Low-temperature Sodium-Beta Battery

Researchers at Lawrence Livermore National Laboratory have modeled a high-performance, rechargeable sodium-beta battery that is expected to provide twice the specific energy of the best Li-ion system without the high-temperature operating requirements of conventional sodium-beta systems.  The improved battery design employs a low-melting Na alloy as the anode that cycles between Na-rich and Na-lean alloy compositions.  The Na-based alloy anode has been designed so that the other alloying elements are electrochemically stable at potentials where Na is oxidized and reduced.  Various low-melting alloy systems have also been identified for fabrication of the cathode.  A battery of this design is anticipated to have a specific energy greater than 400 Wh/kg, and an expected life of 4500 charge-discharge cycles.  Also, like conventional Na-beta cells, a battery of this improved design would not generate gaseous products in the event of an overcharge.

 The most popular power source for all-electric vehicles (EVs), hybrids and plug-ins (HEVs/PHEVs) is presently the high-temperature sodium-nickel chloride (ZEBRA) system. Although robust, ZEBRA batteries are limited to a range of 120–180 miles, and the battery must be heated after four hours of inactivity. LLNL’s improved, low-temperature design for a Na-B battery overcomes those drawbacks.  Additionally, ZEBRA batteries require a double-walled, Dewar-style battery case to reduce conductive heat loss. Because it operates at ambient temperature, the LLNL design does not demand this elaborate casework, and the result is significant savings in mass, weight, and cost of battery production.

• Designs can be made fully operational at ambient/room temperature and lower with no performance degradation
• Ambient temperature operation results in significant energy efficiencies compared to conventional sodium-beta batteries
• Expected life is 4,500 charge–discharge cycles, twice as long as the best Li-ion batteries
• No gaseous products are formed or released in the event of an overcharge
• The design can be readily modified or re-formed to meet specific application requirements; embodiments may be cylindrical or tubular, for example.
• Electrodes may be formed of various low-melting material combinations that best suit a targeted application.

• Motive applications: powering EVs, HEVs, and PHEVs including automobiles, buses, delivery vans, transport trucks, and other vehicles.
• Marine applications: deep-sea rescue submersibles and exploration–research vehicles; stand-by power for long-distance submarines and a variety of sea-surface vessels.
• Stationary uninterruptible power supplies (UPSs) for server farms, load-leveling, peak-shaving,  grid storage, drilling and oil production downhole equipment.
• Lighter and better-performing power supplies for satellites.