Improved Battery Performance Research Articles

Difunctional NH2-modified MOF supporting plentiful ion channels and stable LiF-rich SEI construction via organocatalysis for all-solid-state lithium metal batteries

As an essential part of the performance improvement of lithium metal batteries, the acquisition of dense (LiF-rich solid electrolyte interphase (SEI)) has always been an urgent problem to be solved. Herein, we synthesized Zeolitic Imidazolate Frameworks (ZIFs) modified by two different functional groups (–NH2, –CH3) and used them as the fillers of polyethylene oxide (PEO) composite solid electrolytes to explore the catalytic effect of groups on LiF generation at the Li/electrolytes interface. In a LiFePO4||SPE||Li cell test, the PEO-ZIF-NH2 with LiF-rich SEI exhibits enhanced cycling performance, which was 3.8 times longer than that of PEO-ZIF-CH3. The formation mechanism of LiF-rich SEI was investigated using first-principles calculation, revealing that ZIFs-NH2 makes the C–F bond in TFSI– longer compared with ZIFs-CH3, which leads to easier breakage of the C–F bond and promoted the formation of LiF. The simple design idea of using organic catalysis to generate more stable SEI provides a new aspect for preparing high-performance lithium metal batteries.

Experimental Investigations on the Chemo-Mechanical Coupling in Solid-State Batteries and Electrode Materials

Increasing attention has been paid to the safety and efficiency of batteries due to the rapid development and widespread use of electric vehicles. Solid-state batteries have the advantages of good safety, high energy density, and strong cycle performance, and are recognized as the next generation of power batteries. However, solid-state batteries generate large stress changes due to the volume change of electrode materials during cycling, resulting in pulverization and exfoliation of active materials, fracture of solid-electrolyte interface films, and development of internal cracks in solid electrolytes. As a consequence, the cycle performance of the battery is degraded, or even a short circuit can occur. Therefore, it is important to study the stress changes of solid-state batteries or electrode materials during cycling. This review presents a current overview of chemo-mechanical characterization techniques applied to solid-state batteries and experimental setups. Moreover, some methods to improve the mechanical properties by changing the composition or structure of the electrode materials are also summarized. This review aims to highlight the impact of the stress generated inside solid-state batteries and summarizes a part of the research methods used to study the stress of solid-state batteries, which help improve the design level of solid-state batteries, thereby improving battery performance and safety.

Multi-objective optimum energy management strategies for parallel hybrid electric vehicles: A comparative study

In this study, multi-objective optimum energy management strategies are developed for pre- and post-transmission parallel hybrid electric vehicles. The first strategy aims to improve fuel economy and electric system efficiency, while the second strategy adds the improvement in battery performance and life. Multi-objective genetic algorithm is adopted to solve the formulated optimum energy management problems, hence generates optimum control inputs for each drivetrain configuration. Mathematical models of vehicle dynamics and drivetrain components are integrated with the developed strategies in a simulation environment. Results for both strategies are compared to a baseline rule-based energy management strategy, commonly used as a benchmark in literature. Additionally, both drivetrain configurations are compared and analyzed through different standard driving cycles. The results show the significant improvement in battery performance due to its consideration in the energy management strategy, with either null or positive effect on fuel consumption. Additionally, the results of pre-transmission drivetrain configuration show noticeable improvement in battery performance as compared to the post-transmission results.

Solar-Light-Responsive Zinc-Air Battery with Self-Regulated Charge-Discharge Performance based on Photothermal Effect.

It is extremely challenging to significantly increase the voltaic efficiency, power density, and cycle stability of a Zn-air battery by just adjusting the catalytic performance of the cathode with nanometers/atomistic engineering because of the restriction of thermodynamic equilibrium potential. Herein, inspired by solar batteries, the S-atom-bridged FeNi particles and N-doped hollow carbon nanosphere composite configuration (FeNi-S,N-HCS) is presented as a prototype of muti-functional air electrode material (intrinsic electrocatalytic function and additional photothermal function) for designing photoresponsive all-solid-state Zn-air batteries (PR-ZABs) based on the photothermal effect. The local temperature of the FeNi-S,N-HCS electrode can well respond to the stimuli of sunlight irradiation because of their superior photothermal effect. As expected, under illumination, the power density of the as-fabricated PR-ZABs based on the FeNi-S,N-HCS electrode can be improved from 77 mW cm-2 to 126 mW cm-2. Simultaneously, charge voltage can be dramatically reduced, and cycle lifetime is also prolonged under illumination, because of the expedited electrocatalytic kinetics, the increased electrical conductivity, and the accelerated desorption rate of O2 bubbles from the electrode. By exerting the intrinsic electrocatalytic and photothermal efficiency of the electrode materials, this research paves new ways to improve battery performance from kinetic and thermodynamic perspectives.

Adaptive intelligent hybrid energy management strategy for electric vehicles

AbstractElectric vehicles (EVs) utilizing hybrid energy sources is a significant step toward a sustainable future in the transportation industry. The electric three‐wheeler (3W) considered in the proposed work includes three sources—battery, supercapacitor (SC), and photo‐voltaic (PV) panels. In battery electric vehicles (BEV), battery life cycle, energy efficiency, and performance are affected by variations in driving conditions that inhibit their wider adoption. The main focus of the proposed intelligent hybrid energy management strategy (IHEMS) is to enable the vehicle to adaptively manage and diminish the effects of load fluctuations due to varying conditions. IHEMS diverts the load fluctuations to the SC bank by ensuring an effective absolute energy sharing among the sources with a fuzzy logic control algorithm. PV energy is utilized to assist the battery during sunny days. Performance of the EMS in hybrid source EV is analyzed in MATLAB/SIMULINK environment with a combination of three different standard real‐time driving profiles (NYCC, Artemis Urban, WLTP class‐1). Proposed EMS reduces peak battery power by 20% and 14.35% and improves battery life by 16.4% and 11.4% compared to BEV and conventional EMS, respectively. This proves that the proposed EMS exhibits adaptive energy management irrespective of the driving conditions and ensures improved battery performance and longevity.

Steering the liquid-solid redox conversion of lithium-selenium batteries through ultrafine MoC catalyst.

Selenium cathodes have attracted much attention because of the high electronic conductivity and energy density. However, the shuttle effect of lithium polyselenides (LiPSes) leads to rapid capacity fading, hindering the practical application of lithium-selenium (Li-Se) batteries. Herein, an ultrafine MoC catalyst has been synthesized and utilized to accelerate the conversion from liquid LiPSes to solid Li2Se2/Li2Se, leading to suppressed shuttle effect and thus improved battery performance. Our present study provides valuable inspiration to the future exploration for the rational design of high-efficient catalysts for practical Li-Se batteries.

Performance improvement of aqueous zinc batteries by zinc oxide and Ketjen black co-modified glass fiber separators.

Rechargeable aqueous zinc-based batteries (AZBs) are intriguing candidates for next-generation energy storage batteries. However, the dendrites generated plagued their development during charging. To inhibit the dendrite generation, a novel modification method based on the separators was proposed in this study. The separators were co-modified by spraying sonicated Ketjen black (KB) and zinc oxide nanoparticles (ZnO) uniformly. The highly conductive KB homogenizes the anode interface's electric field. The deposited ions are deposited on ZnO preferentially rather than on the anode electrode, and the deposited particles can be refined. The ZnO in the uniform KB conductive network can provide sites for zinc deposition, and the by-products of the zinc anode electrode reduced. The Zn-symmetric cell with the modified separator (Zn//ZnO-KB//Zn) can cycle for 2218 h at 1 mA cm-2 stably (the unmodified Zn-symmetric cell (Zn//Zn) only can cycle for 206 h). With the modified separator, the impedance and polarization of Zn//MnO2 reduced, and the cell can charge/discharge 995 times at 0.3 A g-1. In conclusion, the electrochemical performance of AZBs can be improved effectively after separator modification by the synergistic effect of ZnO and KB.

RUL Prediction of Lithium-Ion Battery in Early-Cycle Stage Based on Similar Sample Fusion Under Lebesgue Sampling Framework

Remaining useful life (RUL) prediction of lithium-ion battery in early-cycle stage is of great significance to improve battery performance and reduce losses caused by failure. Due to complex degradation mechanism and insufficient data in early-cycle stage, current RUL prediction schemes for lithium-ion battery have trouble obtaining degradation characteristics to achieve satisfactory prediction accuracy. Aiming at this problem, this paper proposes an RUL prediction method of lithium-ion batteries in early-cycle stage based on similar sample fusion under Lebesgue sampling framework. First, a novel similarity measurement index based on fusion of Pearson correlation coefficient and Euclidean distance is proposed, and the fusion parameter is optimized by jumping spider optimization algorithm. Similar samples are selected as reference for the prediction model. Then, Lebesgue sampling theory is introduced to complete data structure transformation for similar samples, so as to ensure that the fused points of different similar samples are under the same degradation state. Finally, similar sample fusion result is transformed to Riemann sampling framework and perform a linear fitting. Fitting results are used to construct a particle filter model for capacity degradation process and RUL prediction. Experimental results and comparison studies on APR18650M1A battery dataset demonstrate the effectiveness of the proposed method.

Impact of LiBOB additive on cycle-performance degradation of lithium mono-chelated borate electrolytes: minimize the crosstalk-derived deterioration.

Novel electrolyte systems are required to further improve the performance and ensure the safety of lithium-ion batteries. Lithium-monochelated borates with trifluoromethylated ligands are used as electrolytes for lithium-ion batteries (LIBs) with a lithium bis(oxalato)borate (LiBOB) additive. The capacity decay and extremely high resistance after the cycle test at 60 °C are dramatically suppressed by the addition of LiBOB. Half-cell measurements, X-ray photoelectron spectroscopy (XPS), and electrochemical impedance spectroscopy (EIS) suggested that the reductive decomposition products of the electrolytes at the negative electrode significantly increased the resistance at the positive electrode, which originated from the crosstalk of the decomposition species formed at the negative electrode. Further analysis confirmed the importance of the LiBOB-derived solid electrolyte interphase (SEI) at the negative electrode, which suppressed the formation of crosstalk species at the negative electrode and effectively suppressed the increase in resistance of the positive electrode. This study provides a reliable and promising approach for designing high-performance electrolytes with lithium borate and emphasizes the importance of considering the reactions occurring at both electrodes to improve battery performance.

Ion correlation and negative lithium transference in polyelectrolyte solutions.

Polyelectrolyte solutions (PESs) recently have been proposed as high conductivity, high lithium transference number (t+) electrolytes where the majority of the ionic current is carried by the electrochemically active Li-ion. While PESs are intuitively appealing because anchoring the anion to a polymer backbone selectively slows down anionic motion and therefore increases t+, increasing the anion charge will act as a competing effect, decreasing t+. In this work we directly measure ion mobilities in a model non-aqueous polyelectrolyte solution using electrophoretic Nuclear Magnetic Resonance Spectroscopy (eNMR) to probe these competing effects. While previous studies that rely on ideal assumptions predict that PESs will have higher t+ than monomeric solutions, we demonstrate that below the entanglement limit, both conductivity and t+ decrease with increasing degree of polymerization. For polyanions of 10 or more repeat units, at 0.5 m Li+ we directly observe Li+ move in the "wrong direction" in an electric field, evidence of a negative transference number due to correlated motion through ion clustering. This is the first experimental observation of negative transference in a non-aqueous polyelectrolyte solution. We also demonstrate that t+ increases with increasing Li+ concentration. Using Onsager transport coefficients calculated from experimental data, and insights from previously published molecular dynamics studies we demonstrate that despite selectively slowing anion motion using polyanions, distinct anion-anion correlation through the polymer backbone and cation-anion correlation through ion aggregates reduce the t+ in non-entangled PESs. This leads us to conclude that short-chained polyelectrolyte solutions are not viable high transference number electrolytes. These results emphasize the importance of understanding the effects of ion-correlations when designing new concentrated electrolytes for improved battery performance.

Lithium-ion battery performance improvement using two-dimensional materials

Lithium-ion battery performance improvement using two-dimensional materials

Impact of the Local Environment on Li Ion Transport in Inorganic Components of Solid Electrolyte Interphases.

The spontaneously formed passivation layer, the solid electrolyte interphase (SEI) between the electrode and electrolyte, is crucial to the performance and durability of Li ion batteries. However, the Li ion transport mechanism in the major inorganic components of the SEI (Li2CO3 and LiF) is still unclear. Particularly, whether introducing an amorphous environment is beneficial for improving the Li ion diffusivity is under debate. Here, we investigate the Li ion diffusion mechanism in amorphous LiF and Li2CO3 via machine-learning-potential-assisted molecular dynamics simulations. Our results show that the Li ion diffusivity in LiF at room temperature cannot be accurately captured by the Arrhenius extrapolation from the high temperature (>600 K) diffusivities (difference of ∼2 orders of magnitude). We reveal that the spontaneous formation of Li-F regular tetrahedrons at low temperatures (<500 K) leads to an extremely low Li ion diffusivity, suggesting that designing an amorphous bulk LiF-based SEI cannot help with the Li ion transport. We further show the critical role of Li2CO3 in suppressing the Li-F regular tetrahedron formation when these two components of SEIs are mixed. Overall, our work provides atomic insights into the impact of the local environment on Li ion diffusion in the major SEI components and suggests that suppressing the formation of large-sized bulk-phase LiF might be critical to improve battery performance.

Restraining Shuttle Effect in Rechargeable Batteries by Multifunctional Zeolite Coated Separator

AbstractThe detrimental shuttle of soluble species from cathode to anode inside battery, is a critical thorn limiting stability and reversibility of rechargeable battery. Herein, an ordered pore‐window of zeolite molecular sieve is employed to effectively block shuttle of soluble matters, and prepared zeolite powder into thin zeolite layer (5 µm thick) coated on celgard separator (zeolite@celgard) with flexible and grid‐scale fabrication features. External pressure is applied to press zeolite@celgard to reduce existed interparticle gaps among zeolite particles. The separation function toward soluble species and attached H2O scavenger role of zeolite@celgard are demonstrated via 1H/19F Nuclear Magnetic Resonance spectra, Inductive Coupled Plasma Emission Spectrometer and X‐Ray Photoelectron Spectroscopy results collected from Li/LiMn2O4 battery, time‐dependent in situ Raman tests in Li/S battery, and penetration experiments of redox mediator shuttle in Li/O2 battery. Replacing typically‐used celgard/glassfiber separators, a series of side reactions (active material outflowing, low coulombic efficiency, and anode corrosion) induced via shuttle of soluble species are addressed, resulting in battery performance improvement of Li/LiMn2O4, Li/S, and Li/O2 batteries. Both scientific hypothesis of utilizing pore‐size effect of zeolite for physically block soluble species, and cost‐effective, grid‐scale, and flexible zeolite‐based separators can be extended to other rechargeable battery systems based on flowing/soluble species.

Understanding the impedance spectra of all-solid-state lithium battery cells with sulfide superionic conductors

Electrochemical impedance spectroscopy (EIS) will assist the development of all-solid-state lithium batteries by identifying their performance limiting resistances, although an elaborate distinction method has not been established to date. Herein, the distribution-of-relaxation-times method was used to support the quantification and understanding of EIS data, which were compiled over various temperatures and states of charge (SOCs) for all-solid-state cells with an In–Li anode, coated-LiCoO2 composite cathode, and separator comprising two kinds of sulfide solid electrolytes (SEs): Li10+xGe1+xP2−xS12 (LGPS) or its structural analogue in the Li–P–S–Br system (LPSBr). It was revealed that the In–Li interface and interphase resistances differ significantly depending on the separator SE, confirming an imperceptible chemical reaction between In–Li/LPSBr and the chemical instability of In–Li/LGPS. Consequently, the LGPS-based cell suffers from a large total impedance (188 Ω at 298 K and 100% SOC with 151 Ω at Li–In/LGPS), which is 250% higher than that of the LPSBr-based cell (66 Ω with 18 Ω at Li–In/LPSBr). This study provides guidance for the quantitative analysis of EIS data and in improvement of battery performance, such as developing new SEs that are as ion-conductive as LGPS and as stable as LPSBr.

Blocking Directional Lithium Diffusion in Solid-State Electrolytes at the Interface: First-Principles Insights into the Impact of the Space Charge Layer.

Understanding the degradation mechanisms in solid-state lithium-ion batteries at interfaces is fundamental for improving battery performance and for designing recycling methodologies for batteries. A key source of battery degradation is the presence of the space charge layer at the solid-state electrolyte-electrode interface and the impact that this layer has on the thermodynamics of the electrolyte structure. Currently, Li10GeP2S12 in its pristine form has one of the highest lithium conductivities and has been used as a template for designing even higher conductivity derived structures. However, being an ionic material with mostly linear diffusion, it is prone to path-blocker defects, which we show here to be especially prevalent in the space charge layer. We analyze the thermodynamic properties of a number of path-blocker defects using density functional theory and their potential crystal decomposition and find that the presence of an electrostatic potential in the space charge layer elevates the likelihood of existence of these defects, which otherwise would not be likely to form in the bulk of the electrolyte away from electrodes. We use ab initio molecular dynamics to assess the impact of these defects on the diffusivity of the crystal and find that they all reduce the lithium diffusivity. While our work focuses on Li10GeP2S12, it is relevant to any solid-state electrolyte with mainly linear diffusion.

Elucidating the charge-transfer and Li-ion-migration mechanisms in commercial lithium-ion batteries with advanced electron microscopy

Understanding the charge-transfer and Li-ion-migration mechanisms in complex electrochemical environments is critical to improving the performance of commercial lithium-ion batteries (LIBs). Advanced electron microscopy and the associated characterization techniques have significantly assisted in clarifying the structure–function relationships of commercial LIBs by providing localized nano/atomic-scale information concerning the following aspects: atomic structures of light/heavy elements, spatial distributions of structural phase transitions, Li⁺ occupation, interfacial phase structures, occupation and migration of elements, elemental distribution in the interfacial layer, Li⁺ concentration, and interfacial space charge layer. Besides, the development of various <i>in situ</i> techniques coupled with electron microscopy can enable comprehensive understanding of the structural evolution, growth of lithium dendrites at the anode, as well as the ion transport and charge accumulation at the electrode–electrolyte interface in LIBs during charging and discharging. This review summarizes the recent progress of how advanced electron microscopy contributes to elucidating key structural information and evolution in commercial LIBs. Emphasis is placed on (1) the discussions of transition metal dissolution and charge-transfer mechanisms during charging and discharging of LIB cathodes; (2) the morphologies, structures, and compositions of solid-electrolyte-interphase (SEI)/cathode– electrolyte-interface (CEI) films, along with their influence on battery performance; (3) the effects of crystal structures, internal crystal defects, and interface structure on ion transport. The lithiation and delithiation processes in LIBs are scrutinized, and strategies for optimizing ion migration are proposed. This information has been collated to enable a deeper understanding of the charge-transfer and ion-migration mechanisms in commercial LIBs, and to provide guidance for improving battery performance.

Nanostructures of silicon anodes in Li-ion batteries

As the application scenarios of lithium-ion batteries expand to many fields including electric vehicles and wearable devices, the energy density of current Li-ion batteries should be improved for satisfying the raising demand. In recent years, various methods have been gradually intensified, in which battery anode materials have received widespread attention. One of the most effective ways for improving battery performance is the use of silicon with different nanostructures, such as structures with different dimensions and different elemental doping, as the anode material, which can effectively improve the stability of solid electrolyte layers, enhance the number of reversible cycles and reversible capacity. This review summarizes the latest advances in silicon nanostructured anodes for lithium-ion batteries including nitrogen-doped carbon-caged silicon nanoparticles, silicon nanotubes made of layered CaSiO3, layered porous silicon encapsulated in carbon nanotube cages, silicon nanoparticles encapsulated in carbon-coated mesoporous silicon shells, and three-dimensional hierarchical porous structures. These nanostructures with excellent electrochemical properties can provide directions for the evolution of high-performance lithium-ion batteries.

Ultrathin ALD Aluminum Oxide Thin Films Suppress the Thermal Shrinkage of Battery Separator Membranes.

Thermal runaway is a major safety concern in the applications of Li-ion batteries, especially in the electric vehicle (EV) market. A key component to mitigate this risk is the separator membrane, a porous polymer film that prevents physical contact between the electrodes. Traditional polyolefin-based separators display significant thermal shrinkage (TS) above 100 °C, which increases the risk of battery failure; hence, suppressing the TS up to 180 °C is critical to enhancing the cell's safety. In this article, we deposited thin-film coatings (less than 10 nm) of aluminum oxide by atomic layer deposition (ALD) on three different types of separator membranes. The deposition conditions and the plasma pretreatment were optimized to decrease the number of ALD cycles necessary to suppress TS without hindering the battery performance for all of the studied separators. A dependency on the separator composition and porosity was found. After 100 ALD cycles, the thermal shrinkage of a 15 μm thick polyethylene membrane with 50% porosity was measured to be below 1% at 180 °C, with ionic conductivity >1 mS/cm. Full battery cycling with NMC532 cathodes demonstrates no hindrance to the battery's rate capability or the capacity retention rate compared to that of bare membranes during the first 100 cycles. These results display the potential of separators functionalized by ALD to enhance battery safety and improve battery performance without increasing the separator thickness and hence preserving excellent volumetric energy.

Low concentration salt triggered in-situ asymmetric gel electrolyte for Li-S battery

Lithium-sulfur (Li-S) batteries with high specific capacity are expected to play important roles in next-generation high-energy-storage systems. However, uncontrollable shuttle effect of Li polysulfide (LiPS) and safety concerns still hinder their applications. Herein, we report an in-situ formed asymmetric gel polymer electrolyte (AGPE) fabricated through a novel and low-cost strategy. In cases of modifying the separator with Lewis acid and inducing an in-situ polymerization reaction, an enclosed catholyte chamber is constructed between sulfur cathode and separator while liquid-state electrolytes still maintain in the anode side. Experimental characterizations indicate the as-prepared AGPE could effectively prevents the shuttle effect while allowing rapidly Li+ transport property. With such AGPE, the Li symmetric cells show stable cycle performance over 1400 h cycling, and Li-S batteries exhibit a high capacity of 1090 mAh g−1 with a capacity decay rate of only ∼0.2% per cycle after 200 cycles. Besides, by combining the electrochemical measurements and the evolution of sulfur species upon cycling, the origin of enhanced cycle performance is demonstrated from the perspective of reaction kinetics in this work. Our research therefore provides a novel strategy for the electrolyte configuration and reveals a promising direction for the performance improvement of Li-S batteries.

Three-in-one oxygen-deficient titanium dioxide in a pomegranate-inspired design for improved lithium storage

Defects engineering has played an ever-increasing important role in electrochemistry, especially secondary lithium batteries. TiO2 is regarded as a promising anode due to its attractive cycling stability, low volume strain and great abundance, while challenges of intrinsic poor electrical and ionic conductivity remain to be addressed. Herein, we report a three-in-one oxygen vacancy (VO)-involved pomegranate design for TiO2-x/C composite anode, which provides highly improved electrical conduction, shortened Li+ pathway and promoted Li+ redox. N-doped mesoporous carbon acts as a robust scaffold to support the whole structure, electron highway and efficient reductant to generate VO on TiO2 nanoparticles during crystallization. Theoretical calculations reveal the crucial role of surface VO on TiO2 in Li electrochemistry. Resultantly, the optimal TiO2-x/C anode achieves significantly enhanced cycling performance (203 mAh/g retained after 2000 cycles at 1 A/g). Postmortem analysis reveals the robustness of VO and reasonable structure stability upon cycles for improved battery performance.