Commercial Lithium-ion Batteries Research Articles

Regulating surface condition of cotton-derived carbon towards enhanced lithium ion storage behavior

With the advancement of battery technology, graphite as a negative electrode material for commercial lithium-ion batteries (LiBs) is reaching the limit of its capacity, and mesoporous carbon with a larger capacity is regarded as its best alternative. In this paper, waste cotton is used as the carbon source, and KOH and urea are used as pore formers and pore size regulators to prepare uniform mesoporous materials (N-PCC800) with a pore size distribution of 2–5 nm. Compared with the traditional KOH pore-making method, the addition of urea can adjust the pore size upward, thereby increasing the effective number of pores for Li+ insertion. While optimizing the structure, urea can also be used as an additional nitrogen source for the material to enrich the content of heteroatoms and defects, thereby increasing the amount of Li+ adsorbed by porous carbon. As an anode material, N-PCC800 exhibits a stable discharge capacity (1086 mAh g−1 at 100 mA g−1) far exceeding that of graphite. At a current density of 1000 mA g−1, there is still a capacity of 596 mAh g−1 remaining after 1000 cycles, indicating its advantages in rate performance and cycle performance. The optimized pore size and higher nitrogen content endow the carbon material with higher Li+ storage performance, and further kinetic analysis indicates that the increased capacity comes from the increased Li+ insertion. This work proposes a new pore size optimization scheme to obtain high-capacity mesoporous carbon, which provides an effective scheme for the reuse of waste cotton and cotton products and helps achieve the goal of carbon neutrality.

Core-shell structure of polyacrylate-based binder enhancing the wet-adhesion strength and the kinetics of lithium-ion diffusion

Despite constituting only a small fraction of the mass of an electrode, the binder is one of the key components ensuring the long-term durability of lithium-ion batteries (LIBs). The need for higher energy density and superior power characteristics necessitates the enhancement of the adhesion properties of the binder to reduce the binder contents of electrodes. In this study, we synthesized a core-shell structured poly(acrylonitrile-co‑butyl acrylate) binder that exhibits higher adhesion strength, lower kinetic resistance, and higher electrode and cell lithium-ion diffusion coefficients than those of styrene-butadiene rubber, which is widely used in commercial LIBs. The polystyrene (PS) constituting the core enhanced the electrical conductivity, while the lone pairs of electrons of poly(acrylonitrile-co‑butyl acrylate) expedited the lithium ion movement, thereby enhancing the kinetics of LIBs. The adhesion properties were enhanced in the presence of the carbonate-based liquid electrolyte owing to the carboxyl groups introduced by itaconic acid on the shells.

Kinetic and transport characteristics of LiNi0.8Co0.1Mn0.1O2 lithium-ion batteries

A balance must be found between energy density, cost and life for energy-typed lithium-ion batteries. Solving this problem requires a deep understanding of the electrode interface reaction mechanism. In this paper, electrochemical AC impedance spectroscopy (EIS) is used to study the impedance spectrum characteristics of lithium-ion batteries comprising LiNi0.8Co0.1Mn0.1O2 (NCM811) and graphite electrodes separately in a symmetrical battery system under different states of charge and temperature. The de Levie - Finite Length Pore (Ls) element is used to differentiate Li+ diffusion resistance Rion inside the porous electrode and charge transfer process resistance Rct in the Faraday reaction. The dependencies of Rion and Rct on temperature and state of charge (SOC) are obtained. Based on the Rion measurements, we calculate MacMullin number (Nm) and then characterize the difficulty of Li ion transportation of NCM811 and graphite electrodes in one cell. The results indicate directions for improving the power design of commercial energy-typed lithium-ion power batteries.

Study on the combustion behaviors and thermal stability of aging lithium-ion batteries with different states of charge at low pressure

Currently, there are many application scenarios for lithium-ion batteries (LIBs) in high-temperature environments, such as large-scale energy storage, electric vehicles, aviation and so on. However, the fire and explosion risks of LIBs will pose a serious threat to transportation, industry applications, and environment. In this work, hence, considering the influence of ambient pressure, a series of experiments are performed to study the characteristics of thermal runaway (TR) for commercial LIBs with different states of charge (SOCs). Relative to past research on fresh batteries, aging LIBs whether at 100 % SOC condition or at lower SOCs, did not particularly exhibit significant spark ejection. The simultaneous burning flame was vertically upwards and no petal-shaped flame appeared. And the maximum flame temperature of LIBs during TR are 394 °C, 368 °C, 469 °C and 508 °C from 30 % SOC to 100 % SOC, respectively. The maximum flame temperature and average mass loss rate of LIBs show a correlation with SOC. Given that the combustions of gases and most ejected combustibles are significantly affected by the environmental pressure, the modified energy balance equation of the battery during the entire TR process is established to quantitative the relationship between the cell surface temperature and SOC under different environmental conditions. These results will help to further identify the risk of the TR process of LIBs with different SOCs after high-temperature aging, and provide a scientific basis for the transportation and use of batteries.

Polyethylene ceramic separators with semi-interpenetrating polymer network boosting fast-charging cycle capacity retention and safety for lithium-ion batteries

Fast-charging lithium-ion batteries (LIBs) have recently received significant attention. In current commercial LIBs, lithium precipitation frequently occurs under long-term cycling and fast-charging conditions, adversely affecting their cycle capacity retention and safety. The primary cause of lithium precipitation is electrolyte loss during long-term cycling. In this study, a thermoplastic polyurethane/polyurethane acrylate semi-interpenetrating polymer network ceramic separator with high electrolyte retention (200%) and interfacial adhesion (6.6 N) is prepared and without a decrease in the energy density. The LiNi0.8Mn0.1Co0.1O2/graphite batteries fabricated with this separator show excellent electrochemistry properties (300 cycles, 1.5 C, discharge capacity of 3677 mAh, capacity retention of 93%). Furthermore, this study presents a novel strategy to mitigate the issue of lithium precipitation in fast-charging LIBs. Therefore, this functional separator is a promising alternative for the conventional commercial polyvinylidene difluoride separators and provides a new avenue for developing the next generation of fast-charging devices.

State of charge and temperature-dependent impedance spectra regeneration of lithium-ion battery by duplex learning modeling

Impedance spectroscopy is a powerful technique and broadly used for battery characterization. In this study, we introduce a novel machine framework we call the duplex (for paired outputs) that constructs a linear ensemble of the best k models. Several impedance spectra of commercial lithium-ion battery coin cells at various states of charge and ambient temperatures are measured sensitively and compared with the spectra predicted by duplex learning modeling. The average difference between overall experimental and duplex estimated impedance data is approximately 3.374 %. The reliable predictions of battery impedance corresponding to a wide range of frequency are made over several operating conditions. The duplex can also be applied to different types of batteries at diverse operating conditions. Critical advantages of this approach are the speed of predicting the experimental space (the training/testing time for duplex is minimal), the small amount of data required to build the duplex, its performance compared to conventional machine learning techniques, as a new, integral component to battery management systems. All code/data are made freely available.

Research Progress of Cathode Materials for Graphene-based Fuel Cells

Graphite is the most widely used cathode material for commercial lithium-ion batteries at present, and the increasing market demand puts forward higher requirements for lithium storage performance of graphite cathode materials. Graphene is a kind of cathode material with great development potential, and its lithium storage performance is influenced by many factors such as structural characteristics, oxygen-containing functional groups and impurity atoms, which leads to complex lithium storage behavior and mechanism. When the polymer with lithium storage activity is compounded with graphene as cathode material, the lithium storage performance is affected by the reversibility of polymer redox and the composite structure. In this article, the working principle of Li-lon and the lithium intercalation mechanism of graphite are introduced, and the research status and progress of graphite cathode materials in surface modification and structural regulation in recent years are emphatically reviewed.

Composite electrolytes engineered by anion acceptors for boosted high-voltage solid-state lithium metal batteries

Solid-state batteries (SSBs) are considered as the most promising option to replace commercial lithium-ion batteries due to their ability to address the flammability of liquid organic electrolytes and facilitate the energy density of lithium batteries. Herein, by introducing tris(trimethylsilyl) borate (TMSB) as anion acceptors, we successfully develop the light and thin electrolyte (TMSB-PVDF-HFP-LLZTO-LiTFSI, PLFB) with a wide voltage window to couple the lithium metal anode with the high-voltage cathodes. Consequently, as-prepared PLFB can greatly boost the generation of free Li+ and improve the Li+ transference numbers (tLi+=0.92) at room temperature. Moreover, combined with theoretical calculation and experimental results, the changes in the composition and properties of the composite electrolyte membrane with the addition of anionic receptors are systematically studied, which further implies the intrinsic mechanism of the stability difference. In addition, the PLFB-based SSB assembled by LiNi0.8Co0.1Mn0.1O2 cathode and lithium anode exhibits a high capacity retention of 86% after loop 400 cycles. This investigation on boosted battery performance by immobilized anions not only contributes to the directional construction of dendrite-free and lithium-ion permeable interface, but also brings new opportunities for the screening and design of the next generation of high-energy SSBs.

Solvation structure and dynamics of a small ion in an organic electrolyte

Organic carbonates are commonly used as electrolytes in commercial lithium-ion batteries. A detailed interpretation of the solvation structure and dynamics of the electrolyte around ions is necessary to understand the charge/discharge process in batteries. This work combines infrared absorption spectroscopy with quantum chemical calculations and molecular dynamics simulations to decipher the solvation structure of propylene carbonate, a cyclic carbonate, around the dissolved thiocyanate ion. Two dimensional infrared spectroscopy and polarization-selective pump probe spectroscopies have been utilized to extract the timescales of solvent fluctuation and the solute reorientational dynamics. The similarity in the slow timescales for the solute and the solvent dynamics signifies that similar processes control both dynamics.

Fading analyses of commercial lithium-ion batteries with blended cathodes using synchrotron X-ray diffraction measurement and discharge curve analysis

We investigated the fading behavior of commercial lithium-ion batteries with blended cathodes. Synchrotron X-ray diffraction measurements revealed the constituent materials of the blended cathode and the degradation state of the cathode due to particle cracking. A particle model was newly introduced to the discharge curve analysis in order to explain the voltage change due to particle cracking, which is not considered in the conventional discharge curve analyses. Herein, blended cathode and particle models to advance the conventional discharge curve analyses have been presented. We have implemented these models besides basic model within our discharge curve analysis code called VOLCALO (VOLtage CALculation and Optimization). The blended cathode model could reproduce the measured values of the discharge curve of cycled batteries better than the conventional method and obtain a change in blend weight ratio due to degradation. The particle model analysis revealed that considering the particle size change due to particle cracking, changes in the discharge curves near the discharge end could be explained by the increase of surface sites.

Solid state battery, what’s next?

Solid state battery (SSB) has become the most attractive and promising technology in the world. SSB should have superior electrochemical performances and safety than commercial nonaqueous lithium ion batteries and has comparable cost. High speed and high yield production facilities and technologies for SSB should be developed. In this short comment paper, possible strategies for developing practical SSB are suggested. And a roadmap for next batteries is purposed.

Surface modification with Li3PO4 enhances the electrochemical performance of LiNi0.9Co0.05Mn0.05O2 cathode materials for Li-Ion batteries

Although high-nickel cathodes (Ni ≥ 90%) have immense potential for use in lithium-ion batteries (LIBs) because of their high energy densities and low material costs. However, structural instability and poor cycling performance have hampered their applications. In this study, we synthesized LiNi0.9Co0.05Mn0.05O2 (denoted “NCM9055″) cathode materials and coated them with Li3PO4 by using a wet-chemical method. We employed X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy to investigate the effects of Li3PO4 surface modification. The (NH4)2HPO4 precursors reacted with the surface residual lithium compounds of NCM9055 to form amorphous Li3PO4 and this active coating layer improved the chemical stability at the electrode-electrolyte interface by suppressing deleterious surface side reactions. Accordingly, the Li+ ion conductivity, rate capability, and long-term cycling performance of the material improved significantly. Measurements of the electrochemical performance revealed that after 200 cycles at a rate of 1 C and a cut-off voltage of 2.7–4.3 V, the 1 mol% Li3PO4–coated NCM9055 (denoted “1P@NCM9055”) cathode retained 90.2% of its initial discharge capacity (ca. 192.9 mA h g–1), whereas the pristine (NCM9055) retained 74.2% of its initial discharge capacity (ca. 196.8 mA h g–1) at room temperature. Our findings should encourage the development and applications of our as-prepared Ni-rich cathode materials in commercial LIBs.

Constructing novel SiOx hybridization materials by a double-layer interface engineering for high-performance lithium-ion batteries

SiOx-based anode materials (0 < x < 2) have been regarded as an appealing candidate for anode material of commercial Lithium-ion batteries accounting for their ultrahigh theoretical capacity and low cost. However, its large-scale applications have been hampered by the serious volume expansion during repeated cycles, low intrinsic conductivity and unsatisfactory initial Coulombic efficiencies. Herein, to address these inherent deficiencies, a hierarchical SiOx-based anode with double-layer coatings of Sn inner layer and N-doped carbon outer shell is elaborately designed by a facile two-step hydrolysis process and polymer coating technology. Benefiting from the “synergistic effect” between Sn and SiOx at different working potentials and a well-designed double-layer coating structure, the resultant SiOx/C@Sn@NC anode displays excellent electrochemical properties, including an enhanced initial Coulomb efficiency (73.3%) efficiency, higher reversible capacity (991 mAh g−1) and superior long lifespan. Moreover, comprehensive characterization based on the reaction kinetics and structural stability proved that such enhanced ICE and cycling stability of anode material stem from its unique double-layer coating structure and multiple active components, which can significantly improve the diffusion of ion and charge transport, stabilize solid-electrolyte interphase (SEI) layer and absorb the expansion stress of electrode. Therefore, this study provides an efficient and feasible strategy to overcome the limitations of high-capacity SiOx-based anode materials via hybridization design with various active components and a double-layer coating strategy.

Lychee-like TiO2@Fe2O3 Core-Shell Nanostructures with Improved Lithium Storage Properties as Anode Materials for Lithium-Ion Batteries.

In this study, lychee-like TiO2@Fe2O3 microspheres with a core-shell structure have been prepared by coating Fe2O3 on the surface of TiO2 mesoporous microspheres using the homogeneous precipitation method. The structural and micromorphological characterization of TiO2@Fe2O3 microspheres has been carried out using XRD, FE-SEM, and Raman, and the results show that hematite Fe2O3 particles (7.05% of the total mass) are uniformly coated on the surface of anatase TiO2 microspheres, and the specific surface area of this material is 14.72 m2 g-1. The electrochemical performance test results show that after 200 cycles at 0.2 C current density, the specific capacity of TiO2@Fe2O3 anode material increases by 219.3% compared with anatase TiO2, reaching 591.5 mAh g-1; after 500 cycles at 2 C current density, the discharge specific capacity of TiO2@Fe2O3 reaches 273.1 mAh g-1, and its discharge specific capacity, cycle stability, and multiplicity performance are superior to those of commercial graphite. In comparison with anatase TiO2 and hematite Fe2O3, TiO2@Fe2O3 has higher conductivity and lithium-ion diffusion rate, thereby enhancing its rate performance. The electron density of states (DOS) of TiO2@Fe2O3 shows its metallic nature by DFT calculations, revealing the essential reason for the high electronic conductivity of TiO2@Fe2O3. This study presents a novel strategy for identifying suitable anode materials for commercial lithium-ion batteries.

Multifunctional Multilayer Nanospheres for Ion Regulation in Lithium Metal Batteries

Lithium metal anodes have the potential to break through the theoretical energy density bottleneck of commercial lithium ion batteries. However, the solid-electrolyte interphase (SEI) layer generated from the decomposition of traditional lithium metal electrolytes is destroyed during the lithium metal expansion process, resulting in the growth of lithium dendrites and the formation of dead lithium. In this work, multilayer Fe3O4@Al(OH)3@ZnO (FAZ) nanospheres are prepared using a hydrothermal method to modify lithium metal anodes. An SEI layer rich in LiF can be formed in fluorine-poor electrolytes. The battery assembled using FAZ nanospheres remains stable for 100 cycles with Coulombic efficiency up to 98.6%. A battery paired with a LiFePO4 cathode (18.3 mg/cm2) can perform 100 cycles with a capacity retention rate of 87%. This work provides a simple and practical solution for low-fluoride lithium metal battery technology.

Nitrogen-Doped Porous Carbon Nanosheets Based on a Schiff Base Reaction for High-Performance Lithium-Ion Batteries Anode

Lithium-ion batteries (LIBs) have already gained significant attention because they have satisfactory energy density and no memory effect, making them one of the most widely used energy storage systems. In commercial LIBs, graphite is widely used as an anode material due to its excellent electrical conductivity and structural stability; however, as they are limited by their restricted theoretical capacity, there is an urgent need for the development of novel anode materials for LIBs. For this purpose, we designed a nitrogen-doped two-dimensional layered porous carbon material (2D-PNC) based on a covalent organic framework (COF) generated by a Schiff base reaction as a precursor. The characterization analysis results show that 2D-PNC is made of stacked two-dimensional ultra-thin carbon sheets with a porous structure. This unique structure is beneficial for electrolyte impregnation and lithium-ion storage, resulting in excellent electrochemical performance of 2D-PNC, which shows a high specific capacity of 573 mAh g−1 after 380 cycles at 0.5 A g−1. The results show that 2D-PNC provides the possibility of a practical application of high-performance lithium-ion batteries.

High-throughput Li plating quantification for fast-charging battery design

Fast charging of most commercial lithium-ion batteries is limited due to fear of lithium plating on the graphite anode, which is difficult to detect and poses considerable safety risk. Here we demonstrate the power of simple, accessible and high-throughput cycling techniques to quantify irreversible Li plating spanning data from over 200 cells. We first observe the effects of energy density, charge rate, temperature and state of charge on lithium plating, use the results to refine a mature physics-based electrochemical model and provide an interpretable empirical equation for predicting the plating onset state of charge. We then explore the reversibility of lithium plating and its connection to electrolyte design for preventing irreversible Li accumulation. Finally, we design a method to quantify in situ Li plating for commercially relevant graphite|LiNi0.5Mn0.3Co0.2O2 (NMC) cells and compare with results from the experimentally convenient Li|graphite configuration. The hypotheses and abundant data herein were generated primarily with equipment universal to the battery researcher, encouraging further development of innovative testing methods and data processing that enable rapid battery engineering.

Homovalent doping: An efficient strategy of the enhanced TiNb2O7 anode for lithium-ion batteries

The low energy density, unsatisfied cycling performance, potential safety issue and slow charging kinetics of the commercial lithium-ion batteries restrained their further application in the fields of fast charging and long-haul electric vehicles. Monoclinic TiNb2O7 (TNO) with the theoretical capacity of 387 mAh g−1 has been proposed as a high-capacity anode materials to replace Li4Ti5O12. In this work, homovalent doping strategy was used to enhance the electrochemical performance of TiNb2O7 (TNO) by employing Zr to partial substitute Ti through solvothermal method. The doping of Zr4+ ions can enlarge the lattice structure without changing the chemical valence of the original elements, refine and homogenize the grains, improve the electrical conductivity, and accelerate the ion diffusion kinetics, and finally enhance the cycle and rate performance. Specifically, Z0.05-TNO shows initial discharge capacity of as high as 312.2 mAh g−1 at 1 C and 244.8 mAh g−1 at 10 C, and still maintains a high specific capacity of 171.3 mAh g−1 after 800 cycles at 10 C. This study provides a new strategy for high-performance fast-charging energy storage electrodes.

Probing depth-dependent inhomogeneous lithium concentration in thick LiNi0.88Co0.09Al0.03O2 cathodes for lithium-ion batteries

A high energy density is an essential requirement for commercial lithium-ion batteries (LIBs) in electric vehicles (EVs) because it directly affects driving range. In addition, the fast charging performance of LIBs, which determines the charging time, is critical in the EV industry. A common approach to enhance the energy density of LIBs is to increase the active material loading by increasing the electrode thickness. However, there is limited scope for increasing the thickness of LIB electrodes in fast charging operations because the power density characteristics of LIB cells are degraded with increasing electrode thickness. Here, we estimate the lithium concentration distribution within thick LIB cathodes after charging/discharging by studying the work function distribution within the thick electrodes using Kelvin probe force microscopy (KPFM). First, to determine the relationship between the work function and lithium content in LIB cathodes, we measure the work function of thin LiNi0.88Co0.09Al0.03O2 (NCA) electrodes under various state-of-charge (SOC) conditions. From these measurements, it is demonstrated that the work function of the NCA electrodes is proportional to the SOC. The results suggest that the work function measurements obtained using KPFM can be used to estimate the Li concentration of NCA electrodes. Next, we perform depth-dependent KPFM measurements in thick NCA samples, which can provide depth profiles of the work function depending on the C-rate conditions. The work function shows a monotonic increase along the depth direction of the thick NCA cathodes, implying a depth-dependent inhomogeneous distribution of lithium concentrations.

Improving stability of high voltage LiCoO2 by synergetic surface modification via in situ surface conversion

LiCoO2 is a pivotal cathode material that is widely used in commercial lithium ion batteries, which can further increase energy density by charging to high voltages. However, the practical application of LiCoO2 at voltages higher than 4.6 V is hindered by its structural instability and severe interfacial side reactions at a highly delithiated state. Herein, we improve the high-voltage performance of LiCoO2 through a synergetic surface modification with a high-voltage-stable and ionic conductive integrated layer, which is realized by the surface coating and heat annealing of Li2CoP2O7. It is discovered that nano-sized Li2CoP2O7 reacts with LiCoO2 and residual lithium-containing species on the surface at 650 °C to form spinel Co3O4 and Li3PO4, which accounts for the high-voltage-stability and high lithium-ion conductivity. The Li2CoP2O7-modified LiCoO2 delivers a high capacity of 203.8 mAh g−1 at 0.2C and a high capacity retention of 75.4% after 200 cycles with a cut-off voltage of 3.0–4.6 V. Moreover, the modified LiCoO2 exhibits an excellent rate capability of 186.5 mAh g−1 at 5C rate, showing great potential in the application scenarios requiring high energy density and fast charging.