Normal aging in a lithium-ion cell may or may not increase the risk of a fire, depending on the type of degradation experienced by the cell. One such degradation method that leads to an increased risk of fire is lithium plating, where environmental factors or charging conditions can induce metallic lithium to form on the negative electrode within the cell. This metallic lithium can lead to internal short-circuit and subsequently thermal runaway if the short is the appropriate resistance to generate sufficient heat. However, capacity and energy loss during use can limit the amount of energy stored within the system, which would limit the energy release in the event of a failure (i.e. failure of a new system with full capacity may be more severe than an older/used system with only 50% available energy remaining).
Another non-energetic failure mode of lithium-ion cells may involve internal corrosion of cells or mechanical damage to cells, where electrolyte may leak from the compromised cells (Mikolajczak et al. 2011). Electrolyte leakage can lead to other problems (such as short-circuiting electronics that initiates larger failures), but the electrolyte itself presents concerns from a ventilation perspective. Lithium-ion electrolyte is typically composed of a mixture of organic carbonates such as ethylene carbonate or dimethyl carbonate (Mikolajczak et al. 2011). Such leaked carbonates are ignitable and may present a combustion hazard. Note, however, that leaked electrolyte is not an expected occurrence during normal operation of lithium-ion batteries and represents a failure of the cell(s) involved. In addition, many lithium-ion cells do not contain a substantial quantity of available liquid electrolyte that may leak out of a damaged cell. Furthermore, a volatile organic compound detector may be sufficient to detect a leak, and electrolyte vapor has a fairly distinct smell that can be detected by a person in the vicinity of such a leak.
Energetic failures in lithium-ion batteries have the potential to release substantial gas and, therefore, may pose a hazard that can be mitigated through ventilation.
Thermal runaway may result from electrical contact between the negative and positive electrodes. Thermal runaway occurs when the active materials within the cell have an exothermic chemical reaction, resulting in a rapid release of stored energy (Mikolajczak et al. 2011). This stored energy takes the form of both electrical energy (stored as chemical potential energy) and chemical energy (stored in the form of combustible materials such as the carbonate electrolyte) (Mikolajczak et al. 2011). A thermal runaway reaction in a lithium-ion cell occurs when the rate of heat generation of the cell exceeds the cell's rate of heat loss to its surroundings and the temperatures inside the cell are present for a sufficient time to initiate self-heating of the internal cell materials. The time it takes to initiate a thermal runaway reaction in a lithium-ion cell will depend on a number of factors, including the manner in which heat is generated by (or applied to) the cell, the cell chemistry, the state of charge of the cell, and the cell's surroundings. Thermal runaway can result in flammable gases being vented from a cell which can then ignite or lead to a potential explosion hazard. The vented gases can include hydrogen, carbon dioxide, carbon monoxide, and hydrocarbons such as methane, ethylene, ethane, propylene, and propane (Somandepalli et at. 2014).
, and they basically told me to go away. I plan to contact Rayovac next, hoping for a different response.
