Progress is now rapid in improving lithium rechargeable batteries known as lithium ion. Some are counterintuitive and a big surprise.
Wax and soap reduce cost?
Material scientist Daiwon Choi at the Department of Energy's Pacific Northwest National Laboratory has developed a simple method to turn lithium metal phosphate eg lithium iron phosphate and derivatives, the favourite cathode material, into a better electrode using paraffin wax and soap.
The electrode ingredients were mixed with melted paraffin wax and oleic acid: this let the crystals grow and form themselves into a plate as the temperature reached 400C. When these nano plates were charged and discharged it was found that the LMP mini battery held a little more than 150 mAh/gram of material, higher than other researchers had been able to attain.
A new ternary Sn-Ni-P anode material for Li-ion batteries exhibits high reversible capacity and excellent coulombic efficiency, with an initial discharge capacity and charge capacity of 785.0 mAh g-1 and 567.8 mAh g-1, respectively. After 100 discharge-charge cycles, capacity retention is 94.2% with a value of 534.8 mAh g-1. The electrode performs with an excellent rate capacity.
Another look at manganese
NASA has assigned the NEI Corporation and the University of California (UC San Diego) to develop and implement high energy density nanoscale cathode material for li-ion batteries that could then be used for a variety of space exploration projects as well as for electric vehicle applications. Energy density of more than 1000 Watt-hours per kilogram, double the best today, is thought to be within reach. A commercially useable cathode material with exceptionally high capacity is targeted, potentially giving over 250 mAh/gm at about 4V. Manganese based cathode using better morphology are targeted to save cost but, as the free white paper from IDTechEx "Electric Vehicles:Who is Winning in Lithium-Ion Traction Batteries and Why" details, there are many types of manganese based cathodes in commercial use in traction batteries today, so the new work needs to be very different if they are to give us third generation energy and power density with second generation battery materials.
The researchers from NEI say they will have sample cathode materials for testing by interested end-users by the middle of 2011 and UC San Diego is looking beyond to develop new material that extends the cycle life of EV batteries as well as the driving range of the vehicles they power.
"Lithium batteries for plug-in hybrid electric vehicles or full electric cars have a lot of potential, but we have to work very hard to decrease the dollar per kilowatt hour numbers," said Shirley Meng, professor in the Department of NanoEngineering at the UC San Diego.
"If we are going to use large scale batteries for applications such as electric cars, it is not acceptable to replace batteries every three years. The cycle life of the batteries becomes very important and this is a challenge to address. How do we make batteries last for ten years instead of three years? We have to look for other options for the structure of the battery materials that are more robust,".
Scientists at the Institute of Chemistry at the Chinese Academy of Sciences has developed a clever way to use tin in an electrode. By enclosing nano-sized particles of tin inside elastic hollow carbon spheres, an anode was made with high specific energy capacity and good cycling performance.
A team at Xiamen University (China) has synthesized an anode with a new Sn-Ni-P material that shows promise for use in lithium-ion traction batteries. The new ternary Sn-Ni-P anode material "shows high reversible capacity and excellent coulombic efficiency." The electrode with is mainly composed of pure Sn, Ni3Sn4 and Ni-P phases in the form of Sn-Ni-P alloy rods.
A team at Xiamen University in China has synthesized the alloy rods array electrode by electrodeposition with a Cu nanorods array structured foil as current collector. The Cu nanorods array foil is fabricated by heat treatment and electrochemical reduction of Cu(OH)2 nanorods film, which is grown directly on Cu substrate through an oxidation method. The Sn-Ni-P alloy rods array electrode is largely composed of pure Sn, Ni3Sn4 and Ni-P phases.
Commentators have started to revise their opinion that lithium sulfur rechargeable traction batteries, with their superb energy density, are at least ten years away. After all, ones from Sion Power have lifted a plane aloft and Oxis Energy also has impressive lithium sulfur traction battery technology. NASA has studied advanced lithium batteries driving planes either alone or in conjunction with fuel cells to balance load. Afs Trinity Power Corporation has combined advanced lithium batteries with ultracapacitors in hybrid powertrains.
Financial backing in China
China-based battery manufacturers and suppliers will benefit from government moves promote domestic lithium battery development among domestic manufacturers. Suppliers will attract more orders by increasing expenditure in competitive areas including improving operating efficiency and developing models with greater storage capacity, improved safety features, and less impact on the environment.
As the markets of China battery suppliers recover, including the consumer electronics, mobile phone, computer, toy, power tool and automotive sectors, we are seeing a sharper focus on eco-friendliness. Besides releasing more lithium models as applications for these products grow, manufacturers are implementing better waste-management practices at their factories. With movements for the protection of the environment worldwide, lithium batteries are now a key growth driver in the industry. China suppliers produced 1.9 billion such units in 2009 and output is expected to rise, with the China government promoting lithium battery development nationally in 2010. The China battery industry as a whole is projected to experience annual growth of 20 % or greater over the next few years.
Image Source: Pacific Northwest National Laboratory
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