What is a Lithium Battery?
Lithium-ion batteries power the lives of millions of people every day through cell phones, laptops, hybrid cars and more. These batteries have higher energy density than other battery types, allowing them to be smaller and lighter.
They charge to 4.20V/cell, and going beyond this voltage stresses the battery and compromises safety. Environmental conditions, not cycling alone, govern a battery’s longevity.
What is a Lithium Ion Battery?
Lithium batteries use lithium ions to store energy. They are made up of cells with an anode, cathode, separator and electrolyte. The electrolyte carries positively charged lithium ions from the anode to the cathode and vice versa during charging and discharging, activating free electrons and creating a flow of electrical current to power devices like cell phones.
When the battery is not connected to a device, it is stored at room temperature in its packaging. It is a safe and durable rechargeable battery. It has a high working voltage and is used in many portable electronic devices such as digital cameras, mobile phone chargers, laptop computers, MP3 players, electric toothbrushes, and children’s toys.
The materials for lithium batteries are mined from a few countries around the world, often in impoverished ion lithium battery communities where mining can cause environmental degradation and human rights violations. These materials travel 80,000 kilometres from the mining site to downstream manufacturing facilities.
Anode
The positive electrode in a battery toward which positively charged particles are attracted. Anodes oxidize (lose electrons) during charging and reduce (gain electrons) during discharging.
Anode materials are selected for their excellent conductivity, stability and high coulombic output (the amount of electrical energy produced). Anodes can be made of zinc, lithium, graphite or platinum.
During charging, an external electric power source applies a voltage higher than the battery’s internal cell voltage, forcing lithium ions to flow from the anode to the cathode. During discharge, the reverse happens as electrons move from the cathode to the anode.
The negative electrode is passitivated with aluminium and the electrolyte is an alkyl carbonate solution. The solvents used in Li-ion batteries are flammable and toxic, and active research is ongoing to find non-flammable alternatives. Over time, extended storage can trigger the formation of a solid electrolyte interface film on the negative electrode, which increases resistance and limits cycling capacity. This can also result in irreversible loss of cyclable Li+, manifested as increased ohmic impedance and decreased Ah charge.
Cathode
The cathode of a lithium-ion battery stores the lithium ions that are released from the anode during discharging and provides a path for the electrons to flow through the electrode generating electricity. The cathode must have high capacity, good cyclability and safety.
A variety of structural and electrochemical properties determine the performance of cathodes, such as their mechanical strength (e.g., fracture toughness), capacity and cycling stability, and morphology. The latter includes avoiding the formation of a SEI layer on the cathode and maintaining an electrochemically active surface throughout its life.
Conventional cathode manufacturing follows a process that involves mixing the active and inactive materials into a slurry, coating the slurry on current collectors, drying and calendaring to achieve high packing density and volumetric capacity. This approach, however, often results in a high concentration of defects that may impact the physical and electrochemical performance.
During charging, the external power source applies a voltage higher than the cell’s internal voltage, forcing electrons to flow from the positive to the negative electrodes in the electrolyte. The electrolyte is a liquid medium that allows lithium ions to move back and forth between the electrodes but blocks electrons. It is composed of salts, solvents and additives.
Electrolyte
The electrolyte is the medium through which lithium ions are transported between the electrodes during the battery’s operation. Ionic liquids and polymer electrolytes show a number of advantages but are limited by low mechanical performance, low lithium ion transference numbers and narrow electrochemical stability windows.
The oxidation half-reaction at the anode results in the release of positively charged lithium ions, which are shuttled across the electrolyte towards the cathode where they recombine with electrons in the reduction half-reaction. The lithium ions are transported in the presence of an electric field generated by the external circuit.
Ionic Liquids (IL) are a promising candidate for an electrolyte because of their high decomposition temperature, good mechanical properties and non-flammability. ILs consist of a combination of cations and anions such as imidazolium, quaternary ammonium, pyrrolidinium and piperidinium. The ionic transport of Li ions in ILs is highly influenced by the cation and anions used. For example, N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide (PP13TFSI) shows a much higher ionic conductivity than PF6-BF4-based ionic liquids but it is limited by the solubility of the lithium polysulfides.
Safety
Lithium-ion batteries are used in a variety of electronic devices, including cell phones and laptops. They are also found in e-bikes, electric cars, and home battery storage systems. While this technology is a very useful power source, it comes with some safety concerns.
These batteries can be extremely dangerous if they become damaged or malfunction. A failure can trigger a thermal runaway where the cells in the pack start to self-heat and vent flaming gases.
Fortunately, these hazards can be mitigated by proper handling and maintenance. Built-in protection circuits limit peak voltage during charge and prevent the cell voltage from dropping too low during discharge. These circuits Portable lifepo4 battery can also monitor the temperature of the cells and prevent external short circuits.
When using lithium-ion batteries, be sure to follow the manufacturer’s instructions regarding charging and storing. Keep them away from anything combustible, and do not store in extreme temperatures. Avoid overcharging or over-discharging as it can reduce capacity and increase the risk of a fire or explosion. Additionally, never mix different brands of batteries. Each type of lithium battery has a unique operating range.
