The single-crystal cathode materials exhibit better cyclic stability, enhanced compaction density, and improved safety than polycrystalline cathode materials. They, therefore, are ideal cathode ...material candidates for lithium-ion batteries. Introducing hetero materials, excessive sintering temperature and tedious steps during the synthesis of the single-crystal cathode materials, however, limit their large-scale application. In this work, we adopt the spray pyrolysis method to prepare the hybrid oxides NiO–MnCo2O4–Ni6MnO8. This kind of hybrid oxides is considered to be an ideal precursor for the single-crystal Ni-rich cathode materials owing to its fine particle size and porous structure. Subsequently, high-temperature lithiation synthesises the submicron single-crystal LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode material. The synthesis temperature of the submicron single-crystal NCM811 is significantly lowered when LiNO3 is selected as the lithium source and serves as the flux agent taking advantage of its fusibility. Consequently, the as-synthesized submicron single-crystal NCM811, compared with conventional polycrystalline NCM811, exhibits long lifetime applications, improved thermal stability and micro-crack immunity. The synthetic strategy in this work also demonstrates that the crystal crushing process, flux adding, and repeated sintering are not indispensable in the synthesis of single-crystal cathode materials.
•The spray pyrolysis method is adopted to synthesize Ni0.8Co0.1Mn0.1O1.1 precursor.•A novel strategy are developed to synthesize the single-crystal NCM811.•Single-crystal particles prevent the generation of intergranular cracks.
The paper reports the preparation of nanostructured LiFePO4 cathode with high performance by a phase transition process from the tavorite LiFePO4OH structure to the olivine LiFePO4 structure at ...low-temperature. On the premise of the lattice maturity, a lower crystallization temperature is conducive to synthesizing LiFePO4 with optimal unit cell, crystalline size, and electrochemical property, as well as reducing energy consumption of production.
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•High performance LiFePO4 was obtained by a novel LiFePO4OH precursor at 550–600 °C.•The desirable LiFePO4OH precursor was prepared via a wet pre-lithiation process.•The mechanisms affecting the electrochemical performance of LiFePO4 have been studied.
The main problem currently faced in the large-scale production of LiFePO4 by solid-phase methods is the high energy consumption caused by solid/melt-phase lithiation process. Herein, LiFePO4 nanoparticles are successfully obtained by a phase transition from the tavorite LiFePO4OH structure to the olivine LiFePO4 structure at low-temperature (550–600 °C). This desirable LiFePO4OH precursor is prepared via a wet pre-lithiation process, and its thermodynamic feasibility is demonstrated by thermodynamic calculation. The liquid-phase lithiation followed by a simple carbothermal reduction process (c.f., the solid/melt-phase lithiation process of the traditional solid-state method) results in a superior mass transfer efficiency and reaction uniformity. It therefore prevents the requirement for a higher temperature and longer sintering process. It is also indicated that on the premise of the lattice perfection, a lower crystallization temperature is not only conducive to widening the effective ion diffusion channels of LFP, inhibiting further crystal growth, and shortening the diffusion path, but it also reduces the synthetic cost. As a result, a crystallization temperature of 600 °C (or 550 °C) is optimal, and the resulting LiFePO4 electrode can deliver an appealing high rate capacity of 147.7 mA h g−1 at 10 C. It is expected that this novel synthetic route could be employed for the large-scale commercial production of high performance LiFePO4 cathode materials at a low cost.
SiO
2
-coated LiNi
0.7
Mn
0.15
Co
0.15
O
2
materials were successfully prepared by electrostatic attraction forces method via adjusting the Zeta potential between SiO
2
and LiNi
0.7
Co
0.15
Mn
0.15
O
...2
in the suspension with the followed heating process. The structure, morphology, and electrochemical performances were characterized by XRD, SEM, TEM, XPS, CV, and EIS. As a result, compared with that with 71.4% capacity retention of bare materials, 1.0 wt% SiO
2
-coated LiNi
0.7
Co
0.15
Mn
0.15
O
2
(NCM-S10) could deliver 184.50 mAh g
−1
with 86.4% capacity retention after 100 cycles at 1 C over 3–4.5 V. In high temperature (55 °C), NCM-S10 also has 76.2% capacity retention after 100 cycles (3–4.5 V, 1 C), showing better cycling stability than that of the pristine (61.5%). The SiO
2
coating layer efficiently inhibits side reaction between electrode and electrolyte and maintains the surface structure of LiNi
0.7
Co
0.15
Mn
0.15
O
2
. The increase in impedance is suppressed during the cycle, thereby enhances electrochemical properties of LiNi
0.7
Co
0.15
Mn
0.15
O
2
in high voltage.
The Eh-pH diagrams for Ni-Co-Mn-CO
3
-H
2
O system at various temperatures and ion concentrations are simulated via OLI studio based on the fundamentals of thermodynamic equilibrium. A co-existence ...area for NiCO
3
, CoCO
3
, and MnCO
3
is observed visually from the Eh-pH diagrams, which thermodynamically proves the stability of these species in aqueous solutions, and the possibility of co-precipitating polymetallic carbonate. The simulation results also demonstrate that a higher temperature and/or a more dilute solution are not in favor of the co-precipitation. With the predicted pH ranges from the Eh-pH diagrams, a confirmative experiment was conducted to synthesize Ni
0.13
Co
0.13
Mn
0.54
(CO
3
)
0.8
, the precursor for preparing Li
1.2
Ni
0.13
Co
0.13
Mn
0.54
O
2
, which is a promising cathode material for next-generation LIBs. The physical properties of both materials are characterized in detail, and the electrochemical performance for the final cathode material was tested. The results show that Ni
2+
, Co
2+
, and Mn
2+
ions in solution are homogeneously co-precipitated in the form of polymetallic carbonate. The Li
1.2
Ni
0.13
Co
0.13
Mn
0.54
O
2
material obtained from the carbonate precursor has a typical structure of Li- and Mn-rich cathodes and yields an initial discharge capacity of 296.0 mAh g
−1
at 0.1 C and 188.1 mAh g
−1
after 100 cycles at 1 C rate. It was verified that the OLI-assisted Eh-pH simulation is consistent with the experimental measurements.
Electrode-electrolyte interface side reactions cause the fast capacity fading of Ni-rich cathode, especially at high cutoff voltages and high temperatures. This is the main obstacle for their ...commercial application. Herein, a hybrid ZrO
2
-Li
2
ZrO
3
(LZO) coating layer was fabricated through a wet process on LiNi
0.7
Co
0.15
Mn
0.15
O
2
(NCM) cathode materials. The structure and chemical composition of the ZrO
2
-Li
2
ZrO
3
coating layer were studied by the characterizations of XRD, SEM, TEM, and XPS. The ZrO
2
-Li
2
ZrO
3
-coated LiNi
0.7
Co
0.15
Mn
0.15
O
2
cathode improved cycling stabilities at both 25 and 55 °C in the case of high cutoff voltage. In detail, ZrO
2
-Li
2
ZrO
3
-coated NCM (LZO-NCM) delivers a 187.40 mAh g
−1
with 83.4% capacity retention after 100 cycles at 1C over 3.0–4.5 V, and it is far higher than that of uncoated sample (71.4%). At elevated temperature (55 °C), the ZrO
2
-Li
2
ZrO
3
-coated sample also maintains 79% capacity retention after 100 cycles (3.0–4.5 V, 1C), which is higher than the 61.5% capacity retention of the pristine electrode. The hybrid ZrO
2
-Li
2
ZrO
3
coating could not only keep the bulk structure stability but also prevent the electrochemical resistance which varies after cycles. Thereby, the electrochemical properties were improved significantly.
A technology has been developed for extracting tungsten from scheelite concentrate with caustic soda by an autoclaving process. In this process, the effects of different variables on the digestion of ...scheelite, and on the evaporation of the crude sodium tungstate leach solution, has been investigated. The results showed that 98.8% W was leached in 2
h at 160
°C under the conditions of 2.2 stoichiometric ratio of NaOH and liquid /solid ratio 0.8:1 stirred at 400
rpm. After evaporation, about 90% sodium tungstate was crystallized, leaving impurities of PO
4
2-, AsO
4
2− and SiO
3
2− in the mother solution. The filtered mother solution contained about 93% of the unconsumed caustic soda which can be recycled for a new round of leaching. This technology has been successfully put into industrial practice and can treat almost any tungsten ore, including scheelite middling and wolframite–scheelite mixed concentrates.
► Scheelite concentrate can be digested well with caustic soda in general equipments. ► The unconsumed NaOH can be recovered by evaporation. ► The impurities P, As, Si were precipitated in the leach residue. ► The technology has been put into industrial practice successfully in China.
Sodium-ion batteries (SIBs) with huge cost advantages will show extraordinary talents in low-speed electric vehicles, energy storage, and base station communications. Manganese oxides are promising ...candidates for cathode materials, rapid capacity decay, and poor electrochemical performance that limit its commercial applications. Here, the nanosheets with exposed active crystal planes are prepared through a simple NH
3
∙H
2
O-assisted sol-gel process and subsequent high-temperature calcination. The unique structure considerably reduces the Na
+
diffusion path for the excellent Na
+
diffusion kinetics. The final results confirm that the NMO-pH6 sample, exposed to the active planes, has high energy density (557.9 Wh kg
−1
at 0.1 C) and outstanding electrochemical performance, especially the rate performance (93.8 mAh g
−1
at 5 C and 79.95 %, 100 cycles at 1 C). More importantly, it will facilitate the further construction of advanced cathode materials for high-performance SIBs.
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
.
High-nickel material is a high energy density cathode. However, its practical application is hindered by the structure and surface instability that cause severe capacity fading during cycling. In ...this study, a one-step approach of AlPO
4
modification to create Li
3
PO
4
-LiAlO
2
coating layer on LiNi
0.8
Co
0.1
Mn
0.1
O
2
cathode materials is reported. The Li
3
PO
4
-LiAlO
2
protective coating can not only mitigate the structure degradation near the surface, but also protect from the attacking of HF and H
2
O to the bulk surface. The AlPO
4
-modified materials exhibit excellent electrochemical properties, where its initial discharge capacity is up to 190.2 mAh g
−1
at 1C over 3.0–4.4 V, and the corresponding retention after 100 cycles also increases to 96.42%. Overall, this work offers some meaningful insights on addressing the structure and surface instability, and enhancing the properties of high-nickel materials, which can be of great importance for the further development and commercialization of high-nickel materials.
