Electrochemical energy storage systems are categorized into different types, according to their mechanisms, including capacitors, supercapacitors, batteries and fuel cells. All battery systems include some main components: anode, cathode, an aqueous/non-aqueous electrolyte and a membrane that separates anode and cathode while being permeable to ions. Being one of the key parts of any new electronic device or electric vehicles, lithium ion batteries have gained great attention in recent years. Lithium ion batteries store/provide energy by insertion/extraction of lithium ions in/from the structure of the electrode materials in successive charge/discharge cycles. The energy and power densities, determine the batteries performance. In order to improve the energy/power density and cyclic life of a lithium ion battery, its electrode materials and electrolyte must be properly chosen. Cathode materials store energy through intercalation or conversion reactions, while the energy storage mechanism in anode materials are intercalation, conversion reactions or alloying/dealloying. Depending on the electrode material, one or more of the aforementioned mechanisms may take place which directly affect the battery performance. Each group of electrode materials have their own advantages and shortcomings; therefore, proper selection of the electrode material is an important issue in applicability of a lithium ion battery. This review covers the principles of energy storage in lithium ion batteries, anode and cathode materials and the related mechanisms, recent advancements and finally the challenges associated with enhancement of lithium ion batteries.

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