WO2000038258A1 - Novel anodes for rechargeable lithium batteries - Google Patents
Novel anodes for rechargeable lithium batteries Download PDFInfo
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- WO2000038258A1 WO2000038258A1 PCT/US1999/024168 US9924168W WO0038258A1 WO 2000038258 A1 WO2000038258 A1 WO 2000038258A1 US 9924168 W US9924168 W US 9924168W WO 0038258 A1 WO0038258 A1 WO 0038258A1
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Definitions
- This invention relates to new anode materials for lithium ion batteries. More specifically this invention relates to new anode materials for lithium-ion batteries consisting of intermetallic materials having active and inactive metals with respect to lithium, such as for instance Sn and Cu metals, respectively.
- Lithium-ion batteries are under development for the consumer electronics market such as cellular phones, laptop computers, and camcorders. Lithium batteries are also being developed for high energy/power systems such as electric vehicles.
- a major concern about lithium batteries is safety, primarily when metallic lithium is used as the anode material. This arises because lithium has a very high oxidation potential and thus reactivity in the cell environment.
- One approach to the safety issue is to use carbon as a host structure for lithium.
- the carbon can be either graphite or a less crystalline form of pyrolyzed carbon.
- Lithium-intercalated graphite/carbon electrodes improve the safety of lithium cells, but do not completely overcome the safety problems, because there is still the possibility of depositing metallic lithium at the top of the charge when the voltage of the lithiated carbon/graphite anode approaches that of metallic lithium.
- Carbon itself when present in a finely divided form with a high surface area, can be highly reactive particularly if oxygen is released within the cell from a highly oxidizing cathode material such as Li]- x CoO 2 , Li ! . x NiO 2 , and L ⁇ JVIJ- ⁇ O.,.
- the electrochemical profile has indicated that the compositions of the stable phases are Li 2 Sn 5 , Li 2 Sn 3 , Li 7 Sn 3 , Li 5 Sn 2 , Li 7 Sn 2 and Li 22 Sn 5 .
- Tin-oxide electrodes suffer an irreversible capacity loss on the first cycle because a significant amount of the lithium is trapped within the charged electrode as lithium oxide.
- lithium oxide is an insulator, which reduces the electronic conductivity of the electrode, a serious disadvantage since for optimum performance the anode needs to be an electrical conductor.
- the invention relates to the use of intermetallic compounds, based on the structure types of copper-tin and lithium-copper-tin materials, as defined by their relationship to NiAs type, Ni 2 In type and lithiated zinc-blende-type materials as anode materials for rechargeable lithium batteries.
- the invention also includes non- aqueous electrochemical cells incorporating the new anodes and the methods of making the anodes and cells.
- an active metal which can alloy substantially with lithium (such as tin) and, in most instances, there is one or more of an inactive metal which does not substantially alloy with lithium (such as copper).
- the anode material components consist of two (or more) active metals that can alloy with lithium, such as tin and germanium.
- the invention also includes cells and batteries incorporating the new anode materials with standard state-of-the-art cathodes such as lithium cobalt oxide, lithium nickel oxide or lithium manganese oxides (and various substituted oxides), cathodes now useful in lithium rechargeable batteries.
- FIG. 1 depicts a schematic illustration of an electrochemical cell
- FIG. 2 is a representation of the ideal structure of a high-temperature Cu 6 Sn 5 intermetallic compound, labeled ⁇ -Cu 6 Sn 5 ;
- FIG. 3 is a representation of the ideal structure of NiAs
- FIG. 4 is a representation of the ideal structure of Ni 2 In;
- FIG. 5a is a [001] crystallographic projection of the high-temperature structure of ⁇ - Cu 6 Sn 5 shown in FIG. 2 showing the displacement of Sn atoms that is required for the transformation to a cubic Li x Cu 6 Sn 5 -type structure (x max ⁇ 13);
- FIG. 5b is a [001] crystallographic projection of the ideal structure of the room- temperature Cu 6 Sn 5 intermetallic compound, labeled ⁇ '-Cu 6 Sn 5 , showing the displacement of Sn (or Cu) atoms that is required for the transformation to a cubic Li x Cu 6 Sn 5 -type structure;
- FIG. 6 is a [001] crystallographic projection of the ideal structure of the Ni 3 Sn 2 (and Co 3 Sn 2 ) intermetallic compound
- FIG. 7 shows the X-ray diffraction patterns (Cut radiation)of a) a standard Cu 6 Sn 5 sample at room-temperature, b) Li x Cu 6 Sn 5 obtained by electrochemical insertion of lithium at room temperature, c) a standard Li 2 CuSn sample at room temperature, and d) a chemically delithiated sample of Li 2 CuSn at room temperature;
- FIG. 8a is a representation of the ordered room-temperature structure of Li 2 CuSn;
- FIG. 8b is a representation of the disordered high-temperature structure of Li 2 CuSn;
- FIG. 8c is a representation of the zinc-blende type CuSn framework of the Li 2 CuSn structure shown in FIG. 8a;
- FIG. 9 is a [001] crystallographic projection of the ordered structure of Li 2 CuSn shown in FIG. 8a;
- FIG. 10 shows the in-situ X-ray diffraction data (CuK Continue radiation) of a Li/Li x Cu 6 Sn 5 cell
- FIG. 11 is an electrochemical profile of the first four discharge and three charge cycles of a Li/Sn cell between 1.2 volts and 0.0 volts;
- FIG. 12 is a graphical representation similar to FIG. 11 for a Li/Cu 6 Sn 6 cell
- FIG. 13 is a graphical representation similar to FIG. 11 for a Li/Cu 6 Sn 5 cell
- FIG. 14 is a graphical representation similar to FIG. 11 for a Li/Cu 6 Sn 4 cell
- FIG. 15 is a graphical representation similar to FIG. 11 for a Li/Li 2 CuSn cell
- FIG. 18 shows the X-ray diffraction pattern (CuK « radiation) of aNi 3 Sn 2 sample at room- temperature;
- FIG. 19 shows the X-ray diffraction pattern (CuK « radiation) of a Li 2 AgSn sample at room-temperature
- FIG. 20 shows the X-ray diffraction patterns (CuK ⁇ radiation) of (a) an InSb sample at room temperature, (b) a Li x InSb electrode lithiated to 0.5 V vs. Li, and (c) a cycled Li x InSb electrode after lithium extraction to 1.2 V vs. Li;
- FIG.21 is a graphical representation similar to FIG. 11 for the first 18 cycles of a Li/InSb cell cycled between 1.2 volts and 0.5 volts;
- FIG.22 is a graphical representation similar to FIG. 16 for the first 22 cycles of a Li/InSb cell cycled between 1.2 volts and 0.5 volts;
- FIG. 23 is an expanded graphical representation similar to FIG. 21 for the 10 th cycle of a Li/InSb cell cycled between 1.2 volts and 0.5 volts;
- the invention relates to a new anode for use in an electrochemical cell 10 having an anode 12 separated from a cathode 16 by an electrolyte 14, all contained in an insulating housing 18 with suitable terminals (not shown) being provided in electronic contact with the anode 12 and the cathode 16, as shown schematically in Fig. 1.
- Binders and other materials normally associated with both the electrolyte and the anode and cathode are well known and are not described herein, but are included as is understood by those of ordinary skill in this art.
- the anodes of the present invention include intermetallics comprising a substantially active element (or elements) which alloys with lithium with a substantially inactive element (or elements) which does not alloy with lithium, or alternatively, comprising a combination of substantially active alloying elements, the anodes having structure types based on the copper-tin compound Cu 6 Sn 5 and lithium-copper-tin derivatives, such as the compound Li 2 CuSn.
- Metals which are considered active, that is metals which can form a binary alloy with lithium useful in this invention are preferably one or more of Sn, Si, Al, Ga, Ge, In, Bi, Pb, Zn, Cd, Hg and Sb.
- the substantially inactive elements which do not form substantial binary alloys with Li are selected preferably from the first row of transition metals and more preferably one or more of Cu, Ni, Co, Fe, Mn, Cr, Ti, V and Sc, and in addition, Mg and Ag along with the noble metals, Pd, Rh, and Ir. More specifically, the preferred combinations of inactive and active metals are Cu and Ni, and one or more of Sn, Ge, Sb, Si and Al. It is understood that the active and inactive metals may be present in a wide variety of ratios as will hereinafter be described with the Cu 6 Sn 5 and Li 2 CuSn intermetallic compounds, by way of example only. It should be understood that various combinations, relative amounts and relative "activities" of both the inactive metals and the active metals may be used in the context of intermetallic compounds without departing from the true spirit and scope of the present invention.
- M intermetallic compound
- M' is an "active" alloying element
- M' is an "inactive” element (or elements)
- MnO 2 metal oxide insertion electrode
- MnO 2 host electrode lithium ions are inserted into the structure to a composition LiMnO 2 with a concomitant reduction of the manganese ions from a tetravalent to a trivalent state.
- MnO 2 the ratio of the inactive element to active element is 2:1; for the uptake of one lithium ion per manganese ion, the capacity of the MnO 2 electrode is 308 mAh/g.
- Manganese oxides, such as the spinel-related phase, ⁇ -MnO 2 that expand and contract isotopically during lithium insertion and extraction with minimal volume expansion of the unit cell provide greatly enhanced cycling stability compared to manganese oxide structures that expand and contract anisotopically with a large volume increase, as in the ramsdellite-Li x MnO 2 structure.
- the tin atoms can be regarded, broadly speaking, as the electrochemically active component (because it forms a binary Li x Sn alloy system with Li) and the copper atoms as the inactive component, (because it does not substantially alloy with Li).
- Lithium insertion into the Cu 6 Sn 5 structure takes place initially in a topotactic reaction to yield a structure, believed to have the nominal composition Li 13 Cu 6 Sn 5 , or Li 2 17 CuSno 83 , i.e., with a maximum of 13 Li per Cu 6 Sn 5 formula unit, which is approximately the same as that of Li 2 CuSn.
- the Cu 6 Sn 5 structure provides a host framework for the uptake of lithium. It is believed that further reaction with lithium necessitates a displacement reaction and a break-up of the Li x Cu 6 Sn 5 structure; the lithium combines with the active tin to form a series of Li x Sn compounds (0- ⁇ x ⁇ 4.4) within a residual copper matrix.
- the divided copper atoms/particles that are produced on electrochemical cycling would provide an electronically conducting matrix to contain the lithiated tin particles and to accommodate at least some of the damaging expansion contraction of the Li x Sn particles during discharge and charge (note that in a Li/Cu 6 Sn 5 cell, extensive discharge means the formation of a "Li x Cu 6 Sn 5 " composite electrode (with x > ⁇ 13) consisting of domains of lithiated tin and copper metal).
- the invention also includes the composite electrodes that are derived over longer-term cycling by the displacement reaction described above and which can yield higher capacities than can be obtained from the topotactic reaction alone.
- the Cu 6 Sn 5 structure exists in a high temperature form and a low temperature form. The transition from the one form to the other takes place at 460K as previously reported.
- the high-temperature structure of Cu 6 Sn 5 labeled ⁇ -Cu 6 Sn 5 and shown in Fig. 2, was first reported in 1928 to have the Ni As-type structure.
- ⁇ -Cu 6 Sn 5 has a defect NiAs structure in which the Cu atoms adopt the octahedral sites occupied by Ni in NiAs, and the Sn atoms occupy the trigonal prismatic sites adopted by As; there is one vacant trigonal prismatic Sn site per Cu 6 Sn 5 unit.
- a recent analysis in 1994, of the room-temperature Cu 6 Sn 5 structure, labeled ⁇ '-Cu 6 Sn 5 has shown that this compound has features of both a NiAs-type and a Ni 2 In-type structure.
- NiAs structure which has a hexagonal-close-packed AB ACABAC arrangement of atoms (Fig. 3a)
- the Ni atoms are octahedrally coordinated to six As atoms, whereas the As atoms are coordinated in trigonal prismatic manner to six Ni atoms.
- the [001] crystallographic projection of the NiAs structure in Fig. 3 shows that the Ni and As atoms are arranged in strings. There are twice as many As strings as Ni strings. The Ni strings are densely packed, whereas the As strings contain half as many As atoms as there are Ni atoms in the Ni strings.
- the NiAs structure is seen to consist of an array of hexagonal columns, each column consisting of alternating Ni strings and As strings, and each column containing an As string at its center.
- Ni 2 In The [001] crystallographic projection of the Ni 2 In structure is shown in Fig. 4.
- Fig. 4 there is a similar hexagonal arrangement of atom strings as described for NiAs (Fig. 3).
- strings of Ni atoms octahedrally coordinated to surrounding In atoms
- strings containing both In and Ni atoms alternate with strings containing both In and Ni atoms to make up the hexagonal columns.
- Each hexagonal column contains, at its center, a similar string of In and Ni atoms.
- ⁇ '-Cu 6 Sn 5 there exist hexagonal columns that consist of Cu strings that alternate with Sn-Cu strings; the center of the hexagonal columns contain identical Sn-Cu strings.
- ⁇ '-Cu 6 Sn 5 may be regarded as having a defect Ni 2 In-type structure in which 80% of the trigonal bipyramidal sites are vacant.
- Intermetallic compounds that are assigned either to the NiAs- or the Ni 2 In-type structure commonly have a composition between that of NiAs and Ni 2 In.
- a superstructure is formed if the structure is ordered. Examples of such superstructures are found in room-temperature modifications of ⁇ '-Cu 6 Sn 5 , Ni 3 Sn 2 , and Co 3 Sn 2 intermetallic compounds.
- the [001] crystallographic projection of the Ni 3 Sn 2 structure (which is isostructural with Co 3 Sn 2 ) is shown in Fig. 6; it demonstrates that Ni 3 Sn 2 (and Co 3 Sn 2 ) is of the same structure type as ⁇ '-Cu 6 Sn 5 (Fig. 5b). In practice, however, it is believed that these structures are not ideally ordered and that some disorder can exist, for example between the copper and tin atom sites in the Cu 6 Sn 5 structures shown in Figs. 5 a and 5b.
- An important aspect of this invention is the discovery by combined electrochemical and in-situ X-ray diffraction studies of Cu 6 Sn 5 electrodes in lithium cells, that lithium can be inserted topotactically into the Cu 6 Sn 5 structure and that this process is reversible. It is believed, however, that the degree to which the lithium insertion reaction takes place is highly dependent on structural features of the intermetallic electrode, such as anti-site disorder and the reaction conditions under which the intermetallic electrodes are made.
- the X-ray diffraction data of various lithiated and delithiated samples (Fig. 7a-d) showed that the lithiated phase Li x Cu 6 Sn 5 (Fig. 7b) has an X-ray pattern similar to that of Li 2 CuSn (Fig.
- the structure of Li 2 CuSn has cubic symmetry.
- the room-temperature form of Li 2 CuSn space group symmetry F-43m
- the Sn atoms and one-half of the Li atoms form two interlinked face-centered-cubic arrays.
- the Cu atoms and remaining Li atoms occupy interstitial sites located at the center of cubes defined by 4 Sn and 4 Li atoms of the face-centered-cubic arrays.
- the high-temperature phase of Li 2 CuSn has higher symmetry, Fm-3m. In this case, the Li and Cu atoms within the cubes are randomly disordered, as shown in Fig.
- a Heusler-type phase such as Ni 2 MnGa, in which the Ni atoms occupy the same sites as the disordered Li and Cu atoms in Fig. 8b, and the Mn and Ga atoms occupy the sites of the Sn and remaining Li atoms, respectively.
- Li 2 CuSn may be regarded as having a lithiated zinc-blende-type structure in which the Li atoms occupy the interstitial sites of the CuSn host framework.
- the invention thus includes zinc-blende-type framework structures as insertion electrodes for lithium batteries.
- Other examples of such a zinc-blende- type framework structure is provided by the AgSn component in Li 2 AgSn and by the MgSi component in Li 2 MgSi.
- Additional examples of zinc-blende-type structures are AlSb, GaSb, and InSb.
- the ordered Li 2 CuSn structure as depicted in a second representation of the structure in Fig. 9, bears a close relationship to the ⁇ -Cu 6 Sn 5 structure (Fig. 5a); this relationship, which is seen in the arrangement of the hexagonal columns, makes it easy to understand the topotactic reaction when lithium is inserted electrochemically into ⁇ -Cu 6 Sn 5 . It is apparent from the X-ray diffraction data in Fig. 10 obtained in-situ in an electrochemical cell that the lithiation process involves a two-phase reaction.
- phase transformation from ⁇ -Cu 6 Sn 5 to the Li 2 CuSn-type structure can be understood if lithium insertion into the hexagonal columns of ⁇ -Cu 6 Sn 5 displaces the Sn atoms from the center of the columns into the trigonal bipyramidal interstitial sites in neighboring Sn strings, as shown by the arrows in Fig. 5a.
- full lithiation of ⁇ -Cu 6 Sn 5 with an ideal defect NiAs-type structure would result in the composition Li 13 Cu 6 Sn 5 (alternatively, Li 2 17 CuSno 83 or Li 2 Cu ⁇ Sno g3 Li 0.
- each Sn atom and each Cu atom is coordinated tetrahedrally to neighboring Cu and Sn atoms, respectively, in a zinc-blende-type structure.
- This topotactic reaction is reversible. Lithium insertion into the room-temperature structure, ⁇ '-Cu 6 Sn 5 (Fig. 5b), in which Cu atoms partially occupy 20% of the interstitial trigonal bipyramidal sites can occur by a similar reaction mechanism described for ⁇ -Cu 6 Sn 5 above.
- lithium insertion into ⁇ '-Cu 6 Sn 5 may initially occur by the occupation of the interstitial trigonal bi-pyramidal sites by lithium before the transformation to the zinc- blende-type structure.
- the initial lithiated Li x Cu 6 Sn 5 products can be lithiated to a NiAs-type structure before converting to a lithiated zinc-blende-type structure.
- the invention is thus extended to incorporate such lithiated NiAs-type structures.
- the invention therefore extends to include the family of compounds having structures related to the NiAs, Ni 2 In, Cu 6 Sn 5 and Li 2 CuSn structure types shown in Figs. 3, 4, 5a, 5b, 8a, 8b and 8c.
- Ni 3 Sn 2 (and Co 3 Sn 2 ) structure shown in Fig. 6 is remarkably similar to that of ⁇ '-Cu 6 Sn 5 (Fig. 5b), having strings of Ni, and strings of Sn-Ni arranged in identical fashion to the strings of Cu and Sn-Cu in ⁇ '-Cu 6 Sn 5 .
- the difference between Ni 3 Sn 2 (Co 3 Sn 2 ) and ⁇ '-Cu 6 Sn 5 structures is only in the number of interstitial trigonal bipyramidal sites occupied by the Ni (Co) and Cu atoms, respectively, in the Sn strings.
- Ni 3 Sn 2 may, in principle, accommodate lithium to the composition Li 3 Ni 3 Sn 2 , or in Li 2 CuSn notation, to the composition (Li, 5 Ni 05 )NiSn; it offers a lower gravimetric capacity (195 mAh g) and volumetric capacity (1755 mAh/ml) compared to ⁇ -Cu 6 Sn 5 and ⁇ '-Cu 6 Sn 5 (Table 1).
- Table 2 illustrates the wide variety of compounds that can exist with the Li 2 CuSn structure.
- the hexagonally shaped channels in Li 2 CuSn-type structures accommodate the inserted lithium.
- a particular embodiment of the invention therefore includes those isostructural materials in which non-lithium metals, M, occupy the Cu and Sn atom sites of Li 2 CuSn shown in Fig. 8a.
- M non-lithium metals
- One such example is Li 2 AgSn, the X-ray diffraction pattern of which is shown in Fig. 19.
- Another particularly attractive example is Li 2 MgSi because Mg and Si are relatively light and inexpensive materials.
- the invention also includes those structures in which at least some M sites are occupied by Li. This is believed to occur in Li x Cu 6 Sn 5 electrodes.
- Cu 6 Sn 5 can be represented CuSno 83 D 0. ⁇ 7 where D refers to a vacancy.
- D refers to a vacancy.
- the ideal Li 2 CuSn-type structure is reached at the composition Li 2 Cu(Sno .83 Li 0 17 ), or alternatively Li 2 17 CuSno .83 , or alternatively Li 13 Cu 6 Sn 5 .
- 17% of the Sn sites are occupied by Li.
- Cu 6 Sn 5 provides an electrode with a theoretical gravimetric capacity and a theoretical volumetric capacities of 358 mAh/g and 2506 mAh/ml, respectively, compared to the theoretical capacities of graphite, viz., 372 mAh g and 818 mAh/ml (Table 1).
- a particular advantage of Cu 6 Sn 5 -type electrodes, therefore, is that they offer a significantly enhanced volumetric capacity to carbon.
- the Cu atoms and one half of the Li atoms are disordered over the sites they normally occupy in the ideal, ordered structure at room-temperature (Fig. 8a). In practice, it is believed that at room temperature some disorder exists between these sites. This invention thus extends to include these disordered structures.
- the ratio of inactive element to active element is 2:1 which is approximately twice the ratio in Cu 6 Sn 5 (1.2:1). Therefore, it is believed that increasing the inactive copper content as a separate Cu phase in the intermetallic electrode would provide greater cycling stability; conversely, increasing the active tin content as a separate Sn phase probably would reduce the cycling stability of the intermetallic electrode.
- Li/Cu 6 Sn 5+ ⁇ cells were evaluated with electrodes having ⁇ values of -1 (Cu 6 Sn 4 , copper-rich), 0 (Cu 6 Sn 5 ) and +1 (Cu 6 Sn 6 , tin-rich).
- the electrochemical behavior of a standard Li/Sn cell was determined, for comparison.
- the electrochemical profiles of the first two discharge - and subsequent charge cycles of a Li/Sn cell and LiCu 6 Sn 5+ ⁇ cells ( ⁇ - 0, ⁇ 1) charged and discharged between 1.2 and 0.0 V are shown in Figs. 11-14.
- Electrochemical extraction from the intermetallic phase Li 2 CuSn occurs with a steadily increasing voltage to the cut-off potential, 1.2 V (see Fig. 15). On the subsequent discharge, the electrode does not show the characteristic plateau at 400 mV, but rather shows a continuous decrease in voltage to 0V.
- Li 2 CuSn electrodes compared to Cu 6 Sn 5 electrodes observed in these initial tests is attributed to the high reactivity of the Li 2 CuSn phase (particularly in moist air), and to the difficulty of assembling Li 2 CuSn electrodes and cells without some degradation of the electrode. From this viewpoint, it is clearly advantageous to load cells with unlithiated electrodes, such as Cu 6 Sn 5 rather than with Li 2 CuSn electrodes.
- Li 7 Sn 3 for example, Li 7 Sn 3 to Li 44 Sn
- the available capacity becomes more attractive, see Table 3.
- Li 13 Cu 6 Sn 5 which is believed to represent the maximum uptake of Li by the ideal ⁇ -Cu 6 Sn 5 structure
- the Li:Sn ratio is 2.6:1 which is close to that in Li 7 Sn 3 (2.3:1).
- lithium-metal alloy systems have high crystallographic densities, they provide significantly higher volumetric capacities than lithiated carbon, LiC 6 (-750 mAh ml).
- Cu 6 Sn 5 has a density of 8.28 g/ml; it will, therefore, provide a volumetric capacity of approximately 2450 mAh ml when discharged to a Li 7 Sn 3 composition (Li n 67 Cu 6 Sn 5 ).
- a major advantage of these intermetallic electrodes, therefore, is that they will occupy less volume than lithiated carbon electrodes for a given capacity value.
- a pure tin electrode provides a significantly higher capacity on the initial discharge (-670 mAh/g) than copper-tin electrodes, the capacity of the pure tin electrodes decreases rapidly on cycling, dropping to - 115 mAh g after 10 cycles.
- Cu 6 Sn 6 , Cu 6 Sn 5 , and Cu 6 Sn 4 electrode powders that were not subjected to high-energy ball milling deliver 350,340 and 440 mAh/g on the initial discharge, and 180, 175 and 280 mAh/g after 10 cycles, respectively.
- the Cu 6 Sn electrode delivers an initial capacity of 165 mAh/g, which increases on cycling as the electrode is "conditioned”; it delivers a steady 190 mAh/g after 10 cycles, see Fig. 17.
- This extra stability is attributed to two major factors: 1) the reversible topotactic reaction of lithium into the Cu 6 Sn 5 component, and 2) to the presence of an inactive, electronically copper component that serves to counter the deleterious volumetric expansion/contraction of any binary Li x Sn alloys that might be formed during cycling, particularly towards the end of discharge when the lithium concentration at the copper-tin intermetallic surface exceeds the limit allowed by the topotactic lithium insertion reaction, i.e., in excess of the lithium content in Li_ 13 Cu 6 Sn 5 .
- a further example of the stability of the intermetallic insertion electrodes of the present invention is given with respect to the compound InSb with a zinc-blende-type structure.
- Fig. 20a shows the X-ray diffraction pattern of an initial InSb electrode having the zinc-blende-type structure.
- Figs. 20b and 20c show the patterns of a Li x InSb electrode after the initial electrochemical lithiation of a Li InSb cell to a 0.5 volt and subsequent delithiation reaction to 1.2 volt, respectively.
- the X-ray diffraction pattern of the Li x InSb electrode at 0.5 volt resembles that of the parent InSb structure (Fig. 20a) but has a cubic lattice parameter 6.553 A which is slightly larger than that of InSb (6.475 A), as reflected by the slight shift of the peaks to lower two-theta values.
- Figs. 21 and 22 The voltage profiles of the first 18 cycles of a Li/InSb cell and the capacity vs. cycle number plot for the first 22 cycles are shown in Figs. 21 and 22, respectively. It can be seen from Figs. 21 and 22 that, apart from the first lithiation reaction, the electrochemical reaction is reversible when cells are cycled between 1.2 and 0.5 V. The exact reasons for the initial capacity loss on the first two cycles (450 to 290 mAh/g, 64%) are unknown, although it can be speculated that this may be due to surface oxidation of the intermetallic electrode materials during processing. It is believed that this capacity loss can be reduced by improved processing techniques under inert conditions.
- the invention also includes intermetallic electrodes with additional lithium in the starting electrode, either as free lithium metal, or lithium as an integral part of the intermetallic electrode structure to compensate for any lithium that may be irreversibly locked within the negative intermetallic electrode during the initial lithiation reaction (charge) of the electrochemical cell.
- Li/InSb cell shown in Fig. 23.
- Lithium insertion into InSb to form Li 2 InSb is consistent with the two-stage reaction process that occurs between approximately 900 mN and 650 mV vs. Li in the expanded plot of cycle 10 in Fig. 24 because the two lithium atoms in the Li 2 InSb are located in two crystallographically independent positions and hence have different site energies. Therefore, the data in Figs.
- This invention is thus extended to include overlithiated intermetallic zinc-blende electrode structures, and particularly those with a Li 3 Sb-type structure. Furthermore, an additional advantage of the Li 3 Sb-type structure is that it can be used as an excellent end-of- charge indicator to signal full lithiation of the Li 2 InSb-zinc-blende-type electrode structures.
- the copper atoms of the Cu 6 Sn 5 (NiAs-type) structure were partially replaced by Zn or Ni atoms, thus increasing and reducing the number of valence electrons associated with the metal elements in the structure, respectively.
- These compounds showed enhanced electrochemical behavior to Cu 6 Sn 5 .
- Figure 25 shows the typical charge/discharge profiles for cycles 4 to 7 of a Li/Cu 6 . x Zn x Sn 5 cell when cycled between 1.2 and 0.2 V.
- These samples were prepared in the presence of 3-5 w/o (weight percent) carbon, thereby allowing for the substitution of carbon atom for some of the metal atoms. If other non-metals were substituted for carbon, then these non-metals would also substitute for some of the metal atoms.
- zinc-blende structures exist that are comprised of a metal atom and a non-metal atom, well known examples being the mineral zinc-blende itself, ZnS, and also AgO, GaP, and ZnSe, that contain the non-metal elements S, O, P and Se, respectively.
- the invention also includes those intermetallic compounds defined above in which the metal atoms can be at least partially substituted by a non-metal element, the intermetallic compound preferably containing less than 50 atom percent of a non-metal element, more preferably less than 20 atom percent of a non-metal element, and most preferably less than 10 atom percent of a non- metal element, the non-metals being selected from one or more of B, C, N, O, F, P, S, Cl, As, Se, Br, Te and I.
- This invention thus also embodies electrode intermetallic host structures that transform on lithiation to a lithiated zinc-blende-type structure in the presence of an additional substantially inactive (non-alloying) element (or elements) with respect to lithium, or alternatively, an additional substantially active alloying element (or elements) with respect to lithium, or both.
- the invention also encompasses the use of carbonaceous additives, such as graphite and pyrolyzed carbons, to the intermetallic negative electrode, thereby providing a composite electrode structure or composite matrix to improve the current collection around electronically disconnected particles. Additional advantages of carbonaceous additives are that they can also contribute to the overall electrochemical capacity of the negative electrode and to provide end-of-charge indicators to prevent overlithiation of the intermetallic electrode materials.
- Cu 6 Sn 5 was synthesized by reacting metallic tin and metallic copper in stoichiometric amounts at 400 °C under argon for 12 hours. The sample was ground by mechanical milling to an average particle size of less than 10 microns. X-ray diffraction data, collected on a Siemens D5000 powder diffractometer with CuK ⁇ radiation showed that the Cu 6 Sn 5 product was an essentially single-phase product as shown in Fig. 7a.
- the samples were ground by mechanical milling to an average particle size of less than 10 microns.
- the copper-rich and tin-rich materials showed the characteristic peaks of Cu 6 Sn 5 and additional peaks of copper and tin metal, respectively.
- Li 2 CuSn was prepared by heating lithium metal, copper metal and tin metal at 900 °C under argon for 3 hours. The sample was ground by mechanical milling to an average particle size of less than 40 microns. X-ray diffraction data, collected on a Siemens D5000 powder diffractometer with CuK ⁇ radiation showed that the Li 2 CuSn product was an essentially single- phase product as shown in Fig. 7c.
- Li 2 CuSn was chemically delithiated by reaction with NOBF 4 in acetonitrile at room temperature.
- X-ray diffraction data, collected on a Siemens D5000 powder diffractometer with CuK ⁇ radiation showed that the product was an essentially single-phase product with a Cu 6 Sn 5 - type structure as shown in Fig. 7d.
- Ni 3 Sn 2 was synthesized by reacting metallic tin and metallic nickel in stoichiometric amounts at 650 °C under argon for 12 hours. The sample was ground by mechanical milling to an average particle size of less than 40 microns. X-ray diffraction data, collected on a Siemens D5000 powder diffractometer with CuK ⁇ radiation showed that the Ni 3 Sn 2 product was an essentially single-phase product as shown in Fig. 18.
- Li 2 AgSn was prepared by heating lithium metal; silver metal and tin metal at 900 °C under argon for 3 hours. The sample was ground by mechanical milling to an average particle size of less than 40 microns. X-ray diffraction data, collected on a Siemens D5000 powder diffractometer with CuK ⁇ radiation showed that the Li 2 AgSn product was an essentially single- phase product as shown in Fig. 19.
- InSb was prepared by ball-milling indium metal and antimony metal powder at room temperature in air for 20 hours. Thereafter, the sample was annealed under argon for 10 hours at 400°C, and subsequently ground to an average particle size of less than 40 microns. X-ray diffraction data, collected on a Siemens D5000 powder diffractometer with CuK ⁇ radiation showed that the InSb product was an essentially single-phase product as shown in Fig. 20a.
- the intermetallic materials were evaluated as electrodes in coin cells (size 1225) 12 mm diameter and 2.5 mm high against a counter lithium electrode.
- the cells had the configuration: Li/IM LiPF 6 in ethylene carbonate, diethyl carbonate (50:50)/Intermetallic electrode.
- laminates were made containing approximately 6 mg (81%) of the intermetallic compound, intimately mixed with 10% (by weight) binder (Kynar 2801) and 9% (by weight) carbon (XC-72) in tetrahydrofuran (THF).
- Metallic lithium foil was used as the counter (negative) electrode.
- Li/Copper-tin cells were charged and discharged at constant current (generally at 0.1 mA), within the voltage range of either 1.2 to 0.0 V, or 1.2 to 0.2 V and Li/InSb cells within the voltage range of 1.2 to 0.5 volts.
- the electrochemical data from the various intermetallic electrodes are shown in various electrochemical plots, as in Fig. 10: a Li/Cu 6 Sn 5 cell; Fig. 11 : a Li/Sn cell (reference); Fig. 12: a Li/Cu 6 Sn 6 cell, Fig. 13; a Li/Cu 6 Sn 5 cell; Fig. 14: a Li/Cu 6 Sn 4 cell; Fig. 15: a Li/Li 2 CuSn cell; Fig.
- Fig. 16 a collective plot of Li/Sn, Li/Cu 6 Sn 6 , Li/Cu 6 Sn 5 , Li/Cu 6 Sn 4 , Li/Cu 6 Sn 2 and Li/Li 2 CuSn cells;
- Fig. 17 a second collective plot of Li/Sn, Li/Cu ⁇ n*, Li/Cu 6 Sn 5 and Li/Cu 6 Sn 4 cells;
- Fig. 21 a Li/InSb cell;
- Fig. 22 a Li/InSb cell.
- Fig. 23, a Li/SnSb cell, Fig. 25, a Li/Cu 6 . x Zn x Sn 5 (x l) cell, and
- Table 1 Table 1
- Li,ZnSb Crystallographic Parameters for Li-,CuSn Space Group: F-43m; a 6.27 A Atom Wyckoff x Occupancy
- Intermetallic electrodes based on the Cu 6 Sn 5 and Li 2 CuSn structure types have been discovered to be useful negative electrodes for lithium-ion cells.
- the new anodes that operate substantially by a topotactic reaction mechanism may provide a significant improvement over the cycling capability of state-of-the-art binary lithium alloy electrodes. Cycling stability of these electrodes is however, gained at the expense of the capacity of the binary lithium alloy systems. While there has been disclosed what is considered to be the preferred embodiment of the present invention, it is understood that various changes in the details may be made without departing from the spirit, or sacrificing any of the advantages of the present invention.
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AU11180/00A AU1118000A (en) | 1998-12-21 | 1999-10-15 | Novel anodes for rechargeable lithium batteries |
US09/622,617 US6528208B1 (en) | 1998-07-09 | 1999-10-15 | Anodes for rechargeable lithium batteries |
CA002321130A CA2321130A1 (en) | 1998-12-21 | 1999-10-15 | Novel anodes for rechargeable lithium batteries |
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US14231298P | 1998-12-21 | 1998-12-21 | |
US60/142,312 | 1998-12-21 | ||
PCT/US1999/012868 WO2000003443A1 (en) | 1998-07-09 | 1999-06-08 | Novel anodes for rechargeable lithium batteries |
USPCT/US99/12868 | 1999-06-08 | ||
USPCT/US99/18811 | 1999-08-17 | ||
PCT/US1999/018811 WO2000038257A1 (en) | 1998-12-21 | 1999-08-17 | Novel anodes for rechargeable lithium batteries |
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Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
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EP1381099A1 (en) * | 2001-04-09 | 2004-01-14 | Sony Corporation | Negative electrode for non-aqueous electrolyte secondary cell and non-aqueous electrolyte secondary cell using the negative electrode |
CN111370671A (en) * | 2020-03-20 | 2020-07-03 | 东莞东阳光科研发有限公司 | Preparation method of lithium-sulfur battery positive electrode material |
Citations (3)
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US4851309A (en) * | 1983-03-07 | 1989-07-25 | Matsushita Electric Industrial Co., Ltd. | Rechargeable electrochemical apparatus and negative electrode thereof |
US5770333A (en) * | 1995-06-12 | 1998-06-23 | Hitachi, Ltd. | Nonaqueous secondary battery and negative electrode material therefor |
JPH1140155A (en) * | 1997-07-23 | 1999-02-12 | Matsushita Electric Ind Co Ltd | Negative electrode material for nonaqueous electrolyte secondary battery |
-
1999
- 1999-10-15 CA CA002321130A patent/CA2321130A1/en not_active Abandoned
- 1999-10-15 WO PCT/US1999/024168 patent/WO2000038258A1/en active Application Filing
- 1999-10-15 AU AU11180/00A patent/AU1118000A/en not_active Abandoned
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
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US4851309A (en) * | 1983-03-07 | 1989-07-25 | Matsushita Electric Industrial Co., Ltd. | Rechargeable electrochemical apparatus and negative electrode thereof |
US5770333A (en) * | 1995-06-12 | 1998-06-23 | Hitachi, Ltd. | Nonaqueous secondary battery and negative electrode material therefor |
JPH1140155A (en) * | 1997-07-23 | 1999-02-12 | Matsushita Electric Ind Co Ltd | Negative electrode material for nonaqueous electrolyte secondary battery |
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Title |
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THACKERAY M. M. ET AL.: "Stabilization of Insertion Electrodes for Lithium Batteries", JOURNAL OF POWER SOURCES, vol. 81-82, 1999, pages 60 - 66, XP002926172 * |
TIRADO J. L. ET AL.: "Electrochemical lithium insertion into In16Sn4S32 and Cu4In20S32 spinel sulphides", JOURNAL OF ALLOYS AND COMPOUNDS, vol. 217, no. 2, February 1995 (1995-02-01), pages 176 - 180, XP002926173 * |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP1381099A1 (en) * | 2001-04-09 | 2004-01-14 | Sony Corporation | Negative electrode for non-aqueous electrolyte secondary cell and non-aqueous electrolyte secondary cell using the negative electrode |
EP1381099A4 (en) * | 2001-04-09 | 2007-01-10 | Sony Corp | Negative electrode for non-aqueous electrolyte secondary cell and non-aqueous electrolyte secondary cell using the negative electrode |
CN111370671A (en) * | 2020-03-20 | 2020-07-03 | 东莞东阳光科研发有限公司 | Preparation method of lithium-sulfur battery positive electrode material |
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CA2321130A1 (en) | 2000-06-29 |
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