Lithium metal anodes

Secondary lithium-metal batteries which have a lithium-metal anode are attractive because their energy density is theoretically higher than that of lithium-ion batteries. Lithium-molybdenum disulfide batteries were the world s first secondary cylindrical lithium—metal batteries. However, the batteries were recalled in 1989 because of an overheating defect. Lithium-manganese dioxide batteries are the only secondary cylindrical lithium—metal batteries which are manufactured at present. Lithium-vanadium oxide batteries are being researched and developed. Furthermore, electrolytes, electrolyte additives and lithium surface treatments are being studied to improve safety and recharge-ability. 

These values are poor compared with lithium-ion cells, whose corresponding values are 500 cycles and above 130 °C. This poor performance is explained mainly by the characteristics of the lithium-metal anode, and specifically its low cycling efficiency. 

Many studies have been undertaken with a view to improving lithium anode performance to obtain a practical cell. This section will describe recent progress in the study of lithium-metal anodes and the cells. Sections 3.2 to 3.7 describe studies on the surface of uncycled lithium and of lithium coupled with electrolytes, methods for measuring the cycling efficiency of lithium, the morphology of deposited lithium, the mechanism of lithium deposition and dissolution, the amount of dead lithium, the improvement of cycling efficiency, and alternatives to the lithium-metal anode. Section 3.8 describes the safety of rechargeable lithium-metal cells. 

There have been many attempts to improve the cycling efficiency of lithium anodes. We describe some of them below, by discussing electrolytes, electrolyte additives, the stack pressure on the electrode, composite anodes, and alternatives to the lithium-metal anode anode. 

An Alternative to the Lithium-Metal Anode (Lithium-Ion Inserted Anodes)... 

It is worthwhile attempting to develop a rechargeable lithium metal anode. This anode should have a high lithium cycling efficiency and be very safe. These properties can be realized by reducing the dead lithium. Practical levels of lithium cycling efficiency and safety could be achieved... 

Today we have some understanding of the first lithium intercalation step into carbon and of the processes taking place on the lithium metal anode. A combination of a variety of analytical tools including di-latometry, STM, AFM, XPS, EDS, SEM, XRD, QCMB, FTIR, NMR, EPR, Raman spectroscopy, and DSC is needed in order to understand better the processes occurring at the anode/electrolyte interphase. This understanding is crucial for the development of safer and better lithium-based batteries. 

Figure 1. Discharge curves for 2325 coin cells with lithium metal anodes and electrolytic (crystalline) vs amorphous manganese oxide-based cathodes.

Mild Steel Disc Spring Stainless Steel Disk Lithium Metal Anode... 

Figure 2.3 Basis of a lithium iodide cell (schematic) (a) electrons are liberated at the lithium metal anode and re-enter the cell via the I2/P2PV cathode (b) lithium ion transport across the electrolyte via Li vacancies, to form Lil at the anode. The number of vacancies (Schottky defects) has been grossly exaggerated.

Unlike the anode-targeted additives discussed in the preceding part, the additives intended for cathode protection have a much longer history than lithium ion technology itself and were originally developed for rechargeable cells based on lithium metal anodes and various 3.0 V class cathode materials. 

As discussed below, there are problems with morphological changes and passivation reactions at lithium metal negative electrodes in secondary cells, which reduce cycle life and the practical energy density of the system, and may in some circumstances introduce safety hazards. A more recent development involves the replacement of the lithium metal anode by another insertion compound, say C Dm. In this cell, the electrochemical process at the negative side, rather than lithium plating and... 

This battery was based on a lithium metal anode and a molybdenum disulphide cathode ... 

It was possible to improve the interfacial properties of Li metal anodes in liquid electrolyte solutions using additives that modify the Li-surface chemistry, such as C02 [23-27] and HF [28,29], Using PEO-based gel electrolyte systems effectively suppressed dendritic deposition of lithium [30], In Section C we report on a very good charge-discharge performance of lithium metal anodes in PVdF-HFP gel electrolyte systems. Furthermore, addition of C02 to the PVdF-HFP gel electrolyte system considerably improves the charge/discharge characteristics [31]. 

Figure 7 Charge-discharge cycling efficiency of lithium metal anode at 0.5 mA cnT2...

Figure 8 Micrographs of lithium metal anode at the first and fifth cycle in (a) PEO gel without C02, (b) PVdF-HFP gel without C02, and (c) PVdF-HFP gel with C02.

The surface film on such lithium particles have been analyzed with X-ray photoelectron spectroscopy, which shows that the surface film has the same chemical compositions and structure, as those obtained for lithium particles deposited in propylene carbonate with LiPF6. This means that HF works as a modification agent during the electrochemical deposition of lithium. The clear suppression of lithium dendrite is very important for rechargeability of lithium metal anode. In fact,... 

Scrosati and coworkers [165] have fabricated an all solid lithium battery by combining a PAN based polymer electrolyte (containing EC and PC) with a lithium metal anode and a poly pyrrole (pPy) film cathode. Although the Coulom-bic efficiency was found to be high, near 90%, the battery has a poor shelf life. 

Ryou, M.H., Lee, D.I., Lee, I.N., Lee, Y.M., Park, I.K., Choi, I.W., 2012. Excellent cycle life of lithium-metal anodes in Uthium-ion batteries with mussel-inspired polydopamlne-coated separators. Adv. Energy Mater. 2,645-650. 

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