US20050042128A1 - Negative active material for rechargeable lithium battery, method of preparing same and rechargeable lithium battery - Google Patents

Negative active material for rechargeable lithium battery, method of preparing same and rechargeable lithium battery Download PDF

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US20050042128A1
US20050042128A1 US10/923,300 US92330004A US2005042128A1 US 20050042128 A1 US20050042128 A1 US 20050042128A1 US 92330004 A US92330004 A US 92330004A US 2005042128 A1 US2005042128 A1 US 2005042128A1
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phase
alloy
active material
negative active
sim
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Inventor
Keiko Matsubara
Akira Takamuku
Toshiaki Tsuno
Sung-Soo Kim
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Samsung SDI Co Ltd
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Samsung SDI Co Ltd
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Priority claimed from JP2003299282A external-priority patent/JP3746499B2/ja
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Assigned to SAMSUNG SDI CO., LTD. reassignment SAMSUNG SDI CO., LTD. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: KIM, SUNG-SOO, MATSUBARA, KEIKO, TAKAMUKU, AKIRA, TSUNO, TOSHIAKI
Publication of US20050042128A1 publication Critical patent/US20050042128A1/en
Priority to US12/182,998 priority Critical patent/US7658871B2/en
Abandoned legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C29/00—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides
    • C22C29/18—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on silicides
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C28/00—Alloys based on a metal not provided for in groups C22C5/00 - C22C27/00
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • H01M2300/0028—Organic electrolyte characterised by the solvent
    • H01M2300/0037—Mixture of solvents
    • H01M2300/004—Three solvents
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to a negative active material for a rechargeable lithium battery, a method of preparing the same, and a rechargeable lithium battery.
  • a negative active material comprising an amorphous structured alloy improves a battery's cycle characteristics in 43 rd Preview of Battery Discussion (The Electrochemical Society of Japan, The Committee of Battery Technology, Oct. 12, 2002, p. 308-309).
  • Si is expected to provide a higher capacity
  • Si is generally known to be too hard to be transferred to an amorphous phase either by itself or in an Si-alloy form.
  • Si material can be transferred into amorphous phase via a mechanical alloying process.
  • amorphous alloy material has a good early stage capacity retention rate relative to that of crystalline alloy material, but that capacity tends to remarkably decrease after repeated charge-discharge cycles.
  • the expansion rate upon charging is relatively low and the characteristics deteriorate less upon repeated charge and discharge compared to those for crystal material.
  • the amorphous material can improve the early stage cycle characteristics better than crystal material because the lithium ion is better diffused.
  • the active material is not fully charged in the very early stage, the utilization of an active material is slowly increased upon repeating cycles and, as a result, the deterioration of the cycle characteristics due to the pulverization of the material to a fine powder is alleviated. However, upon repeating the cycles, it is anticipated that the cycle characteristics will deteriorate due to the pulverization of the material to a fine powder and the exhaustion of the active material.
  • a pulverizing step into fine powder and a compressing step are repeated to slowly reduce the crystal degree to provide an amorphous or pulverized material.
  • a process may cause problems in that the interface is broken between the tiny alloy structures identified via a X-ray diffraction analysis, and the structure is easily broken upon intercalating lithium ions and pulverized. Thereby the cycle characteristics deteriorate.
  • a negative active material is provided that is capable of preventing the active material from pulverizing into fine powder resulting in improved cycle characteristic. Further embodiments include a method of preparing such a negative active material, and a rechargeable lithium battery comprising the negative active material.
  • a negative active material for a rechargeable lithium battery in which the material consists essentially of Si phase and SiM phase material with at least one of X phase and SiX phase, wherein each crystalline grain of the phases has a diameter of between 100 nm and 500 nm, and wherein the element M is selected from the group consisting of Ni, Co, B, Cr, Cu, Fe, Mn, Ti, Y, and combinations thereof, and the element X is selected from the group consisting of Ag, Cu, Au, and combinations thereof, provided that Cu is not selected for both element M and element X.
  • FIG. 1 is a SEM photograph of the negative active material of Example 1;
  • FIG. 2 is a SEM photograph of the negative active material of Example 2.
  • FIG. 3 is a SEM photograph of the negative active material of Example 3.
  • FIG. 4 is a SEM photograph of the negative active material of Example 4.
  • FIG. 5 is a graph illustrating the X-ray refraction pattern of the particles of each step in Example 1 and the active material of Example 2;
  • FIG. 6 is a graph illustrating the relationship between the number of cycles and the discharge capacities for the rechargeable lithium batteries of Examples 1 to 4.
  • a negative active material for a rechargeable lithium battery has a crystal grain comprising Si phase and SiM phase with a very small diameter of 500 nm or less with the grains closely aggregated with one another. According to this structure, it is difficult to destroy the structure even though expansion and contraction are repeated upon charging and discharging the lithium. These properties can improve the cycle characteristics.
  • the structure comprises SiM phase in addition to Si phase, the volume to be expanded and contracted for the particle can be reduced which can prevent the pulverization of the particle into fine powder such as occurs with a negative active material with a single Si phase. Consequently, the cycle characteristics are improved.
  • the structure can prevent a reduction in the specific resistance of the negative active material as it comprises either one or both of X phase and SiX phase.
  • Cu is alloyed with Si, because it has a specific resistance lower than that of Si, it can reduce the specific resistance of the negative active material. While Cu can be used for either of element M or element X, it is important that elements M and X be different. Accordingly, Cu is not selected for both element M and element X when practicing the present invention.
  • element M is preferably selected to have a boiling point higher than that of element X.
  • the negative active material for the rechargeable lithium battery of the present invention is prepared by mechanically alloying Si particles provided in a powder form and particles of element M, also in powder form.
  • the resulting SiM alloy is heated and element X is added as a powder to the heated SiM alloy.
  • the mixture is alloyed again by a mechanical alloying method to provide a SiMX alloy, and heated at a temperature less than that of the first heating step.
  • Element M is selected from the group consisting of Ni, Co, B, Cr, Cu, Fe, Mn, Ti, Y, and combinations thereof
  • element X is selected from Ag, Cu, Au, and combinations thereof, provided however, that Cu is not selected for both element M and element X at the same time.
  • the negative active material for the rechargeable lithium battery is obtained by alternatively repeating a mechanical alloying step and a heating step.
  • the structure of the obtained negative active material is very closely aggregated and has a tiny crystal phase. Since the second heating temperature is less than that of the first heating temperature, the previously formed SiM phase is not melted during the second heating process and it is possible to deposit the tiny crystal of Si phase, SiM phase, X phase and SiX phase.
  • the resulting negative active material preferably has a crystal structure with a crystal grain diameter between 100 nm and 500 nm.
  • the rechargeable lithium battery of the present invention comprises the aforementioned negative active material for the rechargeable lithium battery. Thereby, it is possible to provide a rechargeable lithium battery with good cycle characteristics.
  • the temperature of the first heating step is preferably between (Tm-100)° C. and (Tm-20)° C. where Tm is the melting point of the SiM alloy phase.
  • the negative active material for the rechargeable lithium battery of the present invention is constructed of crystal powder which consists essentially of Si phase and SiM phase with at least one of X phase and SiX phase.
  • each of Si phase, SiM phase, X phase, and SiX phase is a crystal particle having a diameter of between 100 nm and 500 nm, and the phases are closely aggregated with one another.
  • the Si phase is alloyed with the lithium upon charging the battery to form a LiSi X phase, and the lithium is released upon discharge to return to Si single phase. Further, the SiM phase does not react with the lithium upon charge or discharge and the shape of the powder particle remains which prevents the particles form expanding and contracting.
  • the element M of the SiM phase is not alloyed with the lithium and M is preferably an element selected from the group consisting of Ni, Co, B, Cr, Cu, Fe, Mn, Ti, Y and combinations thereof.
  • the element M is most preferably Ni.
  • the composition of the SiM phase is Si 2 Ni phase.
  • Element M preferably has a melting point higher than that of element X.
  • Element X decreases the specific resistance of the negative active material by providing better conductivity to the negative active material powder.
  • Element X is preferably a metal element having a specific resistance of 3 ⁇ m or less and is preferably selected from the group consisting of Ag, Cu, Au and combinations thereof. Particularly, Cu will not alloy with the lithium to decrease the irreversible capacity. Thereby, it is possible to increase the capacity of the charge and discharge.
  • Cu is not alloyed with Si and, at the same time, has a specific resistance less than that of Si, decreasing the specific resistance of the negative active material. Therefore, Cu has features of both element M and element X, but according to the present invention, Cu is not selected for both element M and element X at the same time.
  • SiX phase decreases the specific resistance of the negative active material by applying the conductive to the multi-phase alloy powder as in the X phase.
  • the crystal structure of Si phase, SiM phase, X phase, and SiX phase is preferably a crystal phase. However, it may further comprise other phases which may be crystal or amorphous.
  • Each phase preferably has a crystal grain diameter of between 100 nm and 500 nm.
  • the crystal grain has a diameter of less than 100 nm, the particle becomes weaker by the repeated pulverization into fine powder and compression, and the interface is peeled out to be pulverized into fine powder by expanding and contracting upon the charge and discharge.
  • the diameter is more than 500 nm, the expansion rate is increased by charging the main active material of Si phase, and it is difficult to prevent the Si phase from expanding due to the SiM phase, the X phase and the SiX phase.
  • the average diameter of the negative active material powder is preferably between 5 ⁇ m and 30 ⁇ m.
  • a Si-included alloy particle has a resistance more than that of graphite powder generally used for the conventional negative electrode material of a lithium ion battery, it is preferable to add a conductive agent.
  • an average diameter less than 5 ⁇ m is undesirable in that the multi-phase alloy particle may have an average diameter less than that of the conductive agent, thus it is difficult to achieve the desired effects of the conductive agent and the battery characteristics such as capacity and cycle characteristics deteriorate.
  • the average diameter is more than 30 ⁇ m, it is undesirable because the charge density of the negative active material decreases for a lithium battery.
  • the particle shape of the negative active material is mostly estimated as being amorphous.
  • the negative active material has a composition ratio of Si between 30% by weight and 70% by weight.
  • element M is an element forming a SiM phase together with Si, it is preferable to add it in amount less than that of the stoichiometric concentration of Si.
  • the amount of element M is more than the stoichiometric concentration of Si, it is undesirable in that Si is relatively unable to deposit the SiM phase and M phase so that the Si phase contributing to the charge and discharge is not deposited. Thereby, the charge and discharge is not generated.
  • too little M it is undesirable because the Si phase is overly deposited to increase the total expansion volume of the negative active material upon the charge and discharge, and the negative active material is pulverized into fine powder to deteriorate the cycle characteristics.
  • the composition of the element M in the negative active material is between 20% by weight and 69% by weight.
  • the element M is not alloyed with the lithium so that it does not have the irreversible capacity.
  • the composition ratio of element X When the composition ratio of element X is increased, the specific resistance is decreased, but the Si phase is relatively decreased, thus deteriorating the charge and discharge capacity. On the other hand, when the composition ratio of element X is decreased, the specific resistance of the negative active material is increased, deteriorating the charge and discharge effectiveness. For this reason, the composition ratio of the element X is preferable between 1% by weight and 30% by weight in the negative active material.
  • the negative active material for a rechargeable lithium battery has a crystal grain of Si phase and SiM phase having a very small diameter of 500 nm or less and each grain is closely aggregated.
  • the structure is rarely destroyed or pulverized even with the expansion and contraction caused by the charge and discharge of the lithium, so that the cycle characteristic are improved.
  • the volume of expanding and contracting the particles may decrease compared to Si single phase. This prevents the particle from pulverizing into fine powder so that the cycle characteristics are improved.
  • the specific resistance of the negative active material decreases.
  • the rechargeable lithium battery comprises at least a negative electrode comprising the negative active material, a positive electrode, and an electrolyte.
  • the negative electrode for the rechargeable lithium battery may be, for example, a sheet-shaped electrode formed by solidifying the alloy powder of the negative active material with a binder. Further examples include a pellet solidified as a disc shape, a cylinder shape, a plan shape or a conical shape.
  • the binder may be either an organic or an inorganic material capable of being dispersed or dissolved in a solvent with a negative active material alloy powder.
  • the alloy particles are bound by removing the solvent.
  • the binder may be a material capable of being dissolved with the alloy powder and binding the alloy powder by a solidification process such as a press shaping process.
  • binders include resins such as vinyl based resins, cellulose based resins, phenol resins, and thermoplastic resins. More specific examples include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose, styrene butadiene rubber, and similar materials.
  • the negative electrode may be prepared by further adding carbon black, graphite powder, carbon fiber, metal powder, metal fiber, or some other material as a conductive agent.
  • the positive electrode comprises, for example, a positive active material capable of intercalating and deintercalating the lithium such as LiMn 2 O 4 , LiCoO 2 , LiNiO 2 , LiFeO 2 , V 2 O 5 , TiS, MoS, organosulfide compounds, polysulfide compounds and a Ni, Mn, or Co based composite oxide.
  • the positive electrode may further include a binder such as polyvinylidene fluoride and a conductive agent such as carbon black in addition to the positive active material.
  • the positive electrode and the negative electrode may be exemplified as a sheet-shaped electrode prepared by coating the conductor of a metal foil or a metal mesh on the positive electrode or the negative electrode.
  • the electrolyte may include an organic electrolyte with which the lithium is dissolved in an aprotonic solvent.
  • Aprotonic solvents include, but are not limited to, propylene carbonate, ethylene carbonate, butylene carbonate, benzonitrile, acetonitrile, tetrahydrofurane, 2-methyl tetrahydrofurane, ⁇ -butyrolactone, dioxolane, 4-methyl dioxolane, N,N-dimethyl formamide, dimethyl acetoamide, dimethyl sulfoxide, dioxane, 1,2-dimethoxy ethane, sulfolane, dichloroethane, chlorobenzene, nitrobenzene, dimethyl carbonate, methylethyl carbonate, diethyl carbonate, methylpropyl carbonate, methyl isopropyl carbonate, ethylbutyl carbonate, dipropyl carbonate, diisopropyl carbonate, dibutyl carbonate, diethylene glycol, dimethyl ether or similar solvents or mixtures of such solvents with other solvents such
  • the lithium salt may include, but is not limited to, LiPF 6 , LiBF 4 , LiSbF 6 , LiAsF 6 , LiCIO 4 , LiCF 3 SO 3 , Li(CF 3 SO 2 ) 2 N, LiC 4 F 9 SO 3 , LiSbF 6 , LiAIO 4 , LiAICl 4 , LiN(CxF 2 x+1SO 2 )(CyF 2 y+1SO 2 ) (where x and y are natural number), LiCl, LiI, or mixtures thereof, and preferably is any one of LiPF 6 , LiBF 4 , LiN(CF 3 SO 2 ) 2 , and LiN(C 2 F 5 SO 2 ).
  • the electrolyte may further include a polymer such as PEO, PVA or similar polymers with any one of the lithium salts, and polymer electrolyte incorporated with the polymer in the organic electrolyte.
  • a polymer such as PEO, PVA or similar polymers with any one of the lithium salts, and polymer electrolyte incorporated with the polymer in the organic electrolyte.
  • the rechargeable lithium battery may further comprise, if required, any other material such as a separator interposing the positive electrode and the positive electrode.
  • the rechargeable lithium battery comprises a negative active material having a crystal grain such as a Si phase and a SiM phase having a very small diameter of 500 nm or less, or with the phases closely aggregated with each other, it is rarely possible to destroy the structure even though the expansion and contraction are repeated upon charging and discharging the lithium. Thereby, the cycle characteristics of the battery are improved.
  • the method comprises the steps of: first alloying an element Si and an element M by a mechanical alloying process to provide a SiM phase alloy; first heating the SiM alloy; adding a powder of element X to the heated SiM alloy; second alloying the same by a mechanical alloying process to provide a SiMX alloy; and second heating the SiMX alloy.
  • Si powder and an element M powder are mixed and alloyed by a mechanical alloying process at the first alloying step.
  • Si powder may include any one having an average diameter of between 1 and 10 ⁇ m
  • the element M powder may include any one having an average diameter of between 0.5 and 10 ⁇ m.
  • the Si powder and the element M are introduced into a ball mill and an attritor and alloyed by the mechanical alloy in which the pulverization into fine powder and the compression are repeated. Thereby, a SiM alloy is obtained.
  • the mechanical alloying process is preferably continued until the SiM alloy becomes amorphous.
  • the heating temperature T 1 is preferably between (Tm-100)° C. and (Tm-20)° C. where Tm is the melting point of the SiM alloy phase.
  • Tm is the melting point of the SiM alloy phase.
  • the heating temperature T 1 is less than (Tm-100)° C., the SiM alloy is insufficiently crystallized, while when the heating temperature T 1 is more than (Tm-20)° C., the alloy crystal structure is too large.
  • the heating time is preferable between 1 and 4 hours.
  • the heating step is preferably carried out under an inert gas atmosphere of nitrogen, argon or a similar gas. Upon heating the SiM alloy, the Si phase and the SiM phase are developed with the resulting structure having a crystal grain diameter of between 100 and 500 nm.
  • the mixture of the SiM alloy and the element X powder is alloyed by the mechanical alloy process.
  • the element X powder has an average diameter of between 0.5 and 10 ⁇ m.
  • the SiM alloy and the element X are introduced into, for example, a ball mill or an attritor, and are alloyed by a mechanical alloying process in that the pulverization into fine powder and the compression are repeated. Thereby, a SiMX alloy is obtained.
  • the mechanical alloying process is preferably continued until the SiMX alloy becomes amorphous.
  • the SiMX alloy is heated to transfer the amorphous state into the crystalline state.
  • the temperature T 2 in the second heating step is lower than the temperature T 1 of the first heating step, and the second heating process is preferably carried out between (Tx-200)° C. and (Tx-20)° C. where T x is the melting point of the metal X. If the second heating temperature T 2 is higher than the first heating temperature T 1 , the crystal grain of the SiM phase will dissolve and upon re-crystallization will tend to swell. When the second heating temperature T 2 is higher than (Tx-200)° C., the SiX alloy is insufficiently crystallized.
  • the X phase is re-crystallized so that the desired tiny crystal grain is not obtained.
  • the duration of the heating step is preferable between 2 and 5 hours.
  • the heating step is preferably carried out under an inert gas atmosphere of nitrogen, argon or a similar gas.
  • the element M preferably has a higher melting point than that of element X to prevent the SiM phase from melting during the second heating step.
  • the mechanical alloying process and the heating process are alternatively repeated, so that the structure of the negative active material becomes very dense with a tiny crystal phase.
  • the previously formed SiM phase is not melted during the second heating step. This permits the formation of the desired tiny crystals of Si phase, SiM phase, X phase, and SiX phase.
  • the alloy powders obtained from Experimental Examples 1 to 4 were measured by scanning electronic microscope (SEM) for their surfaces.
  • SEM scanning electronic microscope
  • the SEM photograph of the alloy powder of Experimental Example 1 is shown in FIG. 1 ;
  • the SEM photograph of the alloy powder of Experimental Example 2 is shown in FIG. 2 ;
  • the SEM photograph of the alloy powder of Experimental Example 3 is shown in FIG. 3 ;
  • the SEM photograph of the alloy powder of Experimental Example 4 is shown in FIG. 4 .
  • the structure of alloy powder of Experimental Example 1 has a very tiny crystal grain and the crystal grain is closely aggregated. Further, comparing that of Experimental Example 2, it is found that fewer cracks are generated and the surface of crystal grain is smoother.
  • the diameter of the crystal grain determined from a SEM photograph is between 100 nm and 300 nm. Further, according to Experimental Examples 3 and 4, the crystal grain is large in the structure and the crystal grain is broken. In the Experimental Example 4, the surface of the crystal grain is smooth but the particle size of the crystal grain is bigger than that of Experimental Example 1.
  • the alloy powder of Experimental Example 1 has a fine crystal grain, and the crystal grains are closely aggregated.
  • the material treated only by a mechanical alloying step, the material treated by a mechanical alloying step and a 970° C. heating step, and the material treated by a mechanical alloying step, heating step, a Ag adding step and a heating step at 940° C. in Experimental Example 1, and the material treated by a mechanical alloying step and a heating step at 940° C. in Experimental Example 2 are measured for X-ray diffraction pattern and the results are shown in FIG. 5 .
  • the material treated with only a mechanical alloying process has a very small and broad diffraction peak, which is anticipated as being amorphous. It is crystallized by heating the material. As shown in the photograph, it is confirmed that each structure inside the alloys is very small as being less than 300 nm and crystalline. The size of the crystal grain is tiny and the surface of the crystal grain is very smooth.
  • rechargeable lithium batteries were prepared. 70 parts by weight of each of the negative active materials according to Experimental Examples 1 to 4, 20 parts by weight of graphite powder of conductive agent having an average diameter 3 ⁇ m, and 10 parts by weight of polyvinylidene fluoride were mixed, and added with N-methyl pyrrolidone under agitation to provide a slurry. Then, the slurry was coated on a copper foil having a thickness of 14 ⁇ m and the coated copper foil was dried and compressed to provide a negative electrode having a thickness of 40 ⁇ m. The obtained negative electrode was cut in a circle shape having a diameter of 13 mm.
  • the electrolyte was injected thereto to provide a coin type rechargeable lithium cell.
  • the resulting lithium cell was repeatedly charged and discharged at voltages of between 0V and 1.5V and at 0.2 C current density for 20 cycles.
  • the relationship between the number of cycles and the discharge capacity at each cycle is shown in FIG. 6 .
  • the negative active material for the rechargeable lithium battery of the present invention had a very small particle diameter of crystal such as Si phase, SiM phase and so on, and each phases were closely alternatively linked. Thereby, the structure was rarely broken upon the charge and discharge and the cycle characteristics were improved.
  • the mechanical alloy and the heating processes were alternatively repeated. Thereby, the structure was so dense to provide a negative active material having a tiny crystalline state.

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US10/923,300 2003-08-22 2004-08-20 Negative active material for rechargeable lithium battery, method of preparing same and rechargeable lithium battery Abandoned US20050042128A1 (en)

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JP2003299282A JP3746499B2 (ja) 2003-08-22 2003-08-22 リチウム二次電池用負極活物質及びその製造方法並びにリチウム二次電池
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KR10-2004-0009366A KR100529103B1 (ko) 2003-08-22 2004-02-12 리튬 이차 전지용 음극 활물질, 그의 제조 방법 및 리튬이차 전지

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US20050074672A1 (en) * 2003-10-01 2005-04-07 Keiko Matsubara Negative active material for rechargeable lithium battery, method of preparing same and rechargeable lithium battery using same
US20070148544A1 (en) * 2005-12-23 2007-06-28 3M Innovative Properties Company Silicon-Containing Alloys Useful as Electrodes for Lithium-Ion Batteries
US20100243964A1 (en) * 2009-03-30 2010-09-30 Lg Chem, Ltd. Composite for electrode active material and secondary battery comprising the same
US20110212363A1 (en) * 2010-02-26 2011-09-01 Semiconductor Energy Laboratory Co., Ltd. Power storage system and manufacturing method therefor and secondary battery and capacitor
EP2416410A2 (en) * 2009-03-30 2012-02-08 LG Chem, Ltd. Composite for electrode active material and secondary battery comprising the same
US8455044B2 (en) 2010-11-26 2013-06-04 Semiconductor Energy Laboratory Co., Ltd. Semiconductor film, method for manufacturing the same, and power storage device
US8821601B2 (en) 2011-01-21 2014-09-02 Semiconductor Energy Laboratory Co., Ltd. Hydrogen generating element, hydrogen generation device, power generation device, and driving device
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