Dynamics-Based Vibration Signal Modeling for Tooth Fault Diagnosis of Planetary Gearboxes

Vibration analysis has been widely used to diagnose gear tooth fault inside a planetary gearbox. However, the vibration characteristics of a planetary gearbox are very complicated. Inside a planetary gearbox, there are multiple vibration sources as several sun-planet gear pairs, and several ring-planet gear pairs are meshing simultaneously. In addition, due to the rotation of the carrier, distance varies between vibration sources and a transducer installed on the planetary gearbox housing. Dynamics-based vibration signal modeling techniques can simulate the vibration signals of a planetary gearbox and reveal the signal generation mechanism and fault features effectively. However, these techniques are basically in the theoretical development stage. Comprehensive experimental validations are required for their future applications in real systems. This chapter describes the methodologies related to vibration signal modeling of a planetary gear set for gear tooth damage diagnosis. The main contents include gear mesh stiffness evaluation, gear tooth crack modeling, dynamic modeling of a planetary gear set, vibration source modeling, modeling of transmission path effect due to the rotation of the carrier, sensor perceived vibration signal modeling, and vibration signal decomposition techniques. The methods presented in this chapter can help understand the vibration properties of planetary gearboxes and give insights into developing new signal processing methods for gear tooth damage diagnosis

Guidelines for Air-Stable Lithium/Sodium Layered Oxide Cathodes

The rational design of intercalation materials plays an indispensable role in continuously improving the performance of rechargeable batteries. The capability of some very promising layered oxide materials for positive electrodes (cathodes), such as sodium layered oxides and Ni-rich lithium layered oxides, are limited by several key challenges. Air stability is one of the issues that should be tackled appropriately. In this Perspective, we present the reaction mechanisms of layered oxides when exposed to moist atmospheres, the critical factors that affect the air stability of layered oxides, and the practical strategies toward air-stable electrodes. Based on the above understandings, we highlighted several pivotal research directions for further investigations of air stability of layered oxides. We expect that continued exploration in understanding the air stability of layered oxides will help to advance the design and lower the expense of cost-effective and high-energy cathodes for Li- and Na-ion battery technologies

Layered Oxide Cathodes for Sodium-Ion Batteries: Storage Mechanism, Electrochemistry, and Techno-economics

Conspectus: Lithium-ion batteries (LIBs) are ubiquitous in all modern portable electronic devices such as mobile phones and laptops as well as for powering hybrid electric vehicles and other large-scale devices. Sodium-ion batteries (NIBs), which possess a similar cell configuration and working mechanism, have already been proven as ideal alternatives for large-scale energy storage systems. The advantages of NIBs are as follows. First, sodium resources are abundantly distributed in the earth’s crust. Second, high-performance NIB cathode materials can be fabricated by using solely inexpensive and noncritical transition metals such as manganese and iron, which further reduces the cost of the required raw materials. Recently, the unprecedented demand for lithium and other critical minerals has driven the cost of these primary raw materials (which are utilized in LIBs) to a historic high and thus triggered the commercialization of NIBs. Sodium layered transition metal oxides (Na$_x$TMO$_2$, TM = transition metal/s), such as Mn-based sodium layered oxides, represent an important family of cathode materials with the potential to reduce costs, increase energy density and cycling stability, and improve the safety of NIBs for large-scale energy storage. However, these layered oxides face several key challenges, including irreversible phase transformations during cycling, poor air stability, complex charge-compensation mechanisms, and relatively high cost of the full cell compared to LiFePO$_4$-based LIBs. Our work has focused on the techno-economic analysis, the degradation mechanism of Na$_x$TMO$_2$ upon cycling and air exposure, and the development of effective strategies to improve their electrochemical performances and air stability. Correlating structure–performance relationships and establishing general design strategies of Na$_x$TMO$_2$ must be considered for the commercialization of NIBs. In this Account, we discuss the recent progress in the development of air-stable, electrochemically stable, and cost-effective Na$_x$TMO$_2$. The favorable redox-active cations for Na$_x$TMO$_2$ are emphasized in terms of abundance, cost, supply, and energy density. Different working mechanisms related to Na$_x$TMO$_2$ are summarized, including the electrochemical reversibility, the main structural transformations during the charge and discharge processes, and the charge-compensation mechanisms that accompany the (de)intercalation of Na$^+$ ions, followed by discussions to improve the stability toward ambient air and upon cycling. Then the techno-economics are presented, with an emphasis on cathodes with different chemical compositions, cost breakdown of battery packs, and Na deficiency, factors that are critical to the large-scale implementation. Finally, this Account concludes with an overview of the remaining challenges and new opportunities concerning the practical applications of Na$_x$TMO$_2$, with an emphasis on the cost, large-scale fabrication capability, and electrochemical performance

Tuning Oxygen Redox Reaction through the Inductive Effect with Proton Insertion in Li-Rich Oxides.

As a parent compound of Li-rich electrodes, Li2MnO3 exhibits high capacity during the initial charge; however, it suffers notoriously low Coulombic efficiency due to oxygen and surface activities. Here, we successfully optimize the oxygen activities toward reversible oxygen redox reactions by intentionally introducing protons into lithium octahedral vacancies in the Li2MnO3 system with its original structural integrity maintained. Combining structural probes, theoretical calculations, and resonant inelastic X-ray scattering results, a moderate coupling between the introduced protons and lattice oxygen at the oxidized state is revealed, which stabilizes the oxygen activities during charging. Such a coupling leads to an unprecedented initial Coulombic efficiency (99.2%) with a greatly improved discharge capacity of 302 mAh g-1 in the protonated Li2MnO3 electrodes. These findings directly demonstrate an effective concept for controlling oxygen activities in Li-rich systems, which is critical for developing high-energy cathodes in batteries

P2-Na0.67 Alx Mn1-x O2 : Cost-Effective, Stable and High-Rate Sodium Electrodes by Suppressing Phase Transitions and Enhancing Sodium Cation Mobility.

Sodium layered P2-stacking Na0.67 MnO2 materials have shown great promise for sodium-ion batteries. However, the undesired Jahn-Teller effect of the Mn4+ /Mn3+ redox couple and multiple biphasic structural transitions during charge/discharge of the materials lead to anisotropic structure expansion and rapid capacity decay. Herein, by introducing abundant Al into the transition-metal layers to decrease the number of Mn3+ , we obtain the low cost pure P2-type Na0.67 Alx Mn1-x O2 (x=0.05, 0.1 and 0.2) materials with high structural stability and promising performance. The Al-doping effect on the long/short range structural evolutions and electrochemical performances is further investigated by combining in situ synchrotron XRD and solid-state NMR techniques. Our results reveal that Al-doping alleviates the phase transformations thus giving rise to better cycling life, and leads to a larger spacing of Na+ layer thus producing a remarkable rate capability of 96 mAh g-1 at 1200 mA g-1

Highly-stable P2-Na 0.67 MnO 2 electrode enabled by lattice tailoring and surface engineering

Abstract(#br)One of the key challenges of sodium ion batteries is to develop sustainable, low-cost and high capacity cathodes, and this is the reason that layered sodium manganese oxides have attracted so much attention. However, the undesired phase transitions and poor electrolyte-electrode interfacial stability facilitate their capacity decay and limit their practical applications. Herein, we design a novel Al 2 O 3 @Na 0.67 Zn 0.1 Mn 0.9 O 2 electrode to mitigate these problems, by taking the advantages of both structural stabilization and surface passivation via Zn 2+ substitution and Al 2 O 3 atomic layered deposition (ALD), respectively. Long-range and local structural analyses during charging/discharging processes indicate that P2-P2’ phase transformation can be suppressed by substituting proper amount of Mn 3+ Jahn-Teller centers with Zn 2+ , whereas excessive Zn 2+ leads to P2-OP4 structure transition at low sodium contents and facilitates the electrode degradations. Furthermore, the homogeneous and robust cathode electrolyte interphase (CEI) layers formed on the Al 2 O 3 -coated electrodes effectively hinder the organic electrolytes from further decomposition. Therefore, our synergetic strategy of Zn 2+ substitution and ALD surface engineering remarkably boosts the cycling performance of P2-Na 0.67 MnO 2 and provides some new insights into the designing of highly stable cathode electrodes for sustainable sodium ion batteries

Direct Growth of Bismuth Film as Anode for Aqueous Rechargeable Batteries in LiOH, NaOH and KOH Electrolytes

As promising candidates for next-generation energy storage devices, aqueous rechargeable batteries are safer and cheaper than organic Li ion batteries. But due to the narrow voltage window of aqueous electrolytes, proper anode materials with low redox potential and high capacity are quite rare. In this work, bismuth electrode film was directly grown by a facile hydrothermal route and tested in LiOH, NaOH and KOH electrolytes. With low redox potential (reduction/oxidation potentials at ca. −0.85/−0.52 V vs. SCE, respectively) and high specific capacity (170 mAh·g−1 at current density of 0.5 A·g−1 in KOH electrolyte), Bi was demonstrated as a suitable anode material for aqueous batteries. Furthermore, by electrochemical impedance spectroscopy (EIS) analysis, we found that with smaller Rs and faster ion diffusion coefficient, Bi electrode film in KOH electrolyte exhibited better electrochemical performance than in LiOH and NaOH electrolytes

Direct Growth of Bismuth Film as Anode for Aqueous Rechargeable Batteries in LiOH, NaOH and KOH Electrolytes

As promising candidates for next-generation energy storage devices, aqueous rechargeable batteries are safer and cheaper than organic Li ion batteries. But due to the narrow voltage window of aqueous electrolytes, proper anode materials with low redox potential and high capacity are quite rare. In this work, bismuth electrode film was directly grown by a facile hydrothermal route and tested in LiOH, NaOH and KOH electrolytes. With low redox potential (reduction/oxidation potentials at ca. −0.85/−0.52 V vs. SCE, respectively) and high specific capacity (170 mAh·g−1 at current density of 0.5 A·g−1 in KOH electrolyte), Bi was demonstrated as a suitable anode material for aqueous batteries. Furthermore, by electrochemical impedance spectroscopy (EIS) analysis, we found that with smaller Rs and faster ion diffusion coefficient, Bi electrode film in KOH electrolyte exhibited better electrochemical performance than in LiOH and NaOH electrolytes