Elsevier

Journal of Power Sources

Volume 383, 15 April 2018, Pages 150-156
Journal of Power Sources

Flexible interfaces between Si anodes and composite electrolytes consisting of poly(propylene carbonates) and garnets for solid-state batteries

https://doi.org/10.1016/j.jpowsour.2018.02.026Get rights and content

Highlights

  • Flexible interfaces between Si anodes and composite electrolytes are constructed.

  • The SPEs show the conductivity of 4.2 × 10−4 S cm−1 at room temperature.

  • The SPEs greatly alleviate the stress resulting from volume change of Si.

  • The Si/SPE/Li cells exhibit good cycle and rate performance.

Abstract

Flexible interfaces between Si anodes and composite electrolytes consisting of poly(propylene carbonates) (PPCs) and garnets have been fabricated. The solid polymer electrolytes (SPEs) of PPC/garnet/LiTFSI show the conductivity of 4.2 × 10−4 S cm−1 at room temperature. Their combination with the Si layer anodes allows great alleviation of internal stress resulting from the large volume variation during lithiation and delithiation process of Si anodes. As a result, the Si/SPE/Li cells exhibit 2520 mAh g−1, 2260 mAh g−1, 1902 mAh g−1, 1342 mAh g−1 at 0.1 C, 0.2 C, 0.5 C, and 1 C, respectively. Furthermore, with such compatible and stable interfaces of Si/SPE and the LiFePO4 cathodes in solid-state batteries, the specific capacity of 2296 mAh g−1 in terms of Si is obtained, which remains 82.6% after 100 cycles at room temperature and 0.1 C. The results here indicate that constructing of flexible interfaces between Si anodes and SPEs is a promising strategy to develop high performance solid-state batteries.

Introduction

Recently, rechargeable lithium batteries are requested to achieve the increased energy density and the improved safety property in order to satisfy the rapid development of electric vehicles, portable electronic devices, and grid energy storage [1,2]. Under such circumstances, the solid-state lithium batteries (SSLBs), with great potential in enhancement of energy density as well as improvement of safety, have attracted intensive interests [[3], [4], [5]].

One of the key materials for developing SSLBs is the solid polymer electrolytes (SPEs), which have been paid attention since Wright et al. discovered ionic transport of Polyoxyethylene (PEO) complex with alkali metal salts [6]. A great deal of studies have been carried out on improvement of the ionic conductivity, electrochemical window, and high thermal stability for SPEs, including polymer blending [[7], [8], [9], [10]], cross-linking polymer matrices [11,12], incorporation of plasticizers [13], impregnation with ionic liquids [9,14], and doping inorganic fillers [[15], [16], [17], [18], [19]]. Though much progress has been made previously, the problem of lithium dendrite growth though the SPEs is still the challenge for their application in the batteries with the Li metal anodes [20,21]. In contrast, the Si anodes show the high theoretical capacity of 4200 mAh g−1 through alloying Li4.4Si [22]. Little problem of dendrite growth is expected in case of using Si anode. However, very few reports could be found for the combination of Si anodes with the SPEs. Recently, Takada et al. used the amorphous Si anodes in combination with the Li2S-P2S5 based sulphide solid electrolytes, observing the superior rate and cycle performance of the solid-state batteries [23,24]. This implies that the Si anodes in combination with the garnet could also help improve the relevant cell performance, which nevertheless has not ever been reported.

Herein, the interfaces between Si and solid polymer electrolytes (SPEs) based on poly(propylene carbonates) (PPCs) and Li6.4La3Zr1.4Ta0.6O12 (LLZTO) have been fabricated by deposition of the Si layer on the SPEs at 25 °C. The SPEs show the flat surface as well as high ionic conductivity. Introduction of LLZTO powders into the SPEs promotes complete dissociation of lithium salt as well as enhances the migration of Li+, achieving the conductivity of 4.2 × 10−4 S cm−1 at room temperature [25]. Taking advantages of flexible Si/SPE interfaces, the Li/SPE/Si cells exhibit excellent cycle stability and low charge-transfer resistance after 200 cycles. The reason can be attributed to the effective alleviation of internal stress from volume variation during repeatedly lithiation and delithiation progress. It is indicated that the flexible interfaces are more favorable to reduce the effect of the large volume change, in comparison with rigid interfaces. With the sustainable interfaces between the Si anodes and SPEs, the SSLBs with LiFePO4 cathodes exhibit good cycle performance and high capacity retention at room temperature.

Section snippets

Materials preparation

The PPCs (Mv = 5 × 104 g mol−1, sigma-Aldrich) were dried at 60 °C overnight under vacuum prior to the sample preparation. The Li6.4La3Zr1.4Ta0.6O12 (LLZTO) ceramic powders were prepared by conventional solid-state reaction as described in our previous paper [26]. Crushed by planetary ball-milling and high-energy ball-milling, the initial LLZTO particles of approximately 5 μm were reduced to 200 nm. LiTFSI (99.95%, sigma-Aldrich), acetone (Sigma-Aldrich), PVDF (Aladdin), super-p conductive

Results and discussion

The PPCL-SPEs were fabricated by a mechanochemical method, which was widely used to synthesize inorganic and organic compounds [29]. Toxic acetonitrile in conventional solution casting route is replaced by acetone. And the strong ball-milling force accelerates the dissolving speed of PPC, thus the process time being greatly shortened [30].

The cross section SEM of PPCL-SPE in Fig. 1a shows the thickness of the membranes is approximately 70 μm. In our previous work, the PEO/LLZTO composite

Conclusion

The flexible interfaces between the Si anodes and the composite electrolytes consisting of PPC and garnet powders have been constructed. They effectively alleviate the huge stress in the interfaces resulting from the volume change of Si anodes and remain a good contact between Si anodes and SPEs. With such interfaces, the Si/SPE/Li cells show the capacity of 2520 mAh g−1, 2260 mAh g−1, 1902 mAh g−1, 1342 mAh g−1 at 0.1 C, 0.2 C, 0.5 C, and 1 C, respectively. The capacity retention is as high as

Acknowledgments

The authors would thank the financial supports from National Natural Science Foundation of China (Grant Nos. 51532002 and 51771222), National Basic Research Program of China (2014CB921004), “Strategic Priority Research Program” of Chinese Academy of Science (Grant no. XDA09010202), and Natural Science Foundation of Shanghai (17ZR1434600).

References (52)

  • S. Ramesh et al.

    Thermochim. Acta

    (2010)
  • H. Fan et al.

    J. Power Sources

    (2014)
  • H. Walls et al.

    J. Power Sources

    (2000)
  • Z. Wen et al.

    Solid State Ionics

    (2003)
  • K. Vignarooban et al.

    Solid State Ionics

    (2014)
  • Y. Dai et al.

    Electrochim. Acta

    (1998)
  • G. Katsaros et al.

    J. Photochem. Photobiol. Chem. A.

    (2002)
  • Q. Wang et al.

    J. Membr. Sci.

    (2015)
  • L. Yue et al.

    Energy Storage Mater.

    (2016)
  • D. Zhou et al.

    Nano Energy

    (2017)
  • R.A. Huggins

    J. Power Sources

    (1999)
  • R. Miyazaki et al.

    J. Power Sources

    (2016)
  • R. Miyazaki et al.

    J. Power Sources

    (2014)
  • J. Zhang et al.

    Nano Energy

    (2016)
  • Y. Li et al.

    Solid State Ionics

    (2013)
  • F. Du et al.

    J. Power Sources

    (2015)
  • J. Evans et al.

    Polymer

    (1987)
  • H. Huo et al.

    J. Power Sources

    (2017)
  • T.-H. Cho et al.

    J. Power Sources

    (2010)
  • J.H. Ahn et al.

    J. Power Sources

    (2003)
  • V. Baranchugov et al.

    Electrochem. Commun.

    (2007)
  • Y. Fan et al.

    Carbon

    (2013)
  • H. Yamada et al.

    J. Power Sources

    (2017)
  • J.-M. Tarascon et al.

    Nature

    (2001)
  • N. Ohta et al.

    Adv. Mater.

    (2006)
  • M. Armand et al.

    Nature

    (2008)
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