Irreversible Phases Research Articles

Study on the impact of cutoff voltage on structural and electrochemical stability of sodium-ion layered cathodes

NaNi1/3Fe1/3Mn1/3O2 is recognized for its relatively high theoretical specific capacity and operating voltage, rendering it a sodium-ion cathode material with significant commercial potential. A higher cutoff voltage typically enables more sodium ion deintercalation, thereby achieving higher capacity. However, this increased deintercalation can introduce challenges such as structural instability and side reactions with the electrolyte, leading to electrochemical performance degradation. This study focuses on the migration process of transition metal ions under conditions of high charging cutoff voltage and high sodium removal. At a voltage of 4.3 V, the migration of Ni ions facilitates more charge compensation but is accompanied by irreversible Ni migration, inducing an irreversible phase transition to the O’ phase. Conversely, at a cutoff voltage of 4.1 V, the P3 and O3 phases with high sodium removal demonstrate excellent cycling stability. The specific capacities before and after 150 cycles (at 0.5C) are 142.3 and 113.7 mAh/g, respectively, indicating a tolerable internal structural stress within these high sodium removal phases. This contrasts with the differentiated internal structural stresses generated by the P3, O3, and O’ phases during phase transitions at a cutoff voltage of 4.3 V. The research underscores the importance of regulating reversible crystal phases within the tolerance range of internal stress and avoiding irreversible crystal phases to enhance the cycling stability of cathode materials. These findings provide crucial insights for optimizing NNFMO cathode materials and hold significant implications for the design of high-performance, long-life sodium-ion batteries.

Pathophysiological Approach of Myocardial Infarction: A Review

Coronary artery disease (CAD) is the primary cause of myocardial infarction (MI), which is defined by a decreased or stopped blood supply to a portion of the heart myocardium, resulting in cardiac cell death. Because CAD robs the heart of oxygen supply, it frequently presents as silently or with symptoms like radiating chest pain to the shoulder, arm, neck, or jaw. Elevated cardiac troponins and ECG alterations are involved in the diagnosis. MI is caused by prolonged blockage of a major coronary artery; collateral circulation, hemodynamics, and residual blood flow all affect the size of the infarct. Atherosclerosis, thrombosis, and plaque erosion are the primary causes of ST-elevation MI (STEMI) and non-ST-elevation MI (NSTEMI). Male pattern baldness, advancing age, a family history of the condition, high cholesterol, smoking, hypertension, diabetes, obesity, and stress are risk factors for MI. Aortic dissection, drug misuse, and anomalies in the heart are further causes. Anaerobic respiration and lactate buildup are the results of tissue oxygen deprivation, which starts both reversible and irreversible phases of Myocardial infarction. Oxidative stress and endothelial dysfunction, in conjunction with inflammation and susceptible plaques, worsen the development of MI. Significant MI risks are highlighted by epidemiological research on smoking, obesity, diabetes, hypertension, and socioeconomic variables. Other factors include family history and genetic predisposition. Given that MI continues to be a major cause of morbidity and death worldwide, an understanding of its pathophysiology and risk factors is essential for both prevention and intervention. To lessen the effects of this terrible illness, effective strategies require prompt intervention and thorough risk factor control.

Ti, F Codoped Sodium Manganate of Layered P2-Na 0.7 MnO 2.05 Cathode for High Capacity and Long-Life Sodium-Ion Battery

Open AccessRenewablesRESEARCH ARTICLES14 Jan 2023Ti, F co-doped Sodium Manganate of Layered P2-Na0.7MnO2.05 Cathode for High Capacity and Long-life Sodium Ion Battery Pengchao Wen, Haodong Shi, Dandan Guo, Aimin Wang, Yan Yu and Zhong-Shuai Wu Pengchao Wen Google Scholar More articles by this author , Haodong Shi Google Scholar More articles by this author , Dandan Guo Google Scholar More articles by this author , Aimin Wang Google Scholar More articles by this author , Yan Yu Google Scholar More articles by this author and Zhong-Shuai Wu Google Scholar More articles by this author https://doi.org/10.31635/renewables.022.202200012 SectionsSupplemental MaterialAboutPDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareFacebookTwitterLinked InEmail The development of layered sodium manganese oxides cathode materials with high capacity and structural stability is one of the keys to boost the performance of sodium-ion batteries (SIBs), but remains a great challenge. Herein, a titanium and fluorine co-doped P2 type sodium manganate of Na0.7MnO2.05 cathode material (NMO-0.1TF) is developed as high-capacity and long-durable cathode for high-performance SIBs. The titanium and fluorine co-doping could significantly reduce the structural deformation, synergistically improved structural stabilization, inhibit the formation of irreversible phases and enhance electrochemical kinetics. As a result, the NMO-0.1TF||Na battery working in the voltage ranges of 2.0-4.2 V exhibits a high specific capacity of 227 mAh g-1 at current density of 20 mA g-1, and excellent rate performance (76 mAh g-1 at a high current density of 3 A g-1). Such battery still delivers an outstanding cycle stability, shows a high initial discharge capacity of 133 mAh g-1 at 1 A g-1, and maintains the initial capacity of 96.2% after 200 cycles. More importantly, the assembled full battery of NMO-0.1TF||hard carbon validates high capacity and impressive cyclability. Therefore, this co-doped NMO-0.1TF cathode with high capacity and excellent stability presents brilliantly practical application for developing high energy density SIBs. Download figure Download PowerPoint Previous articleNext article FiguresReferencesRelatedDetails Issue AssignmentNot Yet AssignedSupporting Information Copyright & Permissions© 2023 Chinese Chemical Society Downloaded 7 times PDF downloadLoading ...

Ti, F Codoped Sodium Manganate of Layered P2-Na 0.7 MnO 2.05 Cathode for High Capacity and Long-Life Sodium-Ion Battery

Ti, F Codoped Sodium Manganate of Layered P2-Na _0.7 MnO _2.05 Cathode for High Capacity and Long-Life Sodium-Ion Battery

An in-depth mechanistic insight into the redox reaction and degradation of aqueous Zn-MnO2 batteries

Rechargeable aqueous Zn/MnO2 batteries raise massive research activities in recent years. However, both the working principle and the degradation mechanism of this battery chemistry are still under debate. Herein, we provide an in-depth electrochemical and structural investigation on this controversial issue based on α-MnO2 crystalline nanowires. Mechanistic analysis substantiates a two-electron reaction pathway of Mn2+/Mn4+ redox couple from part of MnO2 accompanying with a reversible precipitation/dissolution of flaky zinc sulfate hydroxide (ZSH) during the discharge/charge processes. The formation of the ZSH layer is double-edged, which passivates the deep dissolution of MnO2 upon discharging, but promotes the electrochemical deposition kinetics of active MnO2 upon charging. The cell degradation originates primarily from the corrosion failure of metallic zinc anode and the accumulation of irreversible ZnMn2O4 phases on the cathode. The addition of MnSO4 to the electrolyte could afford supplementary capacity contribution via electro-oxidation of Mn2+. However, a high MnSO4 concentration will expedite the cell failure by corroding the metallic zinc anodes. The present study will shed a fundamental insight on developing new strategies toward practically viable Zn/MnO2 batteries.

Cardiovascular Autonomic Reflex Tests and 7 Heart Rate Variability Indices for Early Diagnosis of Cardiovascular Autonomic Neuropathy in Type 2 Diabetes Individuals.

Cardiovascular autonomic neuropathy (CAN) is a common complication of type 2 Diabetes mellitus (T2D), and prevalence varies according to the methodology used. CAN should be diagnosed in the subclinical stage when an intensive treatment of T2D could avoid the progression to irreversible phases. Determine the prevalence of early involvement (EI) of CAN in T2D individuals comparing two methodologies. This was a cross-sectional study that included 183 T2D individuals who were monitored in a Tertiary centre. The diagnosis of CAN was based on the results of four cardiovascular autonomic reflex tests (CARTs: expiration-inspiration index, Valsalva maneuver, orthostatic test, and changes in blood pressure after standing) and of seven heart rate variability (7HRV) indices (CARTs plus the spectral analysis). The findings were validated in an independent cohort comprised of 562 T2D individuals followed in a Primary care setting. With the use of 7HRV, 30.6% and 77.8% of individuals in the Tertiary and in the Primary centers, respectively, were classified as without CAN; 25.1% and 15.3% as EI and 44.3% and 6.9% as definitive CAN, respectively. The use of CARTs decreased the proportion of individuals without CAN in both centers (7.1% and 47%) and increased the frequency of EI (30.6% and 36.6%) and definitive CAN (62.3% and 16.4%), respectively. The concordance between both evaluated methodologies was weak. Higher proportions of T2D individuals were diagnosed with EI and with definitive CAN with the use of CARTs.

Propagating irreversibility fronts in cyclically sheared suspensions

The interface separating a liquid from its vapor phase is diffuse; the composition varies continuously from one phase to the other over a finite length. Recent experiments on dynamic jamming fronts in two dimensions [Waitukaitis et al., Europhys. Lett. 102, 44001 (2013)] identified a diffuse interface between jammed and unjammed disks. In both cases, the thickness of the interface diverges as a critical transition is approached. We investigate the generality of this behavior using a third system: A model of cyclically sheared non-Brownian suspensions. As we sediment the particles toward a boundary, we observe a diffuse traveling front that marks the interface between irreversible and reversible phases. We argue that the front width is linked to a diverging correlation length scale in the bulk, which we probe by studying avalanches near criticality. Our results show how diffuse interfaces may arise generally when an incompressible phase is brought to a critical point.

Highly Energy-Dense, Rechargeable, Alkaline Birnessite-Zinc Batteries for Grid-Scale Applications

Manganese dioxide (MnO2) and zinc (Zn) are one of the most abundant, safest and cheapest materials available. Together, they are found in common household batteries like Duracell, Energizer, etc. as small cylindrical alkaline cells. These cells or batteries are used as primary batteries, i.e., as single use batteries, where the entire capacity of the battery is delivered once and then discarded. The disadvantage of primary batteries is that it takes a lot of energy to produce the battery than the energy that can be actually obtained from it, and also, it creates environmental waste. However, the manufacturing of primary cells has still been rampant due to the cost of manufacturing MnO2-Zn cells being very cheap. In terms of improving the overall energy efficiency, reducing waste and maintaining its cost advantage, it makes good sense, economically and environmentally, to make MnO2-Zn cells rechargeable. However, the main deterrent to this direction has been the fundamental material and chemical problems of the main raw components, i.e., MnO2 and Zn. Manganese dioxide can theoretically deliver a capacity of approximately 617mAh/g. It delivers this capacity through a 2 electron electrochemical reaction (each electron providing around 308mAh/g). MnO2 has been found to be rechargeable when the capacity has been limited to around 5-10% of the 617mAh/g. It suffers a crystal structure breakdown as more of the capacity is accessed, and it inherently forms electrochemical irreversible phases. If the entire 2 electron capacity can be accessed then theoretically it can reach energy density numbers near lithium-ion batteries. Similar problems are associated with the zinc electrode, where higher utilization of its capacity causes dendrite formation, shape change and formation of inactive zinc oxides that ultimately lead to electrode failure. These are the main deterrent to a cheap and safe battery that could be a disruptive technology in the energy storage field. In this presentation, we report the breakthrough of reversibly accessing the 2nd electron capacity of MnO2 by using its layered polymorph called birnessite mixed with bismuth oxide (Bi-birnessite) and intercalating the layers with Cu ions (1). Bi-birnessite’s undergo conversion reactions in alkaline electrolyte and ultimately form electro-inactive hausmannite (Mn3O4) because of its poor charge transfer characteristics. Intercalating the layers of Bi-birnessite with Cu ions is shown to improve its charge transfer characteristics dramatically and regenerate its layered structure reversibly for thousands of cycles as shown in Figure 1. We also present a case of Cu-intercalated Bi-birnessite’s applicability in practical batteries by cycling the material at high areal capacities (10-29mAh/cm2) for thousands of cycles at C-rates that are of interest in the battery community. For true applicability in practical energy dense batteries its pairing with a Zn anode is essential. The use of Zn anodes has also presented problems as it is the source of zincate ions in electrolyte that react with the cathode, MnO2, to form electro-inactive phase called haeterolite (ZnMn2O4). The best reported cycle life data for high depth-of-discharge (DOD) birnessite cathodes with Zn anodes had been 50 cycles till our recent publication, which showed over 90 cycles achieving 140Wh/L. In this presentation, we also report the effect of zincate ions on the Cu-intercalated Bi-birnessite cathodes beyond 100 cycles (2). The Cu-intercalated Bi-birnessite cathodes when paired with Zn anodes are shown to deliver 160Wh/L and cycle reversibly for over 100 cycles. The Cu ions play an important role in mitigating the detrimental effect of zincate ions in the 100 cycles; however, the zincate ions eventually poison the cathode to form ZnMn2O4. The mechanism through which ZnMn2O4 is formed is presented in detail with the aid of electroanalytical and spectroscopic methods. A solution of trapping the zincate ions is also presented, where the membrane that is used successfully traps the zincate ions from interacting with the cathode and thus, extend cycle life to over 900 cycles as shown in Figure 2. This is the best reported cycle life data with a manganese dioxide cathode accessing the near 2nd electron capacity paired with Zn anodes.

Engineering the Next Generation of High Energy Dense Zinc-Anode Batteries By Accessing the Theoretical Second Electron Capacity of Manganese Dioxide

Manganese dioxide (MnO2) and zinc (Zn) are one of the most abundant, safest and cheapest materials available. Together, they are found in common household batteries like Duracell, Energizer, etc. as small cylindrical alkaline cells. These cells or batteries are used as primary batteries, i.e., as single use batteries, where the entire capacity of the battery is delivered once and then discarded. The disadvantage of primary batteries is that it takes a lot of energy to produce the battery than the energy that can be actually obtained from it, and also, it creates environmental waste. However, the manufacturing of primary cells has still been rampant due to the cost of manufacturing MnO2-Zn cells being very cheap. In terms of improving the overall energy efficiency, reducing waste and maintaining its cost advantage, it makes good sense, economically and environmentally, to make MnO2-Zn cells rechargeable. However, the main deterrent to this direction has been the fundamental material and chemical problems of the main raw components, i.e., MnO2 and Zn. Manganese dioxide can theoretically deliver a capacity of approximately 617mAh/g. It delivers this capacity through a 2 electron electrochemical reaction (each electron providing around 308mAh/g). MnO2 has been found to be rechargeable when the capacity has been limited to around 5-10% of the 617mAh/g. It suffers a crystal structure breakdown as more of the capacity is accessed, and it inherently forms electrochemical irreversible phases. If the entire 2 electron capacity can be accessed then theoretically it can reach energy density numbers near lithium-ion batteries. Similar problems are associated with the zinc electrode, where higher utilization of its capacity causes dendrite formation, shape change and formation of inactive zinc oxides that ultimately lead to electrode failure. These are the main deterrent to a cheap and safe battery that could be a disruptive technology in the energy storage field. In this presentation, we report the breakthrough of reversibly accessing the 2nd electron capacity of MnO2 by using its layered polymorph called birnessite mixed with bismuth oxide (Bi-birnessite) and intercalating the layers with Cu ions (1). Bi-birnessite’s undergo conversion reactions in alkaline electrolyte and ultimately form electro-inactive hausmannite (Mn3O4) because of its poor charge transfer characteristics. Intercalating the layers of Bi-birnessite with Cu ions is shown to improve its charge transfer characteristics dramatically and regenerate its layered structure reversibly for thousands of cycles. We also present a case of Cu-intercalated Bi-birnessite’s applicability in practical batteries by cycling the material at high areal capacities (10-29mAh/cm2) for thousands of cycles at C-rates that are of interest in the battery community. For true applicability in practical energy dense batteries its pairing with a Zn anode is essential. The use of Zn anodes has also presented problems as it is the source of zincate ions in electrolyte that react with the cathode, MnO2, to form electro-inactive phase called haeterolite (ZnMn2O4). The best reported cycle life data for high depth-of-discharge (DOD) birnessite cathodes with Zn anodes had been 50 cycles till our recent publication, which showed over 90 cycles achieving 140Wh/L. In this presentation, we also report the effect of zincate ions on the Cu-intercalated Bi-birnessite cathodes beyond 100 cycles (2). The Cu-intercalated Bi-birnessite cathodes when paired with Zn anodes are shown to deliver 160Wh/L and cycle reversibly for over 100 cycles. The Cu ions play an important role in mitigating the detrimental effect of zincate ions in the 100 cycles; however, the zincate ions eventually poison the cathode to form ZnMn2O4. The mechanism through which ZnMn2O4 is formed is presented in detail with the aid of electroanalytical and spectroscopic methods. A solution of trapping the zincate ions is also presented, where the membrane that is used successfully traps the zincate ions from interacting with the cathode and thus, extend cycle life to over 900 cycles. This is the best reported cycle life data with a manganese dioxide cathode accessing the near 2nd electron capacity paired with Zn anodes. 1] Yadav, G. G.; Gallaway, J. W.; Turney, D. E.; Nyce, M.; Huang, J.; Wei, X.; Banerjee, S. “Regenerable Cu-intercalated MnO2 layered cathode for highly cyclable energy dense batteries” Nat. Commun. 8, 14424 (2017). 2] Yadav, G. G.; Wei, X.; Huang, J.; Gallaway, J. W.; Turney, D. E.; Nyce, M.; Secor, J.; Banerjee, S., J. Mater. Chem. A, 2017, 5 (30), 15845-15854

Modeling of the combustion synthesis of titanium based composite with detailed reaction schema

The model of composite synthesis from powders of titanium and boron is proposed in this paper. Mathematical model takes into account the dependence of effective properties powders mixture on the composition and structure of reaction mixture. The ignition stage, the formation irreversible phases and reaction retardation by reaction product are also considered in the model. The reaction scheme of the composite synthesis process includes the system of four kinetic equations describing the formation of different titanium borides. Results of modeling for non-stoihiometric composition of the reaction mixture are presented and discussed.

Illumination‐Induced Halide Segregation in Gradient Bandgap Mixed‐Halide Perovskite Nanoplatelets

AbstractEfficient energy funneling has exhibited great contribution to the high performance of perovskite‐based optoelectronic devices. Here, formamidinium (FA+, HC(NH2)2+) lead mixed‐halide nanoplatelets (FAPb(BrxI1−x)3) with gradient bandgap are fabricated using chemical vapor deposition followed with bromide–iodide substitution by exposure to FABr vapor. The as‐fabricated perovskite nanoplatelets exhibit pure bromide phase in the thin nanoplatelet (tens of nanometers) and a gradual bromide–iodide composite, thus with gradient bandgap (2.29–1.56 eV), in the thick nanoplatelet (more than hundreds of nanometers). Accordingly, photoluminescence (PL) spectra are observed at 540, 560/610, and 735/790 nm, respectively. In such gradient bandgap structures, photogenerated carriers can effectively transfer and emit in the low‐bandgap region by energy funneling. With illumination, the PL spectrum of Br‐rich phase exhibits blueshift and therefore 610 nm band disappears. In contrast, redshift is observed in I‐rich phase due to the decrease of 735 nm band while an increase of 790 nm band. It is demonstrated that irreversible and stable phases are formed with illumination in both Br‐rich and I‐rich nanoplatelets. This investigation develops a method to fabricate gradient bandgap perovskites with designed energy funneling, and also provides significant insight into the halide segregation in such special perovskites, which greatly benefits their future optoelectronic applications.

Rechargeability of aqueous sulfate Zn/MnO2 batteries enhanced by accessible Mn2+ ions

The Zn/MnO2 battery is safe, low cost and comes with a high energy density comparable to Li-ion batteries. However, irreversible spinel phases formed at the MnO2 electrode limits its cyclability. A viable solution to overcome this inactive phase is to use an aqueous ZnSO4-based electrolyte, where pH is mildly acidic leading to a different reaction mechanism. Most importantly, the addition of MnSO4 achieves excellent cyclability. How accessible Mn2+ ions in the electrolyte enhances the reversibility is presented. With added Mn2+, the capacity retention is significantly improved over 100 cycles. Zn2+ insertion plays an important role on the reversibility and a hydrated layered Zn-buserite structure formed during charge is reported. Furthermore, Zn4SO4(OH)6 · 5H2O precipitates during discharge but is not involved in the electrochemical reaction. This precipitate both buffers the pH and partly insulates the surface. Described in operando study show how the phase transformations and the failure mechanisms depend on the presence of Mn2+-ions in the electrolyte. These results give insight necessary to improve this battery further to make it a worthy contender to the Li-ion battery in large scale energy storage solutions.

Rapid electrochemical synthesis of δ-MnO2 from γ-MnO2 and unleashing its performance as an energy dense electrode

Birnessite (δ-MnO2) is a layered polymorph of manganese dioxide used in a number of applications because of its low cost and non-toxic characteristics. In organic electrolyte battery chemistry's it has been considered as an insertion electrode for lithium, magnesium and other ions. In an alkaline environment, however, it undergoes conversion reactions. It has a high theoretical specific capacity of 617 mAh/g based on two electron reactions making it an energy dense electrode. However, its implementation in practice has been limited due to complicated, time cumbersome synthesis methods, and formation of electrochemical irreversible phases after a few cycles. In this article, we report the rapid synthesis and study of the electrochemical synthesis of δ-MnO2 from cheap and commercially available electrolytic manganese dioxide (EMD, γ-MnO2), where we find the formation to proceed from γ-MnO2 to groutite (α-MnOOH) and pyrochroite [Mn(OH)2] on the first discharge and follow the reverse transition on the immediate charge to form δ-MnO2 in alkaline electrolyte. The formation process takes only one cycle to completely form δ-MnO2. The electrochemical reversibility of δ-MnO2 formed through this process is also addressed, where we find that avoiding hydrophobic binders, use of appropriate carbons, addition of certain metallic additives and possibly porosity/pore structure play an important role in unleashing its energy-dense electrochemical performance.

Impact of BaSO4 Additive on the Cycling Performance of MnO2/Zn Alkaline Batteries

A detailed electrochemical investigation of BaSO4 as an additive in the electrolytic manganese dioxide (EMD)-based cathode of MnO2/Zn batteries is presented. The addition of BaSO4 appears to have a positive impact on the cycling performance of EMD, but only during the first 50 cycles. The loss of EMD structure and formation of irreversible phases still remain challenging factors in the electrochemical cycling of the EMD materials.

PH-Controlled Electrolysis of Electrolytic Manganese Dioxide (EMD) for Improved Cycle Life of Rechargeable MnO2/Zn Batteries

A systematic study of the effect of acid concentration (0.5–5 M H2SO4) on the electrolysis of electrolytic manganese dioxide (EMD or γ-MnO2) has been performed. All the samples were characterized for their phase and crystallinity, their structural water, the pyrolusitic-to-ramsdellite ratio, BET surface area, pore size range; and were examined for their electrochemical performance. Concentration of the electrolysis acid affects the structural water content and the pyrolusitic-to-ramsdellite ratio of the γ-MnO2 phase as well as the surface area and pore size. The best cycling performance was achieved for the samples prepared with an electrolysis bath containing an acid concentration of about 2 M H2SO4. Electrochemical performance over 100 cycles of the EMD prepared in 2 M H2SO4 has shown higher energy efficiency and improved longer term cycling performance compared to commercial EMD products. Post-mortem analysis of the cycled EMD samples show partial loss of the EMD phase, loss of water content, and growth of irreversible manganese dioxide phases.

In Situ EXAFS Study of Tin Phosphide/Graphite Composite Anodes for Lithium-Ion Batteries

Lithium-ion batteries (LIBs) have become the primary power source for portable electronics and hybrid and electric vehicles. The rapid growth applications of LIBs require significant improvement in their capacity, energy density and cycle life. Sn-based materials are alternatives to replace the traditional most widely used anode material, graphite, which only offers a capacity of 372 mAh/g. Metallic tin or tin oxide can achieve initial capacities over 1000 mAh/g. However, these materials suffer from volume expansion and formation of irreversible phases during lithiation that degrade the capacity and battery performance rapidly. A layered structure material tin phosphide (Sn4P3) is a promising anode material with a high initial capacity of over 1200 mAh/g. Lithiation of Sn4P3 starts with a conversion reaction that forms metallic tin and lithium phosphide, followed by a lithium-tin alloying reaction. Although Li3P is a better lithium-ion conductor than Li2O, Sn4P3 still suffers from a large volume change during the initial lithiation and the irreversible formation of Li3P. This study focuses on the characterization of Sn4P3 and Sn4P3/graphite composites synthesized by high-energy ball milling using red phosphorus and tin nanoparticles under Ar atmosphere. The capacity of pure Sn4P3 rapidly decreases to around 200 mAh/g after 15 cycles. In contrast, Sn4P3/graphite composites exhibit excellent electrochemical performance and durability with a capacity of 610 mAh/g at 0.4 C after 100 cycles. In addition, the coulombic efficiency was also much higher in the Sn4P3/graphite composites, indicating a reversible lithiation/delithiation behavior and more stable SEI layer formation. In situ extended x-ray absorption fine structure (EXAFS) measurements were performed to study the local environment changes around Sn atoms during the lithiation/delithiation process. EXAFS scans of the cell were taken continuously and were analyzed as a function of different charged and discharged states. It is evident that the local Sn environment in the Sn4P3/graphite composite is fully reversible on lithiation/delithiation while the local Sn environment of pure Sn4P3 changes irreversibly after several cycles consistent with the electrochemical results. A mechanism for performance degradation of Sn4P3 and cycling durability of Sn4P3/graphite composites is proposed based on modeling of the EXAFS data.

Si 나노입자에서 shell이 전기화학적 특성에 미치는 영향

Effects of SiOx or C shells on electrochemical properties of Si nanoparticles were investigated. SiOx shells with thickness of 10~15 nm were formed on homogeneously crystalline Si nanoparticles. Incase of Si-C nanoparticles, there were 30~40 layers of C with a number of defects. Li-ion batteries were fabricated with the above-mentioned nanoparticles, and their electrochemical properties were measured. Pristine Si shows a high IRC (initial reversible capacity) of 2,517 mAh/g and ICE (initial columbic efficiency) of 87%, but low capacity retention of 22%, respectively. SiOx shells decreased IRC (1,534 mAh/g) and ICE (54%), while the retention increased up to 65%, which can be explained by irreversible phases such as LiO2 and Li2SiO3. C shells exhibited no differences in IRC and ICE compared to the pristine Si but an enhanced retention of 54%, which might be from proper defect structures.

Advanced Alkaline MnO2-Zn Batteries: Accessing the Second Electron Capacity

Manganese dioxide (MnO2) and zinc (Zn) are one of the most abundant, safest and cheapest materials available. Together, they are found in common household batteries like Duracell, Energizer, etc. as small cylindrical alkaline cells. These cells or batteries are used as primary batteries, i.e., as single use batteries, where the entire capacity of the battery is delivered once and then discarded. The disadvantage of primary batteries is that it takes a lot of energy to produce the battery than the energy that can be actually obtained from it, and also, it creates environmental waste. However, the manufacturing of primary cells has still been rampant due to the cost of manufacturing MnO2-Zn cells being very cheap. In terms of improving the overall energy efficiency, reducing waste and maintaining its cost advantage, it makes good sense, economically and environmentally, to make MnO2-Zn cells rechargeable. However, the main deterrent to this direction has been the fundamental material and chemical problems of the main raw components, i.e., MnO2and Zn. Manganese dioxide can theoretically deliver a capacity of approximately 617mAh/g. It delivers this capacity through a 2 electron electrochemical reaction (each electron providing around 308mAh/g). MnO2has been found to be rechargeable when the capacity has been limited to around 5-10% of the 617mAh/g. It suffers a crystal structure breakdown as more of the capacity is accessed, and it inherently forms electrochemical irreversible phases. If the entire 2 electron capacity can be accessed then theoretically it can reach energy density numbers near lithium-ion batteries. Similar problems are associated with the zinc electrode, where higher utilization of its capacity causes dendrite formation, shape change and formation of inactive zinc oxides that ultimately lead to electrode failure. These are the main deterrent to a cheap and safe battery that could be a disruptive technology in the energy storage field. At the CUNY Energy Institute, we have made a breakthrough in accessing the second electron capacity by altering the crystal structure of manganese dioxide.through dopants and novel and cheap synthesis routes. We have cycled the MnO2 electrode to well over 3000 cycles at rates that are of interest in the battery community. Characterization techniques have shown that the CUNY modified MnO2 is able to maintain its crystal structure and limit the formation of inactive phase hausmannite (Mn3O4) which makes it cycle for thousands of cycles. A 50Ah CUNY modified MnO2 –Zn cell has also been built and cycled well beyond 50 cycles (still running). The cell demonstrates that by accessing the full second electron capacity we can achieve high energy density’s that are theoretically possible of alkaline battery technology. Also, in this talk I will go through the various breakthroughs that have been made at the CUNY Energy Institute with regards to solving other fundamental problems and the scope of these batteries in the current market. Figure 1

Improvement of irreversible behavior of SiO anodes for lithium ion batteries by a solid state reaction at high temperature

Herein, we describe a new simple method to improve the irreversible performance of a SiO anode during the initial cycle. The solid state-reacted SiO material was synthesized from bare SiO and lithium powders (three samples with weight ratios of 7:1, 8:1, and 9:1 were prepared) using a heat treatment process at 600 °C. Irreversible phases such as lithium silicates (Li4SiO4 and Li2SiO3) and Li2O were formed upon the solid state reaction with SiO. Electrochemical tests using half-cells were performed to confirm the effects of the solid state-reacted SiO material. The initial Coulombic efficiencies of the three samples were 82.12% (7:1), 79.81% (8:1), and 78.95% (9:1), which were far higher than that of a bare SiO cell (58.52%). Furthermore, the electrochemical performance of a full cell using a 7:1 wt% SiO anode and a lithium cobalt oxide cathode was evaluated. The full cell exhibited an initial Coulombic efficiency of 93.62% and a capacity retention of 74.70% after 15 cycles, which were also far higher than those of a bare SiO cell (66.4% and 55.72%, respectively). A comparison of the solid state-reacted and bare SiO electrodes demonstrated that the pre-formed irreversible phases prevented the consumption of lithium ions during the 1st cycle.

Enhancement of Irreversible Capacity By Pre-Formed Lithium Silicates and Lithium Oxide in Sio Anode for Lithium Ion Battery

This study focuses on effect of improved irreversible capacity in SiO anode. Irreversible phases such as Li4SiO4, Li2SiO3, Li2O were synthesized by a solid state reaction using a mixture composed of 70 wt% SiO powder and 10 wt% Li-powder. The mixture was mixed by homogenizer and was heated at 600 °C for 2 h in an argon atmosphere. The irreversible phases were observed by XRD, XPS and TEM. Irreversible phases-formed SiO/lithium metal coin cells (2032) were assembled in a dry room. The discharge-charge cycling was performed with cut-off voltage of 0-1.5V. The electrochemical characteristics of the irreversible phases-formed SiO anode were rationalized through impedance analysis, cycle data and voltage profile. The irreversible phases-formed SiO anode’s capacities were 1265.36 mAh g-1 (lithiation) and 1052.03 mAh g-1 (delithiation) after first cycle. The reversible capacity of irreversible phases-formed SiO /lithium metal cells was estimated 83.14% in 1st cycle. It’s larger than pristine SiO/lithium metal which has 60.08%. Figure 1