World's First Fast Rechargeable Battery at Low Temperature
Penn State and Penn State spin-off EC Power presented a solution to overcome the decline in performance of cold lithium-ion batteries.
Their idea is to create self-heating cells called All-Climate Battery, which rely on use of a nickel foil inside cells combined with a temperature sensor attached to a switch. If the battery pack is needed and temperature is below 0˚C (32˚F), the circuit will be closed and the nickel foil will work as heater:
"The all-climate battery uses a nickel foil of 50-micrometer thickness with one end attached to the negative terminal and the other extending outside the cell to create a third terminal. A temperature sensor attached to a switch causes electrons to flow through the nickel foil to complete the circuit. This rapidly heats up the nickel foil through resistance heating and warms the inside of the battery. Once the battery is at 32 degrees Fahrenheit, the switch turns off and the electric current flows in the normal manner.
While other materials could also serve as a resistance-heating element, nickel is low cost and works well."
According to Penn State, the results are very encouraging, while the prototype cells were only 1.5% heavier and cost was only 0.04% higher.
The team claims capability to heat battery cells from -4 to 32˚F (from -20˚C to 0˚C) within 20 seconds using 3.8% of cell capacity. Heating from -22 to 32˚F (from -30˚C to 0˚C) took 30 seconds and uses 5.5% of the available energy.
Why is heating batteries important? Well, cell performances (charging capability, efficiency) are much better at higher temperatures:
"Conventional batteries at below freezing temperatures suffer severe power loss, which leads to slow charging in cold weather, restricted regenerative breaking and reduction of vehicle cruise range by as much as 40 percent, the researchers said in today's (Jan. 20) issue of Nature. These problems require larger and more expensive battery packs to compensate for the cold sapping of energy."
We doubt whether 40% loss of range comes directly from a cold battery, because most of the range loss comes from driving conditions in the winter and heating (up to several kW of additional usage).
Chao-Yang Wang, William E. Diefenderfer Chair of mechanical engineering, professor of chemical engineering and professor of materials science and engineering and director, Electrochemical Engine Center said:
"It is a long standing problem that batteries do not perform well at subzero temperatures. This may not be an issue for phones and laptops, but is a huge barrier for electric vehicles, drones, outdoor robots and space applications."
"We don't want electric cars to lose 40 to 50 percent of their cruise range in frigid weather as reported by the American Automobile Association and we don't want the cold weather to exacerbate range anxiety. In cold winters, range anxiety is the last thing we need."
"Next we would like to broaden the work to a new paradigm called SmartBattery. We think we can use similar structures or principles to actively regulate the battery's safety, performance and life."
More details can be found in this article: "Lithium-ion battery structure that self-heats at low temperatures".
EC Power also presented a set of prismatic and pouch cells in 10 to 20 Ah capacity that were manufactured to demonstrate viability and to enable tests in vehicles.
All-Climate Battery Cells