The paper "Ultracapacitors: Why, How, and Where is the Technology" by Andrew Burke reviews the science and technology of ultracapacitors, focusing on various electrode materials such as carbon, mixed metal oxides, and conducting polymers. The review highlights the current status and future projections of ultracapacitor technology, emphasizing their high power density, efficiency, and long shelf and cycle life compared to batteries. The paper discusses the mechanisms of energy storage in ultracapacitors, including double-layer capacitors and electrochemical capacitors utilizing pseudo-capacitance. It also explores the development of hybrid capacitors and the challenges in reducing electrode thickness, contact resistance, and electrolyte resistivity. The key design and cost issues in ultracapacitor development are identified, including electrode material properties, bonding techniques, electrolyte purity, and packaging. The paper concludes by discussing the potential for new markets if ultracapacitors can achieve higher energy densities and lower costs.The paper "Ultracapacitors: Why, How, and Where is the Technology" by Andrew Burke reviews the science and technology of ultracapacitors, focusing on various electrode materials such as carbon, mixed metal oxides, and conducting polymers. The review highlights the current status and future projections of ultracapacitor technology, emphasizing their high power density, efficiency, and long shelf and cycle life compared to batteries. The paper discusses the mechanisms of energy storage in ultracapacitors, including double-layer capacitors and electrochemical capacitors utilizing pseudo-capacitance. It also explores the development of hybrid capacitors and the challenges in reducing electrode thickness, contact resistance, and electrolyte resistivity. The key design and cost issues in ultracapacitor development are identified, including electrode material properties, bonding techniques, electrolyte purity, and packaging. The paper concludes by discussing the potential for new markets if ultracapacitors can achieve higher energy densities and lower costs.