Controlling the Intercalation Chemistry to Design High-Performance Dual-Salt Hybrid Rechargeable Batteries

Abstract

We have conducted extensive theoretical and experimental investigations to unravel the origin of the electrochemical properties of hybrid Mg(2+)/Li(+) rechargeable batteries at the atomistic and macroscopic levels. By revealing the thermodynamics of Mg(2+) and Li(+) co-insertion into the Mo6S8 cathode host using density functional theory calculations, we show that there is a threshold Li(+) activity for the pristine Mo6S8 cathode to prefer lithiation instead of magnesiation. By precisely controlling the insertion chemistry using a dual-salt electrolyte, we have enabled ultrafast discharge of our battery by achieving 93.6% capacity retention at 20 C and 87.5% at 30 C, respectively, at room temperature.

Prussian Blue MgLi Hybrid Batteries

“…The full cell with an Mg counter electrode reaches ≈125 mAh g −1 capacity at an average voltage of 2.3 V with a moderate 10 mA g −1 rate (≈C/10), resulting in an energy density of 290 Wh kg −1 . Such results represent higher performance compared to the state‐of‐the‐art hybrid cell with a Chevrel Mo 6 S 8 cathode that operates at an average voltage of 1.4 V and yields 170 Wh kg −1 energy density 12, 13. At much higher current densities (2C rate), the Prussian blue cell still delivers 150 Wh kg −1 , which is comparable, albeit a little lower, to the Chevrel that is reported to provide an energy density of 165 Wh kg −1 .…”

Two-Dimensional Titanium Carbide MXene As a Cathode Material for Hybrid Magnesium/Lithium-Ion Batteries

“…The Chevrel phase, Mo 6 S 8 , was the first reported and widely investigated cathode material for hybrid Mg 2+ /Li + batteries. 11,12 Significant improvements in capacity and rate capabilities were demonstrated when compared with Mg-ion battery systems in which no Li + -containing salts were added to the electrolyte. 9 Following that, lithium iron phosphate (LiFePO 4 ), titanium disulfide (TiS 2 ), and titanium dioxide (TiO 2 ) were also employed as cathode materials in hybrid Mg 2+ /Li + battery systems.…”

Improving the Electrochemical Performance of the Li4Ti5O12 Electrode in a Rechargeable Magnesium Battery by Lithium–Magnesium Co‐Intercalation

“…In the Li battery,t he LTOe lectrode will turn to Li 7 Ti 5 O 12 ,w ritten as Li 6 Ther esults shown in Figure 1i ndicate that the phase separation reaction is energetically favorable.T he discussion above is based on the supposition that Mg/Li co-insertion/ extraction can occur in LTO. In the Li battery,t he LTOe lectrode will turn to Li 7 Ti 5 O 12 ,w ritten as Li 6 Ther esults shown in Figure 1i ndicate that the phase separation reaction is energetically favorable.T he discussion above is based on the supposition that Mg/Li co-insertion/ extraction can occur in LTO.…”

“…[4d,e, 5] Howeveru sing aL TO anode for ar echargeable Mg battery also faces the problem of kinetically sluggish Mg insertion/extraction and diffusion in electrode materials.A s such Mg insertion behavior into LTOn anoparticles (LTO NPs) is strongly dependent on size. [6] In this work, we report af acile approach to eliminate the size dependencies of LTOelectrodes during Mg insertion/extraction, resulting in electrode materials with large particle sizes (larger than 100 nm) useful in Mg batteries.D ensity functional theory calculations reveal possibilities for the thermodynamics of Mg 2+ and Li + co-insertion into large sized LTOe lectrodes and experimental investigations show that the electrochemical behavior of large sized LTOelectrodes combining Mg and Li electrochemistry in Mg battery systems is dependent on the lithium salt concentration in the electrolytes.T uning the Li + activity in the electrolyte properly results in large LTON Ps indicating excellent electrochemical performances in terms of specific capacity, cycling performance,a nd especially rate performance. Worse,L TO NPs with particle sizes larger than 100 nm are negligible in Mg battery systems.Thus,exploring appropriate approaches for increasing the kinetics of ion insertion-type electrode materials with large particle size,w hich has more practical advantages,i sh ighly desired in Mg batteries.…”