Suppression of Parasitic Chemistry in Li–O 2 Batteries Incorporating Thianthrene-Based Proposed Redox Mediators

Conversion/alloy active materials, such as ZnO, are one of the most promising candidates to replace graphite anodes in lithium-ion batteries. Besides a high specific capacity (q ZnO = 987 mAh g–1), ZnO offers a high lithium-ion diffusion and fast reaction kinetics, leading to a high-rate capability, which is required for the intended fast charging of battery electric vehicles. However, lithium-ion storage in ZnO is accompanied by the formation of lithium-rich solid electrolyte interphase (SEI) layers, immense volume expansion, and a large voltage hysteresis. Nonetheless, ZnO is appealing as an anode material for lithium-ion batteries and is investigated intensively. Surprisingly, the conclusions reported on the reaction mechanism are contradictory and the formation and composition of the SEI are addressed in only a few works. In this work, we investigate lithiation, delithiation, and SEI formation with ZnO in ether-based electrolytes for the first time reported in the literature. The combination of operando and ex situ experiments (cyclic voltammetry, X-ray photoelectron spectroscopy, X-ray diffraction, coupled gas chromatography and mass spectrometry, differential electrochemical mass spectrometry, and scanning electron microscopy) clarifies the misunderstanding of the reaction mechanism. We evidence that the conversion and alloy reaction take place simultaneously inside the bulk of the electrode. Furthermore, we show that a two-layered SEI is formed on the surface. The SEI is decomposed reversibly upon cycling. In the end, we address the issue of the volume expansion and associated capacity fading by incorporating ZnO into a mesoporous carbon network. This approach reduces the capacity fading and yields cells with a specific capacity of above 500 mAh g–1 after 150 cycles.

Section: Introductionmentioning

confidence: 99%

Electrochemical Lithiation/Delithiation of ZnO in 3D-Structured Electrodes: Elucidating the Mechanism and the Solid Electrolyte Interphase Formation

Kreissl

Petit

Oppermann

et al. 2021

“…Functions of various mobile redox-active electrolyte additives used in LOBs are determined by their reduction potentials. − Redox-active molecules having their reduction potentials more negative than that of superoxide formation (O 2 /LiO 2 ) played a role of discharge redox mediator (DRM) to transfer electrons from electrode to oxygen (DRM in Figure a). − 2,5-Di tert -butyl-1,4-benzoquinone ( DBBQ or DB- p -BQ ), a para -quinone derivative, was one of the representative DRMs . DRM molecules were reduced into DRM – on air cathode during discharge.…”

Section: Introductionmentioning

confidence: 99%

“…Resultantly, discharge overpotential was reduced (kinetic gain) and higher capacity was guaranteed (thermodynamic gain). On the other hand, redox-active molecules having their reduction potential more positive than that of superoxide-to-peroxide conversion (LiO 2 /Li 2 O 2 ) were used as charge redox mediators (CRMs) to transfer electrons from discharge product (lithium peroxide) to electrode (CRM in Figure a,d). − …”

Section: Introductionmentioning

confidence: 99%

Shifting Target Reaction from Oxygen Reduction to Superoxide Disproportionation by Tuning Isomeric Configuration of Quinone Derivative as Redox Mediator for Lithium–Oxygen Batteries

Kim

Lee

Jeong

et al. 2022

Quinones having a fully conjugated cyclic dione structure have been used as redox mediators in electrochemistry. 2,5-Ditert-butyl-1,4-benzoquinone (DBBQ or DB-p-BQ) as a para-quinone derivative is one of the representative discharge redox mediators for facilitating the oxygen reduction reaction (ORR) kinetics in lithium−oxygen batteries (LOBs). Herein, we presented that the redox activity of DB-p-BQ for electron mediation was possibly used for facilitating superoxide disproportionation reaction (SODR) by tuning the isomeric configuration of the carbonyl groups of the substituted quinone to change its reduction potentials. First, we expected a molecule having its reduction potential between oxygen/superoxide at 2.75 V versus Li/Li + and superoxide/peroxide at 3.17 V to play a role of the SODR catalyst by transferring an electron from one superoxide (O 2 − ) to another superoxide to generate dioxygen (O 2 ) and peroxide (O 2 2− ). By changing the isomeric configuration from para (DB-p-BQ) to ortho (DB-o-BQ), the reduction potential of the first electron transfer (Q/Q − ) of the ditert-butyl benzoquinone shifted positively to the potential range of the SODR catalyst. The electrocatalytic SODRpromoting functionality of DB-o-BQ kept the reactive superoxide concentration below a harmful level to suppress superoxidetriggered side reaction, improving the cycling durability of LOBs, which was not achieved by the para form. The second electron transfer process (Q − / Q 2− ) of the DB-o-BQ, even if the same process of the para form was not used for facilitating ORR, played a role of mediating electrons between electrode and oxygen like the Q/Q − process of the para form. The ORR-promoting functionality of the ortho form increased the LOB discharge capacity and reduced the ORR overpotential.

“…1,2 Hence, it is a promising battery chemistry for systems where lightweight energy storage is necessary to maximize performance/efficiency, such as long-range electric vehicles and future electric planes including aircrafts. 3 Nevertheless, such batteries still face numerous challenges hindering their commercialization and frequently suffer from poor reversibility and cell life. The cathodic oxygen reduction reaction (ORR) activity can exceed the oxygen evolution reaction (OER) activity, which leads to incomplete reversing of discharge product Li 2 O 2 to lithium metal.…”

Section: Introductionmentioning

confidence: 99%

“…Lithium oxygen batteries can theoretically store ∼11.4 kWh (excluding the weight of oxygen) of energy per kilogram of battery, which is 19 times the specific energy of lithium-ion batteries with a LiCoO 2 cathode (specific energy = ∼600 Wh kg –1 ). , Hence, it is a promising battery chemistry for systems where lightweight energy storage is necessary to maximize performance/efficiency, such as long-range electric vehicles and future electric planes including aircrafts …”

Section: Introductionmentioning

confidence: 99%

The Influence of Porous Co/CeO_1.88-Nitrogen-Doped Carbon Nanorods on the Specific Capacity of Li-O₂ Batteries

Hyun

Kaker

Sivanantham

et al. 2021

Li-O 2 batteries are attracting considerable attention as a promising power source for electric vehicles as they have the highest theoretical energy density among reported rechargeable batteries. However, the low energy density and efficiency of Li-O 2 batteries still act as limiting factors in real cell implementations. This study proposes the cathode structure engineering strategy by tuning the thickness of a catalyst layer to enhance the Li-O 2 battery performance. The construction of the Li-O 2 battery with a thinner porous cathode leads less parasitic reactions at the solid electrolyte interface, maximization of the catalyst utilization, and facile transport of oxygen gas into the cathode. A remarkably high specific capacity of 33,009 mAh g −1 and the extended electrochemical stability for 75 cycles at a 1000 mAh g −1 limited capacity and 100 mA g −1 were achieved when using the porous Co/ CeO 1.88 -nitrogen-doped carbon nanorod cathode. Further, a high discharge capacity of 20,279 mAh g −1 was also achieved at a relatively higher current density of 300 mA g −1 . This work suggests the ideal cathode structure and the feasibility of the Co/CeO 1.88nitrogen-doped carbon nanorod as the cathode material, which can minimize the areal cathode catalyst loading and maximize the gravimetric energy density.