Interlayer‐Spacing‐Regulated VOPO₄ Nanosheets with Fast Kinetics for High‐Capacity and Durable Rechargeable Magnesium Batteries

Abstract

Owing to the low-cost, safety, dendrite-free formation, and two-electron redox properties of magnesium (Mg), rechargeable Mg batteries are considered as promising next-generation secondary batteries with high specific capacity and energy density. However, the clumsy Mg with high polarity inclines to sluggish Mg insertion/deinsertion, leading to inadequate reversible capacity and rate performance. Herein, 2D VOPO nanosheets with expanded interlayer spacing (1.42 nm) are prepared and applied in rechargeable magnesium batteries for the first time. The interlayer expansion provides enough diffusion space for fast kinetics of MgCl ion flux with low polarization. Benefiting from the structural configuration, the Mg battery exhibits a remarkable reversible capacity of 310 mAh g at 50 mA g , excellent rate capability, and good cycling stability (192 mAh g at 100 mA g even after 500 cycles). In addition, density functional theory (DFT) computations are conducted to understand the electrode behavior with decreased MgCl migration energy barrier compared with Mg . This approach, based on the regulation of interlayer distance to control cation insertion, represents a promising guideline for electrode material design on the development of advanced secondary multivalent-ion batteries.

Spinel Li4Mn5O12 as 2.0 V Insertion Materials for Mg‐Based Hybrid Ion Batteries

“…The medium bind energy difference suggests the coexistence of Mn 4+ and Mn 3+ in lithiated Li 4 Mn 5 O 12 . The partial Mn 4+ in fully discharged Li 4 Mn 5 O 12 is related with the non‐equilibrium state of the active material during the cycling and the Li + diffusivity is not fast enough to the occurrence of adequately electrochemical reaction on the whole electrode, commonly found in other experiments . After the subsequent charge to 2.7 V (vs. Mg 2+ /Mg), the delithiated Li 4+x Mn 5 O 12 displays two peaks of Mn 2p 3/2 and Mn 2p 1/2 centered at 642.2 eV and 653.9 eV, respectively.…”

“…[49] The partial Mn 4 + in fully discharged Li 4 Mn 5 O 12 is related with the non-equilibrium state of the active material during the cycling and the Li + diffusivity is not fast enough to the occurrence of adequately electrochemical reaction on the whole electrode, commonly found in other experiments. [64] After the subsequent charge to 2. Figure S12 shows the ex-situ XRD patterns of Li 4 Mn 5 O 12 electrodes in various states.…”

Vanadium‐Based Nanomaterials: A Promising Family for Emerging Metal‐Ion Batteries

“…But it was found that pristine VOPO 4 showed poor Mg 2+ storage performance, and the special modifications are necessary. Zhou et al effectively expanded the interlayer spacing of VOPO 4 · 2H 2 O from 0.74 to 1.42 nm by phenylamine molecules preintercalation. The enlarged layer spacing results in the fast diffusion kinetics of MgCl + ions with low polarization.…”

Mg Cathode Materials and Electrolytes for Rechargeable Mg Batteries: A Review

“…A small amount of H 2 O is then generally used in the cathode reaction to shield the divalent Mg 2 + charge by hydration, facilitating the insertion and removal of Mg 2 + ions into/from the oxide cathode to obtain improved cyclability. [94,116,117] However, as discussed in the previous section, H 2 O is not compatible with the anode, and will cause the formation of a passivation layer. Thus, although they provide a higher operating voltage, the use of these transition-metal oxides is still limited.…”