Safety lithium deposition

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. 

Thus, at temperatures lower than the liquid us temperature (usually above —20 °C for most electrolyte compositions).EC precipitates and drastically reduces the conductivity of lithium ions both in the bulk electrolyte and through the interfacial films in the system. During discharge, this increase of cell impedance at low temperature leads to lower capacity utilization, which is normally recoverable when the temperature rises. However, permanent damage occurs if the cell is being charged at low temperatures because lithium deposition occurs, caused by the high interfacial impedance, and results in irreversible loss of lithium ions. An even worse possibility is the safety hazard if the lithium deposition continues to accumulate on the carbonaceous surface. 

Lithium deposition is currendy being considered as the most serious safety concern for Li-ion cells. In particular the formation of high-surface lithium deposits during normal cell operation is the major contributing factor for the occurrence of PPB level safety issues [25,27,29]. 

Battery safety has been obviously given a special attention in this volume. Commercial lithium-ion cells and batteries are commonly used to power portable equipment, but they are also used to buildup larger batteries for ground (e.g. EVs), space and underwater applications. Chapter 17 provides test data on the safety of commercial lithium-ion cells and recommendations for safe design when these cells are used in much larger battery configurations. Chapter 18 focuses on safety aspects of LIBs at the cell and system level. In particular, abuse tolerance tests are explained with actual cell test data. Furthermore, internal short and lithium deposition occurring in lithium-ion cells and failure mechanism associated with them are discussed. In Chapter 19, the state of the art for safety optimization of all the battery elements is presented. This chapter also reports tests on not yet commercialized batteries, which pass all the security tests without the help of a BMS. 

Lithium insertion into titanium oxides plays on the redox couple Ti /TP at a potential of between 1.3 and 1.9 V versus Li/LL, depending on the polymorph. This potential window means that (1) safety risks linked to metallic lithium deposits can be avoided (intervening at 0 V) and (2) the copper collector can be replaced by less costly aluminum. 

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... 

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,... 

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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