Abstract: The worldwide increasingly tough circumstance of energy and environment urges the continuous and intensive inte-rest both in industry and in science upon the utilization of renewable energy sources and the development of efficient and safe energy storage techniques. Lithium-ion secondary batteries are a kind of high-specific-capacity and long-cycle-life energy storage devices which over the past decade have acquired considerable and fruitful research attentions and found wide applications in a rich variety of portable electronic devices and electric vehicles. On the other hand, the fast emergence of high-performance electronics has exaggera-ted the requirements of energy density, cycle stability and safety to a remotely high level for the commercialized lithium ion batteries.
For the sake of increasing Li-ion batteries’ energy density, anode materials with high capacity, e.g. silicon, tin, lithium, have been developed to substitute for the conventional graphite anode. Either silicon or tin anode stores and releases Li ions by reacting with them and forming lithium-containing compounds within a charge-discharge process, which generally accompanies huge volume change of the anode. This will cause these anode materials to be pulverized or even stripped from the current collector after expe-rienced relatively long time usage, and in consequence, the rapid fading of battery capacity and even failure. By contrast, Li metal anode’s charge-discharge process is based on dissolution/deposition of lithium on the current collector, and this process involves no reaction-phase-transition-induced volume change. Furthermore, lithium metal is regarded as an ideal candidate material for rechar-geable batteries due to its high theoretical specific capacity (3 860 mAh/g), low density (0.59 g/cm3) and the lowest electrochemical potential (-3.04 V vs RHE) within all anodes. Unfortunately, some key issues, such as Li dendrite growth, low columbic efficiency and uncontrolled-deposition-induced volume expansion, have restrained the commercialization of Li metal anodes.
Each time of lithium deposition will cause the growth of dendrites, and thus the Li dendrites will lead to internal short circuits and even battery explosion, which is considered as a serious safety problem. In addition, lithium dendrites will also increase the anode surface area, enabling the reaction between newly exposed lithium and electrolyte to form solid electrolyte interphase (SEI) that causes low columbic efficiency. In order to solve these problems, researchers have done a lot of studies on the lithium metal anodes, especially on the mechanism and inhibition methodology of dendrite growth. There have been proposed several theoretical models which describe the formation and growth behavior of Li dendrites, including diffusion model, SEI protection model, charge-induced growth model and film growth model, and furthermore, the corresponding inhibition solutions, such as uniform lithium ion flux method, SEI protection method, host-assisted stable deposition and electrostatic shielding method. By adopting these methods, the growth of lithium dendrites can be alleviated to a certain extent, but still the Li metal anodes are unsatisfactory for commercialization.
Herein, we summarize the global research works of lithium metal anode in recent years, introduce systematically several gene-rally recognized Li dendritic growth models and the corresponding influencing factors, and emphatically clarify the inhibition methods of dendrite growth and their effectiveness. Finally, we also put forward some suggestions for the future research direction of lithium metal anodes.
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