Batteries
Overview
DEFINITION AND SCOPE The term lithium battery refers to an entire family of battery types, with varying chemical compositions. The common properties of these chemical constituents are that the negative and the positive electrode materials serve as hosts for lithium ions, and that the battery contains a non-aqueous (organic) conductive electrolyte .
Lithium batteries are manufactured principally in two main types: (1) ‘Primary’, also known as non-rechargeable battery types and (2) ‘Secondary’ rechargeable type. Batteries used for high-power or commercial, automotive and aerospace applications rely on rechargeable technology.
This guidance is mainly focused on rechargeable lithium batteries with additional commentary on non-rechargeable lithium batteries, in the context of their transport and disposal.
COMPOSITION OF ‘LITHIUM’ BATTERIES Despite the use in common language of the term ‘lithium battery’ there are several types in popular use, with differing technologies. Each type or chemical composition has its own performance characteristics. 3.1 Lithium-thionyl chloride (LiSOCl2) These are non-rechargeable and can be high capacity. The main physical risk is a short circuit from inadvertent contact with the terminals. Many types have fuses built in to limit the effect or severity of a short circuit. However, some do not, and consequently can present a serious fire risk. They can have very low internal resistances so that, if shorted, very high currents can flow which can result in rapid heating and temperature escalation which gives rise to the consequent risk of explosion. If subsequently there are attempts at repeatedly re-charging a ‘shorted-out’ battery, there is also a risk of explosion. The other main risk to LiSOCl2 cells is corrosion by saltwater since they are often used in marine applications. The inadvertent introduction of saltwater provides a contaminant which can catalyse decomposition, the separation of a single chemical compound into its two or more elemental parts or to simpler compounds. Ironically this effect is used extensively in safe neutralisation of lithium cells prior to transport to disposal. 3.2 Lithium manganese dioxide (LiMnO2) Rechargeable versions are available, but most are non-rechargeable. They are the type of lithium cells often used as small current devices in watches and memory backups in computers etc. The hazards from these batteries are unintentional polarity changes, or reverse charging when overheating will cause failure and possible fire or explosion. Effects can be minor and risks imagined to be trivial but they must never be ignored. 3.3 Lithium ion (Li-ion) Li-ion is a recent technology that is now prevalent in the consumer portable electronics market. These batteries are rechargeable and present the most severe consequences of any rechargeable battery failure if charging is not carried out using the correct charging technology or procedure. Lithium-ion batteries cannot tolerate overcharging and cannot be trickle charged continuously because of this. Overcharging can result in the deposition of lithium metal on one of the electrodes, which then becomes a fire hazard. The battery must be charged using a charger that follows a rigid charging regime and has both overheat protection and time-out protection. 3.4 Lithium iron phosphate (LiFePO4) These have a lower energy density so are more stable and therefore safer than most other lithium batteries. This performance is illustrated in Figure 1. These batteries also have a longer lifetime (1400 or more charge-cycles). They can be configured as much lighter replacements for 12-volt lead acid batteries (e.g. often operationally dormant Tracker batteries) so may have applications for field work where formerly car batteries were used with consequent positive benefits for manual handling and in protection from sulphuric acid (H2SO4) spillage.
Hazards Lithium ion rechargeable batteries have the lithium incorporated in a compound or ‘intercalated’ with another material. The effects of lithium-based malfunction or the severity of the consequences of the abuse will depend on the type of battery. OPERATIONAL HAZARD POSSIBLE CONSEQUENCES Over charging Venting, fire, explosion Forced discharge Overheating, venting Short circuit Overheating, venting, fire, thermal runaway Incineration/overheating Venting, explosion (if heating is excessive) Physical damage Release of potentially hazardous materials & spontaneous ignition. Short circuits Leaving for a long term uncharged or unmanaged Venting Table 1: Operational hazards and consequences Venting in this context describes release of gases from the battery, with some d