Fe₂O₃ Nanoparticle Seed Catalysts Enhance Cyclability on Deep (Dis)charge in Aprotic LiO₂ Batteries

Abstract

decomposition (oxygen evolution reaction, OER) of Li 2 O 2 according to the reaction 2Li O Li O 2 discharge charge 2 2. [1] Therefore, the performance of this battery is determined by the reversibility of Li 2 O 2 redox and the electrolyte stability. [1] The morphology and mechanism of Li 2 O 2 deposition depends on the relative stability of the intermediate LiO 2 product in the electrolyte and the time scale of the Li 2 O 2 formation on the cathode surface. While LiO 2 stability is determined by the stabilization of the Li + both through the solvation strength of the electrolyte (quantified by the donor number (DN)) and the association strength of the counter anion, [5][6][7] the time scale determines to what extent the intermediate LiO 2 species are solvated. [8] In an intermediate DN electrolyte, such as tetraethylene glycol dimethyl ether (TEGDME), the nucleation and growth of toroidal Li 2 O 2 particles were proposed to occur via the solution dismutase mechanism at low current rates, whereas at fast rates quasi-amorphous thin films were observed on electrode surface. [8] Porous carbon based materials have been extensively explored as O 2 gas diffusion electrodes because of their high surface area, low weight, and low cost. Unfortunately, the discharge product Li 2 O 2 reacts with carbon and the electrolyte at high potentials that characterize the OER process, and forms byproducts that clog the electrode pores, resulting in capacity fading and poor cycling stability. [9,10] Significant efforts have been expended in mitigating these side reactions by employing several combinations of noble metals (Au, Ru/RuO 2 , and Pt), [11][12][13][14][15][16][17][18][19][20][21] transition metal oxides (MnO 2 , Co/CoO/Co 3 O 4 , NiO, and TiO 2 ), [22][23][24][25][26][27][28][29][30][31][32][33] and metal-related compounds, [34][35][36][37][38][39][40] both as catalysts and conductive matrices to improve the energy efficiency and cycle life of the LiO 2 batteries.Most often the reported cycling performance of LiO 2 systems is based on capacity-limited cycling, rather than the preferred potential-limited cycling where the full electrode capacity is utilized. Capacity-limited cycling performance of batteries makes it difficult to quantify if improved cycling stability can be attributed to the specific role of electrode or to the continuous consumption of new active sites on the electrode surface is delivered. To date, the only electrode systems that have displayed improved reversible Li 2 O 2 formation and decomposition during potential limited cycling in aprotic LiO 2 batteries are porous gold, [14] metallic RuO 2 , [41,42] the metallic porous Although the high energy density of LiO 2 chemistry is promising for vehicle electrification, the poor stability and parasitic reactions associated with carbonbased cathodes and the insulating nature of discharge products limit their rechargeability and energy density. In this study, a cathode material consisting of α-Fe 2 O 3 nanoseeds and carbon nanotubes (CNT) is presented, which...

Superassembly of Porous Fetet(NiFe)octO Frameworks with Stable Octahedron and Multistage Structure for Superior Lithium–Oxygen Batteries

“…Within the potential window of 2.35–4.35 V, the contribution of Li‐intercalation reaction and pseudocapacitive charge storage to the discharge capacity of the NiFeO cathode can be negligible as demonstrated in previous work at an inert gas. [ 42,59 ] The electrochemical performance of NiFeO‐600 was significantly improved compared with a series of Ni, Fe based bimetallic electrocatalyst according to previous reports, as schematically shown in Table S2 (Supporting Information). The outstanding performance of the NiFeO‐600 cathode can be attributed to the synergistic effect of hierarchical porous structure and modified intrinsic character.…”

“…It suggested that the discharge capacity decrease accompanied by charge polarization deterioration with increase of current density can be ascribed to the internal charge transfer resistance of LOBs. [ 59 ] Impressive specific capacities of 20 440, 16 609, 12 003, and 9704 mAh g −1 can be still obtained by NiFeO‐600 at high current densities of 200, 500, 800, and 1000 mA g −1 , respectively, while the rate capacity of other electrodes were far less than that of NiFeO‐600 as recorded in Figure S8 (Supporting Information), indicating the significant advantage of high rate capability for NiFeO‐600.…”

Recent Progress on Catalysts for the Positive Electrode of Aprotic Lithium-Oxygen Batteries †

“…Thus, it is challenging to regulate all the transition-metal-based catalysts in one article. Some other alternative mechanisms were also suggested, such as the epitaxial growth of nanosized Li 2 O 2 enabled by Fe 2 O 3 positive electrode [125], quite a similar concept to the Ir 3 Li as the template for the epitaxially induced nucleation and growth LiO 2 in Lu's work [84]. Additionally, an optimized sp 2 /sp 3 carbon bond was proposed by introducing CuCeO 3 nanorods to graphene nanosheet, together with the stabilized Cu + /Cu 2+ redox pair enabled by the solid support of Ce element.…”

Embedded Growth of Li2O2 Achieved by a Rational Designed Three‐Dimensional Fe2O3@CNS‐CNTs Sandwich Structure for Improving the Performance of Li–O2 Batteries

“…[ 22 ] Of note, Wagemaker and co‐workers studied a cathode consisting of α‐Fe 2 O 3 nanoparticle and carbon nanotubes (CNTs), in which the similar lattice plane d‐spacing of α‐Fe 2 O 3 (104) and Li 2 O 2 (100) induced the epitaxial growth of Li 2 O 2 on the α‐Fe 2 O 3 surface, resulting in the well‐distributed and regulated deposition of Li 2 O 2 and enhanced cycling stability on deep (dis)charge. [ 23 ] Moreover, Jung et al reported an electrode consisting hollow Fe 2 O 3 nanoparticles anchored by multiple CNTs, which offered enhanced catalytic sites and fast charge‐transport highway for facile formation and decomposition of Li 2 O 2 , leading to outstanding cell performances. [ 24 ] These results demonstrate the potential prospects of Fe 2 O 3 as the oxygen cathode catalyst.…”