{"id":11868,"date":"2018-08-11T23:24:13","date_gmt":"2018-08-12T06:24:13","guid":{"rendered":"http:\/\/cafe.foundation\/blog\/?p=11868"},"modified":"2018-08-11T23:24:13","modified_gmt":"2018-08-12T06:24:13","slug":"lowered-resistance-greater-spontaneity-with-solid-state-batteries","status":"publish","type":"post","link":"http:\/\/cafe.foundation\/blog\/lowered-resistance-greater-spontaneity-with-solid-state-batteries\/","title":{"rendered":"Lowered Resistance, Greater Spontaneity with Solid-State Batteries"},"content":{"rendered":"

Paradoxically, almost every battery breakthrough seems to have an accompanying problem, and battery developers end up sometimes ditching the positive because of an overriding negative.\u00a0 Solid-state batteries promise some gains without compromise, though.<\/p>\n

Conventional lithium-ion batteries have possibly reached the limit of their capacity, some scientists fear, and still remain prone to issues like thermal runaway.\u00a0 Developers have looked at solid-state battery designs in which even the electrolyte is solid and not prone to bursting into flame.\u00a0 These batteries promise to have higher energy densities and longer lives, but high resistance at the electrolyte-electrode interface tends to interfere with charging and discharging speeds.<\/p>\n

Two groups of researchers at the Tokyo Institute of Technology have been taking different approaches to creating a solid-state battery with improved performance and few of the disadvantages of more conventional lithium cells.<\/p>\n

Stacking Battery Components<\/h4>\n

Scientists from Tokyo Institute of Technology and Tohoku University, led by Professor Taro Hitosugi,<\/a> \u201cFabricated all-solid-state batteries with extremely low interface resistance using Li(Ni0.5<\/sub>Mn1.5<\/sub>)O4<\/sub> (LNMO, or Lithium Nickel Manganese Oxide), by fabricating and measuring their batteries under ultrahigh vacuum conditions, ensuring that the electrolyte\/electrode interfaces were free of impurities.\u201d<\/p>\n

Researchers used X-ray diffraction and Raman spectroscopy to characterize electrochemical properties of the batteries by analyzing the crystal structure of the batteries\u2019 thin films.\u00a0 They found \u201cspontaneous migration of lithium ions from the Li3PO4 (Lithium Phosphate) layer to the LNMO layer, which converted half the LNMO to L2NMO at the Li3PO4\/LNMO interface.\u00a0 This migration reverses during initial charging to regenerate LNMO.\u201d<\/p>\n

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The batteries were made by stacking various layers via thin-film deposition methods. The LNMO\/Li3PO4 interface showed spontaneous migration of Li ions and had an unprecedentedly low resistance.\u00a0\u00a0Illustration: ACS Applied Materials & Interfaces<\/em><\/p><\/div>\n

Researchers tested the impedance of the cells using electrochemical impedance spectroscopy.\u00a0 Resistance \u201cwas 7.6 \u03a9 cm2<\/sup>, two orders of magnitude smaller than that of previous LMNO-based all-solid-state batteries and even smaller than that of liquid-electrolyte-based Li-ion batteries using LNMO.\u201d\u00a0 These batteries also charged and discharged faster, \u201cmanaging to charge\/discharge half the battery within just one second.\u201d\u00a0 They\u00a0 also showed \u201cno degradation in performance even after 100 charge\/discharge cycles.\u201d<\/p>\n

The team\u2019s paper was published in ACS Applied Materials & Interfaces<\/em>.<\/a><\/p>\n

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Performance of the fabricated all-solid-state batteries.\u00a0\u00a0The (a) charge-discharge curves…<\/p><\/div>\n

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…and the (b) cycling performance plot show that the performance of the fabricated all-solid-state batteries did not degrade after repeated use, demonstrating their excellent stability and the total reversibility of the reactions involved in charging\/discharging.<\/p><\/div>\n

Li(Ni0.5<\/sub>Mn1.5<\/sub>)O4<\/sub> is a promising material to increase the energy density of a battery, because the material provides us of a higher voltage. The research team hopes that these results will facilitate the development of high-performance all-solid-state batteries, which could revolutionize modern portable electronic devices and electric cars.<\/p>\n

Professor Kanno’s Canned Energy<\/h4>\n

A second group at Tokyo Tech, led by Professor Ryoji Kanno <\/a>of the Department of Electronic Chemistry, Interdisciplinary Graduate School of Science and Engineering, also works on solid-state batteries.<\/p>\n

Currently, Kanno is mainly focusing his energy on the development of all-solid-state batteries, which dispense with the liquid electrolyte that is part of even so-called dry cells.\u00a0 The organic solvents that act as electrolytes in many lithium batteries are combustible, a big safety concern \u2013 especially in aircraft.<\/p>\n