Engineering topics
Publications and source records attributed to Wu, Yiying.
In response to societal developments and the growing demand for high-energy-density battery systems, alkali metal batteries (AMBs) have emerged as promising candidates for next-generation energy storage.
We developed an embedded perovskite-bottom interface reinforcement strategy employing cyano-based emitters with near-unity photoluminescence efficiency, to enhance the device performance and stability.
Developing K-ion conducting solid-state electrolytes (SSEs) plays a critical role in the safe implementation of potassium batteries. In this work, a chalcogenide-based potassium ion SSE is reported, K 3 SbSe 4 , which adopts a trigonal structure at room temperature. Single-crystal structural analysis reveals a trigonal-to-cubic phase transition at the low temperature of 50 °C, which is the lowest among similar compounds and thus provides easy access to the cubic phase. The substitution of barium for potassium in K 3 SbSe 4 leads to the creation of potassium vacancies, expansion of lattice parameters, and a transformation from a trigonal phase to a cubic phase. As a result, the maximum conductivity of K 3−2x Ba x SbSe 4 reaches around 0.1 mS cm −1 at 40 °C for K 2.2 Ba 0.4 SbSe 4 , which is over two orders of magnitude higher than that of undoped K 3 SbSe 4 . This novel SSE is successfully employed in a K–O 2 battery operating at room temperature where a polymer-laminated K 2.2 Ba 0.4 SbSe 4 pellet serves as a separator between the oxygen cathode and the potassium metal anode. Effective protection of the K metal anode against corrosion caused by O 2 is demonstrated.
Abstract The heavy reliance of lithium-ion batteries (LIBs) has caused rising concerns on the sustainability of lithium and transition metal and the ethic issue around mining practice. Developing alternative energy storage technologies beyond lithium has become a prominent slice of global energy research portfolio. The alternative technologies play a vital role in shaping the future landscape of energy storage, from electrified mobility to the efficient utilization of renewable energies and further to large-scale stationary energy storage. Potassium-ion batteries (PIBs) are a promising alternative given its chemical and economic benefits, making a strong competitor to LIBs and sodium-ion batteries for different applications. However, many are unknown regarding potassium storage processes in materials and how it differs from lithium and sodium and understanding of solid–liquid interfacial chemistry is massively insufficient in PIBs. Therefore, there remain outstanding issues to advance the commercial prospects of the PIB technology. This Roadmap highlights the up-to-date scientific and technological advances and the insights into solving challenging issues to accelerate the development of PIBs. We hope this Roadmap aids the wider PIB research community and provides a cross-referencing to other beyond lithium energy storage technologies in the fast-pacing research landscape.
Abstract A battery cathode based on the superoxide/peroxide redox not only inherits the advantage of oxygen (O 2 ) batteries in high capacities and low costs but also overcomes the disadvantages in O 2 storage, electrolyte evaporation, and anode deactivation due to O 2 crossover. Herein, we report an enhanced potassium superoxide (KO 2 )/peroxide (K 2 O 2 ) conversion by adopting a high‐donicity anion additive in the ether‐based electrolyte. Such an anion was synthesized via a “Solvent‐in‐Anion” strategy and validated to enhance the electron donicity of the electrolyte. The use of high‐donicity anion could lead to enhanced KO 2 utilization (≈90.2 %) by retarding electrode passivation and allow the full charging back of K 2 O 2 through the solution‐mediated pathway without electrocatalysts. No apparent cell degradation is observed during the first 120 cycles by controlling the reversible depth‐of‐discharge capacity at 292 mAh g −1 within an O 2 ‐free region. The K−KO 2 cell delivers a high energy efficiency (>84.4 %) and a lifespan of over 1440 hours.
Abstract A battery cathode based on the superoxide/peroxide redox not only inherits the advantage of oxygen (O 2 ) batteries in high capacities and low costs but also overcomes the disadvantages in O 2 storage, electrolyte evaporation, and anode deactivation due to O 2 crossover. Herein, we report an enhanced potassium superoxide (KO 2 )/peroxide (K 2 O 2 ) conversion by adopting a high‐donicity anion additive in the ether‐based electrolyte. Such an anion was synthesized via a “Solvent‐in‐Anion” strategy and validated to enhance the electron donicity of the electrolyte. The use of high‐donicity anion could lead to enhanced KO 2 utilization (≈90.2 %) by retarding electrode passivation and allow the full charging back of K 2 O 2 through the solution‐mediated pathway without electrocatalysts. No apparent cell degradation is observed during the first 120 cycles by controlling the reversible depth‐of‐discharge capacity at 292 mAh g −1 within an O 2 ‐free region. The K−KO 2 cell delivers a high energy efficiency (>84.4 %) and a lifespan of over 1440 hours.
Abstract The formation of a stable solid electrolyte interphase (SEI) at graphite electrode is necessary for lithium‐ion batteries (LIB) to prevent excessive degradation of electrolytes. Until now, the exact organic composition of SEI has not been decisively determined with lithium ethylene mono‐carbonate (LEMC) being one of the debated components. An air‐tight ambient mass spectrometry (MS) platform is developed to directly characterize the air‐sensitive organic components present in SEI. Ionization occurs via a solvent‐free field‐induced process at atmospheric pressure. Our experimental data, based on tandem MS analysis, revealed LEMC to be the major organic component in SEI. This result resolves a long‐standing mystery surrounding the composition of native SEI in LIB, where no trace of the other debated compound, lithium ethylene dicarbonate, was detected. The energetics of fragmentation of LEMC and the corresponding stabilities of various ionic species detected during the air‐tight ambient MS analysis were calculated using density functional theory (DFT). Our findings confirmed favorable protonation energies and suggested the molecular structures for many of the detected species. Solvent (i. e., ethylene carbonate)‐induced stabilization effects observed during the ionization process were also confirmed by DFT. The reported study encourages the routine use of ambient mass spectrometry to characterize both anodic and cathodic electrodes of all battery types as well as to study other air‐sensitive materials in their native state.
Abstract Localized high‐concentration electrolytes (LHCEs) have attracted interest in alkali metal batteries due to the advantages of forming stable solid‐electrolyte interphases (SEIs) on anodes and good chemical/electrochemical stability. Herein, a new degradation mechanism is revealed for ether‐based LHCEs that questions their compatibility with alkali metal anodes (Li, Na, and K). Specifically, the ether solvent reacts with alkali metals to generate solvated electrons (e s − ) that attack hydrofluoroether co‐solvents to form a series of byproducts. The ether solvent essentially acts as a phase‐transfer reagent that continuously transfers electrons from solid‐phase metals into the solution phase, thus inhibiting the formation of stable SEI and leading to continuous alkali metal corrosion. Switching to an ester‐based solvating solvent or intercalation anodes such as graphite or molybdenum disulfide has been shown to avoid such a degradation mechanism due to the absence of e s − .
Abstract Localized high‐concentration electrolytes (LHCEs) have attracted interest in alkali metal batteries due to the advantages of forming stable solid‐electrolyte interphases (SEIs) on anodes and good chemical/electrochemical stability. Herein, a new degradation mechanism is revealed for ether‐based LHCEs that questions their compatibility with alkali metal anodes (Li, Na, and K). Specifically, the ether solvent reacts with alkali metals to generate solvated electrons (e s − ) that attack hydrofluoroether co‐solvents to form a series of byproducts. The ether solvent essentially acts as a phase‐transfer reagent that continuously transfers electrons from solid‐phase metals into the solution phase, thus inhibiting the formation of stable SEI and leading to continuous alkali metal corrosion. Switching to an ester‐based solvating solvent or intercalation anodes such as graphite or molybdenum disulfide has been shown to avoid such a degradation mechanism due to the absence of e s − .
Not provided.
Abstract Solid‐state K‐ion conducting electrolytes are key elements to address the current problems in K secondary batteries. Here, we report a sulfide‐based K‐ion conductor K 3 SbS 4 with a low‐activation energy of 0.27 eV. W‐doped K 3− x Sb 1− x W x S 4 ( x =0.04, 0.06, 0.08, 0.10 and 0.12) compounds were also explored for increasing vacancy concentrations and improving ionic conductivity. Among them, K 2.92 Sb 0.92 W 0.08 S 4 exhibits the highest conductivity of 1.4×10 −4 S cm −1 at 40 °C, which is among the best reported potassium‐ion conductors at ambient temperature. In addition, K 2.92 Sb 0.92 W 0.08 S 4 is electrochemically stable with long‐chained potassium polysulfide of K 2 S x . A room‐temperature solid potassium–sulfur (K−S) battery system has therefore been successfully demonstrated, which is the first K−S battery prototype using non‐commercial inorganic‐based electrolyte to block the polysulfide shuttle.
Abstract Solid‐state K‐ion conducting electrolytes are key elements to address the current problems in K secondary batteries. Here, we report a sulfide‐based K‐ion conductor K 3 SbS 4 with a low‐activation energy of 0.27 eV. W‐doped K 3− x Sb 1− x W x S 4 ( x =0.04, 0.06, 0.08, 0.10 and 0.12) compounds were also explored for increasing vacancy concentrations and improving ionic conductivity. Among them, K 2.92 Sb 0.92 W 0.08 S 4 exhibits the highest conductivity of 1.4×10 −4 S cm −1 at 40 °C, which is among the best reported potassium‐ion conductors at ambient temperature. In addition, K 2.92 Sb 0.92 W 0.08 S 4 is electrochemically stable with long‐chained potassium polysulfide of K 2 S x . A room‐temperature solid potassium–sulfur (K−S) battery system has therefore been successfully demonstrated, which is the first K−S battery prototype using non‐commercial inorganic‐based electrolyte to block the polysulfide shuttle.