A Novel Strategy toward High‐Performance Lithium Storage of Li₄Ti₅O₁₂ Using Cu₂V₂O₇ as Additive

Abstract

Rechargeable lithium-ion batteries (LIBs) are important energy storage devices, widely used in portable electronic products, hybrid electric vehicles, and smart grids. [1][2][3][4][5] However, the cycle stability of LIBs cannot meet the requirements of electric vehicles. Commercial carbon is the most widely used anode material of LIBs, but it is affected by low voltage and lithium dendrite formation. [6][7][8] Therefore, it is of great significance to develop LIB anode materials with high safety and good stability.Li 4 Ti 5 O 12 with spinel structure is a potential anode material for LIB exchange, thanks to its unique structural stability, zero volume change, as well as its relatively stable and high potential plateau (about 1.55 V) during Li þ deinsertion/insertion to reduce the formed lithium dendrite. [9][10][11][12] However, the poor electronic conductivity of Li 4 Ti 5 O 12 and its low ion-diffusion coefficient limit its large-scale application. [13,14] Therefore, overcoming the shortcomings of Li 4 Ti 5 O 12 is of great significance to advanced uses. [13,15,16] Several methods have been utilized to enhance the conductivity of Li 4 Ti 5 O 12 , including doping with various metal ions (Mn 4þ , Zr 4þ , and F À ), [17][18][19][20] combined with highly conductive materials (C and Cu, etc.) [16,[21][22][23][24][25][26][27][28] and the reduction in size through the synthesis of nano-Li 4 Ti 5 O 12 . [29][30][31] The vanadium-based compounds generally exhibit good chemical stability and better safety characteristics in LIBs. [32,33] Among them, numerous copper vanadium oxides with different structures, such as Cu 2 V 2 O 7 , Cu 3 V 2 O 8 , and CuV 2 O 6 , have recently been tested due to their high redox potentials and simple synthesis methods. [34][35][36] Among these, Cu 2 V 2 O 7 made of an orthorhombic system with space group Fdd2 and lattice parameters (a ¼ 2.0645 nm, b ¼ 0.8383 nm, c ¼ 0.6442 nm, α¼ 90 ∘ , β¼ 90 ∘ , γ¼ 90 ∘ ) has been tested as anode material of LIBs for the reasons of low cost, superior energy density, and excellent specific capacity. Applied in the first discharge process of LIBs, Cu 2 V 2 O 7 will produce metallic copper, and produce a voltage window at about 2.5 V, greatly improving the electrical properties of anode materials for LIBs. [37,38] More importantly, Cu in the lower voltage range (1.0À3.0 V) will not be oxidized to copper ions, meaning irreversible anode processes. Therefore, the addition of appropriate