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首页> 外文期刊>Chemistry: A European journal >Facile Synthesis of Transition-Metal Oxide Nanocrystals Embedded in Hollow Carbon Microspheres for High-Rate Lithium-Ion-Battery Anodes
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Facile Synthesis of Transition-Metal Oxide Nanocrystals Embedded in Hollow Carbon Microspheres for High-Rate Lithium-Ion-Battery Anodes

机译：轻松合成空心金属微球中嵌入的过渡金属氧化物纳米晶，用于高速率锂离子电池阳极

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Lithium-ion batteries, as the dominant type of energystorage device for portable electronics and electric/hybrid vehicles, have been attracting considerable attention in scientific and industrial communities.~([1]) The ever-growing market demand for their high electromotive force, high energy density, and high cyclability has stimulated numerous research efforts aimed at the development of new high-performance electrode materials for Li-ion batteries.~([2, 3]) Although the performance of Li-ion batteries continues to improve, their energy density, cycle life, and rate capability remain insufficient for applications in consumer electronics, transport, and large-scale renewable-energy storage.~([4-6]) Recently, nanosizing has been widely applied in the design of battery electrode materials, because it can enhance the storage capacity and rate capability.~([1, 7, 8]) However, the disadvantage of nanosized materials is that they cannot be packed as densely on the current collector as micrometersized materials; this fact means that electrodes made of nanosized materials have a high porosity, resulting in a decrease in the cell capacity.~([9]) Therefore, the best way to improve both the rate capability and electrode density would be to use micrometer-sized particles that consist of aggregated nanoparticles. However, the disadvantage of this arrangement is that the primary particles located around the center of a nanoaggregate exhibit a large electric resistance, because these particles are not connected with the conducting agent, thus resulting in a high overpotential during high-rate charging and discharging.~([9]) To overcome this disadvantage, we hypothesized that the primary electrode nanoparticles could be self-assembled and fully embedded into a conductive carbon matrix. This constraint necessitates use of microsized particles to yield a high volumetric energy density and reliable battery performance. Even further improvement can be achieved with these microsized electrode materials by introducing a hollow core (e.g., constructing hollow spheres with these tiny nanoparticles).~([10-16]) On the other hand, an effective route to improve the electronic electrical conductivity is the addition or coating of conductive secondary phases, such as conductive carbons or RuO_2.~([9, 17-20]) Consequently, a reasonable combination of these two separate microstructure characteristics into a single intact electrode particle, specifically, constructing conductive secondaryphase- coated hollow electrode particles composed of nanoparticles, is an attractive route to enhance the electrochemical performance. Based on these ideas, uniform hollow carbon microspheres embedded with fully encapsulated tiny metal oxide nanoparticles should be desirable anode materials. This point motivated us to develop a simple, scalable, and general synthesis route for preparing high-rate Li-ionbattery anodes. Despite the appeal of this kind of hollow, metal oxide based nanocomposite, there are only few wellestablished facile and scalable methods to synthesize such advanced nanostructured pure metal oxides.~([21-23]) For example, in our previous research, a general and scalable thermal oxidation strategy based on non-equilibrium interdiffusion was developed for the synthesis of porous metal oxide hollow micro-anostructures. However, this method is only applicable to the synthesis of pure metal oxides, which limits its application in the preparation of high-rate Li-ion-battery anode materials.~([23])
机译：锂离子电池作为便携式电子产品和电动/混合动力汽车的主要能量存储设备类型，已在科学和工业界引起了相当大的关注。〜（[1]）市场对其高电动势的需求不断增长，高能量密度和高可循环性激发了许多旨在开发用于锂离子电池的新型高性能电极材料的研究工作。〜（[2，3]）尽管锂离子电池的性能不断提高，但它们的性能却不断提高。能量密度，循环寿命和倍率性能仍不足以用于消费电子，交通运输和大规模可再生能源存储。〜（[4-6]）近来，纳米化已广泛应用于电池电极材料的设计中〜（[1，7，8]），但是，纳米级材料的缺点是它们无法像微孔一样紧密地堆积在集电器上计量材料;这个事实意味着由纳米材料制成的电极具有较高的孔隙率，从而导致电池容量降低。〜（[9]）因此，同时提高倍率能力和电极密度的最佳方法是使用微米级由聚集的纳米粒子组成的粒子。然而，这种布置的缺点在于，位于纳米聚集体的中心周围的一次颗粒显示出大的电阻，因为这些颗粒未与导电剂连接，因此导致在高速率充电和放电期间的高过电势。 〜（[9]）为了克服这个缺点，我们假设一次电极纳米粒子可以自组装并完全嵌入导电碳基质中。这种限制使得必须使用微米级颗粒来产生高体积能量密度和可靠的电池性能。通过引入空心电极（例如，用这些微小的纳米粒子构造空心球），可以用这些微米级电极材料实现进一步的改进。[（10-16]）另一方面，一种改善电子导电性的有效途径是导电次级相（例如导电碳或RuO_2）的添加或涂层。〜（[9，17-20]）因此，将这两个单独的微观结构特征合理组合到一个完整的电极颗粒中，具体来说就是构造导电次级相-由纳米颗粒组成的涂覆的空心电极颗粒是增强电化学性能的有吸引力的途径。基于这些想法，嵌有完全封装的微小金属氧化物纳米粒子的均匀空心碳微球应该是理想的阳极材料。这是促使我们开发一种简单，可扩展且通用的合成路线来制备高速率锂离子电池阳极的方法。尽管这种中空的，基于金属氧化物的纳米复合材料具有吸引力，但只有极少数成熟的简便且可扩展的方法来合成这种先进的纳米结构纯金属氧化物。[（21-23））例如，在我们之前的研究中，提出了基于非平衡互扩散的可扩展热氧化策略，用于合成多孔金属氧化物空心微结构/纳米结构。但是，该方法仅适用于纯金属氧化物的合成，这限制了其在制备高倍率锂离子电池负极材料中的应用。[[23]）

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