Nature, 8 Feb. 2024, VOL 626, ISSUE 7998
《自然》2024年2月8日，第626卷，7998期
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天文学Astronomy
A recently formed ocean inside Saturn’s moon Mimas
土卫一内部最近形成的海洋
▲ 作者：V. Lainey, N. Rambaux, G. Tobie, N. Cooper, Q. Zhang, B. Noyelles, et al.
▲ 链接：
https://www.nature.com/articles/s41586-023-06975-9
▲ 摘要：
可能孕育海洋的卫星正逐渐成为太阳系中相对常见的物体。这些长寿命海洋的存在通常因内部动力学引起的表面变化而暴露。因此，土卫一将是最不可能找到海洋存在的地方。
根据卡西尼号数据对土卫一轨道运动（特别是土卫一的近日点漂移）的详细分析，研究组表明土卫一坑坑洼洼的冰壳内隐藏着一个全球海洋，深度为20~30千米。偏心阻尼意味着该海洋的年龄可能不到2500万年，而且还在不断进化。
该模型显示，直到最近（不到2~3百万年前）海洋-冰界面的深度才达到不足30千米，时间跨度太短，尚未出现土卫一表面活动的迹象。
▲ Abstract：
Moons potentially harbouring a global ocean are tending to become relatively common objects in the Solar System. The presence of these long-lived global oceans is generally betrayed by surface modification owing to internal dynamics. Hence, Mimas would be the most unlikely place to look for the presence of a global ocean. Here, from detailed analysis of Mimas’s orbital motion based on Cassini data, with a particular focus on Mimas’s periapsis drift, we show that its heavily cratered icy shell hides a global ocean, at a depth of 20–30?kilometres. Eccentricity damping implies that the ocean is likely to be less than 25?million years old and still evolving. Our simulations show that the ocean–ice interface reached a depth of less than 30?kilometres only recently (less than 2–3?million years ago), a time span too short for signs of activity at Mimas’s surface to have appeared.
材料科学Materials Science
Stable blue phosphorescent organic LEDs that use polariton-enhanced Purcell effects
使用极化激元增强的珀塞尔效应来稳定蓝色磷光有机LED
▲ 作者：Haonan Zhao, Claire E. Arneson, Dejiu Fan & Stephen R. Forrest
▲ 链接：
https://www.nature.com/articles/s41586-023-06976-8
▲ 摘要：
磷光有机发光二极管（PHOLEDs）具有高效率、亮度和颜色可调性，适用于显示器和照明应用。然而，克服蓝色PHOLED的短工作寿命仍然是有机电子领域最具挑战性的高值问题之一。其短寿命源于高能、长寿命的蓝色三重态湮灭导致的分子离解。
珀塞尔效应，即微腔中辐射衰减率的增强，可降低三重态密度，从而降低破坏性高能三重态-极化子湮灭（TPA）和三重态-三重态湮灭（TTA）事件的概率。
研究组介绍了蓝色PHOLED中极化子增强的珀塞尔效应。结果发现，等离子-激子极化激元（PEPs）显著增加了珀塞尔效应的强度，在蓝色PHOLED内50 nm厚的发射层（EML）中，平均珀塞尔因子（PF）达到2.4±0.2。与传统PHOLED中的应用相比，青色发光Ir复合物器件的LT90（PHOLED亮度衰减到其初始值90%的时间）提高了5.3倍。
将色度坐标（0.14、0.14）和（0.15、0.20）转换为深蓝色，珀塞尔增强器件与类似的深蓝色PHOLED相比寿命提升了10~14倍，其中一种结构达到了迄今为止报道的最长Ir复合物器件寿命LT90 = 140±20小时。极化激元增强的珀塞尔效应和微腔工程为延长深蓝色PHOLED寿命提供了新的可能性。
▲ Abstract：
Phosphorescent organic light-emitting diodes (PHOLEDs) feature high efficiency, brightness and colour tunability suitable for both display and lighting applications. However, overcoming the short operational lifetime of blue PHOLEDs remains one of the most challenging high-value problems in the field of organic electronics. Their short lifetimes originate from the annihilation of high-energy, long-lived blue triplets that leads to molecular dissociation. The Purcell effect, the enhancement of the radiative decay rate in a microcavity, can reduce the triplet density and, hence, the probability of destructive high-energy triplet–polaron annihilation (TPA) and triplet–triplet annihilation (TTA) events. Here we introduce the polariton-enhanced Purcell effect in blue PHOLEDs. We find that plasmon–exciton polaritons (PEPs) substantially increase the strength of the Purcell effect and achieve an average Purcell factor (PF) of 2.4?±?0.2 over a 50-nm-thick emission layer (EML) in a blue PHOLED. A 5.3-fold improvement in LT90 (the time for the PHOLED luminance to decay to 90% of its initial value) of a cyan-emitting Ir-complex device is achieved compared with its use in a conventional PHOLED. Shifting the chromaticity coordinates to (0.14,?0.14) and (0.15,?0.20) into the deep blue, the Purcell-enhanced devices achieve 10–14 times improvement over similarly deep-blue PHOLEDs, with one structure reaching the longest Ir-complex device lifetime of LT90?=?140?±?20?h reported so far. The polariton-enhanced Purcell effect and microcavity engineering provide new possibilities for extending deep-blue PHOLED lifetimes.
A rechargeable calcium–oxygen battery that operates at room temperature
在室温下运行的可充电钙氧电池
▲ 作者：Lei Ye, Meng Liao, Kun Zhang, Mengting Zheng, Yi Jiang, Xiangran Cheng, et al.
▲ 链接：
https://www.nature.com/articles/s41586-023-06949-x
▲ 摘要：
钙氧（Ca-O2）电池理论上可通过将O2还原为氧化钙化合物（CaOx），以低成本提供高容量。然而，由于CaOx/O2化学通常涉及惰性放电产物，且很少有电解质能够兼顾高度还原性的Ca金属阳极和O2，在室温下运行的可充电Ca-O2电池尚未实现。
研究组报道了一种在室温下可充电700次的Ca-O2电池。该电池依靠高度可逆的双电子氧化还原来形成化学反应性过氧化钙（CaO2）作为放电产物。使用耐用的离子液体基电解质，通过在室温下促进Ca金属阳极中的Ca电镀-剥离和改善空气阴极中的CaO2/O2氧化还原，研究组实现了这种双电子反应。
该研究所提出的Ca-O2电池在空气中很稳定，可制成柔性纤维，编织成纺织电池用于下一代可穿戴系统。
▲ Abstract：
Calcium–oxygen (Ca–O2) batteries can theoretically afford high capacity by the reduction of O2 to calcium oxide compounds (CaOx) at low cost. Yet, a rechargeable Ca–O2 battery that operates at room temperature has not been achieved because the CaOx/O2 chemistry typically involves inert discharge products and few electrolytes can accommodate both a highly reductive Ca metal anode and O2. Here we report a Ca–O2 battery that is rechargeable for 700 cycles at room temperature. Our battery relies on a highly reversible two-electron redox to form chemically reactive calcium peroxide (CaO2) as the discharge product. Using a durable ionic liquid-based electrolyte, this two-electron reaction is enabled by the facilitated Ca plating–stripping in the Ca metal anode at room temperature and improved CaO2/O2 redox in the air cathode. We show the proposed Ca–O2 battery is stable in air and can be made into flexible fibres that are weaved into textile batteries for next-generation wearable systems.
化学Chemistry
Recovery of isolated lithium through discharged state calendar ageing
通过放电状态日历老化恢复死锂
▲ 作者：Wenbo Zhang, Philaphon Sayavong, Xin Xiao, Solomon T. Oyakhire, Sanzeeda Baig Shuchi, Rafael A. Vilá, et al.
▲ 链接：
https://www.nature.com/articles/s41586-023-06992-8
▲ 摘要：
可充电锂金属电池的比能量有望比最先进的可充电锂离子电池提升一倍以上，使锂金属电池成为下一代高能电池技术的首选。然而，与锂离子电池相比，当前锂金属电池存在快速循环衰减的问题，阻碍了其实际应用。容量衰减的一个主要原因是锂与电化学回路断开，形成死锂。日历老化研究表明，在充电状态下静息可促进活性锂与周围电解质的进一步反应。
研究组发现放电状态下的日历老化通过死锂恢复提高了容量保持率，这与众所周知的在充电状态日历老化期间观察到的容量衰减现象形成对比。通过使用混合连续-静息循环方案和滴定气相色谱法观察到Li||Cu半电池和无阳极电池的库仑效率均大于100%，验证了非活性容量恢复。
原位光学装置进一步证实了过量的死锂再活化是容量恢复增加的主要因素。通过放电状态静息来恢复容量的途径此前从未报道，该研究强调了循环策略对锂金属电池性能的显著影响。
▲ Abstract：
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 technology. However, current Li-metal batteries suffer from fast cycle degradation compared with their Li-ion battery counterparts, preventing their practical adoption. A main contributor to capacity degradation is the disconnection of Li from the electrochemical circuit, forming isolated Li. Calendar ageing studies have shown that resting in the charged state promotes further reaction of active Li with the surrounding electrolyte. 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.
地球科学Earth Science
Elevated Southern Hemisphere moisture availability during glacial periods
冰川期南半球水分可用性升高
▲ 作者：Rieneke Weij, J. M. Kale Sniderman, Jon D. Woodhead, John C. Hellstrom, Josephine R. Brown, Russell N. Drysdale, et al.
▲ 链接：
https://www.nature.com/articles/s41586-023-06989-3
▲ 摘要：
晚更新世冰河时期的气候通常被描述为对中低纬度的生态系统施加了水分压力。这一观点主要基于广泛分布的低生物量冰川植被的花粉化石证据，其被解释为气候干燥的迹象。然而，木本植物的生长在低大气CO2下受到抑制，因此了解冰川环境需要开发独立于植被的新型古气候指标。
研究组表明，与预期相反，在过去35万年中，南澳大利亚气候水分可用性的峰值主要局限于冰川期，包括末次冰盛期，而温暖的间冰期相对干燥。通过测量南半球亚热带地区洞穴堆积物生长的时间（如今南半球的年水分平衡主要为负），研究组开发了一个独立于植被的气候水分可用性记录，并延伸贯穿多个冰期-间冰期循环。
研究结果表明，冷湿响应在整个南亚热带地区是一致的，部分原因可能是在寒冷冰川温度下蒸发减少。鉴于南半球亚热带寒冷冰川环境被一致描述为干旱，该研究结果表明，应重新审视该时期是否在进化或生理上阻碍了动物、植物和潜在人类种群的迁徙和扩张。
▲ Abstract：
Late Pleistocene ice-age climates are routinely characterized as having imposed moisture stress on low- to mid-latitude ecosystems. This idea is largely based on fossil pollen evidence for widespread, low-biomass glacial vegetation, interpreted as indicating climatic dryness. However, woody plant growth is inhibited under low atmospheric CO2, so understanding glacial environments requires the development of new palaeoclimate indicators that are independent of vegetation. Here we show that, contrary to expectations, during the past 350?kyr, peaks in southern Australian climatic moisture availability were largely confined to glacial periods, including the Last Glacial Maximum, whereas warm interglacials were relatively dry. By measuring the timing of speleothem growth in the Southern Hemisphere subtropics, which today has a predominantly negative annual moisture balance, we developed a record of climatic moisture availability that is independent of vegetation and extends through multiple glacial–interglacial cycles. Our results demonstrate that a cool-moist response is consistent across the austral subtropics and, in part, may result from reduced evaporation under cool glacial temperatures. Insofar as cold glacial environments in the Southern Hemisphere subtropics have been portrayed as uniformly arid, our findings suggest that their characterization as evolutionary or physiological obstacles to movement and expansion of animal, plant and, potentially, human populations should be reconsidered.
Country-specific net-zero strategies of the pulp and paper industry
纸浆和造纸行业的国别净零战略
▲ 作者：Min Dai, Mingxing Sun, Bin Chen, Lei Shi, Mingzhou Jin, Yi Man, et al.
▲ 链接：
https://www.nature.com/articles/s41586-023-06962-0
▲ 摘要：
全球温室气体排放的大部分归因于纸浆和造纸行业。鉴于各国纸浆和造纸行业间的巨大差异，国别战略对该行业到2050年实现净零排放至关重要。
研究组对30个主要国家1961—2019年国内造纸相关部门的温室气体净排放量（约占同期全球人为温室气体排放量的3.2%）进行了全面的自下而上评估，并通过涵盖关键因素的2160种情景探讨了减缓策略。
研究结果显示，各国纸浆和造纸行业在历史排放演变趋势和结构方面存在实质性差异。到2050年，所有国家都可以实现其纸浆和造纸行业的净零排放，大多数发达国家采取单一措施，大多数发展中国家采取多项措施。
除了提高能源效率和能源系统脱碳外，森林资源丰富的热带发展中国家应优先考虑可持续森林管理，而其他发展中国家应更加重视提高甲烷捕获率和减少循环利用。这些见解对于制定适合每个国家的净零战略以及到2050年实现纸浆和造纸行业的净零排放至关重要。
▲ Abstract：
The pulp and paper industry is an important contributor to global greenhouse gas emissions. Country-specific strategies are essential for the industry to achieve net-zero emissions by 2050, given its vast heterogeneities across countries. Here we develop a comprehensive bottom-up assessment of net greenhouse gas emissions of the domestic paper-related sectors for 30 major countries from 1961 to 2019—about 3.2% of global anthropogenic greenhouse gas emissions from the same period—and explore mitigation strategies through 2,160 scenarios covering key factors. Our results show substantial differences across countries in terms of historical emissions evolution trends and structure. All countries can achieve net-zero emissions for their pulp and paper industry by 2050, with a single measure for most developed countries and several measures for most developing countries. Except for energy-efficiency improvement and energy-system decarbonization, tropical developing countries with abundant forest resources should give priority to sustainable forest management, whereas other developing countries should pay more attention to enhancing methane capture rate and reducing recycling. These insights are crucial for developing net-zero strategies tailored to each country and achieving net-zero emissions by 2050 for the pulp and paper industry.
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