Columbia University, an assistant professor of materials science and engineering college Yang Yuan developed a new way to improve energy density lithium ion batteries. He three layer structure of the electrode can remain stable in the bare air environment, and thus make the battery more lasting and further reduce the manufacturing cost. The energy density of lithium batteries can be increased 10-30%, related papers in early October, published in the journal Nano Letters.

Graphite/PMMA/Li three layer electrode in the battery electrolyte soaked for 24 hours before (left) and after (right). Before immersed in electrolyte, three layer electrode is stable in the air. After soaking, lithium reaction with graphite, the color yellow.

"When the lithium battery charge for the first time, they lost in the first cycle up to 5-20% of the energy", Yang Yuan said, "through the improvement of the structure, we have been able to avoid this kind of loss. At the same time, our method has great potential, in terms of increasing battery life is expected to be used in portable electronic devices and electric vehicles."

After being produced during the first charge would be part of the lithium battery electrolyte as the reduction reaction, from a liquid into a solid, and adhere to the cathode of the battery. This process is irreversible, reduces battery stored energy.

Under the existing electrode manufacturing technology, it is a process to take losses of about 10%, but for the next generation of high capacity anode materials, such as silicon, loss will be 20-30%, this is will reduce the actual capacity of the battery.

To compensate for the initial loss, the traditional way is to add some rich lithium in electrode materials. However, because most of this kind of material in the air environment is not stable, so must be made in completely no moisture in the dry air, thus greatly increased the manufacturing cost of the battery.

Yang Yuan development of the three layers of the electrode structure is to ensure that the electrodes can complete manufacturing under the ordinary air environment.

First of all, he USES a layer of "PMMA" (that is, the common organic glass materials), lithium to cut off contact with air and water; Then add a layer of artificial graphite on PMMA polymer or silica nanoparticles such as active material; Finally, he let PMMA polymer layer dissolved in electrolyte battery, which will be conducting lithium and electrode materials.

Yang Yuan explained: "so that we can avoid the instability of the air between lithium and lithium electrode contact. Adopting the structure of the electrode can be done in the general air environment, easier to achieve volume production of battery electrodes."

Three layers structure of electrode production process: PMMA in the initial state to ensure lithium will not react with moisture in the air. After the PMMA by battery electrolyte solution, graphite contact with lithium to compensate for initial loss caused due to the reduction of electrolyte.

Yang Yuan methods will existing graphite electrode loss reduced from 8% to 0.3%, the silicon electrode loss reduced from 13% to 15% (negative said due to add the new lithium materials, lead to the capacity of the battery instructs the initial state, and the increased). Excess capacity loss of lithium can compensate then loops, so it can further enhance the cycle life of the battery.

Energy density of lithium ion battery (or capacity) in the past 25 years has been maintained a 5-7% annual growth rate, and Yang Yuan research results to further improve the growth provides feasibility plan. His team is trying to reduce the thickness of the PMMA coating now, in order to reduce its are lower proportion of lithium battery, and try to realize industrial production.

Hai-liang wang, assistant professor of chemistry at Yale university said: "three layer electrode structure design is very clever, can under the ordinary air environment in the production of lithium metal electrodes. The electrode of the initial coulombic efficiency has always been a big problem in the lithium ion battery industry, so this kind of simple and effective compensation technology is bound to arouse people‘s great interest."