Lithium Bis(oxalate)borate Research Articles

Selective Application of Electrolyte Additives on Anode or Cathode Investigated By on-Line Electrochemical Mass Spectrometry

Recently, many investigations have been devoted to the development of novel electrolyte additives for Li-ion batteries. In carbonate-based electrolytes, most additives are reduced preferentially during the first charging cycle to generate a solid-electrolyte interphase (SEI) on the anode.1 Vinylene carbonate (VC) is the most widely investigated electrolyte additive for EC-based electrolytes, and its reduction has a well-characterized effect on the SEI on graphite anodes.2,3 In contrast, lithium bis(oxalate) borate (LiBOB) has been shown to generate CO2 and a cathode passivation film upon its oxidation that inhibits the oxidation of bulk electrolyte at the cathode.4 In this study, we employ our newly developed two-compartment Li-ion battery cell,5,6 which provides a tight seal between the anode and the cathode compartment, to investigate the effect of VC and LiBOB selectively on the anode and cathode side. Our two-compartment cell features an edge-sealed Li+-ion conductive glass ceramic (Ohara glass), and we demonstrate that a lamination of the Ohara glass with a layered polypropylene-aluminum-foil can effectively suppress any gas and liquid diffusion between the two compartments. Figure 1 shows that the layered PP-Al-foil sealing can avoid continuous CO2 (m/z = 44) evolution during OCV, in contrast to a PP-foil sealing. The potential independent CO2 increase for the latter is caused by water permeation to the metallic lithium counter-electrode leading to OH--catalyzed EC hydrolysis.5 We further use On-line Electrochemical Mass Spectrometry (OEMS)7 to investigate the effect of VC and LiBOB on the gas generation during the first three formation cycles of NMC/Li half cells, graphite/Li half cells, and NMC/graphite full cells. Our experimental approach is to separate the electrodes in the half cell arrangement, such that all gases detected by OEMS stem exclusively from either the NMC electrode or the graphite electrode. The influence of the lithium side is completely suppressed, and the effect of the additives can be monitored in a reductive (graphite) or oxidative (NMC) environment. Subsequently, we remove the edge-sealed gas diffusion barrier and investigate the gas evolution in NMC/graphite full cells in a one-compartment cell arrangement, to see the sum of gas generation from both electrodes. We quantify our OEMS results using a calibration gas, and give both, quantitative and mechanistic insights into the effect of VC and LiBOB on the gas evolution in Li-ion batteries. Figure 2 highlights the combined gas evolution from the NMC cathode and the graphite anode measured by OEMS in a one-compartment cell arrangement using LP57 (1M LiPF6 EC/EMC 3/7 wt/wt) without additives. The main gases evolved upon formation are ethylene C2H4 (m/z = 26), hydrogen H2 (m/z = 2), and carbon dioxide CO2 (m/z = 44). While H2 results from the unavoidable presence of trace water (< 20 ppm), C2H4 is known to be the main gaseous product of EC reduction at the graphite anode. CO2 evolution is only detected at the end of charge and is likely to originate from the oxidation of the carbonate-based electrolyte at the NMC cathode. References S. S. Zhang, J. Power Sources, 162, 1379 (2006).D. Aurbach et al., Electrochimica Acta, 47, 1423 (2002).B. Zhang et al., submitted (2015).M. Xu, et al., J. Phys. Chem. C, 118, 7363 (2014).M. Metzger et al., J. Electrochem. Soc., 167, A1123 (2015).M. Metzger et al., J. Electrochem. Soc., 167, A1227 (2015).N. Tsiouvaras et al., J. Electrochem. Soc., 160, A471 (2013). Acknowledgement The authors gratefully acknowledge BASF SE for financial support of this research through the framework of its Scientific Network on Electrochemistry and Batteries. Figure 1

LiBOB 전해액 첨가제 도입에 따른 Li(Ni&lt;sub&gt;1/3&lt;/sub&gt;Co&lt;sub&gt;1/3&lt;/sub&gt;Mn&lt;sub&gt;1/3&lt;/sub&gt;)O&lt;sub&gt;2&lt;/sub&gt;/graphite 전지의 고온특성

The effects of electrolyte additives, lithium bis(oxalate)borate (LiBOB), fluoroethylene carbonate (FEC), vinylene carbonate (VC), 2-(triphenylphosphoranylidene) succinic anhydride (TPSA), on high-temperature storage properties of /graphite are investigated with coin-type full cells. The 1 wt.% LiBOB-containing electrolyte showed the highest capacity retention after high temperature () storage for 20 days, 86.7%, which is about 5% higher than the reference electrolyte, 1.15M lithium hexafluorophosphate () in ethylene carbonate/ethyl methyl carbonate (EC/EMC, 3/7 by volume). This enhancement is closely related to the formation of semi-carbonate compounds originated from anions, thereby resulting in lower SEI thickness and interfacial resistance after storage. In addition, the 1 wt.% LiBOB-containing electrolyte also exhibited better cycle performance at 25 and than the reference electrolyte, which indicates that LiBOB is an effective additive for high-temperature performance of /graphite chemistry.

Understanding How Libob Improves the Thermal Stability of Electrolytes in Lithium Ion Batteries

Lithium bis(oxalate) borate (LiBOB) is a commonly used salt in lithium ion batteries due to its capability to improve the thermal stability and high temperature cycling. In addition, LiBOB is capable of forming a protective solid electrolyte interphase (SEI) layer on both graphitic anode and cathode surfaces and has been shown to passivate the aluminum current collector. While LiBOB has been pursued as a primary salt for lithium ion battery electrolytes1, it is most commonly utilized in commercial cells on the additive level with LiPF6as the primary salt because of its lower bulk conductivity and disadvantageous interfacial properties (i.e., higher impedance, lower charge transfer). Despite multiple reports regarding the enhanced thermal stability of electrolytes using LiBOB as an additive, there is not enough understanding of the mechanism by which this improvement is achieved.2 In this work, the reaction between LiBOB and LiPF6 at 100°C in both carbonate and organosilicon-based electrolytes is described. Specifically, the reaction products formed when LiBOB reacts with LiPF6have been identified using nuclear magnetic spectroscopy (NMR) and tracked as a function of time. The thermal stability of LiBOB-containing electrolytes was evaluated at 100°C using a custom analysis method where neat electrolyte samples were sealed in Teflon-lined glass NMR tubes. The LiBOB/LiPF6 reaction was tracked and quantified using 1H, 19F and 31P NMR. This work shows that the initial LiBOB degradation products are tetrafluorooxalatophosphate (TFOP) and difluorooxalato borate (DFOB). Over time, all of the boron from the LiBOB becomes tetrafluoroborate (BF4 -) and the tetrafluorooxalatophosphate (TFOP) becomes difluorophosphate (O2PF2 -). Once the TFOP and DFOB are consumed, the thermal protection of LiBOB disappears and degradation of the solvent with LiPF6begins. Therefore, the TFOP concentration can be used as a benchmark for predicting the onset of thermal decomposition. This reaction pathway has been analyzed and quantified for several carbonate electrolytes (EC/DEC or EC/EMC, 3/7 by volume).

Lithium difluoro(oxalate)borate for robust passivation of LiNi0.5Mn1.5O4 in lithium-ion batteries

In order to improve the electrochemical performance and understand the mechanisms of capacity fading of lithium nickel manganese oxide cathodes (LiNi0.5Mn1.5O4), we examined the electrochemical performance of cathodes using electrolytes in which LiPF6 was partially substituted with lithium bis(oxalate)borate (LiBOB) or lithium difluoro(oxalate)borate (LiFOB). At ambient temperature, the cells employing the electrolyte containing oxalate-type salts exhibited improved cycle performance, and at an elevated temperature of 45°C, incorporation of the LiFOB salt gave rise to superior capacity retention. In contrast, LiBOB exerted detrimental effects on the electrochemical performance of the cathodes. In-depth electrochemical and spectroscopic analyses revealed that the decomposition of the lithium salt influenced the formation of organic and fluoride films and their growth on the cathode surface; this decomposition may also play a crucial role in controlling the surface characteristics of the cathode material in the lithium-ion battery system during high-voltage application.

Synergistic Effects of Suberonitrile-LiBOB Binary Additives on the Electrochemical Performance of High-Voltage LiCoO2 Electrodes

Suberonitrile (SUN) and lithium bis(oxalate)borate (LiBOB) were investigated as binary additives for Li-ion batteries that used LiCoO2 as a cathode, cycled at high cutoff potentials and utilized LiPF6-based electrolyte. Linear sweep voltammetry (LSV) results revealed that LiBOB oxidized prior to the decomposition of the reference electrolyte. By contrast, SUN has a higher oxidization potential, and in the electrolyte it provided better electrolyte stability at higher potentials. In the electrolyte with binary additives, the electrochemical performance of LiCoO2 was enhanced significantly, and the initial coulombic efficiency increased to 94% compared with 90% in reference electrolyte. The cell also exhibited capacity retention of 62% after 500 cycles, a strong contrast with the 25% measured in reference electrolyte. Preliminary studies using electrochemical impedance spectra (EIS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) analyses indicated that the combination of the two additives had a unique influence on the structure and composition of the cathode-electrolyte interface (CEI) on LiCoO2. Ex situ X-ray diffraction (XRD) confirmed that structural change of the LiCoO2 material was not the main reason causing poor cycling performance when charging to the 4.5 V cutoff potential.

Solid electrolyte interphases at Li-ion battery graphitic anodes in propylene carbonate (PC)-based electrolytes containing FEC, LiBOB, and LiDFOB as additives

Density functional theory is used to investigate the reactivity, reduction and effect of electrolyte additives such as fluoroethylene carbonate (FEC), lithium bis(oxalate) borate (LiBOB) and lithium difluoro(oxalato) borate (LiDFOB) in propylene carbonate (PC)-based Li-ion battery electrolytes. The structural, thermodynamical and calculated infra-red vibrational analyses indicate that FEC additives reduce prior to PC, providing stable SEI film formation near the graphite anode. The reduction and reaction mechanisms of LiBOB and LiDFOB influence the SEI film composition at the graphite surface. These additives contribute to stable SEI film formation without degradation of the anode structure by PC co-intercalation.

Performance improvement and failure mechanism of LiNi(0.5)Mn(1.5)O4/graphite cells with biphenyl additive.

The cycling performance of the LiNi0.5Mn1.5O4/graphite cells cycled to 4.8 V versus Li/Li(+) at room temperature has been investigated. The control electrolyte is 1.0 M LiPF6 ethylene carbonate (EC)/ethylmethyl carbonate (EMC)/fluoroethylene carbonate (FEC) (10/70/20, v/v) with 2 wt% lithium bis(oxalate)borate (LiBOB). Biphenyl (BP) (0.5 wt% and 1 wt%) is employed as the in situ electrochemical coating additive for LiNi0.5Mn1.5O4 cathode. The results indicate the potential window of electrolyte without BP is up to 5.5 V versus Li/Li(+) on Pt electrode, but still decomposed seriously on both cathode and anode surfaces during prolonged cycles. The improved cycling performance with added 0.5 wt% BP in the control electrolyte can be attributed to the in situ electrochemical coating film on LiNi0.5Mn1.5O4 surface derived from BP electro-polymerization, which decreases the Mn dissolution and the lattice changes of LiNi0.5Mn1.5O4 cathode, and further inhibits Mn deposition and additional SEI formation on graphite surface. However, the thicker and compact BP electro-polymerization film using 1BP electrolyte on the cathode surface might inhibit the lithium intercalation/deintercalation and increase the polarization, then accelerates the capacity fading.

Influences of Additives on the Formation of a Solid Electrolyte Interphase on MnO Electrode Studied by Atomic Force Microscopy and Force Spectroscopy

The solid electrolyte interphase (SEI) that forms on electrodes largely defines the performances of lithium ion batteries (LIBs), such as cycling performance, shelf life, and safety. Additives in the electrolyte can modify the properties of the SEI and thus efficiently improve the performances of LIBs. However, the effects of additives on the mechanical properties, structure, and stability of the SEI have rarely been studied directly. In this paper, we report the influence of vinylene carbonate (VC) and lithium bis(oxalate)borate (LiBOB) additives on the mechanical properties of SEI films formed on MnO electrodes using atomic force microscopy (AFM) and force spectroscopy. The results show that the SEI formed from VC additive is thick and soft and partially decomposes upon charging. LiBOB forms thin, stiff, and electrochemically stable SEI films, but the stiff SEI may not be favorable for adapting the volume change of the electrodes. The VC and LiBOB mixed additive combines the advantages of the two components and produces stable SEI with moderate thickness and stiffness. This work also demonstrates that the AFM-force spectroscopy method is effective in investigating the structure and mechanical properties of SEI films.

Dimethyl sulfite as an additive for lithium bis(oxalate)borate/γ-Butyrolacton electrolyte to improve the performance of Li-ion battery

Dimethyl sulfite (DMS) is studied as an additive in lithium bis(oxalate)borate (LiBOB)/γ-Butyrolacton(GBL) electrolyte with LiCoO2 cathode and mesocarbon microbeads (MCMB) anode. Electrochemical performances of LiCoO2/DMS-electrolyte/Li and Li/DMS-electrolyte/MCMB half cells are studied by cyclic voltammetry, battery cycler, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Thermal behaviors of electrode–electrolyte coexisting systems are evaluated using a C80 micro-calorimeter. The electrochemical results show that the polarization of LiCoO2 is decreased and the capacity is improved with the addition of proper content of DMS. The XPS and SEM examination show that the presence of DMS decreases the decomposition of BOB anion and modifies the formation of SEI film on the surface of MCMB anode. The C80 micro-calorimeter analysis shows that the electrode materials with a LiBOB/GBL+proper DMS electrolyte begin to release heat at higher temperature and generate less heat than that with a common electrolyte. Therefore, using proper content (such as 20%) of DMS as an additive in LiBOB/GBL electrolyte is beneficial for the performance of Li-ion batteries.

Analytical Study of Surface Film on the Li Metal

Introduction Li metal is one of the most promising materials as a negative electrode because of its theoretical capacity > 3800 mAh g-1. However the formation of the dendritic lithium during the deposition process has to be prevented for the rechargeable batter applications. Though a lot of studies have been conducted to suppress the dendritic growth of lithium metal [1], it can be easily formed at a high current density or during a cycling process. Hence it still needs more studies to prevent the dendritic growth of the lithium metal completely. Recently we reported that the interfacial resistance of a lithium metal electrode and an electrolyte solution mainly consists of the lithium ion transfer in SEI film [2]. This result suggests that the ionic conductive property of the SEI significantly affects to the formation process of the dendritic lithium. In the present study, we investigated relationship between surface morphology of electrodeposited lithium and the SEI films using various electrolyte additives used in commercial Li ion batteries. Experimental A 1 mol dm-3 LiPF6EC:DEC (1:1 vol%) was employed as a standard electrolyte solution. Three additives: 5 vol% Vinylene carbonate (VC), 5 vol% Fluoroethylene carbonate (FEC) and 1 wt% Lithium bis(oxalate)borate (LiBOB), were added to the standard solution as the SEI formation source. The electrodeposition of the lithium was carried out using a two-electrode Swagelok cell. The deposited lithium electrodes were carefully rinsed with DEC and dried in argon filled glove box. The surface morphology of the deposited lithium was observed using SEM and the SEI film was analyzed by XPS. Results and Discussion Fig.1 shows SEM images of lithium electrodes deposited in the electrolyte solutions with / without VC. The lithium electrode from VC-free electrolyte showed a smooth surface morphology, while the electrodeposited lithium form the electrolyte solution with 5 vol% VC had dendritic-shaped deposits. It suggests that the difference of ion conductivity in the SEI films on the Li metal affects to the surface morphology of lithium as we expected. Fig. 2 shows XPS spectra of O 1s for the Li metal immersed in 1 mol dm-3 LiPF6 EC:DEC (1:1 vol%) with / without VC. In the case of the VC-free electrolyte, a relatively broad peak corresponds to lithium alkyl carbonate overlapped with a peak of Li2CO3 was observed while polyether like compounds form the surface film in the case of VC containing electrolyte solution. Furthermore Li2CO3and lithium alkyl carbonate was observed after 30 sec of argon etching process. Therefore it clearly shows that the SEI composition directly affects to the surface morphology of lithium. Further detailed discussion concerning the the SEI composition and surface morphology would will be presented and discussed in the meeting. Reference [1] K. Kanamura, S. Shiraishi, Z. Takehara, J. Electrochem. Soc., 143, 2187 (1996)[2] H. Kuwata, M. Matsui, N. Imanishi, of The 54thBattery Symposium in Japan, 1D18, 2013

Determination and Correlation of Solubilities of Lithium Bis(oxalate)borate in Six Different Solvents from (293.15 to 363.15) K

The solubility data of lithium bis(oxalate)borate (LiBOB) were measured in six different solvents using the synthetic method and laser monitoring technique at temperatures ranging from (293.15 to 363.15) K under atmospheric pressure. The experimental solubilities of LiBOB in different solvents were correlated by the modified Apelblat equations. It is found the calculated solubility data show good consistency with the experimental values. On this basis, some thermodynamic parameters of LiBOB in different solvents, such as dissolution enthalpy, dissolution entropy, and dissolution Gibbs free energy, are also calculated. These results concerning the solubility of LiBOB in different solvents will provide fundamental data in the commercial application of LiBOB.

Editorial: Energy Storage Materials: A Special Issue of Energy Technology

Editorial: Energy Storage Materials: A Special Issue of <i>Energy Technology</i>

Cover Picture: Investigation of the Decomposition Mechanism of Lithium Bis(oxalate)borate (LiBOB) Salt in the Electrolyte of an Aprotic Li–O2 Battery (Energy Technol. 4/2014)

Cover Picture: Investigation of the Decomposition Mechanism of Lithium Bis(oxalate)borate (LiBOB) Salt in the Electrolyte of an Aprotic Li–O₂ Battery (Energy Technol. 4/2014)

Electrolyte Additive Performance in Lithium Ion Batteries: From Coin Cells to 400-Mah Pouch Cells

Electrolyte additives have been widely reported to improve Lithium-Ion battery performance. Even small quantities of various additives have been shown to create stable SEIs on both the anode and cathode, improve safety, and stabilize electrolytes. Our work has focused on SEI forming additives that work on both the anode and cathode electrodes. Promising bi-functional additives that we have chosen to study in coin cells and larger format pouch cells are lithium bis(oxalate)borate (LiBOB) and lithium difloro(oxalate)borate (LiDFOB).As part of DOE’s Applied Battery Research for Transportation (ABR) Program, a high voltage and high capacity cathode was paired with a high capacity graphite anode for this study. This electrode couple has the potential for applications in plug-in hybrid (PHEV) and battery electric vehicles (EV). The cathode selected was from the LMR-NMC class of materials; Toda HE5050 ( Li1.2Ni0.15Mn0.55Co0.1O2) and the anode was A12 graphite from Phillips 66. Coin cells were assembled with these materials and tested with a number of different electrolyte and additive combinations. Several compositions have shown an improvement in the coin cell performance, shown in Figure 1.Based upon promising coin cell results from electrolyte and additive combinations, they were tested in 400-mAh pouch cells. The improved performance that was present in the coin cells was not observed in the pouch cells. Figure 2 shows the 400-mAh pouch cell performance of these additive combinations.This presentation examines the differences in coin cells and pouch cells relative to additive performance. Examples of these differences are: formation conditions, electrolyte quantity, additive concentrations, etc. By studying these conditions, we will be able to simulate and vary pouch cell conditions via coin cell analysis. The coin cell conditions and performance will be verified against 400-mAh pouch cell performance data to ensure that the conditions and performances are scalable. By following this process less battery materials will be required and will speed up the optimization process in pouch cells.Lastly, knowing the challenges that electrolyte additives present in scaling up cell size, we will provide some recommendations for coin cell testing that should be considered in the evaluation of research materials.

Investigation of the Decomposition Mechanism of Lithium Bis(oxalate)borate (LiBOB) Salt in the Electrolyte of an Aprotic Li–O2 Battery

AbstractThe stability of the lithium bis(oxalate) borate (LiBOB) salt against lithium peroxide (Li2O2) formation in an aprotic Li–O2 (Li–air) battery is investigated. From theoretical and experimental findings, we find that the chemical decomposition of LiBOB in electrolytes leads to the formation lithium oxalate during the discharge of a Li–O2 cell. According to density functional theory (DFT) calculations, the formation of lithium oxalate as the reaction product is exothermic and therefore is thermodynamically feasible. This reaction seems to be independent of solvents used in the Li–O2 cell, and therefore LiBOB is probably not suitable to be used as the salt in Li–O2 cell electrolytes.

탄소가 코팅된 일산화규소(SiO) 음극에서 전해질 첨가제로서 Lithium Bis(oxalato)borate의 영향

As an electrolyte additive, the effects of lithium bis(oxalate)borate (LiBOB) on the electrochemical properties of a carbon-coated silicon monoxide (C-coated SiO) negative elec- trode are investigated. The used electrolyte is 1.3 M LiPF6 that is dissolved in ethylene car- bonate (EC), fluoroethylene carbonate (FEC), and diethyl carbonate (DEC) (5:25:70 v/v/v) with or without 0.5 wt. % LiBOB. In the LiBOB-free electrolyte, the film resistance is not so high

Electrochemical performances of a novel lithium bis(oxalate)borate-based electrolyte for lithium-ion batteries with LiFePO4 cathodes

Lithium bis(oxalate)borate (LiBOB) is a promising salt for lithium-ion batteries. However, it is necessary to exert the electrochemical performance of LiBOB by the appropriate solvent. With dimethyl sulfite (DMS) as mixed solvents, the electrochemical behavior of γ-butyrolactone (GBL) with LiBOB is studied in this paper. It shows that LiBOB-GBL/DMS electrolyte has high oxidation potential (>5.3 V) and satisfactory conductivities. When used in lithium and mesophase carbon microbead cells, the novel electrolyte exhibits not only excellent film-forming characteristics but also low impedances of the interface films. Besides, when used in LiFeO4/Li cells, compared to the cell with the electrolyte system of 1 mol L−1 LiPF6–ethylene carbonate (EC)/dimethyl carbonate (DMC) (1:1, v/v), LiBOB-based electrolyte exhibits several advantages, such as more stable cycle performance at room temperature and higher mean voltage.

Effect of sulfolane on the morphology and chemical composition of the solid electrolyte interphase layer in lithium bis(oxalato)borate‐based electrolyte

To discuss the source of sulfolane (SL) in decreasing the interface resistance of Li/mesophase carbon microbeads cell with lithium bis(oxalate)borate (LiBOB)‐based electrolyte, the morphology and the composition of the solid electrolyte interphase (SEI) layer on the surface of carbonaceous anode material have been investigated. Compared with the cell with 0.7 mol l−1 LiBOB‐ethylene carbonate/ethyl methyl carbonate (EMC) (1 : 1, v/v) electrolyte, the cell with 0.7 mol l−1 LiBOB‐SL/EMC (1 : 1, v/v) electrolyte shows better film‐forming characteristics in SEM (SEI) spectra. According to the results obtained from Fourier transform infrared spectroscopy, XPS, and density functional theory calculations, SL is reduced to Li2SO3 and LiO2S(CH2)8SO2Li through electrochemical processes, which happens prior to the reduction of either ethylene carbonate or EMC. It is believed that the root of impedance reduction benefits from the rich existence of sulfurous compounds in SEI layer, which are better conductors of Li+ ions than analogical carbonates. Copyright © 2013 John Wiley &amp; Sons, Ltd.

Impact of Lithium Bis(oxalate)borate Electrolyte Additive on the Performance of High-Voltage Spinel/Graphite Li-Ion Batteries

The impact of lithium bis(oxalate)borate (LiBOB) electrolyte additive on the performance of full lithium-ion cells pairing the high-voltage spinel cathode with the graphite anode was systematically investigated. Adding 1 wt % LiBOB to the electrolyte significantly improved the cycle life and Coulombic efficiency of the full-cells at 30 and 45 °C. As the LiBOB was preferentially oxidized and reduced compared with LiBOB-free electrolyte during cycling, their relative contributions to the improved capacity retention in full-cells was gauged by pairing fresh and LiBOB-treated electrodes with various combinations. The results indicated that a solid–electrolyte interphase (SEI) film on graphite produced by the reduction of the LiBOB additive is more robust and stable against Mn dissolution problem during cycling at 45 °C compared with the SEI formed by the reduction of the base (LiBOB-free) electrolyte. In addition, a 3 wt % LiBOB-added electrolyte showed reduced Mn dissolution compared with the base electrolyte after storing the fully charged Li1–xNi0.42Fe0.08Mn1.5O4 (LNFMO) electrodes at 60 °C for one month. It is believed that LiBOB aids in stabilizing the electrolyte by trapping the PF5, i.e., sequestering the radical which tends to oxidize EC and DEC electrolyte solvents. Thus, oxidation is suppressed on the carbon black particles in the positive electrode, as evidenced by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR) analyses. As a result, HF generation is suppressed, which in turn results in less Mn dissolution from the spinel cathode.

Electrochemical performance of LiNi0.5Mn1.5O4 doped with la and its compatiblity with new electrolyte system

Cathode materials LiNi0.5Mn1.5O4 and LiNi0.5 − x/2LaxMn1.5 − x/2O4 (x = 0.04, 0.1, 0.14) were successfully prepared by the sol-gel self-combustion reaction (SCR) method. The X-ray diffraction (XRD) patterns indicated that, a few of doping La ions did not change the structure of LiNi0.5Mn1.5O4 material. The scanning electronic microscopy (SEM) showed that the sample heated at 800°C for 12 h and then annealed at 600°C for 10 h exhibited excellent geometry appearance. A novel electrolyte system, 0.7 mol L−1 lithium bis(oxalate)borate (LiBOB)-propylene carbonate (PC)/dimethyl carbonate (DMC) (1: 1, v/v), was used in the cycle performance test of the cell. The results showed that the cell with this novel electrolyte system performed better than the one with traditional electrolyte system, 1.0 mol L−1 LiPF6-ethylene carbonate (EC)/DMC (1: 1, v/v). And the electrochemical properties tests showed that LiNi0.45La0.1Mn1.45O4/Li cell performed better than LiNi0.5Mn1.5O4/Li cell at cycle performance, median voltage, and efficiency.