A durable P2-type layered oxide cathode with superior low-temperature performance for sodium-ion batteries

Abstract

To power large-scale energy storage systems, sodium-ion batteries (SIBs) must have not only high-energy density but also high performance under a low-temperature (LT) environment. P2-type manganese oxides with high specific capacity are promising cathode candidates for SIBs, but their LT applications are limitedly explored. We proposed a P2-type Na 0.67 Ni 0.1 Co 0.1 Mn 0.8 O 2 material with outstanding LT performance prepared through reasonable structure modulation. The material offers an excellent Na + diffusion coefficient (approximately 10 −9 -10 −7.5 cm 2 s −1 ) at −20°C, a superior LT discharge capacity of 147.4 mA h g −1 in the Na half-cell system, and outstanding LT full cell performance (energy density of 358.3 W h kg −1 ). Various characterisations and density function theory calculations results show that the solid solution reaction and pseudocapacitive feature promote the diffusion and desolvation of Na + from the bulk electrode to interface, finally achieving superior electrochemical performance at LT.

Zn/Ti/F synergetic-doped Na0.67Ni0.33Mn0.67O2 for sodium-ion batteries with high energy density

“…5e and f), Na + diffusion coefficients with the voltage of NNMO and NNZMTOF samples were measured by GITT. If Es as a function of s is linear, then the Na + diffusion coefficient can be calculated by simplied eqn (1): 56,57…”

“…5e and f), Na + diffusion coefficients with the voltage of NNMO and NNZMTOF samples were measured by GITT. If Eτ as a function of τ is linear, then the Na + diffusion coefficient can be calculated by simplified eqn (1): 56,57 where D Na + (cm 2 s −1 ) represents the Na + diffusion coefficient, V M (cm 3 mol −1 ), m B , and M B are the molar volume, weight, and molar weight of the active materials, respectively, A and τ (s) denote the surface area of the electrode and the testing time in each step, and Δ E s and Δ E τ are the quasi-equilibrium potential and the change in cell voltage E during the current pulse, respectively. D Na + values were calculated for comparison according to eqn (1).…”

The prospect and challenges of sodium‐ion batteries for low‐temperature conditions

“…As a representative of P 2 ‐type cathode material, Na 0.67 MnO 2 has a limited reversible capacity (108.3 mAh g −1 at 0.2 C under −20°C) due to the slow diffusion rate caused by the ordered arrangement of Na + and vacancies in the crystal framework at low temperatures. [ 91 ] The synergistic effect of multiple transition metals is an effective approach to improving electrochemical performance. As a result, a P 2 ‐type‐layered Na 0.67 Ni 0.1 Co 0.1 Mn 0.8 O 2 with an optimized structure was designed, and the doped ions had an obvious inhibitory effect on the Jahn–Teller distortion of Mn ions according to the results of density functional theory calculation, which could effectively shield the electrostatic interaction of Na + /vacancy ordering and enlarge the interstitial space.…”

A high-performance Na-storage cathode enabled by layered P2-type KxMnO2 with enlarged interlayer spacing and fast diffusion channels for sodium-ion batteries

“…[10][11][12][13][14][15] Thereinto, the P2-type Na x MnO 2 cathode delivering a high capacity of ∼150 mA h g −1 with better reversibility has attracted special attention. [16][17][18][19] However, the relatively larger size of Na + diffused in layered channels of P2-type Na x MnO 2 easily causes severe volume deformation and mechanical stress, which will accelerate the collapse of the layered structure, thus resulting in inferior rate capability and poor cycling stability. Expanding the interlayer lattice of Na + host materials favors enlarging ion diffusion channels which can enhance the capacity and increase the ion diffusion rate, thus improving electrochemical performance.…”