Critical Current Density in Solid-State Lithium Metal Batteries: Mechanism,Influences, and Strategies

Solid-state lithium (Li) metal batteries (SSLMBs) have become a research hotspot in the energy storage field due to the much-enhanced safety and high energy density. However, the SSLMBs suffer from failures including dendrite-induced short circuits and contact-loss-induced high impedance, which are highly related to the Li plating/stripping kinetics and hinder the practical application of SSLMBs. The maximum endurable current density of lithium battery cycling without cell failure in SSLMB is generally defined as critical current density (CCD). Therefore, CCD is an important parameter for the application of SSLMBs, which can help to determine the rate-determining steps of Li kinetics in solid-state batteries. Herein, the theoretical and practical meanings for CCD from the fundamental thermodynamic and kinetic principles, failure mechanisms, CCD identifications, and influence factors for improving CCD performances are systematically reviewed. Based on these fundamental understandings, a series of strategies and outlooks for future researches on SSLMB are presented, endeavoring on increasing CCD for practical SSLMBs.     

A Novel 3D Li/Li9Al4/Li-Mg Alloy Anode for Superior Lithium Metal Batteries

Lithium metal has been recognized as the most promising anode material due to its high capacity and low electrode potential. However, the high reactivity, infinite volume variation, and uncontrolled dendrites growth of Li during long-term cycling severely limit its practical applications. To address these issues, herein, a novel 3D Al/Mg/Li alloy (denoted as AM-Li) anode is designed and constructed by a facile smelting-rolling strategy, which improves the surface stability, electrochemical cycling stability, and rate capability in lithium metal batteries. Specifically, the optimized AM-Li|AM-Li symmetric cell exhibits low polarization voltage (< 20 mV) and perfect cycling stability at 1 mA cm⁻²-1 mAh cm⁻² for more than 1600 h. Moreover, the AM-Li|NCM811 full cell exhibits superior rate capability up to 5 C and excellent cyclability for 100 cycles at 0.5 C with a high capacity retention of 90.8%. The realization of lithium-poor or lithium-free anode materials will be a major development trend of anode materials in the future. Therefore, the research shows that the construction of 3D alloy framework is beneficial to improve the cycling stability of Li anodes by suppressing the volume expansion effect and Li dendrite growth, which will promote the further development of lithium-poor metal anodes.     

A Targeted Functional Design for Highly Efficient and Stable Cathodes for Rechargeable Li‐Ion Batteries

Despite the great success of Li‐ion batteries (LIBs) up to now, higher demand has been raised with the emergence of the new generation electrics, such as portable devices and electrical vehicles. Even with the improvement on anodes, the cathodes with high capacity and long‐lastingness still remain a challenge. New 3D NiCo₂O₄@V₂O₅ core–shell arrays (CSAs) on carbon cloth as cathodes in LIBs have been reported in this work. The nanodesigned materials realize the theoretical specific capacity of V₂O₅ with high power rate based on the total mass of the framework and amount of active materials. The electrodes achieve superb cycling stability, among the most stable cathodes for LIBs ever reported. From both in situ transmission electron microscopy and quantum level calculations, the 3D NiCo₂O₄ nanosheet frameworks provide high electron conductivity and the skeleton of the robust CSAs without participating in the lithiation/delithiation; the thickness of the layered V₂O₅ plays a key role for Li diffusivity and the capacity contribution of electrodes. The structures herein point to new design concepts for high‐performance nanoarchitectures for LIB cathodes.