Secure of advanced future battery technology

KETI(Ji-sang Yu, Senior Researcher)
https://korean-electronics.com//inquiryThe Korea Electronics Technology Institute (KETI), an affiliate of the Ministry of Trade, Industry and Energy, has specialized in R&D on electronics and IT over the past 24 years since its establishment in 1991. It has provided technological support to small and medium-sized businesses so that they can have sufficient competitiveness in the country’s focus areas and new industries. The R&D efforts of KETI are based on the actual demand of industries, creativity and convergence, effectively assisting enterprises with their technological innovation. In particular, the next-generation battery research team has carried out an R&D project on lithium ion batteries in close cooperation with small and medium-sized businesses, to develop the proprietary technology for post Li-ion batteries.

Identification of the cause of the deterioration in the nickel
cathode materials develpment of technology for improving

Mobile devices such as smartphones, etc. and electric vehicles need a battery with high energy density in order to increase usage time or mileage. At present, cathode materials used for a lithium ion battery have capacity of 150~160mAh/g, including LiCoO2, LiNi1/3Co1/3Mn1/3O2. Many developers attempt to apply higher nickel content to lithium ion batteries in order to increase the capacity to 170mAh/g or more.
There are a lot of studies and commercialization efforts on the development of nickel-based cathode materials with capacity of 170mAh/g or more, in which nickel accounts for 60% of transition metals or more, but gas-generation and performancedeterioration at high temperatures make it difficult to commercialize the materials. Analysis of deterioration behaviors at high temperatures or high voltage, identification of problems based on the analysis, and development of solutions should take precedence so as to use high-nickel cathode materials for batteries.

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Ji-sang Yu, Senior Researcher

Hence, this project has discovered a deterioration-inhibiting factor by identifying the causes of deterioration, relating to the surface of active materials and bulk characteristics, based on the analysis of deterioration behaviors of high-nickel cathode materials. The newly discovered factor was used for a fundamental solution to deterioration. Using the solution, nickelbased cathode materials can be applied to lithium ion batteries for mobile IT devices and electric cars. In particular, this study is expected to improve significantly the technical understanding of commercial lithium secondary batteries by establishing various methods to identify the relevant problems of the batteries such as analysis of high-nickel cathode materials, interpretation of deterioration behaviors, and so forth.
“Initially, we had considerable difficulties as there was no effective system for coordination and technological cooperation while a large number of institutes participated in the project without systematic analysis on deterioration mechanism, which was needed to apply nickel-based cathode materials to batteries,” said Ji-Sang Yu, senior researcher at KETI (Korea Electronics Technology Institute), who has participated in the project with a number of universities and enterprises specializing in the materials. “But from the 2nd project year, our roles became clearer and interchange smoother, which has led to successful development of the solution to the deterioration of nickel cathode materials.”

Carried out by the division and cooperation of research
works from a number of research institutes

The existing commercial layered cathode materials used for lithium ion batteries, which are mainly cobalt-based materials, are rapidly being replaced by nickel and, it is expected that nickel will account for 40% or more of the total cathode materials by early 2016. Therefore, the technology developed by this project has high value in analyzing and assessing materials, especially in understanding deterioration of lithium ion batteries. In particular, the technology allows researchers to identify if causes of deterioration are from the inside of active materials or from the surface in order to suggest various measures to inhibit deterioration for enterprises specializing in materials and batteries.
This project has been carried out by various institutes such as KETI (Korea Electronics Technology Institute) as well as ECOPRO and PANAX ETEC through cooperation and division of work. The team analyzed real-time transformation of materials using a transmission electron microscope and synchrotron radiation so as to identify the fundamental causes of deterioration in nickelbased cathode materials at high temperatures when applied to batteries. In addition, theoretical simulation of the structural instability of active materials was carried out through ab initio quantum chemistry methods, whose results were compared to those of actual analysis, which helped to clarify the reasons for the instability. Based on these achievements, the team performed analysis and assessment on changes in bulk and surface characteristics of active materials when applied to batteries containing nickel-based cathode materials.
Over the repeated charge/discharge cycle, the internal structure of nickel-based active materials is maintained well without signifi cant changes, but a fi ne crack in the grain boundary keeps growing, which eventually lowers mechanical strength of the materials and then causes deterioration. In addition to this finding, the team developed a surface treatment technology that can prevent residual lithium (which remains from heat treatment) from generating electrolytes and side reaction within a battery.
Application of the technology signifi cantly reduced the residual lithium, and the team could develop electrolyte additives which can inhibit gas generation at high temperatures during storage of batteries. “We’re planning to apply the technology to Li-rich or high-voltage 5V spinel nickel-manganic acid lithium materials with the purpose of realizing higher capacity of 240~260mAh/g,” said Ji-Sang Yu, senior researcher at KETI.

Contributing to the increse of sales of major battery manufacturers

As to the status of lithium ion batteries using nickel-based cathode materials in 2007 LG Chem applied its proprietary high-nickel (50%) cathode materials to 2,200mAh 18650 cylindrical cells for the fi rst time in the Korean market, succeeded in developing high-nickel materials. After 2010, LiNi1/3Co1/3Mn1/3O2, with 33% nickel content began to replace LiCoO2 because of competitive prices (but the discharge capacity of LiNi1/3Co1/3Mn1/3O2 is 155mAh/g, not higher than that of LiCoO2).
Afterward, the success of cathode materials that have 50% nickel content and 165mAh/g discharge capacity has motivated domestic manufacturers (e.g. Umicore Korea, LANDF) to develop new high-nickel (60% or above) materials with 175mAh/g capacity. Such new materials (60% nickel content) meet the requirements of battery manufacturers and buyers in terms of basic performance but swelling and deterioration at high temperatures should be solved.
Accordingly, ECOPRO and PANAX ETEC, specializing in cathode materials and electrolytes, respectively, joined the project in order to develop solutions to the problems. Based on the newly developed technology, ECOPRO has enhanced its cathode materials and is supplying to Panasonic (No. 1 battery manufacturer in Japan) and Samsung SDI (No. 1 in the world) nearly 30t per month with good sales prospects. The Korean market for electrolytes for lithium ion batteries using nickel-based cathode materials is expected to be KRW 31 billion by 2016 and to grow by 6.2% annually on average. Also, the additives developed by PANAX ETEC are expected to increase greatly sales of in the global market.

 

 

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