Secondary Storage Systems Research Articles

Development of Bromine Adsorbing Carbon Felt Electrode by Coating of Nitrogen-Doped Mesoporous Carbon Layer for Highly Stable Flowless Zinc-Bromine Battery

Renewable energy is well known for the extreme volatility of power production, and secondary battery-based energy storage systems (BESS) are the key to the novel and safe energy industry to expand the supply of renewable energy. Currently, lithium-ion battery-based ESS is commonly used, but the frequent ignition accidents from these ESSs rather become an obstacle to the growth of the renewable energy field. Among the redox batteries, the flowless zinc-bromine battery (FLZBB) is studied as the alternative since it uses a non-flammable and cost-effective aqueous Zn- Br2 electrolyte. However, its main challenges are that bromine (Br2) and polybromide anions (), formed at the positive electrode during the charging process, cross over to the negative electrode due to the difference in chemical potential between the electrodes. The diffused Br2 oxidizes the zinc metal, electrodeposited on the negative electrode, and causes a self-discharge reaction that consumes the charging active material and Br2 the battery performance and life. Herein, we present a nitrogen-doped mesoporous carbon coated on the pristine graphite felt fibers (NMC/GF). By uniformly forming a nitrogen-doped porous carbon material on the GF fibers through the evaporation-induced self-assembly (EISA) method, it is a simple and cost-effective method to develop the structural and properties of the GF positive electrode to increase the ability of adsorption and storing the active materials, Br2 and polybromide anions (,, and ) generated during the charging process. In addition, it also improved the bromine redox reaction kinetics by having a strong affinity with the aqueous Zn-Br2 electrolyte. This facilitates long-term charge/discharge cycles, enabling high performance and improved durability for Coulombic efficiency over 95% for 5000 cycles in the FLZBB single-cell platform at a current density of 20 mA cm-2 and a high-rate areal capacity of 2 mAh cm-2.

Regulating the P-band center of SnS2-SnO2 heterostructure to boost the redox kinetics for high-performance lithium-sulfur battery

Lithium-sulfur batteries (LSBs) are considered a strong contender for the new-generation secondary energy storage system due to their high capacity and energy density. However, the sluggish reaction kinetics and the shuttle effect of lithium polysulfides (LPSs) severely hinder the cycle stability. The robust design of both the separator and cathode exhibit an effective role in restricting the shuttle effect and accelerating redox kinetics through the LPSs trapping and catalyzing effect. In this paper, a CNT-modified tin sulfide and tin oxide (SnS2-SnO2-CNTs) heterostructure was constructed as a multifunctional catalyst to modify both the separator and cathode to achieve high-performance LSBs. The formation of SnS2-SnO2 heterostructure promotes the movement of the P band center of the tin atom to the Fermi level, which realizes the association process of adsorption, capture, and conversion of LPSs, thus effectively suppressing the shuttle effect. The SnS2-SnO2 heterogeneous interface can also reduce the deposition barrier of Li2S, thus greatly promoting the redox kinetics. Together with the improved electron transfer, the resulting LSBs with the robust electrode and separator exhibit superior electrochemical performance with a high initial capacity of 930.2 mAh g−1 at 1 C with a high sulfur loading of 4.3 mg cm−2 and a remarkable capacity of up to 580.3 mAh g−1 at an ultrahigh rate of 7.4 C.

Review of Transition Metal Chalcogenides and Halides as Electrode Materials for Thermal Batteries and Secondary Energy Storage Systems.

Transition metal chalcogenides and halides (TMCs and TMHs) have been extensively used and reported as electrode materials in diverse primary and secondary batteries. This review summarizes the suitability of TMCs and TMHs as electrode materials focusing on thermal batteries (utilized for defense applications) and energy storage systems like mono- and multivalent rechargeable batteries. The report also identifies the specific physicochemical properties that need to be achieved for the same materials to be employed as cathode materials in thermal batteries and anode materials in monovalent rechargeable systems. For example, thermal stability of the materials plays a crucial role in delivering the performance of the thermal battery system, whereas the electrical conductivity and layered structure of similar materials play a vital role in enhancing the electrochemical performance of the mono- and multivalent rechargeable batteries. It can be summarized that nonlayered CoS2, FeS2, NiS2, and WS2 were found to be ideal as cathode materials for thermal batteries primarily due to their better thermal stability, whereas the layered structures of these materials with a coating of carbon allotrope (CNT, graphene, rGO) were found to be suitable as anode materials for monovalent alkali metal ion rechargeable batteries. On the other hand, vanadium, titanium, molybdenum, tin, and antimony based chalcogenides were found to be suitable as cathode materials for multivalent rechargeable batteries due to the high oxidation state of cathode materials which resists the stronger field produced during the interaction of di- and trivalent ions with the cathode material facilitating higher energy density with minimal structural and volume changes at a high rate of discharge.

Analysis of Battery Testing Protocols in the Transition from the Lab to the Field: A Test Case Using Advanced Zn-MnO2 Batteries in Off-Grid Solar Microgrids

Understanding cycling performance of batteries under varying conditions is crucial for continued development of emerging chemistries. Currently much of this work is focused on cycling single cells in well-controlled lab experiments. There are few module cycling studies in the open literature. Studies of full-sized fielded systems are even rarer. As a result of this data gap, there is limited understanding of how single cell cycling can be used to predict performance of fielded systems prior to their deployment.Sandia National Laboratories (SNL) recently deployed an advanced Zn-MnO2 secondary battery energy storage system in an off-grid solar plus storage system. Using this deployment as a test case, we will detail how performance and degradation for batteries can vary between the lab and the field. We will also discuss ways that single cell and module lab cycling can be improved to better predict operation in fielded systems.In preparation for this deployment, SNL conducted single cell cycling experiments in the lab to simulate operation in the field and determine the expected life of the systems. The first test program utilized elements of the IEC 61427-1 standard for photovoltaic off-grid application to simulate the temperature and predicted state of charge (SOC) range the cells will be cycled during field operation. The simulated field cycling targeted SOC ranges of 10 to 40% and 80-100% over 150 cycles with temperature varied between -4 and 35oC to match the ambient conditions in the field during each season. The second type of cycling test was a temperature dependence study to determine how temperature impacted cell degradation. Cells were cycled at C/10 at their full SOC range and at a single temperature until they reached 40% capacity retention. Both cycling studies predicted that low temperature operation would increase the rate of degradation.The system was deployed in May of 2022, and since that time the SNL team has collected a significant amount of performance data to help analyze system level behaviors as compared to observations from cell level testing. These include battery interactions with the solar charge controller, limitations on power inverter settings, and variance between the average system level state of charge and the test protocol. Additionally, the team is analyzing conditions found in the field, with regards to ambient temperature, solar insolation and battery charging rates, and customer usage patterns for comparison with cell-level testing protocol.Observations of the deployed system’s performance indicate there is a need for more nuanced testing protocols for lab testing that can better approximate field conditions. These may include dynamic temperature ranges that vary throughout a charge/discharge cycle, and solar charging assumptions that account for reduced insolation due to cloud cover. This can help further inform the development of charge control algorithms, system hardware and software that can help improve the overall performance of solar microgrid energy storage systems.Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. SAND2023-02502A

Self-assembled BNNSs/rGO heterostructure as a synergistic adsorption and catalysis mediator boosts the electrochemical kinetics of lithium-sulfur batteries

Lithium-sulfur (Li-S) battery with high theoretical specific capacity (1675 mAh/g), has been deemed as one of the most potential candidates of secondary energy storage system. However, the large-scale applications of Li-S batteries have been obstructed by internally sluggish multi-step redox reaction and terrible shuttle effect of lithium polysulfides (LiPSs). Herein, boron nitride nanosheets/reduced graphene oxide (BNNSs/rGO) heterostructure prepared by self-assembly crosslinking method has been designed to modify commercial separator for Li-S batteries. The hierarchical pores, physical and chemical cross-links within heterostructure can significantly enhance the adsorption capacity for LiPSs, uniquely physical and electronic interaction between BNNSs and rGO can effectively catalyze the conversion of sulfurated species. Benefiting from the synergistic adsorption-catalysis effect, BNNSs/rGO not only greatly inhibits the shuttle behaviors, but also considerably accelerates the electrochemical reaction kinetics for LiPSs and Li2S. Attributed to these merits, Li-S battery with BNNSs/rGO heterostructure mediator delivers superiorly reversible capacity as high as 915.0 mAh/g at 1 C. Even at high sulfur loading of 3.9 mg cm−2, the cell delivers ultra-stable specific capacity of 629.1 mAh/g at 1 C, and still maintains 605.5 mAh/g over 500 cycles corresponding to a capacity fade of merely 0.0075% per cycle.

Simulation Guided Coaxial Electrospinning of Polyvinylidene Fluoride Hollow Fibers with Tailored Piezoelectric Performance.

Electrospun polyvinylidene fluoride (PVDF) piezoelectric fibers have high potential applicability in mechanical energy harvesting and self-powered sensing owing to their high electromechanical coupling capabilities. Strategies for tailoring fiber morphology have been the primary focus for realizing enhanced piezoelectric output. However, the relationship between piezoelectric performance and fiber structure remains unclear. This study fabricates PVDF hollow fibers through coaxial electrospinning, whose wall thickness can be tuned by changing the internal solution concentration. Simulation analysis demonstrates an increased effective deformation of the hollow fiber as enlarging inner diameter, resulting in enhanced piezoelectric output, which is in excellent agreement with the experimental results. This study is the first to unravel the influence mechanism of morphology regulation of a PVDF hollow fiber on its piezoelectric performance from both simulation and experimental aspects. The optimal PVDF hollow fiber piezoelectric energy harvester (PEH) delivers a piezoelectric output voltage of 32.6V, ≈3 times that of the solid PVDF fiber PEH. Furthermore, the electrical output of hollow fiber PEH can be stably stored in secondary energy storage systems to power microelectronics. This study highlights an efficient approach for reconciling the simulation and tailoring the fiber PEH morphology for enhanced performances for future self-powered systems.

Sulfur polymerization strategy based on the intrinsic properties of polymers for advanced binder‐free and high‐sulfur‐content Li–S batteries

AbstractLithium–sulfur (Li–S) batteries are the promising next‐generation secondary energy storage systems, because of their advantages of high energy density and environmental friendliness. Among numerous cathode materials, organosulfur polymer materials have received extensive attentions because of their controllable structure and uniform sulfur distribution. However, the sulfur content of most organosulfur polymer cathodes is limited (S content <60%) due to the addition of large amounts of conductive agents and binders, which adversely affects the energy density of Li–S batteries. Herein, a hyperbranched sulfur‐rich polymer based on modified polyethyleneimine (Ath‐PEI) named carbon nanotube‐entangled poly (allyl‐terminated hyperbranched ethyleneimine‐random‐sulfur) (CNT/Ath‐PEI@S) was prepared by sulfur polymerization and used as a Li–S battery cathode. The high intrinsic viscosity of Ath‐PEI provided considerable adhesion and avoided the addition of PVDF binder, thereby increasing the sulfur content of cathodes to 75%. Moreover, considering the uniform distribution of elemental sulfur by the polymer, the utilization of sulfur was successfully improved, thus improving the rate capability and discharge capacity of the battery. The binder‐free, sulfur‐rich polymer cathode exhibited ultra‐high initial discharge capacity (1520.7 mAh g−1 at 0.1 C), and high rate capability (804 mAh g−1 at 2.0 C). And cell‐level calculations show that the electrode exhibits an initial capacity of 942.3 mAh g−1electrode, which is much higher than those of conventional sulfur‐polymer electrodes reported in the literature.

High-capacity semi-organic polymer batteries: From monomer to battery in an all-aqueous process

Aqueous Zinc-batteries comprising organic cathode materials represent interesting candidates for sustainable, safe, environmentally friendly, and highly flexible secondary energy storage system. Here, we demonstrate that such an oxygen-tolerant, semi-organic setup can conveniently be prepared in an all-aqueous process, including all steps from the initial polymerization to the coin cell assembly without the need of any intermediate purification steps, and still reach high energy densities of 2.55 mAh cm−2. The TEMPO-modified and crosslinked poly(methacrylamide) cathode facilitates an excellent compatibility to the aqueous electrolyte and an efficient accessibility of the redox-active species due to the increased polarity of the material compared to the common poly(TEMPO-methacrylate) (PTMA). The material exhibits excellent stability (capacity retention of >99% after 1000 cycles at 5C) with low self-discharge and features high rate capabilities. The casting process from the aqueous slurry further appeared to be suitable for the preparation of ultra-thick but still homogeneous binder-free electrodes and exhibit total device capacities of approximately 4.5 mAh in a 2032-type coin cell. Since the overall process avoids harsh conditions or harmful solvents, is scalable, and relies on straightforward processing steps, it represents a promising step towards cost-effective and efficient rechargeable Zinc-based semi-organic batteries with competing capacities if further optimized.

How to increase the potential of aqueous Zn-MnO2 batteries: The effect of pH gradient electrolyte

Non-rechargeable alkaline Zn-MnO2 batteries are dominating the primary battery market and are a promising candidate for secondary battery storage systems as well. However, these batteries suffer from low potential and poor rechargeability. Here, we report a rechargeable membrane-less amphoteric aqueous Zn-MnO2 battery with a 2.4 V open circuit potential. We have employed alkaline (KOH), acidic (H2SO4) and neutral (K2SO4) Pluronic F-127 hydrogels as electrolytes. By placing the anode in an alkaline environment but the cathode in an acidic environment, we have successfully widened the potential window in an aqueous medium avoiding hydrogen and oxygen evolution reactions. The obtained open circuit potential of as prepared amphoteric battery is stable for more than 25 h and 200 charge-discharge cycles.

Prototype production and comparative analysis of high-speed flywheel energy storage systems during regenerative braking in hybrid and electric vehicles

In conventional EVs and HEVs, only a small part of the vehicle's kinetic energy can be usefully stored during deceleration. Generally, this storage process can be done by providing energy flow to the main battery of the vehicle. Since batteries work with a chemical reaction, they are not suitable for fast charging and discharging required for regenerative braking. In this case, a fast storage system is needed to store the regenerative braking energy in a short time. As a solution, the flywheel energy storage system (FESS) can be offered.In the literature, power transmission of vehicles with integrated FESS is provided by mechanical systems (CVT FESS). These systems are heavy, high cost, large volume, and occupy the rear axle of the vehicle.In the proposed system, a purely electrical power transmission is proposed to store the kinetic energy of the vehicle in FESS. In developed topology, the traction machine of the vehicle is also used as a generator, and the recuperation energy is stored in the electrically driven (M/G) FESS.As a result of the experimental studies, a minimum of 56% energy recovery efficiency was obtained. In addition, it has been shown that the developed system is 30% lighter, occupies 60% less space in volume, is at least 50% more cost-effective, maintenance-free, and has fewer moving parts compared to the CVT FESS.As a result, the addition of a fast-response secondary energy storage system to the electric vehicle battery contributes to the increase in efficiency.

A biogas-solar based hybrid off-grid power plant with multiple storages for United States commercial buildings

In this paper, a hybrid renewable power plant with a storage system is designed. The benefits of sizing and energy management are assessed for a commercial building under eight different climatic conditions in the United States. In the considered system, photovoltaic panels are coupled to a unitized regenerative solid oxide fuel cell. The use of biogas to feed unitized regenerative solid oxide fuel cell is investigated, employing a detailed electrochemical model of electrolyzer and fuel cell modes. A battery pack is included in the plant as a secondary storage system, together with a diesel engine operating in backup mode.Four scenarios where biogas amount is varied together with the initial state of charge of the battery were evaluated. Results demonstrate that the power plant can operate with 100 % renewable procurement if the digester produces from 6000 to 9500 stdm3/y and the battery is completely charged at the beginning of the year. By reducing the biogas availability or starting with a low state of charge, the use of the diesel generator is inevitable.The study confirms that the proposed hybrid renewable power plant is technically feasible and can be considered a reliable and clean energy source in other areas and buildings.

Corrosion in Molten Salts for Solar Thermal Power

Global energy needs continue to grow steadily with increasing population and standard of living. While fossil fuels have been a major source of our energy, they are no longer favorable due to their greenhouse gas emissions and atmospheric pollution; the development of carbon-free sources of energy is crucial. Solar energy promises unlimited amounts of emissions-free energy but suffers from intermittency issues that require expensive secondary energy storage systems to act as baseload power. A thermal energy storage (TES) system can store heat and provide a continuous source of power. Concentrated solar power (CSP) is carbon-free and can ideally be combined with a TES system to provide continuous power. These combined systems operate by focusing a large area of sunlight onto a receiver that contains a TES material to convert the sunlight into thermal energy.

Fuzzy Logic-Based Duty Cycle Controller for the Energy Management System of Hybrid Electric Vehicles with Hybrid Energy Storage System

Due to increasing fuel prices, the world is moving towards the use of hybrid electric vehicles (HEVs) because they are environmentally friendly, require less maintenance, and are a green technology. The energy management system (EMS) plays an important role in HEVs for the efficient storage of energy and control of the power flow mechanism. This paper deals with the design, modeling, and result-oriented approach for the development of EMS for HEVs using a fuzzy logic controller (FLC). Batteries and supercapacitors (SCs) are used as primary and secondary energy storage systems (ESSs), respectively. EMS consists of the ultra-power transfer algorithm (UPTA) and FLC techniques, which are used to control the power flow. The UPTA technique is used to charge the battery with the help of a single-ended primary inductor converter (SEPIC) during regenerative braking mode. The proposed research examines and compares the performance of FLC with a proportional integral (PI) controller by using MATLAB (Simulink) software. Three scenarios are built to confirm the efficiency of the proposed design. The simulation results show that the proposed design with FLC has a better response as its rise time (2.6 m) and settling time (1.47 µs) are superior to the PI controller.

Joint optimisation of sizing and fuzzy logic power management of a hybrid storage system considering economic reliability indices

This study is interested in optimisation of both sizing and energy management system of a hybrid storage system (HSS) associated with photovoltaic panels. The battery (BT) considered as the principal storage organ and a super-capacitor used as the secondary storage system to improve the BT life span makes up the HSS. The main purpose of this study is to explore a novel optimisation approach to jointly optimise the sizing and the fuzzy logic energy management system (FLEMS). In fact, an optimisation function based on sequential quadratic programming algorithm is proposed. The optimisation methodology has been performed jointly and successfully for the sizing of the BT storage system and the membership functions parameters of the FLEMS in order to decrease the levelised cost of energy with a violation time by 5% of mean absolute percentage error score <1.5% throughout the year. According to the simulations results, a benefit analysis has been done to assess the associated financial impact.

Modifications of Separators for Li–S Batteries with Improved Electrochemical Performance

Lithium–sulfur (Li–S) batteries are widely regarded as one of the promising next-generation secondary energy storage systems. However, some tricky challenges, such as electrically insulating elemental sulfur, shuttle effect and lithium dendrites, have been limiting its practical application. Modification of separators, which is found as a facile and low-cost settlement, has shown great advantages in solving the above three crucial problems, leading to greatly improved performance of Li–S batteries. In this paper, we summarize recent progresses on separators for Li–S batteries including coatings such as carbon materials, polymers, and inorganic materials, and tailoring multi-functional gel separators to achieve Li–S batteries with high performance. The importance and development directions of functional separators in the further commercialization of Li–S batteries are also discussed.

Laminar MXene-Nafion-modified separator with highly inhibited shuttle effect for long-life lithium–sulfur batteries

Lithium–sulfur (Li–S) batteries have been considered as a prospective candidate of secondary high-energy storage systems, but the shuttle effect of polysulfides through separator is a vital challenge for battery development. Herein, we report a facile strategy to modify commercial polypropylene (PP) separator by depositing a laminar MXene-Nafion composite. Nafion, as a surfactant, results in an ordered layer-by-layer deposition of MXene sheets by filtration. By comparing this modification layer to references composed of Nafion and MXene, we demonstrate that the physical resistance of MXene and electrostatic repulsion of Nafion can synergistically inhibit the shuttle effect. And the resultant Li–S cell shows exceptional cycling stability: ultralow capacity decay of 0.03% per cycle over 1000 cycles at 1C. Furthermore, MXene promotes the re-utilization of polysulfides due to its electrical conduction, while Nafion in interlayer effectively transports Li+. Thus, the cell achieves highly enhanced initial capacity (1234 vs. 834 mAh g−1 for PP cell). Besides, these results are also much higher than that of a dual-layer modification layer (MXene@Nafion), highlighting the full synergism of organic and inorganic components in this laminar nanostructure. Moreover, the laminar GO-Nafion as an example verifies the universality of this design strategy.

A flexible aqueous Al ion rechargeable full battery

With the fast development of flexible and wearable electronics, the design of secondary energy storage system based on aqueous metal ion battery with outstanding flexibility, safety and low cost is critical for their practical application. As low-cost alternatives to lithium ion battery, multivalent metal ion technologies including Mg2+, Zn2+, Ca2+, and Al3+ are investigated increasingly in the past few years. The investigation based on Al-ion chemistry is also underway considering the aluminum’s advantages of natural abundance, small ion size together with three-electron-redox properties. Herein, a flexible aqueous Al-ion battery is successfully fabricated for the first time with copper hexacyanoferrate cathode and polypyrrole (PPy) coated MoO3 anode sandwiched by gel electrolyte. The as-assembled Al-ion battery based on intercalation chemistry exhibits an excellent cycling stability of 83.2% capacity retention after 100 cycles and good rate capability benefiting from the conductive PPy coating layer on MoO3 anode. Besides, the battery demonstrates impressive flexibility and safety to sustain various deformations and mechanical abuse including bending, squeezing, folding, twisting as well as arbitrary drilling and tailoring into any desired shapes. Obviously, the flexible aqueous Al-ion battery developed in this study paves the way of multivalent metal ion battery as energy storage device towards various wearable electronics.

Propelling Polysulfide Conversion by Defect-Rich MoS2 Nanosheets for High-Performance Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries have tremendous energy density and are cost effective and environmentally compatible, thereby deemed one of the most promising secondary energy storage systems. However, Li-S batteries present sluggish polysulfide intermediate redox kinetics due to the unavoidable "shuttle effect", thus hindering their industrialization and resulting in low sulfur utilization, rapid capacity fading, poor Coulombic efficiency, and anode corrosion. Herein, the present study updates a one-step hydrothermal method to synthesize a highly efficient sulfur host integrating three-dimensional porous graphene aerogel (GA) with uniformly dispersed defect-rich MoS2 nanosheets (200-300 nm) (GA-DR-MoS2). The electrochemical studies reveal that these MoS2 nanosheets with abundant defects could provide strong chemical adsorption for polysulfides, as well as act as an electrocatalyst to markedly accelerate polysulfide redox reactions during the charge/discharge process. The resultant GA-DR-MoS2 composites (70 wt % of sulfur loading) present a high initial discharge capacity of 1429 mAh g-1 at 0.2C, an outstanding cycling stability with a low capacity decay rate of 0.085% per cycle over 500 cycles at 0.2C, and a superior rate performance with an improved capacity from 290 to 581 mAh g-1 at 5C. The presented strategy is effective in achieving high-energy-density Li-S batteries from the point of electrocatalysis and facilitating their practical applications.

Bi-structural fibers of carbon nanotube coated with nitrogen/oxygen dual-doped porous carbon layer as superior sulfur host for lithium-sulfur batteries

Lithium-sulfur batteries are one of the most promising secondary energy storage systems. However, their fast capacity fading and low reaction kinetics still remain a challenge. In the present study, a unique bi-structural porous carbon hybrid of fibers with carbon nanotube as core and nitrogen/oxygen dual-doped porous carbon as coating layer is synthesized by a self-assembly approach. The one-dimensional (1D) hybrid has large surface area, high porosity, rich nitrogen/oxygen dual-doping and high conductivity, which is admirable as sulfur host for lithium-sulfur battery cathodes. This novel structural carbon host enables the sulfur cathode a significant cyclic stability and superior rate capability. With a sulfur loading as high as 75 wt%, the sulfur cathode achieves an initial capacity of 1110 mAh g−1 and a capacity of 684 mAh g−1 retains after 200 cycles at 0.2 C. This work offers a new structural 1D porous carbon host and its fabrication method for high efficiency sulfur cathodes.

A Simulation Analysis of Redundancy and Reliability in Primary Storage Deduplication

Deduplication has been widely used to improve storage efficiency in modern primary and secondary storage systems, yet how deduplication fundamentally affects storage system reliability remains debatable. This paper aims to analyze and compare storage system reliability with and without deduplication in primary workloads using public file system snapshots from two research groups. We first study the redundancy characteristics of the file system snapshots. We then propose a trace-driven, deduplication-aware simulation framework to analyze data loss in both chunk and file levels due to sector errors and whole-disk failures. Compared to without deduplication, our analysis shows that deduplication consistently reduces the damage of sector errors due to intra-file redundancy elimination, but potentially increases the damages of whole-disk failures if the highly referenced chunks are not carefully placed on disk. To improve reliability, we examine a deliberate copy technique that stores and repairs first the most referenced chunks in a small dedicated physical area (e.g., 1 percent of the physical capacity), and demonstrate its effectiveness through our simulation framework.