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The mineralization dynamics of calcium carbonate is investigated under highly supersaturated conditions using graphene liquid cell transmission electron microscopy. We demonstrate that the minerali...

As it governs the overall performance of lithium-ion batteries, understanding the reaction pathway of lithiation is highly desired. For Co3O4 nanoparticles as anode material, here, we report an initial conversion reaction pathway during lithiation. Using graphene liquid cell electron microscopy (GLC-EM), we reveal a CoO phase of the initial conversion product as well as morphological dynamics during Co3O4 lithiation. In accordance with the in situ TEM observation, we confirmed that the Co3O4 to CoO conversion is a thermodynamically favorable process by calculating the theoretical average voltage based on density functional theory. Our observation will provide a useful insight into the oxide electrode that undergoes conversion reaction.

The conversion reaction is important in lithium-ion batteries because it governs the overall battery performance, such as initial Coulombic efficiency, capacity retention, and rate capability. Here, we have demonstrated in situ observation of the complete conversion reaction and agglomeration of nanoparticles (NPs) upon lithiation by using graphene liquid cell transmission electron microscopy. The observation reveals that the Sn NPs are nucleated from the surface of SnO2, followed by merging with each other. We demonstrate that the agglomeration has a stepwise process, including rotation of a NP, formation of necks, and subsequent merging of individual NPs.

The stress inevitably imposed during electrochemical reactions is expected to fundamentally affect the electrochemistry, phase behavior and morphology of electrodes in service. Here, we show a strong stress-composition coupling in lithium binary alloys during the lithiation of tin-tin oxide core-shell nanoparticles. Using in situ graphene liquid cell electron microscopy imaging, we visualise the generation of a non-uniform composition field in the nanoparticles during lithiation. Stress models based on density functional theory calculations show that the composition gradient is proportional to the applied stress. Based on this coupling, we demonstrate that we can directionally control the lithium distribution by applying different stresses to lithium alloy materials. Our results provide insights into stress-lithium electrochemistry coupling at the nanoscale and suggest potential applications of lithium alloy nanoparticles., Electrochemical reactions can generate stresses that detrimentally affect battery electrodes. Here, the authors directly image the lithiation of core-shell tin-based nanoparticles and show that lithium can be redistributed by applying stress and change the nanoparticle composition.

In article number 1900264, Jong Min Yuk and co‐workers visualize four types of semi‐coherent boundaries formed during sodiation in copper sulfide utilizing high‐resolution transmission electron microscopy. The semi‐coherent boundaries do not only act as mechanical pillars for pulverization‐tolerance, but also provide additional sodium transport paths for capacity recovery. The novel sodiation mechanism enables exceptionally stable sodium storage in copper sulfide.

Finding suitable electrode materials is one of the challenges for the commercialization of a sodium ion battery due to its pulverization accompanied by high volume expansion upon sodiation. Here, copper sulfide is suggested as a superior electrode material with high capacity, high rate, and long‐term cyclability owing to its unique conversion reaction mechanism that is pulverization‐tolerant and thus induces the capacity recovery. Such a desirable consequence comes from the combined effect among formation of stable grain boundaries, semi‐coherent boundaries, and solid‐electrolyte interphase layers. The characteristics enable high cyclic stability of a copper sulfide electrode without any need of size and morphological optimization. This work provides a key finding on high‐performance conversion reaction based electrode materials for sodium ion batteries.

We trace Sn nanoparticles (NPs) produced from SnO2 nanotubes (NTs) during lithiation initialized by high energy e-beam irradiation. The growth dynamics of Sn NPs is visualized in liquid electrolytes by graphene liquid cell transmission electron microscopy. The observation reveals that Sn NPs grow on the surface of SnO2 NTs via coalescence and the final shape of agglomerated NPs is governed by surface energy of the Sn NPs and the interfacial energy between Sn NPs and SnO2 NTs. Our result will likely benefit more rational material design of the ideal interface for facile ion insertion.

Sodium ion batteries have been considered a promising alternative to lithium ion batteries for large-scale energy storage owing to their low cost and high natural abundance. However, the commercialization of this device is hindered by the lack of suitable anodes with an optimized morphology that ensure high capacity and cycling stability of a battery. Here, we not only demonstrate that copper sulfide nanoplates exhibit close-to-theoretical capacity (~560 mAh g–1) and long-term cyclability, but also reveal that their sodiation follows a non-equilibrium reaction route, which involves successive crystallographic tuning. By employing in situ transmission electron microscopy, we examine the atomic structures of four distinct sodiation phases of copper sulfide nanoplates including a metastable phase and discover that the discharge profile of copper sulfide directly reflects the observed phase evolutions. Our work provides detailed insight into the sodiation process of the high-performance intercalation–conversion anode material., Copper sulfide allows for high-performance sodium ion storage, yet its sodiation mechanism is poorly understood. Here, the authors examine the atomic structures of sodiated phases via in situ transmission electron microscopy, showing a non-equilibrium reaction pathway.

연구배경 : 호흡곤란은 호흡기질환 환자의 가장 흔한 주소이나 이를 감지하는 정확한 기전은 아직 잘 알려져 있지 않다. 폐질환에서 호흡곤란의 심한 정도와 치료에 대한 반응을 측정하는 데 있어 객관적인 폐기능을 이용하여 왔으나 호흡곤란은 폐 환기능 뿐 아니라 심장, 폐질환, 심인적 요인 등을 반영한 복합적인 증상이므로 주관적으로 측정하는 호흡곤란지수(dyspnea index)를 사용하여 이러한 증상의 정도를 양적으로 측정하는 것도 유용할 것으로 생각된다. 방법 : 증상이 기관지천식 환자를 대상으로 Visual Analogue Scale(VAS) 및 Borg Scale Dyspnea Index (BSDI)와 Spirometry를 검사전 휴식상태, methacholine 유발검사에서 양성을 나타내었을 때, 기관지확장제 투여후 각각 측정하였다. 결과 : 1) 기저상태와 Methacholine 및 기관지확장제 투여후 시행한 폐기능검사 결과와 VAS 및 BSDI 간 상관관계는 없었다. 2) FEV1, FVC 및 MMFR 변화량과 VAS 및 BSDI 변화량 간에도 상관관계는 없었다. 3) 천식의 증상호소가 경미한 환자군이 증상호소가 심한 환자군 보다 methacholine 및 기관지확장제 투여 후의 VAS 및 BSDI의 변화가 더 컸다. 4) 호흡곤란지수중 VAS이 BSDI 보다 조금 큰 수치 및 변화량을 보였으며 두 지수 간의 상관관계를 볼 수 있었다(R=0.82). 결론 : 기관지천식 환자에서 기저상태 및 Methacholine 유발검사시에 객관적인 폐기능 검사 수치의 유의한 차이가 없음에도 불구하고 주관적인 호흡곤란지수는 변화하는 경향을 보였으며, 이는 경중 천식군에서 더욱 뚜렷하였다. 호흡곤란지수는 환자 간의 비교척도로는 사용될 수 없으나 한 환자에서 경과관찰이나 치료효과를 판정하는데에 spirometry와 함께 중요한 지표가 될 것으로 생각된다. 【Background: Despite dyspnea is a predominant complaint of patients with respiratory disease, the mechanisms contributing to the sensation of breathlessness are poorly understood. Traditionally, physicians have measured objective pulmonary function to assess severity of dyspnea. But it will be also useful to measure subjective dyspnea index because dyspnea probably depends on a complex interplay of mechanical, experimental, emotional and other factors. Method: We measured breathlessness at rest, after Methacholine challenge and then bronchodilator inhalation using a Visual Analogue Scale (VAS) and Borg Scale Dyspnea Index (BSDI) in stable asthmatic patients. Spirometry was performed concomittently. Results: There was no correlation between dyspnea index and FEV1. There was also no correlation between the change in dyspnea index and change in FEV1. The change in dyspnea index after methacholine and bronchodilator was greater in clinically mild asthmatic patients than clinically severe symptomatic group. Conclusion: In asthmatic patients, there was a wide variation in sensory response for any given FEV1, and the change in perception of dyspnea was greater in those with clinically mild symptoms. The measurement of dyspnea index may yield information complementary to that obtained by spirometry.】