Department of Mechanical Engineering

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https://udspace.udel.edu/handle/19716/4949

Mechanical engineering is the broadest of the engineering disciplines. Our program provides a wide range of opportunities in practice and in research, as well as non-engineering fields including business, law or medicine. Specific areas of focus in mechanical engineering at Delaware include the fields of biomechanics, clean energy and the environment, composite and advanced materials, nano-technology and nano-materials, and robotics and controls.

The undergraduate program is fully accredited and our curriculum is created to be flexible and responsive to the students' interests and needs. Our classes are taught by full-time faculty members and our undergraduates are encouraged to work directly with the faculty in their electives and in research activities including the University of Delaware Undergraduate Research Program and Senior Thesis research. Our Senior Design Capstone Class is structured as a type of practicum enabling students to solve real-world problems for local companies.

The graduate program also provides flexibility including a direct Ph.D. program without the requirements of a Master's degree and the ability to accommodate students with Mathematics and Physics majors into our graduate program. The Department's research program is recognized internationally and includes many cross-disciplinary interests; for example, the Center for Composite Materials, the Center for Biomedical Engineering Research, and the Center for Fuel Cell Research.

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Now showing 1 - 20 of 92

3D Computational Model for an Electrochemical Gas Separation and Inerting System
(Journal of The Electrochemical Society, 2022-04-25) Aryal, Utsav Raj; Aziz, Majid; Prasad, Ajay K.
Aircraft fuel tank inerting is employed to reduce the flammability of the fuel vapor in the ullage (air volume above the fuel) by restricting its oxygen concentration to a safe value—12% for commercial aircraft and 9% for military aircraft. Inerting is typically accomplished by displacing oxygen in the ullage with an inert gas like nitrogen. Electrochemical gas separation and inerting system (EGSIS) is an on-board method to generate and supply nitrogen-enriched air (NEA) to the fuel tank. EGSIS combines a polymer electrolyte membrane (PEM) electrolyzer anode which dissociates water to evolve oxygen, and a PEM fuel cell cathode which reduces oxygen from atmospheric air to produce NEA at its outlet. This paper represents the first attempt to model and simulate EGSIS using a three-dimensional, steady state, isothermal model. Various EGSIS performance indicators such as current density, reactant concentration distribution, and polarization curves are studied as a function of operating conditions and design parameters. The results from the computational model are validated against our previous experimental results for various operating conditions. The simulation results reveal the effects of temperature, reactant flowrates, and material property optimization on EGSIS performance. Different operating strategies are explored with the goal of improving system performance.
A multiscale 3D finite element analysis of fluid/solute transport in mechanically loaded bone
(Nature Publishing Group, 9/27/16) Fan,Lixia; Pei,Shaopeng; Lu,X. Lucas; Wang,Liyun; Lixia Fan, Shaopeng Pei,X Lucas Lu,Liyun Wang; Wang, Liyun
The transport of fluid, nutrients, and signaling molecules in the bone lacunar-canalicular system (LCS) is critical for osteocyte survival and function. We have applied the fluorescence recovery after photobleaching (FRAP) approach to quantify load-induced fluid and solute transport in the LCS in situ, but the measurements were limited to cortical regions 30-50 mu m underneath the periosteum due to the constrains of laser penetration. With this work, we aimed to expand our understanding of load-induced fluid and solute transport in both trabecular and cortical bone using a multiscaled image-based finite element analysis (FEA) approach. An intact murine tibia was first re-constructed from microCT images into a three-dimensional (3D) linear elastic FEA model, and the matrix deformations at various locations were calculated under axial loading. A segment of the above 3D model was then imported to the biphasic poroelasticity analysis platform (FEBio) to predict load-induced fluid pressure fields, and interstitial solute/fluid flows through LCS in both cortical and trabecular regions. Further, secondary flow effects such as the shear stress and/or drag force acting on osteocytes, the presumed mechano-sensors in bone, were derived using the previously Developmenteloped ultrastructural model of Brinkman flow in the canaliculi. The material properties assumed in the FEA models were validated against previously obtained strain and FRAP transport data measured on the cortical cortex. Our results demonstrated the feasibility of this computational approach in estimating the fluid flux in the LCS and the cellular stimulation forces (shear and drag forces) for osteocytes in any cortical and trabecular bone locations, allowing further studies of how the activation of osteocytes correlates with in vivo functional bone formation. The study provides a promising platform to reveal potential cellular mechanisms underlying the anabolic power of exercises and physical activities in treating patients with skeletal deficiencies.
A novel digital lifecycle for Material-Process-Microstructure-Performance relationships of thermoplastic olefins foams manufactured via supercritical fluid assisted foam injection molding
(Polymer Engineering and Science, 2024-03-15) Pradeep, Sai Aditya; Deshpande, Amit M.; Lavertu, Pierre‐Yves; Zheng, Ting; Yerra, Veera Aditya; Shimabukuro, Yiro; Li, Gang; Pilla, Srikanth
This research significantly enhances the applicability of thermoplastic olefins (TPOs) in the automotive industry using supercritical N2 as a physical foaming agent, effectively addressing the limitations of traditional chemical agents. It merges experimental results with simulations to establish detailed material-process-microstructure-performance (MP2) relationships, targeting 5–20% weight reductions. This innovative approach labeled digital lifecycle (DLC) helps accurately predict tensile, flexural, and impact properties based on the foam microstructure, along with experimentally demonstrating improved paintability. The study combines process simulations with finite element models to develop a comprehensive digital model for accurately predicting mechanical properties. Our findings demonstrate a strong correlation between simulated and experimental data, with about a 5% error across various weight reduction targets, marking significant improvements over existing analytical models. This research highlights the efficacy of physical foaming agents in TPO enhancement and emphasizes the importance of integrating experimental and simulation methods to capture the underlying foaming mechanism to establish material-process-microstructure-performance (MP2) relationships. Highlights - Establishes a material-process-microstructure-performance (MP2) for TPO foams - Sustainably produces TPO foams using supercritical (ScF) N2 with 20% lightweighting - Shows enhanced paintability for TPO foam improved surface aesthetics - Digital lifecycle (DLC) that predicts both foam microstructure and properties - DLC maps process effects & microstructure onto FEA mesh for precise prediction
A parallel fictitious domain method for the interface-resolved simulation of particle-laden flows and its application to the turbulent channel flow
(Hong Kong Polytechnic University, Department of Civil and Structural Engineering, 1/20/16) Yu,Zhaosheng; Lin,Zhaowu; Shao,Xueming; Wang,Lian-Ping; Zhaosheng Yu, Zhaowu Lin, Xueming Shao , Lian-Ping Wang; Wang, Lian-Ping
A parallel direct-forcing (DF) fictitious domain (FD) method for the simulation of particulate flows is reported in this paper. The parallel computing strategies for the solution of flow fields and particularly the distributed Lagrange multiplier are presented, and the high efficiency of the parallel code is demonstrated. The new code is then applied to study the effects of particle density (or particle inertia) on the turbulent channel flow. The results show that the large-scale vortices are weakened more severely, and the flow friction drag increases first and then reduces, as particle inertia is increased.
A traveler-centric mobility game: Efficiency and stability under rationality and prospect theory
(PLOS ONE, 2023-05-05) Chremos, Ioannis Vasileios; Malikopoulos, Andreas A.
In this paper, we study a routing and travel-mode choice problem for mobility systems with a multimodal transportation network as a “mobility game” with coupled action sets. We formulate an atomic routing game to focus on the travelers’ preferences and study the impact on the efficiency of the travelers’ behavioral decision-making under rationality and prospect theory. To control the innate inefficiencies, we introduce a mobility “pricing mechanism,” in which we model traffic congestion using linear cost functions while also considering the waiting times at different transport hubs. We show that the travelers’ selfish actions lead to a pure-strategy Nash equilibrium. We then perform a Price of Anarchy and Price of Stability analysis to establish that the mobility system’s inefficiencies remain relatively low and the social welfare at a NE remains close to the social optimum as the number of travelers increases. We deviate from the standard game-theoretic analysis of decision-making by extending our mobility game to capture the subjective behavior of travelers using prospect theory. Finally, we provide a detailed discussion of implementing our proposed mobility game.
Adaptive Functional Electrical Stimulation Delivers Stimulation Amplitudes Based on Real-Time Gait Biomechanics
(Journal of Medical Devices, 2024-05-21) Donlin, Margo C.; Higginson, Jill S.
Functional electrical stimulation (FES) is often used in poststroke gait rehabilitation to decrease foot drop and increase forward propulsion. However, not all stroke survivors experience clinically meaningful improvements in gait function following training with FES. The purpose of this work was to develop and validate a novel adaptive FES (AFES) system to improve dorsiflexor (DF) and plantarflexor (PF) stimulation timing and iteratively adjust the stimulation amplitude at each stride based on measured gait biomechanics. Stimulation timing was determined by a series of bilateral footswitches. Stimulation amplitude was calculated based on measured dorsiflexion angle and peak propulsive force, where increased foot drop and decreased paretic propulsion resulted in increased stimulation amplitudes. Ten individuals with chronic poststroke hemiparesis walked on an adaptive treadmill with adaptive FES for three 2-min trials. Stimulation was delivered at the correct time to the dorsiflexor muscles during 95% of strides while stimulation was delivered to the plantarflexor muscles at the correct time during 84% of strides. Stimulation amplitudes were correctly calculated and delivered for all except two strides out of nearly 3000. The adaptive FES system responds to real-time gait biomechanics as intended, and further individualization to subject-specific impairments and rehabilitation goals may lead to improved rehabilitation outcomes.
An all-copper plasmonic sandwich system obtained through directly depositing copper NPs on a CVD grown graphene/copper film and its application in SERS
(Royal Society of Chemistry, 2015-05-11) Li, Xuanhua; Ren, Xingang; Zhang, Yongxing; Choy, Wallace C. H.; Wei, Bingqing; Xuanhua Li, Xingang Ren, Yongxing Zhang, Wallace C. H. Choy and Bingqing Wei; Wei, Bingqing
A simple, low-cost, all-copper sandwich system has been obtained through directly depositing Cu nanoparticles (NPs) onto a graphene sheet, which has already been grown on a Cu foil (Cu-NGF). The new design inherits two key advantages: (1) the materials of the NGF coupling system are composed of only cheaper Cu instead of Au and Ag, (2) direct fabrication of the system without transferring graphene will greatly lower the fabrication cost. More importantly, the Cu-NFG system shows a high sensitivity in surface-enhanced Raman scattering (SERS) with the highest enhancement factor (EF, over 1.89 × 107) reported to date in Cu plasmonic systems. Experimental and theoretical results reveal that the strong EF is mainly because of the strong near-field coupling between Cu NPs and Cu films at the optimal angle of incidence, opening up a new route for Cu materials in SERS applications.
Analytical Representation and Efficient Computation of the Effective Conductivity of Two-Phase Composite Materials
(International Journal for Numerical Methods in Engineering, 2022-04-04) Roy, R. Valéry
Many engineered materials display ordered or disordered microstructures. Such materials exhibit transport properties which are unmatched by their single-phase homogeneous counterparts. These properties are obtained by the mixture of two or more phases typically characterized by a large contrast in their properties. For the development of these materials, it is critical to develop a robust computational framework in order to provide a fundamental understanding of how microstructure affects performance. This hinges on predicting their macroscopic properties, given the constitutive laws and spatial distribution of their constituents. To this end, this work presents a computational framework based on formulating periodic conduction transport problems in terms of boundary integral equations whose kernel is expressed in terms of Weierstrass zeta-function. The components of the effective conductivity tensor are then sought in the form of power series expansions of a conductivity contrast parameter. To accelerate their convergence, these expansions are transformed into Padé approximants. Presently restricted to the case of two-dimensional, two-phase microstructures, this framework is shown to yield accurate results over the entire range of the contrast parameter. Representation of the kernel as a lattice sum allows the use the fast multipole method, thereby making computations significantly more efficient.
Assembling metal-polyphenol coordination interfaces for longstanding zinc metal anodes
(EcoMat, 2022-01-11) Huyan, Yu; Wang, Jian-Gan; Tian, Shan; Ren, Lingbo; Liu, Huanyan; Wei, Bingqing
Zn metals have gained the immense attention of researchers for their wide employment as the anode of high-performance aqueous batteries. Nonetheless, the Zn anodes suffer from uncontrollable dendrite growth and parasitic side reactions, which substantially shorten the battery lifespan. This study proposes an interfacial assembly of a metal-polyphenol coordination coating on Zn anodes to regulate Zn2+ deposition behavior. Bismush-coordinated polyphenolic ligands (i.e., tannic acid, TA) create a functional interface that could promote Zn's uniform nucleation and plating/striping kinetics. Moreover, the artificial coating acts as a physical barrier to inhibit surface corrosion. As a consequence, the TA-Bi-modified Zn anodes display a small voltage hysteresis of ~38 mV at 1 mA cm−2 over 2600 h and an ultra-long lifespan for 3100 h (~4.3 months) even at a high-current density of 10 mA cm−2. When assembled with a vanadium-based cathode, the full Zn-ion batteries achieve improved electrochemical performance.
Behavior modeling for hybrid robotic vehicles
(Department of Mechanical Engineering, University of Delaware, 2011-10) Rawal, Chetan
The behavior of a certain class of hybrid robotic systems can be expressed using formal languages. In this work, we show how languages can be generated from discrete abstractions of such hybrid systems; that these languages are regular; and they belong to the star free (SF) class of the Sub-regular hierarchy. Planning and control of hybrid systems is typically difficult due to the computational cost involved in predicting the system’s future states, since the states can take infinite values while evolving along the trajectories of continuous dynamics. A discrete abstraction of the hybrid system can reduce these values to a finite number, thereby fascilitating the solution to the reachability problem. Abstraction enables us to focus on planning the system’s overall behavior through controller sequences observed in the abstract system, instead of dealing with the dynamics associated with each controller.
Bioderived silicon nano-quills: synthesis, structure and performance in lithium-ion battery anodes
(Green Chemistry, 2024-03-12) Chen, Nancy; Sabet, Morteza; Sapkota, Nawraj; Parekh, Mihir; Chiluwal, Shailendra; Koehler, Kelliann; Clemons, Craig M.; Ding, Yi; Rao, Apparao M.; Pilla, Srikanth
Cellulose nanocrystals (CNCs) are bioderived one-dimensional species with versatile surface chemistry and unique self-assembling behavior in aqueous solutions. This work presents a scientific approach to leverage these characteristics for creating CNC network templates and processing them to engineer a novel silicon (Si)-based material called silicon nano-quill (SiNQ) for energy storage applications. The SiNQ structure possesses a porous, tubular morphology with a substantial ability to store lithium ions while maintaining its structural integrity. The presence of Si suboxides in the SiNQ structure is demonstrated to be crucial for realizing a stable cycling performance. One of the defining attributes of SiNQ is its water dispersibility due to Si–H surface bonds, promoting water-based Si-graphite electrode manufacturing with environmental and economic benefits. The incorporation of only 17 wt% SiNQ enhances the capacity of graphitic anodes by ∼2.5 times. An initial coulombic efficiency of 97.5% is achieved by employing a versatile pre-lithiation. The SiNQ-graphite anodes with high active loading, when subjected to accelerated charging/discharging conditions at 5.4 mA cm−2, exhibit stable cycling stability up to 500 cycles and average coulombic efficiency of >99%. A generalized physics-based cyclic voltammetry model is presented to explain the remarkable behavior of SiNQs under fast-charging conditions.
Biomechanical Analysis of Gait Termination in 11-17 Year Old Youth at Preferred and Fast Walking Speeds
(Elsevier, 2016-07-15) Ridge, Sarah Trager; Henley, John; Manal, Kurt; Miller, Freeman; Richards, James G.; Sarah Trager Ridge, John Henley, Kurt Manal, Freeman Miller, and James G. Richards; Ridge, Sarah Trager; Manal, Kurt; Richards, James G.
In populations where walking and/or stopping can be difficult, such as in children with cerebral palsy, the ability to quickly stop walking may be beyond the child’s capabilities. Gait termination may be improved with physical therapy. However, without a greater understanding of the mechanical requirements of this skill, treatment planning is difficult. The purpose of this study was to understand how healthy children successfully terminate gait in one step when walking quickly, which can be challenging even for healthy children. Lower extremity kinematic and kinetic data were collected from 15 youth as they performed walking, planned, and unplanned stopping tasks. Each stopping task was performed as the subject walked at his/her preferred speed and a fast speed. The most significant changes in mechanics between speed conditions (preferred and fast) of the same stopping task were greater knee flexion angles (unplanned: +16.49±.54°, p=.00; planned: +15.75±1.1°, p=.00) and knee extension moments (unplanned: +.67±.02 N/kgm, p=.00; planned: +.57±.23 N/kgm, p=.00) at faster speeds. The extra range of motion in the joints and extra muscle strength required to maintain the stopping position suggests that stretching and strengthening the muscles surrounding the joints of the lower extremity, particularly the knee, may be a useful intervention.
Biomimetic Proteoglycans Strengthen the Pericellular Matrix of Normal and Osteoarthritic Human Cartilage
(ACS Biomaterials Science & Engineering, 2024-08-12) Kahle, Elizabeth R.; Fallahi, Hooman; Bergstrom, Annika R.; Li, Anita; Trouillot, Colette E.; Mulcahey, Mary K.; Lu, X. Lucas; Han, Lin; Marcolongo, Michele S.
In osteoarthritis (OA), degradation of cartilage pericellular matrix (PCM), the proteoglycan-rich immediate cell microniche, is a leading event of disease initiation. This study demonstrated that biomimetic proteoglycans (BPGs) can diffuse into human cartilage from both normal and osteoarthritic donors and are preferentially localized within the PCM. Applying immunofluorescence (IF)-guided AFM nanomechanical mapping, we show that this localization of BPGs increases the PCM micromodulus of both normal and OA specimens. These results illustrate the capability of BPGs to integrate with degenerative tissues and support the translational potential of BPGs for treating human OA and other diseases associated with proteoglycan degradation.
Biosourced Antioxidants for Chemical Durability Enhancement of Perfluorosulfonic Acid Membrane
(Advanced Functional Materials, 2024-01-02) Agarwal, Tanya; Adhikari, Santosh; Babu, Siddharth Komini; Prasad, Ajay K.; Advani, Suresh G.; Borup, Rodney L.
The chemical durability of perfluorosulfonic acid (PFSA) membranes is a topic of growing interest to meet Department of Energy (DOE) durability targets for heavy-duty vehicle (HDV) applications. State-of-the-art membranes like Nafion, rely on the use of cerium, heteropolyacids, and other inorganic additives to increase PFSA chemical durability. A less explored avenue for the oxidative stabilization of PFSA and hydrocarbon membranes is the use of organic antioxidants. No reversible organic antioxidant has been demonstrated to date which can enhance membrane lifetime by factors comparable to cerium. Here, ellagic acid (EA) is demonstrated as a promising radical scavenger for PFSA's. It is found that the incorporation of EA enhances the chemical durability of Nafion by 160%. EA, when incorporated with cerium as an electron donorenhances Nafion durability by at least 80% compared to a membrane incorporated with just cerium in DOE-defined durability tests. EA is found to be reversible in acidic conditions like those of fuel cells and its reversibility could be further enhanced by the use of suitable co-antioxidants.
Bladder expandable robotic system and UV materials for rapid internal pipeline repair
(SAMPE Conference Proceedings 2023, 2023-04-18) Tierney, John J.; Vanarelli, Alex; Fuessel, Lukas; Abu-Obaid, Ahmad; Sauerbrunn, Steve; Das, Shagata; Deitzel, Joseph; Tatar, Jovan; Heider, Dirk; Shenton, Harry W. III; Kloxin, Christopher J.; Sung, Dae Han; Thostenson, Erik; Gillespie, John W. Jr.
This paper describes a novel composite placement process to fabricate stand-alone structural pipe within existing legacy pipelines—with no disruption in gas service. The process utilizes low-cost, UV-curable, glass fiber reinforced plastics (GFRP) for discrete preforms made from continuous fiber fabrics. These sections are designed to meet 50-year service life by addressing the unique loading conditions of the pipe repair allowing for the design customization of the preforms to accommodate the state of pipe corrosion, access points or other local features that may vary along the length of the pipe. The approach offers maximum design flexibility and customization while minimizing installation time and cost. The preforms are fabricated above ground using rapid automated manufacturing methods for quality control. The preforms are transported by a tethering system to the robot. The robot is comprised of a self-propelled dual inflation expandable bladder system that places, consolidates, and cures standard or custom composite sections along the entire pipe length in a continuous co-cure process. This system is designed to adapt to pipe features that include lateral tees, service connections, joints, gaps, and irregular cross sections. In addition, variable thickness composite sections can be placed along the pipe where exposed to high external loads under railroads, highways, airports or where soil erosion and movement occurs. This paper presents the robot design, assessment of UV curable resins, embedded sensing methods, and fabrication of pipe sections with this system.
Blending poly(2-ethyl-2-oxazoline) with hydrophobic polymers as a hybrid adhesive with enhanced water-resistant properties
(Journal of Applied Polymer Science, 2021-07-16) Zhang, Yuanyuan; Li, Xuanhua; Guo, Shaohui; Wei, Bingqing
The use of poly(2-ethyl-2-oxazoline) (PEOX) in a wet environment is limited because of its high hydrophilicity. In this study, PEOX based blends were prepared via blending PEOX with hydrophobic polymers, such as poly(styrene-co-acrylonitrile) (SAN), poly(4-vinylphenol) (PVPh), and poly(vinylidene fluoride) (PVDF), in order to improve the water-resistance of PEOX. The blends' water resistance properties are evaluated by the contact angle, solubility, moisture absorption, and mechanical strength in a wet environment. The results show that the water resistance and the adhesion strength of PEOX in a wet environment are dramatically enhanced by polymer blending. The blend with 30 wt% PVPh demonstrates excellent performances in transparency and water-resistant abilities. It is found that the stable hydrogen bonding within the blend plays an important role in hydrophobic modification. The PVPh/PEOX blend can be applied as a new type of transparent coating or adhesive with enhanced water-resistant properties in a wet environment.
Boosting photocatalytic hydrogen production from water by photothermally induced biphase systems
(Nature Communications, 2021-02-26) Guo, Shaohui; Li, Xuanhua; Li, Ju; Wei, Bingqing
Solar-driven hydrogen production from water using particulate photocatalysts is considered the most economical and effective approach to produce hydrogen fuel with little environmental concern. However, the efficiency of hydrogen production from water in particulate photocatalysis systems is still low. Here, we propose an efficient biphase photocatalytic system composed of integrated photothermal–photocatalytic materials that use charred wood substrates to convert liquid water to water steam, simultaneously splitting hydrogen under light illumination without additional energy. The photothermal–photocatalytic system exhibits biphase interfaces of photothermally-generated steam/photocatalyst/hydrogen, which significantly reduce the interface barrier and drastically lower the transport resistance of the hydrogen gas by nearly two orders of magnitude. In this work, an impressive hydrogen production rate up to 220.74 μmol h−1 cm−2 in the particulate photocatalytic systems has been achieved based on the wood/CoO system, demonstrating that the photothermal–photocatalytic biphase system is cost-effective and greatly advantageous for practical applications.
Carbon Additive Manufacturing with a Near-Replica “Green-to-Brown” Transformation
(Advanced Materials, 2023-05-30) Zhang, Chunyan; Shi, Baohui; He, Jinlong; Zhou, Lyu; Park, Soyeon; Doshi, Sagar; Shang, Yuanyuan; Deng, Kaiyue; Giordano, Marc; Qi, Xiangjun; Cui, Shuang; Liu, Ling; Ni, Chaoying; Fu, Kun Kelvin
Nanocomposites containing nanoscale materials offer exciting opportunities to encode nanoscale features into macroscale dimensions, which produces unprecedented impact in material design and application. However, conventional methods cannot process nanocomposites with a high particle loading, as well as nanocomposites with the ability to be tailored at multiple scales. A composite architected mesoscale process strategy that brings particle loading nanoscale materials combined with multiscale features including nanoscale manipulation, mesoscale architecture, and macroscale formation to create spatially programmed nanocomposites with high particle loading and multiscale tailorability is reported. The process features a low-shrinking (<10%) “green-to-brown” transformation, making a near-geometric replica of the 3D design to produce a “brown” part with full nanomaterials to allow further matrix infill. This demonstration includes additively manufactured carbon nanocomposites containing carbon nanotubes (CNTs) and thermoset epoxy, leading to multiscale CNTs tailorability, performance improvement, and 3D complex geometry feasibility. The process can produce nanomaterial-assembled architectures with 3D geometry and multiscale features and can incorporate a wide range of matrix materials, such as polymers, metals, and ceramics, to fabricate nanocomposites for new device structures and applications.
Carbon Binder Domain Inhomogeneity in Silicon-Monoxide/Graphite Composite Anode by 2D Multiphysics Modeling
(Advanced Science, 2024-05-22) Gao, Xiang; Xu, Jun
The Carbon-binder domain (CBD) plays a pivotal role in the performance of lithium-ion battery electrodes. The heterogeneous distribution of CBD across the electrode has garnered significant attention. However, a thorough understanding of how this CBD inhomogeneity affects anode performance remains a crucial pursuit, especially when considering the inherent material variations present in the SiO/Graphite (SiO/Gr) composite anode. In this study, an electro-chemo-mechanical model is established that provides a detailed geometric description of the particles. This model allows to quantitatively uncover the effects of CBD inhomogeneity on the fundamental behaviors of the SiO/Gr composite anode. The findings indicate that reducing the proportion of CBD in the upper domain (near the anode surface) compared to the lower domain (near the current collector) positively influences electrochemical performance, particularly in terms of capacity and Li plating. However, such an arrangement introduces potential risks of mechanical failures, and it is recommended to incorporate a higher proportion of CBD alongside the SiO particles. Finally, an anode design with a lower CBD proportion in the upper domain exhibits superior rate performance. This study represents a pioneering modeling exploration of CBD inhomogeneity, offering a promising multiphysics model with significant potential for informing advanced battery design considerations.
Catalytic Boosting Bidirectional Polysulfide Redox using Co0.85Se/C Hollow Structure for High-Performance Lithium-Sulfur Batteries
(ChemElectroChem, 2022-02-17) Zhang, Xingyuan; Gu, Honghui; Shen, Chao; Wei, Bingqing; Wang, Jian-Gan
Achieving effective adsorption and fast conversion of soluble polysulfides confined in the sulfur cathode is critical yet challenging for building high-performance lithium-sulfur batteries. Herein, we construct a unique hollow-structured Co0.85Se/C as a separator modifier (CSPP) to effectively suppress the polysulfide shuttle effect. The Co0.85Se/C demonstrates strong anchoring with polysulfide species and smooth bidirectional electrocatalysis. The unique mesoporous hollow architecture affords sufficient catalytic sites and Li+ diffusion channels for promoting the reaction kinetics. Benefiting from the merits, the CSPP-cell could yield a superior electrochemical utilization of active sulfur, excellent rate capability (679 mAh g−1 at 5 C), and stable cycling performance with an ultralow fading rate of 0.056 % per cycle over 500 cycles. The work highlights great promise of developing cobalt-based materials as kinetic regulators for highly stable lithium-sulfur batteries.

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