Microstructure evolutions in lithium ion battery electrode manufacturing

Abstract

<p indent="0mm">Since its commercialization in the 1990s, the lithium-ion battery has been a huge success in the energy industry owing to its high energy density and long cycle life. They have been used in national strategic fields, such as satellites and unmanned aircraft, to promote a remarkable leap forward in new energy, new energy vehicles, and other emerging industries. Therefore, the development of lithium-ion batteries is a strategic high ground for competition among countries worldwide. The development and widespread use of lithium-ion batteries is driven by their high energy/power density, long cycle life, and low cost, which requires battery material innovation as well as advancements in manufacturing processes and equipment technology. Particularly, the power and energy storage applications require numbers of battery cells connected in series or parallel. High precision is required to ensure the consistency of the battery cell, to avoid module capacity loss and cycle life attenuation owing to the “shortboard effect,” and to ensure battery safety. Electrode manufacturing, which is the first critical process of lithium-ion battery production, consists of three critical steps: Mixing, coating, and rolling. The positive and negative electrode active materials, conductive agents, binders and solvents are mixed into slurry and coated on copper or aluminum foil. The positive/negative electrodes, which constitute the electrochemical reaction carrier and the battery’s core, are obtained after drying and roller compaction. The porous and multi-component electrode microstructure evolves and is constructed in a complex way during electrode manufacturing. The proportion of electrode slurry, mixing order, coating method, drying strategy, and rolling process can considerably affect the evolution of electrode microstructure, such as pore structure, active particle distribution and, conductive/bonding network. It also influences the lithium-ion battery’s electrochemical performance. Despite tremendous advances in high-energy-density materials, research on lithium-ion battery manufacturing lags, resulting in a large gap between laboratory and production scales. This requires an in-depth understanding of the manufacturing and the relationship between electrode microstructure evolution and battery performance. The advancement and application of cutting-edge slurry mixing, coating, and calendering technologies in electrode manufacturing are thoroughly reviewed in this paper. The evolution of electrode microstructure during manufacturing, in particular, and its impact on the battery’s electrochemical performance, are discussed in detail. Then, various novel electrode manufacturing techniques are summarized in terms of their significance and challenges, covering the innovations based on the current process (aqueous processing, simultaneous double-sided slot coating, multilayer co-coating and, multistage drying), dry processing (electron beam and ultraviolet curing forming, electrostatic dry-powder coating), three-dimensional printing, and template-based methods. We aim to gain a better understanding of electrode structure design, material preparation, and manufacturing processes through the perspective of the “Manufacturing-Microstructure-Performances” relationship and guide the development of high-performance lithium-ion batteries. Finally, perspectives on future developments toward accelerating electrode design and manufacturing process optimization are presented, including three main parts: (1) Developing the multiscale and whole-process simulation platform to connect the electrode manufacturing, microstructure, and battery performance; (2) constructing microstructure-controllable electrode manufacturing technology that is compatible with existing production infrastructure; and (3) researching the microstructure evolution of the post-lithium-ion battery manufacturing.