Rechargeable Lithium-ion Cells Research Articles

Examination of smart battery thermal management system using the counter flow of air and nanofluid for cooling cylindrical rechargeable batteries for better resilience

This paper examines smart thermal management of a battery pack (BTK) with a square arrangement of 16 cylindrical battery cells numerically. The cooling of the battery is carried out simultaneously using laminar airflow in a channel and laminar nanofluids (NFs) flow in the tube inserted between the battery cells. The BTK includes rechargeable lithium-ion cells and a tube placed in the channel. The inlets of air and NFs are counter-flow, and the study is done at constant air velocity for different NFs velocities in the tube from 0.001 to 0.003 m/s and different volume percentages (VOP) of NFs from 1 % to 3 %. The numerical study is performed transiently using the finite element method in 2000 s. The results demonstrate that the use of NFs and air for the thermal management (THMT) of battery cells results in better temperature uniformity on the battery cells, especially in the rows placed at the outlet. An increment iimproveP of nanoparticles improves the heat transfer coefficient (HTRC) between air and NFs flows. Also, enhancing the VOP of NFs increases the temperature of the outlet air and decreases the temperature of the outlet NFs. The average temperature (T-Av) and the maximum temperature (T-Mx) of the BTK are high until the battery is charged. They are reduced when the battery charge is stopped due to the air and NFs flows.

LFO modified separator for the initial anode irreversibility compensation in lithium-ion rechargeable full cells

Lithium-ion batteries (LIBs) dominate portable electronics and electric vehicles for their high energy density and long cycle life. However, a part of active Li loss in the initial charge process for the solid electrolyte interphase (SEI) formation at the anode surface, which reduces the energy density and cycle life of LIBs. Prelithiation attempts have been widely regarded as providing additional active lithium to address this issue. Li5FeO4 (LFO) as a cathode prelithiation additive with high donable lithium ions is very promising. But the residues of the gas release limited its further application due to its low conductivity in the first charge process. Here, we prepared CNT/ Polyacrylonitrile (PAN) /LFO/polypropylene (PP) separator by an electrospinning method, the CNT/PAN/LFO/PP separator can effectively improve cycle performance of LFP batteries, benefiting from Li2O participation in the construction of SEI and higher infiltration rate of the electrolyte resulting in faster interfacial Li+ transfer kinetics. The LFP pouch cell with CNT/PAN/LFO/PP separator can maintain a stable output over 1000 cycles (capacity fade rate per cycle of 0.005 %) with a highercapacity increased by 6.2 %.

Electrochemical characteristics of electrophoretically deposited nickel antimony oxide anode for lithium-ion rechargeable cells

Lithium‐ion batteries (LIB) are widely used energy storage devices for powering portable electronics, electric transportation, and the grid. In this work, the co-precipitation method synthesizes nickel antimony oxide (NiSb2O6; NSO), a relatively new material for LIB anode. The structure of this material is a tri-rutile phase, wherein the lithium (Li) ions are stored via a conversion-type mechanism. The nickel antimony oxide-carbon black (NSO-CB) electrodes are fabricated using electrophoretic deposition. Ex-situ X-ray diffraction analysis reveals the structural breakdown of NSO into nickel oxide (NiO) and antimony pentaoxide (Sb2O5) after the first discharge. In the voltage range 0.01–2.5V vs. Li+/Li, a stable reversible capacity of 574 mAhg−1 is obtained at a specific current of 0.5Ag-1 after 100 cycles. At a high specific current of 5Ag-1, these electrodes deliver a specific capacity of 370 mAhg−1, equivalent to graphite's theoretical capacity. The full-cell of Li(Ni0.8Co0.1Mn0.1)O2//NSO-CB delivers a nominal voltage of 2.83V vs. Li+/Li and can retain up to 84.2 % of its reversible capacity after 50 cycles. Therefore, electrophoretic deposition is established as a prospective processing technique to implement tri-rutile type NiSb2O6 as an anode material for LIBs.

Design considerations and cycling guidance for aluminum foil anodes in lithium-ion rechargeable cells

Al foil is an attractive anode candidate for Li-ion rechargeable batteries, but the systemic problem of fast capacity degradation limits its re-introduction in practical applications. Partial lithiation-delithiation does mitigate the issue to a certain degree, but the cycle life is still tied to the problems associated with the phase transformation between β-LiAl and α-Al. Utilizing the solubility range of β-LiAl has been proven to be a feasible approach to stabilize the β-LiAl grown on an Al foil, i.e., the β-LiAl(Al) anode, but the electrochemically driven ion transport limitations of this electrode remain largely unclear. Herein, we present comprehensive electrochemical analyses of the β-LiAl(Al) electrode to shed light on its kinetic limitations which have intrinsic links to the electrode thickness and total cell capacity. Results show that the β-LiAl(Al) electrode can be charged at a C-rate as high as 2.9 C when a proper prelithiation is done for an Al foil. The superior rate capability is suggested to partly originate from the fast lithium diffusion in β-LiAl: -10−7 cm2·s−1 at room temperature. Furthermore, the cells consisting of β-LiAl(Al) vs. commercial Li4Ti5O12 exhibit promising cycling performances, even at 10 mA·cm−2, giving 300 cycles with a capacity retention of ∼80%. With a systematic investigation of the limiting mechanisms focusing on correlating the prelithiation depth and the cycle life, the cyclability of the β-LiAl(Al) electrode at different current densities (0.5–10 mA·cm−2) is mapped out, providing comprehensive guidance for the practical utilization of the β-LiAl(Al) anode in a range of Li-ion cell types, from all-solid-state batteries to hybrid capacitors.

Simplifying Electrode Design for Lithium-Ion Rechargeable Cells.

In the race to increase lithium-ion cell manufacturing, labor and energy costs quickly ascend to become chief concerns for building new facilities, as conventional electrode designs need significant resources during fabrication. Complicating this issue is an empirical trade-off between environmental friendliness and ethical sourcing. To circumvent this paradox, modified cell designs that employ foils and textiles can significantly change manufacturing considerations if their simple construction can be matched with competitive performance. In this work, we demonstrate one possible cell design for a lithium-ion device that utilizes a fabric and a foil for the cathode and the anode, respectively. For the anode, a prelithiated aluminum foil is chosen, as the room-temperature solubility range of the LiAl phase is well-suited to uptake and release lithium, all while reducing energy or cost-intensive production steps. The cathode is composed of activated carbon fiber textiles, which offer a scalable path to realize sustainability. With such benefits, this device design can potentially change the calculus for the mass production of energy storage devices.

Investigations on the electrochemical characteristics of electrophoretically deposited NiTiO3 negative electrode for lithium-ion rechargeable cells

Due to high theoretical capacities, high energy densities, and widespread abundance, transition metal oxides have attracted much attention as negative electrode materials for Li-ion batteries (LIBs). We report herein the facile synthesis and fabrication of nickel titanate (NiTiO3) electrodes as potential anodes for LIBs. NiTiO3 (NTO) was synthesized by a conventional sol–gel process, and then a NTO-carbon black film was deposited on Cu foil by a simple electrophoretic deposition (EPD) technique. The NTO-carbon black electrode delivers a stable reversible specific capacity of 281 mA h g−1 at a specific current of 50 mA g−1 after 100 cycles. At a high specific current of 1.6 A g−1, the electrode exhibits a specific capacity of 130 mA h g−1. When the NTO-carbon black electrode of the same composition was fabricated by a conventional tape-casting process, it showed rapid capacity fading and poor rate performance. Microstructural analysis has revealed that EPD-grown electrodes have a uniform distribution of NTO particles surrounded by carbon black particles. Such microstructure, coupled with good adherence of the deposited film on the Cu current collector, helps to mitigate the large volume changes that occur during cycling for conversion-type NTO material and thereby improves its electrochemical properties.

Electrophoretic deposition of metal-organic framework derived porous copper oxide anode for lithium and sodium ion rechargeable cells

This article demonstrates the applicability of electrophoretically fabricated CuO-carbon black (CB) film as negative electrodes for lithium and sodium-ion rechargeable cells. CuO powder is derived from a thermally decomposed copper metal-organic framework (MOF) template. Electrophoretic deposition (EPD) of CuO-CB electrode has been carried out from a stable CuO-CB suspension, which is prepared in isopropanol medium containing polyacrylic acid and nickel nitrate as dispersant and charging agent respectively. The obtained EPD films are found to be porous and strongly adherent to underlying current collector, with a uniform distribution of CB and CuO. These films are observed to retain a reversible specific capacity of 500 mA h g−1 at 0.5 A g−1 and 256 mA h g−1 at 0.1 A g−1 after 100 cycles as Li-ion battery and Na-ion battery anode respectively. The uniformly dispersed CuO within the conductive network of CB particles is found to sustain the high-rate battery operations efficiently and exhibit a specific capacity of 265 mA h g−1 at 5 A g−1 (LIB) and 140 mA h g−1 at 3 A g−1 (SIB). Owing to the simple and cost-effective route for fabricating these negative electrodes, electrophoretically deposited CuO-CB porous film proves to be a suitable candidate for high-rate Li-ion and Na-ion batteries.

Observation of memory effects associated with degradation of rechargeable lithium-ion cells using ultrafast surface-scan magnetic resonance imaging

Batteries share their “health problems” and “memories” of hazardous life-cycle events via DC-induced magnetic field patterns revealed by MRI.

Thermo-Electrochemical in-Situ Instrumentation for Smart Energy Storage

Lithium-ion rechargeable cells are widely used as instant power delivery devices. High energy and power densities along with capacity retention over tens of thousands of cycles are highly beneficial compared to alternative technologies. However, recent failure incidents and constant health and safety concerns are slowing down the adoption of this technology and limiting the performance through cautious approach. In order to alleviate these issues, a better understanding of the performance and safety limits and the cells’ internal thermodynamic responses is required. Both the in-situ thermal and electrochemical mechanisms need to be carefully characterised to unlock the full performance without jeopardising safety. This work focuses on an altogether new in-situ instrumentation methods coupling the use of a quasi-reference electrodes, optical sensing technology and miniature thermistors for supplemental internal and external temperature profiles. This methodology allows for new level of analysis, providing insight into in operando in-situ parameters of a range of cell shapes and formats. Higher reliability, shorter charging times and early fault detection can be achieved with the use of smart instrumented Li-ion cells, enabling significant advances in the battery technology. Figure 1

Fabrication and Investigation of MCMB–LiNi0.5Mn1.5O4Pouch Cells for High Energy Density Lithium-Ion Batteries: Indigenous Efforts and Challenges for Realization

In the present work, we have fabricated indigenous 300 mAh lithium-ion rechargeable pouch cells using laboratory made LiMn1.5Ni0.5O4 cathode and commercial meso carbon micro-beads anode. Required mass balancing was performed to yield pouch cell of 300 mAh capacity at C/4 rate. When charged and discharged at C/4 and C/3 rates the fabricated pouch cells retained ~ 79% of their capacities after 50 cycles. Post-mortem analysis of the cycled pouch cell indicated the dissolution of Mn and Ni from cathode and deposition of the same at anode and separator. The observed bulging of the cycled pouch cell could be due to evolution of gases through chemical decomposition of conventional organic electrolyte. Though active material dissolution and gas evolution might reduce deliverable capacity and operating voltage of the fabricated pouch cells, yet the reported electrochemical characteristics were far superior to many of the existing literature reports.

Pushing to the Limit: Samsung Galaxy Note 7 and Fitbit Flex 2

The ongoing demand for smaller and lighter devices, with batteries having longer usage times, has put increasing operational pressure on the batteries. The use of higher capacity cathodes, increasing areal capacity and thinner separators are some of the approaches used to achieve higher energy densities. Here we report two case studies on batteries from the Samsung Galaxy Note 7 phone and fitness tracker wristband, Fitbit Flex 2, highlighting where the device manufacturers were pushing the boundaries to achieve this higher energy density. In September 2016, several reports were published of the Samsung Galaxy Note 7 phone batteries overheating, exploding or catching fire, which led to a total product recall of the Samsung Galaxy Note 7 phone. “The launch of what was supposed to be its flagship model has turned into a fiasco for the world's largest smartphone maker”, the BBC reported1. We carried out a more in-depth investigation, “Looking Deeper into the Galaxy (Note 7)2”, inspecting each of the battery components. The study incorporated X-ray computed tomography, thermal imaging and scanning electron microscopy (with energy dispersive spectroscopy), to identify the most likely root causes of the battery failure. The findings reveal that thermal properties of the battery is not thought to be a contributing factor to battery failure but are from battery design/cell manufacturing defects: (1) Unintended folding of the anode coating at the corner near to the anode tab resulted from insufficient space to safely accommodate the electrodes; (2) No Insulating tape on the cathode tab, and (3) un-bonded welding sections with protrusion features observed at the cathode tab which may penetrate the separator. Such flaws can lead to internal short circuit between the cathode and anode; (4) A much thinner separator (≤ 5 µm, with <1 µm Al2O3 coating on both sides) used in Galaxy Note 7 also increased the likelihood of separator damage which can lead to short circuit. The ceramic coating layer detached itself quite easily when the cell was unravelled, indicating a lack of interfacial integrity. We also report another forensic investigation on a miniature lithium ion rechargeable cylindrical cell with a diameter of 3.65 mm and length in 20 mm, and nominal capacity of 15 mAh, which is fitted in Fitbit Flex 2 fitness tracker. This miniature cylindrical cell shows an impressive volumetric energy density of 503 Wh/L despite having a limited space. The unravelling of the jelly roll shows severe anode coating delamination from the copper current collector, transferring unto the separator. The high bending stress exert on the cell components when rolled up to a 3 mm diameter jelly roll has resulted severe delamination of the anode coating. 1. http://www.bbc.co.uk/news/technology-376154962. Melanie J. Loveridge, Guillaume Remy, Nadia Kourra, Ronny Genieser, Anup Barai, Mike J. Lain, Yue Guo, Mark Amor-Segan, Mark A. Williams, Tazdin Amietszajew, Mark Ellis, Rohit Bhagat and David Greenwood, Looking Deeper into the Galaxy (Note 7). Batteries 2018, 4 (1), 3. Figure 1

Stabilized Lithium, Manganese AB2O4 Spinel for Rechargeable Lithium Electrochemical Systems through A and B Site Doping

Lithium manganese oxide doped with potassium and cobalt produces a promising cathode material for rechargeable lithium-ion cells. Modifying the A site and B site of the spinel structure works to limit cathodic capacity fading by enhancing the robustness of the material. LixKyMn2-zCozO4 was synthesized as the active ingredient for the cathode with x=1, y=0.1, and both z=0.1 and 0.2, and was tested against metallic lithium to evaluate performance. Through high-rate discharge, pulse cycling, and deep discharge tests, the electrochemistry of the cathode exhibited excellent reversibility and overall performance stability. LiK0.1Mn2-zCozO4 proved to be a capable abuse tolerant option for use in rechargeable battery applications.

Stabilized Lithium, Manganese AB2O4 Spinel for Rechargeable Lithium Electrochemical Systems through A and B Site Doping

Lithium manganese spinel (LixMn2O4) has been extensively investigated as a safe and affordable lithium ion cathode material that can provide a great lattice for lithium intercalation. However, a major obstacle when utilizing LixMn2O4 cathodes is the loss of cycle capacity that occurs during cell charge and discharge. Lithium manganese oxide doped with potassium and cobalt produces a promising cathode material for rechargeable lithium-ion cells. Modifying the A site and B site of the spinel structure works to limit cathodic capacity fading by enhancing the robustness of the material. Successfully preventing degradation of the spinel matrix is key to maintaining the electrochemistry’s reversibility over prolonged cycling and abusive conditions. LixKyMn2-zCozO4 was prepared by modifying a stabilized lithium manganese-based AB2O4 spinel material with potassium A site and cobalt B site dopants. This was done using a two-step method where a manganese mixed metal oxide precursor was synthesized and subsequently used in a solid state reaction. LixKyMn2-zCozO4 was synthesized as the active ingredient for the cathode with x=1, y=0.1, and both z=0.1 and 0.2, and was tested against metallic lithium to evaluate performance. In order to assess the robustness of the LixKyMn2-zCozO4 cathode material at both z=0.1 and z=0.2, a number of cycling tests were run and analyzed in comparison to each cell’s baseline performance. A 2 mA cycling test between 3.0 or 2.5 V and 4.5 V was run initially on all cells to establish baseline performance, and was run between high rate discharge tests, pulse cycling tests, and deep discharge tests in order to compare to the cell’s baseline. Different groups of cells were discharged at 2, 4, 8, 12, 16, and 20 mA, pulse charged and discharged for 1 second with a 1 second rest, and deep discharged down to 2.5 V in order to assess the reversibility of the LixKyMn2-zCozO4 cathode chemistry when compared back to baseline performance. Through high-rate discharge, pulse cycling, and deep discharge tests, the electrochemistry of the cathode exhibited excellent reversibility and overall performance stability. For example, Figure 1 shows a Li \\ LiK0.1Mn1.8Co0.2O4 cell that retains its full capacity when tested at the 2 mA cycling baseline after high discharge rates of 4, 12, 16, and 20 mA for 10 cycles at a time. Figure2 illustrates the maintenance of the base thermodynamics of the same cell after these high-rate discharges, exhibiting the stability of the LiK0.1Mn1.8Co0.2O4 chemistry. An Li \\ LiK0.1Mn1.8Co0.2O4 cell was additionally shown to withstand a deep discharge test down to 2.5 V in Figure 3, and a pulse cycling test in Figure 4. Following each abusive test, the cell’s capacity returned to its previous value when cycled at baseline conditions, showing the stabilizing effect of the spinel’s modifications on capacity retention. Doping the LiMn2O4 spinel with potassium in the A site and cobalt in the B site proved to be a promising chemistry to prevent cathodic capacity fading in a lithium-ion cell, as well as a capable abuse tolerant option for use in rechargeable battery applications. Figure 1

A novel mechanistic modeling framework for analysis of electrode balancing and degradation modes in commercial lithium-ion cells

Abstract Aiming at a long-term stable and safe operation of rechargeable lithium-ion cells, elementary design aspects and degradation phenomena have to be considered depending on the specific application. Among the degrees of freedom in cell design, electrode balancing is of particular interest and has a distinct effect on useable capacity and voltage range. Concerning intrinsic degradation modes, understanding the underlying electrochemical processes and tracing the overall degradation history are the most crucial tasks. In this study, a model-based, minimal parameter framework for combined elucidation of electrode balancing and degradation pathways in commercial lithium-ion cells is introduced. The framework rests upon the simulation of full cell voltage profiles from the superposition of equivalent, artificially degraded half-cell profiles and allows to separate aging contributions from loss of available lithium and active materials in both electrodes. A physically meaningful coupling between thermodynamic and kinetic degradation modes based on the correlation between altered impedance features and loss of available lithium as well as loss of active material is proposed and validated by a low temperature degradation profile examined in one of our recent publications. The coupled framework is able to determine the electrode balancing within an error range of

An Efficient and Controllable Prelithiation of Silicon Monoxide for Improving Energy Density of Lithium-Ion Rechargeable Full Cells

High capacity silicon (Si) anodes are expected to play a key role in increasing the energy density of current lithium-ion batteries (LIBs). In spite of this attractive feature, its huge volume change over repeated cycles impairs the cycle life through pulverization, film delamination, and unstable solid-electrolyte-interphase (SEI) formation, and thereby hinders its practical applications. As an alternative approach, silicon monoxide (SiOx) phase has been recently adopted because its SiO2 background matrix can buffer the volume expansion of inner Si nano-domains. Nonetheless, most of these phases suffer from inferior performance, namely initial Coulombic efficiency (ICE). This shortcoming originates from Li ion trapping in the matrix and SEI layer formation during the first lithiation. In an attempt to catch the two challenging rabbits (cycle life and ICE), the current study has developed delicately controlled pre-lithiation for SiOx anodes. It should be first noted that a proper degree of lithiation is very critical for stable full-cell operations. We pre-lithiate the pristine electrode via an electrical short with Li metal foil in the presence of an optimized circuit resistance while simultaneously monitoring the voltage between both electrodes. Utilizing a fine-tuning capability in the degree of lithiation, a pre-lithiation condition that simultaneously maximizes the ICE and cycle life was found and was also engaged for robust full-cell operations by pairing with a commercially available high capacity cathode. The accurate shorting time and voltage monitoring allow a fine tuning on the degree of pre-lithiation without lithium plating, to a level that the initial CE reaches 94.9%. The excellent reversibility enables robust full-cell operations in pairing with an emerging nickel-rich layered cathode, Li[Ni0.8Co0.15Al0.05]O2, leading to a full cell energy density 1.5 times as high as that of graphite-LiCoO2 counterpart in terms of the active material weight. The given procedure is compatible with the existing roll-to-roll manufacturing line and so must be immediately applicable to the current state of the art LIB anodes containing certain contents of SiOx. Figure 1. Electrochemical characterization of c-SiOx/ Li[Ni0.8Co0.15Al0.05]O2 full cells mad e of the pristine and 30 min pre-lithiated c-SiOx. (a) Voltage profiles of the first cycles. (b) Cycling performance, with regard to the areal capacity. Figure 1

Modeling Investigation of Influencing Factors on Li Plating of Li-Ion Battery

Lithium plating is a known issue of rechargeable lithium-ion cells with carbon-based anodes. Accumulated metallic lithium plating growth accelerates aging and internal short circuit failures. Preventing lithium plating is an important consideration for cell design and operations. In real world applications, the cells in battery pack will age and very likely they age differently and sometimes they are used in extreme conditions and then it raises questions of how to detect and control lithium plating in service. A variety of factors influence lithium plating including cell design variables, intrinsic material properties, manufacturing conditions, as well as cell operation conditions. Understanding these factors has significant value in points of view of design and controls. Where are the optimization rooms in battery design without raising plating risks? How to determine the charging current limits as function of temperature, state of charge and battery conditions? Using experimental means to investigate plating has limitations in sensitivity and timeliness because in many scenarios plating does not show up in a detectable quantity and sometimes they are not stable. In this work, we develop a model to consider lithium plating. In the framework of electrochemical modeling the lithium plating reaction is included. The model is used to study lithium plating upon various design variables and application conditions. We are interested in how coating thickness, particle size characteristics, pulse current and duration, and driving cycles affect lithium plating. The aim of this modeling is to understand the relative impacts of these factors and provide guidance for cell designs and controls.

Energetics of lithium ion battery failure

The energy released by failure of rechargeable 18-mm diameter by 65-mm long cylindrical (18650) lithium ion cells/batteries was measured in a bomb calorimeter for 4 different commercial cathode chemistries over the full range of charge using a method developed for this purpose. Thermal runaway was induced by electrical resistance (Joule) heating of the cell in the nitrogen-filled pressure vessel (bomb) to preclude combustion. The total energy released by cell failure, ΔHf, was assumed to be comprised of the stored electrical energy E (cell potential×charge) and the chemical energy of mixing, reaction and thermal decomposition of the cell components, ΔUrxn. The contribution of E and ΔUrxn to ΔHf was determined and the mass of volatile, combustible thermal decomposition products was measured in an effort to characterize the fire safety hazard of rechargeable lithium ion cells.

Phenomenological force and swelling models for rechargeable lithium-ion battery cells

Three phenomenological force and swelling models are developed to predict mechanical phenomena caused by Li-ion intercalation: a 1-D force model, a 1st order relaxation model, and a 3-D swelling model. The 1-D force model can estimate the Li-ion intercalation induced force for actual pack conditions with preloads. The model incorporates a nonlinear elastic stiffness to capture the mechanical consequences of Li-ion intercalation swelling. The model also separates the entire state of charge range into three regions considering phase transitions. The 1st order relaxation model predicts dynamic swelling during relaxation periods. A coefficient of relaxation is estimated from dynamic and quasi-static swelling at operational conditions. The 3-D swelling model predicts the swelling shape on the battery surface for all states of charge. This model introduces an equivalent modulus of elasticity, which is dependent on the state of charge, to capture material transformations of the electrodes, and the orthotropic expansion of the jellyroll in a direction perpendicular to the electrode surfaces. Considering the simplicity of the measurements and direct physical correlations between stress and strain, the proposed models can enhance battery management systems and power management strategies.

Controlled Prelithiation of Silicon Monoxide for High Performance Lithium-Ion Rechargeable Full Cells.

Despite the recent considerable progress, the reversibility and cycle life of silicon anodes in lithium-ion batteries are yet to be improved further to meet the commercial standards. The current major industry, instead, adopts silicon monoxide (SiOx, x ≈ 1), as this phase can accommodate the volume change of embedded Si nanodomains via the silicon oxide matrix. However, the poor Coulombic efficiencies (CEs) in the early period of cycling limit the content of SiOx, usually below 10 wt % in a composite electrode with graphite. Here, we introduce a scalable but delicate prelithiation scheme based on electrical shorting with lithium metal foil. The accurate shorting time and voltage monitoring allow a fine-tuning on the degree of prelithiation without lithium plating, to a level that the CEs in the first three cycles reach 94.9%, 95.7%, and 97.2%. The excellent reversibility enables robust full-cell operations in pairing with an emerging nickel-rich layered cathode, Li[Ni0.8Co0.15Al0.05]O2, even at a commercial level of initial areal capacity of 2.4 mAh cm(-2), leading to a full cell energy density 1.5-times as high as that of graphite-LiCoO2 counterpart in terms of the active material weight.

A novel thermal swelling model for a rechargeable lithium-ion battery cell

The thermal swelling of rechargeable lithium-ion battery cells is investigated as a function of the charge state and the charge/discharge rate. The thermal swelling shows significant dependency on the state of charge and the charge rate. The thermal swelling follows a quadratic form at low temperatures, and shows linear characteristics with respect to temperature at high temperatures in free-swelling conditions. Moreover, the equivalent coefficient of thermal expansion is much larger than that of each electrode and host materials, suggesting that the separator and the complex shape of the cell play a critical role in thermal expansion. Based on the experimental characterization, a novel thermal swelling model is proposed. The model introduces an equivalent coefficient of thermal expansion for the cell and also considers the temperature distribution throughout the battery by using heat transfer theory. The comparison between the proposed model and experiments demonstrates that the model accurately predicts thermal swelling at a variety of charge/discharge rates during operation and relaxation periods. The model is relatively simple yet very accurate. Hence, it can be useful for battery management applied to prolong the cycle life of cells and packs.