Energy Storage Materials最新文献

The development of nonflammable electrolytes is critical for breaking the trade-off between the safety and energy density in Li-ion batteries (LIBs). Here, a rational design strategy of temperature-responsive nonflammable electrolytes (TRNEs) is proposed which are capable to prevent the heat accumulation and extinguish the fire efficiently during thermal runaway. Compared to the conventional phosphate- or halogen-based flame retardants, the TRNE based on low-cost and multifunctional methylurea (MU) was demonstrated with the lowest volatility (11.6 % weight loss) below 250 °C, and the highest efficacy to extinguish the fire at >210.4 °C through heat absorption, inert gases generation and char layer formation. In addition, the developed MU-based TRNEs enable higher stability and rate capability of LIBs compared to various nonflammable electrolytes. A Li||LiFePO₄ (LFP) cell employing MU-based TRNE achieved higher stability (94.9 % capacity retention for 1500 cycles) than commercial electrolyte. A Ni-rich Li||LiNi_0.8Mn_0.1Co_0.1O₂ (NMC811) system was demonstrated with superior rate capability and high stability for 700 cycles (2.72 months) with the capacity retention of 89.9 %. Combining low cost and volatility, as well as high stability, rate capability and fire extinguishing efficacy, we demonstrate a promising design strategy to improve the battery safety for high-energy-density LIBs.

The effective diffusivity of ionic species in multiphase materials is critical for the design and function of composite materials for electrochemical energy storage. In practice, effective diffusivity depends sensitively not only on the intrinsic diffusivities of constituting materials but also on their topological arrangement; nevertheless, these coupled contributions are oversimplified in most analytical models. Here, we combine atomistically informed mesoscale modeling and machine learning (ML) analysis to unravel how such features affect effective diffusivity in two-phase composites. Using the Li₇La₃Zr₂O₁₂-LiCoO₂ composite solid-state battery cathode as a model system, we compute effective diffusivity for 600 distinct dense polycrystalline microstructures with different topological configurations of grains, grain boundaries, and heterointerfaces. We verify that in addition to atomic-scale variabilities, microstructural feature diversity can significantly impact effective transport properties. Across the ensemble of test microstructures, this often results in bimodal distributions of effective diffusivity that encompass two qualitatively distinct operating mechanisms, which we identify via flux analysis. An ML approach reveals that the most critical determining factors for effective diffusivity are the connectivity of bulk phases and their heterointerfaces. The role of ionic mobility at the heterointerfaces is also discussed. These insights highlight the combined importance of microstructure and interface engineering in tuning the transport properties of ionic species in composite materials. Our framework can also be extended for understanding generic microstructure-property relationships in other complex multiphase materials.

Controllable assembly of polyoxometalates (POMs) in confined nanochannels is crucial to understand the host-guest structures and tailor the emerging properties for applications. Here, we report the encapsulation of polyoxometalates inside single-walled carbon nanotubes (SWNTs) for target catalytic regulation. Theoretical modeling predicts the confined polyoxomolybdates are able to induce biaxial tensile strains of SWNTs for more stable interaction with iron phthalocyanine (FePc) and tailor the charge distribution and coordination environment of targetable FeN₄ sites, leading to improved catalytic activity toward oxygen reduction reaction (ORR). The polyoxomolybdates are confined in the SWNTs via redox-driven encapsulation mechanism with a POM encapsulation efficiency of about 21 %. The constructed FePc/SWNT@POM molecule catalyst exhibits a high half-wave potential of 0.90 V, excellent stability and methanol tolerance in alkaline medium. The zinc-air battery also presents prominent charge-discharge ability and long-term durability over 400 h with a peak power density of 190.8 mW cm^–2.

Na₂FePO₄F has emerged as a promising cathode for large-scale electrochemical energy storage, primarily due to its abundance of raw materials and distinctive two-dimensional ion channels. Counterintuitively, pristine Na₂FePO₄F lacks the long-term stability typically seen in polyanionic cathodes, which severely impedes its practical application. Traditionally, the origin of this problem has been only phenomenologically attributed to the poor intrinsic electronic conductivity and structural instability of Na₂FePO₄F. Here, we identify that rapid capacity fading of Na₂FePO₄F is closely related to the β-to-α phase transition during the long cycling process. Furthermore, we develop a practical high-entropy doping strategy and the corresponding microstructure engineering to mitigate the impact of the phase transition on the crystal structure, thereby increasing the capacity retention from 56 % to 94 % over 400 cycles at 0.5C in coin cell, and attain almost 100 % capacity retention after 300 cycles at 0.1C in pouch cell. Overall, this work unveils the mechanism of rapid capacity decay in Na₂FePO₄F and lays the groundwork for the rational design of durable polyanionic electrodes.

Cation-disordered rock-salts (DRX) emerge as an intriguing class of high-capacity cathode materials, garnering significant attention in the development of advanced energy-storage systems. Fluorination strategies have been raised to regulate redox and structure for better DRX electrochemical performance. However, research on the interfacial processes during fluorinated DRX cycling remains limited. Here, we evaluate a highly fluorinated DRX, Li₂Mn_2/3Nb_1/3O₂F (LMNOF), in different electrolytes to correlate its cycling performance with distinct interfacial evolutions. During cycling in the carbonate-based electrolyte, a thick Mn-containing CEI forms on the LMNOF surface, leading to gradual capacity decay. Intriguingly, the addition of fluoroethylene carbonate (FEC) would bring about surface oxygen loss, Mn-ion dissolution and formation of a fluorinated surface layer by reacting with the LMNOF surface, which critically deteriorate the cycling performance. In comparison, the ether-based electrolyte is compatible with the LMNOF surface, resulting in a more favorable cycling stability. This work sheds light on the interfacial deterioration mechanism of LMNOF cathode in traditional carbonate-based electrolyte, emphasizing the importance of using advanced non-reactive electrolytes to enhance DRX performance.

Conventional polymer electrolytes suffer from low ionic conductivity, poor interface compatibility, low mechanical strength and certain flammability. Herein, a rigid-flexible synergistic ultrastrong nonflammable polymer electrolyte (LiNO₃-PPT@PI) regulated by LiNO₃ is developed, which consists of rigid polyimide (PI) fiber skeleton and flexible poly pentaerythritol tetraacrylate (PPT) plasticized with LiNO₃/triethyl phosphate (TEP)/fluoroethylene carbonate (FEC). PI fiber skeleton enhances tensile strength of LiNO₃-PPT@PI to 21.8 MPa. TEP effectively enhances ionic conductivity to 7.57 × 10⁻⁴ S cm⁻¹ at 30 °C and improves flame retardancy. LiNO₃ is creatively utilized as the only lithium salt for LiNO₃-PPT@PI to construct Li₃N-rich solid electrolyte interphases (SEIs) and promote FEC to form LiF-rich SEIs/cathode-electrolyte interphases (CEIs) to improve interface stability, thereby enabling high-efficiency, long-term and dendrite-free cycling of LiFePO₄ (LFP)||Li cells and LiNi_0.8Mn_0.1Co_0.1O₂ (NCM811)||Li cells, which is superior to the LiPF₆-based polymer electrolytes. LFP||Li cells with LiNO₃-PPT@PI exhibit excellent cycle performance over 650 cycles with 81.8 % capacity retention. This work presents a promising design strategy of safe and efficient polymer electrolytes for Li metal batteries.

The electrochemically inert phase (EIP) within the electrode is formed by the combination of carbon black and binder, characterized by a highly heterogeneous spatial distribution and structural morphology. This heterogeneity impairs electrode performance under varying discharge rates and temperatures. In this study, X-ray computed tomography is employed to image the original electrode. The resulting grayscale images are digitally processed to reveal the two-dimensional (2D) and three-dimensional (3D) features of the EIP morphology, thereby providing a design window to understand the influence of EIP morphology. The physical structure characterization indicates that, compared to bulk-like EIP (B-EIP), film-like EIP (F-EIP) tends to cover the active surface of the active material (AM), exacerbating the heterogeneity of the lithiation reactions within the electrode. The reduction in the AM active surface area correlates the state of lithiation (SOL) of particles with their active specific surface area (α_a). At low temperatures, the temperature sensitivity of electrodes intensifies the risk of α_a loss, promoting heterogeneous reaction transfer between particles. The Biot number (Bi) is used to evaluate the competing mechanisms between interfacial reactions and bulk diffusion within particles. In electrodes with a high EIP content, the reaction rate at the particle/electrolyte interface is accelerated, causing particle performance to be dominated by interfacial reactions. Finally, the electrochemistry and heat generation from the particle-level to the electrode-level in thicker electrodes are examined. It demonstrates that ion diffusion in the pore controls interfacial reactions and heat transport behavior. Aggregated high-flux reactions and localized hot spots exacerbate the heterogeneous degradation and side reactions within the electrode.

Lithium-sulfur (Li-S) batteries involve complex solid-liquid-solid phase transformations during both discharging and charging processes, where cathode materials, formulation, and structure play a crucial role. Here, a design of experiments (DoE) methodology and an empirical model are developed to systematically explore the interactions and trade-offs among cathode factors and process variables, and to obtain generalizable effects estimates for the multivariate system. Compared to the conventional one-factor-at-a-time (OFAT) approach, this work demonstrates advantages in both efficiency and accuracy by allowing the data to guide future research and decisions. An optimized cathode formulation and processing parameters are predicted and validated experimentally, achieving over 1000 mAh g⁻¹ in discharge capacity and improved cycling under practical lean electrolyte (4 µL mg⁻¹ S) and high S-loading cathodes (>4 mg cm⁻²) conditions. The optimized cathode was scaled up and assembled into Li-S pouch cells, achieving 316 Wh kg⁻¹ in cell-level energy, proving that the comprehensive and rigorous framework for optimizing complex systems with DoE leads to improved performance in a practical pouch cell system.

Flexible Micro-supercapacitors (FMSCs) are revolutionizing smart wearable and implantable devices with their high energy density, superior power density, and exceptional mechanical flexibility. These properties make FMSCs ideal for dynamic, contoured surfaces of wearables and the limited spaces in implants, enhancing design, comfort, and user experience. As these devices evolve, incorporating advanced biosensors, communication technologies, and sophisticated processors, the demand for compact, potent energy storage solutions grows. FMSCs address this need by providing efficient energy storage and delivery, significantly extending operational times. Their rapid charging and discharging capabilities are especially beneficial in healthcare applications, where timely data acquisition and transmission are crucial for effective patient monitoring and intervention. Advances in material science, fabrication techniques, and integration methods continuously improve FMSC performance, broadening their applications and ensuring they remain at the technology forefront. This review explores the current state of FMSC research, focusing on recent advancements, identifying ongoing challenges, and examining potential future directions. It underscores the critical role of FMSCs in enhancing the functionality and autonomy of contemporary and future portable and wearable electronics, paving the way for seamless electronic integration into daily life.