Fast-charging Li-ion Batteries Research Articles

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.

F-doped orthorhombic Nb2O5 exposed with 97% (100) facet for fast reversible Li+-Intercalation

Orthorhombic Nb2O5 (T-Nb2O5) is attractive for fast-charging Li-ion batteries, but it is still hard to realize rapid charge transfer kinetics for Li-ion storage. Herein, F-doped T-Nb2O5 microflowers (F-Nb2O5) are rationally synthesized through topotactic conversion. Specifically, F-Nb2O5 are assembled by single-crystal nanoflakes with nearly 97% exposed (100) facet, which maximizes the exposure of the feasible Li+ transport pathways along loosely packed 4g atomic layers to the electrolytes, thus effectively enhancing the Li+-intercalation performance. Besides, the band gap of F-Nb2O5 is reduced to 2.87 eV due to the doping of F atoms, leading to enhanced electrical conductivity. The synergetic effects between tailored exposed crystal facets, F-doping, and ultrathin building blocks, speed up the Li+/electron transfer kinetics and improve the pseudocapacitive properties of F-Nb2O5. Therefore, F-Nb2O5 exhibit superior rate capability (210.8 and 164.9 mAh g−1 at 1 and 10 C, respectively) and good long-term 10 C cycling performance (132.7 mAh g−1 after 1500 cycles).

A Figure of Merit for Fast-Charging Li-ion Battery Materials

Rate capability is characterized necessarily in almost all battery-related reports, while there is no universal metric for quantitative comparison. Here, we proposed the characteristic time of diffusion, which mainly combines the effects of diffusion coefficients and geometric sizes, as an easy-to-use figure of merit (FOM) to standardize the comparison of fast-charging battery materials. It offers an indicator to rank the rate capabilities of different battery materials and suggests two general methods to improve the rate capability: decreasing the geometric sizes or increasing the diffusion coefficients. Based on this FOM, more comprehensive FOMs for quantifying the rate capabilities of battery materials are expected by incorporating other processes (interfacial reaction, migration) into the current diffusion-dominated electrochemical model. Combined with Peukert's empirical law, it may characterize rate capabilities of batteries in the future.

The synthesis of novel porous graphene anodes for fast charging and improved electrochemical performance for lithium-ion batteries

ABSTRACT As part of sustainable development goals seven and thirteen, electric vehicles (EV) are taking over internal combustion engine vehicles by using battery packs as their power source. One major concern for the EV sector is the charging time of lithium-ion (Li-ion) batteries. Advancing the battery pack industry and the EV sector will benefit economically and environmentally by creating pores on the graphene anode using the NaCl activation method, eventually leading to high performance and efficiency in Li-ion batteries. Accordingly, the present study focused on fabricating novel macroporous graphene (MPG) anodes for fast-charging Li-ion batteries. Macropores increase the anode surface area, thereby enhancing lithiation. The performance of the novel MPG anode is compared with that of the commercial mesocarbon microbead (MCMB) anode. As a result, the MPG anode exhibits a 15% faster charge than the MCMB at a 0.1 C rate. Moreover, the specific capacity of the MPG anode retains 16.3% higher than the MCMB anode after the completion of the 100th cycle.

Mesoporous Single‐Crystal Lithium Titanate Enabling Fast‐Charging Li‐Ion Batteries (Adv. Mater. 18/2022)

Mesoporous Materials In article number 2109356, Jianming Li, Pengfei Yan, Shuhong Jiao, and co-workers report mesoporous single-crystalline lithium titanate microrods featured with a single-crystalline structure and interconnected pores inside for fast-charging Li-ion batteries (LIBs). The unique structure of lithium titanate enables a short lithium-ion diffusion distance and fast penetration of electrolytes into the electrode interior during battery cycling, which contribute to high-rate capability and excellent cycling stability. The novel design of porous single-crystalline materials paves a new venue for developing fast-charging materials for LIBs.

Low-Temperature Synthesis of Lithium Lanthanum Titanate/Carbon Nanowires for Fast-Charging Li-Ion Batteries.

Due to the lower working voltage and higher capacity, the Li-rich lithium lanthanum titanate perovskite (LLTO) anode is becoming a potential candidate for the commercial Li4Ti5O12 (LTO) Li-ion battery anode [Zhang, L. Lithium Lanthanum Titanate Perovskite as an Anode for Lithium Ion Batteries. Nat. Commun. 2020, 11, 3490]. However, a high temperature of 1250 °C is required to fabricate pure LLTO particles by the conventional solid-phase calcination method, limiting their further practical applications. Here, an in situ carbon nanospace confined method is developed to synthesize the pure LLTO with sub-nanometer grain size at an extremely low temperature of 800 °C. The LLTO precursor is confined in the in situ formed carbon nanowire matrix during heating, resulting in a shorter solid-phase diffusion distance and subsequently lower energy required for the formation of the pure LLTO phase. The low-temperature-synthesized pure LLTO/carbon composite nanowires (P-LLTO/C NWs) exhibit improved lithium storage performances than the traditionally prepared LLTO due to the fast electronic conduction of carbon and the stable carbon surface. In addition, the working potentials of P-LLTO/C||LiFePO4 and P-LLTO/C||LiCoO2 full cells are all 0.7 V higher than that of the corresponding commercial full cells with LTO as an anode, meaning much higher power energy densities (307.6 W kg-1 at 2C and 342.4 W kg-1 at 1C vs 198.4 W kg-1 and 275.2 W kg-1 for LTO||LiFePO4 and LTO||LiCoO2 full cells based on electrode materials, respectively). This low-temperature synthesis method can extend to other solid-state ionic materials and electrode materials for electrochemical devices.

Preparation of biomass-derived hard carbon with uniform ultramicropores for development of fast charging Li-ion batteries

Biomass-based hard carbon is the material of choice for fabricating fast charging anodes. However, their low initial coulombic efficiency (~70%) must be improved to increase energy density. In this study, the pore structure of hard carbon was tuned by pretreatment. The ultramicropores (< 0.4 nm) in modified hard carbon inhibited electrolyte decomposition and enhanced the diffusion kinetics. The hard carbon pretreated at 500 °C under 6 MPa for seven days showed a high capacity retention rate of 82%, despite fast charging and a low irreversible capacity. This strategy can help realize efficient lithium storage and diffusion.

Anisotropic black phosphorene nanotube anodes afford ultrafast kinetic rate or extra capacities for Li-ion batteries

As an important anode material for fast-charging Li-ion batteries (LIBs), black phosphorus (BP) has attracted extensive attention. Black phosphorene nanotubes (BPNTs) can be theoretically produced by rolling up the black phosphorene nanosheet along armchair (a-BPNTs) and zigzag (z-BPNTs) directions. The effects of curvature, chirality, Li-storage concentrations and strain stress on the Li-storage performance such as Li diffusion barriers and mechanical stabilities of BPNTs are mainly investigated by first principles calculations. The theoretical calculations predict that the a-BPNTs and z-BPNTs have good maximum Li-storage capacities, and the z-BPNTs exhibit better flexibility than a-BPNTs. The mechanical stabilities and Li-migration are all related to the curvature of BPNTs. Additionally, both a-BPNTs and z-BPNTs exhibit fast Li-ion conductivity along the c-axis direction. Moreover, the average Poisson's ratio of a-BPNTs (0.68) is larger than that of z-BPNTs (0.17), indicating that the strain stress is more difficult to apply on a-BPNTs than z-BPNTs. Our calculations predict that the a-BPNTs can afford ultrafast kinetic rate for fast-charging and high-power LIBs, while the z-BPNTs can provide extra capacity for high-energy LIBs.

Effect of thermal environments on fast charging Li-ion batteries

Battery thermal management systems (BTMSs) are expected to keep the battery temperature at a moderate level (∼30 °C) to minimize the thermally exacerbated degradation. However, during fast charging, a strong cooling system is required to restrict the temperature rise of Li-ion batteries (LiBs), which significantly increases the cost and weight of battery packs, and induces a large temperature variation inside the battery. In this work we find that all these drawbacks could be relieved by allowing LiBs to charge at higher temperatures. Since the fast charging of a LiB only takes a tiny fraction of its lifetime, the aging rate is limited even at a charging temperature of 60 °C. Three types of thermal environments are proposed: kept constant at 30 °C, preheated to 60 °C, and adiabatic fast charging. With an experimentally validated electrochemical-thermal (ECT) coupled model, we explore the interplay between thermal management and the fast-charging performance. It is found that a gradually increasing temperature profile is the best option to balance the lithium plating and thermal management of the battery. Combining adiabatic fast charging with a preheating step, we can achieve minimal cooling need, perfect temperature uniformity within a battery, and fast-charging capability simultaneously.

A cooperative biphasic MoOx\u2013MoPx promoter enables a fast-charging lithium-ion battery

The realisation of fast-charging lithium-ion batteries with long cycle lifetimes is hindered by the uncontrollable plating of metallic Li on the graphite anode during high-rate charging. Here we report that surface engineering of graphite with a cooperative biphasic MoOx–MoPx promoter improves the charging rate and suppresses Li plating without compromising energy density. We design and synthesise MoOx–MoPx/graphite via controllable and scalable surface engineering, i.e., the deposition of a MoOx nanolayer on the graphite surface, followed by vapour-induced partial phase transformation of MoOx to MoPx. A variety of analytical studies combined with thermodynamic calculations demonstrate that MoOx effectively mitigates the formation of resistive films on the graphite surface, while MoPx hosts Li+ at relatively high potentials via a fast intercalation reaction and plays a dominant role in lowering the Li+ adsorption energy. The MoOx–MoPx/graphite anode exhibits a fast-charging capability (<10 min charging for 80% of the capacity) and stable cycling performance without any signs of Li plating over 300 cycles when coupled with a LiNi0.6Co0.2Mn0.2O2 cathode. Thus, the developed approach paves the way to the design of advanced anode materials for fast-charging Li-ion batteries.

Pathways towards managing cost and degradation risk of fast charging cells with electrical and thermal controls

This work demonstrates pathways toward affordable, fast-charging Li-ion batteries by implementing a constant-risk charging protocol with active thermal management.

Free-standing hybrid films comprising of ultra-dispersed titania nanocrystals and hierarchical conductive network for excellent high rate performance of lithium storage

The construction of advanced electrode materials is key to the field of energy storage. Herein, a free-standing anatase titania (TiO2) nanocrystal/carbon nanotube (CNT) film is reported using a simple and scalable sol-gel method, followed by calcination. This unique free-standing film comprises ultra-small TiO2 nanocrystals (∼ 5.9 nm) and super-aligned CNTs, with ultra-dispersed TiO2 nanocrystals on the surfaces of the CNTs. On the one hand, these TiO2 nanocrystals can significantly decrease the diffusion distance of the charges and on the other hand, the cross-linked CNTs can act as a three-dimensional (3D) conductive network, allowing the fast transport of electrons. In addition, the film is free-standing, without requiring electrode fabrication and additional conductive agents and binders. Owing to these above synergistic effects, the film is directly used as an anode in Li-ion batteries, and delivers a high discharge capacity of ∼ 105 mAh·g−1 at high rate of 60 C (1 C = 170 mA·g−1) and excellent cycling performance over 2,500 cycles at 30 C. These results indicate that the free-standing anatase TiO2 nanocrystal/CNT film affords a superior performance among the various TiO2 materials and can be a promising anode material for fast-charging Li-ion batteries. Moreover, the TiO2/CNT film exhibits an areal capacity of up to 2.4 mAh·cm−2, confirming the possibility of its practical use.

Enabling > 4C Fast Charging of Li-Ion Batteries with Graphite/Hard Carbon Hybrid Anodes to Overcome Energy/Power Density Tradeoffs

Li-ion batteries with high energy density and fast-charge capability are required to realize the widespread use of electric vehicles. However, current graphite-anode-based Li-ion batteries are unable to achieve fast charging without adversely impacting battery performance. This is because when graphite anodes are subjected to fast charging conditions, large cell polarizations reduce the accessible capacity and induce Li plating on the anode surface. The formation of metallic Li on the graphite anode surface results in irreversible loss of Li inventory, leading to significant capacity fade. In contrast to graphite, hard carbon is known to exhibit enhanced power performance. However, the high redox potential, low first-cycle efficiency, and low material density have prevented the adoption of hard carbon in high-energy-density battery systems. Thus, there is a unmet need to develop Li-ion technology to achieve both high energy density and power performance.In this work, we demonstrate hybrid anodes fabricated by mixing graphite and hard carbon to achieve fast-charging Li-ion batteries with high energy density, using industrially relevant multi-layer pouch cells (> 1Ah) and electrode loadings (3 mAh/cm2). Standard roll-to-roll slurry casting was performed to fabricate the hybrid anodes, demonstrating the compatibility with existing Li-ion manufacturing. By tuning the blend ratio of graphite and hard carbon, it is shown that the battery performance can be tailored to simultaneously achieve high energy density and power performance. As a result of the hybrid anode design, we demonstrate pouch cells with > 96% and > 93% capacity retention over 100 cycles of 4C and 6C fast-charge cycling respectively. Synchrotron tomography was employed to investigate the microstructure effects (porosity, tortuosity, and pore size) on the electrochemical performance. Electrochemical dynamic simulations were also performed to provide mechanistic insight into the origins of the improved fast-charging performance of the graphite/hard carbon hybrid anodes.

Using nanoconfinement to inhibit the degradation pathways of conversion-metal oxide anodes for highly stable fast-charging Li-ion batteries

Nanostructured hybrids that physically encapsulate highly morphable, high capacity Li-ion battery anodes can potentially enable much longer cycle life than straightforward deployment of the same chemistry.