We prepare a totally nonflammable phosphate-based electrolyte composed of 5 mol L-1 (M) Li bis(fluorosulfonyl) imide (LiFSI) in a trimethyl phosphate (TMP) solvent. The concentrated 5 M LiFSI/TMP ...electrolyte shows good compatibility with graphite and no Al corrosion. More attractively, such a concentrated electrolyte can effectively suppress the growth of Li dendrites in Li metal batteries because of a stable LiF-rich SEI layer. Therefore, this highly concentrated electrolyte is promising for safe Li batteries.
The notorious lithium (Li) dendrites and the low Coulombic efficiency (CE) of Li anode are two major obstacles to the practical utilization of Li metal batteries (LMBs). Introducing a ...dendrite-suppressing additive into nonaqueous electrolytes is one of the facile and effective solutions to promote the commercialization of LMBs. Herein, Li difluorophosphate (LiPO2F2, LiDFP) is used as an electrolyte additive to inhibit Li dendrite growth by forming a vigorous and stable solid electrolyte interphase film on metallic Li anode. Moreover, the Li CE can be largely improved from 84.6% of the conventional LiPF6-based electrolyte to 95.2% by the addition of an optimal concentration of LiDFP at 0.15 M. The optimal LiDFP-containing electrolyte can allow the Li||Li symmetric cells to cycle stably for more than 500 and 200 h at 0.5 and 1.0 mA cm–2, respectively, much longer than the control electrolyte without LiDFP additive. Meanwhile, this LiDFP-containing electrolyte also plays an important role in enhancing the cycling stability of the Li||LiNi1/3Co1/3Mn1/3O2 cells with a moderately high mass loading of 9.7 mg cm–2. These results demonstrate that LiDFP has extensive application prospects as a dendrite-suppressing additive in advanced LMBs.
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• Pure Al2O3 inorganic separator for lithium-ion batteries is prepared by a double sintering process. • The inorganic separator soaking the electrolyte solution exhibits quite high ionic ...conductivities, and specially the conductivity reaches 0.78mScm−1 at −20°C. • The inorganic separator has the higher electrolyte retention at 50°C than the commercial polymer separator. • The LiFePO4/graphite cell using the inorganic separator shows higher discharge capacity and rate capability, and better low-temperature performance than that using the commercial polymer separator.
An Al2O3 inorganic separator is prepared by a double sintering process. The Al2O3 separator has a high porosity and good mechanical strength. After the liquid electrolyte is infiltrated, the separator exhibits quite high ionic conductivities, and even the conductivity reaches 0.78mScm−1 at −20°C. Furthermore, the inorganic separator has an advantage over the polymer separator in the electrolyte retention. The LiFePO4/graphite cell using the Al2O3 inorganic separator shows higher discharge capacity and rate capability, and better low-temperature performance than that using the commercial polymer separator, which indicates that the Al2O3 separator is very promising to be applied in the lithium-ion batteries.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Niobium doped lithium titanate with the composition of Li
4Ti
4.95Nb
0.05O
12 has been prepared by a sol–gel method. X-ray diffraction (XRD) and scanning electron microscope (SEM) are employed to ...characterize the structure and morphology of Li
4Ti
4.95Nb
0.05O
12. The Li
4Ti
4.95Nb
0.05O
12 electrode presents a higher specific capacity and better cycling performance than the Li
4Ti
5O
12 electrode prepared by the similar process. The Li
4Ti
4.95Nb
0.05O
12 exhibits an excellent rate capability with a reversible capacity of 135
mAh
g
−1 at 10
C, 127
mAh
g
−1 at 20
C and even 80
mAh
g
−1 at 40
C. Electrical resistance measurement and electrochemical impedance spectra (EIS) reveal that the Li
4Ti
4.95Nb
0.05O
12 exhibits a higher electronic conductivity and faster lithium-ion diffusivity than the Li
4Ti
5O
12, which indicates that niobium doped lithium titanate (Li
4Ti
4.95Nb
0.05O
12) is promising as a high rate anode for the lithium-ion batteries.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Graphene/nanosized silicon composites were prepared and used for lithium battery anodes. Two types of graphene samples were used and their composites with nanosized silicon were prepared in different ...ways. In the first method, graphene oxide (GO) and nanosized silicon particles were homogeneously mixed in aqueous solution and then the dry samples were annealed at 500
°C to give thermally reduced GO and nanosized silicon composites. In the second method, the graphene sample was prepared by fast heat treatment of expandable graphite at 1050
°C and the graphene/nanosized silicon composites were then prepared by mechanical blending. In both cases, homogeneous composites were formed and the presence of graphene in the composites has been proved to effectively enhance the cycling stability of silicon anode in the lithium-ion batteries. The significant enhancement on cycling stability could be ascribed to the high conductivity of the graphene materials and absorption of volume changes of silicon by graphene sheets during the lithiation/delithiation process. In particular, the composites using thermally expanded graphite exhibited not only more excellent cycling performance, but also higher specific capacity of 2753
mAh/g because the graphene sheets prepared by this method have fewer structural defects than thermally reduced GO.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Heteroatom-doped high-quality graphene is highly effective in encapsulating sulfur (S) and fabricating a high-performance electrode for lithium–sulfur (Li-S) batteries. Herein, simultaneously ...exfoliated boron-doped graphene sheets (B-EEGs) are prepared via electrochemical exfoliation of graphite in a 1.0 mol L–1 Li bis(oxalato)borate (LiBOB)/dimethyl methylphosphonate (DMMP) electrolyte. The obtained B-EEG possesses high quality with a large planar size of ∼11 μm, few structure defects of ID/IG = 0.26, and low oxygen content of 7.93%. After B-EEG is used to encapsulate S through an in situ deposition route, the S@B-EEG with an S content of 72.5% displays a high initial discharge capacity of 1476 mAh g–1 at 0.1 C. Compared to a conventional S@thermally reduced graphene oxide (S@T-RGO) composite, the S@B-EEG composite exhibits a high capability of 1018 mAh g–1 at 1 C and excellent capacity retention of 838 mAh g–1 after 130 cycles. On one hand, the excellent electrochemical performances of S@B-EEG are primarily attributed to the few defects and big planar size of B-EEG, which is helpful for increasing the conductivity of S and suppressing the shuttle of long-chain polysulfides. On the other hand, the doped boron atoms as active sites can efficiently trap polysulfides by chemical adsorption.
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A paper-based membrane coated by graphitic carbon nitride (g-C
3
N
4
) is prepared via a dip-coating method and used as a separator for sodium metal batteries with merits of low cost and ...environment-friendliness. Introduction of g-C
3
N
4
effectively improves the ionic conductivity and the structural stability of the separator. Compared with traditional polyethylene separators and Al
2
O
3
-coated separators, the g-C
3
N
4
-coated separators show better electrolyte wettability, thermal stability, and electrochemical stability. Therefore, Na||Na
3
V
2
(PO
4
)
3
battery using the g-C
3
N
4
-coated separator exhibits better cycling stability and higher rate capability. These results prove that the g-C
3
N
4
-coated paper-based separator is expected to become the next generation of low-cost and high-safety separator in sodium metal batteries.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Ultrathin Li4Ti5O12 (LTO) nanosheets with ordered microstructures were prepared via a polyether-assisted hydrothermal process. Pluronic P123, a polyether, can impede the growth of Li2TiO3 in the ...precursor and also act as a structure-directing agent to facilitate the (Li1.81H0.19)Ti2O5·2H2O precursor to form the LTO nanosheets with the ordered microstructure. Moreover, the addition of P123 can suppress the stacking of LTO nanosheets during calcining of the precursor, and the thickness of the nanosheets can be controlled to be about 4 nm. The microstructure of the as-prepared ultrathin and ordered nanosheets is helpful for Li+ or Na+ diffusion and charge transfer through the particles. Therefore, the ultrathin P123-assisted LTO (P-LTO) nanosheets show a rate capability much higher than that of the LTO sample without P123 in a Li battery with over 130 mAh g–1 of capacity remaining at the 64C rate. For intercalation of larger size Na+ ions, the P-LTO still exhibits a capacity of 115 mAh g–1 at a current rate of 10 C and a capacity retention of 96% after 400 cycles.
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Li–S batteries have been considered as the most desirable candidate for next-generation batteries because of their high energy density and low cost, although the problems of the insulating nature of ...S and Li
2
S and the “shuttle effect” of polysulfides in Li–S batteries have to be addressed. In this work, we propose NaCl templates and a solid–liquid coexistence strategy to synthesize an N-doped carbon matrix with interconnected micro-mesoporous structure. Benefiting from the critical state of solid–liquid coexistence at the melting point of NaCl and a pretreatment by pressure, a unique porous structure with an interconnected network of micropores and mesopores is obtained. The micropores can prevent the dissolution of polysulfides, the mesopores can increase the S loading, and the interconnected pore network can significantly improve the usage of active materials. As a result, the cathode with the N-doped carbon matrix shows improved electrochemical performances.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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