on of one molecule between two other molecules. Some 3D metal oxide structures have been shown to have a reversible capacity of more than 1000 mAh/g. Low-cost materials like iron manganese have also been proposed. One problem with lithium-ion batteries has been cost and toxicity with early batteries using cobalt as a cathode material. Cobalt has now largely been replaced with lithium manganese. In 2002 other battery technologies being discussed included zinc air and methanol cells, but these have failed to make an impact on the mobile phone market for mainly practical reasons. Batteries have some similarities with memory - both are storage devices and both achieve performance gain though materials innovation, packaging and structural innovation. Memory technologies are addressed in more detail in Chapter 7. Batteries and memory are both significant markets in their own right both by volume and value. New and replacement sales of batteries into the mobile-phones sector alone are approaching two billion units per year and account for between 4 and 5% of the individual BOM of each phone. Even assuming say between five and ten dollars per phone this is a $10 to $20 billion market. Wireless User Hardware Memory represents a higher percentage of the BOM at around 9 to 10% though with less year-on-year replacement sales (apart from additional plug-in memory). We address the technology economics of memory in Chapter 7. 5.3 Smart Phones and the User Experience Battery constraints are of course one of the two caveats that apply to the potential usability and profitability of smart phones. If a smart-phone battery runs flat by lunchtime then two things happen. The user gets annoyed and the operator loses an afternoon of potential revenue. The smarter smart phones deal with this by automatically switching off functions that are not being used. For example, there is no point in doing automatic searches for WiFi networks if the user never uses WiFi. There is no point in having a display powered up if the user cannot see it. Sm