Electrochemical Performance For Lithium-ion Batteries Research Articles

Upscaling of the Laser Structuring of Lithium-Ion Battery Electrodes - Process Development and Electrochemical Properties As a Function of Design Patterns

Structuring of electrodes for lithium-ion batteries by using ultrashort pulsed laser ablation is a quite promising approach to significantly increase the electrochemical performance of lithium-ion batteries. The main impact of such 3D electrodes is due to shortening of lithium-ion diffusion pathways and improving the electrolyte wetting of composite electrodes The latter is reducing the electrolyte filling process time and saving the need for warm aging in the manufacturing process. The 3D electrode concept, in combination with an increase in electrode layer thickness, facilitates an increase in energy and power density of batteries at the same time. To implement the laser structuring process in industrial cell manufacturing, an adaptation of the ultrafast laser technology to the coating speed has to be established.In the presented study, the use of an ultrashort pulsed laser system of high power up to 300 W and high repetition rate in the MHz regime was evaluated regarding processing speed for patterning of graphite and silicon/graphite anodes. For composite graphite anodes (film thickness > 76 µm) with an areal capacity of about 2.5 – 4.0 mAh/cm2 and a thick-film silicon/graphite anode with 5 wt.% silicon content (film thickness 80 µm, areal capacity 4.3 mAh/cm2) the laser and process parameters and processing speed were evaluated and optimized. Furthermore, different structure patterns including hole, grid and line pattern, were studied regarding upscaling in roll-to-roll processing. The different types of patterns were evaluated with respect to accessible electrochemical properties. Prior to cell assembly and during post-mortem studies, the quality of structured electrodes was examined by profilometry and scanning electron microscopy. Debris formation and a thermal impact to active material and current collector could be avoided. To evaluate the electrochemical properties such as high rate capability, cell impedance, and cell lifetime, coin cells and pouch cells were manufactured. For this purpose, NMC 622 cathodes were prepared as the respective counter-electrodes and a cell balancing in the range of 1.1-1.2 was ensured.

(Digital Presentation) Role of Phosphorus Doping on Silicon Anode Performance in Lithium-Ion Batteries Via Facile Solid-State Synthesis

Lithiated silicon (Li15Si4) has a theoretical specific capacity of 3579 mAh g-1 compared to 372 mAh g-1 for graphite at conventional conditions. However, the large volume fluctuations during (de)lithiation result in irreversible damage to the solid-electrolyte interphase (SEI) and then gradual capacity loss as the electrolyte is reduced to reform the surface passivation layer in each cycle. One approach to mitigate this issue is to develop an artificial SEI layer on the silicon surface to limit strain-induced fracture during cycling. The approach presented herein is unique in that both surface functionalization and homogenous doping of the silicon are simultaneously achieved by introducing a trace amount of phosphorus via facile solid-state synthesis. Increased thermodynamic stability of the Li-P-Si ternaries as evidenced in previous studies has been corroborated herein, showing that the P-doped lithium silicide exhibits a contracted crystal lattice which both reduces the Li+ mobility and suppresses the chemical reaction between lithium silicide and typical organic electrolytes. The effect of P-doping, specifically the doping amount and depth within the silicon particles, on the electrochemical performance in lithium-ion batteries was investigated. In conclusion, the solid-state reaction between red phosphorus and nanoparticulate silicon is a relatively simple and tunable method enabling versatile studies of the interfacial chemistry of silicon electrodes over hundreds of cycles.

A Novel High-Performance TiO2-x /TiO1-y Ny Coating Material for Silicon Anode in Lithium-Ion Batteries.

Protective surface coatings on Si anodes are promising for improving the electrochemical performance of lithium-ion batteries (LIBs). Nevertheless, most coating materials have severe issues, including low initial coulombic efficiency, structural fracture, morphology control, and complicated synthetic processing. In this study, a multifunctional TiO2- x /TiO1- y Ny (TTN) formed via a facile and scalable synthetic process is applied as a coating material for Si anodes. A thin layer of amorphous TiO2 is uniformly coated onto Si nanoparticles by a simple sol-gel method and then converted into a two phase TiO2- x /TiO1- y Ny via nitridation. The lithiated TiO2-x provides high ionic and electrical conductivity, while TiO1-y Ny can improve mechanical strength that alleviates volume change of Si to address capacity fading issue. Owing to these synergetic advantages, TiO2- x /TiO1- y Ny -coated Si (Si@TTN) exhibits excellent electrochemical properties, including a high charge capacity of 1650mAhg-1 at 0.1Ag-1 and 84% capacity retention after 100 cycles at 1Ag-1 . Moreover, a significantly enhanced rate performance can be achieved at a high current density. This investigation presents a facile and effective coating material to use as the high-capacity silicon anode in the emerging Si anode technology in LIBs.

High-areal-capacity of micron-sized silicon anodes in lithium-ion batteries by using wrinkled-multilayered-graphenes

Even nanostructured Si electrodes have demonstrated stable electrochemical performances in lithium-ion batteries (LIBs), complex process and high-cost of nanostructured Si electrodes are far from industry standards. Thus, utilization of commercially available low-cost Si microparticles with high-performance is highly necessary for high-energy-density LIBs. Herein, we demonstrate a simple and scalable method to utilize commercially available Si microparticles (ca. 7 μm) with wrinkled-multilayered-graphenes (Si-WMGs) for high-areal-capacity LIBs. The WMGs provide not only mechanical flexibility for mitigating large volume change of Si microparticles during deep charge/discharge processes, but also good adhesion property to effectively coalesce Si microparticles, and high electrical conductivity, resulting in binder- and conductor-free thick electrodes. The Si-WMG electrodes showed high initial areal capacities of 12.5 mAh cm−2 at 0.1 C and 7.1 mAh cm−2 even at a very high rate of 2 C, with outstanding long-term stability with 5.3 mAh cm−2 at 2 C for over 240 cycles. Furthermore, a full cell composed of Si-WMG and lithium cobalt oxide presented 3.13 mAh cm−2 and a stable cycling performance (90.3% retention after 100 cycles) in a practical cell setting, clearly demonstrating the practical applicability of Si-WMG electrodes. Therefore, the WMG as a binder and conductor could be applicable to other electrodes with a large volume change and high mass-loading for high-areal-capacity LIBs.

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.

Effect of porous structure and morphology of cathode on the degradation of lithium-ion batteries

This study investigates the effect of the micromorphology of cathodes with 3D porous structures and geometries on the degradation and electrochemical performance of lithium-ion batteries. Active particle aggregates with different particle diameters and volume fractions are randomly positioned to generate a 3D structure of the cathode in simulation. A physics-based electrochemical model that describes the degradation of the separator, anode, and cathode is developed. Simulation results show that aggregates with a smaller particle radius have a larger surface area, which leads to a higher capacity with a lower concentration gradient but also severe overall degradation. However, with a larger surface area, the volume fraction of the cathode decreases faster, whereas that of the anode decreases slower because of the difference in the fundamental degradation mechanisms of both electrodes. These results indicate that a cathode with a smaller surface area and an anode with a larger surface area are preferred to minimize battery degradation. This morphological information also impacts the diffusivity, which must be carefully optimized for maximizing the capacity and minimizing the degradation. The model developed in this study is expected to be useful to understand degradation mechanisms and to optimize battery design and manufacturing.

Li1.4Al0.4Ti1.6(PO4)3 coated Li1.2Ni0.13Co0.13Mn0.54O2 for enhancing electrochemical performance of lithium-ion batteries

Li1.4Al0.4Ti1.6(PO4)3 coated Li1.2Ni0.13Co0.13Mn0.54O2 for enhancing electrochemical performance of lithium-ion batteries

New insight into the interface of TiO2/C as nanocomposite electrode for lithium-ion batteries

Coating the carbon layer onto the surface of TiO2 electrode is seen as an effective strategy to improve the electrochemical performance of lithium-ion batteries, particularly the reduced charge transfer resistance. The reduced charge transfer resistance was attributed to the chemical bonding between the phases. In this paper, however, we show that it is not only the chemical bonding but also the change of the activation energy differences that is responsible. Herein, we fabricate the carbon layer coated TiO2 electrode (TiO2/C) and combine the recently proposed modified Planck-Nernst-Poisson coupled Frumkin-Butler-Volmer (MPNP-FBV) model to address the above-mentioned issues. By combining the experimental results with the electrochemical model, the charge transfer resistance and the interface behaviors are analyzed. The results show that the performance of TiO2/C electrode based cells is determined by the carbon layer/TiO2 interface, while the cells based on TiO2 electrodes are limited by the electrolyte/TiO2 interface. Comparison between the electrochemical simulations and the experimental data indicates that this increased activation energy difference leads to the decrease of the charge transfer resistance. These results imply that activation energy difference across the interfaces can be a critical parameter for designing high performance batteries.

Novel Method for Monitoring the Electrochemical Capacitance by In Situ Impedance Spectroscopy as Indicator for Particle Cracking of Nickel-Rich NCMs: Part III. Development of a Simplified Measurement Setup

As the optimization of the electrochemical performance of lithium-ion batteries by the adjustment of the composition of the cathode active materials (CAMs) has come to a limit, the focus has shifted to the modification of the morphological aspects. However, new methodologies for the quantification of characteristics such as particle size, particle cracking, and surface area change are needed. A previously reported impedance-based method allows for monitoring the capacitance of CAMs in the positive electrodes as indicator for their surface area but relies on a sophisticated cell setup. In this study, we deduce a stepwise simplification of the capacitance measurements from the setup using a gold-wire reference electrode to a conventional coin half-cell setup, which is commonly used in industry as testing platform for the initial benchmarking of newly developed CAMs. Additionally, it is shown that the CAM capacitance does not have to be extracted from a full impedance spectrum that requires an impedance analyzer, but that it can be obtained solely from a low-frequency single-point impedance measurement, which can be performed with a simple battery cycler. The working principle of this approach is validated using four different cell and electrochemical test hardware configurations (potentiostat, battery cycler) over several charge/discharge cycles.

Conjugated microporous polymer derived N, O and S co-doped sheet-like carbon materials as anode materials for high-performance lithium-ion batteries

Rational design and preparation of nitrogen (N), oxygen (O), and sulfur (S) co-doped materials with distinguished electrochemical performance in lithium-ion batteries are highly sensible. In this study, layered structure carbon material (PTPAO@600) with co-doped N, O and S elements is prepared by carbonizing conjugated microporous polymers (CMPs) as a precursor. When PTPAO@600 electrode material employed as anode of LIBs, and evaluated its properties in electrochemical aspects. After cycling for 800 times under 0.1 A g−1, PTPAO@600 electrode has shown powerful reversible specific capacity of 1142.5 mAh g−1, and excellent rate capability of 275 mAh g−1 at 2.0 A g−1 large current density. Long-cycle performance for 1000 charge/discharge cycles shows that the capacity is retained at 490.9 mAh g−1 under 1.0 A g−1, revealing its high stability. Such high lithium storage performance is mainly attributed to rich heteroatom co-doping, larger specific surface area and high Li+ diffusion coefficient. The superior electrochemical performance makes the PTPAO@600 a anode material with potential in secondary batteries.

Heterogeneous interface in hollow ferroferric oxide/ iron phosphide@carbon spheres towards enhanced Li storage

Heterogeneous interface and structural engineering play important roles for electrochemical performance of lithium-ion batteries. Herein, heterostructures of hollow Fe3O4/FeP spheres coated with carbon shell (H-Fe3O4/FeP@C) are designed to enhance lithium storage performance. As bifunctional anode materials, the H-Fe3O4/FeP@C spheres show the good rate performance with 458.4 mAh g−1 at 5 A g−1 and long-cyclic performance (630.2 mAh g−1 at 2.0 A g−1 after 1000 cycles). Density functional theory calculations demonstrate that the heterogeneous interfaces from (311) plane of Fe3O4 and (002) plane of FeP possess high charge density and distinct metallic character, which can improve the conductivity, increase the adsorption energy, provide more active sites and reduce the transfer barrier of ions and electrons. Besides, hollow structure of H-Fe3O4/FeP@C not only alleviates the volume expansion during lithiation/delithiation process but also shortens the diffusion distance of Li ions. In addition, the ex-situ X-ray diffraction and X-ray photoelectron spectroscopy are used to reveal the electrochemical Li storage mechanisms of H-Fe3O4/FeP@C. This work provides a novel route for design and preparation of Fe-based heterostructures for various energy storage systems in the future.

Effect of coating operating parameters on electrode physical characteristics and final electrochemical performance of lithium-ion batteries

The effect of coating parameters of NMC622 cathodes and graphite anodes on their physical structure and half-cell electrochemical performance is evaluated by design of experiments. Coating parameters include the coater comma bar gap, coating ratio and web speed. The electrochemical properties studied are gravimetric and volumetric capacity, rate performance, areal specific impedance (ASI) and C-rate. Differences in the manufacturing effects on the electrode physical structure and electrochemical performance are observed between the electrodes and are modelled by linear regression. The effect of cell coating weight and porosity on half-coin cell electrochemical performance is also evaluated by linear regression. The cathode performance at high gravimetric and volumetric C-rates is mainly influenced by coating weight, whereas porosity is the only explanatory variable for volumetric C-rates of 1C and below. For anode, correlations are only found for the C/20 and 5C gravimetric and volumetric capacities and are related to coating weight. An inverse relationship between ASI and coating weight is observed for cathode, but in general the cell physical characteristics cannot completely explain the observed ASI for both electrodes. The obtained models are useful for the design and robust manufacturing of electrodes since present a quantitative relationship between the coating parameters, cell characteristics and final cell electrochemical performance.

Strengthened the structural stability of in-situ F− doping Ni-rich LiNi0.8Co0.15Al0.05O2 cathode materials for lithium-ion batteries

Layered Ni-rich oxides have always been considered as highly promising cathode materials for high-energy–density lithium-ion batteries, whereas they have been confronted with technical bottlenecks sprung from short cycle life and thermal instability. In this work, F− doping as one feasible approach has been introduced into LiNi0.8Co0.15Al0.05O2 for alleviating the limitations by stabilizing the layered structure. The stoichiometric LiNi0.8Co0.15Al0.05O2-xFx (0 ≤ x ≤ 0.1) composite powders doped with different amounts of NH4F powders are precisely synthesized by in-situ modified method, which are strictly identified by physicochemical methods. The characterization results demonstrate that F ions successfully enter into the lattice of LiNi0.8Co0.15Al0.05O2-xFx (0 ≤ x ≤ 0.1) and that the targeted LiNi0.8Co0.15Al0.05O1.96F0.04 composite powders possess the most ordered layered structure with compact surface morphology when the doping amount of F− is up to 4 % based on the weight of the precursor Ni0.8Co0.15Al0.05(OH)2 composite powders. Moreover, the half-cell assembled with the LiNi0.8Co0.15Al0.05O1.96F0.04 composite electrode presents a reversible discharge specific capacity of 157.8 mAh g−1 with remarkable capacity retention of 98.3 % after 100cycles at 2.0C at 25 °C. Even at an elevated temperature of 60 °C and a high current density of 5.0C, it still delivers an improved discharge specific capacity of 142.6 mAh g−1 with excellent capacity retention of 89.1 %. The outstanding improvements in the terms of the lithium storage performance are principally attributed to the stronger metal-F bonds substituting the metal-O bonds with introducing F ions into the lattice, which can not only effectively stabilize the host structure to preserve the structural integrity, but also prevent the erosion of HF and suppress the increment of the polarization degree during continuous cycling processes. Therefore, the F− doping strategy may provide a novel horizon to construct layered Ni-rich cathode materials with improved structural stability and durable electrochemical performance for lithium-ion batteries.

Thickness-controllable coating on graphite surface as anode materials using glucose-based suspending solutions for lithium-ion battery

Surface-passivation is an effective way to allow the anode materials can deliver long-term superior electrochemical performance for lithium-ion batteries (LIBs). Herein, we develop a simple solution suspension-coating method to prepare thickness-controllable nano‑carbon layer (NCL) on a synthesis graphite-mesocarbon microbeads (MCMB) using aqueous glucose solutions with a surfactant-triton X-100 at 25 °C. This simple process can control the thickness of the NCL on MCMB with a range of 1.5–20 nm with various glucose concentrations. The as-formed NCL can reduce the defect sites on MCMB surface and create slightly porous structures within NCL. For electrochemical performance in LIB, we observed that the carbon-coating thickness at around 4 nm shows better reversible capacity (from 295 to 347 mAh g−1), lower Li+ diffusion resistance, stable cycle-life, and superior C-rate performance. As our results, we provide a simple method to stabilize surface properties of MCMB and show better electrochemical performance in LIB. Moreover, this method can be easily exploited in the industrial with a massive production.

Fabrication of VO Nanorings on a Porous Carbon Architecture for High-Performance Li-Ion Batteries.

Vanadium monoxide (VO) is a promising candidate as an anode for lithium-ion batteries due to its high theoretical capacity, low cost, and considerable electronic conductivity. Unfortunately, a large volume change during electrochemical processes obstructs its practical application. In this work, a composite of VO nanorings grown on a porous carbon architecture is prepared via a topochemical self-reduction approach. When used as an anode for lithium-ion batteries, improved redox kinetics from enhanced electronic conduction and the corresponding fast lithium-ion diffusion is observed to greatly promote the electrochemical performance of lithium-ion batteries. The resulting composite delivered a reversible capacity of 336 mA h g-1 after 400 cycles at 10 A g-1 with a capacity retention of 85%, owing to the synergistic effect of VO nanorings and porous carbon in alleviating volume changes that result in a long-term cycling ability at a high current density. At 20 A g-1, the composite anode exhibited a rate capability of 235 mA h g-1, superior to all VO-based electrodes reported in the literature. Furthermore, a full cell was first fabricated by employing VO@C-2 as the anode and LiFePO4 as the cathode, which exhibited a capacity of 213 mA h g-1 after 100 cycles at 0.1 A g-1, indicating the potential of VO as an anode for practical application.

New Type of SnSe/CoSe@C Anode for Lithium-Ion Batteries

The design of electrodes with a unique structure has a major impact on boosting the electrochemical performance for lithium-ion batteries. Herein, the SnSe/CoSe@C composite was synthesized by a facile metal–organic framework-engaged method. The carbon layer can improve the stability and conductivity of materials. In addition, SnSe/CoSe heterojunctions can increase the electron transfer rate between interfaces, which will be instrumental in inducing fast electronic/ionic diffusion kinetics. The SnSe/CoSe@C anode retained a high specific capacity of 789 mAh/g at 200 mA/g after 100 cycles. This anode still delivered high capacities of 425 mAh/g at 3000 mA/g.

Functionalization of Graphite Electrodes with Aryl Diazonium Salts for Lithium‐Ion Batteries

AbstractThe functionalization of electrode surfaces is a useful approach to gain a better understanding of solid–electrolyte interphase formation and battery performance in lithium‐ion batteries (LIBs). Electrografting and deprotection of alkyl silyl protected ethynyl aryl diazonium salts on graphite electrodes were performed. Furthermore, electrografting of aryl diazonium salts carrying functional groups such as amino, carboxy and nitro, and their influence on the electrochemical performance in LIBs were investigated. The drawbacks of electrografted and especially deprotected samples were evaluated and compared to corresponding in situ grafted samples. While electrografted samples tend to lower the delithiation capacities, in situ grafted samples, except amino groups, reveal higher capacities. Ethynyl (TMS) shows improved capacities at 1 C and better capacity retention compared to the pristine graphite electrode. Additionally, the Coulombic efficiency of the first cycle was enhanced for in situ grafted samples.

Inducing lattice defects in calcium ferrite anode materials for improved electrochemical performance in lithium-ion batteries

Enhancing the electrical conductivity of electrode materials via a cationic substitution strategy was recognized as an effective way of improving the electrochemical performance of Li-ion batteries. Thus, LixCa1-xFe2O4 nanoparticles were synthesized via a facile inexpensive process at low temperature. XRD peaks refer to the formation of an orthorhombic structure with the Pnma space group. HR-TEM investigations reveal orthorhombic-like shape for pure CaFe2O4, nanoplatelet-like morphology for Li0.05Ca0.95Fe2O4 and irregular distorted crystals for Li0.1Ca0.9Fe2O4. Voids and pores in Li-doped CaFe2O4 were confirmed by FESEM and BET measurements. XPS spectra of O1s prove that Li-doped CaFe2O4 have higher conductivity due to the created lattice defects and oxygen species. Li-doped CaFe2O4 anodes exhibit great improvement in their initial discharge capacities ∼1219 and 1606 mAhg−1 upon substitution of Ca with 5% and 10% Li, respectively. Furthermore, 10% Li-doped CaFe2O4 anode displays the highest Li-ions diffusion coefficient and exchange current density due to the enhanced Li+ ions mobility. Moreover, the DC activation energies for the LixCa1-xFe2O4 nanoparticles decreased with increasing Li content.

Constructing MoS2/ZnS-NC heterostructures on carbon cloth as anode with enhanced diffusion kinetics for lithium-ion batteries

Interface engineering is an effective strategy to optimize the electronic properties of MoS2, yielding significantly improved electrochemical performance of lithium-ion batteries. We have designed carbon cloth (CC) decorated by a MoS2/ZnS-NC heterostructure, where ZnS with N-doped carbon (ZnS-NC) is derived from zeolitic imidazolate framework‐8 (ZIF-8) carbonation. A MoS2/ZnS-NC@CC heterostructure with abundant heterointerfaces, high conductivity, and N heteroatom doping greatly enhances electron/ion diffusion kinetics, thereby improving electrochemical performance. The MoS2/ZnS-NC@CC anode exhibits improved lithium storage capacity due to its structural advantage. Electrochemical measurements reveal that the MoS2/ZnS-NC@CC binder-free electrode delivers an initial discharge capacity of 1427.2 mAh g−1 at a current density of 100 mA g−1 and good cycling stability after 200 cycles.

Preparation of nanorod-assembled CNT-embedded LiMnPO4 hollow microspheres for enhanced electrochemical performance of lithium-ion batteries

The simultaneous enhancement of electron transfer and Li+ migration is of particular importance to achieve high electrochemical performance in lithium-ion batteries.