(12) United States Patent
`Thackeray et al.
`
`111111
`
`1111111111111111111111111111111111111111111111111111111111111
`US006677082B2
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 6,677,082 B2
`Jan.13,2004
`
`(54) LITHIUM METAL OXIDE ELECTRODES
`FOR LITHIUM CELLS AND BATTERIES
`
`(75)
`
`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 120 days.
`
`(21) Appl. No.: 09/887,842
`
`(22) Filed:
`
`Jun.21,2001
`
`(65)
`
`Prior Publication Data
`
`US 2002/0136954 A1 Sep. 26, 2002
`
`Related U.S. Application Data
`( 60) Provisional application No. 60/213,618, filed on Jun. 22,
`2000.
`
`(51)
`
`Int. Cl? ................................................. HOlM 4/50
`
`wo
`
`FOREIGN PATENT DOCUMENTS
`wo 00/23380
`* 4/2000
`OTHER PUBLICATIONS
`
`Material Res. Bulletin vol. 15, pp. 783-789, 1980, "ANew
`Cathode Material for Batteries of High Energy Density", K.
`Mizushima et al.
`Electrochemical Society vol. 144, No. 8, Aug. 1997, Mor(cid:173)
`phology Effects on The Electrochemical Performance
`of ... , W. Li et al., pp. 2773-2779.
`Electrochemical
`and Solid State
`117-119
`(1998) Novel ... Compounds as Cathode Material for Safer
`Lithium-Ion Batteries, Yuan Gao et al.
`Journal of Power Sources 90 (2000) 76-81, "Lithium Nick(cid:173)
`elate Electrodes With Enhanced . . . Thermal Stability,"
`Hajime Arai et al.
`Electrochemical Society vol. 144, Sep., 9, 1997, Electro(cid:173)
`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(cid:173)
`ganese Oxides From ... Battery Applications, M.H. Ros(cid:173)
`souw et al.
`Journal of Solid State Chemistry, 104, 464-466 (1993),
`Synthesis and Structural Characterization . . . Lithiated
`Derivative ... , M.H. Rossouw et al.
`
`(52) U.S. Cl. .................... 429/224; 429/223; 429/231.1;
`429/231.6; 429/231.3; 423/599
`
`(58) Field of Search .............................. 429/231.1, 223,
`429/224, 218.1, 231.6, 231.3; 423/599
`
`(List continued on next page.)
`Primary Examiner-Laura Weiner
`(74) Attorney, Agent, or Firm---Emrich and Dithmar
`
`(57)
`
`ABSTRACT
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`5,153,081 A
`5,393,622 A
`6,017,654 A *
`6,221,531 B1
`6,551,743 B1 *
`2002/0136954 A1
`2003/0022063 A1
`2003/0027048 A1
`
`10/1992
`2/1995
`1!2000
`4/2001
`4/2003
`9/2002
`1!2003
`2/2003
`
`Thackeray et a!.
`Nitta eta!.
`Kumta et a!. .......... 429/231.95
`Vaughey et a!.
`Nakanishi eta!. .......... 429/223
`Thackeray et a!.
`Paulsen et a!.
`Lu eta!.
`
`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 xLiM0 2 .(1-x)
`Li2 M'0 3 in which O<x<l, and where M is one or more
`trivalent ion with at least one ion being Mn or Ni, and where
`M' is one or more tetravalent ion. Complete cells or batteries
`are disclosed with anode, cathode and electrolyte as are
`batteries of several cells connected in parallel or series or
`both.
`
`16 Claims, 8 Drawing Sheets
`
`M02
`xli2M'03•(1-x-y)LiM02
`
`Path of initial
`electrochemical
`delithiation
`
`/
`. /
`
`' ' ' ' ' ' ' '
`
`~
`'
`yli\
`'
`
`' '
`
`/
`xli2M'03•(1-x)LiM02
`
`(M'= e.g., Mn, Ti, Zr)
`
`(M= e.g., Mn, Ni)
`
`SONY EXHIBIT 1012
`
`Page 1 of 17
`
`

`
`US 6,677,082 B2
`Page 2
`
`01HER PUBLICATIONS
`
`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(cid:173)
`tural and Electrochemical Analysis ... ",C. S. Johnson et
`al.
`lOth 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.
`Chern. Commun. vol. 17, p. 1833 (1998); Armstrong A R.
`et al.
`J. Mat. Chern., vol. 9, p. 193 1999); P. G. Bruce et al.
`J. Solid State Chern., vol. 145, p. 549 (1999). Armstrong, A
`R.
`J. Power Source, vol. 54, p. 205 (1995); Davidson, I. J. et al.
`K. Mizushima, P.J. Wiseman and J.B. Goodenough, Mat.
`Res. Bull, 15 783-789 (1980).
`
`W. Li and J.C. Currie, J. Electrochem. Soc., 144,2773-2779
`(1997.
`Y. Gao, M.V. Yakovleva and W.B. Ebner, Electrochem. and
`Solid-State Lett., 1, 117-119 (1998).
`H. Arai, M. Tsuda andY. Sakurai, J. Power Sources, 90,
`76-81 (2000).
`H. Arai, S. Okada, Y. Sakurai and J. Yamaki,. Electrochem.
`soc., 144, 3117-3125 (1997).
`Armstrong and P.G. Bruce, Nature, 381, 499-500 (1996).
`M.H. Rossouw and M. M. Thackeray, J.Solid State Chern.
`104, 464-473 1993).
`M.H. Rossouw, D.C. Liles and M.M. Thakeray, J. Solid
`State Chern. 104, 464--466 (1993).
`C.S. Johnson, J.T. Vaughey, M.M. Thackeray, T.E. Bofinger
`and S.A Hackney, Ext. Abstract No. 136, 194'h Meeting of
`the Electrochemical Society Boston, USA, Nov. 1-6, 1998.
`S. Johnson, S.D. Korte, J.T. Vaughey, M.M.Thackeray, T.E.
`Bofinger, Y. Shao-Horn and S.A. Hackney, J. PowerSources
`81-82, 491-495 (1999).
`B. Amundsen, lO'h International Meeting on Lithium Bat(cid:173)
`teries, Como, Italy, May 28-Jun. 2, 2000.
`K. Numata and S. Yamanaka, Solid State ionics, 118, 117
`(1999).
`* cited by examiner
`
`Page 2 of 17
`
`Page 2 of 17
`
`

`
`M02
`1\
`xli2M'03•(1-x-y)LiM02
`
`Path of initial
`electrochemical
`delithiation
`
`/
`/ /
`
`\
`
`\
`
`\ y Li ',
`'
`'
`
`\
`
`\
`
`~
`0
`
`1--..
`
`\
`
`\
`
`\
`
`' \
`
`\
`
`\
`
`Li2M'03
`
`\
`
`' \
`' \
`
`\
`
`\
`\
`
`\
`
`\
`
`\
`
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`\
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`\
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`\
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`
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`
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`\ ' \
`
`\
`\
`
`\
`
`\
`
`\
`
`\
`
`\
`
`/
`xli2M'03•(1-x)LiM02
`
`LiM02
`
`(M'= e.g., Mn, Ti, Zr)
`
`(M= e.g., Mn, Ni)
`
`d •
`\Jl
`•
`~
`~ ......
`~ = ......
`
`~
`~
`?
`'"""' ~~
`N c c
`
`~
`
`'JJ. =(cid:173)~
`
`~
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`
`00
`
`e
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`rJ'l
`0'1
`'0-,
`""-l
`""-l
`b
`00
`N
`~
`N
`
`Page 3 of 17
`
`Page 3 of 17
`
`

`
`U.S. Patent
`
`Jan.13,2004
`
`Sheet 2 of 8
`
`US 6,677,082 B2
`
`lt)
`
`UJ
`G)
`
`CD ...
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`
`FIG. 2
`
`Page 4 of 17
`
`Page 4 of 17
`
`

`
`U.S. Patent
`
`Jan.13,2004
`
`Sheet 3 of 8
`
`US 6,677,082 B2
`
`-.
`0
`G)
`
`Q)
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`
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`,...
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`
`FIG. 3
`
`Page 5 of 17
`
`Page 5 of 17
`
`

`
`U.S. Patent
`
`Jan.13,2004
`
`Sheet 4 of 8
`
`US 6,677,082 B2
`
`-tl)
`
`Cl)
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`
`(SJIUn ·qJy) AIISUaJUI
`FIG. 4
`
`Page 6 of 17
`
`Page 6 of 17
`
`

`
`U.S. Patent
`
`Jan.13,2004
`
`Sheet 5 of 8
`
`US 6,677,082 B2
`
`(C
`(I')
`
`.....
`
`~ .....
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`
`FIG. 5
`
`Page 7 of 17
`
`Page 7 of 17
`
`

`
`U.S. Patent
`
`Jan.13,2004
`
`Sheet 6 of 8
`
`US 6,677,082 B2
`
`I r-..
`I r- 1--
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`
`Page 8 of 17
`
`Page 8 of 17
`
`

`
`U.S. Patent
`
`Jan.13,2004
`
`Sheet 7 of 8
`
`US 6,677,082 B2
`
`\
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`FIG. 7
`
`Page 9 of 17
`
`Page 9 of 17
`
`

`
`U.S. Patent
`
`Jan. 13,2004
`
`Sheet 8 of 8
`
`US 6,677,082 B2
`
`0 ...-
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`
`Page 10 of 17
`
`Page 10 of 17
`
`

`
`US 6,677,082 B2
`
`2
`trolyte 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
`5 combat such chemical degradation.
`Although the layered manganese compound LiMn02 has
`been successfully synthesized in the laboratory, it has been
`found that delithiation of the structure and subsequent
`cycling of the LixMn02 electrode in electrochemical cells
`10 causes a transition from the layered Mn02 configuration to
`the configuration of a spinel-type [Mn2]04 structure. This
`transformation changes the voltage profile of the
`Li/LixMn02 cell such that it delivers capacity over both a 4V
`and a 3V plateau; cycling over the 3V plateau is not fully
`15 reversible which leads to capacity fade of the cell over
`long-term cycling. Other types of LiMn02 structures exist,
`such as the orthorhombic-form, designated O-LiMn02 in
`which sheets of Mn0 6 octahedra are staggered in zig-zig
`fashion unlike their arrangement in layered LiMn02.
`20 However, O-LiMn02 behaves in a similar way to layered
`LiMn02 in lithium cells; it also converts to a spinel-like
`structure on electrochemical cycling.
`Therefore, further improvements must be made to LiM02
`electrodes, particularly LiMn02, to impart greater structural
`25 stability to these electrode materials during electrochemical
`cycling in lithium cells and batteries. This invention
`addresses the stability of LiM02 electrode structures, par(cid:173)
`ticularly LiMn02, and makes use of a Li2M'0 3 component
`to improve their stability.
`
`30
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`1
`LITHIUM METAL OXIDE ELECTRODES
`FOR LITHIUM CELLS AND BATTERIES
`
`RELATED APPLICATIONS
`
`This application claims priority under 35 U.S.C. §1.78(a)
`(3) provisional application Serial No. 60/213,618 filed Jun.
`22, 2000, the entire contents of which are incorporated
`herein by reference.
`
`CONTRACTUAL ORIGIN OF THE INVENTION
`
`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(cid:173)
`positions and structures, having in their initial state in an
`electrochemical cell, a general formula xLiM02.(1-x)
`Li2M'0 3 alternatively Li2_xM~'1 _x03_x in which O<x<l and
`where M is one or more trivalent ion with at least one ion
`being Mn, and where M is one or more tetravalent ions
`selected preferably from Mn, Ti and Zr; or, where M is one
`or more trivalent ion with at least one ion being Ni, and
`where M' is one or more tetravalent ion 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 LiM02
`component is essentially LiMn02 modified in accordance
`with this invention. In a further embodiment of 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 Mg2+ and
`Al3+ to impart improved structural stability or electronic
`conductivity to the electrode during electrochemical cycling.
`
`SUMMARY OF THE INVENTION
`
`40
`
`The invention consists of certain novel features and a
`combination of parts hereinafter fully described, illustrated
`35 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'0 3 -
`M02-LiM02 phase diagram, in which M is a trivalent ion
`(or ions) and M is a tetravalent ion (or ions);
`FIG. 2 depicts the X-ray diffraction pattern of a
`xLi2Mn0 3 .(1-x)LiNi0.8 Co0.20 2 electrode composition;
`FIG. 3 depicts the X-ray diffraction pattern of a xLi2
`Mn1_xTix0 3 .(1-x)LiNi0.8 Co0.20 2 electrode composition;
`FIG. 4 depicts the X-ray diffraction pattern of a xLi2Ti0 3 .
`(1-x)LiMn02 electrode composition;
`FIG. 5 depicts the electrochemical profile of a
`Li/xLi2Mn0 3 .(1-x)LiNi0.8 Co0.20 2 electrochemical cell;
`FIG. 6 depicts the electrochemical profile of a
`Li/xLi2Ti0 3 .(1-x)LiMn02 electrochemical cell;
`FIG. 7 depicts a schematic representation of an electro-
`55 chemical cell; and
`FIG. 8 depicts a schematic representation of a battery
`consisting of a plurality of cells connected electrically in
`series and in parallel.
`
`45
`
`Lithium-metal oxide compounds of general formula
`LiM02, where M is a trivalent transition metal cation Co,
`Ni, Mn, Ti, V, Fe, and with electrochemically inactive
`substituents such as Al are very well known and are of
`interest as positive electrodes for rechargeable lithium bat(cid:173)
`teries. The best-known electrode material is LiCo02, 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 50
`costly electrodes, for example, by partially substituting the
`cobalt ions within LiCo02 by nickel, such as in
`LiNi0.8 Co0.20 2 or by exploiting the manganese-based sys(cid:173)
`tem LiMn02. Such layered compounds are sometimes sta(cid:173)
`bilized by partially replacing the transition metal cations
`within the layers by other metal cations, either alone or in
`combination. For example, Mg2+ ions may be introduced
`into the structure to improve the electronic conductivity of
`the electrode, or Al3+ or Ti4 + ions to improve the structural
`stability of the electrode at high levels of delithiation. 60
`Examples of such compounds are LiNi0.8 Co0.15A10.050 2 and
`LiNio. 75Coo.1s Tio.osMgo.os02 ·
`A major problem of layered LiM02 compounds contain(cid:173)
`ing either Co or Ni (or both) is that the trivalent transition
`metal cations, M, are oxidized during charge of the cells to 65
`a metastable tetravalent oxidation state. Such compounds
`are highly oxidizing materials and can react with the elec-
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`
`This invention relates to stabilized LiM02 electrodes
`whereby an electrochemically inert rocksalt phase Li2M0 3
`is introduced as a component to the overall electrode struc(cid:173)
`ture as defined, in its initial state, by the general formula
`xLiM02.(1-x)Li2M'0 3 alternatively Li2 _xMxM' 1_x0 3 _x in
`
`Page 11 of 17
`
`Page 11 of 17
`
`

`
`US 6,677,082 B2
`
`5
`
`10
`
`3
`which 0<x<1, preferably 0.8~x<l, and more preferably
`0.9~x<1, and where M is one or more trivalent ions having
`at least one ion selected from Mn and where M' is one or
`more tetravalent ion selected preferably from Mn, Ti and Zr,
`or alternatively, where M is one or more trivalent ions
`having at least one ion selected from Ni and where M' one
`or more tetravalent ions having at least one ion selected from
`Mn. These compounds can be visualized as lying on the
`LiM0 2 -Li2M'0 3 tie-line of the Li2M'0 3 -M0 2 -LiM02 phase
`diagram shown schematically in FIG. 1.
`The rocksalt phase Li2 Mn0 3 has a layered-type structure
`in which discrete layers of lithium ions alternate with layers
`containing Mn and Li ions (in a 2:1 ratio) between the
`close-packed oxygen sheets. Note that, in this respect, the
`formula Li2Mn0 3 can be written in layered notation as
`Li(Mn213Li113)02 , in which the Li and Mn within round
`brackets represent the ions in one layer. A difference
`between Li2Mn0 3 and the layered LiM0 2 compounds is that
`the Mn ions in Li2Mn0 3 are tetravalent and cannot be easily
`electrochemically oxidized by lithium extraction, whereas in 20
`the LiM0 2 compounds the transition metal cations M are
`trivalent and can be electrochemically oxidized. Because
`Li2 Mn0 3 has a rocksalt phase, there is no energetically
`favorable interstitial space for additional lithium; therefore,
`Li2 Mn0 3 cannot operate as an insertion electrode and can(cid:173)
`not be electrochemically reduced. The xLiM0 2 .(1-x)
`Li2 M'0 3 structure can be regarded essentially as a com(cid:173)
`pound with a common oxygen array for both the LiM0 2 and
`Li2 Mn0 3 components, but in which the cation distribution
`can vary such that domains of the two components exist side
`by side. Such a domain structure does not rule out the
`possibility of cation mixing and structural disorder, particu(cid:173)
`larly at domain or grain boundaries. In a generalized
`xLiM0 2 .(1-x)Li2 M'0 3 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 xLiM0 2 .(1-x)Li2 M'0 3
`structure that contains monoclinic LiMn0 2 as the LiM0 2
`component, it is believed that the tetravalent M' ions can
`partially occupy the M positions in the monoclinic layered
`LiMn0 2 structure, thereby providing increased stability to
`the overall structure.
`Thus 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 LiM0 2 component is essentially LiMn0 2 . In a
`further embodiment of the invention, the transition metal
`ions and lithium ions may be partially replaced by minor
`concentrations (typically less than 10 atom percent) of other
`+ or Mg2
`mono- or multivalent cations such asA13
`+ to impart
`improved structural stability or electronic conductivity to the
`electrode during electrochemical cycling. In addition, the
`xLiM0 2 .(1-x)Li2 M'0 3 structures 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 depart slightly from the ideal stoichiometry
`as defined by the formula xLiM0 2 .(1-x)Li2 M'0 3 .
`It has been shown in the past that Li2 Mn0 3 (and isos(cid:173)
`tructural Li 2 Mn 1 _xZrx0 3 ) which is electrochemically
`inactive, can be used as a precursor material to form an
`electrochemically active charged xMn0 2 .(1-x)Li2 Mn0 3
`electrode structure in which x is approximately equal to 65
`0.91; this value of x translates to a composition of the
`layered structure Li1.1Mn0 .9 0 2 . These charged xMn0 2 .(1-
`
`4
`x)Li2 Mn0 3 compounds have been prepared by leaching
`Li2 0 from the Li2Mn0 3 (Li2 0.Mn0 2 ) 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 xMn0 2 .(1-x)Li2 Mn0 3 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(cid:173)
`tion yields a xLiMn0 2 .(1-x)Li2 Mn0 3 -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
`15 transformation can be avoided by starting directly with a
`discharged xLiMn0 2 .(1-x)Li2 Mn0 3 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 Li2Mn0 3
`.
`Furthermore, it is important to note that even though the
`relithiation of a xMn0 2 .(1-x)Li2 Mn0 3 electrode of the prior
`art in an electrochemical cell yields the same formulation as
`the electrodes of the present invention, i.e., xLiMn0 2 .(1-x)
`Li2 Mn0 3 , the applicants believe that the structures of the
`25 electrode materials of the present invention are significantly
`different from those of the prior art and will be unequivo(cid:173)
`cally distinguished from one another by high-resolution
`transmission electron microscopy, i.e., differences will be
`evident in the microstructural features of the xLiMn0 2 -(1-
`30 x)Li2 Mn0 3 electrodes of the present invention and those of
`the prior art. For example, because the lithiated 20
`xLiMn0 2 -(1-x)Li2 Mn0 3 electrode structures of the prior art
`are derived from a non-close-packed xMn0 2 -(1-x)Li2 Mn0 3
`structure, which is obtained by the acid leaching of, and Li20
`35 removal from, a Li2Mn0 3 precursor as described above, the
`microstructures of the prior art electrode materials 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 materials of
`40 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) xMn0 2 .(1-x)Li2Mn0 3 , is that they
`45 represent charged positive electrodes, whereas lithium-ion
`batteries require positive electrodes in the discharged state,
`for example, LiM0 2 electrodes (M=Co, Ni, Mn).
`Moreover, the charged xMn0 2 .1-x)Li2 Mn0 3 electrodes of
`the prior art require dehydration before use so that they can
`50 be used effectively in lithium cells. By contrast, the
`xLiMn0 2 .(1-x)Li2Mn0 3 electrodes of this invention are
`prepared in the discharged state and are essentially anhy(cid:173)
`drous materials and are more stable to heat-treatment and
`long-term storage in air compared to the xMn0 2 .(1-x)
`55 Li2 Mn0 3 materials of the prior art, which are known to
`transform on storage to a gamma-Mn0 2 -type structure as
`reported by Johnson et al in J. Power Sources 81-82, 491
`(1999).
`In one embodiment, this invention extends to include
`60 xLiM0 2 .(1-x)Li2 M'0 3 electrodes stabilized by isostructural
`rocksalt Li2 M'0 3 compounds other than M'=Mn, Ti, Zr as
`described in the preceding sections. Examples of such
`compounds are Li2 Ru0 3 , Li2 Re0 3 , Li21r03 , and Li2Pt03
`which may contribute a portion of the electrochemical
`capacity of the electrode.
`One of the difficulties that has been encountered in
`synthesizing xLiM0 2 .(1-x)Li2 M'0 3 electrodes, in which M
`
`Page 12 of 17
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`Page 12 of 17
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`

`
`US 6,677,082 B2
`
`5
`
`5
`is Mn, has been to keep the valency of the manganese ions
`equal, or close to its trivalent state. This has been success(cid:173)
`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-
`th.ermal process or method for synthesizing xLiM0 2 .(1-x)
`Ll2 M'0 3 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- 10
`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, 0.15LiMn0 2 .85Li2 Ti0 3 electrodes
`have been successfully prepared by this process from pre(cid:173)
`cursor materials consisting of manganese oxide (Mn 0 ),
`lithium hydroxide (LiOH.H20) and titanium isoprop~xide
`(Ti[OCH(CH3 ) 2 ] 4 ) in a potassium hydroxide (KOH) solu(cid:173)
`tion at 220° C. and at 15 atmospheres pressure.
`It has been recently demonstrated that layered lithium(cid:173)
`chromium-manganese-oxide and lithium-cobalt(cid:173)
`manganese-oxide electrodes of general formula xLiCr0 2 .
`(1-x)Li 2 Mn0 3 and xLiCo0 2 .(1-x)Li 2 Mn0 3 provide
`electrochemical stability when cycled between 4.5 and 2.0 V
`in electrochemical lithium cells. In particular, a
`Li(Cr 0 . 4 Mn 0 . 4 Li 0 . 2 )0 2 electrode (alternatively,
`0.4LiCr02 .0.4Li2Mn0 3 ) 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 Li2Mn0 3 component
`is ~lectrochemically inactive, the electrochemical capacity
`denved from the cell is due to the oxidation of Cr3
`+ to Cr 6
`+
`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
`Cr3 0 8 are dangerous and are a major health hazard whereas
`the electrodes of the present invention operate predomi(cid:173)
`nantly off a M3+/M4+ couple, notably a Mn3+/4+ couple. For
`the cobalt compound, xLiCo0 2 .(1-x)Li2 Mn0 3 , no signifi(cid:173)
`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(cid:173)
`trode.
`. The following examples of stabilized xLiMn0 2 .(1-x)
`L12 Mn0 3 electrodes containing either manganese and/or
`nickel describe the principles of the invention as contem(cid:173)
`plated by the inventors, but they are not to be construed as
`limiting examples.
`
`EXAMPLE 1
`The material 0.2Li2Mn0 3 .0.8LiNi0 .8 Co 0 .2 0 2 that can be
`written, alternatively, as Li(Ni058Mn0 .18Co 0 .15Li0 .09)0 2
`was prepared by the reaction of Ni(N0 3 ) 2 , Co(N03 ) 2 ,
`Mn0 2 , 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 55
`essentially single-phase product with a layered-type struc(cid:173)
`ture (FIG. 2).
`
`EXAMPLE 2
`The material 0.2Li2Mn1 _xTix0 3 .0.8LiNi0 .8 Co0 .2 0 2 , where
`x=0.5, which can be written, alternatively, as
`Li(Ni0 .s8Mn0 .09 Ti0 .09Co 0 .15Li0 .09)02 was prepared by the
`reaction of Ni(N0 3 ) 2 , Co(N03 ) 2 , Mn0 2 , Ti0 2 (anatase) and
`LiOH in the required stoichiometric amounts at 800° C. in
`air or oxygen for about 16 hours. The powder X-ray dif(cid:173)
`fraction pattern of this compound indicates an essentially
`single-phase product with a layered-type structure (FIG. 3).
`
`6
`EXAMPLE 3
`
`The material 0.15Li 2 Ti0 3 .0.85LiMn02
`that can be
`written, alternatively, as Li(Ti0 .14Mn0 .79Li0 m)0 2 was pre(cid:173)
`pared by the hydrothermal reaction of Mn2 0 3 , Ti0 2
`(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(cid:173)
`type structure (FIG. 4).
`
`)
`
`EXAMPLE 4
`The xLiM0 2 .(1-x)Li2 M'0 3 electrode materials were
`evaluated in coin cells (size 2032) 20 mm diameter and 3.2
`15 mm high against a counter lithium electrode. The cells had
`t~e configuration: Li/1M LiPF 6 in ethylene carbonate (EC),
`d1.ethrl c~rbon.ate (DEC) (1:1)electrolyte/xLiM0 2 .(1-x)
`Ll2 M 0 3 , m wh1ch the xLiM0 2 .(1-x)Li2 M'0 3 electrode con(cid:173)
`sisted of 0.2Li 2 Mn0 3 .0.8LiNi 0 . 8 Co 0 . 20 0 2 or
`20 0.15Li2Ti0 3 .0.85LiMn02 . Other electrolytes well known in
`the art may be used. Laminated electrodes were made
`c~nta~ning approx~mately 7 to 10 mg of the xLiM0 2 .(1-x)
`L12 M 0 3 powder, 1.e., approximately 82% by weight of the
`laminate electrode, intimately mixed with approximately
`25 10% by weight of a polyvinylidene difluoride (Kynar PVDF
`polymer binder) and approximately 8% by weight of a
`suitable carbon (i.e. graphite, such as Timcal SFG-6, or
`acetylene black, such as Chevron XC-72) in 1-methyl-2-
`pyrrolidinone (NMP). Other binders are well known in the
`30 art and may be substituted here. The slurries were coated
`with a doctor blade onto an aluminum foil substrate current
`collector. The coatings were dried in vacuum at temperatures
`from 70° C. for about 12 hours, and punched out as electrode
`laminates. Metallic lithium foil was used as the counter
`35 electrode. Li/xLiM0 2 .(1-x)Li2M'0 3 cells were discharged
`and charged at constant current (typically 0.1 mNcm2
`within the voltage range 4.5 to 2.0 V.
`. Typical electrochemical data for Li/xLiM0 2 .(1-x)
`L12 M'0 3 cells are provided in various plots, as shown in
`40 FIG. 5, a Li/0.2Li2Mn0 3 .0.8LiNi0 .8 Co0 .2 0 2 cell; and FIG.
`6, a Li/0.15Li2 Ti0 3 .0.85LiMn02 cell. For example, the
`electrode
`of
`Example
`1,
`namely
`0.2Li2 Mn0 3 .0.8LiNi0 .8 Co 0 .2 0 2 has a theoretical electro(cid:173)
`chemical capacity of 212 mAh/g. The electrochemical data
`45 in FIG. 5 indicate that an initial capacity of approximately
`208 mAh/g can be achieved from this electrode during the
`'break-in' process on the initial charge of the cell and,
`thereafter, a steady rechargeable discharge capacity of
`approximately 136 mAh/g. For the stabilized
`50 0.15Li2Ti0 3 .0.85LiMn02 electrode of Example 3, as seen in
`FIG. 6, a capacity of 179 mAh/g was achieved during the
`'break-in ' process on the initial charge of the cell, and
`thereafter a rechargeable capacity of 108 mAh/g was
`achieved.
`The data in the examples provided above indicate that the
`principle of this invention can be used to stabilize LiM0 2
`compounds with a Li2 M'0 3 component, and specifically
`t~ose containing M=Ni and/or Mn that are of major sig(cid:173)
`mficance and interest to the lithium battery industry for
`60 replacing the lithium-cobalt-oxide, LiCo0 2 , as the electrode
`of choice, thereby reducing cost. The performance and
`effectiveness of the xLiM0 2 .(1-x)Li2 M0 3 electrodes
`(0<x<1) of this invention depend on the concentration of the
`trivalent transition metal ions, M, in the structure, that is the
`65 value of "x" which preferably is equal to or greater than 0.8
`and less than 1. A major advantage of the compounds of this
`invention is that the concentration of the trivalent M ions,
`
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`US 6,677,082 B2
`
`10
`
`7
`the concentration of stabilizing tetravalent M' ions and
`concentration of monovalent lithium ions can be tailored in
`such a way to extend and optimize both the capacity of the
`electrode as well as the stabilizing effect of the Li2 M'0 3
`component in the structure. For example, an electrode with
`the composition 0.9LiMn 0 . 9 Ni0.10 2 .0.1Li 2 Ti0 3
`(alternatively Li1.2Mn0 .72Ni0 .08 Ti0 .2 0 2 .2 ) has a theoretical
`capacity of 252 mAh/g, which is only 8% less than that of
`LiCo0 2 used in state-of-the-art lithium cells.
`This invention, therefore, relates to a lithium-metal-oxide
`positive electrode for a non-aqueous electrochemical lithium
`cell as shown schematically in FIG. 7, the cell represented
`by the numeral10 having a negative electrode 12 separated
`from a positive electrode 16 by an electrolyte 14, all
`contained in an insulating housing 18 with suitable terminals 15
`(not shown) being provided in electronic contact with the
`negative electrode 12 and the positive electrode 16. Binders
`and other materials normally associated with both the elec(cid:173)
`trolyte and the negative and positive electrodes are well
`known in the art and are not described herein, but are
`included as is understood by those of ordinary skill in this
`art. FIG. 8 shows a schematic illustration of one example of
`a battery in which two strings of electrochemical lithium
`cells, described above, are arranged in parallel, each string
`comprising three cells arranged in series.
`While particular embodiments of the present invention
`have been shown and described, it will be appreciated by
`those skilled in the art that changes and modifications may
`be made without departing from the invention in its broader
`aspects. Therefore, the aim in the appended claims is to
`cover all such changes and modifications as fall within the
`true spirit and scope of the invention.
`The embodiments of the invention in which an exclusive
`property or privilege is claimed are defined as follows:
`1. A lithium metal oxide positive electrode for a non(cid:173)
`aqueous lithium cell prepared in its initial discharged state
`having a general formula xLiM0 2 .(1