Lithium-ion batteries store electrical energy in a positive electrode made of a lithium compound that is reversibly intercalated with lithium ions, and a negative electrode made of carbon or graphite. When lithium reacts violently with water, a non-aqueous electrolyte is used. It is a mixture of ionized organic solvents, such as propylene carbonate with an appropriate lithium solution. The separator is a microporous plastic film that can be coated with ceramic particles to improve battery safety.
For consumer batteries, lithium cobalt (LCO) is widely used as a cathode material, but this is expensive, while for BESS applications a lower-cost alternative material is used. These include mixed oxides of nickel, cobalt and aluminium (NCA), nickel, cobalt and manganese (NCM), in which the cobalt content is diluted. Manganese dioxide spinel (LMO) and lithium iron phosphate (LFP) are also used to reduce costs. For anodes, graphite or carbon is usually used, but silicon is being investigated and lithium titanate (LTO) can be used. The key to wider use of BESS is a longer cycle life and lower cost. The use of lithium-ion batteries in electric vehicles has reduced costs.
The safety of lithium-ion batteries needs careful consideration. They have high energy density and are flammable with organic electrolytes. Thermal loss of control is a risk, and the choice of materials, battery and battery structure and charging system need to be carefully specified to ensure that problems are minimized in service. Battery monitoring system with thermal sensors, voltage and current measurements and fuses for safe operation.
Na-s battery is a solid ceramic material with molten liquid sodium and sulfur as electrode materials. It works at a high temperature of 300° to 350°C to keep the electrode liquid and achieve good ionic conductivity in the electrolyte. The electrolyte is β -alumina (β -al2o3), which conducts sodium ions at operating temperature. Sodium and sulfur react to form sodium polysulfide during discharge.