Acid-Scavenging Separators: A Novel Route for Improving Li-Ion

Sep 13, 2017 - The latter reduce the power delivered by the cell and also lead to the underutilization of the cell capacity due to increased interfaci...
0 downloads 8 Views 3MB Size
Download PDF
Acid-Scavenging Separators: A Novel Route for Improving Li-Ion Batteries’ Durability Anjan Banerjee,† Baruch Ziv,† Yuliya Shilina,† Shalom Luski,† Doron Aurbach,*,† and Ion C. Halalay‡ †

Department of Chemistry and BINA (BIU Institute for Nano-Technology and Advanced Materials), Bar-Ilan University, Ramat-Gan 590002, Israel ‡ General Motors R&D Center, Warren, Michigan 48090-1203, United States S Supporting Information *

ABSTRACT: Autocatalytic decomposition of LiPF6, with generation of HF and Lewis acids is the root cause for Li-ion battery (LIB) performance degradation. Acidic species promote various parasitic reactions, among which transition metal ions’ dissolution and the loss of electroactive as well as transport Li+ have the most detrimental consequences for LIB performance. Herein we report on the performance improvements enabled by an acid-scavenging separator in cells with graphite negative and LiMn2O4 or LiNi0.6Mn0.2Co0.2O2 positive electrodes. After 4 weeks of cycling at 55 °C, LiMn2O4∥graphite and LiNi0.6Mn0.2Co0.2O2∥graphite cells with functional separators retain 100 and 43% more capacity, respectively, than cells with plain polypropylene separators. Furthermore, cells with functionalized separators have half of the interfacial impedances of cells with baseline separators, irrespective of positive electrode. The benefits afforded by acid-scavenging separators thus extend to broader classes of cell chemistries, beyond those affected mainly by manganese dissolution and loss of electroactive Li+ ions.

T

degradation initiated by the dissolution of other TM ions (Ni and Co).8 Nevertheless, whatever their identity and source, dissolved TM ions migrate to the negative electrode and poison its protective surface film, also known as the solid−electrolyte interphase (SEI). The contaminated SEI then loses its passivating properties, after which malignant SEI growth and premature capacity loss become unavoidable.9−17 The loss of electroactive Li+ ions decreases the available energy in the LIB and also promotes the growth of thicker and more resistive surface films on electrode surfaces. The latter reduce the power delivered by the cell and also lead to the underutilization of the cell capacity due to increased interfacial resistances. LNMO and Li-rich oxygen-deficient nickel cobalt manganese (NCM) mixes oxides are promising candidates for electrochemical propulsion due to their high voltage (hence increased power) and large capacity (hence increased specific energy), respectively, in addition to other benefits such as environmental friendliness and low cost.16−19 These benefits notwithstanding, the Mn ion dissolution-related LIB performance degradation calls into question the commercial viability of these materials. Of all positive electrode materials seriously affected by manganese dissolution, LMO has been most widely studied and represents the model system for investigating the Mn (and

he successful expansion of Li-ion batteries (LIBs) from applications in consumer electronics to electrochemical propulsion requires significant improvements in features like specific and volumetric energy density, power performance, and durability. Advanced LIBs for electric or hybrid vehicle applications must achieve 10 years of service life.1−5 The present day state-of-art electrolytes consist of LiPF6 salt solutions in mixed alkyl carbonate solvents.4 While offering the best balance between performance benefits and drawbacks, these electrolyte solutions are neither electrochemically stable in contact with the electrochemically active materials in the electrodes nor chemically stable in mixed alkyl carbonate solvents at elevated temperatures. Furthermore, the LiPF6 salt undergoes autocatalytic decomposition (LiPF6 → LiF + PF5). In the presence of a trace amount of water, PF5 will generate HF (PF5 + H2O → 2HF + PF3O).3,6 The hydrofluoric and Lewis acids (PF5, PF3O, etc.) thus generated then promote other parasitic reactions in a LIB, among which reactions catalyzed by transition metal (TM) ions dissolved from positive electrode active materials and those involving the loss of Li+ cations are some of the most detrimental side reactions for LIB performance. Of all TM ions, the dissolution of Mnx+ ions and its deleterious consequences are most pronounced for materials with Mn3+ cations and spinel phases, such LiMn2O4 (LMO), LiMn1.5Ni0.5O4 (LNMO), and Li-rich oxygen-deficient mixed Ni−Mn−Co oxides.7 Furthermore, the consequences of manganese dissolution are dramatic in comparison to the © XXXX American Chemical Society

Received: August 18, 2017 Accepted: September 13, 2017 Published: September 13, 2017 2388

DOI: 10.1021/acsenergylett.7b00763 ACS Energy Lett. 2017, 2, 2388−2393

Letter

http://pubs.acs.org/journal/aelccp

Letter

ACS Energy Letters

acid-scavenging filler.21−31,37 The average thickness and porosity of the functional separator were 30 μm and ∼43%, respectively, while its loading with poly(DVB-4VP) was 2 mg· cm−2. Note that the physical properties of the functional separator from our study are similar to those of commercial separators. Details on separator fabrication are provided in the Supporting Information (SI). The surface morphology of the functional separator, obtained by HR-SEM, is shown in Figure 1. Figure 1a displays the overall porous structure of the functional separator, with 4−20 μm diameter macropores formed by the nonporous PVDF matrix material (see Figure 1b). The macropores are in turn filled with 100 nm diameter resin particles that create a nanoporous network, as seen in Figure 1c,d. The performance of the functional separator was first evaluated in LMO∥Li and NCM-622∥Li coin cells and then further tested in LMO∥graphite and NCM-622∥graphite pouch cells. All cells were filled with 1 M LiPF6/EC:EMC (3:7 v/v) electrolyte solution. Details regarding electrode manufacturing, cell assembly, and electrochemical tests are given in the SI. Cycling data at elevated temperature (55 °C) for LMO∥graphite and NCM-622∥graphite cells are shown in Figure 2 a,b, respectively. Because we aim to assess the benefits provided by the acid-scavenging separator for cell performance, we performed full-cell cycling only at high temperature, when the generation of acidic species in LiPF6 electrolyte solutions is accelerated. After 4 weeks of high-temperature cycling, the LMO∥graphite cells with baseline and functional separators experience 71 and 39% capacity losses, respectively, relative to their initial capacity, while NCM-622∥graphite cells with baseline and functional separators lose only 42 and 17% of their initial capacity, respectively. Note also that for both cell chemistries the Faradaic efficiency is higher in cells with functionalized separators than in cells with baseline separators. The remaining capacity of the cells and also the percent capacity loss per cycle are provided as functions of cycle index in Figures S2 and S3. The benefits from the acid-scavenging functional separator are clearly more pronounced in cells with LMO than those in cells with NCM-622 due to the severe consequences of parasitic reactions catalyzed by the dissolved Mn, a fraction thereof also leading to loss of electroactive Li+ ions. After 4 weeks of high-temperature cycling, LMO∥graphite cells with functional separators retain 100% more capacity than the baseline cells. On the other hand, in NCM-622∥graphite cells functional separators provide only a 43% increase in remaining capacity over the baseline cells. Nevertheless, note that the acid-scavenging separator keeps the capacity of the NCM-622∥graphite cells significantly closer to their initial capacity than in LMO∥graphite, which is most important from a practical perspective, with 83 and 61% retention of initial capacity retained at end of test (EOT), respectively in cells with NCM-622 and LMO. Two major causes for the capacity fading in LMO∥graphite cells are the underutilization of cell capacity due to increased cell resistances through malignant SEI growth and the net capacity loss caused by the destruction of the graphite materials and the negative electrode’s structure in reactions catalyzed by dissolved Mn ions.34 Analyses of the XRD and EIS data indicate that the acid-scavenging separator affects both capacity loss modes. Furthermore, the Mn amounts found in separators and graphite electrodes at EOT point to acid species scavenging as the only plausible cause for the improvements in LIB performance effected by the acid-scavenging separators. The

more broadly TM) dissolution-related LIB performance degradation. We therefore chose LMO−graphite cells as one of the test platforms in our studies. Several means for minimizing the Mn ions’ dissolution and its consequences were explored over the years: cationic and anionic substitutions into the active material lattice,7,17 surface coatings,16,22 and the use of various additives.22−26 Nevertheless, none proved completely successful all alone, and only a combination thereof is likely to maximize performance improvements. Recently, we proposed and demonstrated an alternative/complementary mitigation route: multifunctional separators.28−31 In cells using this measure, the SEI remains “healthy” (both maximally ion-conducting and electronically insulating) and maintains passivation of the negative electrode without malignant SEI growth throughout cell life, thus enabling improved capacity retention even during LIB operation at elevated temperatures. Even though such separators can perform several functions (TM ions trapping, acid species scavenging, and alkali metal ion dispensing), their main function is the trapping of TM (particularly Mn) cations subsequent to their dissolution from positive electrodes, with the other two functions playing only ancillary roles. Furthermore, their acid-scavenging function, which is based on an ion-exchange mechanism, may not be very efficient at low acid concentrations, that is, during the crucial phase of SEI formation early in a LIB’s life. Although many details of LIB degradation reaction mechanisms are still not fully elucidated, there exists little doubt that the interaction of HF and other acid species with positive electrode materials is the major factor driving the TM ions’ dissolution in LIBs with LiPF6 electrolyte solutions.14,15,2032−35 We therefore propose and demonstrate herein the benefits for LIB performance enabled by separators whose sole function is to suppress the root cause of LIB performance degradation: parasitic reactions initiated by HF and other acid species from the electrolyte solution. The active material in the functional separator reported here is a commercial resin consisting of a 25% cross-linked divinylbenzene backbone functionalized with 4-vinylpyridine, henceforth referred to as poly(DVB-4VP). Pyridine is a Lewis base that can scavenge acidic species (see Scheme 1)36 through the Lewis Scheme 1. Reaction between the Pyridine Group in the Resin and HF, with the Formation of Pyridinium Hydrofluoride

base−acid interaction, which is more effective than ionexchange for scavenging trace acid amounts. We show herein that the poly(DVB-4VP)-functionalized separator provides performance benefits for cell chemistries representative of two distinct classes of performance degradation mechanisms, LMO∥graphite and NCM-622∥graphite, where Mn dissolution and the loss of electrochemically active Li+ ions play, respectively, major and minor roles in LIB performance degradation. The functional separator was fabricated in-house by a phaseinversion method, using a poly(vinylidene fluoride hexafluoropropylene) copolymer as the matrix and poly(DVB-4VP) as 2389

DOI: 10.1021/acsenergylett.7b00763 ACS Energy Lett. 2017, 2, 2388−2393

Letter

ACS Energy Letters

Figure 1. SEM micrographs displaying the surface morphology of the composite functional separator: (a) macropores in the composite binder-filler structure are visible at low magnification, (b) zoomed-in detail showing an area of the nonporous PVDF-HFP binder matrix, (c) magnified area of a resin-filled macropore, and (d) zoomed-in detail displaying the nanopores formed by the poly(DVB-4VP) particles inside of the PVDF-HFP macropores.

separator reduces the amount of Mn dissolved in LMO∥graphite cells by a factor of 4.8 compared to cells with baseline separators. On the other hand, the reduction of the Mn amount dissolved from NCM-622 in cells with functionalized separators compared to that in cells with baseline separators is only 39%. Dissolved Ni and Co amounts deposited in the graphite electrodes are much smaller (13 and 6%, respectively, of the Mn amount in ppm) for the NCM-622∥graphite cell with the baseline separator and below the detection limit for the cell with the functional separator. Furthermore, the greater capacity loss rates observed in NCM-622∥Li cells relative to LMO∥Li cells during cycling tests at both room and elevated temperatures irrespective of separator type (see Figure S4) show that the availability of excess Li in half-cells cannot significantly reduce the capacity loss in the NCM-622∥Li cells. Therefore, the loss of electroactive Li+ from NCM-622 cannot be a major cause for capacity fading in NCM-622∥graphite cells. The major factors contributing to capacity loss in NCM622-based cells are acid-related degradation reactions that necessitate neither catalysis by TM ions nor the loss of electroactive Li+ and lead to surface film growth,38 as evidenced by ac impedance data below. Because these degradation mechanisms do not involve the consumption of electroactive Li+ ions, they are equally effective in both NCM-622∥Li and NCM-622∥graphite cells. Therefore, the excess Li present in NCM-622 half-cells cannot offer any advantage for improving capacity retention, as in the case of LMO half-cells. Thus, acidscavenging functional separators enable significant performance benefits also for positive electrode materials that do not suffer from TM ion dissolution issues or loss of electroactive Li+. Figure 4 displays Nyquist plots for electrochemical impedance spectroscopy (EIS) data from LMO∥graphite and

scavenging of acid species in turn reduces the TM dissolution from positive electrodes, the reactions catalyzed by Mn ions that consume electroactive Li+ and/or generate gases, as well as other degradation reactions that involve acid species but do not necessitate catalysis by Mn ions or the consumption of electroactive Li+. XRD patterns of the LMO and NCM-622 materials from pristine and cycled electrodes are shown in Figure 3a,b, respectively. It is clear, from the shifts of the XRD peak positions toward higher diffraction angles for the LMO cycled in the cell with the baseline separator, that the LMO lattice experiences shrinking during cycling due to loss of electroactive Li+ (i.e., a reduction of ∼1% in lattice constant at EOT), while no shrinking was detected at EOT in the LMO cycled in cells with a functional separator. On the other hand, the absence of changes in the diffraction patterns of NCM-622 between its pristine and cycled states, irrespective of the separator used in the cells, indicates that its lattice is inherently stable during sustained high-temperature cycling. The capacity decreases experienced by the NCM-622∥graphite cells during cycling must therefore result from the underutilization of cell capacity due to the increased cell resistance caused by film growth on the electrode surfaces, with no contributions from losses of electroactive Li+ ions. Elemental analyses of the negative electrodes and separators from cycled cells clearly indicate that the acid-scavenging separator suppresses the root cause of the Mn ions’ dissolution from positive electrodes. Note first that no TM ions were detected by postexperiment ICP-OES analyses of either the baseline or the functionalized separators from all tested cells. Table 1 displays the amounts of TM ions found in the graphite electrodes subsequent to the cycling tests. The acid-scavenging 2390

DOI: 10.1021/acsenergylett.7b00763 ACS Energy Lett. 2017, 2, 2388−2393

Letter

ACS Energy Letters

Figure 3. XRD patterns for (a) LMO and (b) NCM-622 positive electrode materials in pristine state and after high-temperature cycling with functional and baseline separators, as indicated. The diffraction peak at 65.1° in panel (b) is due to the Al current collector.

Table 1. Amounts of TM Ions Found on the Graphite Electrodes after the Cycling Tests of NCM-622∥Graphite and LMO∥graphite Cells with Baseline and Acid-Scavenging Separatorsa

Figure 2. Constant current cycling data for (a) LMO∥graphite and (b) NCM-622∥graphite cells at 55 °C.

TM Amount on Graphite Electrode/ppm vs Positive Electrode Active Mass

NCM-622∥graphite cells containing functional (a,c) and baseline separators (b,d). The double depressed arcs are characteristic features of Li-ion cells, with the chords subtending the high- and medium-frequency arcs assigned to charge-transfer and ion transport (through surface films) resistances, respectively. Because an unambiguous assignment of the various features in EIS spectra to one electrode or the other is impossible for data from two-electrode cells, we will confine our discussion to a qualitative comparison of data from cells with functional and baseline separators. The EIS data indicate that acid-scavenging separators are somewhat more effective in reducing the interfacial charge-transfer and film resistances in LMO∥graphite cells than in NCM-622∥graphite cells. At EOT, acid-scavenging separators affect reductions in high- and medium-frequency resistances by ∼2.5× in cells with LMO compared to cells with baseline separators. In contrast, in cells with NCM-622, acid-scavenging separators decrease the high-frequency resistance by 25% and the medium-frequency

NCM-622 separator functional baseline

Mn 102 167

Ni b

nd 22

LMO Co b

nd 10

Mn 250 1194

a

Note that the TM amounts in all separators were below the detection limit of ICP-OES. bND = Not detectable.

resistance by 2× over cells with baseline separators. (Estimates of the high- and medium-frequency resistances derived from the EIS spectra of the full cells are listed in Table S3.) While the negligible TM (Mn, Ni, Co) ions’ dissolution and loss of Li+ from NCM-622 in cells with an acid-scavenging separator cannot significantly affect the SEI on the graphite electrodes in those cells, other parasitic reactions due to acidic species still lead to significant increases in cell impedances, particularly in the cells with baseline separators. 2391

DOI: 10.1021/acsenergylett.7b00763 ACS Energy Lett. 2017, 2, 2388−2393

Letter

ACS Energy Letters

prominent causes for cell performance degradation. Clearly, the beneficial effects for LIB performance afforded by acidscavenging separators extend to broader classes of cell chemistries, due to their ability to suppress the performance degradation related to all sorts of acid-related parasitic reactions.

■

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsenergylett.7b00763. Details of experimental methods for separator fabrication, electrode manufacturing, cell assembly, and electrochemical testing; SEM images of pristine and cycled separators; relative discharging capacity and capacity loss rate per cycle in LMO∥graphite and NCM-622∥graphite cells; and electrochemical characterization and postdisassembly analysis of LMO∥Li and NCM-622∥Li cells (PDF)

■

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Anjan Banerjee: 0000-0002-5658-4610 Doron Aurbach: 0000-0001-8047-9020 Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS This work received partial funding from the Israel Committee of High Education and Prime Minister office within the framework of the INREP project.

■

REFERENCES

(1) Berg, E. J.; Villevieille, C.; Streich, D.; Trabesinger, S.; Novák, P. Rechargeable batteries: grasping for the limits of chemistry. J. Electrochem. Soc. 2015, 162, A2468−A2475. (2) Levasseur, A.; Cavalett, O.; Fuglestvedt, J. S.; Gasser, T.; Johansson, D. J. A.; Jørgensen, S. V.; Raugei, M.; Reisinger, A.; Schivley, G.; Strømman, A.; Tanaka, K.; Cherubini, F. Enhancing life cycle impact assessment from climate science: Review of recent findings and recommendations for application to LCA. Ecological Indicators. Ecol. Indic. 2016, 71, 163−174. (3) Goodenough, J. B.; Kim, Y. Challenges for rechargeable Li batteries. Chem. Mater. 2010, 22, 587−603. (4) Marom, R.; Amalraj, S. F.; Leifer, N.; Jacob, D.; Aurbach, D. A review of advanced and practical lithium battery materials. J. Mater. Chem. 2011, 21, 9938−9954. (5) Manthiram, A. Materials challenges and opportunities of lithium ion batteries. J. Phys. Chem. Lett. 2011, 2, 176−184. (6) Sloop, S. E.; Pugh, J. K.; Wang, S.; Kerr, J. B.; Kinoshita, K. Chemical reactivity of PF5 and LiPF6 in ethylene carbonate/dimethyl carbonate solutions. Electrochem. Solid-State Lett. 2001, 4, A42−A44. (7) Choi, M.; Manthiram, A. Comparison of metal ion dissolutions from lithium ion battery cathodes. J. Electrochem. Soc. 2006, 153, A1760−A1764. (8) Komaba, S.; Kumagai, N.; Kataoka, Y. Influence of manganese(II), cobalt(II), and nickel(II) additives in electrolyte on performance of graphite anode for lithium-ion batteries. Electrochim. Acta 2002, 47, 1229−1239.

Figure 4. Nyquist plots for LMO∥graphite cells with (a) functional and (b) baseline separators, as well as NCM-622∥graphite cells with (c) functional and (d) baseline separators. Note the changes in the axes’ ranges by a factor of 2.4 between panels (a) and (b) and by a factor of 2 from between panels (c) and (d).

We demonstrated herein the benefits offered for LIB performance by a novel acid-scavenging separator based on a 4-vinylpyridine-functionalized polymer. The functional separator neutralizes the acidic environment inside the cell, which in turn minimizes parasitic reactions and their consequences for performance degradation. Besides showing that acid-scavenging separators significantly improve the high-temperature capacity retention of cells with LMO positive electrodes (a material notorious for its Mn-dissolution-induced performance degradation), we also demonstrated that the beneficial effects of acidscavenging separators also obtain cells with NCM-622 positive electrodes, for which the TM ions’ dissolution and the loss of electroactive Li+ ions are much reduced and therefore not 2392

DOI: 10.1021/acsenergylett.7b00763 ACS Energy Lett. 2017, 2, 2388−2393

Letter

ACS Energy Letters (9) Jang, D. H.; Shin, Y. J.; Oh, S. M. Dissolution of spinel oxides and capacity losses in 4 V Li/Li x Mn2O4 cells. J. Electrochem. Soc. 1996, 143, 2204−2211. (10) Amatucci, G.; Schmutz, C. N.; Blyr, A.; Sigala, C.; Gozdz, A. S.; Larcher, D.; Tarascon, J.-M. Materials’ effects on the elevated and room temperature performance of C/LiMn2O4 Li-ion batteries. J. Power Sources 1997, 69, 11−25. (11) Pistoia, G.; Antonini, A.; Rosati, R.; Zane, D. Storage characteristics of cathodes for Li-ion batteries. Electrochim. Acta 1996, 41, 2683−2689. (12) Xia, Y.; Zhou, Y.; Yoshio, M. Capacity fading on cycling of 4 V Li /LiMn2O4 cells. J. Electrochem. Soc. 1997, 144, 2593−2600. (13) Du Pasquier, A.; Blyr, A.; Courjal, P.; Larcher, D.; Amatucci, G.; Ǵ erand, B.; Tarascon, J.-M. Mechanism for limited 55°C storage performance of Li1.05Mn1.95O4 electrodes. J. Electrochem. Soc. 1999, 146, 428−436. (14) Zhan, C.; Lu, J.; Kropf, A. J.; Wu, T.; Jansen, A. N.; Sun, Y. K.; Qiu, X.; Amine, K. Mn(II) deposition on anodes and its effects on capacity fade in spinel lithium manganate−carbon systems. Nat. Commun. 2013, 4, 2437. (15) Shkrob, I. A.; Kropf, A. J.; Marin, T. W.; Li, Y.; Poluektov, O. G.; Niklas, J.; Abraham, D. P. Manganese in graphite anode and capacity fade in Li ion batteries. J. Phys. Chem. C 2014, 118, 24335−24348. (16) Lu, J.; Zhan, C.; Wu, T.; Wen, J.; Lei, Y.; Kropf, A.; Wu, H.; Miller, D.; Elam, J.; Sun, Y.-K.; Qiu, X.; Amine, K. Effectively suppressing dissolution of manganese from spinel lithium manganate via a nanoscale surface-doping approach. Nat. Commun. 2014, 5, 5693. (17) Amatucci, G.; Du Pasquier, A.; Blyr, A.; Zheng, T.; Tarascon, J.M. The elevated temperature performance of the LiMn2O4/C system: failure and solutions. Electrochim. Acta 1999, 45, 255−271. (18) Myung, S. T.; Komaba, S.; Kumagai, N. Enhanced structural stability and cyclability of Al-doped LiMn2O4 spinel synthesized by the emulsion drying method. J. Electrochem. Soc. 2001, 148, A482−489. (19) Thackeray, M. M.; David, W. I. F.; Bruce, P. G.; Goodenough, J. B. Lithium insertion into manganese spinels. Mater. Res. Bull. 1983, 18, 461−472. (20) Guyomard, D.; Tarascon, J.-M. Li metal-free rechargeable LiMn2O4/carbon cells: Their understanding and optimization. J. Electrochem. Soc. 1992, 139, 937−948. (21) Gummow, R. J.; Dekock, A.; Thackeray, M. M. Improved capacity retention in rechargeable 4 V lithium/lithium-manganese oxide (spinel) cells. Solid State Ionics 1994, 69, 59−67. (22) Li, C.; Zhang, H. P.; Fu, L. J.; Liu, H.; Wu, Y. P.; Rahm, E.; Holze, R.; Wu, H. Q. Cathode materials modified by surface coating for lithium ion batteries. Electrochim. Acta 2006, 51, 3872−3883. (23) Yamane, H.; Inoue, T.; Fujita, M.; Sano, M. A casual study of the capacity fading of Li1.01Mn1.99O4 cathode at 80 °C, and the suppressing substances of its fading. J. Power Sources 2001, 99, 60−65. (24) Xu, M.; Lu, D.; Garsuch, A.; Lucht, B. L. Improved performance of LiNi0.5Mn1.5O4 cathodes with electrolytes containing dimethylmethylphosphonate (DMMP). J. Electrochem. Soc. 2012, 159, A2130− A2134. (25) Xu, M.; Zhou, L.; Dong, Y.; Tottempudi, U.; Demeaux, J.; Garsuch, A.; Lucht, B. L. Improved performance of high voltage graphite/LiNi0.5Mn1.5O4 batteries with added lithium tetramethyl borate. ECS Electrochem. Lett. 2015, 4, A83−A86. (26) Xu, M.; Zhou, L.; Dong, Y.; Chen, Y.; Demeaux, J.; MacIntosh, A. D.; Garsuch, A.; Lucht, B. L. Development of novel lithium borate additives for designed surface modification of high voltage LiNi0.5Mn1.5O4 cathodes. Energy Environ. Sci. 2016, 9, 1308−1319. (27) Wang, R.; Li, X.; Wang, Z.; Guo, H.; Wang, J. Electrochemical analysis for cycle performance and capacity fading of lithium manganese oxide spinel cathode at elevated temperature using ptoluenesulfonyl isocyanate as electrolyte additive. Electrochim. Acta 2015, 180, 815−823. (28) Banerjee, A.; Ziv, B.; Shilina, Y.; Luski, S.; Aurbach, D.; Halalay, I. C. Improving stability of Li-ion batteries by means of transition metal ions trapping separators. J. Electrochem. Soc. 2016, 163, A1083− A1094.

(29) Banerjee, A.; Shilina, Y.; Ziv, B.; Ziegelbauer, J. M.; Luski, S.; Aurbach, D.; Halalay, I. C. Review-Multifunctional materials for enhanced Li-ion batteries durability: A brief review of practical options. J. Electrochem. Soc. 2017, 164, A6315−A6323. (30) Banerjee, A.; Ziv, B.; Luski, S.; Aurbach, D.; Halalay, I. C. Increasing the durability of Li-ion batteries by means of manganese ion trapping materials with nitrogen functionalities. J. Power Sources 2017, 341, 457−465. (31) Banerjee, A.; Ziv, B.; Shilina, Y.; Luski, S.; Halalay, I. C.; Aurbach, D. Multifunctional manganese ions trapping and hydrofluoric acid-scavenging separator for lithium ion batteries based on poly(ethylene-alternate-maleic acid) dilithium salt. Adv. Energy Mater. 2017, 7, 1601556. (32) Jang, D. H.; Oh, S. M. Electrolyte effects on spinel dissolution and cathodic capacity losses in 4 V Li/LixMn2O4 rechargeable cells. J. Electrochem. Soc. 1997, 144, 3342−3348. (33) Amatucci, G.; Tarascon, J.-M. Optimization of insertion compounds such as LiMn2O4 for Li-ion batteries. J. Electrochem. Soc. 2002, 149, K31−K46. (34) Tsujikawa, T.; Yabuta, K.; Matsushita, T.; Arakawa, M.; Hayashi, K. A Study on the cause of deterioration in float-charged lithium-ion batteries using LiMn2O4 as a cathode active material. J. Electrochem. Soc. 2011, 158, A322−325. (35) Choi, N. S.; Yeon, J. T.; Lee, Y. W.; Han, J. G.; Lee, K. T.; Kim, S. S. Degradation of spinel lithium manganese oxides by low oxidation durability of LiPF6-based electrolyte at 60°C. Solid State Ionics 2012, 219, 41−48. (36) Huheey, J. E.; Keiter, E. A.; Keiter, R. L. Inorganic Chemistry: Principles of Structure and Reactivity, 4th ed.; James E. Pearson Education Publishers, 2000; ISBN: 81-7808-385-X. (37) Miao, R.; Liu, B.; Zhu, Z.; Liu, Y.; Li, J.; Wang, X.; Li, Q. PVDFHFP-based porous polymer electrolyte membranes for lithium-ion batteries. J. Power Sources 2008, 184, 420−426. (38) Schipper, F.; Dixit, M.; Kovacheva, D.; Talianker, M.; Haik, O.; Grinblat, J.; Erickson, E. M.; Ghanty, C.; Major, D. T.; Markovsky, B.; Aurbach, D. Stabilizing nickel-rich layered cathode materials by a highcharge cation doping strategy: zirconium-doped LiNi0.6Co0.2Mn0.2O2. J. Mater. Chem. A 2016, 4, 16073−16084.

2393

DOI: 10.1021/acsenergylett.7b00763 ACS Energy Lett. 2017, 2, 2388−2393