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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><span style='font-size:14.0pt'><o:p> </o:p></span></p><p class=MsoNormal align=center style='margin-bottom:12.0pt;text-align:center'><b><span style='font-size:14.0pt'>UH ChBE Dept. Seminar<br>9:00am-10:00am, Tuesday , February 23, 2016<br>Cemo Hall, room 105</span></b><span style='font-size:14.0pt'><o:p></o:p></span></p><p class=MsoNormal align=center style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;text-align:center'><b><span style='font-size:18.0pt'>Controlling the Surface Chemistry of Electrode Materials for High Energy Rechargeable Batteries<o:p></o:p></span></b></p><p class=MsoNormal align=center style='text-align:center'><b><span style='font-size:14.0pt'>Feng Lin<o:p></o:p></span></b></p><p class=MsoNormal align=center style='text-align:center'><b><span style='font-size:12.0pt'>Lawrence Berkeley National Laboratory<o:p></o:p></span></b></p><p class=MsoNormal><b><span style='font-size:14.0pt'><o:p> </o:p></span></b></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal style='text-align:justify;line-height:115%'><b><u><span style='font-size:14.0pt;line-height:115%'>ABSTRACT:</span></u></b><span style='font-size:14.0pt;line-height:115%'> </span><span style='font-family:"Times New Roman","serif";mso-fareast-language:ZH-CN'>Chemical evolution and structural transformations at the surface of an electrode material influence greatly the key performance metrics of lithium batteries, including energy density, power capability, safety and cycle life. This presentation will discuss how we bridge the design principles of surface chemistry in electrode materials with advanced characterization tools, in pursuit of safer and durable lithium batteries</span><span style='font-family:"Times New Roman","serif"'>. First, </span><span style='font-family:"Times New Roman","serif";mso-fareast-language:ZH-CN'>a </span><span style='font-family:"Times New Roman","serif"'>high-throughput analytical method, based on synchrotron X-ray spectroscopy, is developed to investigate the surface phase irreversibility of lithium ion battery materials, a phenomenon that has been widely observed yet poorly understood. It is found that, in </span><span style='font-family:"Times New Roman","serif";mso-fareast-language:ZH-CN'>the </span><span style='font-family:"Times New Roman","serif"'>technologically important LiNi<sub>1−x−y</sub>Mn<sub>x</sub>Co<sub>y</sub>O<sub>2</sub> cathode materials, surface reconstruction from a layered to a rock-salt structure is </span><span style='font-family:"Times New Roman","serif";mso-fareast-language:ZH-CN'>commonly</span><span style='font-family:"Times New Roman","serif"'> observed under a variety of battery operating conditions, particularly in high energy Ni-rich compositions. This phenomenon </span><span style='font-family:"Times New Roman","serif";mso-fareast-language:ZH-CN'>results in</span><span style='font-family:"Times New Roman","serif"'> poor high-voltage cycling performance, impeding attempts to improve the energy density by widening the potential window at which these electrodes operate. Subsequently, </span><span style='font-family:"Times New Roman","serif";mso-fareast-language:ZH-CN'>both </span><span style='font-family:"Times New Roman","serif"'>experimental and computational approaches, including selective surface metal segregation and aliovalent substitution, are </span><span style='font-family:"Times New Roman","serif";mso-fareast-language:ZH-CN'>developed</span><span style='font-family:"Times New Roman","serif"'> to optimize LiNi<sub>1−x−y</sub>Mn<sub>x</sub>Co<sub>y</sub>O<sub>2</sub> materials. The tailored surface metal segregation (i.e., Mn-rich and Ni-poor) result</span><span style='font-family:"Times New Roman","serif";mso-fareast-language:ZH-CN'>s</span><span style='font-family:"Times New Roman","serif"'> in superior resistance to surface reconstruction compared with those of conventional LiNi<sub>1−x−y</sub>Mn<sub>x</sub>Co<sub>y</sub>O<sub>2</sub></span><span style='font-family:"Times New Roman","serif";mso-fareast-language:ZH-CN'> materials,</span><span style='font-family:"Times New Roman","serif"'> </span><span style='font-family:"Times New Roman","serif";mso-fareast-language:ZH-CN'>due</span><span style='font-family:"Times New Roman","serif"'> to </span><span style='font-family:"Times New Roman","serif";mso-fareast-language:ZH-CN'>the </span><span style='font-family:"Times New Roman","serif"'>minimized unpaired Ni3d-e<sub>g</sub> electrons at the outmost layer of LiNi<sub>1−x−y</sub>Mn<sub>x</sub>Co<sub>y</sub>O<sub>2</sub> materials. On the other hand, an examination of the structural and electronic modifications reveals that aliovalent substitution</span><span style='font-family:"Times New Roman","serif";mso-fareast-language:ZH-CN'> of </span><span style='font-family:"Times New Roman","serif"'>Co<sup>3+</sup> site</span><span style='font-family:"Times New Roman","serif";mso-fareast-language:ZH-CN'>s by</span><span style='font-family:"Times New Roman","serif"'> Ti<sup>4+</sup> </span><span style='font-family:"Times New Roman","serif";mso-fareast-language:ZH-CN'>can largely </span><span style='font-family:"Times New Roman","serif"'>reduce the structural distortions during delithiation</span><span style='font-family:"Times New Roman","serif";mso-fareast-language:ZH-CN'>, which could be ascribed to</span><span style='font-family:"Times New Roman","serif"'> the larger cation radius of Ti<sup>4+</sup> relative to Co<sup>3+</sup> and the presence of an electron polaron on </span><span style='font-family:"Times New Roman","serif";mso-fareast-language:ZH-CN'>the </span><span style='font-family:"Times New Roman","serif"'>Mn cations induced by Ti<sup>4+</sup>. The </span><span style='font-family:"Times New Roman","serif";mso-fareast-language:ZH-CN'>successful</span><span style='font-family:"Times New Roman","serif"'> Ti aliovalent substitution</span><span style='font-family:"Times New Roman","serif";mso-fareast-language:ZH-CN'> in the </span><span style='font-family:"Times New Roman","serif"'>LiNi<sub>1−x−y</sub>Mn<sub>x</sub>Co<sub>y</sub>O<sub>2</sub> </span><span style='font-family:"Times New Roman","serif";mso-fareast-language:ZH-CN'>composite </span><span style='font-family:"Times New Roman","serif"'>lead</span><span style='font-family:"Times New Roman","serif";mso-fareast-language:ZH-CN'>s</span><span style='font-family:"Times New Roman","serif"'> to improved capacity and cycle life</span><span style='font-family:"Times New Roman","serif";mso-fareast-language:ZH-CN'> of</span><span style='font-family:"Times New Roman","serif"'> </span><span style='font-family:"Times New Roman","serif";mso-fareast-language:ZH-CN'>the </span><span style='font-family:"Times New Roman","serif"'>cells.</span><span style='font-family:"Times New Roman","serif";mso-fareast-language:ZH-CN'> This presentation will </span><span style='font-family:"Times New Roman","serif"'>demonstrate the </span><span style='font-family:"Times New Roman","serif";mso-fareast-language:ZH-CN'>great </span><span style='font-family:"Times New Roman","serif"'>importance of controlling surface chemistry</span><span style='font-family:"Times New Roman","serif";mso-fareast-language:ZH-CN'> of cathode materials</span><span style='font-family:"Times New Roman","serif"'> for </span><span style='font-family:"Times New Roman","serif";mso-fareast-language:ZH-CN'>the </span><span style='font-family:"Times New Roman","serif"'>successful development of high-energy lithium batteries. It is expected that </span><span style='font-family:"Times New Roman","serif";mso-fareast-language:ZH-CN'>this</span><span style='font-family:"Times New Roman","serif"'> work </span><span style='font-family:"Times New Roman","serif";mso-fareast-language:ZH-CN'>c</span><span style='font-family:"Times New Roman","serif"'>ould help accelerate the implementation of LiNi<sub>1−x−y</sub>Mn<sub>x</sub>Co<sub>y</sub>O<sub>2</sub> materials in electric vehicles and </span><span style='font-family:"Times New Roman","serif";mso-fareast-language:ZH-CN'>other </span><span style='font-family:"Times New Roman","serif"'>energy storage</span><span style='font-family:"Times New Roman","serif";mso-fareast-language:ZH-CN'> facilities</span><span style='font-family:"Times New Roman","serif"'>.<o:p></o:p></span></p><p class=MsoNormal style='text-align:justify'><span style='font-size:10.5pt;font-family:"Arial","sans-serif"'><o:p> </o:p></span></p><p class=MsoNormal style='text-align:justify;line-height:115%'><b><u><span style='font-size:14.0pt;line-height:115%'>BIO: </span></u></b><span style='line-height:115%;font-family:"Times New Roman","serif"'>Dr. Feng Lin is currently a Senior Member of Technical Staff at a stealth energy company in Silicon Valley, and an affiliate scholar at Lawrence Berkeley National Laboratory (LBNL). In 2013-2015, he performed postdoctoral research in Dr. Marca Doeff’s group at LBNL, on the topics of rechargeable batteries, electrocatalysis and synchrotron core-level spectroscopy. He holds a Bachelor’s degree (2009)</span><span style='line-height:115%;font-family:"Times New Roman","serif";mso-fareast-language:ZH-CN'> </span><span style='line-height:115%;font-family:"Times New Roman","serif"'>in Materials Science and Engineering from Tianjin University, and an MSc degree (2011) and a PhD degree (2012) in Materials Science from Colorado School of Mines. His graduate research was </span><span style='line-height:115%;font-family:"Times New Roman","serif";mso-fareast-language:ZH-CN'>co-advised</span><span style='line-height:115%;font-family:"Times New Roman","serif"'> by Prof. Ryan Richards, Dr. Anne Dillon and Dr. Chaiwat Engtrakul at National Renewable Energy Laboratory and Colorado School of Mines, where he developed multicomponent inorganic materials for electrochromic smart windows and catalysis. Dr. Feng Lin served the electrochemistry community of Northern California as the Chair of the Electrochemical Society-San Francisco Section during 2013-2014 (currently as the Past Chair). In 2015, he received Spicer Young Investigator Award from SLAC National Accelerator Laboratory, and was a finalist of Young Scientists Award of International Society for Solid State Ionics. His research in batteries was selected to the Top 10 Scientific Achievements by Brookhaven National Laboratory in 2014. Dr. Feng Lin is currently serving the Users Executive Committee of Stanford Synchrotron Radiation Lightsource on a 3-year term</span><span style='line-height:115%;font-family:"Times New Roman","serif";mso-fareast-language:ZH-CN'> (2015-2017)</span><span style='line-height:115%;font-family:"Times New Roman","serif"'>. <o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:8.0pt;text-align:justify'><span style='font-size:10.5pt;font-family:"Arial","sans-serif"'><o:p> </o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><o:p> </o:p></p><p class=MsoNormal style='text-align:justify'><span style='font-size:10.0pt;font-family:"Times New Roman","serif";color:black'><o:p> </o:p></span></p><p class=MsoNormal style='text-align:justify;background:white'><b><u><span style='font-size:14.0pt'><o:p><span style='text-decoration:none'> </span></o:p></span></u></b></p><p class=MsoNormal style='text-align:justify;background:white'><b><u><span style='font-size:14.0pt'><o:p><span style='text-decoration:none'> </span></o:p></span></u></b></p><p class=MsoNormal><span style='font-size:10.0pt'><o:p> </o:p></span></p><p class=MsoNormal style='text-align:justify;text-indent:27.35pt;line-height:15.0pt;mso-line-height-rule:exactly'><span style='font-family:"Arial","sans-serif"'><o:p> </o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='font-size:14.0pt'><o:p> </o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='font-size:14.0pt'><o:p> </o:p></span></p><p class=MsoNormal style='margin-right:2.25pt;text-align:justify;line-height:115%'><span style='font-size:14.0pt;line-height:115%'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal style='text-align:justify'><o:p> </o:p></p><p class=MsoNormal style='text-align:justify'><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal style='text-align:justify;text-indent:12.05pt'><span style='font-family:"Franklin Gothic Book","sans-serif"'><o:p> </o:p></span></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p></div></body></html>