs. V) measurements at various rates and temperatures. Additionally, the reversible capacity and cycling stability correlated strongly with the intensity of the dQ/dV vs V peak at 3.5 V (discharge) measured with a C/20 rate at 30°C.

Mathematical Modelling and Analysis of Solvent Drying in Electrode Processing for Battery Manufacturing

The development of efficient and affordable electric vehicles is receiving ever greater interest from both industry and academia. This, indeed, is in the interest of migrating towards emission free vehicles. Arguably, one of the greatest barriers in the successful deployment of electric vehicles is the cost of the batteries inherent to such vehicles. In order to compete with the internal combustion engine (ICE) based vehicles, the current practices of producing the batteries need significant changes in technology and cost. The development of new materials and chemistries for more efficient and economic batteries is receiving a greater interest in the research community. However, for a successful commercialization and to bring down the overall cost, each processing step in the manufacturing of these batteries also needs to be improved and optimized. Argonne National Laboratory has developed, BatPac [1], a comprehensive spreadsheet tool for estimating the cost of Lithium Ion Batteries (LIB) with granularity to the cost contribution from each processing step. Analysis of each step, backed by thermal-hydraulic models where possible, offers the potential for quantifying and identifying the opportunities for reducing the cost and energy consumption of each processing step. Among the various processing steps in the production of LIBs, drying and solvent removal from the electrode coating is an energy and cost intensive process [2]. Solvent removal and drying of the coating is also a slow process, which is a potential bottleneck in the production line of LIBs. Thus, it is very useful to study and analyze this processing step in a greater detail. In general, solvent removal and drying has been widely studied [3-4]. However, few studies exist in the literature that focuses on the solvent removal and drying in the context of LIBs. This forms the focus of this study. In this work, we study and analyze the design aspects and energy requirements of solvent removal and drying in the electrode processing step of LIB production. The heat for the drying is derived from a combination of infra-red (IR) radiators and hot air injectors. We develop a mathematical model of the physical phenomena to understand the various factors affecting the drying rate. The solvent removal involves simultaneous heat and mass transfer with phase change. Our model considers capillary flow and gravity effects for liquid transport and diffusion for vapor phase transport. The model also accounts for the shrinkage of coating thickness with the removal of the solvent and so, the voidage is considered to be a function of solvent saturation in the coating. The system of non-linear partial differential equations is then solved numerically using a finite element method to predict the concentration and temperature profiles within the drying cathode layer. We finally study the effects of various factors such as drying temperatures and air conditions on the process performance. Acknowledgement The authors gratefully acknowledge support from the Vehicle Technologies Office, Hybrid and Electric Systems, David Howell (Team Lead), at the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy. Reference [1] P. Nelson, K. Gallagher and I. Bloom, "BatPaC (Battery Performance and Cost) Software," Argonne National Laboratory, 2012. [Online]. Available: http://www.cse.anl.gov/BatPaC/. [2] S. Ahmed, P. Nelson, K. Gallagher, D. Dees, “Energy impact of cathode drying and NMP recovery during LIB manufacturing.” Manuscript in preparation. [3] F. Chen, D. Pei, “A mathematical model of drying processes.” Intl. J. Heat Mass Transfer 32 (1989): 297-310. [4] Z. Przesmycki, “The mathematical modelling of drying process based on moisture transfer mechanism.” Drying’85 (1985): 126-134. [5] E. Gutoff, “Modelling solvent drying of coated webs including the initial transient.” Drying Technology 14 (1996):1673-1693.

Hygroscopic and Drying Behaviour of Electrodes and Separators for Lithium Ion Batteries

The industrial scale production of high-performance and long term stable lithium ion batteries (LIBs) relies on the usage of precisely tailored materials of high purity. Even small deviations in the material properties or contaminations may lead to detrimental effects regarding the battery’s stability, safety and rate capability. For example, the commonly used conducting salt LiPF6 hydrolyses in the presence of trace amounts of water in the organic solvent, generating HF and further decomposition products [1, 2]. These products can degrade battery components and, consequently, lead to a bad performance of the battery [3]. The components which can contribute to the overall water contamination level inside a LIB are the electrodes, the separator, the housing and the electrolyte itself. Therefore all these components of a LIB have to be dried carefully before assembly. These time and energy intensive processes, contribute to the overall costs of LIBs. In order to ensure a sufficiently low moisture level inside the battery components, while, at the same time, keeping the drying costs low, a detailed understanding of the water sorption and drying behaviour of those battery components is required. While the trace water concentrations in commercially available LIB electrolytes (usually 15 ppm or lower) is commonly precisely monitored, a systematic and comparative study of the hygroscopic and drying behaviour of different electrodes and separators has not been performed yet. This work focusses on the investigation of hygroscopic and drying behaviour of various common anodes, cathodes and separators. Therefore, samples were stored in a defined atmosphere (25 °C, 40 %rh) and their moisture sorption as well as the subsequent drying behaviour (at 120 °C) were studied. The moisture content and drying behaviour of battery components was analysed by a coulometric Karl Fischer titrator. During the sample drying, the evaporated water was transferred into the titrator by a dry argon stream and the water detection was recorded. The results show that the investigated cathodes and anodes differ strongly in their drying behaviour (Fig. 1). Cathodes with LiMn2O4 as active material absorb a high amount of water from the atmosphere and show and a delayed water release while drying. The LiFePO4 cathode also shows strong water uptake, but to a lesser extent than the LiMn2O4 cathode. In contrast, the LiNi1/3Co1/3Mn1/3 cathode shows an amount of water sorption, which is even lower than the water sorption of the commonly used graphite anode. In accordance with the hydrophobic surface behaviour of the polypropylene separator (Celgard PP2500), its water uptake is very low. The glass fibre separator (Whatman GF/C) on the other hand has a large and hydrophilic surface, which results in a very high water content. The water emitted from the samples during the drying process is continuously quantified in the Karl Fischer Titrator. As a consequence time dependent moisture emission rates for the different electrodes and separators are obtained. Fitting and extrapolating the moisture emission rates allows to draw conclusions beyond the runtime of the drying experiments. For example the drying times until reaching threshold levels for the remaining water concentration in the sample can be calculated (Fig. 2). [1] D. Aurbach, a. Zaban, Y. Ein-Eli, I. Weissman, O. Chusid, B. Markovsky, M. Levi, E. Levi, a. Schechter, and E. Granot, J. Power Sources, vol. 68, no. 1, pp. 91–98, Sep. 1997. [2] A. V. Plakhotnyk, L. Ernst, and R. Schmutzler, J. Fluor. Chem., vol. 126, no. 1, pp. 27–31, Jan. 2005. [3] U. Heider, R. Oesten, and M. Jungnitz, J. Power Sources, vol. 81–82, pp. 119–122, Sep. 1999. Figure 1

The Performance of Hard Carbon in a Sodium Ion Battery and Influence of the Sodium Metal in Observed Properties

Since the 1990’s and the commercialisation of the first lithium ion cell by Sony there has been a large focus on new materials for lithium ion batteries, and the work in the 1970’s and 80’s in room temperature sodium ion materials was lapsed. However, due to the high current cost of lithium ion batteries, alternative sodium ion technologies may offer a cost and safety advantage over the typical lithium ion cells.1,2 Sodium is a much more abundant metal when compared to lithium which should result in lower cost materials. Although the mass of sodium is higher than lithium, the observed specific capacity of a sodium ion battery compared to lithium is not hugely compromised; this is because the proportion of the sodium and lithium content is small enough that the difference is minimal. Sharp Laboratories of Europe Ltd have been developing a new sodium ion cell chemistry based upon a layered oxide cathode3 and a hard carbon anode. The hard carbon anode is extremely sensitive to processing conditions and testing methods. In two electrode cells we have observed high hysteresis in the charge and discharge profiles and have experienced difficulties in reaching the low voltages required for complete sodiation of the hard carbon. In addition we have also observed high Coulombic inefficiencies during the testing in a sodium metal anode cell, and the instability of the sodium in certain solvents. By using 3-electrode cells we have been able to investigate the specific properties of the hard carbon in considerably more detail, and note that much of the hysteresis observed in two electrode measurements originates from the sodium metal anode. 3-electrode galvanic and potenstiostatic intermittent titration techniques have been used to investigate the properties of the hard carbon and sodium metal electrodes in more detail, and much of the hysteresis with regards to the performance of the carbon material in a 2-electrode cell can be shown to be related to the sodium metal deposition and stripping. Figure 1 shows the galvanic intermittent titration technique (G.I.T.T.) for hard carbon vs sodium metal in a 3-electrode arrangement visualising the difference between cell potential (red) and potential of the working electrode vs sodium reference (hard carbon, blue). V. Palomares, P. Serras, I. Villaluenga, K.B. Hueso, J. Carretero-Gonzalez and T. Rojo, Energy Environ. Sci. 2012, 5, 588,J. Barker, M.Y. Saidi and J. Swoyer, Electrochem. Solid-State Chem. 2003, 6, A1,E. Kendrick, R. Gruar et al, Tin containing compounds, WO2015177568A1, 2015-11-26 Figure 1

Prospects for reducing the processing cost of lithium ion batteries

A detailed processing cost breakdown is given for lithium-ion battery (LIB) electrodes, which focuses on: 1) elimination of toxic, costly N-methylpyrrolidone (NMP) dispersion chemistry; 2) doubling the thicknesses of the anode and cathode to raise energy density; and 3) reduction of the anode electrolyte wetting and SEI-layer formation time. These processing cost reduction technologies generically adaptable to any anode or cathode cell chemistry and are being implemented at ORNL. This paper shows step by step how these cost savings can be realized in existing or new LIB manufacturing plants using a baseline case of thin (power) electrodes produced with NMP processing and a standard 10–14-day wetting and formation process. In particular, it is shown that aqueous electrode processing can cut the electrode processing cost and energy consumption by an order of magnitude. Doubling the thickness of the electrodes allows for using half of the inactive current collectors and separators, contributing even further to the processing cost savings. Finally wetting and SEI-layer formation cost savings are discussed in the context of a protocol with significantly reduced time. These three benefits collectively offer the possibility of reducing LIB pack cost from $502.8 kW h−1-usable to $370.3 kW h−1-usable, a savings of $132.5/kWh (or 26.4%).

Hydrothermal synthesis of LiMn2O4 onto carbon fiber paper current collector for binder free lithium-ion battery positive electrodes

Concerns over the safety and high cost of lithium ion batteries, especially those containing cobalt-based active materials, limit their use to applications where energy density requirements cannot be met by any other materials. Manganese-spinel based positive electrode materials represent a promising candidate for lithium ion batteries because of their lower cost, lower toxicity, and greater resistance to thermal runaway than cobalt-based active materials. Although LiMn2O4 has a well-known issue of capacity fading, investigations into nanostructured composites composed of surface modified spinel phases have demonstrated outstanding performance, suggesting that LiMn2O4 has potential to be a viable positive electrode for safe, inexpensive, high power, and long lifetime lithium-ion batteries. Here we report a low-temperature hydrothermal process for growth of conformal coatings of highly crystalline LiMn2O4 directly onto a carbon fiber current collector, completely eliminating the process steps and materials associated with the conventional tape casting approach (binders, solvents, and metal foils). The prepared electrodes tested at a rate of 1 C showed an initial discharge capacity of 125 mAh g−1 and an average energy efficiency of 92.4% over 100 cycles.