Date: Jun 19, 2014 Source: Green Car Congress (
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The US Department of Energy (DOE) has six recently launched applied battery research (ABR) projects as part of its Vehicle Technologies portfolio. ABR, noted Peter Faguy, the DOE manager of the applied battery research program, during his presentation at the Annual Merit Review in Washington, DC, is the difficult regime between the discovery of materials and their application in batteries that can be commercialized.
The objective of the projects is to develop cells that provide more than 200 Wh/kg energy density, along with long cycle life and excellent abuse tolerance to enable 40-mile-range plug-in hybrid (PHEV) and electric vehicles (EVs). One common attribute of all the projects is the use of some form of silicon-based material for the anode. The projects end in 2015.
Argonne National Laboratory. A team led by Argonne National Laboratory and including Brookhaven and Lawrence Berkeley National Laboratories and the University of Utah, is developing a new high energy redox couple (250 Wh/kg) based on a high-capacity full gradient concentration cathode (FCG) (230 mAh/g) (earlier post) and a Si-Sn composite anode (900 mAh/g). Project funding is $2.5 million.
The FCG cathode material consists of lithium transition-metal oxide particles with the nickel concentration decreasing from the center towards the outer layer and the concentration of manganese increasing accordingly. Argonne received a patent on the material, reported in a paper in the journal Nature in 2012, last year.
The Argonne team is currently engineering anodes based on 50 wt% SiO-50 wt% Sn30Co30C40 and a conductive polymer binder (PFFOMB). Later this year, the researchers will finalize the optimization of a Gen 1 FCG cathode, and then bring the components together with a fully or partially fluorinated electrolyte in a Gen 1 cell.
Among the challenges the project faces are reduce the irreversible loss of the anode material and demonstrating 1,000 cycles, and improving the FCG cathode capacity to 220~230mAh/g at high voltage (4.4V and 4.5V).
TIAX. TIAX is the sole organization in a $2.2-million project to combine TIAX's proprietary CAM-7 cathode material (earlier post) with a blended Si/carbon anode to achieve >200 Wh/kg and >400 Wh/L energy and >800 W/kg and >1600 W/L 10s pulse power targets under USABC PHEV battery testing procedures.
CAM-7 is a stabilized, high-nickel cathode material that combines high energy content with high power capability. The material is currently in various stages of sampling at major companies in Korea and Japan for both portable electronics and vehicle applications. CAM-7 has been evaluated in high energy and high power cell designs both at TIAX and by other companies.
TIAX has implemented CAM-7 in high energy 18650 cells with graphite anodes that can deliver 2.7 Ah and 247 Wh/kg.
TIAX proposes that using a blended Si/hard carbon anode will allow the design of cells capable of delivering high energy during EV operation and high power during HEV mode of the battery. More specifically, a blended Si/hard carbon anode with >1000 mAh/cc will enable meeting pulse power targets, while exceeding the energy density of graphite cells.
Binder selection and electrolyte formulation can significantly impact silicon based anodes; accordingly, TIAX will work to optimize those to meet the life targets.
On the cathode side, TIAX will focus on further improving the high temperature cycle life of CAM-7.
3M. The 3M-led project, which includes Umicore, Army Research Laboratory, Berkeley Lab, Leyden Energy and GM Research and Development, is receiving $3 million in DOE funding. The basic approach is to combined a high-capacity Silicon alloy anode with a high energy NMC cathode and advanced electrolyte.
The team seeks to develop the high capacity Si alloy with a stable microstructure using an innovative conductive binder. Targets include a 20% increase in mAh/g and a 10% increase in mAh/cc.
On the NMC material side, 3M has identified a material composition with reduced irreversible capacity; the team is also examining other compositions.
Envia. Envia is leading a $3.8-million project that includes Lawrence Berkeley and Oak Ridge National Laboratories and General Motors. Envia has licensed Lithium-rich Layered-Layered Li2MnO3·LiMO2 composite patents from Argonne National Laboratory, and has developed HCMR (High Capacity Manganese Rich) cathodes based on these layered-layered composite structures.
Envia tailors HCMR based on the application (e.g., hybrid, pug-in hybrid or EV) using particle morphology, composition and nanocoatings. With one HCMR type in production (XP), Envia has two others in R&D (XE and XLE). In the ABR program, Envia is currently using an HCMR XLE cathode (240~280 mAh/g). While HCMR offers high capacity and safety and low cost, it can be challenged by high DC-Resistance, voltage fade upon cycling and poor durability.
The team plans to integrate the HCMR cathode material with a Si-C anode. Envia's anode material will be paired with LBNL's conductive binder to enable the long cycle and calendar life meeting ABR PHEV goals.
Penn State/University of Texas at Austin. The Penn State/U Texas project is a $2.4-million effort that includes EC Power, and Argonne and Lawrence Berkeley National Laboratories and that targets a high-energy, high-power cell for EV applications.
The team is designing a cell with a layered oxide cathode and advanced silicon alloy-carbon anode with optimized binders and electrolyte. Performance targets include 2.5 Ah cells with 330 Wh/kg and 1600 W/L, with more than 500 cycles of life, and excellent safety characteristics.
The team reports that it has already developed a silicon-carbon anode with 1500 mAh/g capacity, 95% capacity retention after 100 cycles at C/3, and coulombic efficiency of more than >99%. Work is in progress on a Si-carbon anode with 1900 mAh/g capacity, 95% capacity retention after 300 cycles at C/3, and coulombic efficiency >99.9%.
Work is also underway on two versions of cathode material: surface-coated, Ni-rich layered oxide cathode with 190 mAh/g capacity, 95% capacity retention after 100 cycles at C/3; and surface-coated, Ni-rich layered oxide cathode with 220 mAh/g capacity, and 95% capacity retention after 300 cycles at C/3.
To develop the nickel-rich cathode, the researchers are controlling the composition, microstructure, and morphology through novel synthesis and processing approaches.
Farasis Energy. Farasis is leading a $3.5-million project that includes Argonne and Lawrence Berkeley National Laboratories, Dupont and Nanosys/OneD Material to demonstrate a PHEV40 cell with an energy density of 250 Wh/kg and an EV light duty cell with an energy density 350 Wh/kg that can meet the cycle life goals for those applications.
Farasis' basic concept is that the layered and layered-layered (LL) NCM materials paired against a silicon-based anode offer the greatest potential to meet the PHEV and EV performance goals especially if higher voltage operation can be enabled. However, there are multiple interacting failure mechanisms—high impedance, SOC-dependent impedance, and impedance growth; voltage fade; accelerated capacity loss; low utilization; low tap density; and a wide voltage window that are barriers to LL-NCM achieving the targets.
Farasis' development strategy is based on initial work done by Dr. Chris Johnson at Argonne National Laboratory and continued at Farasis Energy on an ion-exchange synthesis approach. Na-based LL-NCM material is used as a precursor to form Lithium LL-NCM through an ion-exchange process with Lithium (IE-LL-NCM). Composition and synthetic conditions also can be tuned to produce a high voltage spinel component to the LL materials: Layered-Layered-Spinel NCM (LLS-NCM). The ion-exchange approach offers the potential for new structural and performance characteristics that address the barriers.
Layered NCM materials offer good rate capability, high tap density, good stability at moderate voltages, and reasonable average voltage; however, the materials have stability problems at higher voltages. To address this, the Farasis team is looking to surface stabilization and doping.
To enable operation up to 4.7 V, Farasis is seeking to develop high voltage capable fluorinated electrolytes.
