(12) United States Patent
`Thackeray et al.
`
`(10) Patent N0.:
`
`(45) Date of Patent:
`
`US 6,680,143 B2
`Jan. 20, 2004
`
`US006680143B2
`
`(54)
`
`(75)
`
`LITHIUM METAL OXIDE ELECTRODES
`FOR LITHIUM CELLS AND BATTERIES
`
`Inventors: Michael M. Thackeray, Naperville, IL
`(US); Christopher S. Johnson,
`Naperville, IL (US); Khalil Amine,
`Downers Grove, IL (US); Jaekook
`Kim, Naperville, IL (US)
`
`(73)
`
`Assignee: The University of Chicago, Chicago,
`IL (US)
`
`(*)
`
`Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 134 days.
`
`Appl. No.: 09/989,844
`
`Filed:
`
`Nov. 21, 2001
`Prior Publication Data
`
`US 2002/0114995 A1 Aug. 22, 2002
`
`Related U.S. Application Data
`
`Continuation—in—part of application No. 09/887,842, filed on
`Jun. 21, 2001.
`Provisional application No. 60/213,618, filed on Jun. 22,
`2000.
`
`Int. Cl.7 ............................................... .. H01M 4/50
`
`FOREIGN PATENT DOCUMENTS
`
`WO
`
`WO 00/23380
`
`4/2000
`
`OTHER PUBLICATIONS
`
`Material Res. Bulletin vol. 15, pp. 783-789, 1980, “A New
`Cathode Material for Batteries of High Energy Density”, K.
`Mizushima et al.
`
`Electrochemical Society vol. 144, No. 8, Aug. 1997, Mor-
`phology Effects on The Electrochemical Performance
`of .
`.
`.
`, W. Li et al, pp. 2773-2779.
`. 117-119 (1998)
`.
`Electrochemical and Solid State .
`Novel
`.
`.
`. Compounds as Cathode Material for Safer
`Lithium-Ion Batteries, Yuan Gao et al.
`Journal of Power Sources 90 (2000) 76-81, “Lithium Nick-
`elate Electrodes With Enhanced .
`.
`. Thermal Stability,”
`Hajime Arai et al.
`Electrochemical Society vol. 144, Sep. 9, 1997, Electro-
`chemical and Thermal Behavior of .
`.
`.
`, Hajime Arai et al.,
`pp. 3117-3125.
`.
`.
`Nature, vol. 381, Jun. 6, 1996, Synthesis of Layered .
`Lithium Batteries, A. Robert Armstrong et al., pp. 499-500.
`Mat. Res. Bull. vol. 26, pp. 463-473, 1991, Lithium Man-
`ganese Oxides From .
`.
`. Battery Applications, M.H. Ros-
`souw et al.
`
`(List continued on next page.)
`
`Primary Examiner—Laura Weiner
`(74) Attorney, Agent, or Firm—Emrich and Dithmar
`
`(21)
`
`(22)
`
`(65)
`
`(63)
`
`(60)
`
`(51)
`
`(52)
`
`(58)
`
`(56)
`
`U.s. Cl.
`
`............... .. 429/224, 429/231.1, 429/231.3,
`429/223, 429/231.5; 429/231.6; 423/599
`
`(57)
`
`ABSTRACT
`
`Field of Search ............................ .. 429/224, 231.1,
`429/231.3, 223, 231.5, 231.6; 423/599
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`5,153,081 A
`5,370,949 A
`5,393,622 A
`6,017,654 A
`6,221,531 B1
`6,551,743 B1
`
`10/1992
`12/1994
`2/1995
`1/2000
`4/2001
`4/2003
`
`Thackeray et al.
`Davidson et al.
`Nitta et al.
`Kumta et al.
`Vaughey et al.
`Naka
`nishi
`
`A lithium metal oxide positive electrode for a non-aqueous
`lithium cell is disclosed. The cell is prepared in its initial
`discharged state and has a general formula xLiMO2.(1—x)
`Li2M‘O3 in which 0<x<1, and where M is one or more ion
`with an average trivalent oxidation state and with at least one
`ion being Mn or Ni, and where M‘ is one or more ion with
`an average tetravalent oxidation state. Complete cells or
`batteries are disclosed with anode, cathode and electrolyte as
`are batteries of several cells connected in parallel or series
`or both.
`
`18 Claims, 14 Drawing Sheets
`
` xLi2M’O3o(1-x-y)LiMO2
`
`Path of initial
`electrochemical
`delithiation
`
`Li2M'O3
`
`xLi2M’O3-(1-x)LiMO2
`
`(M’= e.g., Mn, Ti, Zr)
`
`(M: e.g., Mn, Ni)
`
`Page 1 of 23
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`SONY EXHIBIT 1001
`
`SONY EXHIBIT 1001
`
`Page 1 of 23
`
`

`
`US 6,680,143 B2
`Page 2
`
`OTHER PUBLICATIONS
`
`Journal of Solid State Chemistry, 104, 464-466 (1993),
`Synthesis and Structural Characterization .
`.
`. Lithiated
`Derivative .
`.
`.
`, M.H. Rossouw et al.
`The Electrochemical Society, Inc. Meeting Abstract No. 16,
`Boston, Nov. 1-6, 1998, Layered Lithium-Manganese
`Oxide .
`.
`. Precursors, Christopher S. Johnson et al.
`Journal of Power Sources 81-82 (1999) 491-495, “Struc-
`tural and Electrochemical Analysis .
`.
`. ”, C. S. Johnson et
`al.
`
`10th International Meeting on Lithium Batteries, “Lithium
`2000”, Como, Italy, May 28-Jun. 2, 2000, Abstract No. 17,
`B. Amundsen et al.
`
`Solid State Ionics 118 (1999) 117-120, Preparation and
`Electrochemical Properties .
`.
`.
`, K. Numata et al.
`Solid State Ionics, vol. 57m, p. 311 (1992), R. Rossen et al.
`Power Sources, vol. 74, p. 46 (1998), M. Yoshio et al.
`J. Electrochem. Soc., vol. 145, p. 1113 (1998) Yuoshio M. et
`al.
`
`Chem. Commun. vol. 17, p. 1833 (1998); Armstrong A. R.
`et al.
`
`J. Mat. Chem., vol. 9, p. 193 1999); P. G. Bruce et al.
`
`J. Solid State Chem., vol. 145, p. 549 (1999). Armstrong, A.
`R.
`
`J. Power Source, vol. 54, p. 205 (1995); Davidson, I. J. et al.
`
`ZhonghuaLu, D.D. MacNeil and J .R. Dahn, Layered-Cath-
`ode Materials .
`.
`. For Lithium-Ion Batteries, Electrochemi-
`cal and Solid State letters, 4 (11) A191-A194 (2001).
`
`T. Ohzuku and Y. Makimura, Layered Lithium Insertion
`Material .
`.
`. For Lithium-Ion Batteries, Dept. of Applied
`Chemistry, Graduate School of Eng., Osaka City Univ.
`Osaka 558-8585, Chemistry Express, p. 642 (2001).
`
`I.J. Davidson, R.S. McMillan, J.J. Murray, Rechargeable
`Cathodes Based .
`.
`.
`, Journal of Power Sources 54 (1995)
`205-208.
`
`Page 2 of 23
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`Page 2 of 23
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`Jan. 20, 2004
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`US 6,680,143 B2
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`U.S. Patent
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`

`
`US 6,680,143 B2
`
`1
`LITHIUM METAL OXIDE ELECTRODES
`FOR LITHIUM CELLS AND BATTERIES
`
`RELATED APPLICATIONS
`
`This continuation-in-part application of U.S. patent appli-
`cation Ser. No. 09/887,842 filed Jun. 21, 2001 which
`claimed priority under 35 U.S.C. §1.78(a)(3) of provisional
`application Serial No. 60/213,618 filed Jun. 22, 2000. +gi
`The United States Government has rights in this invention
`pursuant to Contract No. W-31-109-ENG-38 between the
`U.S. Department of Energy (DOE) and The University of
`Chicago representing Argonne National Laboratory.
`
`BACKGROUND OF THE INVENTION
`
`This invention relates to lithium metal oxide positive
`electrodes for non-aqueous lithium cells and batteries. More
`specifically, it relates to lithium-metal-oxide electrode com-
`positions and structures, having in their initial state in an
`electrochemical cell, a general formula xLiMO2.(1—x)
`Li2M‘O3 alternatively Li2_xMxM‘1_xO3_x in which 0<x<1
`and where M is one or more ion with an average oxidation
`state of three and with at least one ion being Mn, and where
`M‘ is one or more ions with an average oxidation state of
`four selected preferably from Mn, Ti and Zr; or, where M is
`one or more ion with an average oxidation state of three and
`with at least one ion being Ni, and where M‘ is one or more
`ions with an average oxidation state of four with at least one
`ion being Mn. In one embodiment of the invention, the Mn
`content should be as high as possible, such that the LiMO2
`component is essentially LiMnO2 modified in accordance
`with this invention.
`In a second embodiment of the
`
`10
`
`15
`
`20
`
`25
`
`30
`
`invention, the Ni content should be as high as possible such
`that the LiMO2 component is essentially LiNiO2 modified in
`accordance with this invention. In a further embodiment of
`
`35
`
`the invention, the transition metal ions and lithium ions may
`be partially replaced by minor concentrations of one or more
`mono- or multivalent cations such as H’' derived from the
`
`electrolyte by ion-exchange with Li’' ions, and/or Mg“ and
`Al3+ to impart improved structural stability or electronic
`conductivity to the electrode during electrochemical cycling.
`Prior application Ser. No. 09/887/842 filed Jun. 21, 2001
`taught one or more cations M or M‘ in a lithium metal oxide
`cathode, such as LiMO2 or Li2M‘O3 where M has an
`oxidation state or valence of three and M‘ has an oxidation
`
`state or valence of four. Although one of ordinary skill in the
`art would have clearly understood that
`the valences or
`oxidation states taught included ions which averaged oxi-
`dation state of three or average oxidation states of four, this
`continuation-in part application explictily states what was
`understood from the earlier filed ’842 application and adds
`newly obtained data.
`
`SUMMARY OF THE INVENTION
`
`Lithium-metal oxide compounds of general formula
`LiMO2, where M is a trivalent transition metal cation such
`as Co, Ni, Mn, Ti, V, Fully executed, with a trivalent
`oxidation state and with electrochemically inactive substitu-
`ents such as Al are very well known and are of interest as
`positive electrodes for rechargeable lithium batteries. The
`best-known electrode material
`is LiCoO2, which has a
`layered-type structure and is relatively expensive compared
`to the isostructural nickel and manganese-based compounds.
`Efforts are therefore being made to develop less costly
`electrodes, for example, by partially substituting the cobalt
`ions within LiCoO2 by nickel, such as in LiNi0_8CoO_2O2 or
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`2
`by exploiting the manganese-based system LiMnO2. Such
`layered compounds are sometimes stabilized by partially
`replacing the transition metal cations within the layers by
`other metal cations, either alone or in combination. For
`example, Li+ and/or Mg“ ions may be introduced into the
`structure to improve the electronic conductivity of the
`electrode, or Al3+ and/or Ti“ ions to improve the structural
`stability of the electrode at high levels of delithiation.
`Examples of such compounds are LiNiO_8Co0_15AlO_O5O2 and
`I-iNio.7sC0Oo.1sTio.osMgo.osO2~
`A major problem of layered LiMO2 compounds contain-
`ing either Co or Ni (or both) is that the transition metal
`cations, M, with a trivalent oxidation state are oxidized
`during charge of the cells to a metastable tetravalent oxida-
`tion state. Such compounds are highly oxidizing materials
`and can react with the electrolyte or release oxygen. These
`electrode materials can,
`therefore, suffer from structural
`instability in charged cells when, for example, more than
`50% of the lithium is extracted from their structures; they
`require stabilization to combat such chemical degradation.
`Although the layered manganese compound LiMnO2 has
`been successfully synthesized in the laboratory, it has been
`found that delithiation of the structure and subsequent
`cycling of the LixMnO2 electrode in electrochemical cells
`causes a transition from the layered MnO2 configuration to
`the configuration of a spinel-type [Mn2]O4 structure. This
`transformation changes the voltage profile of the
`Li/LixMnO2 cell such that it delivers capacity over both a 4V
`and a 3V plateau; cycling over the 3V plateau is not fully
`reversible which leads to capacity fade of the cell over
`long-term cycling. Other types of LiMnO2 structures exist,
`such as the orthorhombic-form, designated O—LiMnO2 in
`which sheets of MnO6 octahedra are staggered in zig—zig
`fashion unlike their arrangement
`in layered LiMnO2.
`However, O—LiMnO2 behaves in a similar way to layered
`LiMnO2 in lithium cells;
`it also converts to a spinel-like
`structure on electrochemical cycling.
`Therefore, further improvements must be made to LiMO2
`electrodes, particularly LiMnO2 and LiNiO2,
`to impart
`greater structural stability to these electrode materials during
`electrochemical cycling in lithium cells and batteries. This
`invention addresses the stability of LiMO2 electrode
`structures, particularly those in which M is Mn and Ni, and
`makes use of a Li2M‘O3 component in which M‘ is one or
`more ions with an average oxidation state of four to improve
`their stability.
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The invention consists of certain novel features and a
`
`combination of parts hereinafter fully described, illustrated
`in the accompanying drawings, and particularly pointed out
`in the appended claims, it being 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.
`
`FIG. 1 depicts a schematic representation of a Li2M‘O3—
`MO2—LiMO2 phase diagram, in which M (in the LiMO2
`component) is one or more ions with an average oxidation
`state of three, and in which M‘ (in the Li2M‘O3 component)
`is one or more ions with an average oxidation state of four;
`FIG. 2 depicts the X-ray diffraction pattern of a
`xLi2MnO3.(1—x)LiNi0_8Co0_2O2 electrode composition;
`FIG. 3 depicts the X-ray diffraction pattern of a xLi2Mn1_
`xTIxO3.(1—X)LINIO_8C0O_2O2 electrode composition;
`FIG. 4 depicts the X-ray diffraction pattern of a xLi2TiO3.
`(1—x)LiMnO2 electrode composition;
`
`Page 17 of 23
`
`Page 17 of 23
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`

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`US 6,680,143 B2
`
`3
`FIG. 5 depicts the X-ray diffraction pattern of a
`Li1_2NiO_4MnO_4O2 electrode component composition;
`FIG. 6 depicts the X-ray diffraction pattern of a
`Li1_9Mn0_9Ni0_2O3 electrode component composition;
`FIG. 7 depicts the electrochemical profile of a
`Li/xLi2MnO3.(1—x)LiNiO_8Co0_2O2 electrochemical cell;
`FIG. 8 depicts the electrochemical profile of a
`Li/xLi2TiO3.(1—x)LiMnO2 electrochemical cell;
`FIG. 9 depicts the X-ray diffraction pattern of a xLi2TiO3.
`(1—x)LiNiO_5Mn0_5O2 electrode composition;
`FIG. 10 depicts the cyclic voltammogram of a xLi2TiO3.
`(1—x)LiNiO_5Mn0_5O2 electrode;
`FIG. 11 depicts the electrochemical charge/discharge pro-
`files of a Li/xLi2TiO3.(1—x)LiNi0_5MnO_5O2 electrochemical
`cell;
`FIG. 12 depicts the capacity versus cycle number plot of
`a Li/xLi2TiO3.(1—x)LiNiO_5MnO_5O2 electrochemical cell;
`FIG. 13 depicts a schematic representation of an electro-
`chemical cell; and
`FIG. 14 depicts a schematic representation of a battery
`consisting of a plurality of cells connected electrically in
`series and in parallel.
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`
`This invention relates to stabilized LiMO2 electrodes
`whereby an electrochemically inert rocksalt phase Li2MO3
`is introduced as a component to the overall electrode struc-
`ture as defined, in its initial state, by the general formula
`xLiMO2.(1—x)Li2M‘O3 alternatively Li2_xMxM‘1_xO3_x in
`which 0<x<1, preferably 0.8<x<1, and more preferably
`0.9<x<1, and where M is one or more ion with an average
`oxidation state of three and having at least one ion selected
`from Mn and where M‘ is one or more ions with an average
`oxidation state of four selected preferably from Mn, Ti and
`Zr, or alternatively, where M is one or more ion with an
`average oxidation state of three and having at least one ion
`selected from Ni and where M‘ is one or preferably more
`ions with an average oxidation state of four having at least
`one ion selected from Mn. These compounds can be visu-
`alized as lying on the LiMO2—Li2M‘O3 tie-line of the
`Li2M'O3—MO2—LiMO2 phase diagram shown schemati-
`cally in FIG. 1.
`From a consideration of charge balance, because lithium
`and oxygen ions are monovalent (+1) and divalent (-2),
`respectively, it necessitates that when the M cations are of
`one type such as in LiMnO2, LiCoO2 and LiNiO2,
`the
`oxidation state of the M cations must be trivalent. However,
`it stands to reason that when two or more M cations reside
`
`in the LiMO2 structure, the oxidation state of the M cations
`may either be all trivalent, or they may be of mixed valence
`such that the average oxidation state of the M cations overall
`is three or trivalent. Examples of the latter case would, in
`principle, be 1) Li(Mn0_5Ni0_5)O2 if the oxidation state of the
`Mn ions is tetravalent and the oxidation state of the Ni ions
`
`is divalent, as is the case for the lithium-manganese-nickel-
`oxide spinel Li[Mn0_5NiO_5]O4; 2) Li(MnO_4NiO_4AlO_2)O2 if
`the oxidation state of the Mn ions is four or tetravalent, the
`oxidation state of the Ni ions is divalent, and the oxidation
`state of the Al ions is trivalent; 3) Li(Mn0_4NiO_4Li0_2)O2, if
`the Mn ions are tetravalent, the Ni ions are trivalent and the
`Li ions are monovalent; and 4) Li(MnO_5NiO_4LiO_1)O2 if the
`Mn ions are tetravalent, the Li ions are monovalent, and if
`0.1 Ni ions are trivalent and 0.3 Ni ions are divalent.
`
`The rocksalt phase Li2MnO3 has a layered-type structure
`in which discrete layers of lithium ions alternate with layers
`
`4
`
`containing Mn and Li ions (in a 2:1 ratio) between the
`close-packed oxygen sheets. Note that, in this respect, the
`formula Li2MnO3 can be written in layered notation as
`Li(Mn2/3Li1/3)O2, in which the Li and Mn within round
`brackets represent
`the ions in one layer. A difference
`between Li2MnO3 and the layered LiMO2 compounds is that
`the Mn ions in Li2MnO3 are tetravalent and cannot be easily
`electrochemically oxidized by lithium extraction, whereas in
`the LiMO2 compounds the transition metal cations M are
`trivalent and can be electrochemically oxidized. Because
`Li2MnO3 has a rocksalt phase,
`there is no energetically
`favorable interstitial space for additional lithium; therefore,
`Li2MnO3 cannot operate as an insertion electrode and can-
`not be electrochemically reduced. The xLiMO2.(1—x)
`Li2M‘O3 structure may be either a solid solution of the two
`components or a domain structure with a common oxygen
`array for both the LiMO2 and Li2MnO3 components, but in
`which the cation distribution can vary such that domains of
`the two components exist side by side. Such a solid solution
`or domain structure does not rule out the possibility of cation
`mixing and structural disorder, particularly at domain or
`grain boundaries. In a generalized xLiMO2.(1—x)Li2M‘O3
`layered structure, one layer contains M, M‘ and Li ions
`between sheets of close-packed oxygen ions, whereas the
`alternate layers are occupied essentially by lithium ions
`alone. By analogy, in a xLiMO2.(1—x)Li2M‘O3 structure that
`contains monoclinic LiMnO2 as the LiMO2 component, it is
`believed that the tetravalent M‘ ions can partially occupy the
`M positions in the monoclinic layered LiMnO2 structure,
`thereby providing increased stability to the overall structure.
`In a further embodiment of the invention, from the
`foregoing arguments, it stands to reason that the lithium and
`the tetravalent M‘ ions in the Li2M‘O3 component of the
`xLiMO2.(1—x)Li2M‘O3 structure can be partially replaced
`by other monovalent or tetravalent cations. Of particular
`significance to the invention is the replacement of Mn in an
`Li2Mn2O3 component by Ti or Zr which are known to form
`isostructural compounds Li2TiO3 and Li2ZrO3, respectively;
`such components are expected to enhance the structural
`stability of the xLiMO2.(1—x)Li2M‘O3 electrode.
`Furthermore, it stands to reason that the lithium and M‘ ions
`in the Li2M‘O3 component of the xLiMO2.(1—x)Li2M‘O3
`structure can be partially replaced by other monovalent, or
`multivalent ions, such that the substitution maintains charge
`neutrality, thereby introducing electrochemical activity to
`the Li2M‘O3 component and giving it LiMO2-type charac-
`teristics; in principle, examples of such components are 1)
`Li1_8MnO_9Ni0_3O3, written alternatively in LiMO2 form as
`Li(Mno0_6NiO_2Li0_2)O2,
`in which the lithium ions are
`monovalent,
`the manganese ions are tetravalent, and the
`nickel ions are divalent which can be electrochemically
`oxidized to the tetravalent state in a lithium cell; and 2)
`Li1_9MnO_9Ni0_2O3, written alternatively in LiMO2 form as
`Li(MnO_6ONiO_13LiO_27)O2,
`in which the lithium ions are
`monovalent,
`the manganese ions are tetravalent, and the
`nickel ions are 50% divalent and 50% trivalent, all of which
`can be electrochemically oxidized to the tetravalent state in
`a lithium cell.
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`In the electrodes of the present invention, the M and M‘
`ions can be disordered in the electrode structure.
`It
`is
`
`preferable that the Mn content should be as high as possible,
`such that the LiMO2 component is essentially LiMnO2. In a
`further embodiment of the invention, the Ni content should
`be as high as possible such that the LiMO2 component is
`essentially LiNiO2 modified in accordance with the inven-
`tion. In yet a further embodiment of the invention,
`the
`transition metal
`ions and lithium ions may be partially
`
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`US 6,680,143 B2
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`replaced by minor concentrations (typically less than 10
`atom percent) of other mono- or multivalent cations such as
`Li+, Mg2+ or Al3+ to impart improved structural stability or
`electronic conductivity to the electrode during electrochemi-
`cal cycling. In addition, the xLiMO2.(1—x)Li2M‘O3 struc-
`tures of the invention may include H+ ions, for example,
`resulting from the removal acidic H+ species from the
`electrolyte by ion-exchange with Li’'
`ions.
`It stands to
`reason, therefore, that the present invention includes the
`introduction of mono- or divalent cations into the structure,
`and that the electrodes of the invention may therefore depart
`slightly from the ideal stoichiometry as defined by the
`formula xLiMO2.(1—x)Li2M‘O3.
`It has been shown in the past that Li2MnO3 (and isos-
`tructural Li2Mn1_xZrxO3) which is electrochemically
`inactive, can be used as a precursor material to form an
`electrochemically active charged xMnO2.(1—x)Li2MnO3
`electrode structure in which X is approximately equal to
`0.91;
`this value of X translates to a composition of the
`layered structure Li1_1MnO_9O2. These charged xMnO2.(1—
`x)Li2MnO3 compounds have been prepared by leaching
`Li2O from the Li2MnO3(Li2O.MnO2) structure with acid
`such as sulphuric acid (U.S. Pat. No. 5,153,081). However,
`the acid treatment causes a shear of the oxygen array, such
`that the resulting xMnO2.(1—x)Li2MnO3 structures are no
`longer close-packed but have an oxygen arrangement that
`provides octahedral and trigonal prismatic sites in alternate
`layers. During relithiation,
`for example with Lil
`in
`acetonitrile, it has been demonstrated that the oxygen sheets
`shear back to close-packing and that the phase transforma-
`tion yields a xLiMnO2.(1—x)Li2MnO3-type structure.
`However, such phase transformations are undesirable in
`rechargeable battery systems, because they can adversely
`affect
`the efficiency and rechargeability of the electrode.
`Thus, a major advantage of this invention is that this phase
`transformation can be avoided by starting directly with a
`discharged xLiMnO2.(1—x)Li2MnO3 electrode in the cell
`because the non-aqueous removal of lithium does not appear
`to cause the phase transition to yield the structure (non
`close-packed) generated by acid leaching of Li2MnO3.
`Furthermore, it is important to note that even though the
`relithiation of a xMnO2.(1—x)Li2MnO3 electrode of the prior
`art in an electrochemical cell yields the same formulation as
`the electrodes of the present invention, i.e., xLiMnO2.(1—x)
`Li2MnO3, the applicants believe that the structures of the
`electrode materials of the present invention are significantly
`different from those of the prior art and will be unequivo-
`cally distinguished from one another by high-resolution
`transmission electron microscopy, i.e., differences will be
`evident in the microstructural features of the xLiMnO2.(1—
`x)Li2MnO3 electrodes of the present invention and those of
`the prior art. For example, because the lithiated xLiMnO2.
`(1—x)Li2MnO3 electrode structures of the prior art are
`derived from a non-close-packed xMnO2.(1—x)Li2MnO3
`structure, which is obtained by the acid leaching of, and
`Li2O removal from, a Li2MnO3 precursor as described
`above, the microstructures of the prior art electrode mate-
`rials will be characterized by high concentrations of defects
`and stacking faults, as is evident by the broad peaks in their
`X-ray diffraction patterns, in contrast to the electrode mate-
`rials of the present invention that are more crystalline and
`ordered as reflected by the relatively sharp and well-resolved
`peaks in their X-ray diffraction patterns (FIGS. 2, 3 and 4).
`Another disadvantage of the acid-treated compounds of
`the prior art (’081 patent) xMnO2.(1—x)Li2MnO3, is that
`they represent charged positive electrodes, whereas lithium-
`ion batteries require positive electrodes in the discharged
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`state, for example, LiMO2 electrodes (M=Co, Ni, Mn).
`Moreover, the charged xMnO2.(1—x)Li2MnO3 electrodes of
`the prior art require dehydration before use so that they can
`be used effectively in lithium cells. By contrast,
`the
`xLiMnO2.(1—x)Li2MnO3 electrodes of this invention are
`prepared in the discharged state and are essentially anhy-
`drous materials and are more stable to heat-treatment and
`
`long-term storage in air compared to the xMnO2.(1—x)
`Li2MnO3 materials of the prior art, which are known to
`transform on storage to a gamma-MnO2-type structure as
`reported by Johnson et al in J. Power Sources 81-82, 491
`(1999).
`this invention extends to include
`In one embodiment,
`xLiMO2.(1—x)Li2M‘O3 electrodes stabilized by isostructural
`rocksalt Li2M‘O3 compounds other than M'=Mn, Ti, Zr as
`described in the preceding sections. Examples of such
`compounds are Li2RuO3, Li2ReO3, Li2IrO3, and Li2PtO3
`which may contribute a portion of the electrochemical
`capacity of the electrode.
`One of the difficulties that has been encountered in
`
`synthesizing xLiMO2.(1—x)Li2M‘O3 electrodes, in which M
`is Mn, has been to keep the valency of the manganese ions
`equal, or close to its trivalent state. This has been success-
`fully accomplished by the inventors with a hydrothermal
`method or process under basic conditions using LiOH and/or
`KOH. This invention, therefore, extends to include a hydro-
`thermal process or method for synthesizing xLiMO2.(1—x)
`Li2M‘O3 compounds in which M is one or more trivalent ion
`with at least one ion being Mn, and in which M‘
`is a
`tetravalent ion. Such methods of synthesis are undertaken in
`a pressurized autoclave, preferably between 5 and 35 atmo-
`spheres and at temperatures ranging between 100 and 250°
`C. and most preferably at 10-20 atm and temperatures
`between 180 and 230° C. for about 6 to 12 hours or more if
`
`necessary. For example, 0.15LiMnO2.85Li2TiO3 electrodes
`have been successfully prepared by this process from pre-
`cursor materials consisting of manganese oxide (Mn2O3),
`lithium hydroxide (LiOH.H2O) and titanium isopropoxide
`(Ti[OCH(CH3)2]4) in a potassium hydroxide (KOH) solu-
`tion at 220° C. and at 15 atmospheres pressure.
`It has been recently demonstrated that layered lithium-
`chromium-manganese-oxide and lithium-cob alt-
`manganese-oxide electrodes of general formula xLiCrO2.
`(1—x)Li2MnO3 and xLiCoO2.(1—x)Li2MnO3 provide
`electrochemical stability when cycled between 4.5 and 2.0 V
`in electrochemical
`lithium cells.
`In particular,
`a
`Li(CrO_4Mn0_4Li0_2)O2 electrode (alternatively,
`0.4LiCrO2.0.4Li2MnO3) delivers approximately 150 mAh/g
`at 25° C. and 200 mAh/g at 55° C. at an average cell voltage
`of 3.5 V vs. Li. However, because the Li2MnO3 component
`is electrochemically inactive, the electrochemical capacity
`derived from the cell is due to the oxidation of Cr3+ to Cr°+
`during the electrochemical charging of the cells. This system
`has an immediate disadvantage because it is known that the
`high oxidation states of chromium such as those found in
`Cr3O8 are dangerous and are a major health hazard whereas
`the electrodes of the present invention operate predomi-
`nantly off a M3+/M4+ couple, notably a Mn3+/4+ couple. For
`the cobalt compound, xLiCoO2.(1—x)Li2MnO3, no signifi-
`cant advantage is gained in overcoming the cost limitations
`of the electrode because the cobalt ions, not the manganese
`ions, provide all the electrochemical capacity of the elec-
`trode.
`
`The following examples of stabilized xLiMnO2.(1—x)
`Li2MnO3 electrodes and LiMO2 and Li2M‘O3 components
`containing either manganese and/or nickel describe the
`principles of the invention as contemplated by the inventors,
`but they are not to be construed as limiting examples.
`
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`US 6,680,143 B2
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`7
`EXAMPLE 1
`
`The electrode material 0.2Li2MnO3.0.8LiNiO_8CoO_2O2
`that
`can
`be written,
`alternatively,
`as
`Li(Ni0_58MnO_18CoO_15LiO_09)O2 was prepared by the reac-
`tion of Ni(NO3)2, Co(NO3)2, MnO2, and LiOH in the
`required stoichiometric amounts at 800° C. in air or oxygen
`for about 16 hours. The powder X-ray diffraction pattern of
`this compound indicates an essentially single-phase product
`with a layered-type structure (FIG. 2).
`
`EXAMPLE 2
`
`0.2Li2Mn1_
`electrode material
`The
`XTIXO3.0.8LINI0_8C00_2O2, where x=0.5, which can be
`written, alternatively, as Li(Ni0_58Mn0_09TiO_O9CoO_15Li0_09)
`O2 was prepared by the reaction of Ni(NO3)2, Co(NO3)2,
`MnO2, TiO2 (anatase) and LiOH in the required stoichio-
`metric amounts at 800° C. in air or oxygen for about 16
`hours. The powder X-ray diffraction pattern of this com-
`pound indicates an essentially single-phase product with a
`layered-type structure (FIG. 3).
`
`EXAMPLE 3
`
`The electrode material 0.15Li2TiO3.0.85LiMnO2 that can
`be written, alternatively, as Li(Ti0_14Mn0_79LiO_07)O2 was
`prepared by the hydrothermal reaction of Mn2O3, TiO2
`(anatase and LiOH in the required stoichiometric amounts at
`220° C. and 15 atmospheres pressure for about 10 hours. The
`powder X-ray diffraction pattern of this compound indicates
`an essentially single-phase product with a layered-type
`structure (FIG. 4).
`
`EXAMPLE 4
`
`The electrode component material Li1_2Mn0_4NiO_4O2 that
`can be written, alternatively,
`in LiMO2 form as
`Li(Mn0_4Ni0_4LiO_2)O2 in which the Mn ions are tetravalent,
`the Ni ions are trivalent and the Li ions are monovalent was
`
`prepared by the reaction of Mn0_5Ni0_5(OH)2, and
`LiOH.H2O in the required stoichiometric amounts in pel-
`letized form, first at 480° C. for 12 hours and thereafter at
`950° C. for 10 hours. The sample was then quenched in air
`to room temperature and ground into a powder. The powder
`X-ray diffraction pattern of this compound, in which the
`average oxidation state of all the M ions (MnO_4NiO_4LiO_2) is
`trivalent, indicates an essentially single-phase product with
`a layered-type structure (FIG. 5).
`EXAMPLE 5
`
`The electrode component material Li1_9Mn0_9Ni0_2O3 that
`can be written, alternatively,
`in LiMO2 form as
`Li(Mn0_60NiO_13LiO_27)O2 in which the Li
`ions are
`monovalent, the Mn ions are tetravalent, and the Ni ions are
`50% divalent and 50% trivalent, was prepared by the reac-
`tion of MnOOH, Ni(OH)2, and LiOH.H2O in the required
`stoichiometric amounts in pelletized form, first at 480° C.
`for 12 hours and thereafter at 950° C. for 10 hours. The
`sample was then quenched in air to room temperature and
`ground into a powder. The powder X-ray diffraction pattern
`of this compound in which the average oxidation state of all
`the M ions (Mn0_60Ni0_13Li0_27)
`is trivalent,
`indicates an
`essentially single-phase product with a layered-type struc-
`ture (FIG. 6).
`
`EXAMPLE 6
`
`The xLiMO2.(1—x)Li2M‘O3 electrode materials in
`Examples 1, 2 and 3 were evaluated in coin cell