The Interface Effect During Lithium Deposition/dissolution Kinetics Process

With the rapid development of mobile electronics and electric vehicles,it is urgent and important to develop high energy density batteries.The theoretical capacity?3860mAh/g?of lithium metal anode is 11 times higher than that of the present graphite anode?340 mAh/g?.Consequently,the use of lithium metal instead of the graphite anode has become an important research direction in the area of batteries in recent years.Different from the traditional graphite anode,lithium metal anode inevitably forms lithium dendrites during repeated charging/discharging cycles.The lithium dendrites may be detached from the anode surface to form the so called"dead lithium",resulting in capacity fading.Furthermore,the growth of the lithium dendrites increase the specific surface area of the lithium metal anode and accelerate the chemical reaction between the lithium metal anode and the electrolyte.Once the lithium dendrites penetrate through the separator,the battery may catch fire or explode due to internal short circuit.In this paper,the plating and dissolution of lithium metal at the anode/electrolyte interface were studied by a variety of interface characterization methods.The effect of different interface morphology on the lithium plating and the mechanism of the growth of lithium dendrites were investigated in detail.We further designed and optimized the interface to inhibit the formation of the lithium dendrites.The main results of this paper are:1.By application of ether solvent,which has a high resistance against reduction,into a common carbonate electrolyte,the SEI component of the lithium metal interface was optimized,and the carbonate-ether mixed electrolyte was used to realize the self-inhibition of the growth of the lithium dendrites.2.Based on the catalytic action of polysulfide to ring-opening of ethylene carbonate in electrolyte,we designed an electrolyte which could self-repair and increase the polyoxyethylene content on the SEI of the lithium metal anode.3.A novel but simple method was proposed to prepare an“anode-material-free”lithium battery with high coulombic efficiency and without formation of lithium dendrites during cycling.The“anode-material-free”battery consisted of a LiFePO₄ electrode as the cathode and a Cu plate as the anode current collector.An additional Cu/Au surface protection layer was formed on the Cu plate anode current collector by an electrochemical and in-situ deposition during the first charge.Lithium ions were able to penetrate the surface of the Cu protection layer and adsorb on the Au seed layer as Li metal,while the Cu protection layer provided excellent interfacial protection,due to its chemical stability,mechanical strength and flexibility.