Enabling Fast Na⁺ Transfer Kinetics in the Whole‐Voltage‐Region of Hard‐Carbon Anodes for Ultrahigh‐Rate Sodium Storage

Abstract

Efficient electrode materials, that combine high power and high energy, are the crucial requisites of sodium‐ion batteries (SIBs), which have unwrapped new possibilities in the areas of grid‐scale energy storage. Hard carbons (HCs) are considered as the leading candidate anode materials for SIBs, however, the primary challenge of slow charge‐transfer kinetics at the low potential region (<0.1 V) remains unresolved till date, and the underlying structure–performance correlation is under debate. Herein, ultrafast sodium storage in the whole‐voltage‐region (0.01–2 V), with the Na+ diffusion coefficient enhanced by 2 orders of magnitude (≈10–7 cm2 s–1) through rationally deploying the physical parameters of HCs using a ZnO‐assisted bulk etching strategy is reported. It is unveiled that the Na+ adsorption energy (Ea) and diffusion barrier (Eb) are in a positive and negative linear relationship with the carbon p‐band center, respectively, and balance of Ea and Eb is critical in enhancing the charge‐storage kinetics. The charge‐storage mechanism in HCs is evidenced through comprehensive in(ex) situ techniques. The as prepared HCs microspheres deliver a record high rate performance of 107 mAh g–1 @ 50 A g–1 and unprecedented electrochemical performance at extremely low temperature (426 mAh g–1 @ −40 °C).

Pore Structure Modification of Pitch‐Derived Hard Carbon for Enhanced Pore Filling Sodium Storage

“…In this stage, the kinetic bottleneck lies on the Na + diffusion between the graphitic layers, and a wider graphitic layer spacing favors the fast Na + diffusion. [ 35,36 ] Recently, Wu et al found that the solvent cointercalation mechanism of hard carbon in ether electrolytes can lead to an increase in the interlayer spacing of hard carbon, which in turn results in the significant improvement of sodium ion diffusion and kinetic performance, this result was consistent with the earlier analysis. [ 37 ] Besides, compounding hard carbon with other sodium storage materials with fast Na + diffusion may also improve its kinetic performance.…”

Niobium-doped layered cathode material for high-power and low-temperature sodium-ion batteries

“…Next, mixed the carbonate precursor of 0.01 mol, with 0.004 mol Na 2 CO 3 and 1.27 × 10 −4 mol Nb 2 O 5 into planetary ball mills and milling with high energy in air with 1000 rpm at 25 °C for 6 h. The power was calcined at 500 °C for 10 h and then sintered in corundum crucible at 900 °C for 12 h in Muffle furnace in air atmosphere with heating rate of 5 °C / min and cooled down to room temperature. Polyvinylidene fluoride (PVDF, 99.5%, Alfa Aesar), N-Methyl pyrrolidone (NMP, 99.5%, Alfa Aesar), hard carbon (average particle size of 1.1 nm; in-house prepared via bottom-up ZnO-assisted bulk etching strategy 66 ), acetylene black (99.5%, Alfa Aesar, average particle size: 300 nm). Al foil (20 μm, 99.5%, Alfa Aesar) and Cu foil (18 μm 99.5%, Alfa Aesar), Na metal foil (99%, Alfa Aesar), Na discs were rolled into thin pieces and punched out of the large Na metal chunks (diameter: 16 mm, thickness: 0.5 mm).…”

Atomic-interface strategy and N,O co-doping enable WS2 electrodes with ultrafast ion transport rate in sodium-ion batteries

“…This phenomenon may result from the structural instability in the initial activation stage at high current density, 12 which was also commonly found in previous reports on SIB anodes. 12–15 The cycling performances under high current densities were superior to previously reported WS 2 -based anode materials for SIBs (Fig. 4g and Table S10†).…”

“…5–8 However, the large radius of Na + (∼0.106 nm) endows anode materials with sluggish ionic-transport kinetics, thus resulting in poor fast-charging capability. 9,10 To solve this tricky problem, a multitude of anode materials with well-designed structures, such as metals, 11,12 metal sulfides, 13 metal oxides, 14 hard carbon, 15,16 and graphene, 17 have been demonstrated with good rate performances. However, the anode materials possessing ultrafast Na + -storage capability, together with ultrahigh capacity and an ultralong working lifetime, are highly required for fast-charging SIBs, which still is a huge challenge up to now.…”