Lithium-ion battery structure that self-heats at low temperatures

Here we report a lithium-ion all-climate battery that very efficiently heats itself up in extremely cold environments by diverting current through a strip of metal foil to generate heat of resistance and then reverts to normal high-power operation. A battery for all seasons Lithium-ion batteries, ubiquitous in powering smart phones and laptops, suffer severe power loss at subfreezing temperatures, limiting their use in applications such as electric cars and high-altitude drones. The problem can be mitigated by adding external heaters and insulating material to the battery, but with a severe weight penalty. Now Chao-Yang Wang and colleagues have developed an 'all-climate' lithium-ion battery by adding a strip of metal foil of specified resistance to the interior of a conventional battery. At low temperatures, current is diverted through the foil and heat of resistance is produced. When the battery's internal temperature is raised above zero degrees, a switch is triggered such that it reverts to normal operation. Only a small amount of the battery's capacity needs to be 'traded' for an increase in discharge power relative to normal Li-ion batteries. Lithium-ion batteries suffer severe power loss at temperatures below zero degrees Celsius, limiting their use in applications such as electric cars in cold climates and high-altitude drones 1 , 2 . The practical consequences of such power loss are the need for larger, more expensive battery packs to perform engine cold cranking, slow charging in cold weather, restricted regenerative braking, and reduction of vehicle cruise range by as much as 40 per cent 3 . Previous attempts to improve the low-temperature performance of lithium-ion batteries 4 have focused on developing additives to improve the low-temperature behaviour of electrolytes 5 , 6 , and on externally heating and insulating the cells 7 , 8 , 9 . Here we report a lithium-ion battery structure, the ‘all-climate battery’ cell, that heats itself up from below zero degrees Celsius without requiring external heating devices or electrolyte additives. The self-heating mechanism creates an electrochemical interface that is favourable for high discharge/charge power. We show that the internal warm-up of such a cell to zero degrees Celsius occurs within 20 seconds at minus 20 degrees Celsius and within 30 seconds at minus 30 degrees Celsius, consuming only 3.8 per cent and 5.5 per cent of cell capacity, respectively. The self-heated all-climate battery cell yield