High Voltage Safety Research Articles

Advanced earth grid monitoring for HV network safety compliance

ABSTRACT Electrical energy is a critical component for human comfort, but mismanagement of this energy can lead to human injury and even fatalities. High voltage safety compliance hinges on the presence of an adequate earthing system within the infrastructure. Various factors influence the effectiveness of the earthing system, including soil resistivity in the surrounding area and the availability of auxiliary paths for fault currents. Weather conditions, changes in the surrounding environment, and alterations within the high-voltage network significantly impact these elements. Any modifications to the auxiliary path conditions can have severe consequences on the network’s safety compliance. The current industry practice lacks continuous monitoring of the earth grid and fault current paths, with no provision for frequent current injection tests on the entire earth grid system. To close the existing gap, this paper proposes a novel approach through the introduction of an Earthing IoT Monitoring system. This system enables network owners to monitor safety compliance across the entire network, identify fault current return paths, and pinpoint any necessary preventive maintenance measures. The paper also delves into the crucial roles played by soil resistivity and split factors in the earthing system domain. A case study is included to support the innovative nature of the proposed system.

Transmission line earthing system; Advanced design diagram for safety compliance

An electrical high-voltage power system is essential to support everyday electrical demands. Due to the increase in electrical loads, a more rigid design is required to ensure system compliance with standards and policies. High-voltage safety is the number one priority when it comes to the design, installation, commissioning, and operation of the electrical power system network. Safety compliance is getting more complex due to the joining infrastructure between residential and high-voltage projects. Nowadays, high-voltage infrastructure, including substations and transmission lines, is constructed near residential properties. This neighboring setup increased the safety concerns of high voltage systems, especially under fault or system malfunction situations. Safety concerns are addressed during the design stage and verified during the commissioning stages.The paper discusses the minimum transmission line earthing system requirements. This document provides a clear and consistent approach to assess transmission line earthing system design. The work contents comply with current IEEE standards including rigid author research outcomes. The works reduce the complexity of the assessment and explain the critical role of different sectors within the transmission line network. The work introduces the boundaries when the fault current analysis should include the earth grid resistance. A case study is also included.

Noncombustible gel polymer electrolyte inspired by bio-radical chemistry for high voltage and high safety Ni-rich lithium batteries

For high energy density lithium-ion batteries (LIBs) with nickel-rich ternary cathodes, the chemical degradation of electrolytes caused by free radical reactions and the hazards of thermal runaway have always been significant challenges. Inspired by the free radical scavenging of living organisms and multiphase synergistic flame retardant mechanism, we innovatively designed and prepared a multifunctional flame retardant HCCP-TMP that combines flame retardancy and free radical scavenging by combining hindered amine and cyclophosphazene. Only 1 wt% HCCP-TMP can make the polyacrylate-based gel polymer electrolyte (GPE) incombustible. Moreover, the equipped NCM811//Graphite pouch cells don't exhibit combustion behavior after thermal runaway and can resist mechanical abuse. Based on the above noncombustible GPE, the NCM811//Li battery exhibits capacity retention rate of 82.2 % after 100 cycles at a current density of 2 C and in the voltage range of 3.0–4.7 V, exhibiting excellent cyclability under high voltage. This simple molecular design simultaneously improves the fire safety and high voltage stability, demonstrating enormous application potential in the field of advanced LIBs with high safety and high energy density.

Initiating a High‐Rate and Stable Aqueous Air Battery by Using Organic N‐Heterocycle Anode

AbstractAlkaline metal‐air batteries are advantageous in high voltage, low cost, and high safety. However, metal anodes are heavily eroded in strong alkaline electrolytes, causing serious side reactions including dendrite growth, passivation, and hydrogen evolution. To address this limitation, we successfully synthesized an organic N‐heterocycle compound (NHCC) to serve as an alternative anode. This compound not only exhibits remarkable stability but also possesses a low redox potential (−1.04 V vs. Hg/HgO) in alkaline environments. To effectively complement the low redox potential of the NHCC anode, we designed a dual‐salt highly concentrated electrolyte (4.0 M KOH+10.0 M KCF3SO3). This electrolyte expands the electrochemical stability window to 2.3 V through the robust interaction between the O atom in H2O molecule with the K+ of KCF3SO3 (H−O⋅⋅⋅KCF3SO3). We further demonstrated the K+ uptaken/extraction storage mechanism of NHCC anodes. Consequently, the alkaline aqueous NHCC anode‐air batteries delivers a high battery voltage of 1.6 V, high‐rate performance (101.9 mAh g−1 at 100 A g−1) and long cycle ability (30,000 cycles). Our work offers a molecular engineering strategy for superior organic anode materials and develops a novel double superconcentrated conductive salt electrolyte for the construction of high‐rate, long‐cycle alkaline aqueous organic anode‐air batteries.

Initiating a High-Rate and Stable Aqueous Air Battery by Using Organic N-Heterocycle Anode.

Alkaline metal-air batteries are advantageous in high voltage, low cost, and high safety. However, metal anodes are heavily eroded in strong alkaline electrolytes, causing serious side reactions including dendrite growth, passivation, and hydrogen evolution. To address this limitation, we successfully synthesized an organic N-heterocycle compound (NHCC) to serve as an alternative anode. This compound not only exhibits remarkable stability but also possesses a low redox potential (-1.04 V vs. Hg/HgO) in alkaline environments. To effectively complement the low redox potential of the NHCC anode, we designed a dual-salt highly concentrated electrolyte (4.0 M KOH+10.0 M KCF3 SO3 ). This electrolyte expands the electrochemical stability window to 2.3 V through the robust interaction between the O atom in H2 O molecule with the K+ of KCF3 SO3 (H-O⋅⋅⋅KCF3 SO3 ). We further demonstrated the K+ uptaken/extraction storage mechanism of NHCC anodes. Consequently, the alkaline aqueous NHCC anode-air batteries delivers a high battery voltage of 1.6 V, high-rate performance (101.9 mAh g-1 at 100 A g-1 ) and long cycle ability (30,000 cycles). Our work offers a molecular engineering strategy for superior organic anode materials and develops a novel double superconcentrated conductive salt electrolyte for the construction of high-rate, long-cycle alkaline aqueous organic anode-air batteries.

High voltage in nuclear applications: Occupational safety aspects and standards

High voltage (HV) plays diverse and critical roles that in both nuclear power generation and nuclear instrumentation, contributing to the efficiency, safety, and precision of various processes within the nuclear domain. The basic detection component of nuclear instruments is the nuclear detector, which needs direct current HV power supply. Exposure to HV electrical systems can cause serious injuries, fatalities, and damage to equipment if proper safety measures are not followed. Comprehensive safety measures, such as proper training, adherence to safety procedures, use of personal protective equipment, equipment maintenance, regular inspections, and compliance with relevant safety standards and regulations, are essential to mitigate hazards arising from HV applications. HV safety and standards are critical aspects of HV occupational practices as they ensure the protection of personnel, machine, and workplace safety. A close study points to certain inadequacies and weaknesses in the existing standards. These include a lack of universal standards, insufficient coverage of nonelectric hazards or indirect safety hazards, deficient or no focus on human factors, and limited consideration of evolving and new technologies. In the last portion of this article, the standards followed at the High Voltage Pulsed Power Lab, Control Instrumentation Division, BARC are discussed along with the safety practices that are observed in the routine operation of different high voltage systems.

High-Performance Dual-Ion Battery Based on Silicon-Graphene Composite Anode and Expanded Graphite Cathode.

Dual-ion batteries (DIBs) are a new kind of energy storage device that store energy involving the intercalation of both anions and cations on the cathode and anode simultaneously. They feature high output voltage, low cost, and good safety. Graphite was usually used as the cathode electrode because it could accommodate the intercalation of anions (i.e., PF6-, BF4-, ClO4-) at high cut-off voltages (up to 5.2 V vs. Li+/Li). The alloying-type anode of Si can react with cations and boost an extreme theoretic storage capacity of 4200 mAh g-1. Therefore, it is an efficient method to improve the energy density of DIBs by combining graphite cathodes with high-capacity silicon anodes. However, the huge volume expansion and poor electrical conductivity of Si hinders its practical application. Up to now, there have been only a few reports about exploring Si as an anode in DIBs. Herein, we prepared a strongly coupled silicon and graphene composite (Si@G) anode through in-situ electrostatic self-assembly and a post-annealing reduction process and investigated it as an anode in full DIBs together with home-made expanded graphite (EG) as a fast kinetic cathode. Half-cell tests showed that the as-prepared Si@G anode could retain a maximum specific capacity of 1182.4 mAh g-1 after 100 cycles, whereas the bare Si anode only maintained 435.8 mAh g-1. Moreover, the full Si@G//EG DIBs achieved a high energy density of 367.84 Wh kg-1 at a power density of 855.43 W kg-1. The impressed electrochemical performances could be ascribed to the controlled volume expansion and improved conductivity as well as matched kinetics between the anode and cathode. Thus, this work offers a promising exploration for high energy DIBs.

Static and Dynamic Response Characteristics of a Full-Scale Long-Cantilever Tower under Various Loading Conditions

Long-cantilever transmission towers are drawing more and more attention in ultrahigh-voltage (UHV) transmission projects. To meet the requirements of high-voltage safety clearance, the structural characteristics of long-cantilever transmission towers are significantly different from traditional ones. Aiming to ensure the safety of long-cantilever transmission towers during service, this paper investigates their static and dynamic characteristics under various extreme loading conditions based on full-scale tests and numerical simulation. With the strain data tested in seven typical cases, the bending moments and axial forces of the main members were back-calculated and the initial imperfections were calculated based on these results. Using a stochastic subspace identification algorithm, the evolution of the modal parameters during the full-scale test was revealed. The damage position of the main members was identified according to the mode shape changes, and the dynamic collapse process was analyzed via the measured dynamic responses and recorded videos. Numerical simulation was conducted in ANSYS using the calculated initial imperfections, and the results were in good agreement with the full-scale test. The results show that torsion action was not dominant for this tower and the failure mode was still the bending failure at the tower body. The proposed imperfection quantification method makes up for the deficiency of the empirical values, and using experimental results to guide numerical simulation proves practical. The modal parameters vary greatly under different loading conditions, which can be attributed to the damage after each loading case.

Comparative study on high-voltage safety performance of LiNixMnyCozO2 cathode with different nickel contents

In this article, systematic comparison of the safety performance of LiNixMnyCozO2 is made to find a balance among nickel content, energy density, and thermal stability. Three kinds of LiNixMnyCozO2 cathodes with different nickel contents are charged to different cut-off voltages from 4.2 to 4.6 V (vs Li+/Li) to obtain different energy densities, and their safety is evaluated through differential scanning calorimetry. Different characteristic temperatures are proposed to describe the cathode safety comprehensively and a relationship between energy density and thermal stability is established. It is found that cathode with lower nickel content (LiNi0.5Mn0.3Co0.2O2 and LiNi0.6 Mn0.2Co0.2O2) charging to high voltage exhibits better thermal stability compared to high nickel cathode (LiNi0.8Mn0.1Co0.1O2) at a conventional voltage. Numerical simulation based on a lumped thermal model is also performed to predict the real thermal behaviors of batteries using different cathodes. The discussion of the impact of the cut-off voltage for NMC cathodes provides a new dimension to further improve the comprehensiveness of battery material safety database and a new viewpoint on the trade-off between cathode energy density and safety.

Hierarchical Heterostructure Engineering of Layered Double Hydroxides on Nickel Sulfides Heteronanowire Arrays as Efficient Cathode for Alkaline Aqueous Zinc Batteries.

Aqueous alkaline rechargeable nickel-zinc (Ni-Zn) batteries possess great potential for large-scale energy storage systems because of their high output voltage, cheap cost, and intrinsic safety. However, the practical applicability of Ni-Zn batteries has been limited by traditional Ni-based cathodes with low capacity and poor cycle stability. Rational design of electrode structure and composition is highly desired but still significantly challenging. Herein, uniform self-supported hierarchical heterostructure composites interacting NiCo-layered double hydroxide with 1D nickel sulfides heteronanowire rooted on Ni foam (NF\Ni3 S2 /NiS@NiCo-LDH) are successfully developed by a hydrothermal sulfurization-electrodeposition process. The self-supported 3D hierarchical heterostructured composites nanoarray provides abundant reactive sites, rapid ion diffusion channels, and fast electron transfer routes, as well as strong structural stability. More significantly, the strong interfacial charge transfer between Ni3 S2 /NiS heteronanowire and NiCo-LDH effectively modifies the electronic structure of the composites and thereby improving the reaction kinetics. Consequently, the NF\Ni3 S2 /NiS@NiCo-LDH electrode presents a superior capacity of 434.5 mAh g-1 (1.73 mAh cm-2 ) at 3mA cm-2 . In addition, the fabricated NF\Ni3 S2 /NiS@NiCo-LDH//Zn battery can offer a maximal energy density and power density as large as 556.3Wh kg-1 and 26.3kW kg-1 , respectively, as well as an exceptional cycling performance.

Review of electrolyte strategies for competitive dual-ion batteries

The development of potential substitutes for lithium-ion batteries has attracted considerable attention in recent years due to the scarcity of lithium sources and the urgent demand for energy storage systems. Remarkably, dual-ion batteries (DIBs) based on a particular intercalation mechanism of anions exhibit great promise as next-generation batteries with high operating voltage, low cost, and high safety. However, research on DIBs is still in its infancy, and many fundamental issues, such as limited energy density, structural failure, sluggish kinetics, and electrolyte deposition, must be understood more comprehensively to explore high-performance electrolytes and electrodes and establish stable redox electrochemistry. In this review, we summarize the current mechanisms and challenges of DIBs to address and alleviate these issues. Among various critical components of DIBs, electrolytes are receiving considerable attention because they provide the basic operating environment and participate in the energy storage process. Several electrolyte strategies, including high-concentration, hybrid ion, functional additive, and solid-state strategies, have been proposed. These strategies have been demonstrated to not only improve the properties of electrolytes but also deliver superior battery performance. Therefore, a comprehensive overview of electrolyte strategies is presented and discussed in detail for the future development of DIBs.

A Fault Diagnosis Method for Lithium-Ion Battery Packs Using Improved RBF Neural Network

With the increasing demand for electric vehicles, the high voltage safety of electric vehicles has attracted significant attention. More than 30% of electric vehicle accidents are caused by the battery system; hence, it is vital to investigate the fault diagnosis method of lithium-ion battery packs. The fault types of lithium-ion battery packs for electric vehicles are complex, and the treatment is cumbersome. This paper presents a fault diagnosis method for the electric vehicle power battery using the improved radial basis function (RBF) neural network. First, the fault information of lithium-ion battery packs was collected using battery test equipment, and the fault levels were then determined. Subsequently, the improved RBF neural networks were employed to identify the fault of the lithium-ion battery pack system using the experimental data. The diagnosis test results showed that the improved RBF neural networks could effectively identify the fault diagnosis information of the lithium-ion battery packs, and the diagnosis accuracy was about 100%.

A gas monitoring chamber for high pressure applications

Time Projection Chambers (TPCs) operated at high pressure have become a topic of interest for future long baseline neutrino experiments. Pressurized gas retains the low momentum threshold for particle detection of atmospheric TPCs, but offers a larger target mass for neutrino interactions at the same volume. Operation at high pressure poses several new challenges in safety aspects regarding overpressure and high voltage safety. The presented High Pressure Gas Monitoring Chamber (HPGMC) can be used to study the suitability of various drift gas mixtures up to 10 bar and a maximum field of ∼ 3000 V/cm. A flexible construction makes it possible to exchange parts of the inner detector and to test new technologies. In this work, the construction of a HPGMC and its commissioning using the P10 gas mixture (90 % Ar + 10 % CH4) are presented.

Design and Implementation of Portable Auto Defibrillator

Sudden Cardiac Arrest (SCA) is a case that made the heart stop pumping the blood. Ventricular fibrillation (VF) and ventricular tachycardia (VT) are the major causes that lead to cardiac arrest. To treat SCA, a defibrillator device is used to return the heart to its normal sinus rhythm. The main generation of the defibrillator is the manual type which has many limitations involved., It requires the physician’s instruction to determine the patient state and the amount of joule required; therefore, it is preferable to design an auto defibrillator. The aim of this paper is to design a hardware implementation system of auto dc-shock utilized in the emergency case for diagnosing patient case and recovering the normal state of the heart. This prototype consists of five main parts, including the diagnosing system, high voltage section, charging unit, discharging unit, and safety unit. The output of diagnosing system is followed by charging and discharging period in order to get a suitable amount of joule according to patient situation of 50, 100, 120, and 150 joule discharged on the patient body by using a biphasic system provided by safety mode circuit so that the discharge process automatically happens in the case of not discharged on the patient body. The proposed diagnosing system in hardware design was tested on several patients in Ibn al-Nafis hospital and healthy patients at home and the accuracy was achieved of 97.03%, specificity is 97.8%, and the detection error rate is 3.09%.

Dynamic Loading Effect on Fault Current and Arc Flash for a Coordinated Substation

Due to load growth and various load types within the service territory, utilities need to enhance the utilization of substations. In any case, towards the coordinated substation design, the utilization of the transformers' most total capacity cannot be reduced just because there is a lack of proper coordination between transmission and distribution systems. The transmission and distribution systems' stability and safe operability must be investigated in a coordinated substation. The critical issues are the asymmetric fault currents on the high voltage and arc-related safety issues on the distribution switchgear at different dynamic loading scenarios. We found that when one 138 kV transmission line and two transformers are energized, with increased dynamic loading, from 40% and above, the substation, as a whole, gets gradually more stressed. Because of the highest amount of fault currents on the 138 kV bus, to avoid CT saturation, we need to consider that three transmission lines are connected, and all three transformers are running at 100% dynamic loading. At this value of dynamic loading, in the 13.2 kV switchgear, the incident energy is 2 cal/cm2, and the arc flash boundary is four feet, which ensures that all workers need to wear the proper arc-rated clothes to work on any de-energized cubicle of the switchgear.

Epidemiological investigation of 169 inpatients with high-voltage electrical burns on the wrist

Objective: To analyze the epidemiological characteristics of inpatients with high-voltage electrical burns on the wrist in Beijing Jishuitan Hospital (hereinafter referred to as the author's unit), so as to provide reference for the prevention and treatment of high-voltage electrical burns on the wrist. Methods: The medical records of inpatients suffered from high-voltage electrical burns on the wrist in the author's unit from January 2008 to December 2019 were collected. The patients' gender, age, population category, injury situation, injury season, total burn area, electrical burn type on the wrist of the affected limbs, the time from injury to first flap/myocutaneous flap transplantation, vascular reconstruction and flap/myocutaneous flap transplantation of the affected limbs, the total amputation rate of the affected limbs and the amputation rate of the affected limbs with type Ⅲelectrical burns on the wrist, the number of operation, postoperative infection rate of flap/myocutaneous flap, length of hospital stay, hospitalization expense, and treatment outcome were retrospectively analyzed. Comparison of the aforementioned statistical items between patients admitted from January 2008 to December 2013 (hereinafter referred to as the pre-stage) and January 2014 to December 2019 (hereinafter referred to as the post-stage) except gender, the total amputation rate of the affected limbs, treatment outcome were performed. Data were statistically analyzed with chi-square test, Fisher's exact probability test, and Wilcoxon rank-sum test. Results: During the 12 years, a total of 169 patients with high-voltage electrical burns on the wrist were admitted to the author's unit, including 162 males and 7 females, aged (35±13) years, and 75.15% (127/169) of patients were 21-50 years old. The top three groups in population category from high to low were workers, migrant workers, and primary and secondary school students, accounting for 48.52% (82/169), 28.99% (49/169), and 9.47% (16/169), respectively. At work of non-electric power accounted for 47.93% (81/169) and ranked the first in the proportion of injury situation. The injury occurred mostly in summer and autumn, accounting for 39.05% (66/169) and 28.99% (49/169), respectively. About 65.09% (110/169) of the patients were with total burn area less than 10% total body surface area. There were totally 216 affected limbs with high-voltage electrical burns on the wrist, of which the numbers of wrist with type Ⅲ and type Ⅳ injury were 25 (11.57%) and 21 (9.72%), respectively. The time from injury to first flap/myocutaneous flap transplantation was 6.00 (3.75, 8.00) d. There were 45 affected limbs operated with vascular reconstruction, 75 affected limbs transplanted with pedicled axial flap, and 86 affected limbs transplanted with free flap/myocutaneous flap. The total amputation rate of affected limbs was 12.96% (28/216), and the amputation rate of the affected limbs with type Ⅲ electrical burns on the wrist was 28% (7/25). The number of operation was 4 (3, 5) times, the postoperative infection rate of flap/myocutaneous flap was 7.18% (13/181), the hospitalization time was 39.00 (25.00, 50.00) d, and the hospitalization cost was 123 553.00 (50 656.50, 216 003.00) yuan. Compared with those of the pre-stage, the time from injury to first flap/myocutaneous flap transplantation was significantly shortened (Z=-4.038, P<0.01), the ratio of free flap/myocutaneous flap transplantation on affected limbs was significantly increased (χ(2)=13.478, P<0.01), the ratio of pedicled axial flap transplantation on affected limbs was significantly decreased (χ(2)=10.242, P<0.01), the number of operation was significantly reduced (Z=-5.903, P<0.01), the postoperative infection rate of flap/myocutaneous flap was significantly decreased (χ(2)=4.492, P<0.05), the length of hospital stay was significantly shortened (Z=-2.723, P<0.01), and the hospitalization expense was significantly decreased among patients hospitalized in the post-stage (Z=-2.121, P<0.05). The other items were close between patients hospitalized in the pre-stage and those in the post-stage. Conclusions: Men were more likely than women to suffer from high-voltage electrical burns on the wrist in the author's unit. Young workers and migrant workers may be the key groups for the prevention of high-voltage electrical burns on the wrist. It is very important to strengthen the management of high voltage safety education for non-electric power staff, warn and protect the surrounding area of high voltage environment, and prohibit non staff for entering the high voltage environment, especially in summer and autumn. In the last 6 years, the patients with high-voltage electrical burns on the wrist may benefit from the active vascular reconstruction at early stage and free flap/myocutaneous flap repair in the author's unit.

Fault and safety protection of ship power station

With the continuous development of the shipbuilding industry, there are more and more ship types, and the tonnage of ships is getting bigger and bigger. Traditional low-voltage ship power systems are no longer sufficient for navigation, and 6600 V high-voltage power supply systems are increasingly being used on large ships. High-voltage equipment is different from traditional low-voltage equipment, and incorrect operation can easily lead to safety accidents. In the process of building a ship, the shipyard has a complex environment. How to do safe operation and protection is especially important. This paper focuses on the safe operation characteristics of equipment, analyzes common faults, analyzes the requirements of on-site personnel for high-voltage safety protection, and ensures that the mooring test is carried out smoothly, and the test personnel and high-voltage power equipment are not damaged.

A Flexible Aqueous Asymmetric Lithium‐Ion Supercapacitor with High Voltage and Superior Safety

Achieving high voltage and safety simultaneously in energy storage devices can greatly advance the development of flexible and wearable electronics. Thus, flexible aqueous asymmetric lithium‐ion supercapacitors with a high voltage attract the interest of many researchers. Herein, a new flexible aqueous asymmetric lithium‐ion supercapacitor with a high voltage and superior safety is fabricated using manganese oxide and iron hydroxide, which are electrodeposited on carbon cloths as electrodes and a super‐concentrated gel polymer as the electrolyte. Impressively, the flexible asymmetric lithium‐ion supercapacitor delivers a high voltage of 3.2 V, which is a high value in aqueous asymmetric supercapacitors. Moreover, the asymmetric supercapacitor exhibits a specific capacitance of 227.6 F g−1, a maximum energy density of 49.3 Wh kg−1, and a maximum power density of 11.5 kW kg−1, together with a capacitance retention of 82% after 1000 cycles at a current density of 2 A g−1. Importantly, the supercapacitor can keep good electrochemical performance under extremely harsh conditions, such as compressing, hammering, punching, and tailoring, which demonstrates superior safety.

Electrochemically Activated Nickel-Carbon Composite as Ultrastable Cathodes for Rechargeable Nickel-Zinc Batteries.

Aqueous rechargeable nickel-zinc batteries are highly attractive for large-scale energy storage for their high output voltage, low cost, and excellent safety; however, their inferior cycling durability due to the degradation of the Ni-based cathode is a major obstacle for their applications. In this context, we develop a new kind of porous electrochemically activated Ni nanoparticle/nitrogen-doped carbon (Ni/NC) composite material as ultrastable cathodes for advanced aqueous rechargeable nickel-zinc batteries. The in situ formation of a highly active NiO x(OH) y layer on Ni nanoparticles and a unique hydrophilic porous architecture endow the activated Ni/NC composite with high accessible area, abundant active sites, easy electrolyte permeation, and shortened charge/ion transport pathway. Consequently, a high capacity of 381.2 μAh cm-3 with an outstanding rate capability is achieved by the Ni-Zn battery using the optimized activated Ni/NC composite as the cathode (about 30-fold enhancement compared to that with the pristine Ni/NC composite as the cathode). More impressively, the as-assembled Ni-Zn battery achieves an unprecedented cyclic stability with no capacity loss after 36 000 charge/discharge cycles. This is the highest cyclic durability ever for Ni-Zn batteries and other aqueous rechargeable batteries. This novel efficient electrochemical activation strategy to achieve a high-performance cathode and demonstration of an ultrastable aqueous rechargeable Ni-Zn battery may open up new vistas on the development of more advanced and reliable energy storage materials and devices.

LiFePO4-Coated LiNi0.5Co0.2Mn0.3O2 Cathode Materials with Improved High Voltage Electrochemical Performance and Enhanced Safety for Lithium Ion Pouch Cells

The applicable nickel-rich cathode materials (LiNi0.5Co0.2Mn0.3O2, NCM) under high cutoff voltage for high energy density lithium ion batteries shows a broad prospect, but creates enormous challenges for safety. In this work, the LiFePO4-coated LiNi0.5Co0.2Mn0.3O2 (NCM-LFP) composites were prepared on a large scale by the high-speed dispersion and mechanical fusion method, attempting to improve the electrochemical performance and safety of pouch full cells worked under a high cutoff voltage of 4.5 V. Performances have been greatly enhanced, especially for the heat generation during the charge process: the temperature rise of a 5Ah NCM-LFP/MCMB (mesocarbon microbeads) pouch cell was 18.7°C, much lower than that of a NCM/MCMB pouch cell (42.7°C). Also, no thermal runaway was observed of NCM-LFP/MCMB pouch cells at 100% state of charge (SOC) during the extrusion and metallic nail penetration tests. The results of ex-situ impedance measurement, high magnification transmission electron microscope (HR-TEM) and in-situ X-Ray Diffraction (XRD) during heating revealed that the enhanced high voltage safety was contributed to the suppressed structure evolution from layer to spinel to rock salt, as a result of a dense and uniform LFP protective layer on NCM.