Tortuosity Anisotropy in Lithium-Ion Battery Electrodes
Tortuosity Anisotropy in Lithium-Ion Battery Electrodes
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DOI：
10.1002/aenm.201301278
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发表时间：
2014-04-01
影响因子：
27.8
通讯作者：
Wood, Vanessa
中科院分区：
文献类型：
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作者：
Ebner, Martin;Chung, Ding-Wen;Wood, Vanessa
高性能锂离子电池（LIB）需要改进的活性材料和优化的多孔电极微结构。实验和计算研究都表明，LIB电极的微观结构影响关键性能指标。[1-7]例如，Buqa等人在2005年对石墨的实验研究报告了速率-性能对可控电极制造参数（如孔隙率和负载）的依赖性，并表明所获得的性能与石墨片形成的曲折电极微结构有关。[3]最近，Harris等人已经原位成像了球形中间相碳微珠（MCMB）电极上的不均匀锂化和金属锂电镀。[7]随后，这些限制LIB耐久性和安全性的影响与微观结构的不均匀性有关。[8]微观结构对LIB性能指标（如充电和放电速率，电池寿命和安全性）产生影响的原因在概念上是明确的。[8]在工业LIB电极制造中，将活性颗粒、导电剂和聚合物粘合剂在溶剂中的悬浮液浇铸并干燥，并使用研磨来实现高能量密度电池所需的致密、低孔隙率电极。[9]该制造工艺不允许微结构控制，使得可能产生复杂、曲折的微结构，导致有效电解质电导率和扩散率降低。由于在电解质相中的传输限制了具有高速率能力所关注的快速固态扩散率的材料如石墨的性能，因此多孔电极的微观结构变得至关重要。[2]在这项工作中，我们试图量化控制多孔电极制造的参数，如颗粒形状和颗粒化，以及它对控制电池性能和可靠性的关键微观结构特性的影响。在多孔电极的宏观描述中，电极弯曲度（τ）的概念与电极孔隙率（ε）沿着使用作为由于电极的微结构而导致的有效电解质电导率和扩散率降低的量度。为了突出弯曲度和孔隙率对电极性能的影响，我们模拟了负载为10 mAh cm− 2的高能石墨电极的放电行为。对于特定材质集，
High-performance lithium-ion batteries (LIBs) require improved active materials and optimized porous electrode microstructures. Both experimental and computational studies have demonstrated that the microstructure of LIB electrodes influences key performance metrics.[1–7] For example, the experimental study of graphite by Buqa et al. in 2005 reported the dependence of rate-performance on controllable electrode fabrication parameters such as porosity and loading and suggests that the obtained performance is linked to the tortuous electrode microstructure formed by graphite platelets.[3] More recently, inhomogeneous lithiation and metallic lithium plating on spherical mesocarbon microbead (MCMB) electrodes has been imaged in situ by Harris et al.[7] Subsequently, these effects, which limit durability and safety of LIBs, were linked to microstructural inhomogeneity.[8] The reason why microstructure has an impact on LIB performance metrics such as charge and discharge rate, cell life, and safety is conceptually clear.[8] In industrial LIB electrode manufacturing, a suspension of active particles, conductive agents, and polymeric binder in a solvent is cast and dried, and calendaring is used to achieve the dense, low porosity electrodes required for high energy density batteries.[9] This manufacturing process does not allow for microstructure control, such that complex, tortuous microstructures can result, leading to decreased effective electrolyte conductivity and diffusivity. Because transport in the electrolyte phase limits performance for materials such as graphite with fast solid-state diffusivities of interest for high rate capability, the microstructure of the porous electrodes becomes critical.[2] In this work, we seek to quantify parameters that control porous electrode manufacturing, such as particle shape and calendaring, and its impact on microstructural properties that are key to controlling battery performance and reliability.In the macroscopic description of porous electrodes, the concept of electrode tortuosity (τ) is used along with electrode porosity (ε) as a measure for the decrease in effective electrolyte conductivity and diffusivity due to the microstructure of the electrode. To highlight the impact that tortuosity and porosity can have on electrode performance, we simulate the discharge behavior of a high energy graphite electrode with a loading of 10 mAh cm− 2. For a specific material set where the