Dual Substitution Strategy to Enhance Li + Ionic Conductivity in Li 7 La 3 Zr 2 O 12 Solid Electrolyte

Nagata

Akimoto

2018

Sci Rep

103

Today, all-solid-state secondary lithium-ion batteries have attracted attention in research and development all over the world as a next-generation energy storage device. A key material for the all-solid-state lithium batteries is inorganic solid electrolyte, including oxide and sulfide materials. Among the oxide electrolytes, garnet-type oxide exhibits the highest lithium-ion conductivity and a wide electrochemical potential window. However, they have major problems for practical realization. One of the major problems is an internal short-circuit in charging and discharging. In the polycrystalline garnet-type oxide electrolyte, dendrites of lithium metal easily grow through the void or impurity in grain boundaries of the sintered body, which causes serious internal short-circuits in the battery system. To solve these problems, we present an all-solid-state battery system using a single-crystal oxide electrolyte. We are the first to successfully grow centimeter-sized single crystals of garnet-type by the floating zone method. The single-crystal solid electrolyte exhibits an extremely high lithium-ion conductivity of 10−3 S cm−1 at 298 K. The garnet-type single-crystal electrolyte has an advantageous bulk nature to realize the bulk conductivity without grain boundaries such as in a sintered polycrystalline body, and will be a game-changing technology for achieving highly safe advanced battery systems.

Section: Introductionmentioning

confidence: 99%

Lithium-ion conducting oxide single crystal as solid electrolyte for advanced lithium battery application

Nagata

Akimoto

2018

Sci Rep

103

“…Oxide solid electrolytes are further classified into glass, glass‐ceramic, and crystalline types. Crystalline solid electrolytes include LISICON, perovskite, β‐alumina with Na + /Li + ion exchange, and garnet types . Li 7– x La 3 Zr 2– x Nb x O 12 , and Li 7– x La 3 Zr 2– x Ta x O 12 ,,,, in which part of Li 7 La 3 Zr 2 O 12 ,, is substituted with niobium or tantalum, has high lithium ion conductivity and a wide potential window.…”

Section: Introductionmentioning

confidence: 99%

“…Li 7– x La 3 Zr 2– x Nb x O 12 , and Li 7– x La 3 Zr 2– x Ta x O 12 ,,,, in which part of Li 7 La 3 Zr 2 O 12 ,, is substituted with niobium or tantalum, has high lithium ion conductivity and a wide potential window. Recently, many reports have shown that the Li 7 La 3 Zr 2 O 12 of garnet solid electrolytes partially replaced with Ga and/or Sc and Al has high ionic conductivity on the order of 10 −3 ,,. Previously, we reported for the first time that single crystals of garnet type solid electrolyte can be grown by the floating zone (FZ) method which is one of melting methods .…”

Section: Introductionmentioning

confidence: 99%

High Ionic Conductor Member of Garnet‐Type Oxide Li_6.5La₃Zr_1.5Ta_0.5O₁₂

Akimoto

2018

ChemElectroChem

Single‐crystal rods of Li6.5La3Zr1.5Ta0.5O12 were grown by floating zone melting. The typical size of the single‐crystal rod was 8 mm in diameter and 70 mm in length. Li6.5La3Zr1.5Ta0.5O12 crystallizes in a cubic structure with an Ia‐3d space group and the lattice parameter a=12.9455 (6) Å. The crystal structure of Li6.5La3Zr1.5Ta0.5O12 was refined to the conventional values of R=3.32 % and wR=4.45 % using single‐crystal X‐ray diffraction data, and to R=8.82 % and wR=7.45 % using single‐crystal neutron diffraction data. Li‐ions in the crystal structure occupied two crystallographic sites: the distorted tetrahedral 96 h site and the distorted octahedral 96 h site. Analyzing the results of AC impedance measurements, we estimated the total Li‐ion conductivity of member in Li6.5La3Zr1.5Ta0.5O12 to be 1.27×10−3 S cm−1 at 298 K. This value is the highest in the reported Li6.5La3Zr1.5Ta0.5O12 members. Using NMR spectroscopy, we determined the Li diffusion coefficient to be 1.57×10−13 m2 s−1 at 298 K and 7.96×10−13 m2 s−1 at 333 K. These values related to Li‐ion migration are higher than those reported for polycrystalline samples.

“…Recently, components with high denseness have been fabricated by electric current sintering and hot press methods, and there are reports of lithium ion conductivity of 10 -3 S/cm order. [20]- [22] Although the denseness of components is increasing, there are also new reports of internal shortcircuiting. [3][6] [12][13] [15] The problem of internal short-circuits is that short-circuits occur between positive and negative electrodes due to precipitation of lithium metal within an allsolid-state lithium secondary battery.…”

Section: Garnet-type Lithium Solid Electrolytementioning

confidence: 99%

Development of a compact all-solid-state lithium secondary battery using single-crystal electrolyte

Synthesiology English edition

Akao

Nagata

et al. 2019

secondary battery. [1]-[3] According to the NEDO roadmap for FY 2013 in Japan, an all-solid-state battery is positioned as a product that fully covers the potential of a next-generation battery, and is set for practical utilization in 2030. [4] The conventional lithium secondary battery is roughly composed of four parts: a positive electrode, a negative electrode, an electrolyte, and a separator that separates the positive and negative electrodes. On the other hand, an all-solidstate lithium secondary battery is composed of three parts: a positive electrode, a negative electrode, and a lithium solid electrolyte (a lithium ion conductor), and the lithium solid electrolyte plays the roles of both an electrolyte and a separator. Figure 1 shows a schematic diagram of a conventional liquid-state lithium secondary battery and an all-solid-state lithium secondary battery. While the materials for positive and negative electrodes in conventional liquidstate lithium secondary batteries can be used in all-solid-1 Introduction Current situation of next-generation lithium secondary batteryLithium secondary batteries that possess high energy density are used in automobiles and various small electronic devices such as smartphones, and have become power source devices that cannot be separated from life in modern society. Recently, the required specifi cations for secondary batteries have shifted keeping balance with other electronic devices. The current liquid-state secondary batteries are running into problems that cannot be solved, such as high capacity, high voltage, long life, and high energy density. As post-lithium secondary batteries, there is R&D for various new secondary batteries such as lithium air batteries that use air for counter electrodes as well as secondary batteries that use sodium and magnesium as transfer ions. The most leading candidate for new secondary batteries is an all-solid-state lithium -Towards realizing oxide-type all-solid-state lithium secondary batteries-All-solid-state lithium secondary batteries are attracting attention as a next-generation technology. To realize this technology, it is important to develop a new solid-state lithium-ion conductor. In this regard, we discuss the development of all-solid-state secondary lithium batteries using single-crystal solid electrolytes and the AD method. Development of a compact all-solid-state lithium secondary battery using single-crystal electrolyte Fig. 1 Comparison of composition of current lithium secondary battery and allsolid-state lithium secondary batteryResearch paper : Development of a compact all-solid-state lithium secondary battery using single-crystal electrolyte (K. KATAOKA et al.) − 30 −