New Electrode Materials for Magnesium Batteries and Metal Anodes
Beyond Lithium Ion Battery Systems
Magnesium ion batteries present a viable alternative to lithium ion batteries and are drawing the attention of major electric vehicle and battery manufacturers. This is due in part to each lithium ion carrying a single positive charge, while each magnesium ion has a plus-two (divalent) charge, allowing the magnesium ion battery to move twice as many electrons. Magnesium is also much cheaper and easier to acquire than lithium. Other benefits of using magnesium instead of lithium include greater stability and safety of the battery, as well as a potential 10x increase in storage capacity.Description
High-energy rechargeable magnesium ion batteries, which use low-cost, non-dendritic magnesium metal, provide an ideal energy storage system for a post lithium ion battery. However, Mg metal has a unique electrochemistry which prohibits its reversible deposition in aprotic solvents (except ethers) containing currently commercial ionic salts, such as Mg(TFSI)2 and MgClO4. Only corrosive Grignard and magnesium organohaloaluminates-based electrolytes can be used in the nonaqueous rechargeable Mg-metal batteries. However, the corrosive nature of these electrolytes limits the operating voltage window to a much lower level (<2.0V) than that in Li-ion batteries (<4.5V). Two new inventions are described here to enable Mg-ion batteries.
The first develops a new type of anode material that can replace a Mg metal anode to enable using non-aqueous electrolytes. Scientists at the National Renewable Energy Laboratory (NREL) have recently begun using magnesium borides (MgBx) as anodes in “beyond-Li-ion” battery systems, utilizing an MgB2 electrode as a host for Mg2+ ions. In this research, new anode materials with a general formula of Mg1-xB2 (MB, 0≤x≤1) are being investigated. Based on our previous study, the MB compounds can reversibly intercalate/deintercalate Mg2+ ions into their layered structure without destroying the structure. However, the slow diffusion kinetics and surface impurities impede electrochemical activities. Combining solid-state synthesis and soft chemistry, nanoscale MB materials will be synthesized to reduce Mg2+ diffusion distance. Electrochemical properties of these synthesized materials will be demonstrated in an optimized electrochemical testing system. This research will establish mechanisms of intercalation and deintercalation of Mg2+ in MB materials, and open new avenues for high-energy batteries. This novel approach has the capability to replace Mg metal in Mg ion/air batteries, enabling the use of non-aqueous electrolytes to achieve a much greater energy density (theoretical capacity of 2013 Wh/kg) than current Li-ion technology (~200Wh/kg).
The second invention is to protect the Mg metal anode with a robust and conductive film. In addition to using magnesium borides for anodes, scientists at NREL have invented a conductive coating layer for magnesium metal anodes, using magnesium powder and foil, to prevent the direct contact of Mg and electrolytes. Moreover, the coating layer can work with various aprotic electrolytes, including high-voltage solution and commercial ionic salts such as magnesium perchlorate and Magnesium(II) Bis(trifluoromethane sulfonyl) Imide-Based salts. Thus, the coated Mg-anode can be used in the aprotic solvents containing commercially available ionic salts, which isn’t possible for current Mg-ion batteries. This approach revolutionizes the field, enabling the use of high-voltage cathodes that have been excluded in state-of-the-art Mg-ion batteries and will provide another strategy to solve the bottleneck problem in the current Mg-ion batteries.Benefits
- Enables the use of noncorrosive Mg-ion electrolytes to realize high-energy-density Mg batteries
- Increases safety
- Increases stability
- Increases energy storage capacity
- Magnesium batteries
- Electric vehicles and grid storage
- Advanced electronic devices
|Title and Abstract||
MAGNESIUM-BASED METHODS, SYSTEMS, AND DEVICES
An aspect of the present invention is an electrical device, where the device includes a current collector and a porous active layer electrically connected to the current collector to form an electrode. The porous active layer includes MgB.sub.x particles, where x.gtoreq.1, mixed with a conductive additive and a binder additive to form empty interstitial spaces between the MgB.sub.x particles, the conductive additive, and the binder additive. The MgB.sub.x particles include a plurality of boron sheets of boron atoms covalently bound together, with a plurality of magnesium atoms reversibly intercalated between the boron sheets and ionically bound to the boron atoms.
|National Renewable Energy Laboratory||04/13/2015
|Technology ID||Development Stage||Availability||Published||Last Updated|
|NREL ROI 13-53, 15-55||Proposed||Available||11/20/2015||11/20/2015|