原位构建富氟SEI的凝胶电解质用于金属锂二次电池

doi:10.11949/0438-1157.20220316

摘要/Abstract

摘要：

以六氟磷酸锂（LiPF₆）为四氢呋喃的聚合引发剂制备凝胶电解质，同时作为氟源在金属锂负极表面原位构建富含LiF的固态电解质界面层（solid electrolyte interface，SEI）来抑制锂枝晶的生长以及金属锂/电解液之间的副反应。所制备的凝胶电解质具有较高的室温离子电导率（1.33 mS·cm^-1）和较宽的电化学稳定窗口（4.5 V）。原位聚合方式组装金属锂对称电池循环后，锂负极表面没有明显的锂枝晶和被损毁的形貌出现；XPS结果表明锂负极表面生成了富含LiF的SEI。组装的LiFePO₄全电池在1 C的电流密度下，稳定循环400周后仍保持118.7 mAh·g^-1的放电比容量。得益于四氢呋喃在开环聚合反应过程中，促进了LiPF₆分解反应平衡的正向移动，在锂负极表面形成稳定的富含LiF的SEI，能够抑制锂枝晶的生长并防止其被持续性的腐蚀破坏。

关键词: 氟化锂, 固态电解质界面层, 原位聚合, 凝胶聚合物电解质, 金属锂电池

Abstract:

A gel electrolyte was prepared by using lithium hexafluorophosphate (LiPF₆) as the polymerization initiator of tetrahydrofuran, and at the same time as a fluorine source, a LiF-rich solid electrolyte interface (SEI) was constructed in-situ on the surface of the lithium metal anode to suppress the growth of lithium dendrites and side reactions between metallic lithium/electrolyte. The as-prepared gel polymer electrolyte presents an ionic conductivity of 1.33 mS·cm^-1 at room temperature and shows a high electrochemical stability up to 4.5 V. Compared with linear sweep voltammetry in 335C electrolyte, lower reduction current is observed at the range of 0—1.5 V (vs Li/Li⁺) in the cell with gel polymer electrolyte, which indicates that gel polymer electrolyte can mitigate the side reaction of metallic lithium with electrolyte. The lithium metal anode in the symmetric-cell with in-situ polymerization gel polymer electrolyte exhibits no obvious lithium dendrite and damaged morphology. X-Ray photoelectron spectroscopy results further reveal that the lithium metal anode in gel polymer electrolyte is formed a stable SEI with LiF-rich compound, which is much enhanced than that of in 335C electrolyte. Consequently, the Li|LiFePO₄ cells with gel polymer electrolyte exhibits a long-term cycling stability, which can release a reversible capacity 118.7 mAh·g^-1 after 400 cycles at a current density of 1 C, as well as coulombic efficiency of 99.5%. Benefit from the ring opening polymerization process of tetrahydrofuran, PF₅ participates the formation reaction of intermediate product [(THF)⁺(PF₅)^-], which caused the equilibrium of the decomposition reaction shift to the right and therefore increase the formation of LiF on the surface of lithium metal anode. This process results in a great enhancement of the cyclability due to LiF-rich formed in the SEI. Therefore, the growth of lithium dendrite can be prevented by the stable SEI, as well as the side reaction between lithium metal and electrolyte.

Key words: LiF, SEI, in-situ polymerization, gel polymer electrolyte, lithium mental batteries

中图分类号:

TQ 125.1

李文涛, 林慧娟, 钟海. 原位构建富氟SEI的凝胶电解质用于金属锂二次电池[J]. 化工学报, 2022, 73(7): 3240-3250.

Wentao LI, Huijuan LIN, Hai ZHONG. LiF-rich SEI generated by in-situ gel polymer electrolyte process for lithium metal rechargeable batteries[J]. CIESC Journal, 2022, 73(7): 3240-3250.

图/表 11

图1 (a) THF开环聚合机理示意图； (b) 纤维素隔膜支撑的GPE光学照片； (c)，( d)不同放大倍数的GPE的SEM图；(e) 纤维素隔膜的SEM图

Fig.1 (a) Illustration of polymerization mechanism; (b) Photograph of GPE with cellulose film; (c), (d) SEM images of GPE under different magnifications; (e) SEM image of cellulose film

图2 (a) GPE, PTHF以及335C电解液的FTIR光谱； (b) GPE与335C电解液的离子电导率-温度变化曲线； (c) Li|GPE|Li对称电池的计时安培曲线（插图为对称电池极化前后的交流阻抗谱）； (d) GPE与335C电解液的LSV曲线

Fig.2 (a) FTIR spectra of GPE, PTHF and 335C electrolyte; (b) Temperature dependent ionic conductivity of GPE and 335C electrolyte; (c) The chronoamperometry profile of Li|GPE|Li symmetric cell（the inset displays the impedance spectra before and after chronoamperometry); (d) Linear sweep curves of GPE and 335C electrolyte

图3 (a) 室温下Li|GPE|Li对称电池在不同静置时间的交流阻抗谱图； (b) 采用GPE、 335C电解液组装的Li|Li电池在电流密度为0.5 mA·cm-2, 面容量为0.5 mAh·cm-2条件下的循环稳定性能图；(c) 335C电解液及(d) GPE组装的锂负极经过20次循环后表面的SEM图

Fig.3 (a) AC impedance spectra of Li|GPE|Li symmetrical cells for different time at room temperature; (b) Cyclic performance of Li symmetric cells with GPE, 335C electrolyte at a current density of 0.5 mA·cm-2 with area capacity of 0.5 mAh·cm-2; Typical SEM images of the Li anode with (c) 335Celectrolyte, and (d) GPE after 20 cycles

Fig.4 (a) Long-term cycling performance of Li|GPE|LiFePO4 cells(the cells were charged and discharged between 2.0—4.0 V at a current rate of 1 C); (b) DQ/DV diagram corresponding to charge and discharge curves of LMBs; (c) Rate performance of Li|GPE|LiFePO4 at various current rate; (d) Corresponding voltage profiles at various current rates

图5 GPE和335C电解液中循环50周后锂负极表面XPS的(a) F 1s谱图和(b) Li 1s谱图； (c) 金属锂表面LiF物质生成反应路径示意图

Fig.5 XPS spectra of Li metal (a) F 1s spectra, (b) Li 1s spectra in GPE and 335C electrolyte after 50 cycle;(c) Schematic diagram of LiF produce reaction

图A1 THF与335C前体混合溶液质量比为1∶2 (a), 1∶3 (b), 1∶4 (c)引发聚合后倒置状态的照片

Fig.A1 The photograph of THF/335C precursor solution with mass ratios of 1∶2 (a), 1∶3 (b), 1∶4 (c) after completion of polymerization

图A2 (a) Li|GPE|Li对称电池的阻抗拟合谱图; (b) Li|335C|Li对称电池的计时安培曲线(插图为对称电池极化前后的交流阻抗谱)

Fig.A2 (a) The impedance spectra of Li|GPE|Li symmetric cell before and after chronoamperometry. (b) The chronoamperometry profile of Li|335C|Li symmetric cell(The inset displays the impedance spectra before and after chronoamperometry)

图A3 对应图2(d)中的GPE和335C电解液在LSV曲线中被还原分解区域内[0 ~ 1.5 V(vs Li/Li+)]放大图

Fig.A3 The corresponding magnified views of two electrolytes decomposed at reduction reaction regions [0—1.5 V(vs Li/Li+)] in Fig. 2(d)

图A4 (a) 室温下Li|335C|Li对称电池在不同静置时间的交流阻抗谱图; (b)新鲜锂负极表面的SEM图; (c), (d) GPE所组装的锂负极经过20次循环后金属锂表面在不同尺度下的SEM图

Fig.A4 (a) AC impedance spectra of Li|335C|Li symmetrical cell for different time at room temperature; (b) Typical SEM images at the surface of fresh Li anode; (c),(d) Typical SEM images of the Li anode with GPE after 20th cycles under different scales

图A5 Li|LiFePO4电池在充放电电压为2.0 ~ 4.0 V以及电流密度为0.5 C条件下分别采用GPE和335C电解液的长期循环性能

Fig.A5 Long-term cycling performance of Li| LiFePO4 cells with GPE or 335C electrolyte at a current rate of 0.5 C and voltage range of 2.0—4.0 V

图A6 Li|GPE|Li对称电池循环50周后金属锂表面的XPS谱图

Fig.A6 XPS survey spectrum of lithium metal anode in GPE after 50 cycles

参考文献 40

1	Liu F Q, T, Li T, Yang Y J, et al. Investigation on the copolymer electrolyte of poly(1, 3-dioxolane-co-formaldehyde)[J]. Macromolecular Rapid Communications, 2020, 41(9): 2000047.
2	Bai M H, Xie K Y, Hong B, et al. An artificial Li₃PO₄ solid electrolyte interphase layer to achieve petal-shaped deposition of lithium[J]. Solid State Ionics, 2019, 333: 101-104.
3	Zhang Q K, Zhang X Q, Yuan H, et al. Thermally stable and nonflammable electrolytes for lithium metal batteries: progress and perspectives[J]. Small Science, 2021, 1(10): 2100058.
4	Jin D Q, Hu K, Hou R, et al. Vertical nanoarrays with lithiophilic sites suppress the growth of lithium dendrites for ultrastable lithium metal batteries[J]. Chemical Engineering Journal, 2021, 405: 126808.
5	Golozar M, Paolella A, Demers H, et al. Direct observation of lithium metal dendrites with ceramic solid electrolyte [J]. Scientific Reports, 2020, 10: 18410.
6	Ke X Y, Wang Y, Dai L M, et al. Cell failures of all-solid-state lithium metal batteries with inorganic solid electrolytes: lithium dendrites[J]. Energy Storage Materials, 2020, 33: 309-328.
7	Chi S S, Liu Y C, Zhao N, et al. Solid polymer electrolyte soft interface layer with 3D lithium anode for all-solid-state lithium batteries[J]. Energy Storage Materials, 2019, 17: 309-316.
8	Lu Y, Zhao C Z, Yuan H, et al. Critical current density in solid-state lithium metal batteries: mechanism, influences, and strategies[J]. Advanced Functional Materials, 2021, 31(18): 2009925.
9	Chen L, Li W X, Fan L Z, et al. Intercalated electrolyte with high transference number for dendrite-free solid-state lithium batteries[J]. Advanced Functional Materials, 2019, 29(28): 1901047.
10	Tabani Z, Maghsoudi H, Fathollahi Zonouz A. High electrochemical stability of polyvinylidene fluoride (PVDF) porous membranes using phase inversion methods for lithium-ion batteries[J]. Journal of Solid State Electrochemistry, 2021, 25(2): 651-657.
11	Tarascon J M, Gozdz A S, Schmutz C, et al. Performance of Bellcore’s plastic rechargeable Li-ion batteries[J]. Solid State Ionics, 1996, 86/87/88: 49-54.
12	Zhou J Q, Ji H Q, Liu J, et al. A new high ionic conductive gel polymer electrolyte enables highly stable quasi-solid-state lithium sulfur battery[J]. Energy Storage Materials, 2019, 22: 256-264.
13	Chen F, Yang D J, Zha W P, et al. Solid polymer electrolytes incorporating cubic Li₇La₃Zr₂O₁₂ for all-solid-state lithium rechargeable batteries[J]. Electrochimica Acta, 2017, 258: 1106-1114.
14	Wang Q Y, Xu X Q, Hong B, et al. Molecular engineering of a gel polymer electrolyte via in situ polymerization for high performance lithium metal batteries[J]. Chemical Engineering Journal, 2022, 428: 131331.
15	Deng B, Jing M X, Li L X, et al. Nano-zirconia boosting the ionic conductivity and lithium dendrite inhibition ability of a poly(1, 3-dioxolane) solid electrolyte for high-voltage solid-state lithium batteries[J]. Sustainable Energy & Fuels, 2021, 5(21): 5461-5470.
16	Zhang X L, Zhao S Y, Fan W, et al. Long cycling, thermal stable, dendrites free gel polymer electrolyte for flexible lithium metal batteries[J]. Electrochimica Acta, 2019, 301: 304-311.
17	Wu H, Tang B, Du X F, et al. LiDFOB initiated in situ polymerization of novel eutectic solution enables room-temperature solid lithium metal batteries[J]. Advanced Science, 2020, 7(23): 2003370.
18	Shen Y Q, Zhu W, Papadaki M, et al. Thermal decomposition of solid benzoyl peroxide using advanced reactive system screening tool: effect of concentration, confinement and selected acids and bases[J]. Journal of Loss Prevention in the Process Industries, 2019, 60: 28-34.
19	Zhong H, Wang C, Xu Z, et al. A novel quasi-solid state electrolyte with highly effective polysulfide diffusion inhibition for lithium-sulfur batteries[J]. Scientific Reports, 2016, 6: 25484.
20	Xie M, Wu Y, Liu Y, et al. Pathway of in situ polymerization of 1, 3-dioxolane in LiPF₆ electrolyte on Li metal anode[J]. Materials Today Energy, 2021, 21: 100730.
21	Cui Y Y, Liang X M, Chai J C, et al. High performance solid polymer electrolytes for rechargeable batteries: a self-catalyzed strategy toward facile synthesis[J]. Advanced Science, 2017, 4(11): 1700174.
22	Ma Q, Yue J P, Fan M, et al. Formulating the electrolyte towards high-energy and safe rechargeable lithium-metal batteries[J]. Angewandte Chemie International Edition, 2021, 60(30): 16554-16560.
23	Tominaga Y, Kato S, Nishimura N. Preparation and electrochemical characterization of magnesium gel electrolytes based on crosslinked poly(tetrahydrofuran)[J]. Polymer, 2021, 224: 123743.
24	Li T, Zhang X Q, Shi P, et al. Fluorinated solid-electrolyte interphase in high-voltage lithium metal batteries[J]. Joule, 2019, 3(11): 2647-2661.
25	Yuan Y X, Wu F, Bai Y, et al. Regulating Li deposition by constructing LiF-rich host for dendrite-free lithium metal anode[J]. Energy Storage Materials, 2019, 16: 411-418.
26	Feng Y Y, Zhang C F, Li B, et al. Low-volume-change, dendrite-free lithium metal anodes enabled by lithophilic 3D matrix with LiF-enriched surface[J]. Journal of Materials Chemistry A, 2019, 7(11): 6090-6098.
27	Hoene R, Reichert K H W. Zur aufklärung des initiierungsschrittes der kationischen polymerisation von tetrahydrofuran mit PF₅ [J]. Die Makromolekulare Chemie, 1976, 177(12): 3545-3570.
28	Zhang C J, Hu L F, Wu H L, et al. Dual organocatalysts for highly active and selective synthesis of linear poly(γ-butyrolactone)s with high molecular weights[J]. Macromolecules, 2018, 51(21): 8705-8711.
29	Huang S Q, Cui Z L, Qiao L X, et al. An in situ polymerized solid polymer electrolyte enables excellent interfacial compatibility in lithium batteries[J]. Electrochimica Acta, 2019, 299: 820-827.
30	O'Connor C J, Cleverly D R. Fourier-transform infrared assay of bile salt-stimulated lipase activity in reversed micelles[J]. Journal of Chemical Technology & Biotechnology, 1994, 61(3): 209-214.
31	赵航, 魏闯, 康鑫, 等. 锂离子电池三元正极材料的研究进展[J]. 中国陶瓷, 2020, 56(5): 10-15.
	Zhao H, Wei C, Kang X, et al. Research progress of ternary cathode materials for lithium ion battery[J]. China Ceramics, 2020, 56(5): 10-15.
32	蓝兹炜, 张建茹, 李园园, 等. 基于锂离子电池正极材料的一元/二元复合正极材料研究进展[J]. 储能科学与技术, 2021, 10(1): 27-39.
	Lan Z W, Zhang J R, Li Y Y, et al. Research progress of mono/binary composite cathode materials based on lithium-ion battery cathode materials[J]. Energy Storage Science and Technology, 2021, 10(1): 27-39.
33	Xu C, Sun B, Gustafsson T, et al. Interface layer formation in solid polymer electrolyte lithium batteries: an XPS study[J]. Journal of Materials Chemistry A, 2014, 2(20): 7256-7264.
34	Che H Y, Yang X R, Wang H, et al. Long cycle life of sodium-ion pouch cell achieved by using multiple electrolyte additives[J]. Journal of Power Sources, 2018, 407: 173-179.
35	Winkler V, Hanemann T, Bruns M. Comparative surface analysis study of the solid electrolyte interphase formation on graphite anodes in lithium-ion batteries depending on the electrolyte composition[J]. Surface and Interface Analysis, 2017, 49(5): 361-369.
36	Fu J L, Ji X, Chen J, et al. Lithium nitrate regulated sulfone electrolytes for lithium metal batteries[J]. Angewandte Chemie International Edition, 2020, 59(49): 22194-22201.
37	Qiao Y, Wu J W, Zhao J, et al. Synergistic effect of bifunctional catalytic sites and defect engineering for high-performance Li-CO₂ batteries[J]. Energy Storage Materials, 2020, 27: 133-139.
38	Wang L N, Liu J Y, Yuan S Y, et al. To mitigate self-discharge of lithium–sulfur batteries by optimizing ionic liquid electrolytes[J]. Energy & Environmental Science, 2016, 9(1): 224-231.
39	Krotkov D, Schneier D, Menkin D S, et al. Operando terahertz spectroscopy of solid electrolyte interphase evolution on silicon anodes[J]. Batteries & Supercaps, 2022, 5(1): e202100183.
40	Hamidah N L, Wang F M, Nugroho G. The understanding of solid electrolyte interface (SEI) formation and mechanism as the effect of flouro-o-phenylenedimaleimaide (F-MI) additive on lithium-ion battery[J]. Surface and Interface Analysis, 2019, 51(3): 345-352.

[1]	逯翠梅1，李辉1，2，李昱琢1，谭先周2，李贵2. 硅胶衍生尼古丁印迹整体柱的制备及其识别[J]. 化工进展, 2013, 32(07): 1613-1620.
[2]	李杰, 刘红研, 汪树军, 游龙, 王肃凯. 密胺树脂硫磺微胶囊的制备及应用[J]. 化工学报, 2011, 62(6): 1716-1722.
[3]	孙凯，张步宁，晏凤梅，尹国强，崔英德. 石蜡微胶囊型相变储能材料制备及表征[J]. CIESC Journal, 2011, 30(12): 2676-.
[4]	胡剑峰，夏正斌，司徒粤，陈焕钦. MF包封DCPD自修复微胶囊的合成 [J]. CIESC Journal, 2010, 61(11): 2978-2984.
[5]	何秋星, 刘蕤, 涂伟萍. 铋掺杂氧化锡/聚氨酯的原位聚合动力学 [J]. 化工学报, 2008, 59(9): 2366-2370.
[6]	方玉堂匡胜严张正国高学农. 纳米胶囊相变材料的制备 [J]. CIESC Journal, 2007, 58(3): 771-775.
[7]	庄秋虹，张正国，方晓明. 微/纳米胶囊相变材料的制备及应用进展 [J]. CIESC Journal, 2006, 25(4): 388-.
[8]	张森;史鹏飞. 凝胶聚合物电解质的电化学性能 [J]. CIESC Journal, 2005, 56(2): 329-332.