Lithium metal safety

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. 

One of the most important factors determining whether or not secondary lithium metal batteries become commercially viable is battery safety, which is affected many factors insufficient information is available about safety of practical secondary lithium metal batteries [91]. Vanadium compounds dissolve electrochemi-cally and are deposited on the lithium anode during charge-discharge cycle. The... 

Table 3). However, their cycle life depends on the discharge and charge currents. This problem results from the low cycling efficiency of lithium anodes. Another big problem is the safety of lithium-metal cells. One of the reasons for their poor thermal stability is the high reactivity and low melting point (180 °C) of lithium. 

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. 

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... 

Instead it is a known as a lithium ion battery since it is free from lithium metal and hence free from the safety and stability problems of lithium cells. The commercialisation of this cell by Sony represents one of the most important breakthroughs in battery technology for many years and is a major success for solid state electrochemistry. 

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... 

The physical properties of lithium metal were given in Table 4.4. Despite its obvious attractions as an electrode material, there are severe practical problems associated with its use in liquid form at high temperatures. These are mainly related to the corrosion of supporting materials and containers, pressure build-up and the consequent safety implications. Such difficulties were experienced in the early development of lithium high temperature cells and led to the replacement of pure lithium by lithium alloys, which despite their lower thermodynamic potential remained solid at the temperature of operation and were thus much easier to use. 

The entry of lithium batteries into the consumer market is still quite recent and not much attention has so far been paid to disposal and the possibility of recycling procedures. Lithium metal, although not toxic, is a safety hazard since it is very reactive, especially in contact with water or in high humidity. This makes lithium batteries which have not been fully... 

Sony dubbed the new cell, lithium-ion, as only lithium-ions and not lithium metal are involved in the electrode reactions. The lithiated carbon had a voltage of about 0.05 V vs. lithium metal and avoided the safety issues of mossy and dendritic lithium metal deposits. The lithium-ion rechargeable battery system has replaced the heavier, bulkier, Ni-Cd and Ni-MH cells in most applications,... 

The substitution of the liquid electrolyte with the less reactive polymer electrolyte has led to lithium-polymer batteries, among the most likely to be commercialized for electric vehicles [89]. It must be stressed that the lithium-polymer battery is still a lithium-metal battery and not a lithium-ion one. Lithium-polymer batteries are solid-state, in that their electrolyte is a solid. A great safety advantage of this type of battery is that the electrolyte will not leak out if there is a rupture in the battery case. Furthermore, it can be assembled in any size and shape, allowing manufacturers considerable flexibility in cell design for electric vehicle or electronic equipment. 

To avoid the problems associated with lithium metal, lithium insertion materials (e.g., graphitic carbons) are being investigated as negative electrodes. With respect to lithium metal, the use of negative insertion materials improves the cycle life and safety of the battery but lowers the cell voltage, the theoretical specific capacity, and the charge transfer rate [104]. 

This type of Li battery has already widely diffused in the electronic consumer market, however for automotive applications the presence of a liquid electrolyte is not considered the best solution in terms of safety, then for this type of utilization the so-called lithium polymer batteries appear more convenient. They are based on a polymeric electrolyte which permits the transfer of lithium ions between the electrodes [21]. The anode can be composed either of a lithium metal foil (in this case the device is known as lithium metal polymer battery) or of lithium supported on carbon (lithium ion polymer battery), while the cathode is constituted by an oxide of lithium and other metals, of the same type used in lithium-ion batteries, in which the lithium reversible intercalation can occur. For lithium metal polymer batteries the overall cycling process involves the lithium stripping-deposition at the anode, and the deintercalation-intercalation at the anode, according to the following electrochemical reaction, written for a Mn-based cathode ... 

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