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A new class of LAGP-based solid polymer composite electrolyte for efficient and safe solid-state lithium batteries Qingpeng Guo, Yu Han, Hui Wang, Shizhao Xiong, Yujie Li, Shuangke Liu, and Kai Xie ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.7b12092 • Publication Date (Web): 13 Nov 2017 Downloaded from http://pubs.acs.org on November 14, 2017

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ACS Applied Materials & Interfaces

A New Class of LAGP-based Solid Polymer Composite Electrolyte for Efficient and Safe Solid-State Lithium Batteries Qingpeng Guo*, Yu Han*, Hui Wang, Shizhao Xiong, Yujie Li, Shuangke Liu and Kai Xie College of Aerospace Science and Engineering, National University of Defence Technology, Changsha, Hunan, 410073, China.

ABSTRACT Inorganic solid electrolytes (SEs) possess substantial safety and electrochemical stability, which make them as key components of the safe rechargeable solid-state Li batteries with high energy density. However, complicated integrally molding process, the poor wettability between SE and active materials are the most challenging barriers for the application of SEs. In this regard, we explore composite SE of the active ceramic Li1+xAlxGe2-x(PO4)3 (LAGP) as the main medium for ion-conducting and the polymer P(VDF-HFP) as matrix. Meanwhile, for the first time, we choice high chemical, thermal and electrochemical stability of ionic liquid swelled in polymer, which significantly ameliorate the interface in the cell. In addition, reduced crystallinity degree of the polymer in electrolyte can also be achieved. All of these lead to good ionic conductivity of the composite electrolyte (LPELCE), at the same time, good compatibility with lithium electrode. Especially, high mechanical strength and stable solid electrolyte interphase (SEI) which suppressed the growth of lithium dendrite, and high thermal safety stability can also be observed. For further illustration, the solid-state lithium battery of LiFePO4/LPELCE/Li shows relatively satisfactory performance, indicating the promising potentials of using this type of electrolyte to develop high safety and high energy density solid-state lithium battery. Keywords: Solid composite electrolyte; Flexible membrane; Ionic liquid; Nonﬂammable; Compatibility; Ionic conductor.

1．．Introduction The development of electronic products and electric vehicles has greatly

*Corresponding author. Tel.: +86-0731-84573149, fax: +86-0731-84573149. E-mail addresses: [email protected] ( Q, Guo ), [email protected] ( Y, Han ).

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promoted developing of the electrochemical storage as power storage systems1-3. Currently, lithium-ion batteries (LIBs) with liquid organic electrolytes (LOEs) have dominated the portable electronics market, however, the potential security issues of LOEs restrict their widespread applications in the new type high-power and high-capacity batteries4-7. Exploring solid-state electrolytes can address the issue of battery safety. Despite the fact that inorganic solid electrolytes always have high conductivity at room temperature, good thermal stability and wide electrochemical stability, this type of electrolyte still has some problems such as complicated integrally molding process, the poor wettability between the electrode material and electrolyte5,8-10. Solid polymer electrolytes (SPEs) can also have excellent film forming process with good wettability and low flammability, however, the practical use of SPEs are severely impeded by its relatively low ionic conductivity at room temperature (10-7~10-8 S cm-1) for the inherently high polymer crystallinity degree6. Therefore, based on the characteristics and defects of the two types of solid electrolytes, several alternative strategies7-12, such as exploring composite solid electrolyte of the active ceramic as the main medium for ion-conducting and the polymer as film formers, have been researched. Active ceramic fillers themselves have high ionic conductivity and the ceramic particles as cross-linking centers can successfully suppressed the degree of polymer crystallinity. Moreover, since the transition phase is formed between ceramic particles and polymer, better ion transmission can be achieved, and the large specific surface area of ceramic fillers can enhance salt dissociation, which also enhance the overall performance of the


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composite solid electrolyte7,8. Whereas large amounts of crystallized polymers regions still exist in the composite solid electrolyte, together with agglomeration of ceramic particles6,13-15. Thus, it is generally believed that further improving the ionic conductivity is still a challenge16-19. To address these concerns, we put forward a strategy to prepare "firmness and flexibility" composite laminate electrolyte via combining ceramic particles Li1+xAlxGe2-x(PO4)3 (LAGP) with polymer P(VDF-HFP), and add serve ionic liquid (room temperature molten salt with high safety) into composite electrolyte as plasticizers (LAGP-P(VDF-HFP)-EMITFSI-LiTFSI composite electrolyte, referred to as LPELCE), which can provide high ionic conductivity and ameliorate the interface between electrode and solid electrolyte. Through a systematic and comprehensive experiment, we can see that the prepared composite electrolyte combines the advantages of both the inorganic solid electrolyte (with mechanical stability, electrochemical stability, high thermal stability) and the polymer electrolyte (with good film forming process). The great attention is that LPELCE can increase compatibility to lithium anode which suppressed the growth of lithium dendrite. Thus, with all the benefits of the electrolyte, these can establish the theoretical and technological foundation for the development of a safe, reliable, good overall performance of solid-state lithium battery. 2. Experimental Section Preparation of inorganic electrolytes LAGP powder: The four materials of Li2CO3, GeO2, Al2O3 and NH4H2PO4 were weighed in a agate jar by the stoichiometry



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and grinded evenly, then they were heated to 700℃ and kept for 1 h in a platinum crucible. Subsequently, the mixture was heated up to 1500℃ with 5℃ min-1 heating rate and melted for 2 h. The homogenous lava was quenched in water to obtain glass blocks. The glass block was placed in a tube furnace and heated at 850℃ for 12 h, then cooled to room temperature naturally and got LAGP glass-ceramic blocks. Finally, the glass-ceramic blocks were experienced in milling for 8 h in zirconia jar, screening particles size between 850~950 nm to obtain fine powder (see Figure S1), which were dried under vacuum at 120℃ for 24 h spare to use. LPELCE synthesis: An appropriate amount of P(VDF-HFP) was dissolved in 1-Methyl-2-pyrrolidone (NMP) and magnetic stirred for 30 min at room temperature to obtain 6.7 wt% of polymer clear solution. Then appropriate ratios of LAGP powder, lithium salt and ionic liquid (the values of mPVDF-HFP:mLiTFSI:mEMITFSI:mLAGP changed from 5:5:7:5 to 5:5:7:9) were added to the solution in an argon filled glovebox. The mixed solution was continuously stirred for 3 h and still standing for 20 min to obtain a homogeneous casting solution. The mixed solution was cast onto a teflon mold to obtain composite electrolyte films. At last, the films were kept in vacuum oven at 100℃ for 24 h to completely remove the solvent. Characterization: The morphology, microstructures and phase were characterized by HITACHI S-4800 scan electron microscopy (SEM), X-ray power diffraction (SIEMENS D-500, 2θ=10°~70°) respectively. Thermal properties were implemented by 209 TG F1 with a heating rate of 10°C min-1 under N2 atmosphere. The thermal safety performance-


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values of limiting oxygen index (LOI) of electrolytes were measured by Atlas Limiting Oxygen Index Chamber. Thus, the lowest percentage of O2 in the mixed gas which allows the test samples to burn out reflecting the value of LOI. Electrochemical Measurements: The solid composite electrolyte was sandwiched between two stainless steel (SS) electrodes in a blocking type cells, then the ionic conductivities of LPELCEs were measured by electrochemical impedance spectroscopy (EIS) at various temperatures (25~100℃), with AC amplitude of 10 mV from 0.01 to 105 Hz. Ionic conductivity (σ) was calculated by the formula: σ = d/(Rb·S). The electrochemical stability of the LPELCE was measured by linear sweep voltammetry (LSV) with the cell structure of Li/LPEL/SS at the scanning rate of 0.1 mV S-1 from voltage 0 to 6 V. The cyclic voltammetry (CV) was performed at a sweep rate of 0.1 mV S-1 between -3 to 3 V using symmetric Li/Li cell. The symmetric Li/Li analog battery with electrolyte was used to evaluate stability between electrolyte and Li electrode. A current density of 0.2 mA cm-2 was applied to promote lithium plating/stripping on the Li electrode at 25 ℃. The cycled battery disassembled in an Ar-ﬁlled glovebox, the removed lithium electrode washed by solvent of DMC and dried in vacuum for 12 h as the samples for SEM or XPS test. The LiFePO4 electrode was prepared by the mixed slurries coated on Al foils, the slurries contain LiFePO4 powders, carbon black and P(VDF-HFP) which was contained in ingredient of LPEL at 8:1:1 weight ratio in N-methylpyrrolidone (NMP) solvent. The composite cathode was dried in a vacuum oven for 12 h. The loading



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density of LiFePO4 cathode was controlled to be 2.2 mg cm-2. Li/LPEL/LiFePO4 coin cells were assembled as the solid-state batteries, the charge-discharge testing was conducted in the range of 2.7-3.85 V at room temperature, according to the LAND CT2001A. 3. Results and Discussion 3.1 Synthesis and physical characterization of electrolyte

Figure 1．Schematic illustration for the synthesis of LPELCE and photograph of the membrane.

Figure 1 shows a schematic diagram of the reaction steps involved in the synthesis of LPELCE. LAGP nano-particles were prepared by the method of solid phase reaction and then filtered to obtain the powder (for details, see experimental methods). X-ray diffraction (XRD) patterns of LAGP powder (Figure 2a) show that the diffraction peak position is consistent with the NASICON LiGe2(PO4)3 (JCPDS 80-1924) structure. Meanwhile, a number of glass-ceramic continuous phases were examined by scanning electron microscopy (SEM), as shown in Figure 2b. The grains are coated and connected with adhesive phase. There are no obviously grain boundaries, indicating that the successfully formation of the NASICON type of glass ceramic LAGP.


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Figure 2. Phase structure and morphological characterizations of LAGP and LPELCEs: (a) XRD patterns of LAGP. (b) SEM micrographs of LAGP. (c) Surface of L-50%-PELCE. (d) Cross-section morphology of L-50%-PELCE. (e) TEM image of L-50%-PELCE. (f) SEM image of LPELCE with 80 wt% LAGP content. (g) XRD patterns of the polymer matrix P(VDF-HFP) and LPELCEs. (h) Strain-stress curves of L-50%-PELCE.

Figure 2c-f indicates the surface topography of LPELCE with various contents of LAGP nano-particles (L-x%-PELCE). SEM micrographs of the composite electrolyte with 50 wt% LAGP in Figure 2c (surface) and Figure 2d (cross-section) clearly show that

nano-particles

are

uniformly

embedded

inside

gel

state

of

P(VDF-HFP)-EMITFSI-LiTFSI. Meanwhile, ceramic particles, as a crosslinking center, were wrapped by amorphous tissue of gel polymer. Much more transitional phase can be obtained between ceramic particles and polymer (Figure 2e). In addition, when the content of LAGP is higher than 60 wt% to 80 wt%, the ceramic particles agglomerated easily and gaps appeared between particles, resulting in poor



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film-forming property (Figure 2f). XRD patterns were taken at room temperature for P(VDF-HFP), P(VDF-HFP)-LiTFSI and the composite electrolytes with different content of LAGP (Figure 2g). The bottom curve, which is the spectrum of pure P(VDF-HFP), contains two strong characteristic peaks of crystalline, showing that this polymer has high degree of crystallinity. It also can be seen that, the diffraction peaks of P(VDF-HFP) can be weakened by the complexation between LiTFSI and P(VDF-HFP), but not obvious. A dramatic reduce on peak intensity can be observed with the increase of LAGP. When the content of LAGP is more than 50% and further increase, notably, polymer shows almost indiscernible characteristic peaks, characteristic peaks of solid composite electrolyte are consistent with pure LAGP characteristic spectrum peak. The polymer crystallization regions are squeezed by LAGP amorphous area, making neat molecular chains in crystal district become more disordered, which implies that LAGP can reduce the degree of crystallinity of P(VDF-HFP). On the other hand, ionic liquid swells molecular chains of P(VDF-HFP) make it almost in the amorphous state. Meanwhile, a solid polymer electrolyte must have sufficient mechanical strength for practical use, therefore, the mechanical strength is also one of an important indicator to evaluate the merit of electrolyte membrane. Figure 2h is a demonstration of mechanical properties of L-50%-PELCE. It can be seen that the electrolyte showed a certain mechanical properties with a tensile strength of 4.90 MPa and a Young’s modulus of 13.96 MPa. Thus we can say that the special mechanical properties and tenacity of L-50%-PELCE can easy to film during production process and effectively


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mitigate dendrite penetration while used it in lithium batteries6,20-22. 3.2 Thermal safety analysis Figure 3a lists four main components of polymeric based electrolytes. Among these, only ionic liquids and inorganic solids are non-flammable, which reflect good thermal stability3,23,24. Here we select inorganic solid as a main component of composite electrolyte and add a small amount of ionic liquid as the modifier, its main purpose is to make an electrolyte with good thermal stability and electrochemical performance. Thus, TGA and flammability tests are implemented to describe thermal safety stability of LPELCE. The TGA curves of L-50%-PLCE (without ionic liquid in composite electrolyte) and L-50%-PELCE show two different processes taking place within the sample during the heating (Figure 3b). Before 300℃ a small portion loss of mass can be observed, it is noteworthy to mention that the weight loss of electrolyte is nearly from lithium salt and polymer; a second degradation process takes place above 300℃, which is related to the decomposition of ionic liquid. These results confirm that LAGP and ionic liquid showed the intrinsic thermal safety and improve thermal stability of electrolyte. Flammability tests for Celgard membrane, L-50%-PLCE and L-50%-PELCE ones are depicted in Figure 3c. The commercial Celgard membrane is ignited easily once in contact with the flame and quickly burned off into ashes. Low-flammability is observed for the L-50%-PLCE membrane, and there are many pores left in the membrane after amount of polymer component is gone. In comparison, no flammability is observed for the L-50%-PELCE even upon prolonged the ignition time with an acetylene flame where the outer flame temperature is up to 1300℃, which proved that LPELCE can enhance the safety of



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solid-state lithium batteries. In addition, to further description the flame retardant degree of the solid polymer composite electrolyte, the limiting oxygen index (LOI) test was administered, which is an useful method to quantitatively evaluate the minimum concentration of oxygen to judge whether a substance is flammable25. Figure 3d shows the LOI values of different electrolytes, generally, the value higher than 27 indicate the material is flame retardant26. Thus, we can say that the L-50%-PLCE exhibits flame retardant, and with the addition of ionic liquids, the LOI value of the L-50%-PELCE can reach 56, suggesting that ionic liquids can improve non-flammablility of the composite electrolyte.

Figure 3. Thermal properties and flammability tests of the LPELCE: (a) Different kinds of electrolytes with four basic electrolyte materials, and the state of electrolyte from liquid to all solid, the security become better. (b) TGA curves of electrolytes with different ingredients. (c) Flammability tests of commercial Celgard membrane, L-50%-PLCE (without ionic liquid in composite electrolyte) and L-50%-PELCE. (d) Limiting oxygen index of different electrolytes.

3.3 Electrochemical performance analysis


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3.3.1 Ionic conductivity Ionic conductivity is a key parameter to evaluate the performance of the electrolyte27-30. Arrhenius plots of ionic conductivity with various concentration of ionic liquid and LAGP as a function of temperature are shown in Figure S2 and Figure 4a. As can be seen, ionic conductivity of LPELCE indicates that the increase of temperature leads to the increase of ionic conductivity. In addition, the composite electrolyte containing 50%-60 wt% LAGP displays the highest ionic conductivity of 0.92×10-3~0.96×10-3 S cm-1 at room temperature. Furthermore, the conductivity has a sharp turn at 70 wt% LAGP and then drops progressively as the LAGP content increase, as expected, when the content of LAGP is 80%, the ionic conductivity of the electrolyte is close to the pure LAGP solid electrolyte of 1.9×10-4 S cm-1. Thus we can deduce that the dispersion of ionic liquid in composite electrolyte results in multi-directional swelling of the polymer molecular chain, forming more amorphous regions. The swollen polymer molecular chains provide effective channel for the Li+ migration, eventually let LPELCE exhibits a relatively high ionic conductivity compared to other solid polymer electrolyte systems (see Table S1). Therefore, introducing appropriate amount of IL in all solid polymer composite electrolyte is an effective way to improve conductivity, meanwhile, besides the superior conductivity, in our case, LPELCE generally has better mechanical strength and electrochemical stability.



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Figure 4. Electrical properties of LPEL composite electrolytes: (a) Arrhenius plots of the composite electrolytes with various LAGP concentrations, together with the schematic illustration for Li+ migration in electrolyte. (b) Electrochemical stability window of LPELCE.

3.3.2 Electrochemical stability The electrochemical stability window of the electrolyte is critical for the development of high-energy density lithium batteries. Currently, some high potential cathode materials have been developed, however, electrolytes that are stable enough to endure cathode decomposition at high potential versus Li+/Li remain rare8,12-15. With inorganic solids and IL as main ingredient of electrolyte, we are able to develop a composite electrolyte, which helps to improve the electrochemical stability. Figure 4b shows linear sweep voltammograms of LPELCE with various concentration of LAGP. When the potential is less than 4.8 V, the current is found to be more stable with respect to the LPELCE, while the current began to increase when the potential exceeding 4.8 V, which is related to the decomposition of the LPELCE. Thus, LPELCE have displayed an electrochemical stability window (ESW) nearly exceeding 4.8 V (vs. Li+/Li). We can conclude that LPELCE can be used in


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combination with high voltage cathodes for high energy lithium batteries. Figure 5a presents cyclic voltammetry of lithium electrode with L-50%-PELCE. A typical couple of reversible redox peaks are appeared at –0.5 V and 0.5 V (vs. Li+/Li), showing the typical plating and dissolution of lithium, respectively. These peaks are very sharp and fairly symmetrical to each other, and consistency of CV curves are very good after many times cycle, indicating excellent reversibility of Li+ pass through L-50%-PELCE with fast kinetics electrochemical process, and the plating/stripping process on the electrode is reversible. Interface compatibility between L-50%-PELCE and lithium electrode can directly affect the specific capacity and cycling stability of solid-state battery. Time evolution of the interfacial resistance in the symmetrically non-blocking Li/ L-50%-PELCE /Li cell was tested in Figure 5b. The bulk electrolyte resistance (Rb) and electrode/electrolyte interfacial resistance (Rf) can obtained from the spectrum at the whole frequency range. During storage the Rb of L-50%-PELCE is almost constantly, indicating that ionic conductivity of electrolyte does not change with extended storage time varies. However, there was a significant variation of Rf from the beginning to 24 h, then Rf slightly increases and tends to maintain steady. Hence, the result demonstrated that L-50%-PELCE can form a dense and stable SEI layer on the Li electrode surface in a short time. This SEI layer inhibits chemical reactions continue to occur on the surface of active Li electrode and thus helps to improve related properties of cell. The other stability analysis of lithium electrodeposition were evaluated through



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the method of ‘strip-plate test’ in symmetric Li/Li cells31. Figure 5c shows the time-dependent voltage profile of the cell with L-50%-PELCE cycled at current density of 0.2 mA cm-2, we can see that the voltage tends to be stable with increasing cycle time. The voltage changes in the initial mainly ascribed to the non-uniform lithium deposition and the interfacial film formed by the reaction of the electrolyte with the metal lithium. The cells show stable voltage profiles during subsequent cycles indicates that the SEI layer can keep stable during cycling.

Figure 5. The compatibility of LPELCE and lithium anode: (a) Cyclic voltammograms of the L-50%-PELCE in Li/Li symmetrical cells at 25℃ at a scan rate of 0.1 mV s-1. (b) Time evolution of the impedance response of Li/L-50%-PELCE/Li cell. (c) Voltage profile of the lithium plating/striping cycling with a current density of 0.2 mA cm-2.

In addition, the surface morphology of lithium metal after 400 h of cycling was analyzed by SEM. As seen in Figure 5d and 5e, the surface has become less and less smooth after several times cycles, however, there are no lithium dendrites or mossy lithium distributions on the surface of lithium metal, only a small amount of solid electrolyte particles can be discovered, indicating that the composite electrolyte can


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effectively inhibit the formation of lithium dendrites. In order to explore whether the proposed SEI is influenced by the composition of L-50%-PELCE, X-ray photoelectron spectroscopy (XPS) is used to study the chemical composition and element distribution of SEI layer symmetry, which is attached on the cycled Li anode surface after cycles. Figure 5f displays the F 1s and S 2p XPS spectra, the F, S are the main elements to promote the formation of the SEI layer, which have been demonstrated in many previous studies32,33. F ls spectrum reveals the surface layer composition contains components of S-F and LiF are dominated by the decomposition of TFSI-. The S 2p and O 1s spectra show the chemical consistent with that of -SO2CF3 (170.36 eV) and S-O (168.8 eV), it can reveal evidence of the reaction of these groups from TFSI- breakdown. Thus we can deduce that all of these ingredients may result format the SEI layer and the ingredients are formed by the decomposition between ionic liquid and Li anode.

Figure 5. (d) and (e) Scanning electron microscope (SEM) images of Li metal anode in Li/L-50%-PELCE/Li cell after 400 h of cycling with different scale bar. (f) XPS patterns of the cycled lithium anode with the L-50%-PELCE.

3.4 Effect of L-50%-PELCE in LFP/Li Cells



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Although the relate properties of the L-50%-PELCE imply a promising applicability in cell, the actual effect in lithium ion battery should still be proven. Therefore, the performance of L-50%-PELCE in solid-state battery of LiFePO4/Li was investigated in detail. Particularly, we mixed a small amount of the composition of electrolyte as a bridge to connect between active material of cathode and electrolyte (schematic illustration of the cell design in Figure 6a), the aim of this design is to effectively ameliorate the interface between electrode and electrolyte, reducing barriers of ion conductivity in the cell.

Figure 6. The performance of LPELCE in solid-state battery of LiFePO4/Li: (a) Schematic diagram representing the solid-state battery of LiFePO4/Li. (b) Cycling performance of LiFePO4/L-50%-PELCE/Li, insets indicate charge and discharge profiles. (c) C-rate discharge performance of LiFePO4/Li cells. (d) Photographs of button battery after cycles.

Setting the interval of voltage between 2.7 and 3.85 V, the first specific discharge capacity is as high as 157.8 mAh g-1 at a current rate of 0.05 C and maintains 141.3 mAh g-1 after the 50th cycle with a capacity retention of 89.5% (Figure 6b). More


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importantly, apart from the initial irreversible capacity, the coulombic efficiency is nearly 100% after the first cycle. In addition, the C-rate discharge performance of LiFePO4/Li cells assembled with L-50%-PELCE is evaluated, where the cell is charged at current rate of 0.05 C and discharged with different current densities ranging from 0.05 to 2 C. As shown in Figure 6c, they can achieve capacities of 156.18, 154.06, 153.29, 144.56, 138.48 and 53.62 mAh g-1 at current rates of 0.05, 0.1, 0.2, 0.5, 1 and 2 C, respectively. When the current rate returns to 0.05 C, there is a reversible capacity of 152.4 mAh g-1 remains, which still show a certain rate capability. Finally, a proper comparison on the performance is recommended in Figure S3, which as a comparative study to illustrate the effect of L-50% -PELCE on the performance of solid-state battery. We attribute the good performance of LiFePO4/L-50%-PELCE/Li to the better compatibility between electrode and electrolyte, which makes Li+ intercalation and de-intercalation easier, certainly, this is also closely related to the higher ionic conductivity, electrochemical stability of the electrolyte itself and stability of the interface in cell. However, impedance spectra (see Figure S4) of the cell was still increased after cycling, which might be due to the part of reaction happened between the electrolyte and lithium metal. 4. Conclusion In summary, "firmness and flexibility" LPELCE was fabricated via combining ceramic nanoparticles with IL gel polymer. This method not only provides the slurry easy to film-forming and ensures the mechanical strength of the composite electrolyte but also largely reduces the degree of crystallinity of the polymer, which further



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improves the ionic conductivity of the composite electrolyte. Meanwhile, LPELCE have good compatibility with lithium electrode, which can endure up to 4.8 V versus Li+/Li without significant anodic decomposition. Moreover, the electrolyte displayed good interface stability with lithium electrode after long times cycle, which can effectively inhibit the formation of lithium dendrites. Thus, with these advantages of LPELCE, enables the fabrication of solid-state metallic lithium battery with high safety and appreciably enhanced performance. This opens up an opportunity to use this type of electrolyte to develop high energy density and high security solid-state metallic lithium batteries. Supporting Information The Supporting Information is available free of charge on the ACS Publications website. Acknowledgements This work was financially supported by the Research Project of National University of Defense Technology. References (1) Molina Piper, D.; Evans, T.; Leung, K.; Watkins, T.; Olson, J.; Kim, S. C.; Han, S. S.; Bhat, V.; Oh, K. H.; Buttry, D. A.; Lee, S. H., Stable Silicon-Ionic Liquid Interface for Next-Generation Lithium-Ion Batteries. Nat. Commun. 2015, 6, 6230. (2) Zeng, X. X.; Yin, Y. X.; Li, N. W.; Du, W. C.; Guo, Y. G.; Wan, L. J., Reshaping Lithium Plating/Stripping Behavior via Bifunctional Polymer Electrolyte for Room-Temperature Solid Li Metal Batteries. J. Am. Chem. Soc. 2016, 138 (49), 15825.


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2015, 13, 546-553.

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