In this paper, the dual-modified LiNi
0.8
Co
0.1
Mn
0.1
O
2
via Gd
2
O
3
is successfully obtained by the solid-state method. The phenomenon of Li/Ni cation mixing and structural stability of ...materials has been improved after Gd
2
O
3
modification. Additionally, the lower average discharge voltage drop (Δ
E
d
) and electrochemical polarization of the batteries are obtained after modification. Simultaneously, the dual-modified material via Gd
2
O
3
exhibits the high capacity retention of 94.50% compared with that (83.40%) of the Pristine (3.0–4.4 V, 1 C (180 mA g
−1
), 25 °C, after 100 cycles). The excellent electrochemical properties ascribe to the higher bond dissociation energies of Gd-O (716 kJ mol
−1
) and the stable coating layer of Gd
2
O
3
.
Ni-rich cathode material is taking more and more important position in energy storage and conversion because of their high capacity. But the gap between the demanded and actual capacity still hinder ...the development of electric vehicle industry. Herein, the Ni-rich (Ni content > 85%) cathode material has received extensive concern. In our research, LiNi
0.88
Co
0.09
Al
0.03
O
2
was prepared with solvothermal method by two steps. Meanwhile, the different solvents in solvothermal route are investigated. It is found that LiNi
0.88
Co
0.09
Al
0.03
O
2
prepared by isopropyl alcohol shows an excellent capacity retention which is up to 82.3% after 100 cycles at 55 °C, much higher than that prepared by ethyl alcohol (64.0%). The enhanced performance could be ascribed to the specific morphology formed in solvothermal period by the proper solvent.
DC line fault is one of the key problems that must be solved in a flexible HVDC system. During quite a long time between the existing main protection and backup protection of the HVDC line, there is ...no line protection method to detect the fault, which may lead the protection at the AC side to act before the backup protection of the DC line. To solve the problem, a novel two-step distance protection for flexible HVDC lines is proposed in this manuscript. Firstly, based on the uniform distributed parameter model, the equivalent lumped parameter model of the HVDC transmission line at low frequency is analyzed. Secondly, according to the time domain differential equation and the least squares algorithm, novel distance protection based on the iterative calculation of fault distance is proposed, which can eliminate the influence of distributed capacitive current and improve the precision of calculation. To improve the rapidity and reliability of the distance protection, low pass filters with two different cut-off frequencies are used to process the electrical quantities. Finally, simulation results show that the proposed distance protection can respond to metallic poleto-ground faults and pole-to-pole faults rapidly and reliably.
Reduced graphene oxide (rGO) sheet decorated Na
3
V
2
(PO
4
)
3
(NVP) microspheres were successfully synthesized by spray-drying method. The NVP microspheres were embedded by rGO sheets, and the ...surface of the particles were coated by rGO sheets and amorphous carbon. Thus, the carbon conductive network consisted of rGO sheets and amorphous carbon generated in the cathode material. NVP microspheres decorated with different content of rGO (about 0, 4, 8, and 12 wt%) were investigated in this study. The electrochemical performance of NVP exhibited a significant enhancement after rGO introduction. The electrode containing about 8 wt% rGO (NVP/G8) showed the best rate and cycle performance. NVP/G8 electrode exhibited the discharge capacity of 64.0 mAh g
−1
at 70°C, and achieved high capacity retention of 95.5% after cycling at 10°C for 100 cycles. The polarization of the electrode was inhibited by the introduction of rGO sheets. Meanwhile, compared with the pristine NVP electrode, NVP/G8 electrode exhibited small resistance and high diffusion coefficient of sodium ions.
Epoxy-functionalized silane (KH560) modified Li
1.2
Ni
0.13
Co
0.13
Mn
0.54
O
2
materials are prepared by a facile chemical grafting method for the first time. X-ray diffraction confirms that the ...crystal structure of Li
1.2
Ni
0.13
Co
0.13
Mn
0.54
O
2
is not affected by the KH560 modification. Scanning electron microscopy and transmission electron microscopy results prove that KH560 is homogeneously grafted on the Li
1.2
Ni
0.13
Co
0.13
Mn
0.54
O
2
surface with a thickness of 3–5 nm. The electrochemical tests reveal that the 1.0 wt% KH560 modified Li
1.2
Ni
0.13
Co
0.13
Mn
0.54
O
2
cathodes retain 92.88% (1 C) and 98.24% (5 C) capacity retentions after 100 cycles, respectively, far higher than 83.09% (1 C) and 50.68% (5 C) of the pristine. The improved cycling performances are mainly attributed to the fact that the X-O-M bonds stabilize the surface oxygen and resist the parasitic reactions during cycling, which further can suppress the structure degradation and the impedance increase. This work provides a facile and effective modification method to optimize the interfacial structures of Li
1.2
Ni
0.13
Co
0.13
Mn
0.54
O
2
and/or other cathode materials.
SnS
2
nanosheets/reduced graphene oxide (rGO) composite was prepared by reflux condensation and hydrothermal methods. In this composite, SnS
2
nanosheets
in-situ
grew on the surface of rGO ...nanosheets. The SnS
2
/rGO composite as anode material was investigated both in lithium ion battery (LIB) and sodium ion battery (SIB) systems. The capacity of SnS
2
/rGO electrode in LIB achieved 514 mAh g
−1
at 1.2 A g
−1
after 300 cycles. Moreover, the SnS
2
/rGO electrode in SIB delivered a discharge capacity of 645 mAh g
−1
at 0.05 A g
−1
; after 100 cycles at 0.25 A g
−1
, the capacity retention still keep 81.2% relative to the capacity of the 6th cycle. Due to the introduction of rGO in the composite, the charge-transfer resistance became much smaller. Compared with SnS
2
/C electrode, SnS
2
/rGO electrode had higher discharge capacity and much better cycling performance.
In this study, silicon/carbon composite nanofibers (Si@CNFs) were prepared as electrode materials for lithium-ion batteries via a simple electrospinning method and then subjected to heat treatment. ...The morphology and structure of these materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results show that the structure provides good electrical conductivity and affords sufficient space to accommodate volume expansion during charging/discharging. Furtherly, electrochemical performance tests show that the optimized Si@CNFs have an initial reversible capacity of 1,820 mAh g
at a current density of 400 mA g
and capacity retention of 80.7% after 100 cycles at a current density of 800 mA g
. Interestingly, the optimized Si@CNFs have a superior capacity of 1,000 mAh g
(400 mA g
) than others, which is attributed to the carbon substrate nanofiber being able to accommodate the volume expansion of Si. The SEI resistance generated by the Si@CNFs samples is smaller than that of the Si nanoparticles, which confirms that SEI film generated from the Si@CNFs is much thinner than that from the Si nanoparticles. In addition, the connected carbon substrate nanofiber can form a fiber network to enhance the electronic conductivity.
In spent battery material, there are plenty of valuable metals, such as copper, nickel, cobalt, manganese. Recovery of valuable metals from spent battery material not only protects the environment ...but also improves the utilization of resources and decreases the cost of battery material. In this study, hydrochloric acid is used as lixivant with characteristics of faster leaching rate and being recycled easily. The optimal conditions are that hydrochloric acid concentration is 6 mol/L, reaction temperature is exactly 60 °C, liquid/solid ratio is 8:1, (H
2O
2)
mol/(MeS)
mol
=
2, and the leaching time is 2 h, the results show that the dissolution yields of Ni, Co and Mn can be 95 wt.% at least. The basic purification concept of the leaching solution includes that copper is removed through replacement by iron powder followed by iron precipitation in goethite method. The results show that Cu and Fe can be removed 99 wt.% at the least. At the same time, the loss of Ni, Co and Mn is not beyond 2 wt.%, 3 wt.％ and 2 wt.%, respectively. This method makes the preparation of pure Ni
x
Co
y
Mn
z
ternary system precursor economical. The process seems to be able to claim base metals from waste in a reliable and feasible way.
On the basis of the principle of breaker failure protection delay and the analysis of the main factors which affect the protection, a sub-station-area breaker failure and dead-zone protection ...technical scheme based on the current differential principle is proposed. In this scheme, an incomplete current differential protection is structured by the breakers current transformer (CT) of the non-fault area, which is adjacent to the fault area. When the criteria of the incomplete current differential protection are satisfied, the adjacent breakers will trip to realise the isolation of the fault. This scheme is not only affected by the CT tailing and CT saturation, but also greatly reduces the time delay of breaker failure protection and achieves the free protection setting. The implementation of the project adopts an expandable architecture designed with the master slave mode, which could be achieved by high reliability with a flexible configuration of engineering and not relying on external time signals. Moreover, this scheme has the advantages of versatility and easier to implement. Also, it is preferable due to practicability and extended significance to popularise.
PDF
