The strong push for electric vehicles and large-scale power storage systems has generated intense interest in rechargeable magnesium batteries due to the innate merits associated with the magnesium metal anode in terms of volumetric capacity, abundance, and operational safety. Herein, we report a novel pathway toward the development of an advanced battery containing a magnesium anode, a titanium dioxide cathode, and a magnesium borohydride/tetraglyme electrolyte, which delivers high specific capacity, as well as exceptional cycle life and rate capability. This work demonstrates the importance of compatibility of the electrochemical activities of the cathode materials and electrolytes in rechargeable Mg batteries.

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. (2016). A high-performance rechargeable Mg2+/Li+ hybrid battery using one-dimensional mesoporous TiO2(B) nanoflakes as the cathode. ACS Applied Materials and Interfaces, 8 (11),[7111][7112][7113][7114][7115][7116][7117] A high-performance rechargeable Mg2+/Li+ hybrid battery using onedimensional mesoporous TiO2(B) nanoflakes as the cathode AbstractMg2+/Li+ hybrid batteries have recently been constructed combining a Mg anode, a Li+-intercalation electrode, and an electrolyte containing both Mg2+ and Li+. These batteries have been reported to outperform all the previously reported magnesium batteries in terms of specific capacity, cycling stability, and rate capability. Herein, we report the outstanding electrochemical performance of Mg2+/Li+ hybrid batteries consisting of a one-dimensional mesoporous TiO2(B) cathode, a Mg anode, and an electrolyte consisting of 0.5 mol L-1 Mg(BH4)2 + 1.5 mol L-1 LiBH4 in tetraglyme. A highly synergetic interaction between Li+ and Mg2+ ions toward the pseudo-capacitive reaction is proposed. The hybrid batteries show superior rate performance with 130 mAh g-1 at 1 C and 115 mAh g-1 at 2 C, together with excellent cyclability up to 6000 cycles.

The electrolytes containing halide-free inorganic magnesium salt Mg(BH 4 ) 2 dissolved in ether solvents have shown reversible Mg deposition-dissolution performance. Herein, we improved the anodic stability of the electrolytes on non-inert stainless-steel electrode by mixing PP 14 TFSI ionic liquid with tetraglyme (TG) and dimethoxyethane (DME) ether solvents. The effect of mixing ratios and salt concentrations on the electrochemical behavior of the electrolyte were investigated. High anodic stability, good ionic conductivity, excellent cycling efficiency, feasibility of the preparation and good compatibility toward Mo 6 S 8 and TiO 2 insertion cathode make the electrolytes promising for the potential application in rechargeable magnesium batteries. 3-5 The development of magnesium electrolytes is considered as the most important challenge for the commercial application of rechargeable magnesium batteries because electrolyte properties govern battery performance and determine the class of cathodes to be utilized. 6 The significant progress is the reports of 0.25 mol L −1 Mg(AlCl 2 BuEt) 2 /THF (Bu=butyl, Et=ethyl) electrolyte 7,8 and 0.4 mol L −1 (PhMgCl) 2 -AlCl 3 /THF electrolyte, 9,10 which have high anodic stability (2.5 V and 3.3 V vs. Mg RE on inert Pt electrode, respectively) and reversibility of Mg deposition-dissolution. Recently, a family of novel boron based electrolytes with high ionic conductivity, excellent Mg deposition reversibility as well as high anodic potential were proposed.11,12 On the other hand, phenolate-based 13 and alkoxide-based 14 electrolytes exhibit air insensitive character and excellent magnesium depositiondissolution performance. Meanwhile, inorganic magnesium salt solutions synthesized by the acid-base reaction of MgCl 2 and Lewis acidic compounds such as AlCl 3 show high coulombic efficiency, low overpotential for magnesium deposition-dissolution and good anodic stability. [15][16][17][18] However, these electrolytes may corrode non-inert current collectors at lower anodic potentials duo to the presence of halides in the cation and anion components of the electrolytes, although some of these electrolytes have shown impressive stability against electrochemical oxidation.19 Hence, it is still necessary to find electrolytes with high stabilities on non-inert current collectors for a practical rechargeable Mg battery system. Nelson et al. showed that decreasing the chloride content in Mg electrolytes by switching the Lewis acid from AlCl 3 to Al(OPh) 3 greatly improves the anodic stability up to 5 V on both Pt and stainless steel electrodes.20 Ha et al. proposed a new class of electrolytes based on magnesium (II) bis(trifluoromethane sulfonyl)imide (Mg[N-(SO 2 CF 3 ) 2 ] 2 , Mg(TFSI) 2 ) dissolved in glymebased solvents with unique characteristics such as highly reduced corrosive nature toward the current collector, low volatility, high solvating power, and the ability to form an appropriate solvation sheath structure for Mg deposition-dissolution. 21 Recently, a whole new promisi...

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Theeffectsofdifferentcathodecurrentcollectors(stainlesssteel,nickel,copper,andtitanium)on theelectrochemicalperformanceofrechargeablemagnesiumbatterieswereinvestigated.ChevrelphaseMo6S8 actedasthecathode,(PhMgCl)2-AlCl3/tetrahydrofuran(THF)(thesecondgenerationelectrolyte)asthe electrolyte,andmagnesiumastheanode.Constantcurrentdischarge-chargeresultsindicatedthatthe electrochemicalpolarizationoftheelectrodeonstainlesssteelwasthesmallestanditscyclingstabilitywasthe best,followedbynickel,copper,andtitanium.Microstructureanalysesfortheelectrodesandcurrentcollectors beforeandafterdischarge-chargewereanalyzedtoinvestigatethedifferingelectrochemicalperformance.The electrolytecorrodedthecurrentcollectorstodifferingdegrees.Thesurfacesoftheelectrodesdifferedafter coatingtheactivematerialondifferentcurrentcollectors.Thecorrosionpotentialsofthecurrentcollectors decreasedafterloadingtheactivematerial.Thisresultedinthecurrentcollectorsbeingmoresusceptibleto corrosionbytheelectrolyte.