JP5103789B2 - Negative electrode for lithium secondary battery and lithium secondary battery using the same - Google Patents

Description

  The present invention relates to a negative electrode for a lithium secondary battery and a lithium secondary battery using the same.

  2. Description of the Related Art In recent years, as mobile devices have higher performance and more functions, there is a strong demand for higher capacities of secondary batteries that are power sources thereof. There is a lithium secondary battery as a secondary battery that meets this requirement. Recently, studies have been actively made on high capacity negative electrodes for lithium secondary batteries (hereinafter also referred to as negative electrodes) using silicon (Si), germanium (Ge), tin (Sn) or the like as a negative electrode active material. However, when these negative electrodes are repeatedly charged and discharged, they are pulverized and refined by vigorous expansion and contraction of the negative electrode active material, resulting in a decrease in current collection or an accelerated decomposition reaction due to an increase in surface area. The cycle characteristics were not improved. Therefore, negative electrodes in which a negative electrode active material layer is formed on a current collector by a vapor phase method, a liquid phase method, a sintering method, or the like have been studied (see, for example, Patent Document 1 and Patent Document 2).

  According to these, the current collector and the negative electrode active material layer can be integrated as well as miniaturization can be suppressed as compared with a conventional coated negative electrode coated with a slurry containing a particulate negative electrode active material and a binder. Therefore, the electron conductivity in the negative electrode becomes extremely good, and high performance is expected in terms of capacity and cycle life. In addition, since it is possible to reduce or eliminate the conductive material, binder, voids, and the like that have conventionally existed in the negative electrode, it is possible to essentially increase the capacity of the negative electrode.

  Next, as a means for increasing the capacity of the battery, in order to increase the electrode area per sheet and improve the characteristics during discharging and charging with a large current, the strip-shaped positive electrode and the strip-shaped negative electrode are connected via a separator. A wound electrode group structure wound in a spiral shape is used (see, for example, Patent Document 3).

  In such a wound battery, there has been a problem that an internal short circuit due to, for example, lithium dendrite or chipping of active material particles shortens the cycle life.

  In order to solve these problems, an insulating layer is provided between the negative electrode and the separator, and the internal short circuit that occurs when the dendrite generated on the negative electrode surface penetrates the separator when charging and discharging are repeated eliminates the charge. Efforts have been made to improve the discharge cycle life (see, for example, Patent Document 4).

Also, at least one end face of the positive electrode active material layer and the negative electrode active material layer is coated with an insulating material particle aggregate layer to prevent chipping from the end face of the active material and to improve internal short circuit. (For example, refer to Patent Document 5).
JP 11-339777 A Japanese Patent Laid-Open No. 11-135115 JP-A-9-293537 JP-A-6-168737 WO 98/38688 pamphlet

  However, when the active material repeatedly expands and contracts during charge and discharge, the negative electrode outermost peripheral portion wound in a spiral shape and the negative electrode active material edge of the innermost peripheral portion rub against the separator, and the separator breaks and the positive electrode active material or The positive electrode current collector and the negative electrode active material or the negative electrode current collector are internally short-circuited, resulting in a problem that the cycle life is shortened.

  The present invention has been made in view of such problems, the purpose of which is the deterioration of the separator that occurs in the outermost peripheral portion and the innermost peripheral portion of the wound electrode plate due to expansion and contraction associated with charging and discharging of the negative electrode active material layer, An object of the present invention is to provide a negative electrode capable of alleviating breakage and improving cycle life and a battery using the negative electrode.

In order to solve the above conventional problems, the negative electrode of the present invention is
A negative electrode comprising a long current collector and a negative electrode active material layer formed on the surface of the current collector,
The negative electrode active material layer is formed on the current collector surface and includes a first negative electrode active material layer including a first negative electrode active material composed of a plurality of columnar particles;
Adjacent to the first negative electrode active material layer, the height decreases toward the terminal end in the longitudinal direction of the current collector, and the oxygen concentration contained increases toward the terminal end in the longitudinal direction of the current collector. A second negative electrode active material layer containing a second negative electrode active material formed on
It is characterized by including.

  With this configuration, deterioration and breakage of the separator due to rubbing between the negative electrode active material edge and the separator generated at the outermost and innermost negative electrodes of the wound electrode plate due to expansion and contraction accompanying charging and discharging of the negative electrode active material can be mitigated. The cycle life can be improved by eliminating an internal short circuit between the positive electrode active material or positive electrode current collector and the negative electrode active material or negative electrode current collector.

  According to the negative electrode of the present invention and the wound battery using the negative electrode, the negative electrode active material at the time of charge and discharge is used in the negative electrode outermost periphery and innermost peripheral portion of the wound electrode plate using a high-capacity negative electrode active material. The separator is prevented from rubbing and breaking due to the expansion and contraction of the material, and an internal short circuit between the positive electrode active material or the positive electrode current collector and the negative electrode active material or the negative electrode current collector can be eliminated, thereby improving the cycle life. As a result, a battery having excellent cycle characteristics can be obtained.

  Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1)
FIG. 1 is a schematic cross-sectional view of the negative electrode according to Embodiment 1 of the present invention. In FIG. 1, a negative electrode 10 of the present invention includes a long negative electrode current collector 6 and a first negative electrode active material 8 formed on the surface of the negative electrode current collector 6 and comprising a first negative electrode active material 8 made of a plurality of columnar particles. The negative electrode active material layer 4 and the second negative electrode active material 9 formed adjacent to the first negative electrode active material layer 4 and having a height that decreases toward the end of the negative electrode current collector 6 in the longitudinal direction. And a second negative electrode active material layer 5 containing. The second negative electrode active material 9 is formed so that the concentration of oxygen contained increases toward the end of the negative electrode current collector 6 in the longitudinal direction. The negative electrode current collector 6 preferably has protrusions as shown in FIG.

  1 is a schematic cross-sectional view of the negative electrode 10 cut along a plane parallel to the longitudinal direction of the negative electrode current collector 6, and the tip direction of the arrow in FIG. 1 is the end portion side in the longitudinal direction. Further, in the direction of the terminal portion opposite to the terminal portion side in the longitudinal direction in FIG. 1, the negative electrode current collector 6, the first negative electrode active material layer 4 and the second negative electrode current collector 6 are also shown in FIG. Although the negative electrode active material layer 5 is formed, it is omitted.

  FIG. 2 is a schematic cross-sectional view of the outer periphery of the electrode plate group for a wound battery using the negative electrode 10 of the present invention described above. In the following drawings, the same reference numerals are used for the same components as in FIG.

  In FIG. 2, a first negative electrode active material layer 4 and a second negative electrode active material layer 5 adjacent thereto are formed on the surface of the negative electrode current collector 6. The second negative electrode active material layer 5 is formed so that its height decreases toward the end portion of the negative electrode current collector 6 in the longitudinal direction. The negative electrode 10 is opposed to the positive electrode active material 1 formed on the positive electrode current collector 2 via the separator 3.

  In FIG. 2, only the outer peripheral portion of the electrode plate group is shown. Similarly, the innermost peripheral portion also includes the first negative electrode active material layer 4 and the inner side of the innermost periphery (in the longitudinal direction of the negative electrode current collector 6). A second negative electrode active material layer 5 including a second negative electrode active material 9 formed so as to decrease in height toward the terminal end side) is formed.

Next, the negative electrode active material will be described. It is known that a negative electrode active material used in a lithium ion battery expands and contracts in volume when inserting and extracting lithium ions. In particular, the oxygen concentration in the silicon oxide and the volume expansion coefficient are closely related. For example, when silicon oxide having a chemical composition represented by SiO _α is used as the negative electrode active material, when the negative electrode active material contains almost no oxygen (α≈0), the negative electrode active material is about 400 by charging. % Volume expansion occurs. When the amount of oxygen atoms relative to silicon atoms in the negative electrode active material is 30%, that is, when α = 0.3, the negative electrode active material undergoes a volume expansion of about 350% by charging. Similarly, when the amount of oxygen atoms is 60%, that is, when α = 0.6, volume expansion of about 280% occurs, and when the amount of oxygen atoms is 100%, that is, α = In the case of 1.0, volume expansion of about 200% occurs.

  Such volume expansion is closely related to the proportion of the volume occupied by the negative electrode active material in the film (hereinafter referred to as film density) when the negative electrode active material formed on the current collector is viewed as one film. . When the density of the negative electrode active material in the in-film direction becomes dense, a space for isotropic expansion cannot be secured in the in-film direction, and thereafter, expansion in the film thickness direction becomes the main and reaches the above-described volume expansion coefficient. However, since the negative electrode active material expands isotropically when the film density is low, the expansion in the film thickness direction of the negative electrode active material can be reduced, and the outermost peripheral portion and innermost portion of the wound electrode plate group can be reduced. In the peripheral portion, the amount of expansion and contraction of the electrode plate can be suppressed.

  With such behavior of the negative electrode active material, the electrode plate group swells to some extent at the outermost peripheral portion of the wound electrode plate group, but because the size is regulated by the case, the electrode plate moves along the inner periphery of the case. extend. Further, in the innermost peripheral portion, the electrode plate group is further deformed to the inner peripheral side. Thus, every time charging / discharging is repeated, the electrode plate repeatedly expands and contracts in the outermost and innermost peripheral portions of the wound electrode plate group. At this time, the separator and the negative electrode active material have different shrinkage rates, so that they rub against each other, and the edge of the negative electrode active material breaks, for example, the separator breaks or breaks. When the separator is broken, the negative electrode active material or the negative electrode current collector and the positive electrode active material or the positive electrode current collector may be internally short-circuited.

  In order to avoid such a situation, in the present invention, the outermost circumferential end and the innermost circumferential end of the negative electrode current collector 6 toward the end in the longitudinal direction, that is, when the negative electrode 10 is a wound electrode plate are used. The second negative electrode active material layer 5 including the second negative electrode active material 9 formed so as to decrease in height and increase in oxygen concentration is adjacent to the first active material layer 4. By providing so, it can suppress that the separator 3 is rubbed by the edge part edge of a negative electrode active material, and fracture | ruptures.

  Furthermore, by using a negative electrode active material using silicon oxide, the amount of expansion and contraction of the electrode plate can be suppressed at the outermost peripheral portion and the innermost peripheral portion of the wound electrode plate group.

When silicon oxide is used as the negative electrode active material, the first negative electrode active material contained in the first negative electrode active material layer has a chemical composition represented by SiO _x (0 ≦ x <1.2), and the second The second negative electrode active material contained in the negative electrode active material layer preferably has a chemical composition represented by SiO _y (1.0 <y ≦ 2.0). When x exceeds 1.2, the thickness of the active material for securing the capacity increases, and problems such as warpage of the negative electrode current collector 6 after film formation occur, which is not preferable. The value of y is 1.0 <y ≦ 2.0, and it is preferable that the value of y increases toward the end of the negative electrode current collector 6 in the longitudinal direction, and y gradually changes toward 2.0. . The wider the region of y = 2.0 of the second negative electrode active material 9, the more preferable is that an insulating film is provided at the outermost peripheral edge of the negative electrode, and an internal short circuit due to fine particles inside the electrode plate can be prevented. .

  Further, as shown in FIG. 3, a third negative electrode active material layer 7 may be further included between the negative electrode current collector 6 and the first negative electrode active material layer 4 and the second negative electrode active material layer 5. By providing the third negative electrode active material layer 7 between the negative electrode current collector 6 and the first negative electrode active material layer 4 and the second negative electrode active material layer 5, the stress applied to the negative electrode current collector 6 is relieved. can do. In addition, the 3rd negative electrode active material layer 7 should just be formed so that the negative electrode collector 6 may be covered. In other words, the third negative electrode active material layer 7 is formed continuously on the surface of the negative electrode current collector 6 so that the negative electrode current collector 6 and the first negative electrode active material 4 do not directly contact each other. A portion where the negative electrode current collector 6 is exposed may be provided as necessary, such as a current collecting lead portion. When the negative electrode active material layer 7 having a substantially uniform thickness is formed on the surface of the negative electrode current collector 6, a vacuum deposition method is suitable.

The third negative electrode active material layer 7 has a chemical composition represented by SiO _Z (1.0 <z <2.0), and z has an effect of suppressing electrode plate expansion while ensuring electrical conductivity. It is an area that appears. Particularly, in the first negative electrode active material, x is 0.3 ≦ x ≦ 0.7, and z is 1.0 ≦ z ≦ 1.6, the stress applied to the negative electrode current collector 6 is relieved, More desirable.

Moreover, it is preferable that x = z at the junction between the third negative electrode active material layer 7 and the first negative electrode active material layer 4. The fact that the chemical composition of the silicon oxide at the joint between the third negative electrode active material layer 7 and the first negative electrode active material layer 4 is identical means that no interface is formed at the joint. When the chemical composition of the silicon oxide at the joint between the third negative electrode active material layer 7 and the first negative electrode active material layer 4 is the same, the chemical composition inside the third negative electrode active material layer 7 is changed. When SiO _z1 , the chemical composition inside the first negative electrode active material layer 4 is SiO _x1, and the chemical composition at the junction is SiO _v , z1>v> x1 and the composition is continuous from z1 to x1. It is preferable that it changes. This is because the expansion of the first negative electrode active material 8 in the vicinity of the third negative electrode active material layer 7 can be further suppressed. As a result, expansion of the negative electrode active material is suppressed, and the amount of expansion and contraction of the electrode plate can be further suppressed at the outermost and innermost peripheral portions of the wound electrode plate group. On the other hand, the first negative electrode active material layer 4 has a lower oxygen concentration than the third negative electrode active material layer 7 having a higher oxygen concentration. As a result, the lithium ion storage capability of the first negative electrode active material layer 4 is increased, so that the negative electrode 10 having a high energy density can be obtained.

  The thickness d of the third negative electrode active material layer 7 is preferably 5 nm ≦ d ≦ 100 nm, more preferably 5 nm ≦ d ≦ 50 nm, from the viewpoints of conductivity, energy density, and expansion coefficient. . If the thickness d of the third electrode active material layer 7 is too thin, the effect of suppressing expansion cannot be obtained sufficiently, and conversely, if it is too thick, sufficient battery energy may not be obtained.

  Further, as shown in FIG. 4, the growth direction of the first negative electrode active material 8 is formed of columnar particle groups inclined by an angle θ with respect to the normal direction D1 of the negative electrode current collector 6, and the second The negative electrode active material 9 is preferably formed of a columnar particle group in which the growth direction is random. The 1st negative electrode active material layer 4 is comprised from the 1st negative electrode active material 8 grown diagonally, and has a space in the inside. The space between the first negative electrode active material 8 is the surface roughness of the negative electrode current collector 6 and the silicon to the negative electrode current collector 6 when the negative electrode 10 is produced using a vacuum deposition method in an oxygen atmosphere. It can be controlled by the incident angle of (Si) vapor. The first negative electrode active material 8 formed from the columnar particle group inclined with respect to the normal direction D1 of the negative electrode current collector 6 can have a low film density, and the first negative electrode active material 8 expands isotropically. The expansion of the negative electrode active material in the film thickness direction can be reduced, and the amount of expansion and contraction of the electrode plate can be further suppressed at the outermost peripheral portion of the wound electrode plate group.

  Further, since the second negative electrode active material 9 is randomly formed, the second negative electrode active material layer 5 has fine particles inside the electrode plate, the negative electrode current collector 6 or the third negative electrode active material layer 7. It is more preferable because it can prevent an internal short circuit in contact with.

  The area (s1) where the first negative electrode active material layer 4 and the third negative electrode active material layer 7 are in contact is the area where the negative electrode current collector 6 and the third negative electrode active material layer 7 are in contact. Smaller than (s2). The active material coverage (S = s1 / s2) is determined by the surface roughness of the negative electrode current collector 6 and the silicon (Si) on the negative electrode current collector 6 when vacuum deposition is performed in an oxygen atmosphere. Depending on the incident angle of the steam, it can be controlled from about 30% to 60%. That is, the first negative electrode active material layer 4 composed of a plurality of columnar first negative electrode active materials 8 is formed of a group of particles inclined with respect to the normal direction D 1 of the negative electrode current collector 6. The coverage S can be measured by observing the polished cross section of the negative electrode 10 by SEM (Scanning Electron Microscope, scanning electron microscope) and measuring the contacted portion.

  Here, the coverage S is that when the polished cross section is observed with an SEM, the length of the uneven portion on the surface of the negative electrode active material layer 7 is A per 100 μm length, and the negative electrode active material particles 8 are formed of the negative electrode active material layer 7. When the length of the part joined to the concavo-convex part was defined as B, B / A was determined and defined as an average value of 400 μm length. When the coverage S is 30% to 60%, a space can be formed between the first negative electrode active materials 8. As a result, since a space for isotropic expansion can be secured in the in-plane direction of the first negative electrode active material layer 4, the expansion of the negative electrode active material is suppressed, and at the outermost peripheral portion of the wound electrode plate group, The amount of expansion and contraction of the plate can be further suppressed. In addition, the length of the concavo-convex portion on the surface of the negative electrode current collector 6 is applied as the length A instead of the length of the concavo-convex portion on the surface of the third negative electrode active material layer 7, and the first negative electrode active Even if the length of the portion where the material 8 is bonded to the uneven portion of the negative electrode current collector 6 is applied, the third negative electrode active material layer 7 is formed so as to follow the surface shape of the negative electrode current collector 6. In that case, there is virtually no problem.

  The negative electrode current collector 6 can be made of a foil such as copper or nickel. From the viewpoints of strength, volumetric efficiency as a battery, and ease of handling, the thickness of the foil is preferably 4 to 30 μm, more preferably 5 to 10 μm. Although the surface of the foil may be smooth, in order to increase the adhesion strength with the first to third negative electrode active material layers 7, an uneven foil having an arithmetic average roughness Ra of about 0.3 to 5.0 μm is used. It is preferable to use it. The arithmetic average roughness Ra is defined in Japanese Industrial Standard (JISB 0601-1994), and can be measured by, for example, a surface roughness meter. The unevenness of the foil also has the effect of forming voids between the columnar particles 8 constituting the negative electrode active material 4. From the viewpoint of securing the adhesive force between the negative electrode current collector 6 and the third negative electrode active material layer 7, Ra = 0.3 to 5.0 μm is preferable.

  The thickness of the entire first negative electrode active material layer 4 is not particularly limited, but is preferably 0.5 μm to 50 μm, particularly 5 μm to 30 μm from the viewpoint of battery energy density, high rate characteristics, productivity, and the like. More preferred. If the first negative electrode active material layer 4 is too thin, sufficient battery energy cannot be obtained, and if the first negative electrode active material layer 4 is too thick, cracks may occur during film formation.

  Note that various methods can be used to measure the oxygen concentration and film thickness in each region. For example, an X-ray photoelectron spectrometer (XPS, ESCA) can be used. In order to measure the oxygen concentration of the negative electrode active material layer 7 located at the interface between the negative electrode current collector 6 and the first negative electrode active material layer 4, in addition to Ar etching, oxygen equivalent to the site to be measured It is also effective to separately form a silicon oxide film for measurement having a concentration on the surface layer.

  Next, an example of a method for manufacturing the negative electrode 10 shown in FIG. 1 will be described with reference to FIGS.

  FIG. 5 is a schematic diagram illustrating an example of a method of forming a third negative electrode active material layer on a current collector. In FIG. 5, the inside of the vacuum chamber 101 is exhausted by an exhaust pump 113. In the vacuum chamber 101, the current collector substrate 100 is installed so that it can be deposited while moving at a constant speed. The evaporation source crucible 105 containing the Si material 106 is irradiated with electrons from the electron gun 107 to melt and evaporate the Si material. The oxygen flow rate control device 112 controls the oxygen flow rate, and a predetermined oxygen amount is introduced into the vacuum chamber 101 from the oxygen nozzle 111. When a predetermined vapor deposition condition is reached, the shutter 104 is opened and film formation is started. The evaporation amount of Si is controlled by the film thickness monitor 108, and Si collector is supplied to the current collector substrate 100 by the Si vapor supplied in an atmosphere containing oxygen and passing through the active material formation region 109 between the fixed masks 102. 3 negative electrode active material layer 7 is formed. The thickness of the third negative electrode active material layer 7 can be changed by the opening length of the active material formation region 109, the amount of Si evaporation, and the moving speed of the current collector substrate 100. The active material formation region 109 is arranged such that Si atoms are incident and deposited on the normal line standing on the traveling current collector substrate 100 including an angle of 0 °. Thus obtained current collector substrate 120 with the third negative electrode active material layer formed thereon is obtained.

  FIG. 6 is a schematic diagram illustrating an example of a method for producing a negative electrode. In FIG. 6, the same components as those in FIG. In FIG. 6, the inside of the vacuum chamber 101 is exhausted by an exhaust pump 113. In the vacuum chamber 101, the current collector 120 with the third negative electrode active material layer 7 formed (hereinafter referred to as the current collector 120) is installed so as to be deposited while moving at a constant speed. Note that a moving device for moving the current collector 120 is omitted. The moving mask 103 has an opening and is installed so as to move at the same speed as the moving speed of the current collector 120. The moving mask 103 is provided with an edge oxygen nozzle 114. The edge oxygen nozzle 114 moves while the moving mask 103 introduces oxygen from the edge oxygen nozzle 115 by controlling the amount of oxygen by the edge oxygen flow rate control device 115. The edge oxygen nozzle 114 may be a flexible SUS pipe that can be expanded and contracted.

  The evaporation crucible 105 containing the vapor deposition material 106 is irradiated with electrons from the electron gun 107 to melt and evaporate the vapor deposition material. The oxygen flow rate control device 112 controls the oxygen flow rate, and a predetermined oxygen amount is introduced into the vacuum chamber 101 from the oxygen nozzle 111. When a predetermined vapor deposition condition is reached, the shutter 104 is opened and film formation is started. The evaporation amount of the vapor deposition material is controlled by the film thickness monitor 108, and the vapor deposition material vapor is supplied in an atmosphere containing oxygen, and the vapor deposition material vapor passes through the active material formation region 109 between the fixed mask 102 and the moving mask 103. The first negative electrode active material layer 4 including a plurality of first negative electrode active materials 8 is formed on the surface of the third negative electrode active material layer 7.

  In the active material formation region 109, the region changes with the movement of the movement mask 103. In the second negative electrode active material layer formation region 110, the movement speed of the movement mask 103 and the current collector 120 is the same, and the movement direction is the same. Since they are identical, they can be formed constant. The size of the second negative electrode active material layer forming region 110 can be changed by the gap between the moving mask 103 and the current collector 120. The evaporation material clusters or evaporation material atoms evaporated from the evaporation crucible 105 directly reach the current collector 120, but in the shadowed portion of the moving mask 103, the evaporation material clusters or evaporation material atoms lose their straightness. ing. Therefore, the deposition rate is very slow, the film is easily oxidized, and a randomly shaped film can be gradually formed thin. Further, the wider the gap between the moving mask 103 and the current collector 120, the clearer the boundary and the smoother the active material edge can be formed, so that the region of the second negative electrode active material layer 5 can be formed wider.

  In the case of manufacturing the negative electrode 10 shown in FIG. 4, the active material formation region 109 is from the direction of an angle θ (0 ° <θ <90 °) with respect to the normal line standing on the traveling current collector 120. The arrangement is such that the vapor deposition material atoms are incident and deposited. Thereby, the first negative electrode active material 8 having a columnar shape with a gap due to the surface unevenness of the negative electrode current collector 6 can be formed to be inclined with respect to the normal direction D 1 of the current collector 120.

In this way, the negative electrode 10 is obtained. In the case where silicon oxide is formed as the negative electrode active material 4, silicon (Si) may be used as the vapor deposition material. In the case where silicon (x = 0 in SiO _x ) is formed, the oxygen flow rate control device 112 is used. The oxygen supply may be stopped.

  In addition, in the case of manufacturing the negative electrode 10 illustrated in FIG. 1, the process of forming the third negative electrode active material layer illustrated in FIG. 5 may be omitted.

  The formation thickness and composition of the first negative electrode active material layer 4 and the first negative electrode active material 8 obtained by the above-described method are the opening width and passage time of the active material formation region 109, and the oxygen flow rate of the oxygen nozzle 111, respectively. Can be controlled. At this time, since the current collector 120 has a constant speed, the deposition speed of the vapor deposition material atoms in the active material forming region 109 can be estimated from a generally known cos rule. Further, the passage time can be appropriately set depending on the position of the fixed mask 102.

  The evaporation crucible 105 is often made of carbon when silicon (Si) is dissolved. The higher the silicon purity of the vapor deposition material 106, the better. Generally, silicon having a purity of 99.99% or more is used. As a method for heating the vapor deposition material 106, an induction heating method, a resistance heating method, a heating method by irradiation with an electron beam, or the like can be used.

  The amount of oxygen in the active material formation region 109 includes the amount of oxygen introduced from the oxygen nozzle 111, the shape of the vacuum chamber 101, the exhaust capacity of the exhaust pump 113, the evaporation rate of the vapor deposition material 106, and the negative electrode active material 4 on the current collector 120. The film forming width and other manufacturing conditions can be changed as appropriate.

  Although the formation method of the 1st negative electrode active material layer 4 and the 1st negative electrode active material 8 will not be specifically limited if the negative electrode 10 of this invention can be obtained, a vapor deposition method, a sputtering method, or CVD method etc. It is preferable to use the dry process. In particular, the vapor deposition method is a highly productive method, and is suitable as a method for continuously and mass-forming the first negative electrode active material layer 4 and the first negative electrode active material 8 on the moving current collector 120. .

  In the manufacturing method described above, as shown in FIG. 6, the negative electrode of the present invention is obtained by using the current collector 120 on which the third negative electrode active material layer 7 has been formed. The formation of the layer 7 may be carried out in the same vacuum layer. Moreover, you may implement continuously in the same apparatus. In this case, the negative electrode in which x = y described above, that is, the negative electrode in which the chemical composition of the silicon oxide at the junction between the third negative electrode active material layer 7 and the first negative electrode active material 4 is the same is used. It can be easily obtained.

The negative electrode 10 obtained by such a method includes a positive electrode containing a commonly used positive electrode active material such as LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , a separator made of a microporous film, etc., and phosphorus hexafluoride A lithium secondary battery can be produced by using lithium acid or the like together with an electrolyte having lithium ion conductivity having a generally known composition in which cyclic carbonates such as ethylene carbonate and propylene carbonate are dissolved.

  Further, the negative electrode of the present invention can be applied to lithium secondary batteries having various shapes such as a cylindrical shape, a flat shape, a coin shape, and a square shape, and the shape of the battery as long as the battery uses a wound electrode plate group. The sealing form is not particularly limited.

  The negative electrode according to the present invention and a battery using the negative electrode use a high-capacity negative electrode active material, and suppress the destruction of the separator at the outermost peripheral portion of the wound electrode plate, which occurs due to the influence of expansion and contraction due to charge and discharge. It is useful as a negative electrode that can be used, and as a battery using the same.

Schematic cross-sectional view of the negative electrode in Embodiment 1 of the present invention Schematic cross-sectional view of a wound battery using a negative electrode according to Embodiment 1 of the present invention Schematic cross-sectional view of another negative electrode in Embodiment 1 of the present invention Schematic cross-sectional view of another negative electrode in Embodiment 1 of the present invention Schematic diagram showing an example of a method of forming a third negative electrode active material layer on the current collector in Embodiment 1 of the present invention Schematic diagram showing an example of a method for producing a negative electrode in Embodiment 1 of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Positive electrode active material 2 Positive electrode collector 3 Separator 4 1st negative electrode active material layer 5 2nd negative electrode active material layer 6 Negative electrode current collector 7 Negative electrode active material layer 8 1st negative electrode active material 9 2nd negative electrode active Substance 10 Negative electrode 101 Vacuum chamber 102 Fixed mask 103 Moving mask 104 Shutter 105 Evaporation source crucible 106 Vapor deposition material 107 Electron gun 108 Film thickness monitor 109 Active material formation region 100 Current collector substrate 110 Second negative electrode active material layer formation region 111 Oxygen Nozzle 112 Oxygen flow control device 113 Exhaust pump 114 Oxygen nozzle for edge 115 Oxygen flow control device for edge 120 Current collector with a third negative electrode active material layer formed

Claims (6)

A negative electrode for a lithium secondary battery comprising a long current collector and a negative electrode active material layer formed on the surface of the current collector,
The negative electrode active material layer is formed on the current collector surface, and includes a first negative electrode active material layer including a first negative electrode active material composed of a plurality of columnar particles;
Adjacent to the first negative electrode active material layer, the height decreases toward the end of the current collector in the longitudinal direction, and the concentration of oxygen contained increases toward the end of the current collector in the longitudinal direction. A second negative electrode active material layer containing a second negative electrode active material made of silicon oxide and formed to be large;
A negative electrode for a lithium secondary battery. The first negative electrode active material included in the first negative electrode active material layer has a chemical composition represented by SiOx (0 ≦ x <1.2),
The second negative electrode active material contained in the second negative electrode active material layer has a chemical composition represented by SiOy (1.0 <y ≦ 2.0);
The negative electrode for a lithium secondary battery according to claim 1. The negative electrode active material layer further includes a third negative electrode active material layer between the current collector and the first negative electrode active material layer and the second negative electrode active material layer,
The third negative electrode active material included in the third negative electrode active material layer has a chemical composition represented by SiOz (1.0 <z <2.0) and has a thickness of 5 nm to 100 nm. thing,
The negative electrode for a lithium secondary battery according to claim 1, wherein the negative electrode is a lithium secondary battery. The first negative electrode active material contained in the first negative electrode active material layer is composed of columnar particles inclined with respect to the normal direction of the current collector,
The second negative electrode active material contained in the second negative electrode active material layer is composed of columnar particles having random growth directions;
The negative electrode for a lithium secondary battery according to any one of claims 1 to 3, wherein: Area ratio (S = s1 / s2) of the area (s1) where the first negative electrode active material layer and the third negative electrode active material layer are in contact with the area (s2) of the third negative electrode active material layer Satisfying 30% ≦ S ≦ 60%,
The negative electrode for a lithium secondary battery according to claim 3. A positive electrode capable of inserting and extracting lithium ions;
A negative electrode for a lithium secondary battery according to any one of claims 1 to 5,
A separator disposed between the positive electrode and the negative electrode for a lithium secondary battery;
An electrolyte having lithium ion conductivity;
Lithium ion secondary battery containing.