Lithium ion battery electrolyte
阅读说明：本技术 锂离子的电池电解质 (Lithium ion battery electrolyte ) 是由 斯特凡·勒泽 约翰内斯·卡斯纳特舍韦 拉尔夫·瓦格纳 雅舍尔·阿提克 贡特尔·布伦克劳斯 于 2018-06-13 设计创作，主要内容包括：本发明涉及一种包括电解质盐和溶剂的用于能量存储的电解质,其特征在于,溶剂包括根据通式(1)的至少一种化合物,通式(1)如下所示：<Image he="286" wi="536" file="DDA0002312880640000011.GIF" imgContent="drawing" imgFormat="GIF" orientation="portrait" inline="no"></Image>其中,R<Sup>1</Sup>、R<Sup>2</Sup>、R<Sup>3</Sup>、R<Sup>4</Sup>相同或不同,并且独立地选自包括直链或支链的C<Sub>1-6</Sub>烷基、C<Sub>2-6</Sub>烯基、C<Sub>2-6</Sub>炔基、C<Sub>3-6</Sub>环烷基和/或苯基的组,各自未被取代或者被选自包括F、CN和/或被氟单或多取代的C<Sub>1-2</Sub>烷基的组的取代基单或多取代。(The invention relates to electrolytes for energy storage comprising an electrolyte salt and a solvent, characterized in that the solvent comprises at least compounds according to formula (1), formula (1) being shown below: wherein R is 1 、R 2 、R 3 、R 4 Are the same or different and are independently selected from the group consisting of straight or branched chain C 1‑6 Alkyl radical, C 2‑6 Alkenyl radical, C 2‑6 Alkynyl, C 3‑6 CycloalkanesGroups of radicals and/or phenyl radicals, each unsubstituted or mono-or polysubstituted with C selected from the group comprising F, CN and/or with fluorine 1‑2 Substituents of the group of alkyl radicals are mono-or polysubstituted.)
electrolyte for energy storage comprising an electrolyte salt and a solvent, characterized in that said solvent comprises at least compounds of general formula (1), said general formula (1) being represented as follows:
wherein:
R1、R2、R3、R4are the same or different and are independently selected from the group consisting of straight or branched chain C1-6Alkyl radical, C2-6Alkenyl radical, C2-6Alkynyl, C3-6Cycloalkyl and phenyl, in each case unsubstituted or substituted by C, selected from the group consisting of F, CN and mono-or polysubstituted by fluorine1-2Taking of alkyl groupsThe substituent is mono-or polysubstituted.
2. The electrolyte of claim 1, wherein R is1、R2、R3、R4Are the same or different and are independently selected from the group consisting of unsubstituted C1-C5Alkyl or phenyl and substituted by fluorine, CN or CF3Mono-or polysubstituted C1-C5Groups of alkyl or phenyl groups.
3. The electrolyte of claim 1 or 2, wherein R is1、R2、R3、R4The same or different and independently selected from the group comprising methyl, ethyl, n-propyl and isopropyl.
4. The electrolyte according to any of the preceding claims, wherein the compound of formula (1) is selected from the group comprising 1,1,2, 2-tetramethoxyethane and 1,1,2, 2-tetraethoxyethane.
5. Electrolyte according to any of the preceding claims, characterized in that the solvent comprises the compound of formula (1) in the following amounts, based on the total weight of the electrolyte solvent: from 0.1% by weight or more to 100% by weight or less, preferably from 10% by weight or more to 80% by weight or less, more preferably from 20% by weight or more to 50% by weight or less, particularly preferably from 30% by weight or more to 50% by weight or less.
6. The electrolyte according to any of the preceding claims, wherein the electrolyte comprises an organic solvent selected from the group comprising ethylene carbonate, ethyl methyl carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, acetonitrile, propionitrile, 3-methoxypropionitrile, glutaronitrile, adiponitrile, pimelonitrile, γ -butyrolactone, γ -valerolactone, dimethoxyethane, 1, 3-dioxolane, methyl acetate, ethyl methanesulfonate, dimethyl methylphosphonate, linear or cyclic sulfones, symmetrical or unsymmetrical alkyl phosphates and mixtures thereof.
7. The electrolyte of claim 6, wherein the solvent is selected from the group consisting of propylene carbonate, ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, and mixtures thereof.
8, energy storage, in particular electrochemical energy storage selected from the group comprising lithium batteries, lithium ion batteries, rechargeable lithium ion batteries, lithium polymer batteries, lithium ion capacitors or supercapacitors, comprising an electrolyte according to any of claims 1 to 7.
method for forming a solid electrolyte interphase on an electrode of an electrochemical cell comprising an anode, a cathode and an electrolyte, wherein the cell operates with an electrolyte according to any of claims 1-7.
Use of compounds of general formula (1) shown below in energy storage, in particular in electrochemical energy storage selected from the group comprising lithium batteries, lithium ion batteries, rechargeable lithium ion batteries, lithium polymer batteries, lithium ion capacitors or supercapacitors:
wherein:
R1、R2、R3、R4are the same or different and are independently selected from the group consisting of straight or branched chain C1-6Alkyl radical, C1-6Alkenyl radical, C1-6Alkynyl, C3-6Cycloalkyl and phenyl, in each case unsubstituted or substituted by C, selected from the group consisting of F, CN and mono-or polysubstituted by fluorine1-2Mono-or polysubstituted with substituents of the group of alkyl radicals。
Technical Field
The present invention relates to the field of lithium ion batteries.
Background
Lithium ion batteries (secondary batteries) are currently the leading technology in the field of rechargeable batteries, especially in the field of portable electronics. Conventional lithium ion batteries typically employ graphite anodes. Charge transport is effected by an electrolyte comprising a lithium salt dissolved in a solvent. Various electrolytes and electrolyte salts are known in the art. Lithium hexafluorophosphate (LiPF) is commonly adopted in the conventional lithium ion battery at present6)。
A suitable electrolyte induces the formation of a Solid Electrolyte Interphase (SEI) on the electrode, which then prevents the graphite from reacting with the electrolyte further and in this way protects the electrolyte from reductive decomposition further and prevents the anode from being damaged by the co-intercalation of solvents.
However, reductive decomposition of the solvent propylene carbonate (IUPAC
It has been proposed to suppress exfoliation of graphite and reductive decomposition of solvents by using highly concentrated electrolytes. However, the use of highly concentrated electrolytes (also known as "solvent in salt" electrolytes) is not economical, since this approach requires multiples of the normally required amount of electrolyte salt. Furthermore, the concentration (usually > 3 mol. multidot.l)-1) The viscosity of the electrolyte is greatly increased, which results in a significant decrease in conductivity and battery performance. Furthermore, it would be expected that a decrease in the operating temperature results in a lower solubility product of the electrolyte salt than the concentration of the electrolyte salt in the electrolyte solvent, which results in the precipitation of the salt inside the battery. Furthermore, the density and hence the total mass of the electrolyte increases at a constant volume and the addition of electrolyte salt is increased. This also results in the specific energy density (Ah. kg) of the battery-1) As the overall system decreases.
Furthermore, it has been proposed to use additives of suitable properties. In commercial batteries, in particular, Vinylene Carbonate (VC) and fluoroethylene carbonate (FEC) are relevant here. Therefore, other agents that can prevent graphite exfoliation are needed.
Disclosure of Invention
It is an object of the present invention to provide an electrolyte that overcomes at least of the above-mentioned disadvantages of the prior art, in particular it is an object of the present invention to provide compounds that facilitate the formation of a solid electrolyte interphase on graphite, thus enabling reversible cycling of the electrolyte comprising propylene carbonate.
This object is achieved by an electrolyte for energy storage comprising an electrolyte salt and a solvent, characterized in that the solvent comprises at least compounds of formula (1), formula (1) being shown below:
wherein the content of the first and second substances,
R1、R2、R3、R4are the same or different and are independently selected from the group consisting of straight or branched chain C1-6Alkyl radical, C2-6Alkenyl radical, C2-6Alkynyl, C3-6Cycloalkyl and phenyl, in each case unsubstituted or substituted by C, selected from the group consisting of F, CN and mono-or polysubstituted by fluorine1-2Substituents of the group of alkyl radicals are mono-or polysubstituted.
Further advantageous embodiments of the invention can be derived from the dependent claims and the subclaims.
It has been surprisingly found that tetraalkoxyethane of formula (1) forms a Solid Electrolyte Interphase (SEI) on graphite electrodes, therefore, the use of tetraalkoxyethane of formula (1) in an electrolyte allows graphite electrodes to be used in solvents that do not form an effective SEI on graphite, such as propylene carbonate, where tetraalkoxyethane can be used as the only solvent or SEI additive or co-solvent for propylene carbonate electrolytes.
Unless otherwise indicated, the term "C" is used1-6Alkyl "or" C1-C6Alkyl "includes straight or branched chain alkyl groups having 1 to 6 carbon atoms. The term "C3-6-cycloalkyl "refers to a cyclic alkyl group having 3 to 6 carbon atoms. Unless otherwise indicated, the term "C" is used2-6-alkenyl "and" C2-6Alkynyl includes straight chains having from 2 to 6 carbon atoms and in each case at least double or triple bondsAn alkenyl or alkynyl group, which may be branched or unbranched.
Free radical R1、R2、R3、R4May be the same or different. Free radical R1、R2、R3、R4Preferably the same.
Preferably, C is taken into account1-C5An alkyl group. Preferred C unless otherwise stated1-C5The alkyl group includes a linear or branched alkyl group having 1 to 5 carbon atoms, and is preferably selected from the group consisting of a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a pentyl group, an isopentyl group, and a neopentyl group.
The alkyl, alkenyl or alkynyl group may be unsubstituted or mono-or polysubstituted, for example, di-or trisubstituted. Here, the alkyl, alkenyl or alkynyl group may be multiply substituted on various carbon atoms (preferably on the same carbon atom). The substituent may be fluorine or CN (nitrile). In which the radical R1、R2、R3、R4In substituted embodiments, it is preferably substituted with fluorine, e.g., mono-or polyfluorinated or perfluorinated. C3-C6The alkyl substituents may in particular bear CF3A group. C where alkyl, alkenyl, alkynyl or cycloalkyl or phenyl may also be substituted by small fluorine1-2Alkyl (especially CF)3) Mono-or polysubstituted.
In a preferred embodiment, R1、R2、R3、R4Are the same or different and are independently selected from the group consisting of unsubstituted C1-C5Alkyl (preferably C)1-C3Alkyl) or phenyl and substituted by fluorine, CN or CF3Mono-or polysubstituted C1-C5Alkyl (preferably C)1-C3Alkyl) or phenyl.
In another aspect, unsubstituted compounds are generally inexpensive and therefore more economical as solvents or cosolvents in lithium ion batteries1-C3The alkyl substituents may in particular be unsubstituted. In a preferred embodiment, R1、R2、R3、R4The same or different and are independently selected from the group consisting of methyl, ethylAnd (ii) a group of radicals, n-propyl and isopropyl, in particular selected from methyl and ethyl.
In a preferred embodiment, the compound of formula (1) is selected from among 1,1,2, 2-tetramethoxyethane and 1,1,2, 2-tetraethoxyethane. According to the IUPAC nomenclature, 1,1,2, 2-tetramethoxyethane is also referred to as 1,1,2, 2-ethanedicarboxylic acid tetramethyl ester and 1,1,2, 2-tetraethoxyethane is referred to as 1,1,2, 2-ethanedicarboxylic acid tetraethyl ester. 1,1,2, 2-tetramethoxyethane and 1,1,2, 2-tetraethoxyethane have the following general formulae (2) and (3):
in particular, it has been found that 1,1,2, 2-tetramethoxyethane and 1,1,2, 2-tetraethoxyethane are well suited as co-solvents for propylene carbonate to form an effective SEI on graphite that effectively inhibits co-intercalation of propylene carbonate into graphite, thus, for lithium ion technology, 1,1,2, 2-tetramethoxyethane and 1,1,2, 2-tetraethoxyethane are particularly suited as co-solvents or SEI additives or as only solvents.
In an embodiment, the solvent may comprise the compound of the general formula (1) in an amount of from 0.1% by weight or more to 100% by weight or less based on the total weight of the electrolyte solvent tetraalkoxyethane may be used as the sole solvent, furthermore tetraalkoxyethane may be used as the SEI additive, for example, the solvent may comprise the compound of the general formula (1) in an amount of from 0.1% by weight or more to 10% by weight or from 1% by weight or more to 5% by weight or less based on the total weight of the electrolyte solvent tetraalkoxyethane may preferably be used as a co-solvent for the propylene carbonate based electrolyte, the electrolyte preferably comprises the compound of the general formula (1) in an amount of from 10% by weight or more to 80% by weight or less, more preferably from 20% by weight or more to 50% by weight, particularly preferably from 30% by weight or more to 50% by weight or less, in an advantageous manner, in particular 30% by weight of 1,1,2, 2-tetramethoxyethane or 1, 2-tetraethoxyethane or 1, which may be efficiently embedded in a small amount of graphite such as a co-solvent, such as a co-alkoxy-1-2, or a co-tetraethoxyethane, which may be economically effective method, such as a co-2, or a co-solvent, such as a co-solvent, for example, tetraethoxyethane, and a solvent, and.
The electrolyte includes at least electrolyte salts, preferably lithium salts, and a solvent including a compound of formula (1). Here, the compound of formula (1) may be a solvent the electrolyte may also contain other solvents.
The electrolyte may comprise a solvent selected from the group consisting of non-fluorinated or partially fluorinated organic solvents, ionic liquids, polymer matrices, and mixtures thereof. The electrolyte preferably comprises an organic solvent, in particular a cyclic or linear carbonate. In a preferred embodiment, the organic solvent is selected from the group consisting of ethylene carbonate, ethyl methyl carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, acetonitrile, propionitrile, 3-methoxypropionitrile, glutaronitrile, adiponitrile, pimelonitrile, γ -butyrolactone, γ -valerolactone, dimethoxyethane, 1, 3-dioxolane, methyl acetate, ethyl methanesulfonate, dimethyl methylphosphonate, linear or cyclic sulfones, symmetric or asymmetric alkyl phosphate esters, and mixtures thereof.
In a preferred embodiment, the solvent is selected from the group consisting of propylene carbonate, ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate and mixtures thereof. In particular, the electrolyte may include a solvent (such as propylene carbonate) that does not result in the formation of an effective solid electrolyte interphase. Preference is given to propylene carbonate and mixtures of propylene carbonate with ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate and/or diethyl carbonate, in particular mixtures of propylene carbonate with dimethyl carbonate. When these solvents are used, it is particularly advantageous to add the compounds according to the invention to form an effective solid electrolyte interphase. Particularly preferred are 1,1,2, 2-tetramethoxyethane and 1,1,2, 2-tetraethoxyethane as co-solvents.
For example, it is preferable to include a mixture of 50% by weight of 1,1,2, 2-tetramethoxyethane and/or 1,1,2, 2-tetraethoxyethane with 50% by weight of propylene carbonate, based on the total weight of the electrolyte solvent. Preference is likewise given to mixtures comprising 1,1,2, 2-tetramethoxyethane and/or 1,1,2, 2-tetraethoxyethane and propylene carbonate, dimethyl carbonate in a weight ratio of 1:1:1 or 1:2: 2. Such a mixture may have good electrical conductivity and cause passivation of the graphite electrodes.
In addition to forming an effective SEI, advantages are that the use of tetraalkoxyethane can help improve the intrinsic safety of the electrolyte system by increasing the auto-ignition temperature compared to linear carbonates (such as dimethyl carbonate and diethyl carbonate). The auto-ignition temperatures of 1,1,2, 2-tetramethoxyethane and 1,1,2, 2-tetraethoxyethane are 47 ℃ to 53 ℃ and 71 ℃, respectively, while dimethyl carbonate and diethyl carbonate can auto-ignite at temperatures of 18 ℃ and 31 ℃, respectively.
The electrolyte may also be a polymer electrolyte selected from, for example, the group consisting of polyethylene oxide, polyacrylonitrile, polyvinyl chloride, polyvinylidene fluoride, poly (vinylidene fluoride-hexafluoropropylene copolymer), and polymethyl methacrylate to which an electrolyte salt is added, or a gel polymer electrolyte comprising a polymer, the above-mentioned organic solvent and/or ionic liquid, and an electrolyte salt. The electrolyte may also be formed from an ionic liquid and an electrolyte salt.
The electrolyte of the present invention comprises, in addition to the solvent and at least compounds of the general formula (1), at least electrolyte salts,in particular a lithium salt. The electrolyte salt is preferably selected from the group consisting of LiPF6、LiBF4、LiAsF6、LiSbF6、LiClO4、LiPtCl6、LiN(SO2F)2、LiN(SO2CF3)2、LiN(SO2C2F5)2、LiC(SO2CF3)3、LiB(C2O4)2、LiBF2(C2O4) And LiSO3CF3The group (2). The lithium salt is preferably selected from LiN (SO)2CF3)2(LiTFSI, lithium bis (trifluoromethanesulfonyl) imide), LiN (SO)2F)2(LiFSI) and LiPF6Among them. The concentration of the lithium salt in the electrolyte may be in a conventional range, for example, in the range of ≧ 1.0M to ≦ 1.5M. The use of relatively small amounts of electrolyte salts makes the electrolytes of the present invention more economical, particularly as compared to "salt-solvent" electrolytes.
In a preferred embodiment, the electrolyte comprises a mixture of compounds of formula (1) (in particular, 1,1,2, 2-tetramethoxyethane and/or 1,1,2, 2-tetraethoxyethane), at least lithium salts and propylene carbonate or an organic solvent comprising propylene carbonate the electrolyte may be prepared, for example, by mixing a compound of formula (1) with propylene carbonate or a compound of formula (1) with a solvent mixture comprising propylene carbonate and introducing a lithium salt into the solvent.
The electrolyte may further comprise at least additives, particularly selected from the group consisting of SEI formers, flame retardants, and overcharge additives, for example, the electrolyte may comprise a compound of formula (1) and further SEI formers, for example selected from the group consisting of fluoroethylene carbonate, vinyl chlorocarbonate, vinylene carbonate, ethylene carbonate, ethylene sulfite, propane sultone, propylene sultone, sulfite (preferably dimethyl and propylene sulfite, vinyl sulfate, propylene sulfate, methylene methane disulfonate, trimethylene sulfate, butyrolactone optionally substituted with F, Cl or Br, styrene carbonate, vinyl acetate, and propylene carbonate.
The compounds of the general formula (1) (in particular, 1,1,2, 2-tetramethoxyethane and 1,1,2, 2-tetraethoxyethane) are commercially available or can be prepared by methods that will be familiar to those skilled in the art.
The electrolyte is particularly suitable for use in batteries or rechargeable batteries, in particular as an electrolyte for lithium ion batteries or rechargeable lithium ion batteries.
The invention also provides energy stores, in particular electrochemical energy stores, selected from the group consisting of lithium batteries, lithium ion batteries, rechargeable lithium ion batteries, lithium polymer batteries, lithium ion capacitors and supercapacitors comprising the electrolyte according to the invention.
For the purposes of the present invention, the term "energy storage" includes times and secondary electrochemical energy storage devices, i.e., batteries ( times storage) and rechargeable batteries (secondary storage). in general language usage, rechargeable batteries are often referred to by the term "battery", which is often used as a generic term.
Secondary electrochemical energy storage is preferably considered. In particular, the energy storage is a lithium ion battery. It can be shown that the solid electrolyte interphase formed on the graphite anode is stable for at least 300 cycles. This allows economical operation of the rechargeable battery and use of the electrolyte.
In particular, the energy storage may comprise a compound of formula (1) and carbon (in particular graphite) and/or an electrolyte comprising propylene carbonate as electrode material. For example, a lithium ion battery comprising a cathode, a graphite anode, a separator (separator) and an electrolyte comprising a carbon-carbon composite in a weight ratio of 1:1 (particularly, 1,2,2, 2-tetramethoxyethane or 1,1,2, 2-tetraethoxyethane) and propylene carbonate, or a mixture comprising 1,1,2, 2-tetramethoxyethane and/or 1,1,2, 2-tetraethoxyethane and propylene carbonate and dimethyl carbonate in a weight ratio of 1:1:1 or 1:2:2, and further preferably 1M LiTFSI, LiFSI or LiPF6。
In principle, all electrolytes, solvents, electrolyte salts and counter electrodes known to the person skilled in the art and commonly used in energy storage, such as lithium ion batteries, can be used. For example, lithium metal, lithium titanate spinel (LTO), and carbon (particularly graphite) may be used as the anode material, and lithium iron phosphate (LFP) and lithium nickel manganese cobalt oxide (NMC) may be used as the cathode material.
The invention also provides a method of forming a solid electrolyte interphase on an electrode of an electrochemical cell comprising an anode, a cathode, and an electrolyte, wherein the cell operates using the electrolyte of the invention.
The present invention also provides the use of compounds of general formula (1) as shown below in energy storage, in particular in electrochemical energy storage selected from the group comprising lithium batteries, lithium ion batteries, rechargeable lithium ion batteries, lithium polymer batteries, lithium ion capacitors or supercapacitors:
wherein:
R1、R2、R3、R4are the same or different and are independently selected from the group consisting of straight or branched chain C1-6Alkyl radical, C1-6Alkenyl radical, C1-6-alkynyl, C3-6Cycloalkyl and phenyl, in each case unsubstituted or substituted by C, selected from the group consisting of F, CN and mono-or polysubstituted by fluorine1-2Substituents of the group of alkyl radicals are mono-or polysubstituted.
The compounds of formula (1) can be advantageously used as electrolyte additives, solvents or co-solvents, especially in electrolytes that do not add additives, do not form an effective SEI. In particular, the compounds of formula (1) can be advantageously used in energy storage comprising carbon (in particular graphite) as electrode material and/or an electrolyte comprising propylene carbonate. For the description of the compounds of the general formula (1), reference is made to the above description. 1,1,2, 2-tetramethoxyethane and 1,1,2, 2-tetraethoxyethane are particularly preferred.
Drawings
Examples and figures for illustrating the invention are presented below. Here, the drawings are shown as:
the reduction stability window for an electrolyte comprising 1M LiTFSI in a mixture of 1,1,2, 2-Tetramethoxyethane (TME) and Propylene Carbonate (PC) is shown in fig. 1a) of fig. 1, and the reduction stability window for an electrolyte comprising 1M LiTFSI in a mixture of 1,1,2, 2-Tetraethoxyethane (TEE) and Propylene Carbonate (PC) is shown in fig. 1b) of fig. 1. In each case, the current is plotted against the potential.
Fig. 2 shows the oxidation stability windows of the following electrolytes in a Pt/Li half cell: each electrolyte contained 1M LiTFSI in a mixture of 1,1,2, 2-tetraethoxyethane and Propylene Carbonate (PC) or a mixture of 1,1,2, 2-tetramethoxyethane and Propylene Carbonate (PC), and 1M LiFSI in a mixture of PC and 1,1,2, 2-tetramethoxyethane. The current density is plotted against the potential.
FIG. 3 shows LiMn2O4Window of oxidation stability of electrolytes comprising 1M LiFSI in a mixture of propylene carbonate and 1,1,2, 2-tetraethoxyethane in a Li half cell.
Fig. 4 shows the charge and discharge capacity (left vertical axis) and coulombic efficiency (right vertical axis) versus the number of charge/discharge cycles for the following electrolytes for graphite/Li batteries: the electrolyte contains 1M LiTFSI in a 1:1 mixture of propylene carbonate and 1,1,2, 2-tetraethoxyethane.
Fig. 5 shows the charge and discharge capacity and coulombic efficiency of the following electrolytes in LFP/graphite full cells as a function of the number of charge/discharge cycles: the electrolyte contains 1M LiTFSI in a 1:1 mixture of propylene carbonate and 1,1,2, 2-tetraethoxyethane.
Figure 6 shows the charge and discharge capacity and coulombic efficiency of the following electrolytes in NMC/graphite full cells as a function of the number of charge/discharge cycles: the electrolyte contained 1M LiFSI in a 1:1 mixture of propylene carbonate and 1,1,2, 2-tetraethoxyethane.
Fig. 7a) of fig. 7 shows the cell voltage course versus th cycle capacity for an electrolyte comprising 1M litfsi in a 1:1 mixture of propylene carbonate and 1,1,2, 2-tetraethoxyethane fig. 7b) of fig. 7 shows a scanning electron micrograph of a cross section of a surface secondary graphite particle after cycles in the electrolyte.
FIG. 8a) of FIG. 8 shows the cell voltage course over time for the th cycle for an electrolyte comprising 1M LiPF in propylene carbonate with 2 wt% FEC6Fig. 8b) of fig. 8 shows a scanning electron micrograph of the graphite surface after cycles in the electrolyte.
Detailed Description
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