Sc3+ substituted Na3V2(PO4)3 on N-doped porous carbon skeleton boosting high structural stability and superior electrochemical performance for full sodium ion batteries.

The poor structural stability and conductivity of Na3V2(PO4)3 (NVP) have been serious limitations to its development. In this paper, Sc3+ is selected to replace partial site of V3+ which can enhance its ability to bond with oxygen, forming the ScO6 octahedral unit, resulting in improved structural stability and better kinetic properties for the NVP system. Moreover, due to the larger ionic radius of Sc3+ compared to V3+, moderate Sc3+ substitution can support the crystal framework as pillar ions and expand the migration channels for de-intercalation of Na+, thus efficiently promoting ionic conductivity. The introduction of polyacrylonitrile (PAN) to provide an N-doped porous carbon substrate is another key aspect. The low-cost carbon resource of PAN can induce a beneficial nitrogen-doped carbon skeleton with defects, enhancing electronic conductivity at the interface to reduce the polarization phenomenon. The established pore structure can serve as a buffer for unit cell deformation caused by Na+ migration. Furthermore, the enlarged specific surface area provides more active sites for electrolyte infiltration, improving the material utilization rate. The after cycling X-ray Diffraction/scanning electron microscope (XRD/SEM) further confirms the stabilized porous carbon skeleton and improved crystal stability of Sc-3 material. Ex-situ XRD analysis shows that the crystal volume change in the Sc-3 cathode is relatively slight but reversible during the charge/discharge process, indicating that Sc3+ doping plays a crucial role in stabilizing the unit cell structure. The hybrid Sc/VO6 and PO4 units jointly build a strong bone structure to resist stress and weaken deformation. Accordingly, the optimized Sc-3 sample reveals an initial capacity of 115.9 mAh/g at 0.1C, with a capacity retention of 78.6 % after 2000 cycles at 30C. The Sc-3//CHC full battery can release a capacity of 191.3 mAh/g at 0.05C, accompanied by successful illumination, showcasing its promising practical applications.

Facile Al2O3 coating suppress dissolution of Mn2+ in Mn-substituted Na3V2(PO4)3 with outstanding electrochemical performance for full sodium ion batteries.

Na3V2(PO4)3 (NVP) encounters significant obstacles, including limited intrinsic electronic and ionic conductivities, which hinder its potential for commercial feasibility. Currently, the substitution of V3+ with Mn2+ is proposed to introduce favorable carriers, enhancing the electronic conductivity of the NVP system while providing structural support and stabilizing the NASICON framework. This substitution also widens the Na+ migration pathways, accelerating ion transport. Furthermore, to bolster stability, Al2O3 coating is applied to suppress the dissolution of transition metal Mn in the electrolyte. Notably, the Al2O3 coating serves a triple role in reducing HClO4 concentration in the electrolyte, inhibiting Mn dissolution, and functioning as the ion-conducting phase. Likewise, carbon nanotubes (CNTs) effectively hinder the agglomeration of active particles during high-temperature sintering, thereby optimizing the conductivity of NVP system. In addition, the excellent structural stability is investigated by in situ XRD measurement, effectively improving the volume collapse during Na+ de-embedding. Moreover, the Na3V5.92/3Mn0.04(PO4)3/C@CNTs@1wt.%Al2O3 (NVMP@CNTs@1wt.%Al2O3) possesses unique porous structure, promoting rapid Na+ transport and increasing the interface area between the electrolyte and the cathode material. Comprehensively, the NVMP@CNTs@1wt.%Al2O3 sample demonstrates a remarkable reversible specific capacity of 122.6 mAh/g at 0.1 C. Moreover, it maintains a capacity of 115.9 mAh/g at 1 C with a capacity retention of 90.2 mAh/g after 1000 cycles. Even at 30 C, it achieves a capacity of 87.9 mAh/g, with a capacity retention rate of 84.87 % after 6000 cycles. Moreover, the NVMP@CNTs@1wt.%Al2O3//CHC full cell can deliver a high reversible capacity of 205.5 mAh/g at 0.1 C, further indicating the superior application potential in commercial utilization.

Simultaneous Mn and Cl doping on Na3V2(PO4)3 with high performance for full sodium-ion batteries.

Nowadays, the poor conductivity and unstable structure have become obstacles for the popularization of Na3V2(PO4)3 (NVP). In the current work, a dual-modified Mn0.1Cl0.3-NVP composite doped with Mn and Cl is prepared by a facile sol-gel method. When Mn2+ with a large ionic radius replaces small V3+, it can improve the stability of the NVP crystal structure. In addition, the replacement of V3+ by Mn2+ in a low valence state can generate redundant hole carriers, which is conducive to the rapid transport of electrons. The substitution of PO43- by Cl-, which is more electronegative, can reduce the impedance and facilitate the movement of Na+. Owing to the synergistic effect of Mn and Cl co-substitution, the structural stability of NVP was systematically enhanced, and the electron transfer and ion diffusion were effectively improved. Consequently, the optimized Mn0.1Cl0.3-NVP sample demonstrated superior electrochemical performance and kinetic properties. It exhibited a high reversible capacity of 109.2 mA h g-1 at 0.1C. Even at 15 and 30C, high discharge capacities of 70.3 mA h g-1 and 68.2 mA h g-1 were observed after 2000 cycles with capacity retention above 80%. Moreover, it delivered remarkable capacities of 77.1 and 73.4 mA h g-1 at 100 and 200C with retained capacity values of 50.3 and 47 mA h g-1, respectively, after 2000 cycles. Furthermore, the assembled Mn0.1Cl0.3-NVP//HC full cell delivered a high value of 94.7 mA h g-1 and lit LED bulbs, indicating its excellent application potential.

Se-induced defective carbon nanotubes promoting superior kinetics and electrochemical performance in Na3V2(PO4)3 for half and full Na ion cells.

Na3V2(PO4)3 (NVP), with unique Na super ionic conductivity (NASICON) framework, has become an prospective cathode material. However, the low electronic conductivity and poor structural stability limit its further development. Currently, the optimized carbon nanotubes (CNTs) by selenium doping are utilized to modify NVP system for the first time. Notably, the introduction of selenium in CNTs promotes to generate more defects, resulting in abundant active sites for the de-intercalation of Na+ to achieve more pseudocapacitance. Moreover, the newly formative C-Se bonds possess much stronger bond energy than the original CC (586.6 KJ mol-1 vs 377.4 KJ mol-1) bonds. The structure arrangement of the original CNTs is significantly improved by the doped selenium element, indicating that an enhanced carbon skeleton could be obtained to sustain the structural stability of NVP system. Furthermore, the excess selenium can be doped into the bulk of NVP crystal to replace of partial oxygen. Due to the larger ionic of Se2- (1.98 Å vs 1.4 Å of O2-), the VSe6 group has larger framework, which provides a broadened pathway for Na+ migration to improve the kinetic characteristics. Accordingly, the modified NVP@CNTs:Se = 1:1 sample exhibits superior rate capability and cyclic performance. It reveals high capacities of 78.6 and 76.5 mAh/g at 20 and 60C, maintaining 65.4 and 53.8 mAh/g after 5000 and 7000 cycles with high capacity retention of 84.49 % and 70.32 %, respectively. The assembled NVP@CNTs:Se = 1:1//CHC full cell delivers a high value of 153.6 mAh/g, suggesting the optimized sample also behaves excellent application potentials.

Enhanced performance of Sn-doped Na3V2(PO4)3 with CNT integration for high-efficiency sodium-ion batteries.

The development of Na3V2(PO4)3 (NVP) has been severely hindered by low conductivity and unstable crystal structure. A simultaneously optimized strategy of Na-rich and Sn substitution is proposed for the first time. SnX-NVP@CNTs with different doping gradients are successfully prepared by the facile sol-gel method. Notably, more hole carriers can be generated by introducing Sn2+, thus improving its electron transport efficiency. In addition, since Sn2+ ions have a larger ion radius; when replacing V3+ ions at pillar positions, the lattice spacing can be enlarged to improve the structural stability of electrode materials. Meanwhile, it is beneficial to the movement of deep-level Na+ ions and improves the utilization rate of electrode materials. Moreover, to achieve charge compensation, it is necessary to introduce excess Na+ to the Sn-doped NVP system, which will increase the number of Na+ involved in the deintercalation process and improve its reversible capacity. Furthermore, the dense coating of CNTs can form an efficient conductive network structure, which improves the electron transport rate and inhibits the accumulation of active grains to accelerate Na+ diffusion. Under the synergistic adjustment of Sn2+ doping and CNTs enwrapping, the prepared Sn0.07-NVP@CNTs exhibit a high reversible capacity of 115.1 mAh/g at 0.1C, and the capacity retention rate reaches 89.35 % after 2000 cycles at 10C. Even after 10,000 cycles at 60C, its reversible capacity dropped from the initial 75.9 to 51.3 mAh/g, with a capacity loss of only 0.003 % per cycle. Besides, the Sn0.07-NVP@CNTs//CHC full battery releases a capacity of 139.9 mAh/g, highlighting its great potential for actual applications.

Constructing p-type substitution induced by Ca2+ in defective Na3V2-xCax(PO4)3/C wrapped with conductive CNTs for high-performance sodium-ion batteries.

Na3V2(PO4)3 (NVP), with a high tap density, is considered a prospective cathode material due to its low cost, ideal specific capacity and cycling stability. However, its low ionic/electronic conductivity has become the main factor hindering its development. In the current work, a dual modification strategy has been proposed to optimize NVP, which is successfully achieved via a facile sol-gel method. The addition of partial Ca2+ with low valence at the V3+ site produces favorable p-type substitution in the pristine NVP bulk, generating beneficial hole carriers in the electronic structure to accelerate the migration rate of Na+. Moreover, the doped Ca2+ with a larger ionic radius (1.03 Å vs. 0.64 Å of V3+) can have a pillar effect to support the cell structure, improving the structural stability of NVP. Meanwhile, the larger radius of Ca2+ contributes to the expansion of the lattice spacing, significantly facilitating the diffusion efficiency of Na+ to optimize the diffusion kinetics. Besides, the evenly coated carbon layers derived from the excess carbon resources combine with the enwrapped carbon nanotubes to construct a highly conductive network to enhance the transportation of electrons. Notably, the modified Ca0.04-NVP@CNTs electrode exhibits a high capacity of 117.4 mA h g-1 at 0.1 C, while that of NVP is only 69.4 mA h g-1. Moreover, it delivers an initial capacity of 110.1 mA h g-1 at 1 C and the mass loss rate per lap is only 0.01%. At 5 C, the initial capacity of Ca0.04-NVP@CNTs is 104.3 mA h g-1 while that of NVP is only 75.9 mA h g-1. Interestingly, it exhibits excellent cycling stability at 50 C; the initial capacity is 75.7 mA h g-1 and the capacity retention is around 99% after 4000 cycles.

Simultaneous defect regulation by p-n type co-substitution in a Na3V2(PO4)3/C cathode for high performance sodium ion batteries.

The Na3V2(PO4)3 (NVP) cathode is deemed to be a promising candidate for sodium ion batteries due to its strong structural stability and high theoretical capacity. Nevertheless, its poor intrinsic conductivity restricts further development. To overcome these shortcomings, a dual modification strategy of Mn2+/Ti4+ co-substitution is proposed for the first time. Significantly, Mn doping can efficiently accelerate the transmission speed of electrons by introducing beneficial holes derived from the low valence state of +2, presenting the classical p-type doping modification. Moreover, the presence of Mn2+ with a larger ionic radius can support the crystal to stabilize the Na superionic conductor (NASICON) framework of the NVP system. Ti4+ is introduced for perfect charge compensation. Accordingly, the addition of Ti4+ can generate excess electrons due to the n-type substitution, which contributes to the favorable electronic conductivity. In addition, conductive carbon nanotubes (CNTs) are utilized to construct an efficient network to improve the rate capability of the NVP composite. Meanwhile, CNTs can inhibit particle growth and thus reduce particle size, shortening the transport path of Na+ and promoting the diffusion of Na+. Comprehensively, the optimized Na3V2-xMnxTix(PO4)3/C@CNTs (x = 0.15) deliver high capacities of 70.3 and 68.2 mA h g-1 at 90C and 180C, maintaining 58 and 53.8 mA h g-1 after 1000 cycles with high capacity retention of 82.5% and 78.9%.

Constructing hierarchical heterojunction structure for K/Co co-substituted Na3V2(PO4)3 by integrating carbon quantum dots.

Na3V2(PO4)3 (NVP) has been widely adopted as cathode in sodium ion battery devices. Nevertheless, the weak intrinsic conductivity and serious structural collapse limit the further development. Herein, a simultaneous modified strategy of doping K/Co and integrating carbon quantum dots (CQD) is proposed. Substituting K+ is beneficial to afford amount of Na+ transport within the stabled and expanded lattice. The introduction of Co2+ generates beneficial hole carriers to improve conductivity. Furthermore, the bonding of conductive CQD guides to obtain nano-sized NVP grains, reducing the pathway for ionic migration to accelerate the diffusion capability. Importantly, a unique p-n type heterojunction construction is established in the interface between CQD (n-type) and NVP (p-type). This heterojunction structure enhances the mobility of electrons owing to the free pathways, in which the electrons transport in a relatively lower energy level without the scatter and collision of anions dopants. Ultimately, K0.1Na2.95V1.95Co0.05(PO4)3@CQD exhibits with the best energy output level. It's initial capacity under 5C is 109.8 mA h g-1 and the retention is 87.6% after cycle 400 cycles. Even at 20 and 50C, its output is 93.5 and 82.6 mA h g-1 for 1st and 66.6 and 52.1 mA h g-1 for 1000th cycle, respectively. Finally, an asymmetric full cell test confirms its application practically.

Activating the Extra Redox Couple of Co2+/Co3+ for a Synergistic K/Co Co-Substituted and Carbon Nanotube-Enwrapped Na3V2(PO4)3 Cathode with a Superior Sodium Storage Property.

Na3V2(PO4)3 (NVP) materials have emerged as a promising cathode for sodium ion batteries (SIBs). Herein, NVP is successfully optimized by dual-doping K/Co and enwrapping carbon nanotubes (CNTs) through a sol-gel method. Naturally, the occupation of K and Co in the Na1 sites and V sites can efficiently stabilize the crystal cell and provide the expanded Na+ transport channels. The existence of tubular CNTs could restrict the crystal grain growth and effectively downsize the particle size and provide a shorter pathway for the migration of electrons and ions. Moreover, the amorphous carbon layers combined with the conductive CNTs form a favorable network for the accelerated electronic transportation. Furthermore, the ex situ XPS characterization reveals that an extra redox reaction pair of Co2+/Co3+ is successfully activated at the high voltage range, resulting in superior capacity and energy density property for KC0.05/CNTs composites. Comprehensively, the optimized KC0.05/CNTs electrode exhibits a distinctive electrochemical property. It delivers an initial reversible capacity of 119.4 mA h g-1 at 0.1 C, surpassing the theoretic value for the NVP system (117.6 mA h g-1). Moreover, the KC0.05/CNT electrode exhibits the initial capacity of 113.2 mA h g-1 at 5 C and 105.8 mA h g-1 at 10 C, and the maintained capacities at 500 cycles are 105.8 and 100.8 mA h g-1 with outstanding retention values of 96.6 and 95.3%. Notably, it releases capacities of 99.8 and 84.5 mA h g-1 at 50 and 100 C, and the capacity retention values at 2500 cycles are 66.2 and 58.8 mA h g-1, respectively. What is more, the KC0.05/CNTs//Bi2Se3 asymmetric full cell exhibits a high capacity of 191.4 mA h g-1 at 2.65 V, with the energy density being as high as 507 W h kg-1, demonstrating the eminent practical application potential of KC0.05/CNTs in SIBs.

Phase Change Materials Application in Battery Thermal Management System: A Review.

The purpose of a battery thermal management system (BTMS) is to maintain the battery safety and efficient use as well as ensure the battery temperature is within the safe operating range. The traditional air-cooling-based BTMS not only needs extra power, but it could also not meet the demand of new lithium-ion battery (LIB) packs with high energy density, while liquid cooling BTMS requires complex devices to ensure the effect. Therefore, phase change materials (PCMs)-based BTMS is becoming the trend. By using PCMs to absorb heat, the temperature of a battery pack could be kept within the normal operating range for a long time without using any external power. PCMs could greatly improve the heat dissipation efficiency of BTMS by combining with fillers such as expanded graphite (EG) and metal foam for their high thermal conductivity or coordinating with fins. In addition, PCMs could also be applied in construction materials, solar thermal recovery, textiles and other fields. Herein, a comprehensive review of the PCMs applied in thermal storage devices, especially in BTMS, is provided. In this work, the literature concerning current issues have been reviewed and summarized, while the key challenges of PCM application have been pointed out. This review may bring new insights to the PCM application.

Experimental study of polyethylene pyrolysis and combustion over HZSM-5, HUSY, and MCM-41.

The effects of temperatures, catalysts, and catalyst contents on polyethylene (PE) pyrolysis were investigated by using single-photon ionization time-of-flight mass spectrometry (SPI-TOFMS). The mass spectra of pyrolyzed PE and PE/catalysts from 300°C to 800°C illustrate that the pyrolysis reactions were apparently promoted and varied by introducing HZSM-5, HUSY, and MCM-41. As microporous catalysts, HZSM-5 and HUSY were found to accelerate the BTX formation at 400°C, which could not be observed for pure PE until 800°C. With the existence of MCM-41, only alkenes were produced below 600°C. The pyrolysis processes could to be accelerated by adding catalysts. Principal components analysis (PCA) was finally employed to identify the main factors with influence on the products distribution. Analytical results showed that the yield of the majority of products could be affected by different experimental conditions, that the type of catalysts makes the most significant influence. The impact of different types of catalysts on fire hazard of PE was studied by using the cone calorimeter. The results indicated that the time to ignition (TTI) and the peak heat release rate (pHRR) were changed remarkably. It is worth noting that with the addition of MCM-41, the pHRR is the minimum.

[Critical care and therapy based different illness state of 80 patients with severe hand-foot-and-mouth disease seen in Shenzhen].

OBJECTIVE: To discuss the treatment strategy of severe hand-foot-and-mouth disease (HFMD) cases, prevent the severe cases from progressing to fatal condition and enhance the survival rate of critically ill patients. METHODS: Eighty HFMD cases were divided into four groups, A, B, C and D, according to the severity of patients' nervous system manifestation and other system involved. Different intensive care and treatments were used and the effect and outcome were analyzed for each group. All statistical analyses were performed by using SPSS software 13.0. One-way ANOVA and Chi-square test were used for data analysis. RESULTS: The most common symptoms were continuous fever (69/70) and myoclonic jerk (67/70). The fewer the rashes were, the more severe the patient's condition was, heart rate >200/min, hypertension, increase of white blood cells in peripheral blood and hyperglycemia were common in patients with lesions in brain stem and pulmonary edema. There were no relations between patient's conditions and CSF white blood cells and CRP. CNS involvement was highly associated with EV71 infection. There were 69 cases in group A, B and C in total and all recovered. Of 11 patients in group D, 6 got complicated neurogenic pulmonary edema and circulatory failure, 2 cases died and 9 cases survived, 8 cases recovered without sequelae while one case had sequelae of mental retardation and dyscinesia. CONCLUSION: Administration of mannitol, methylprednisolone, IVIG and other supportive treatments in time and reasonably might have advantages in avoiding aggravation of the condition and enhancing the rate of successful rescue in patients with nervous system involvement.