Showing papers by "Yayuan Liu published in 2019"
TL;DR: In this article, the authors discuss the challenges and future research directions towards fast charging at the level of battery materials from mass transport, charge transfer and thermal management perspectives, and highlight advanced characterization techniques to understand the failure mechanisms of batteries during fast charging, which in turn would inform more rational battery designs.
Abstract: Extreme fast charging, with a goal of 15 minutes recharge time, is poised to accelerate mass market adoption of electric vehicles, curb greenhouse gas emissions and, in turn, provide nations with greater energy security. However, the realization of such a goal requires research and development across multiple levels, with battery technology being a key technical barrier. The present-day high-energy lithium-ion batteries with graphite anodes and transition metal oxide cathodes in liquid electrolytes are unable to achieve the fast-charging goal without negatively affecting electrochemical performance and safety. Here we discuss the challenges and future research directions towards fast charging at the level of battery materials from mass transport, charge transfer and thermal management perspectives. Moreover, we highlight advanced characterization techniques to fundamentally understand the failure mechanisms of batteries during fast charging, which in turn would inform more rational battery designs. Along with high energy density, fast-charging ability would enable battery-powered electric vehicles. Here Yi Cui and colleagues review battery materials requirements for fast charging and discuss future design strategies.
866 citations
TL;DR: With its roll-to-roll compatible fabrication procedure, WGC serves as a highly promising material for the practical realization of Li metal anodes in next-generation high energy density secondary batteries.
Abstract: Lithium (Li) metal has long been considered the “holy grail” of battery anode chemistry but is plagued by low efficiency and poor safety due to its high chemical reactivity and large volume fluctuation, respectively. Here we introduce a new host of wrinkled graphene cage (WGC) for Li metal. Different from recently reported amorphous carbon spheres, WGC show highly improved mechanical stability, better Li ion conductivity, and excellent solid electrolyte interphase (SEI) for continuous robust Li metal protection. At low areal capacities, Li metal is preferentially deposited inside the graphene cage. Cryogenic electron microscopy characterization shows that a uniform and stable SEI forms on the WGC surface that can shield the Li metal from direct exposure to electrolyte. With increased areal capacities, Li metal is plated densely and homogeneously into the outer pore spaces between graphene cages with no dendrite growth or volume change. As a result, a high Coulombic efficiency (CE) of ∼98.0% was achieved u...
179 citations
TL;DR: The abundant nitrogen species within g-C3 N4 nanosheets can form transient LiN bonds to powerfully stabilize the lithium-ion flux and thus enable a CE over 99% for 900 cycles and smooth deposition at high current densities and capacities, surpassing most previous works.
Abstract: Commercial deployment of lithium anodes has been severely impeded by the poor battery safety, unsatisfying cycling lifespan, and efficiency. Recently, building artificial interfacial layers over a lithium anode was regarded as an effective strategy to stabilize the electrode. However, the fabrications reported so far have mostly been conducted directly upon lithium foil, often requiring stringent reaction conditions with indispensable inert environment protection and highly specialized reagents due to the high reactivity of metallic lithium. Besides, the uneven lithium-ion flux across the lithium surface should be more powerfully tailored via mighty interfacial layer materials. Herein, g-C3 N4 is employed as a Li+ -modulating material and a brand-new autotransferable strategy to fabricate this interfacial layer for Li anodes without any inert atmosphere protection and limitation of chemical regents is developed. The g-C3 N4 film is filtrated on the separator in air using a common alcohol solution and then perfectly autotransferred to the lithium surface by electrolyte wetting during normal cell assembly. The abundant nitrogen species within g-C3 N4 nanosheets can form transient LiN bonds to powerfully stabilize the lithium-ion flux and thus enable a CE over 99% for 900 cycles and smooth deposition at high current densities and capacities, surpassing most previous works.
174 citations
TL;DR: A previously overlooked mechanism by which lithium deposits can corrode on a copper surface is reported, and a Kirkendall-type mechanism is validated through electrochemical analysis.
Abstract: Developing a viable metallic lithium anode is a prerequisite for next-generation batteries. However, the low redox potential of lithium metal renders it prone to corrosion, which must be thoroughly understood for it to be used in practical energy-storage devices. Here we report a previously overlooked mechanism by which lithium deposits can corrode on a copper surface. Voids are observed in the corroded deposits and a Kirkendall-type mechanism is validated through electrochemical analysis. Although it is a long-held view that lithium corrosion in electrolytes involves direct charge-transfer through the lithium-electrolyte interphase, the corrosion observed here is found to be governed by a galvanic process between lithium and the copper substrate-a pathway largely neglected by previous battery corrosion studies. The observations are further rationalized by detailed analyses of the solid-electrolyte interphase formed on copper and lithium, where the disparities in electrolyte reduction kinetics on the two surfaces can account for the fast galvanic process.
138 citations
01 Dec 2019
TL;DR: Li metal is the ultimate anode choice due to its highest theoretical capacity and lowest electrode potential, but it is far from practical applications with its poor cycle lifetime as discussed by the authors. But, despite the exciting improvement on Li metal cycling capability, problems still exist with these methodologies, such as the deficient long-time cycling stability of interphase materials and the accelerated Li corrosion for high surface area three-dimensional composite Li anodes.
Abstract: Li metal is the ultimate anode choice due to its highest theoretical capacity and lowest electrode potential, but it is far from practical applications with its poor cycle lifetime. Recent research progresses show that materials designs of interphase and host structures for Li metal are two effective ways addressing the key issues of Li metal anodes. Despite the exciting improvement on Li metal cycling capability, problems still exist with these methodologies, such as the deficient long-time cycling stability of interphase materials and the accelerated Li corrosion for high surface area three-dimensional composite Li anodes. As a result, Coulombic efficiency of Li metal is still not sufficient for full-cell cycling. In the near future, an interphase protected three-dimensional composite Li metal anode, combined with high performance novel electrolytes might be the ultimate solution. Besides, nanoscale characterization technologies are also vital for guiding future Li metal anode designs.
136 citations
89 citations
TL;DR: It is demonstrated that a composite lithium metal electrode with an ion-conducting mesoscale skeleton can improve electrochemical performance by locally reducing the current density and the potential for short-circuiting is largely alleviated.
Abstract: Lithium metal-based batteries are attractive energy storage devices because of high energy density. However, uncontrolled dendrite growth and virtually infinite volume change, which cause performance fading and safety concerns, have limited their applications. Here, we demonstrate that a composite lithium metal electrode with an ion-conducting mesoscale skeleton can improve electrochemical performance by locally reducing the current density. In addition, the potential for short-circuiting is largely alleviated due to side deposition of mossy lithium on the three-dimensional electroactive surface of the composite electrode. Moreover, the electrode volume only slightly changes with the support of a rigid and stable scaffold. Therefore, this mesoscale composite electrode can cycle stably for 200 cycles with low polarization under a high areal current density up to 5 mA/cm2. Most attractively, the proposed fabrication process, which only involves simple mechanical deformation, is scalable and cost effective, providing a new strategy for developing high performance and long lifespan lithium anodes.
69 citations