Fast-charging Li-ion Batteries Research Articles

Suppressing Lithium Metal Plating of Graphite Anode with Al2O3 and TiO2 for Fast-Charging Li-Ion Batteries

Suppressing Lithium Metal Plating of Graphite Anode with Al2O3 and TiO2 for Fast-Charging Li-Ion Batteries

Balancing the Ion/Electron Transport of Graphite Anodes by a La-Doped TiNb2O7 Functional Coating for Fast-Charging Li-Ion Batteries.

A functional coating layer (FCL) is widely applied in fast-charging lithium-ion batteries to improve the sluggish Li+ transport kinetics of traditional graphite anodes. However, blindly increasing the Li+ conductivity for FCL reduces the overall electron conductivity of the anodes. Herein, we decoupled the effect of La-doping on TiNb2O7 (TNO) in terms of the phase evolution, Li+/electron transport, and lithiation behavior, and then proposed a promising La0.1TNO FCL with balanced Li+/electron transport for a fast-charging graphite anode. By optimizing the doping concentration of La, more holes are introduced into the TNO as electron carriers without causing lattice distortion, thus maintaining the fast Li+ diffusion channel in TNO. As a result, the graphite with La0.1TNO FCL delivers an excellent capacity of 220.2 mAh g-1 (96.3% retention) after 450 cycles at 3 C, nearly twice that of the unmodified one.

Improving Fast-Charging Capability of High-Voltage Spinel LiNi0.5 Mn1.5 O4 Cathode under Long-Term Cyclability through Co-Doping Strategy.

Co-free spinel LiNi0.5 Mn1.5 O4 (LNMO) is emerging as a promising contender for designing next generation high-energy-density and fast-charging Li-ion batteries, due to its high operating voltage and good Li+ diffusion rate. However, further improvement of the Li+ diffusion ability and simultaneous resolution of Mn dissolution still pose significant challenges for their practical application. To tackle these challenges, a simple co-doping strategy is proposed. Compared to Pure-LNMO, the extended lattice in resulting LNMO-SbF sample provides wider Li+ migration channels, ensuring both enhanced Li+ transport kinetics, and lower energy barrier. Moreover, Sb creating structural pillar and stronger TM─F bond together provides a stabilized spinel structure, which stems from the suppression of detrimental irreversible phase transformation during cycling related to Mn dissolution. Benefiting from the synergistic effect, the LNMO-SbF material exhibits a superior reversible capacity (111.4mAhg-1 at 5C, and 70.2mAhg-1 after 450cycles at 10C) and excellent long-term cycling stability at high current density (69.4% capacity retention at 5C after 1000cycles). Furthermore, the LNMO-SbF//graphite full cell delivers an exceptional retention rate of 96.9% after 300cycles, and provides a high energy density at 3C even with a high loading. This work provides valuable insight into the design of fast-charging cathode materials for future high energy density lithium-ion batteries.

Amorphous CoO/Al2O3/C hybrid as anode material for fast-charging Li-ion batteries

Amorphous CoO/Al2O3/C hybrids were synthesized using a simple pyrolysis method at various temperatures and reagent ratios. At 500 °C, CoO localized from homogenous distribution to quantum dots (∼10 nm) on the Al2O3/C matrix. X-ray photoelectron spectroscopy results suggested that the feed nitrate ions doped the hybrids with pyridinic (398.8 eV) and pyrrolic (400.55 eV) N, which ameliorated the electrochemical performance of the hybrids. The optimum pyrolysis temperature to obtain a reversible capacity of 0.45 Ah g−1 at the 1000th cycle at a current density of 1 A g−1 was 500 °C. However, owing to the polarization electrode, the specific capacity decreased by 54 % after increasing the material mass loading (0.5–3 mg cm−2), which resulted in a maximum areal capacity of 0.78 mAh cm−2. After regulating the C content in the hybrid, the loss in reversible capacity was only 29 % for an eight-fold gain in the mass-loading (0.4–3.2 mg cm−2) and the areal capacity was up to 1.13 mAh cm−2. The specific capacity of the optimized electrode was 0.52 Ah g−1 at the 1000th cycle. In addition, it only lost 28 % of its capacity along with a ten-fold increase in current density (0.2–2 A g−1). In a full cell test involving a LiNi0.8Mn0.1Co0.1O2-based cathode and a CoO/Al2O3/C-based anode, 91 % of the maximum theoretical specific capacity was obtained, whereas the capacity retention at the 100th cycle was 97 %. Electrochemical impedance spectra suggested that small resistances (<38 Ω) and high Li+ diffusivity (5.5–6.8 × 10−11 cm2 s−1) supported the fast-charging properties of the hybrid.

Pillaring Electronic Nano-Wires to Slice T-Nb2 O5 Laminated Particles for Durable Lithium-Ion Batteries.

T-Nb2 O5 characterized by the pronounced intercalation pseudocapacitance effect, is regarded as a promising and alternative anode for fast-charging Li-ion batteries. However, its electrochemical kinetics are still hindered by the absence of sufficient and homogenous conductive wiring inside active microparticles. Herein, an in situ pillaring strategy of electronic nano-wires is proposed to slice T-Nb2 O5 laminated particles for the development of durable and fast-charging anodes for Li-ion batteries. A micro-level layered structure consisting of nano-carbon-inserted T-Nb2 O5 composite flakes is designed and enabled by successive ion exchange, slice exfoliation, in situ polymerization, and carbonization processes. The pillared carbon interlayer (derived from polyaniline) can serve as in-built conductive wires to promote and homogenize electron transfer inside the micro-level particles. The porous structure (formed by the self-assembly of exfoliated flakes) contributes to the improved electrolyte immersion and enhanced lithium migration. Benefitting from the kinetically favorable effects, the modified T-Nb2 O5 anode achieves the high-rate capability (108.4 mAhg-1 at 10 Ag-1 ) and ultralong cycling durability (138 mAhg-1 at 1.0 Ag-1 after 8000 cycles, with an average capacity decaying rate as small as 0.043‰). This work provides an effective strategy of electron wire pillaring with the slicing effect for laminated electrode materials with high tap density.

Understanding How the Suppression of Insertion-Induced Phase Transitions Leads to Fast Charging in Nanoscale LixMoO2.

Fast-charging Li-ion batteries are technologically important for the electrification of transportation and the implementation of grid-scale storage, and additional fundamental understanding of high-rate insertion reactions is necessary to overcome current rate limitations. In particular, phase transformations during ion insertion have been hypothesized to slow charging. Nanoscale materials with modified transformation behavior often show much faster kinetics, but the mechanism for these changes and their specific contribution to fast-charging remain poorly understood. In this work, we combine operando synchrotron X-ray diffraction with electrochemical kinetics analyses to illustrate how nanoscale crystal size leads to suppression of first-order insertion-induced phase transitions and their negative kinetic effects in MoO2, a tunnel structure host material. In electrodes made with micrometer-scale particles, large first-order phase transitions during cycling lower capacity, slow charge storage, and decrease cycle life. In medium-sized nanoporous MoO2, the phase transitions remain first-order, but show a considerably smaller miscibility gap and shorter two-phase coexistence region. Finally, in small MoO2 nanocrystals, the structural evolution during lithiation becomes entirely single-phase/solid-solution. For all nanostructured materials, the changes to the phase transition dynamics lead to dramatic improvements in capacity, rate capability, and cycle life. This work highlights the continuous evolution from a kinetically hindered battery material in bulk form to a fast-charging, pseudocapacitive material through nanoscale size effects. As such, it provides key insight into how phase transitions can be effectively controlled using nanoscale size and emphasizes the importance of these structural dynamics to the fast rate capability observed in nanostructured electrode materials.

Electrochemical reconstruction from mixed-phase nickel niobium to Ni-rich LixNb2O5 towards fast charging Li-ion battery

Fast charging capability is a crucial aspect of next-generation ion battery development, but the ion diffusion rate in existing anode materials is limited. It is necessary to design an anode material with a suitable host structure to effectively promote the ion transport rate. In this study, a novel nickel niobate (Ni4Nb2O9) is proposed as an anode material for lithium-ion battery, and a mixed-phase structure consisting of NiNb2O6 and Ni4Nb2O9 (M-NNO) is creatively constructed based on component engineering. The phase interfaces within the mix phases prove instrumental in facilitating the transmission of lithium ions and electrons. Notably, Ni-rich Ni4Nb2O9 enhances the precipitation of metallic Ni nanoparticles during electrochemical reconstruction, thereby effectively improving the electrical conductivity of the electrode material and enhancing its rate performance. The composite delivers an impressive specific capacity of 216 mAh g−1 at 1C and maintains 98.9 % capacity retention after 1000 cycles at 10C. Moreover, the assembled full-cell with NCM811 as a cathode exhibits 173.1 mAh‍ g−‍1 at current densities of 1C. Therefore, the mixed-phase nickel niobates demonstrate good adaptability and stability in a wide voltage range (0.005–3 V), presenting a new approach for designing high-performance and fast charging lithium battery anodes.

Understanding Internal Short Circuit Caused Thermal Runaway of Li-Ion Cells through in-Situ Diagnosis

Internal short circuit (ISC) caused thermal runaway of Li-ion batteries has been a challenge for decades due to difficulties in prevention and early detection of ISC. This challenge becomes increasingly urgent in recent years with the rapid growth of electric transportation industries which demand large-format, high-energy-density and fast-charging Li-ion batteries. Various ISC triggering methods have been developed to evaluate failure behaviors and advance safety designs of Li-ion cells and batteries. However, in-situ diagnosis is often overlooked in many ISC triggering methods and tests. Considering that ISC is a highly localized and transient phenomenon, in-situ diagnosis is important in understanding if and how an ISC triggers thermal runaway. In this presentation, our work on triggering ISC while simultaneously monitoring critical ISC parameters, such as ISC current, ISC resistance and ISC temperature, will be discussed to demonstrate the importance of in-situ diagnosis in understanding ISC and thermal runaway of Li-ion cells.

Covalently Joined Electrode Architectures for Extreme Fast Charging Li-Ion Batteries

Li-ion batteries are the backbone of all electric vehicles (EVs) in production today [1]. However, they compete poorly against the few-minute refueling time of fossil fuel powered vehicles [2, 3]. To successfully replace fossil fuel powered vehicles, the EV batteries must support charging rates under the 15-minute mark as determined by the eXtreme Fast Charging (XFC) standard defined by the U.S. Department of Energy [4]. When subjected to XFC charging rates, well-known problems of lithium plating and delamination plague graphite anodes due to local potential gradients and binder degradation respectively [5].Our work replaces the traditional polymer binder with conductive titanium carbide interconnects that covalently join graphite particles as well as bond them to the current collector [6]. This new architecture demonstrates ~400% increase in electrical conductivity compared to traditional architectures with polymer binders while maintaining interparticle integrity and improving adhesion. The adhesion and mechanical properties are provided by conductive chemical bonds mitigating delamination as these novel bonds suffer less mechanical and chemical degradation under high current rates than adhesion provided by polymer binders. The improved conductivity was also utilized to form a solid electrolyte interphase (SEI) at rates up to 4C reducing the ionic impedance of the SEI interface significantly [7]. The improved graphite electrodes can sustain 15-minute charge maintaining 80% of the specific capacity of the graphite particles for 800 cycles at commercially relevant loadings. Our studies introduce an effective strategy to engineer Li-ion battery electrode architectures that simultaneously improve electrical and ionic conductivity mitigating lithium plating and delamination under XFC charging rate needed for the mass adoption of EVs. Habib, A.A., S. Motakabber, and M.I. Ibrahimy. A comparative study of electrochemical battery for electric vehicles applications. in 2019 IEEE International Conference on Power, Electrical, and Electronics and Industrial Applications (PEEIACON). 2019. IEEE.Balali, Y. and S. Stegen, Review of energy storage systems for vehicles based on technology, environmental impacts, and costs. Renewable and Sustainable Energy Reviews, 2021. 135: p. 110185.Andwari, A.M., et al., A review of Battery Electric Vehicle technology and readiness levels. Renewable and Sustainable Energy Reviews, 2017. 78: p. 414-430.Dufek, E.J., et al., Developing extreme fast charge battery protocols–A review spanning materials to systems. Journal of Power Sources, 2022: p. 231129.Ahmed, S., et al., Enabling fast charging–A battery technology gap assessment. Journal of Power Sources, 2017. 367: p. 250-262.Rangom, Y., Covalently Joined Carbonaceous and Mettalloid Powders by Carbide-Based Interconnects and Method of Fabrication for High-Performance Electrodes. 2021: United States preliminary patent #63/248,293.Rangom, Y., T.T. Duignan, and X. Zhao, Lithium-ion transport behavior in thin-film graphite electrodes with SEI layers formed at different current densities. ACS Applied Materials & Interfaces, 2021. 13(36): p. 42662-42669. Figure 1

Aligned NMC811 electrodes by functionalized conductive graphite flakes for fast-charging Li-ion battery

In recent years, the demand for high capacity, long cycle life, fast charging, and increased safety lithium-ion batteries has become increasingly urgent, especially in the electric vehicle industry. The specific capacity of Li-ion batteries is growing steadily under the great efforts of researchers. However, fast charging, as one of the key technologies of lithium-ion batteries, is still not fully and efficiently resolved. Electric vehicles now have a sufficient driving range, but they take too long to refill compared to traditional vehicles. Here, we aligned polycrystalline NMC 811 microparticles by functionalized graphitic flakes (conductive graphite KS6) under a rotating magnetic field by 2 steps in the cathode fabrication process and constructed an effective and fast conducting three-dimensional conductive network for both electron and ion transport in the cathode system of a high-rate performance Li-ion battery. We successfully regulate and control the tortuosity and porosity of the NMC811 cathode on the electrode level. The new electrode structure has higher ionic conductivity and higher specific capacity. The specific capacity of the electrode with the new electrode structure is about four times and five times the reference electrode at 5 C and at 10 C, respectively. And, the half-cell of the electrode can be fed with 70 % SOC in a 6-min charge at 5 C.

Breaking Mass Transport Limitations by Iodized Polyacrylonitrile Anodes for Extremely Fast-Charging Lithium-Ion Batteries.

The fast-charging capability of rechargeable batteries is greatly limited by the sluggish ion transport kinetics in anode materials. Here we develop an iodized polyacrylonitrile (I-PAN) anode that can boost the bulk/interphase lithium (Li)-ion diffusion kinetics and accelerate Li-ion desolvation process to realize high-performance fast-charging Li-ion batteries. The iodine immobilized in I-PAN framework expands ion transport channels, compresses the electric double layer, and changes the inner Helmholtz plane to form LiF/LiI-rich solid electrolyte interphase layer. The dissolved iodine ions in the electrolyte self-induced by the interfacial nucleophilic substitution of PF6 - not only promote the Li-ion desolvation process, but also reuse the plated/dead Li formed on the anode under fast-charging conditions. Consequently, the I-PAN anode exhibits a high capacity of 228.5 mAh g-1 (39 % of capacity at 0.5 A g-1 delivered in 18 seconds) and negligible capacity decay for 10000 cycles at 20 A g-1 . The I-PAN||LiNi0.8 Co0.1 Mn0.1 O2 full cell shows excellent fast-charging performance with attractive capacities and negligible capacity decay for 1000 cycles at extremely high rates of 5 C and 10 C (1 C=180 mA g-1 ). We also demonstrate high-performance fast-charging sodium-ion batteries using I-PAN anodes.

In Situ Li-Plating Diagnosis for Fast-Charging Li-Ion Batteries Enabled by Relaxation-Time Detection.

The Li-plating behavior of Li-ion batteries under fast-charging conditions is elusive due to a lack of reliable indicators of the Li-plating onset. In this work, the relaxation time constant of the charge-transfer process (τCT ) is proposed to be promising for the determination of Li-plating onset. A novel pulse/relaxation test method enables rapid access to the τCT of the graphite anode during battery operation, applicable to both half and full batteries. The diagnosis of Li plating at varying temperatures and charging rates enriches the cognition of Li-plating behaviors. Li plating at low temperatures and high charging rates can be avoided because of the battery voltage limitations. Nevertheless, after the onset, severe Li plating evolves rapidly under harsh charging conditions, while the Li-plating process under benign charging conditions is accompanied by a simultaneous Li-intercalation process. The quantitative estimates indicate that Li plating at high temperatures/high charging rates leads to more irreversible capacity losses. This facile method with rational scientific principles can provide inspiration for exploring the safe boundaries of Li-ion batteries.

Low Temperature Niobium Tungsten Oxides as Anodes for Fast Charging Li-Ion Batteries

The development of fast-charging Li-ion batteries is one of the important steps in building electric vehicles that need high power and fast charging. The reduction in the particle size to the nanometre length scale drastically improves the charging rate by increasing the surface area but lowers the volumetric energy density and can potentially result in more rapid degradation of the electrolyte via electrode-catalysed reactions. Recent reports show that niobium tungsten oxides (NbWOs) with µm sized particles serve as good anode materials for Li-ion batteries having high volumetric capacity with good cyclability at high rates while avoiding solid electrolyte interphase formation (SEI). The high rate performance of NbWOs is attributed to the topochemical charge storage mechanism that exhibits (i) minimal, highly reversible structural changes during the charge-discharge cycles, (ii) high Li-ion diffusion coefficients due to the presence of fast conducting tunnels, and (iii) high electronic conductivity upon lithiation.1,2 The NbWOs are known to crystallize into two families of different crystal structures depending on the composition and synthesis conditions. The NbWOs phases can either have tungsten bronze-type structures or block-type structures (commonly referred to as Wadsley-Roth phases). Different NbWO phases are reported in the literature3 which could serve as potential anode materials with better performance.In this work, a series of new NbWO phases have been synthesized at reduced annealing temperatures and the structure of these phases has been established using X-ray and neutron diffraction data. The electrochemical properties of NbWO/Li half cells were examined through a series of galvanostatic (dis)charge tests at varying current rates ranging from 0.2 C to 20 C. The NbWO phases delivers a high reversible capacity of 200 and 130 mAh/g at 0.2C and 10 C respectively vs. Li metal. Here we use operando powder X-ray diffraction to investigate the structural changes occurring at the anode during the charge-discharge process in the newly synthesised NbWO phases. Reference s : 1 K. J. Griffith, K. M. Wiaderek, G. Cibin, L. E. Marbella and C. P. Grey, Nature, 2018, 559, 556–563.2 C. P. Koçer, K. J. Griffith, C. P. Grey and A. J. Morris, Chem. Mater., 2020, 32, 3980–3989.3 N. C. Stephenson, Acta Crystallogr. Sect. B Struct. Crystallogr. Cryst. Chem., 1968, 24, 637–653. Figure 1

Relating Crystallographic Shear to Rate Performance in Wadsely-Roth Materials

Wadsley-Roth shear structures represent a promising and high performance class of high-voltage Nb- and W-based anode materials that intrinsically avoid SEI formation, are capable of mulitelectron redox, and suppress large lattice expansion. Currently, there is huge momentum to design faster charging batteries. Wadsley-Roth materials, typically described by their block size, have been found to display outstanding charge storage at fast rates. Within this class of materials, however, there is significant diversity in terms of block size and block arrangement. It is understood that these materials as a class are all generally high performance, but what differentiates them between each other and why? Through data aggregation and visualization, we quantitatively relate the role of shear to rate performance. We find that the structures which have block arrangements with lower amounts edge-sharing polyhedra are capable of higher capacity retention at fast rates. Our findings suggest there is an optimal amount of shear for high-rate Wadsley-Roth materials, too little and the structure will have insufficient stability, too much and the structure will have insufficient channels for Li transport. We develop more nuanced understanding on the relationship between crystallographic features and high-rate properties, informing future material design strategies for fast-charging Li-ion batteries.

Experimental studies of a static flow immersion cooling system for fast-charging Li-ion batteries

ABSTRACT This study explores the performance of a steady-state flow single-phase non-conductive liquid immersion cooling system in a single-cell Li-ion battery under a variety of thermal environments such as 25°C, 40°C, and 60°C and tested at different charge C-rates. The experimental results show that the proposed cooling system exhibited the best cooling performance of less than 5°C and a significant temperature rise reduction of 34% at 3C rate under the ambient temperature of 25°C. Also, it provided uniform temperature distribution within the cell when charged at fast charge rates of 2C and 3C operations.

Particle size effect of graphite anodes on performance of fast charging Li-ion batteries

This study reports the effect of particle size on rate capabilities and provides insights into the design and fabrication of anode materials for fast charging applications.

Recent achievements toward the development of Ni-based layered oxide cathodes for fast-charging Li-ion batteries.

The driving mileage of electric vehicles (EVs) has been substantially improved in recent years with the adoption of Ni-based layered oxide materials as the battery cathode. The average charging period of EVs is still time-consuming, compared with the short refueling time of an internal combustion engine vehicle. With the guidance from the United States Department of Energy, the charging time of refilling 60% of the battery capacity should be less than 6 min for EVs, indicating that the corresponding charging rate for the cathode materials is to be greater than 6C. However, the sluggish kinetic conditions and insufficient thermal stability of the Ni-based layered oxide materials hinder further application in fast-charging operations. Most of the recent review articles regarding Ni-based layered oxide materials as cathodes for lithium-ion batteries (LIBs) only touch degradation mechanisms under slow charging conditions. Of note, the fading mechanisms of the cathode materials for fast-charging, of which the importance abruptly increases due to the development of electric vehicles, may be significantly different from those of slow charging conditions. There are a few review articles regarding fast-charging; however, their perspectives are limited mostly to battery thermal management simulations, lacking experimental validations such as microscale structure degradations of Ni-based layered oxide cathode materials. In this review, a general and fundamental definition of fast-charging is discussed at first, and then we summarize the rate capability required in EVs and the electrochemical and kinetic properties of Ni-based layered oxide cathode materials. Next, the degradation mechanisms of LIBs leveraging Ni-based cathodes under fast-charging operation are systematically discussed from the electrode scale to the particle scale and finally the atom scale (lattice oxygen-level investigation). Then, various strategies to achieve higher rate capability, such as optimizing the synthesis process of cathode particles, fabricating single-crystalline particles, employing electrolyte additives, doping foreign ions, coating protective layers, and engineering the cathode architecture, are detailed. All these strategies need to be considered to enhance the electrochemical performance of Ni-based oxide cathode materials under fast-charging conditions.

Soccerene-like Li4Ti5O12/C as anode materials for fast-charging Li-ion batteries

Li4Ti5O12 (LTO) with great promising anode material for Li-ion batteries (LIBs) has attracted extensive attention, while the large-scale application is hampered owing to the low electronic conductivity and Li+ diffusion coefficient. Herein, the carbon-coated LTO with a unique soccerene-like structure is constructed to simultaneously improve the electron and ion transport by the simple and scalable soft template method. The as-obtained LTO/C material exhibits unique soccerene-like morphology with a large specific surface area and abundant open channels, which can endow the rapid diffusion for Li+ and electrons, and provide more favorable paths for penetration of the electrolyte. Besides, the carbon layer (about 3 nm) on the surface of LTO material can improve the electronic conductivity. Therefore, the LTO/C shows superior electrochemical performance, especially at high-rate discharging.The composite delivers remarkable discharge-specific capacities of 175.42, 170.45, 165.76, 158.90, 153.13, 147.32, 138.64, and 126.95 mA h g−1 at 0.2, 1, 3, 5, 10, 20, 40, and 80C, respectively as well as excellent cyclic stability at 20C with high capacity retention of 99.5 % over 1008 cycles. The composite with a unique soccerene-like structure provides a good prospect for the design of anode material for Li-ion batteries with high rate and long cycling life.

(Digital Presentation) Electrochemical Behavior of Ionic Liquid Modified of Lithium Bis(fluorosulfonyl)Imide Based Electrolyte for Lithium-Ion Batteries

The high efficient energy storage, lithium-ion batteries (LIBs) is accounted as one of the most important storage devices to facilitate the transition of renewable energy conversion. The electrolyte component is the most important in deciding the capacity of LIBs. Lithium bis(fluorosulfonyl)imide (LiFSI) is recently considered as promising conducting electrolyte salt for LIBs because it shows enabling high voltage, high energy density, long cycle life, and accelerates the fast-charging Li-ion batteries. Generally, Additionally, LiFSI and LiPF6 based electrolyte are used in the most of commercial LIBs. Last few years, LiFSI is regarded as an alternative electrolyte to the classical LiFP6 due to its high ionic conductivity, good thermal stability, and HF free nature. In this work, the controlled mixing of ionic liquids (ILs) (imidazolium salts and pyridinium salts) in LiFSI electrolyte was carried out to enhance the ionic conductivity, thermal stability, viscosity, and solubility in organic solvents. The ILs modified LiFSI electrolyte was prepared by adding a constant 1.0 M LiFSI and varying the concentration of ILs from 5 to 20% volume in trimethyl phosphate (TMP). After the modification by ILs, the ionic conductivity of LiFSI electrolyte (10.623 mS/cm) was considerably increased as compared to LiFSI only. The flammability test of electrolyte revealed that ILs modified LiFSI electrolyte was non-flammable, indicating excellent stability in any circumstances. The prepared ILs modified LiFSI electrolyte was used to fabricate coin cell LIBs using double-coated side electrodes (both CMS graphite/Li-NCM (5:2:3) and CMS graphite/LiFePO4). From GCD analysis, the fabricated LIBs with ILs modified LiFSI electrolyte showed a significant improvement in the charging/discharging ability as compared to commercial LIBs with LiPF6 electrolyte. This study manifests that the modification of LiFSI by novel ILs would be promising to achieve highly efficient liquid electrolytes for high performance LIBs.

(Invited) 4C 15-Minute Fast-Charging Li-Ion Battery Enabled By Novel Electrolytes

Electrifying our transportation is one key step to decrease human society’s fossil fuel consumption, therefore, reducing CO2 emissions. In the past decade, electric vehicles (EVs), especially electric passenger cars, are successfully commercialized and are gaining increasing market shares. Most of these EVs are powered by Li-ion batteries (LiBs) due to their high performance over other alternative vehicle power sources. After three decades of development, the energy density of LiBs has steadily increased to >250 Wh/kg at the cell level, which enables EVs with a comparable drive range to their gasoline counterparts. However, the charging time of LiBs is much longer than the refueling of a gasoline tank. The current battery technology can only achieve 80% charge for >30-40 minutes at a high temperature (40-50°C), which falls short of the U.S. Department of Energy (DOE)’s target of 80% charge within 10 minutes. Achieving such a super-fast charging performance without degrading battery life is a challenge that still has not been solved.In this talk, I will discuss our latest findings that by engineering the composition of the electrolyte, the charging performance of LiB can be significantly enhanced. When compared with the commercial carbonate electrolytes (1M LiPF6 in EC-DMC, LP30; or 1M LiPF6 in EC-EMC, LP50), our electrolytes show remarkably better charging performance at all charging rate > 1C. Some formulation of our electrolyte is able to deliver >80% charge at 4C rate within 15 minutes at room temperature. I will discuss our fundamental study to understand the mechanisms underlying the remarkable charging performance of our electrolytes compared to the commercial carbonate electrolytes.