Hybrid perovskite photovoltaics combine high performance with the ease of solution processing. However, to date, a poor understanding of morphology formation in coated perovskite precursor thin films casts doubt on the feasibility of scaling-up laboratory-scale solution processes. Oblique slot jet drying is a widely used scalable method to induce fast crystallization in perovskite thin films, but deep knowledge and explicit guidance on how to control this dynamic method are missing. In response, we present a quantitative model of the drying dynamics under oblique slot jets. Using this model, we identify a simple criterion for successful scaling of perovskite solution printing and predict coating windows in terms of air velocity and web speed for reproducible fabrication of perovskite solar cells of ∼15% in power conversion efficiencyin direct correlation with the morphology of fabricated thin films. These findings are a corner stone toward scaling perovskite fabrication from simple principles instead of trial and error optimization.
widely used in consumer electronics due to the advantages of rechargeability and high energy density. [4][5][6] Commercial LIBs are usually fabricated in fixed geometry such as cylinder, coin, and pouch with scrolled or layered planar sheets for each component. [7] Nevertheless, LIBs with customizable geometry are desired for specialized applications such as wearable electronics [8,9] and on-device power systems [10,11] for automobile and aerospace vehicles, For example, LIBs can be made into a watchband to power an electronic watch, [12] which eliminates the installation and replacement of coin cell. To meet such demands, irregular, customizable LIBs in arbitrary geometry on 3D structures along with the packaging, integrating, and manufacturing approaches need to be developed. So far, the most effective solution to fabricate freeform LIBs is additive manufacturing (AM, popularly known as 3D printing). [13][14][15][16] The on-demand and layer-by-layer manufacturing method has provided the flexibility to accommodate customizable designs of 3D LIBs.Electrodes are the most essential components of LIBs. Currently reported AM processes for electrodes are mostly based on extrusion printing, [17][18][19][20][21][22][23][24] with a few reports on other ink-based printing methods including inkjet printing [25] and aerosol printing. [10] In extrusion printing, active material laden inks are directly deposited and powered by ultra-high air pressure. The materials are extruded into semi-solidified and self-supportive filaments owing to the shear-thinning characteristics of the highly viscous inks. Main advantage of AM processes is the capability of printing electrodes in arbitrary geometry. For example, Lacey et al. and Wang et al. demonstrated 3D printing of mesh and lattice structured electrodes, which effectively introduced macroporosity and facilitated the transportation of lithium-ions under high charging/discharging rate. [18,23] The flexibility in printed geometry also enables the fabrication of electrodes with high aspect ratio and high areal capacity, which are usually not processable by conventional slurry-casting method. Sun et al. first printed high aspect ratio, multilayer, interdigitated electrodes for micro-LIBs with high energy density and power density. [21] Despite these advantages, in extrusion-printing, composition and rheological behaviors of inks are demanding due to the requirements in clogging prevention, substrate bonding and shape maintenance. [19,20] Alternatively, aerosol printing Lithium-ion batteries (LIBs) are widely used in consumer electronics due to their rechargeability and high energy density. Commercial LIBs are fabricated in fixed geometries such as cylinder, coin, and pouch. However, for specialized applications such as wearable electronics and on-device power systems, customizable LIBs with arbitrary geometry on threedimensional (3D) structures need to be developed. For this purpose, aerosol printing is uniquely suitable due to its flexible working distance, allowing deposition on nonp...
Lithium (Li) deposition behavior plays an important role in dendrite formation and the subsequent performance of lithium metal batteries. This work reveals the impact of the lithiophilic sites of lithium-alloy on the Li plating process via the first-principles calculations. We find that the Li deposition mechanisms on the Li metal and Li22Sn5 surface are different due to the lithiophilic sites. We first propose that Li plating on the Li metal surface goes through the “adsorption–reduction–desorption–heterogeneous nucleation–cluster drop” process, while it undergoes the “adsorption–reduction–growth” process on the Li22Sn5 surface. The lower adsorption energy contributes to the easy adsorption of Li on the lithiophilic sites of the Li22Sn5 surface. The lower Li reduction energy on the Li metal surface indicates that it is easy for Li to be reduced on the Li metal surface, attributed to its higher Fermi energy level. Furthermore, the faster Li diffusion on the Li22Sn5 surface results in smooth Li deposition, which is based on a “two-Li synergy diffusion” mechanism. However, Li diffuses more slowly on the Li metal surface than on the Li22Sn5 surface due to the “single Li diffusion” mechanism. This work provides a fundamental understanding on the impact of lithiophilic sites of Li alloy on the Li plating process and points out that the future design of 3D Li-alloy substrates decorated with multilithiophilic sites can prevent dendrite formation on the lithium-alloy substrate by guiding uniform Li deposition.
The degree of metal dissolution of cathode materials is a critical parameter in determining the performance of lithium-ion batteries (LIBs). Ultra-thin coated cathode particles, fabricated via atomic layer deposition (ALD), exhibit superior battery performance over that of bare particles. Therefore, it is generally believed that a coating layer protects the particles from metal dissolution of active materials, which is a critical cathode degradation mechanism. However, it is observed that ultra-thin CeO 2 coating intensified the Mn dissolution of LiMn 2 O 4 (LMO) during cycling of LIBs, whereas ultra-thin Al 2 O 3 coating tended to inhibit Mn dissolution. A detailed density functional theory (DFT) study is carried out to explain these experimental observations by analyzing interaction of Mn atoms with neighboring electrode atoms in terms of energetic and structural aspect. All atomic and electronic analyses are consistent with the experimental observations. Several common materials are investigated as possible ALD coatings for LIBs to provide general insight, and it is found that Mn dissolution can be suppressed or accelerated depending on the material selection. This is the first report finding that depending on the coating material, metal dissolution can be accelerated, providing new insights into the impact of ALD coating materials on metal dissolution in cathode materials. potential, superior capacity, a long life cycle, and a sufficiently broad range of working temperatures. Although metal oxide cathodes satisfy the criteria, they suffer from an inevitable metal dissolution degradation process. In the dissolution degradation process, transition metal ions dissolve from cathode active materials and can deposit onto the anode, causing severe cell aging and irreversible side reactions that reduce performance. [1,2] For high performance cathode materials such as LiNi x Mn y Co z O 2 (NMC, x + y + z = 1), LiNi 0.5 Mn 1.5 O 4 (LNMO), and LiMn 2 O 4 (LMO), metal dissolution (Ni, Co, Mn, etc.) is severe, and, furthermore, it was found that in such cathode materials, which are composed of two or more transition metals, there is no preferential dissolution among the constituent metals. [3] To study the metal dissolution phenomena, manganese is an excellent candidate for intensive study of the fundamental interfacial processes and side reactions at cathode surfaces because of its low toxicity, low cost, and the high natural abundance of Mn, [4][5][6][7][8][9][10][11][12] which allows it to be used in several promising cathode materials, such as NMC, LNMO, and LMO. It has been published that Mn dissolution accounts for 23% and 34% of overall capacity degradation at room temperature and at 55°C [13] in LMO, respectively. The major reason for LMO degradation, [14][15][16][17][18] as well as for other metal oxide cathode materials, [3,[19][20][21] has been identified as structural changes in the material due to phase transformations, alternation of intrinsic properties (such as electronic and ionic conductivity), dissoluti...
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