Contents lists available at ScienceDirect Journal of Energy Storage journal homepage: www.elsevier.com/locate/est Constructing an interface compatible Li anode in organic electrolyte for solid-state lithium batteries Xiaolin Sun a , Quanhai Niu a , Depeng Song a , Shimei Sun a , Minmin Li a , Takeo Ohsaka b , Futoshi Matsumoto b , Jianfei Wu a, ⁎ a Qingdao Industrial Energy Storage Research Institute, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, No. 189 Songling Road, Qingdao, 266101, China b Research Institute for Engineering, Kanagawa University, Kanagawa-Ku, Yokohama, 221-8686, Japan ARTICLE INFO Keywords: Solid-state lithium batteries Lithium metal Li 10 GeP 2 S 12 Solid electrolyte interphase Electrochemistry ABSTRACT To obtain high energy solid-state lithium batteries (SSLB), matching solid electrolyte with lithium metal remains a challenge due to the lack of stable contact on the solid electrolyte/lithium interfaces. Herein, a lithium metal anode modified by solid state electrolyte interphase (SEI) was prepared to assemble SSLB. XPS results show the components of SEI layer contain LiCO 3 , LiF and ROCO 2 Li, which play a role in stabilizing the interface. At a current density of 0.1 mA cm -2 , the Li (M)/Li 10 GeP 2 S 12 (LGPS)/Li (M) symmetric cell has cycled with a small polarization for 500 h. And the Cyclic voltammetry of Li (M)/LGPS/Au also proves the interface stability. The coin cells assembled with SEI modified Li anode, LGPS, and LiNi 0.8 Co 0.15 Al 0.05 O 2 (NCA) cathode show a large initial discharge capacity of 117.6 mAh g -1 and good cycle performance, capacity retention of 77.6% after 100th cycles. The SEI layer formed in the organic electrolyte is applied to SSLB, providing the possibility for the combined development of organic and solid state batteries. 1. Introduction Lithium ion batteries (LIBs) have undergone rapid development over the past 20 years. Graphite is a primary anode material used in LIBs because of its reasonable price, high capacity retention and cycle stability. However, with the increasing demand for high energy density and high safety, traditional LIBs have their inherent drawbacks espe- cially in the energy density, limiting their use in the electric vehicle industry. In order to obtain high specific energy, an effective strategy is to replace conventional anode with lithium metal, the theoretical spe- cific capacity of which can reach to 3860 mAh g -1 and the standard electrochemical potential of which is -3.04 V(vs. hydrogen electrode) [1,2]. Nevertheless, lithium, a highly active metal, reacts with almost all the chemical substances in organic electrolyte, resulting in lower coulombic efficiency and higher interface impedance. In addition, large current density and heterogeneous deposition tend to induce dendrite nucleation, leading to short circuits, fires or explosions. Great efforts have been made to prevent these problems from happening. Among them, replacing organic electrolyte with solid electrolytes is considered an effective method in LIBs [3–5]. However, although lithium can theoretically be used in all kinds of solid state batteries (SSLB) [6–8], many experiments have proven that an unstable interface between solid electrolyte and lithium metal still exists. Popular electrolytes of per- ovskite-type, NASICON and thiophosphates are all unstable with li- thium metal, but easy to form interphases [9–11]. Recent researches [12–14] show that the interface of lithium metal/solid electrolyte can be classified into three types: reactive and metastable interphase, re- active and mixed conducting interphase, and non-reactive and ther- mally stable interface. The interface of sulfide solid electrolyte/lithium metal belongs to the first type, which is unfavorable for the high per- formance SSLB [13–15]. For example, the sulfide solid electrolyte Li 10 GeP 2 S 12 (LGPS) exhibits high ionic conductivity. But when used in conjunction with lithium metal, LGPS is easily reduced by lithium to form lithium sulfide and lithium phosphate. At the same time, due to the reduction of lithium, the structure of LGPS changes, resulting in uneven deposition of lithium. Therefore, it is urgent to develop new methods or new materials to improve the interface stability of lithium metal/solid electrolyte, such as artificial electrode/electrolyte films [16,17], hybrid electrolytes [18,19], Li-Al alloys, Li-In alloys, or Li-Au alloys [20–22]. As is known to all, solid electrolyte interphase (SEI) formed on the surface of the anode during the initial charging cycle shows electrical insulation and ionic conductivity [23,24]. These characteristics of SEI can contribute to stabilizing the interface and inhibit dendrite https://doi.org/10.1016/j.est.2019.101142 Received 16 September 2019; Received in revised form 2 December 2019; Accepted 6 December 2019 ⁎ Corresponding author. E-mail address: wujf@qibebt.ac.cn (J. Wu). Journal of Energy Storage 27 (2020) 101142 2352-152X/ © 2019 Elsevier Ltd. All rights reserved. T