Introductory Chapter: Lithium-Ion Batteries - Thin Film for Energy Materials and Devices

In 2019, the Nobel Prize in Chemistry has been awarded to John B. Goodenough, M. Stanley Whittingham, and Akira Yoshino for their research in improving battery technology. It is the invention of lithium-ion battery (LIB). The energy density of LIB with high discharge voltage (3.6 V) is nearly twice that of Ni-Cd batteries, and excellent cycle life and higher level of intrinsic safety have been demonstrated. The LIB has revolutionized our lives and is widespread from small-scale devices such as mobile phone to emergency distributed power supply, electric vehicle, etc. Lithiumion batteries are evolving even now. Many current types of research for LIB focus on life extension, energy density, safety, cost reduction, and charging speed. Thin film LIB is one of the forms of LIB. It has attracted much interest for use as power sources of smart cards, implantable medical devices, micro-sensors, and so on. The thin film LIB is composed of the anode, cathode, and electrolyte with thicknesses on the order of microns. As the demands for safety, higher energy density, and other performance metrics increase, research into anode, cathode, and electrolyte materials has been rapidly progressing. Cathode materials are often mixed metal oxides involving lithium ion such as LiCoO2 and LiMn2O4. Anode materials are lithium metal, carbon-based materials, and inorganic compounds. Both the cathode and anode materials are film, chosen for their ability to intercalate, and de-intercalate lithium ion while maintaining their structural integrity. The current research of electrolyte, whose form is preferable to be solid in thin film batteries, trends toward ceramics such as lithium lanthanum zinc oxide (LLZO) and lithium lanthanum titanium oxide (LLTO). The optimal electrolyte should be an efficient ion-conductor and a good electrical insulator allowing the battery to operate safely. The optimal combination of these materials can yield a battery that is light, thin, long-lasting, and safe.