Characterization of ceramic coating on ZK60 magnesium alloy prepared in a dual electrolyte system by micro-arc oxidation

Micro-arc oxidation （MAO） process was cartied out in an optimized dual electrolyte system to fabricate a compact, smooth, and corrosion resistant coating on ZK60 Mg alloy. The microstructural characteristics of coating were investigated by scanning electron microscopy （SEM） coupled with an energy dispersive spectrometer （EDS） and X-ray diffraction （XRD）. Test of mass loss was conducted at a 3.5 % NaCl solution to assess the resistance to corrosion. The bonding strength between the coating and ZK60 substrate was evaluated using scratch experiment. The results reveal that MgA1204 and MgO are the main phases of ceramic coating obtained in the dual electrolyte system. The corrosion rate of coating prepared in the optimized dual electrolyte is only 0.0061 g.m-2.h-1, which demonstrates excellent corrosion resistance. This is mainly due to the compact, uniform coating with high bonding strength.

Synergistic interphase modification with dual electrolyte additives to boost cycle stability of high nickel cathode for all-climate battery

B-containing electrolyte additives are widely used to enhance the cycle performance at low temperature and the rate capability of lithium-ion batteries by constructing an efficient cathode electrolyte interphase(CEI)to facilitate the rapid Li+migration.Nevertheless,its wide-temperature application has been limited by the instability of B-derived CEI layer at high temperature.Herein,dual electrolyte additives,consisting of lithium tetraborate(Li_(2)TB)and 2,4-difluorobiphenyl(FBP),are proposed to boost the widetemperature performances of LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)(NCM)cathode.Theoretical calculation and electrochemical performances analyses indicate that Li_(2)TB and FBP undergo successive decomposition to form a unique dual-layer CEI.FBP acts as a synergistic filming additive to Li_(2)TB,enhancing the hightemperature performance of NCM cathode while preserving the excellent low-temperature cycle stability and the superior rate capability conferred by Li_(2)TB additive.Therefore,the capacity retention of NCM‖Li cells using optimal FBP-Li_(2)TB dual electrolyte additives increases to 100%after 200 cycles at-10℃,99%after 200 cycles at 25℃,and 83%after 100 cycles at 55℃,respectively,much superior to that of base electrolyte(63%/69%/45%).More surprisingly,galvanostatic c ha rge/discharge experiments at different temperatures reveal that NCM‖Li cells using FBP-Li_(2)TB additives can operate at temperatures ranging from-40℃to 60℃.This synergistic interphase modification utilizing dual electrolyte additives to construct a unique dual-layer CEI adaptive to a wide temperature range,provides valuable insights to the practical applications of NCM cathodes for all-climate batteries.

Optimization of dual electrolyte and characteristic of micro-arc oxidation coating fabricated on ZK60 Mg alloy

Micro-arc oxidation （MAO） process was carried out in a dual electrolyte system of NaAlO 2 and Na 3 PO 4 to develop compact, smooth and corrosion-resistant coatings on ZK60 Mg alloy by single factor experiments. The microstructural characteristics of coatings were investigated by X-ray diffractometry （XRD） and scanning electron microscopy （SEM） coupled with energy dispersive X-ray spectroscopy （EDS）. Test of mass loss was conducted at a 3.5% NaCl solution to assess the resistance to corrosion. The effect of every element in the dual electrolyte system on voltage—time responses during MAO process and the coating characteristic were also analyzed and discussed systematically via single factor experiments. The results reveal that the main components of NaAlO 2 and Na 3 PO 4 as well as additives of NaOH, NaB4O7 and C6H5Na3O7 demonstrate different effects on MAO process and coating characteristics. By means of single factor experiments, an optimized dual electrolyte system was developed, containing 17.5 g/L NaAlO 2, 5.0 g/LNa3 PO4, 5.0 g/L NaOH, 3.0 g/L NaB4O7 and 4.2g/LC6H5Na3O7 .

Microarc oxidation coating fabricated on AZ91D Mg alloy in an optimized dual electrolyte

Microarc oxidation （MAO） process was conducted on AZ91D magnesium alloy in an electrolyte composed of NazSiO3, NaAlO2, NaEB4O7, NaOH, C3H803 and C6H5Na307 by AC pulse electrical source. The surface and cross-sectional morphologies, film thickness, chemical composition and structure of the coatings were characterized by scanning electron microscopy（SEM）, layer thickness metry, energy disperse spectroscopy（EDS） and X-ray diffraction（XRD）. The corrosiofi resistances of the coatings in a 3.5% NaC1 neutral solution were evaluated by electrochemical impedance spectroscopy （EIS） and potentiodynamic polarization test. The results showed that an optimized electrolyte with a composition of 15 g/L NazSiO3, 9 g/L NaA102, 2 g/L NazB407, 3 g/L NaOH, 5 mL/L C3H803 and 7 g/LC,HsNa307 was developed by means of orthogonal experiment. The coating obtained in the optimized electrolyte had a dense structure and revealed a lower current density, decreased by two orders of magnitude as compared with the magnesium substrate. Meanwhile, the corrosive potentials of the coated samples increased nearly by 73 inV. EIS result showed that the corrosion resistance of the coating was mainly determined by the inner dense layer. The coating primarily contained elements Mg, Al, O and Si and XRD analyses indicated that the coating was mainly composed of MgO, Mg2SiO4 and MgAl204.

Solvent sieving separators implement dual electrolyte for highvoltage lithium-metal batteries

Lithium-metal batteries(LMBs)based on high-voltage cathodes would deliver high specific energy density to meet the demand of future energy storage.However,developing liquid electrolytes with wide electrochemical window for high-energy LMBs is intrinsically challenging.Herein,we demonstrate metal-organic framework-functionalized separators(PE@MOF)with solvent sieving capability that implement dual electrolyte for LMBs.The capability of PE@MOF separator to block the diffusion of liquid electrolytes has been investigated.The PE@MOF separator notably suppresses solvents shuttling,enabling the independent optimization of cathode-electrolyte and anode-electrolyte interfaces.By adapting commercial carbonate and ether electrolytes on cathode and anode sides,respectively,robust cathode-electrolyte interphase(CEI)and solid electrolyte interface(SEI)have been built on both electrodes.The lifespan of LiCoO_(2)(LCO)|Li full cell has been notably extended when using dual electrolyte and the solvent-sieving PE@MOF separator.This work demonstrates a new strategy to separately optimize the local environments at electrodes and to develop high-energy LMBs using low-cost and commercially available electrolytes.