RESUMEN
Rechargeable Li-metal batteries have the potential to more than double the specific energy of the state-of-the-art rechargeable Li-ion batteries, making Li-metal batteries a prime candidate for next-generation high-energy battery technology1-3. However, current Li-metal batteries suffer from fast cycle degradation compared with their Li-ion battery counterparts2,3, preventing their practical adoption. A main contributor to capacity degradation is the disconnection of Li from the electrochemical circuit, forming isolated Li4-8. Calendar ageing studies have shown that resting in the charged state promotes further reaction of active Li with the surrounding electrolyte9-12. Here we discover that calendar ageing in the discharged state improves capacity retention through isolated Li recovery, which is in contrast with the well-known phenomenon of capacity degradation observed during the charged state calendar ageing. Inactive capacity recovery is verified through observation of Coulombic efficiency greater than 100% on both Li||Cu half-cells and anode-free cells using a hybrid continuous-resting cycling protocol and with titration gas chromatography. An operando optical setup further confirms excess isolated Li reactivation as the predominant contributor to the increased capacity recovery. These insights into a previously unknown pathway for capacity recovery through discharged state resting emphasize the marked impact of cycling strategies on Li-metal battery performance.
RESUMEN
At >95% Coulombic efficiencies, most of the capacity loss for Li metal anodes (LMAs) is through the formation and growth of the solid electrolyte interphase (SEI). However, the mechanism through which this happens remains unclear. One property of the SEI that directly affects its formation and growth is the SEI's solubility in the electrolyte. Here, we systematically quantify and compare the solubility of SEIs derived from ether-based electrolytes optimized for LMAs using in-operando electrochemical quartz crystal microbalance (EQCM). A correlation among solubility, passivity, and cyclability established in this work reveals that SEI dissolution is a major contributor to the differences in passivity and electrochemical performance among battery electrolytes. Together with our EQCM, X-ray photoelectron spectroscopy (XPS), and nuclear magnetic resonance (NMR) spectroscopy results, we show that solubility depends on not only the SEI's composition but also the properties of the electrolyte. This provides a crucial piece of information that could help minimize capacity loss due to SEI formation and growth during battery cycling and aging.
RESUMEN
Despite the fact that much work has been dedicated to finding the ideal additive for composite solid electrolytes (CSEs) for lithium-based solid-state batteries, little is known about the properties of a CSE that enable stable cycling with a lithium metal anode. In this work, we use three CSEs based on lithium nitride (Li3N), a fast lithium-ion conductor, and lithium hydroxide (LiOH) to investigate the properties and interfacial interactions that impact the cyclability of CSEs. We present a method for stabilizing Li3N with a shell of LiOH, and we incorporate Li3N, core-shell particles, and LiOH into CSEs using polyethylene oxide (PEO) and lithium bis(trifluoromethanesulfonyl)imide. Through improved interfacial chemistry, CSEs with core-shell particles have superior electrochemical cycling performance compared to those with unprotected Li3N in symmetric Li-Li cells. This CSE features a high ionic conductivity of 0.66 mS cm-1 at 60 °C, a high critical current density of 1.2 mA cm-2, and a wide voltage window of 0-5.1 V. Full cells with the core-shell CSE and lithium iron phosphate cathodes exhibit stable cycling and high reversible specific capacities in cells as high as 2.5 mAh cm-2. We report that the improved ionic conductivity and amorphous PEO content have a limited effect on the solid-state electrolyte performance, while improving the electrolyte-Li metal anode interface is key to cycling longevity.
RESUMEN
Background: Existing literature emphasised the spiritual value of grandparents in a child's faith nurture, but this was not reflected in contemporary understandings or practices of the Christian community. Purpose: The discourses surrounding the perceptions and practices of grandparents themselves, the local church and wider Christian society were investigated; uncovering the dynamics of cross-generational relationships and interactions with a child's spiritual journey. Methods: Data was gathered from Christian media, resourcing organisations, denominational websites and focus group interviews with grandparents and church representatives, to reveal the discourses conveyed by individuals, institutions and the wider Christian community. Critical discourse analysis was used to investigate perceptions and implications. Results: Grandparents unanimously reported collective worth and purpose in their grandparent-grandchild relations. However, church representatives observed barriers and tensions regarding their involvement in faith nurture, citing a culture of privacy surrounding faith. Denominational websites and Christian media indicated that grandparents were not integral to church strategies, being rarely mentioned, resourced or empowered. The dominant discourses were of grandparents being passive agents with background involvement. Resourcing primarily conveyed romanticism and nostalgia rather than addressing contemporary family life. For some, these relationships facilitated discussions about faith, whilst others said their family's faith identity was unspoken. The grandparents were primarily motivated personally and independently of external bodies, often adopting a 'trial and error' mentality, suggesting a highly individual rather than collective approach to faith nurture of grandchildren. The local church rarely championed grandparents in this role, leading to grandparents being passive and feeling excluded. Many lacked confidence and were disengaged with faith nurture. Conclusions and Implications: The value of grandparents needs better communicating, moving them from being minor contributors at the periphery of the team to being more actively and intentionally involved. This requires enhanced understanding at institutional and societal levels of grandparents' role, and improvement in the functionality and efficacy of interactions between grandparents and their grandchildren. Redressing of the power dynamics at play within congregations and society is required to bring grandparents more equally into the equation. A paradigm shift is required at all levels to equip, empower and include grandparents more fully. This would lead to improved Christian faith transmission.
