JP2007257890A - Positive electrode material for nonaqueous lithium ion battery and battery using this - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positive electrode material for a nonaqueous electrolyte lithium ion battery suppressing elution of Mn even in storage and charge discharge at high temperature, holding high output, and suppressing increase in internal resistance in high output charge discharge. <P>SOLUTION: The positive electrode material uses a lithium nickel manganese oxide having an average valence number of Mn of 3.2 or more in a region of the depth of five times the length of c axis of a crystal from the surface of a primary particles as a positive active material. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a positive electrode material for a non-aqueous electrolyte lithium ion battery using lithium nickel manganese oxide as a positive electrode active material and a non-aqueous electrolyte lithium ion battery using the same.

Currently, lithium ion secondary batteries are commercialized as non-aqueous electrolyte secondary batteries for portable devices such as mobile phones. This non-aqueous electrolyte lithium ion secondary battery needs to be made thinner as the portable device becomes lighter and thinner. Recently, the development of a thin battery using a laminate film as an exterior material has progressed. Laminate type thin batteries using lithium cobalt oxide (LiCoO ₂ ) as material, graphite or carbonaceous material as negative electrode active material, organic solvent or polymer electrolyte in which lithium salt is dissolved in nonaqueous electrolyte are being put into practical use is there.

  Furthermore, in recent years, with the increase in functionality and performance of portable devices, the power consumption of the devices is increasing, and there is an increasing demand for higher capacity for batteries serving as power sources. Thus, development of lithium nickel manganese oxides that can be expected to have a higher capacity than conventional lithium cobalt oxides is progressing.

  Apart from these applications, in order to promote the introduction of electric vehicles (EV), hybrid vehicles (HEV), and fuel cell vehicles (FCV) against the backdrop of the recent increase in environmental protection movements, these motor drive power supplies and hybrid devices Auxiliary power supplies are being developed. Non-aqueous electrolyte lithium ion secondary batteries that can be repeatedly charged and discharged are also used for such applications. In applications where high output and high energy density are required, such as EV, HEV, FCV motor drive, etc., a single large battery cannot be made practically, and an assembled battery constructed by connecting a plurality of batteries in series. Is generally used. It has been proposed to use a laminate-type thin nonaqueous electrolyte lithium ion battery (simply referred to as a thin laminate battery) as one battery constituting such an assembled battery.

  Even in a thin laminated battery for such applications requiring high output and high energy density, the battery outer container is similarly changed to a metal sheet material. Specifically, a metal thin film such as aluminum foil and a resin film that physically protects a metal thin film such as polyethylene terephthalate and heat fusion such as an ionomer so that gas such as water vapor and oxygen is not exchanged inside and outside the container. A laminate sheet in which adhesive resin films are stacked to form a multilayer is used. The outer container of the thin laminated battery has a rectangular shape in plan view and has a predetermined thin shape. A battery is formed by inserting a plate-like positive electrode and negative electrode into an outer container and enclosing a liquid nonaqueous electrolyte.

  Such a thin laminated battery is lightweight because it does not have an individual metal outer container, and even when the pressure inside the container becomes high due to overcharge or the like, and it ruptures, it has less impact than a metal container. , EV, HEV, FCV motor drive, and other applications that require high output and high energy density.

  Furthermore, the thin laminated battery used for such applications as high power and high energy density such as EV, HEV, FCV motor drive, etc. is the power source as in the case of the portable device described above. The demand for higher capacity has become stronger for batteries. In addition, safety is an extremely important evaluation item for automobiles. Therefore, development of lithium nickel manganese oxide that can be expected to have higher capacity and higher safety than conventional lithium cobalt oxide is progressing.

  However, in a lithium ion battery using a positive electrode material containing this lithium nickel manganese oxide as a positive electrode active material, Mn in the positive electrode material becomes a trivalent ion in storage at high temperature (45 ° C. or higher) and cycle durability. There is a problem in that it elutes into the electrolyte and deposits on the negative electrode, reducing the capacity and output of the battery.

In order to stably store and charge / discharge at high temperatures, Patent Document 1 performs element substitution of transition metals.
JP 2005-38629 A

  However, the method described in Patent Document 1 has a problem that the output is decreased for HEV due to a decrease in capacity, an increase in resistance, and the like by replacing the transition metal. Furthermore, there has been a problem in an increase in internal resistance due to a high output charge / discharge cycle for HEV.

  Therefore, the present invention has been focused on the above-mentioned problems of the prior art, and suppresses the elution of Mn even during storage and charge / discharge at a high temperature and maintains high output. It aims at providing the positive electrode material for non-aqueous electrolyte lithium ion batteries which can suppress the raise of resistance, and a battery using the same.

  The inventor makes the average valence of Mn in a region at a certain depth from the surface of the primary particles of lithium nickel manganese oxide used for the positive electrode active material 3.2 or more in storage and charge / discharge. In addition, the present inventors have found that the elution of Mn can be suppressed, the high output can be maintained, and the increase in internal resistance due to the high output cycle charge / discharge can be suppressed.

  That is, the present invention relates to lithium nickel manganese oxidation in which the average valence of Mn is 3.2 or more in a region having a depth five times the c-axis length of the crystal from the primary particle surface (also simply referred to as a near-surface region). The above object can be achieved by a positive electrode material characterized by using a product as a positive electrode active material.

  According to the positive electrode material for a non-aqueous electrolyte lithium ion battery of the present invention, the average valence of Mn in the region 5 times deeper than the c-axis length of the crystal from the primary particle surface of the lithium nickel manganese oxide as the positive electrode active material By making the number 3.2 or more, elution of Mn from the surface to the electrolytic solution can be suppressed. As a measure to make Mn 3.2 or more, excess oxygen is introduced into the surface vicinity region (especially on the surface). Alternatively, the surface vicinity region of the lithium nickel manganese oxide that is the positive electrode active material is terminated with oxygen. Further, Mn in the vicinity of the surface is replaced with +2 valent ions (elements). Oxygen in the vicinity of the surface is replaced with a trivalent ion (element). Furthermore, the valence of Mn can be increased to +4 by deleting Mn in the surface vicinity region. Further, by making the region near the surface of the positive electrode active material oxygen-terminated, the binding force with the carbon-based conductive additive is increased, and an increase in internal resistance due to high output charge / discharge can be suppressed.

  The positive electrode material of the present invention uses, as a positive electrode active material, lithium nickel manganese oxide having an average valence of Mn of 3.2 or more in a region having a depth five times the c-axis length of the crystal from the primary particle surface. It is characterized by.

  The lithium nickel manganese oxide that can be used for the positive electrode material of the present invention is not particularly limited as long as it is used as a positive electrode active material, and conventionally known ones can be used. In these lithium nickel manganese oxides, a region having a depth of 5 times the c-axis length of the crystal from the surface of the primary particles by utilizing the measure for increasing Mn to 3.2 or more as described in the effect of the invention. By making the average valence of Mn at 3.2 or more, an oxide having a surface structure capable of suppressing Mn elution from the oxide surface to the electrolytic solution is obtained.

These lithium nickel manganese oxides have lithium, nickel and manganese as the main components as described above, and the average valence of Mn in the region 5 times deeper than the c-axis length of the crystal from the primary particle surface is 3 It contains a lithium nickel manganese based composite oxide adjusted to 2 or more. As the lithium nickel manganese oxide, for example, the average valence of Mn is 3.2 in a region having a depth five times the c-axis length of the crystal from the primary particle surface of LiNi _0.5 Mn _0.5 O _2. In addition to the above, nickel, a part of manganese is substituted with other elements such as transition metals, for example, LiNi _0.5-x Mn _0.5-y Co _{x + y} O ₂ (0 <x <0.4 0 <y <0.4), the average valence of Mn is 3.2 or more in the region where the depth is 5 times the c-axis length of the crystal from the primary particle surface, or the following general formula In (I),

(Wherein M is at least one selected from alkali metals (excluding lithium), alkaline earth metals (including beryllium and magnesium), transition metals (excluding nickel, manganese and cobalt), and aluminum. A represents an element, A represents at least one element selected from chalcogen elements (excluding oxygen), nitrogen, phosphorus, and halogen elements, and x, y, z, a, b, c, d
0.5 <x ≦ 1.1,
0.3 ≦ y ≦ 0.7,
0.3 ≦ z ≦ 0.7,
0.0 ≦ a ≦ 0.4,
0.0 ≦ b ≦ 0.2,
1.8 ≦ c ≦ 2.4,
0.0 ≦ d ≦ 0.2
Indicates. ) And the like. In the present invention, the lithium nickel manganese composite oxide represented by the formula (I) can be used, but the present invention is not limited to these materials. These lithium nickel manganese oxides, particularly the composition of the general formula (I), can be measured by, for example, ICP (inductively coupled plasma) analysis, atomic absorption method, fluorescent X-ray method, particle analyzer, and mass spectrometry.

  In the present invention, as described above, lithium nickel manganese oxide having an average valence of Mn of 3.2 or more in the region having a depth of 5 times the c-axis length of the crystal from the primary particle surface is used as the positive electrode active material. It is characterized by.

  Preferably, the general formula (I)

(Wherein M is at least one selected from alkali metals (excluding lithium), alkaline earth metals (including beryllium and magnesium), transition metals (excluding nickel, manganese and cobalt), and aluminum. A represents an element, A represents at least one element selected from chalcogen elements (excluding oxygen), nitrogen, phosphorus, and halogen elements, and x, y, z, a, b, c, d
0.5 <x ≦ 1.1,
0.3 ≦ y ≦ 0.7,
0.3 ≦ z ≦ 0.7,
0.0 ≦ a ≦ 0.4,
0.0 ≦ b ≦ 0.2,
1.8 ≦ c ≦ 2.4,
0.0 <= d <= 0.2 is shown. In the lithium nickel manganese oxide when the Li content is 0.95 ≦ x ≦ 1.05, the positive electrode material is obtained by using a lithium nickel manganese oxide represented by The average valence of Mn is 3.2 or more in a region having a depth five times the c-axis length of the crystal from the surface of the next particle.

  M is an element (substitution) for substituting a lithium nickel manganese oxide Li layer (Li site) or a transition metal site of Ni, Mn, Co, an alkali metal (however, excluding lithium), an alkali It represents at least one element selected from earth metals (including beryllium and magnesium), transition metals (excluding nickel, manganese and cobalt), and aluminum.

  Among the above M, alkali metals and alkaline earth metals can be elements (substitutes) that substitute for the Li nickel manganese oxide Li layer (Li site). By substituting a part of the Li layer (site of Li) with the element, the substituted part does not participate in charging / discharging of Li, so that structural change due to charging / discharging can be suppressed. However, these elements may replace some of transition metal sites of nickel (Ni), manganese (Mn), and cobalt (Co) in the lithium nickel manganese oxide.

  The alkali metal refers to lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr), and here, Na, K, excluding Li, Rb, Cs, Fr shall be said. Alkaline earth metal refers to calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra), but here, the one further added with beryllium (Be) and magnesium (Mg). Shall.

Of the M in the above formula, alkaline earth metals (including beryllium and magnesium), transition metals (excluding nickel, manganese and cobalt), and aluminum are Ni, Mn, and Co of lithium nickel manganese oxide. It can become an element (M substitution product) that substitutes the transition metal site. By substituting a part of Ni, Mn, and Co sites of lithium nickel manganese oxide with these elements, it is possible to obtain a substitute having a changed surface composition. In particular, as one of the measures to increase the average valence of Mn in the region (region near the surface) 5 times the c-axis length of the crystal from the primary particle surface of lithium nickel manganese oxide to 3.2 or more. The transition metal sites of Ni, Mn, and Co in the vicinity of the surface, in particular, the Mn site are replaced with elements of +2 metal ions (excluding Ni, Mn, and Co). The transition metal site is replaced with an M-substitution of element of a divalent metal ion (for example, Mg, Zn, etc.) to increase the average valence of Mn to 3.2 or more, so that it can be stored at high temperature and cycle durability. In this case, Mn can be prevented from eluting from the surface into the electrolyte as trivalent ions. As a result, it is possible to suppress the eluted Mn ions from depositing on the negative electrode and reducing the battery capacity and output. From this point of view, the M-substituted product is preferably a +2 valent metal ion element (alkaline earth metal or transition metal), specifically, Mg and / or Zn.
The transition metal refers to an element belonging to Group 3 to 12 of the periodic table. Here, the transition metal site of the lithium nickel manganese oxide of the general formula (I) constitutes the transition metal site of Ni, Mn, and Co. Ni, Mn, and Co are not included.

  Furthermore, A in the above formula is an element (substitute) that substitutes for the oxygen (O) site of the lithium nickel manganese oxide, and is a chalcogen element (group 16 element, excluding oxygen), nitrogen, At least one element selected from phosphorus and halogen elements is shown. By substituting a part of the O site of the lithium nickel manganese oxide with the substitution product A, the surface structure can be stabilized. In particular, as one of the measures to make the average valence of Mn in the region 5 times the c-axis length of the crystal from the primary particle surface of lithium nickel manganese oxide to 3.2 or more, The oxygen site is substituted with an element of a trivalent nonmetallic ion. By substituting oxygen with an A-substitution of -3 valent non-metallic ions (for example, N, P, etc.) to make the average valence of Mn 3.2 or more, in storage at high temperatures and cycle durability, It can suppress that Mn elutes from a surface to electrolyte solution as a trivalent ion. As a result, it is possible to suppress the eluted Mn ions from depositing on the negative electrode and reducing the battery capacity and output. From this point of view, the A-substituted product is preferably a trivalent non-metallic ion element, specifically N and / or P, but is not limited thereto.

  The chalcogen element includes oxygen (O), sulfur (S), selenium (Se), tellurium (Te), and polonium (Po). Here, S, Se, Te, and Po, excluding O, are used. Shall.

  X in the above formula represents the Li content in the lithium nickel manganese oxide, and 0.5 <x ≦ 1.1, preferably 0.66 ≦ x ≦ 1.0. When the Li content x exceeds 1.1, it is easy to form lithium oxide in the first place, it is difficult to synthesize, the crystal structure becomes unstable, or the battery capacity of a lithium secondary battery using this decreases. There is a risk of inviting. Further, the lower limit is not particularly limited, and it is sufficient that Li is contained as an essential component. However, when the Li content x is less than 0.5, in addition to the decrease in capacity as a battery, Li This is undesirable because it leads to a decrease in the diffusion path.

  Y in the above formula indicates the Ni content in the lithium nickel manganese oxide, and 0.3 ≦ y ≦ 0.7, preferably 0.33 ≦ y ≦ 0.67. When the Ni content y is less than 0.3, there is a risk of lowering the capacity, the crystal structure becomes unstable, the internal resistance increases due to high output charge / discharge, and there is a demand for higher capacity. It may be difficult to satisfy the above sufficiently. In addition, when the Ni content y exceeds 0.7, the composition is close to that of lithium nickelate, so that the synthesis is difficult and the thermal stability is lowered. It may be difficult to suppress the internal resistance due to the high output charge / discharge.

  Z in the above formula represents the Mn content in the lithium nickel manganese oxide, and 0.3 ≦ z ≦ 0.7, preferably 0.33 ≦ z ≦ 0.55. When the Mn content z is less than 0.3, the thermal stability is lowered and becomes unstable due to a temperature rise. Further, when the Mn content z exceeds 0.7, there is a risk of causing elution of Mn in addition to a decrease in capacity.

  A in the above formula represents the Co content in the lithium nickel manganese oxide, and 0.0 ≦ a ≦ 0.4, preferably 0.1 ≦ a ≦ 0.35. By including Co in the lithium nickel manganese oxide, capacity deterioration can be suppressed. The lower limit of the Co content a is not particularly specified, but when the Co content a exceeds 0.4, the thermal stability is deteriorated as the raw material cost increases.

  B in the above formula represents an alkali metal (excluding lithium), an alkaline earth metal (including beryllium and magnesium), a transition metal (excluding nickel, manganese and cobalt) in the lithium nickel manganese oxide, The content of the substitution product M made of aluminum is shown, and 0 ≦ b ≦ 0.2, preferably 0.01 ≦ b ≦ 0.1. By including the substitution product M in the lithium nickel manganese oxide, capacity deterioration can be suppressed. When the content b of the substitution product M exceeds 0.2, the battery capacity and the output are reduced. Moreover, since the substitution product M is an optional component and does not need to be contained in particular, the lower limit is not particularly limited. When the substitution product M is included, it is desirable that the substitution product M is substituted to such an extent that the effect of the substitution product M can be effectively exhibited. From this point of view, the content b of the substitution product M is desirably 0.01 or more.

  C in the above formula represents the content of oxygen in which the substitution product A in the lithium nickel manganese oxide is in an unsubstituted state, and 1.8 ≦ c ≦ 2.4, preferably 2.0 ≦ c ≦ 2.2. When the oxygen content c is less than 1.8, the structure is not stable because the number of oxygen is small. On the other hand, when the oxygen content c exceeds 2.4, the oxidation number of the transition metal becomes too high and is thermally unstable.

  D in the above formula represents the content of the substitution product A in the lithium nickel manganese oxide, and 0 ≦ d ≦ 0.2, preferably 0.05 ≦ d ≦ 0.1. In particular, by introducing the substitution A of -3 valent ions in the range of the above content d into the oxygen site in the vicinity of the surface of the lithium nickel manganese oxide, the average valence of Mn in the vicinity of the surface is 3.2. It can be effectively used as one of the measures to increase the price. Thereby, Mn elution from the surface to the electrolytic solution can be suppressed. Moreover, a high output can be maintained and an increase in internal resistance due to a high output cycle charge / discharge can be suppressed. When the content d of the substitution product A exceeds 0.2, the structure becomes unstable, so that synthesis is difficult. Moreover, since the substitute A is an arbitrary component and does not need to contain in particular, a minimum in particular is not restrict | limited. When the substitution product A is included, it is desirable that the substitution product A is substituted to such an extent that the above-described effects of the substitution product A can be effectively exhibited. From this point of view, the content d of the substitution product A desirably exceeds 0.03, more preferably 0.05 or more (see Examples 15 to 20 and Comparative Examples 5 to 6).

  In the present invention, the lithium nickel manganese oxide represented by the above general formula (I) is preferably one in which the entire primary particles are represented by the above general formula (I). However, the composition in the region (surface vicinity region) having a depth five times the c-axis length of the crystal from the primary particle surface may be represented by the above general formula (I). As described above, the surface treatment is performed so that the valence of Mn in the vicinity of the surface of the lithium nickel manganese oxide can be increased. This is because it is included in the range defined by the formula (I). In addition, confirmation of the composition of the surface vicinity area | region after surface treatment can be confirmed by TOF-MASS (time-of-flight mass spectrometry) and TOF-SIMS (time-of-flight secondary ion mass spectrometry), for example. Moreover, the confirmation of the composition of the core part of the lithium nickel manganese oxide particles, that is, the part deeper than the surface vicinity region can be confirmed by, for example, the size of the low angle side peak of the X-ray diffraction pattern.

  Furthermore, in the present invention, excess oxygen is introduced from the surface of the primary particles of the lithium nickel manganese oxide into a region having a depth five times the c-axis length of the crystal, that is, in the general formula (I), It is desirable that ≧ 2-d. This is because the surface of the positive electrode active material can be terminated with oxygen by introducing excess oxygen onto the surface of the lithium nickel manganese oxide. As a result, the average valence of Mn in the region 5 times deeper than the c-axis length of the crystal from the primary particle surface of the lithium nickel manganese oxide can be increased to 3.2 or more, and from the surface to the electrolytic solution. Mn elution can be suppressed. In addition, the surface of the positive electrode active material is oxygen-terminated, so that the binding force with the carbon-based conductive additive is strengthened, and the increase in internal resistance due to high output charge / discharge can be further suppressed.

  From the above points, in the present invention, it is desirable that the primary particle surface of the lithium nickel manganese oxide is oxygen-terminated at a rate of 40% to 100%, preferably 60% to 100%. When the primary particle surface is oxygen-terminated at a ratio of 40% or more and 100% or less, the stability of the transition metal is increased, which is excellent in that the life can be extended.

As described in the examples, the oxygen termination rate can be measured after surface treatment (annealing) of lithium nickel manganese oxide after film formation to increase the valence of Mn in the vicinity of the surface. it can. For example, existing lithium nickel manganese oxide powder not subjected to surface treatment obtained according to the production method as shown in Comparative Example 1 is formed into a cylindrical pellet having an appropriate size (for example, a diameter of 20 mm and a thickness of 5 mm). Mold. The pellet is sintered at 500 to 1000 ° C. in an oxygen atmosphere for 1 to 100 hours. Using the pellet as a target, a film is formed on a conductive substrate (for example, an SrTiO ₃ (100) substrate) by using, for example, a pulse laser deposition (PLD) method. The film forming conditions may be a temperature of room temperature to 700 ° C., an oxygen partial pressure of 0.01 to 10 mmHg, and a range of 0.01 to 10 hours. If the film thickness to be produced is usually about 2 to 100 nm, sufficient evaluation is possible. Thin film lithium nickel manganese oxide (positive electrode active material) by annealing for 1 to 100 hours at a partial pressure of oxygen of 0.2 to 10 atm and 300 to 1000 ° C. as surface treatment (for example, annealing treatment) after film formation (For details, refer to Examples described later). Thus, the surface-treated thin-film lithium nickel manganese oxide (positive electrode active material) thus obtained has an oxygen-terminated area occupying an area of 10 × 10 nm ² according to the method for measuring the oxygen termination rate shown in the Examples. And the oxygen termination rate (%) can be calculated (for details, refer to the section “Method for measuring oxygen termination rate” defined in the Examples). However, such a film forming method is not limited to the pulse laser deposition method (PLD) described in the embodiment, and a chemical vapor deposition method (CVD), PVD, sputtering method, or the like can be used. Further, MgO, LaSrGaO, or the like can be used as the substrate. As for the surface treatment, in addition to an annealing treatment in an atmosphere having an oxygen partial pressure of 0.1 atm (atm) or higher, for example, an annealing treatment in an atmosphere higher than 2 atm of oxygen, an electrolytic oxidation treatment, and an annealing using ozone. It can be performed using processing.

  Further, in the present invention, in the region having a depth of 5 times the c-axis length of the crystal from the primary particle surface of the lithium nickel manganese oxide, a depth of 5 times the c-axis length of the crystal from the primary particle surface. In this region, the transition metal site occupancy ratio of the transition metal site is 90% to 98%, preferably 92% to 96%. The transition metal site here refers to a Ni, Mn, Co transition metal site of the lithium nickel manganese oxide, particularly preferably a Mn site. In addition to Ni, Mn, and Co, the transition metal at this transition metal site may include M in the general formula (I) that can be introduced into the transition metal site (limited to the transition metal). Mn is preferable. By adjusting (controlling) the site occupancy rate of the transition metal (Mn) at the transition metal site (Mn site) within the above range, the average valence of Mn in the vicinity of the surface is set to 3.2 or more. It can be used effectively as one. In other words, Mn is lost from the primary particle surface in a region having a depth of 5 times the c-axis length of the crystal, that is, the Mn site occupancy of the Mn site is lower than 100% in the region near the surface. Also, the valence of Mn (partial) in the vicinity of the surface can be increased to +4 by making the defect to be 98%. Thereby, Mn elution from the surface to the electrolytic solution can be suppressed. Moreover, a high output can be maintained and an increase in internal resistance due to a high output cycle charge / discharge can be suppressed (see the comparison between Examples 21 to 22 and Comparative Example 7).

  The transition metal site occupancy ratio (for example, the Mn site occupancy ratio of the Mn site) in the region having a depth five times the c-axis length of the crystal from the primary particle surface is the crystal from the primary particle surface. It can be calculated by a method such as thin film X-ray analysis or RHEED from the composition of the region having a depth of 5 times the c-axis length (see Table 8).

  Furthermore, in the present invention, 1.8 ≦ (cd) / (y + z + a + b) ≦ 2.4 in a region having a depth five times the c-axis length of the crystal from the primary particle surface of the lithium nickel manganese oxide. Preferably, 2 ≦ (cd) / (y + z + a + b) ≦ 2.2. When the oxygen content (cd) / Ni + Mn + Co + M content (y + z + a + b) is 1.8 or more in a region having a depth of 5 times the c-axis length of the crystal from the surface of the next particle, the number of oxygen atoms is sufficient. Therefore, it is structurally stable, and if it is 2.4 or less, the oxidation number of the transition metal does not become too high, and it is excellent in that the thermal stability is maintained.

  In the present invention, the lithium nickel manganese oxide represented by the general formula (I) described above represents the state of the positive electrode active material before initial charging.

  In the present invention, in the lithium nickel manganese oxide represented by the general formula (I) when the Li content is 0.5 <x ≦ 1.1, particularly 0.95 ≦ x ≦ 1.05, 1 The average valence of Mn is 3.2 or more in a region having a depth five times the c-axis length of the crystal from the surface of the next particle. This can effectively prevent Mn from being ionized and eluted by covering the entire surface with Mn having a higher valence as Mn eluted as +3 valent ions. In particular, by using Mn having a higher valence in the vicinity of the surface, it is possible to effectively block elution of Mn inside than this. Therefore, in the present invention, it is sufficient that the average valence of Mn is controlled to be 3.2 or more in the region from at least the surface of the primary particle to the depth of 5 times the c-axis length of the crystal. The Mn valence of the deeper part is not particularly limited. Therefore, if the Mn valence in the inside (deeper part of the particle) is 3.2 or more than the depth of 5 times the c-axis length of the crystal from the primary particle surface, it is naturally lower than 3.2. The elution can be suppressed, and the effects of the present invention can be effectively expressed. By satisfying such requirements, it is possible to suppress the dissolution of Mn in the lithium nickel manganese oxide as a trivalent ion into the electrolyte during storage at high temperatures (45 ° C. or higher) and cycle durability. As a measure for increasing Mn to 3.2 or more, excessive oxygen is introduced onto the surface to terminate the surface with oxygen. Further, Mn in the vicinity of the surface is replaced with +2 valent ions (elements). Oxygen in the vicinity of the surface is replaced with a trivalent ion (element). Although the valence of Mn can be increased to +4 by depleting Mn, it is not limited thereto. On the other hand, when the average valence of Mn is less than 3.2 in the region 5 times deeper than the c-axis length of the crystal from the primary particle surface, the surface of the positive electrode active material can be used for storage at high temperatures and cycle durability. It becomes difficult to suppress Mn from eluting into the electrolyte as trivalent ions. As a result, the internal resistance due to high output charge / discharge also increases (refer to the comparison of the resistance ratios 1 to 3 and the elution amount of Mn between the examples and comparative examples in each table).

  Here, “when the Li content is 0.95 ≦ x ≦ 1.05” means that the Li content is reduced to 0 by adjusting the amount of lithium atoms introduced into the surface layer as necessary. .95 ≦ x ≦ 1.05. It should be noted that the Li content x of the lithium nickel manganese oxide represented by the general formula (I) in the state before charge / discharge obtained in each example described later is already 0.95. This is because it is not necessary to make the above adjustment in such a case because it is in the range of ≦ x ≦ 1.05. In such a case, the average value of Mn in the region 5 times deeper than the c-axis length of the crystal from the primary particle surface with respect to the lithium nickel manganese oxide represented by the general formula (I) in the state before charge and discharge as it is. Valence can be measured. However, in the state before charge / discharge, the Li content x of the lithium nickel manganese oxide represented by the general formula (I) is not necessarily in the range of 0.95 ≦ x ≦ 1.05. As defined in (I), 0.5 <x ≦ 1.1, preferably 0.66 ≦ x ≦ 1.0 may be satisfied.

  In the present invention, when the Li content x is in the above range, the average valence of Mn in the region 5 times the c-axis length of the crystal from the primary particle surface of the lithium nickel manganese oxide is 3.2. As described above, it is preferably 3.3 or more. In other words, it can be said that the entire primary particle surface can be covered with Mn having a high valence. That is, by covering only a part of the particle surface with Mn having a high valence, elution of Mn from the part can be suppressed, so that a certain effect can be obtained. However, the elution of Mn cannot be effectively suppressed with respect to the surface portion not covered with Mn having a high valence. As a result of the study by the present inventors, when the average valence of Mn in the surface vicinity region is 3.2 or more, the elution suppressing effect of Mn becomes uniform (almost constant value. See Tables 2 to 8) Therefore, it is considered that the entire primary particle surface can be covered with Mn having a high valence at this point.

  Here, the composition of the region (surface vicinity region) having a depth five times the c-axis length of the crystal from the primary particle surface of lithium nickel manganese oxide is, for example, ICP (inductive ion plasma) as a method for quantifying metal elements. Method), nonmetals, and metal elements can be determined using TOF-MASS (time-of-flight mass spectrometry), TOF-SIMS (time-of-flight secondary ion mass spectrometry), or the like. From the composition of the region near the surface thus obtained, the valence of Mn can be obtained based on the principle of electric neutrality. Here, Table 1 shows an example of the valence of each element represented by the general formula (I) (for the transition element of M element, the first transition element (3d transition element) is exemplified).

  The alkali in the above table represents an alkali metal element excluding Li. The earth represents an alkaline earth metal element including Be and Mg. X represents a halogen element. Chalcogen represents a chalcogen element excluding O. W represents the valence of Mn.

Accordingly, for example, the composition in the vicinity of the surface of the lithium nickel manganese oxide of Example 1 described later; LiNi _0.4 Co _0.3 Mn _0.3 O _2.06 is taken as an example and obtained as follows. be able to.

W = − (1 × 1 + 0.4 × 3 + 0.3 × 3 + 2.06 × (−2)) / 0.3
W = 3.4
The crystal structure (symmetry of the crystal space group) in the lithium nickel manganese oxide represented by the general formula (I) when the Li content is in the above range is not particularly limited, but will be described later. R3-m is desirable as shown in the examples. Such crystal structure (symmetry of crystal space group) can be confirmed by, for example, a powder X-ray diffractometer (powder XRD) or the like.

In the present invention, the positive electrode active material is characterized by using the above-described lithium nickel manganese oxide that can be expected to have high capacity and high safety. The other positive electrode active material which can be used within the range which does not impair this may be included. As such another positive electrode active material, a positive electrode active material used in a conventionally known non-aqueous electrolyte lithium ion battery can be used. Specifically, other positive electrode active materials may optionally be contained, and conventionally known materials can be used. Specifically, a composite oxide of lithium and transition metal (lithium-transition metal composite oxide) can be preferably used. For example, Li · Mn based composite oxides such as LiMn ₂ O ₄ , Li · Co based composite oxides such as LiCoO ₂ , Li · Cr based composite oxides such as Li ₂ Cr ₂ O ₇ and Li ₂ CrO _4, etc. Li / Fe-based composite oxides such as LiFeO ₂ and those obtained by substituting some of these transition metals with other elements can be used in combination. However, it is limited to these materials. It is not something. Although these lithium-transition metal composite oxides are not as good as lithium nickel manganese oxide in terms of capacity increase, they are excellent in reactivity and cycle durability and are low-cost materials like lithium nickel manganese oxide. Therefore, a battery having excellent output characteristics can be formed by using these materials for the electrodes. In addition to these, transition metal and lithium phosphate compounds and sulfuric acid compounds such as LiFePO ₄ ; transition metal oxides and sulfides such as V ₂ O ₅ , MnO ₂ , TiS ₂ , MoS ₂ , and MoO ₃ ; PbO ₂ , AgO, NiOOH, etc. can be used together.

  The average particle diameter of the lithium nickel manganese oxide particles of the positive electrode active material depends on the production method, but from the viewpoint of increasing the capacity, reactivity, and cycle durability of the lithium nickel manganese oxide, which is the positive electrode active material. Is desirably in the range of 0.1 to 20 μm, but is not necessarily limited to the above range in the present invention. In addition, when the lithium nickel manganese oxide is secondary particles, it can be said that the average particle size of the primary particles constituting the secondary particles is preferably in the range of 0.01 to 5 μm. Then, it is not necessarily limited to the above range. However, it is needless to say that the lithium nickel manganese oxide does not have to be secondary particles formed by aggregation, agglomeration or the like, depending on the production method. The particle size of the lithium nickel manganese oxide particles and the particle size of the primary particles can be measured, for example, by observation with a scanning electron microscope (SEM) or transmission electron microscope (TEM).

  Next, the following (1) to (4), which are methods for increasing the Mn in the region near the surface of the lithium nickel manganese oxide to 3.2 or more, will be described below.

(1) Method of introducing excess oxygen into the region near the surface of lithium nickel manganese oxide As a method of introducing excess oxygen into the region near the surface of lithium nickel manganese oxide, (i) high oxygen in an atmosphere of 1 atmosphere or more of oxygen Oxygen pressure annealing treatment (ii) Annealing treatment using ozone can be used. However, the method for introducing excess oxygen is not limited to these methods.

  The high oxygen pressure annealing treatment (i) is not particularly limited as long as desired excess oxygen can be introduced. For example, excess oxygen may be introduced into the surface of the lithium nickel manganese oxide by performing a high oxygen pressure annealing treatment at 300 ° C. to 500 ° C. in an atmosphere higher than 2 atmospheres, preferably in an atmosphere higher than 2 atmospheres and 20 atmospheres or lower. it can.

  The ozone annealing treatment (ii) is not particularly limited as long as desired excess oxygen can be introduced. For example, excess oxygen can be introduced into the surface of the lithium nickel manganese oxide by performing an annealing process using ozone at 300 ° C. to 500 ° C. Note that ozone annealing can be performed using a mixed gas of oxygen and ozone, air, and a mixed gas of ozone. The pressure at the time of ozone annealing may be the same as that of the high oxygen annealing. Further, the ozone concentration in the case of using a mixed gas is not particularly limited as long as desired excess oxygen can be introduced.

  In any of the cases (i) to (ii) of the above (1), the lithium nickel manganese oxide before introducing excess oxygen to the surface (near region) is the same as the manufacturing method of (3) described later. Can be produced. That is, it is prepared by mixing a compound containing a raw material before coprecipitation (a raw material of lithium nickel manganese oxide that is a positive electrode active material), coprecipitating, pyrolyzing, and firing (including annealing). Can do.

(2) A method in which the surface (near region) of the primary particle of lithium nickel manganese oxide is oxygen-terminated The method of having the surface (near region) of the lithium nickel manganese oxide is oxygen-terminated is not particularly limited. However, it can be carried out (confirmed) by the same method as the method for introducing excess oxygen. In the present invention, in addition to the method for introducing excess oxygen, for example, the oxygen termination can be formed by using the method used in the examples. That is, a thin film of lithium nickel manganese oxide is formed using an electron-doped SrTiO ₃ (100) substrate using a laser pulsed deposition method (PLD). After that, oxygen termination is formed by oxygen annealing, and the oxygen termination rate before annealing and after annealing by the diffraction pattern of in situ STM (in-situ observation device using scanning tunneling microscope) and RHEED (reflection high-energy electron diffraction) Was measured. The film forming method is not limited to PLD, and chemical vapor deposition (chemical vapor deposition method; CVD), physical vapor deposition method (physical vapor deposition method; PVD), sputtering, and the like are also possible. . Also, the substrate is not limited to the electron-doped SrTiO ₃ (100) substrate, and for example, MgO, LaSrGaO, or the like can be used. Furthermore, the oxygen annealing conditions after the film formation are not particularly limited as long as a desired oxygen termination can be formed on the surface (near region). For example, at 300 to 1000 ° C., by performing oxygen annealing in an atmosphere having an oxygen partial pressure of 0.05 atmospheres or more, preferably 0.1 atmospheres or more, more preferably 0.1 to 10 atmospheres, lithium nickel manganese oxide A desired oxygen termination can be formed on the surface (near region). By making the surface of the lithium nickel manganese oxide (near region) an oxygen termination, the binding force with the carbon-based conductive additive is strengthened and high output charge is achieved. An increase in internal resistance due to discharge can be suppressed.

  In the case of (2), the lithium nickel manganese oxide powder before the surface (near region) is terminated with oxygen can be produced in the same manner as in the production method (3) described later. That is, it is prepared by mixing a compound containing a raw material before coprecipitation (a raw material of lithium nickel manganese oxide that is a positive electrode active material), coprecipitating, pyrolyzing, and firing (including annealing). Can do.

(3) Method of substituting Mn in the region near the surface of the lithium nickel manganese oxide with +2 valent ions (element M) As a method for substituting Mn in the region near the surface with +2 valent ions (mainly transition metal element M), There is no particular limitation. For example, when lithium nickel manganese oxide is produced by the coprecipitation method, a compound containing element M such as Mg or Zn is mixed into the raw material before coprecipitation (raw material of lithium nickel manganese oxide, which is a positive electrode active material). , Coprecipitation, thermal decomposition, and firing (including annealing), manganese on the surface of the lithium nickel manganese oxide can be replaced with a substitution element. After substitution, confirmation of the surface composition can be confirmed by TOF-MASS and TOF-SIMS. Moreover, about the Li layer (composition of the core part of particle | grains) which does not have a substitution element, it can confirm by the magnitude | size of the low angle side peak of a X-ray diffraction pattern.

(4) Method of substituting oxygen in the region near the surface of the lithium nickel manganese oxide with a trivalent ion (element A) Method of substituting oxygen in the region near the surface with a trivalent ion (element A) such as nitrogen or phosphorus There is no particular limitation on the above. For example, in the method of (3) above, by using a manganese nitrogen compound or a manganese phosphorus compound as a raw material (a part) before coprecipitation, a trivalent ion (element A) such as nitrogen or phosphorus is introduced into the oxygen site. can do. As a method for quantifying nitrogen and phosphorus on the surface, TOF-MASS, TOF-SIMS and the like can be used.

(5) Method for missing Mn in the vicinity of the surface of the lithium nickel manganese oxide The method for missing Mn in the vicinity of the surface is not particularly limited. For example, in the above methods (3) and (4), by adjusting the mixing amount of the compound containing Mn in the raw material before coprecipitation (raw material of lithium nickel manganese oxide as the positive electrode active material), lithium nickel Manganese on the surface of the manganese oxide can be lost. The valence of Mn can be increased to +4 by depleting Mn.

  Especially as a manufacturing method of lithium nickel manganese oxide used in said (1)-(5) (and the substitution method of M elements, such as Zn and Mg, and A elements, such as N and P, made at the time of manufacture), it is especially restricted. However, conventionally known techniques for producing various complex oxides can be applied. For example, the raw material of lithium nickel manganese oxide as a raw material before coprecipitation is mixed with a compound containing an M element such as Zn or Mg and an A element such as N or P, if necessary, and coprecipitated, By thermal decomposition and firing (including annealing), Mn in the region near the surface of the lithium nickel manganese oxide can be increased to 3.2 or more. Specifically, lithium hydroxide hydrate as a raw material before coprecipitation, Mn, Co, and optionally nickel hydroxide containing M element such as Zn or Mg, N or P as necessary Manganese nitrate, manganese phosphate or the like is mixed as a compound containing an A element such as coprecipitate, thermally decomposed, and fired (including annealing). As a result, Mn in the region near the surface of the lithium nickel manganese oxide can be replaced with M element such as Zn or Mg, and a part of oxygen can be replaced with nitrogen or phosphorus, and Mn in the region near the surface can be reduced to 3.2. It can be more than the value. However, the manufacturing method is not limited at all.

  As the compound containing M element such as Zn and Mg, in addition to Ni and Mn, a hydroxide further containing M element such as Zn and Mg in the primary particles, for example, Co, Mn and Mg. It is desirable to use nickel hydroxide containing appropriate amounts; nickel hydroxide containing appropriate amounts of Co, Mn and Zn. This is because synthesis in an aqueous solution system such as a coprecipitation method becomes easy.

  Moreover, as a compound containing A elements, such as said N and P, manganese nitrate, manganese phosphate, etc. can be used, for example. Thereby, oxygen can be substituted with an A element such as nitrogen or phosphorus, and good conductivity can be maintained. However, the present invention is not limited to these.

  If necessary, the above raw materials are mixed with a compound containing M element such as Zn or Mg and A element such as N or P (mixing process) and co-precipitated (co-precipitation process), followed by thermal decomposition. Specific examples of the processing (process) conditions until the heat treatment (thermal decomposition process) and the firing (firing process; including annealing) are shown in the respective examples described later. More general conditions will be briefly described below, but the present invention is not limited to these ranges.

(Mixing / coprecipitation process)
The raw material lithium hydroxide hydrate and manganese, cobalt, and optionally nickel hydroxide containing the element M shown in the general formula (I) are purified so as to have a desired lithium nickel manganese oxide composition. Dissolve in water. In this process, if necessary, a compound containing the element A represented by the general formula (I) such as nitrogen or phosphorus is mixed so that the composition of the desired lithium nickel manganese oxide is obtained.

(Co-precipitation step) (Since co-precipitation starts from the mixing step, this is the procedure (form).)
Here, the precipitate formed after the start of mixing is allowed to stand for 0.1 to 24 hours and matured, and then filtered and washed with pure water, ethanol or the like to obtain a coprecipitate.

(Pyrolysis process)
The coprecipitate is heated to a temperature of 120 to 300 ° C. at a temperature rising rate of 0.1 to 20 ° C./min, and in the temperature range, preferably a constant temperature within the temperature range, in the air or in an inert atmosphere Pyrolysis under 1-24 hours. The porosity of the secondary particles can be controlled by the temperature of the thermal decomposition.

(Baking process)
The temperature is raised from the temperature of the thermal decomposition to a range of 500 to 1000 ° C. at a rate of temperature increase of 0.1 to 20 ° C./min, and the temperature range, preferably a constant temperature within the temperature range, in an oxygen atmosphere, Baking for 1 to 100 hours while homogenizing. After firing, the temperature is lowered from the firing temperature to a range of 300 to 700 ° C. at a rate of temperature reduction of 0.1 to 20 ° C./min, and in that temperature range, preferably a constant temperature within the temperature range, in the air or in an oxygen atmosphere The desired lithium nickel manganese oxide can be produced by annealing for 0 to 100 hours. In this step, lithium nickel manganese oxide particles grow.

  In the process up to here, by mixing a compound containing M element such as Zn or Mg and A element such as N or P, or adjusting the amount of Mn mixed, and performing the desired annealing treatment, The valence of Mn can be 3.2 or more (see (3) to (5) above). However, as in the above (1) and (2), excess oxygen may be introduced by oxygen annealing after the high oxygen pressure (in an atmosphere higher than 2 atmospheres) annealing or after film formation in the annealing. The valence of Mn in the surface vicinity region can be 3.2 or more. In this case, a compound containing M element or A element may not be mixed.

  ICP (inductive ion plasma method) as a quantitative method for metal elements, TOF-MASS (time-of-flight mass spectrometry), TOF-SIMS (time-of-flight secondary ion mass spectrometry) as non-metallic and metal element quantitative methods ) Etc. can be used.

  Other constituent components that can be used in the positive electrode material of the present invention include a conductive auxiliary agent for increasing electronic conductivity, a binder, an electrolyte supporting salt (lithium salt) for increasing ionic conductivity, a polymer gel or a solid. Electrolytes (host polymers, electrolytes, etc.) can be included. In the case of using a polymer gel electrolyte for the battery electrolyte layer, it is sufficient that a conventionally known binder, a conductive auxiliary agent for enhancing electronic conductivity, etc. are contained. Lithium salt or the like may not be contained. Even when a solution electrolyte is used for the battery electrolyte layer, the positive electrode material may not contain a host polymer, an electrolytic solution, a lithium salt, or the like as a raw material of the polymer electrolyte.

  Examples of the conductive aid include acetylene black, carbon black, graphite, and vapor grown carbon fiber (VGCF). However, it is not necessarily limited to these.

  As the binder, polyvinylidene fluoride (PVDF), SBR, polyimide, or the like can be used. However, it is not necessarily limited to these.

  The polymer gel electrolyte includes a solid polymer electrolyte having ion conductivity and an electrolyte used in a conventionally known non-aqueous electrolyte lithium ion battery, and further has lithium ion conductivity. A structure in which a similar electrolyte solution is held in a non-polymeric skeleton is also included.

Here, the electrolytic solution (electrolyte supporting salt and plasticizer) contained in the polymer gel electrolyte is not particularly limited, and various conventionally known electrolytic solutions can be appropriately used. For example, inorganic acid anion salts such as LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiTaF ₆ , LiAlCl ₄ , Li ₂ B ₁₀ Cl ₁₀ , LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, Li (C 2 _F 5 _{SO 2)} selected from organic acid anion salts such as 2 _N, wherein at least one lithium salt (electrolyte support salt), propylene carbonate, cyclic carbonates such as ethylene carbonate; dimethyl carbonate Chain carbonates such as methyl ethyl carbonate and diethyl carbonate; ethers such as tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-dibutoxyethane; γ-butyrolactone, etc. Lactones; Nitto such as acetonitrile Lyls; Esters such as methyl propionate; Amides such as dimethylformamide; Plasticizers such as aprotic solvents (organic) mixed with at least one selected from methyl acetate and methyl formate Those using a solvent) can be used. However, it is not necessarily limited to these.

  Examples of the solid polymer electrolyte having ion conductivity include known solid polymer electrolytes such as polyethylene oxide (PEO), polypropylene oxide (PPO), and copolymers thereof.

  For example, polyvinylidene fluoride (PVDF), polyvinyl chloride (PVC), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), etc. are used as the polymer having no lithium ion conductivity used for the polymer gel electrolyte. it can. However, it is not necessarily limited to these. Note that PAN, PMMA, etc. are in a class that has almost no ionic conductivity, and therefore can be a polymer having the above ionic conductivity, but here, they are used for a polymer gel electrolyte. This is exemplified as a polymer having no lithium ion conductivity.

As an electrolyte support salt to increase the ionic conductivity, for _{example, LiPF 6, LiBF 4, LiClO} 4, LiAsF 6, LiTaF 6, LiAlCl 4, Li 2 B 10 Cl 10 inorganic acid anion salts such as, Li ( An organic acid anion salt such as CF ₃ SO ₂ ) ₂ N, Li (C ₂ F ₅ SO ₂ ) ₂ N, or a mixture thereof can be used. However, it is not necessarily limited to these.

  The ratio (mass ratio) between the host polymer and the electrolytic solution in the polymer gel electrolyte may be determined according to the purpose of use, but is in the range of 2:98 to 90:10. That is, in the present invention, particularly from the viewpoint of suppressing the decomposition of the electrolytic solution due to the release of radical oxygen from the LiNi oxide, among nonaqueous electrolytes, a solution electrolyte or a polymer gel electrolyte that uses an electrolytic solution is particularly used. It works effectively against. Therefore, regarding the ratio (mass ratio) between the host polymer and the electrolytic solution in the polymer gel electrolyte, it is not necessary to limit the amount of the electrolytic solution for the purpose of preventing the swelling of the battery due to the decomposition of the electrolytic solution, and priority is given to the battery characteristics. It is something that can be done.

  Next, the positive electrode material for a non-aqueous electrolyte lithium ion battery according to the present invention can be widely applied to a non-aqueous electrolyte lithium ion battery.

  That is, the battery to which the positive electrode material of the present invention can be applied is a non-aqueous electrolyte lithium ion battery using lithium nickel manganese oxide that can be expected to have a high capacity. In particular, high energy density and high output density can be achieved, and it can be suitably used as a drive power source for vehicles, etc., and can be sufficiently applied to non-aqueous electrolyte secondary batteries for portable devices such as mobile phones. Therefore, although the following description demonstrates the nonaqueous electrolyte lithium ion secondary battery using the positive electrode material of this invention, it should not be restrict | limited at all to these.

[Current collector]
The current collector that can be used in the present invention is not particularly limited, and conventionally known current collectors can be used. For example, aluminum foil, stainless steel (SUS) foil, nickel-aluminum clad material, copper-aluminum clad material, SUS-aluminum clad material, or a plated material of a combination of these metals can be preferably used. Further, a current collector in which a metal surface is coated with aluminum may be used. Moreover, you may use the electrical power collector which bonded 2 or more metal foil depending on the case. When the composite current collector is used, as a material for the positive electrode current collector, for example, a conductive metal such as aluminum, an aluminum alloy, SUS, or titanium can be used, and aluminum is particularly preferable. On the other hand, as the material of the negative electrode current collector, for example, conductive metals such as copper, nickel, silver, and SUS can be used, and SUS and nickel are particularly preferable. Further, in the composite current collector, the positive electrode current collector and the negative electrode current collector may be electrically connected to each other directly or via a conductive intermediate layer made of a third material. In addition to the flat plate (foil), the positive electrode current collector and the negative electrode current collector are constituted by a lath plate, that is, a plate in which a mesh space is formed by expanding a plate with a cut. Can also be used.

  Although the thickness of a collector is not specifically limited, Usually, it is about 1-100 micrometers.

[Positive electrode active material layer]
Here, the constituent material of the positive electrode active material layer is characterized in that the positive electrode material of the present invention is used, and since it has already been described, the description thereof is omitted here.

  The thickness of the positive electrode active material layer is not particularly limited, and should be determined in consideration of the purpose of use of the battery (output importance, energy importance, etc.) and ion conductivity. The thickness of a general positive electrode active material layer is about 1 to 500 μm, and if it is within this range, it can be sufficiently used in the present invention, but in order to effectively express the function of the positive electrode material of the present invention, In particular, the range of 4 to 60 μm is desirable.

[Negative electrode active material layer]
As a constituent material of the negative electrode active material layer, any material using a negative electrode material may be used. The negative electrode material only needs to include a negative electrode active material. In addition to this, conductive aids to enhance electronic conductivity, binders, electrolyte supporting salts (lithium salts) to enhance ionic conductivity, polymer gels or solid electrolytes (host polymers, electrolytes, etc.), etc. Can be. Except for the type of the negative electrode active material, the content is basically the same as that described in the section “Positive electrode material for non-aqueous electrolyte lithium ion battery” of the present invention, and thus the description thereof is omitted here.

  As a negative electrode active material, the negative electrode active material used also in a conventionally well-known solution-type lithium ion battery can be used. Specifically, a negative electrode mainly composed of at least one selected from carbon materials such as natural graphite, artificial graphite, amorphous carbon, coke and mesophase pitch carbon fiber, graphite, and hard carbon which is amorphous carbon. Although it is desirable to use an active material, it is not particularly limited. In addition, a metal oxide (particularly a transition metal oxide, specifically titanium oxide), a composite oxide of a metal (particularly a transition metal, specifically titanium) and lithium, or the like can also be used.

[Nonaqueous electrolyte layer]
The present invention can be applied to any of (a) a separator impregnated with an electrolytic solution, (b) a polymer gel electrolyte, and (c) a polymer solid electrolyte depending on the purpose of use.

(A) Separator soaked with electrolyte solution As an electrolyte solution that can be soaked into the separator, the electrolyte contained in the polymer gel electrolyte of the above-described "positive electrode material for non-aqueous electrolyte lithium ion battery" of the present invention Since the same liquid (electrolyte salt and plasticizer) can be used, description thereof will be omitted. However, if a suitable example of the electrolytic solution is shown, as the electrolyte, LiClO ₄ , LiAsF ₆ , LiPF _{5 are used.} , LiBOB, LiCF ₃ SO ₃ and Li (CF ₃ SO ₂ ) ₂ , and as a solvent, ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate, methyl ethyl carbonate 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydride The concentration of the electrolyte is adjusted to 0.5 to 2 mol / liter by dissolving at least one kind of ethers composed of furan, 1,3-dioxolane and γ-butyllactone and dissolving the electrolyte in the solvent. However, the present invention should not be limited to these.

  The separator is not particularly limited, and a conventionally known separator can be used. For example, a porous sheet made of a polymer that absorbs and holds the electrolytic solution (for example, a polyolefin microporous material). Separator, etc.), a nonwoven fabric separator, etc. can be used. The polyolefin microporous separator having the property of being chemically stable to an organic solvent has an excellent effect that the reactivity with the electrolyte (electrolytic solution) can be kept low.

  Examples of the material for the porous sheet such as the polyolefin-based microporous separator include a laminate having a three-layer structure of polyethylene (PE), polypropylene (PP), PP / PE / PP, and polyimide.

  As the material of the nonwoven fabric separator, for example, conventionally known materials such as cotton, rayon, acetate, nylon, polyester, polypropylene, polyethylene such as polyethylene, polyimide, aramid, etc. can be used, and the purpose of use (machine required for the electrolyte layer) Depending on strength, etc., they are used alone or in combination.

  Further, the bulk density of the nonwoven fabric is not particularly limited as long as sufficient battery characteristics can be obtained by the impregnated polymer gel electrolyte. That is, if the bulk density of the nonwoven fabric is too large, the proportion of the non-electrolyte material in the electrolyte layer becomes too large, which may impair the ionic conductivity in the electrolyte layer.

  The thickness of the separator (including the nonwoven fabric separator) cannot be unambiguously defined because it varies depending on the intended use. In use, it is desirable to be 5 to 200 μm. When the thickness of the separator is within such a range, it is possible to suppress increase in retention and resistance. In addition, there is an effect of securing mechanical strength in the thickness direction and ensuring high output performance because it is desirable to prevent a short circuit caused by fine particles entering the separator and to narrow the space between the electrodes for high output. . In addition, when a plurality of batteries are connected, the electrode area increases, so that it is desirable to use a thick separator in the above range in order to increase the reliability of the battery.

  It is desirable that the fine pore diameter of the separator (polyolefin-based microporous separator or the like) is 1 μm or less (usually a pore diameter of about several tens of nm). When the average diameter of the micropores in the separator is within the above range, the “shutdown phenomenon” that the separator melts due to heat and the micropores close quickly occurs, resulting in higher reliability during abnormalities, resulting in heat resistance. Has the effect of improving. In other words, when the battery temperature rises due to overcharging (in an abnormal state), the “shutdown phenomenon” that the separator melts and closes the micropores occurs quickly, so that the positive electrode (+) of the battery (electrode) Li ions cannot pass through to the negative electrode (−) side, and no further charge is possible. As a result, overcharging cannot be performed and overcharging is eliminated. As a result, the heat resistance (safety) of the battery is improved, and it is possible to prevent gas from being released and the heat fusion part (seal part) of the battery exterior material from being opened. Here, the average diameter of the micropores of the separator is calculated as an average diameter obtained by observing the separator with a scanning electron microscope or the like and statistically processing the photograph with an image analyzer or the like.

  The porosity of the separator (such as a polyolefin microporous separator) is desirably 20 to 50%. The separator's porosity is within the above range, preventing output from being reduced due to the resistance of the electrolyte (electrolyte), and preventing the short circuit caused by fine particles penetrating the separator's pores (micropores). It has the effect of securing both sexes. Here, the porosity of the separator is a value obtained as a volume ratio from the density of the raw material resin and the density of the separator of the final product.

  The porosity of the nonwoven fabric separator is preferably 50 to 90%. If the porosity is less than 50%, the electrolyte retention deteriorates, and if it exceeds 90%, the strength is insufficient.

  The amount of the electrolytic solution impregnated in the separator may be impregnated to the range of the liquid retention capacity of the separator, but may be impregnated beyond the liquid retention capacity range. This can prevent impregnation of the electrolyte from the electrolyte layer by injecting a resin into the electrolyte seal portion, and therefore can be impregnated as long as the electrolyte layer can be retained. The electrolyte can be impregnated in the separator by a conventionally known method, for example, the electrolyte can be completely sealed after being injected by a vacuum injection method or the like.

(B) Polymer gel electrolyte and (c) Polymer solid electrolyte As the polymer gel electrolyte and polymer solid electrolyte, the polymer gel described in the section “Positive electrode material for non-aqueous electrolyte lithium ion battery” of the present invention described above is used. Since the same electrolyte and polymer solid electrolyte can be used, description thereof is omitted here.

  In addition, the above (b) includes those obtained by impregnating and supporting the polymer gel electrolyte in the separator described in the above (a). In this case, the amount of the polymer gel electrolyte impregnated / supported in the separator may be impregnated / supported up to the range of the liquid retention / retention capacity of the separator. May be. This is because resin can be injected into the electrolyte seal portion to prevent the electrolyte solution from leaking out from the electrolyte layer (mainly polymer gel electrolyte), so that the electrolyte layer can be impregnated and supported as long as it can be retained and retained. Is possible. The polymer gel electrolyte is a polymer electrolyte raw material host polymer, an electrolytic solution or a lithium salt applied to and impregnated in the separator, and then heated to crosslink the host polymer, and the separator is impregnated with the polymer gel electrolyte. What is necessary is just to carry | support, and it does not restrict | limit in particular.

  Similarly, the above (c) includes the one in which the polymer solid electrolyte is supported on the separator described in the above (a). In this case, the amount of the solid polymer electrolyte supported on the separator may be supported up to the holding capacity range of the separator, but may be supported beyond the holding capacity range. Since there is no electrolyte solution that causes the electrolyte layer to bleed out, there is no risk of liquid junction. Therefore, the electrolyte layer can be supported as long as it can be held in the electrolyte layer. The polymer solid electrolyte is applied to the separator with the host polymer, solvent (mainly viscosity adjusting solvent) or lithium salt as the raw material of the polymer electrolyte, and heated to crosslink the host polymer and remove the solvent. The separator is not particularly limited, for example, a polymer solid electrolyte may be supported on the separator.

  The electrolyte layers (a) to (c) may be used in one battery.

  In addition, the polymer electrolyte may be included in the polymer gel electrolyte layer, the positive electrode active material layer, and the negative electrode active material layer, but the same polymer electrolyte may be used, or different polymer electrolytes may be used depending on the layer. Good.

  By the way, a host polymer for a polymer gel electrolyte that is preferably used at present is a polyether polymer such as PEO and PPO. For this reason, the oxidation resistance on the positive electrode side under high temperature conditions is weak. Therefore, when using a positive electrode material having a high oxidation-reduction potential, the capacity of the negative electrode (active material layer) is preferably smaller than the capacity of the positive electrode (active material layer) opposed via the polymer gel electrolyte layer. When the capacity of the negative electrode (active material layer) is less than the capacity of the opposing positive electrode (active material layer), it is possible to prevent the positive electrode potential from rising excessively at the end of charging. In addition, the capacity | capacitance of a positive electrode (active material layer) and a negative electrode (active material layer) can be calculated | required from manufacturing conditions as theoretical capacity | capacitance at the time of manufacturing a positive electrode (active material layer) and a negative electrode (active material layer). You may measure the capacity | capacitance of a finished product directly with a measuring device. However, if the capacity of the negative electrode (active material layer) is smaller than the capacity of the opposing positive electrode (active material layer), the negative electrode potential will drop too much and the durability of the battery may be impaired. There is a need. For example, care should be taken not to lower the durability by setting the average charge voltage of one cell (single cell layer) to an appropriate value for the oxidation-reduction potential of the positive electrode active material.

The thickness of the electrolyte layer constituting the battery is not particularly limited. However, in order to obtain a compact battery, it is preferable to make it as thin as possible within a range in which the function as an electrolyte can be ensured, and the thickness of the electrolyte layer is preferably 5 to 200 μm.
[Positive electrode and negative electrode terminal plate]
When using positive and negative terminal plates, in addition to having a function as a terminal, it is better to be as thin as possible from the viewpoint of thinning, but the laminated electrode, electrolyte and current collector all have mechanical strength. Since it is weak, it is desirable to have strength to sandwich and support these from both sides. Furthermore, it can be said that the thickness of the positive electrode and the negative electrode terminal plate is usually preferably about 0.1 to 2 mm from the viewpoint of suppressing the internal resistance at the terminal portion.

  As materials for the positive electrode and the negative electrode terminal plate, materials used in a conventionally known lithium ion battery can be used. For example, aluminum, copper, titanium, nickel, stainless steel (SUS), and alloys thereof can be used. Aluminum is preferably used from the viewpoints of corrosion resistance, ease of production, economy, and the like.

  The material of the positive electrode terminal plate and the negative electrode terminal plate may be the same material or different materials. Furthermore, the positive electrode and the negative electrode terminal plate may be a laminate of different materials.

[Positive electrode and negative electrode lead]
Regarding the positive electrode and the negative electrode lead, the same lead as that used in a conventionally known lithium ion battery can be used. In addition, the part taken out from the battery exterior material (battery case) does not affect the product (for example, automobile parts, especially electronic devices, etc.) by contacting with peripheral devices or wiring and leaking electricity. It is preferable to coat with a heat-resistant insulating heat-shrinkable tube or the like.

[Battery exterior material (battery case)]
In a lithium ion battery, in order to prevent external impact and environmental degradation during use, it is desirable to accommodate the entire battery stack or battery winding body, which is the battery body, in a battery exterior material or battery case. From the viewpoint of weight reduction, a polymer-metal composite laminate film in which both surfaces of metals (including alloys) such as aluminum, stainless steel, nickel, and copper are covered with an insulator (preferably a heat-resistant insulator) such as a polypropylene film. It is preferable that the battery stack is housed and sealed by joining a part or all of the peripheral part thereof by heat fusion using a conventionally known battery exterior material. In this case, the positive electrode and the negative electrode lead may be structured to be sandwiched between the heat-sealed portions and exposed to the outside of the battery exterior material. In addition, it is preferable to use a polymer-metal composite laminate film having excellent thermal conductivity because heat can be efficiently transmitted from a heat source of an automobile and the inside of the battery can be quickly heated to the battery operating temperature. The polymer-metal composite laminate film is not particularly limited, and a conventionally known film in which a metal film is disposed between polymer films and the whole is laminated and integrated can be used. As specific examples, for example, an outer protective layer made of a polymer film (laminate outermost layer), a metal film layer, a heat-sealing layer made of a polymer film (laminate innermost layer), and the whole is laminated and integrated. The thing which becomes. Specifically, in the polymer-metal composite laminate film used for the exterior material, a heat-resistant insulating resin film is first formed as a polymer film on both surfaces of the metal film, and heat fusion is performed on at least one heat-resistant insulating resin film. An insulating insulating film is laminated. Such a laminate film is heat-sealed by an appropriate method, whereby the heat-welding insulating film portion is fused and joined to form a heat-sealing portion. An example of the metal film is an aluminum film. Moreover, as said insulating resin film, a polyethylene tetraphthalate film (heat-resistant insulating film), a nylon film (heat-resistant insulating film), a polyethylene film (heat-bonding insulating film), a polypropylene film (heat-bonding insulating film) ) Etc. can be illustrated. However, the exterior material of the present invention should not be limited to these. In such a laminate film, it is possible to easily and surely join one to one (bag-like) laminate films by heat fusion using a heat fusion insulating film by ultrasonic welding or the like. In order to maximize the long-term reliability of the battery, metal films that are constituent elements of the laminate sheet may be directly joined. Ultrasonic welding can be used to join the metal films by removing or destroying the heat-fusible resin between the metal films.

  The nonaqueous electrolyte lithium ion battery of the present invention described above may be a bipolar nonaqueous electrolyte lithium ion battery (also referred to as a bipolar battery) or a nonaqueous bipolar lithium ion battery (not bipolar). (Also referred to as a battery).

  Next, as a use of the nonaqueous electrolyte lithium ion secondary battery of the present invention, for example, a large-capacity power source such as a hybrid vehicle, an electric vehicle (EV), a hybrid electric vehicle (HEV), a fuel cell vehicle, and a hybrid fuel cell vehicle Thus, it can be suitably used for a vehicle driving power source and an auxiliary power source that require high energy density and high output density. In this case, it is desirable that the assembled battery is constructed by connecting a plurality of the nonaqueous electrolyte lithium ion batteries of the present invention. That is, in the present invention, an assembled battery (vehicle sub-module) is formed using at least one of the plurality of nonaqueous electrolyte lithium ion secondary devices in parallel connection, series connection, parallel-series connection, or series-parallel connection. be able to. This makes it possible to meet the demands for capacity and voltage for various types of vehicles by combining basic batteries. As a result, it becomes possible to facilitate the design selectivity of required energy and output. For this reason, it is not necessary to design and produce different batteries for various vehicles, and it becomes possible to mass-produce basic batteries and to reduce costs by mass production. Hereinafter, a representative embodiment of the assembled battery (vehicle submodule) will be briefly described with reference to the drawings.

  The other constituent requirements of the assembled battery should not be limited at all, and the same constituent requirements as the assembled battery using the existing lithium ion secondary battery can be applied as appropriate. Since conventionally known components and manufacturing techniques for assembled batteries can be used, the description thereof is omitted here.

  Next, at least two or more of the above-mentioned assembled batteries (vehicle submodules) are combined in series, parallel, or in series and parallel to form a combined battery (vehicle assembled battery). It is possible to meet the demand for output relatively inexpensively without producing a new assembled battery. In other words, the composite assembled battery of the present invention comprises at least an assembled battery (such as one composed only of the bipolar battery or non-bipolar battery of the present invention, or a combination of the bipolar battery of the present invention and a non-bipolar battery). It is characterized by two or more series, parallel, or series and parallel composite connections. By manufacturing a standard assembled battery and combining it into a composite assembled battery, the specifications of the assembled battery can be tuned. . Thereby, since it is not necessary to manufacture many assembled battery types with different specifications, the composite assembled battery cost can be reduced.

  Moreover, in the said composite assembled battery, it is desirable to connect the some assembled battery which comprises this so that attachment or detachment is possible respectively. As described above, in the composite assembled battery in which a plurality of assembled batteries are connected in series and parallel, even if some of the batteries and the assembled battery fail, the repair can be performed only by replacing the failed part.

  The vehicle according to the present invention is characterized in that the assembled battery and / or the composite assembled battery is mounted. This makes it possible to meet a large vehicle demand for space by using a light and small battery. By reducing the battery space, the weight of the vehicle can be reduced.

  For example, in order to mount the composite assembled battery on a vehicle such as a hybrid car, an electric vehicle, or a fuel cell, the composite assembled battery is mounted under a seat (seat) at the center of the vehicle body of the vehicle. This is because if it is installed under the seat, the interior space and the trunk room can be widened. The place where the battery is mounted is not limited to under the seat, but may be under the floor of the vehicle, behind the seat back, under the rear trunk room, or in the engine room in front of the vehicle.

  In the present invention, not only the composite battery pack but also the battery pack may be mounted on the vehicle depending on the intended use, or the composite battery pack and the battery pack may be mounted in combination. In addition, as a vehicle on which the assembled battery and / or the composite assembled battery of the present invention can be mounted, for example, as a driving power supply or an auxiliary power supply, an ordinary hybrid car (a gasoline engine and the assembled battery of the present invention and / or Combinations of composite assembled batteries), electric vehicles, hybrid electric vehicles, fuel cell vehicles, hybrid fuel cell vehicles and the like are preferred, but are not limited thereto.

  Hereinafter, the content of the present invention will be described with reference to examples and comparative examples, but the present invention is not limited to these examples. In the following examples and comparative examples, unless otherwise specified, “%” represents “ratio of molar ratio in (transition metal atom) (mol%)”.

Examples and Comparative Examples 1-1. Preparation of positive electrode (powder) (Examples 1-5, 11-22, Comparative Examples 1-2, 4-8)
Lithium hydroxide hydrate and nickel hydroxide containing 30% manganese and 30% cobalt were dissolved in pure water. In this process, compounds containing magnesium, zinc, nitrogen and phosphorus were further mixed according to the compositions of the lithium nickel manganese oxides of the examples and comparative examples. The mixture was heated from room temperature to 300 ° C. and dehydrated in air for 24 hours. Then, it thermally decomposed between 300-500 degreeC for 8 hours, and baked for 24 hours, performing homogenization in 500-850 degreeC and oxygen atmosphere. In the main firing step, lithium nickel composite oxide particles grow. Each Example and Comparative Example were carried out by changing the type and amount of the raw material of the substitution product up to this step and the annealing temperature condition after the main firing. In each example and comparative example to be described later, the process will be described, and other requirements are the same in each example and comparative example. In addition, the average particle diameter of the lithium nickel manganese oxide (positive electrode active material) particles obtained here was 5 μm.

  75% by mass of the obtained lithium nickel manganese oxide (positive electrode active material), 10% by mass of the conductive auxiliary agent acetylene black (Denka black), and 15% by mass of the binder polyvinylidene fluoride (also referred to as PVDF), N-methyl-2-pyrrolidone (also referred to as NMP) is added as a solvent and stirred to prepare a slurry, which is applied onto an aluminum foil (thickness 20 μm) of a positive electrode current collector with an applicator, and vacuum After drying by heating at about 80 ° C. with a dryer, the electrode was punched to a diameter of 15 mm and dried at 90 ° C. in a high vacuum for 6 hours. The thickness of the punched positive electrode active material layer was 50 μm.

1-2. Production of positive electrode (thin film) (Examples 6 to 10 and Example 1 ′)
Lithium hydroxide hydrate and nickel hydroxide containing 30% Co and 30% Mn were dissolved in pure water. The mixture was heated from room temperature to 300 ° C. with stirring, and dehydrated in air for 24 hours. Then, thermal decomposition was performed between 300 ° C. and 500 ° C. in the air for 8 hours, and calcination was performed at 500 to 850 ° C. in an oxygen atmosphere for 24 hours. Thereafter, annealing was performed at 500 ° C. in an atmosphere of 1 atmosphere of oxygen for 12 hours. The powder obtained by annealing was formed into a cylindrical pellet having a diameter of 20 mm and a thickness of 5 mm, and sintered in an oxygen atmosphere at 850 ° C. for 12 hours. Using the pellet as a target, a film was formed on a conductive SrTiO ₃ (100) substrate using a pulsed laser deposition (PLD) method. The film forming conditions were a temperature of 700 ° C., an oxygen partial pressure of 100 mmHg, and 6 hours. The film pressure produced was about 500 nm. After film formation in this step, Examples 6 to 10 and Example 1 ′ were performed by further changing the annealing temperature conditions. Therefore, in Examples 6 to 10 and Example 1 ′ to be described later, the process will be described, and other requirements are the same in each Example, and will be described collectively below. In addition, about the thin film-like lithium nickel manganese oxide (positive electrode active material) obtained by annealing (oxygen partial pressure of 0 to 0.8 atm, 300 ° C.) after the film formation, the composition and oxygen termination rate shown in Table 3 were obtained. Used as a sample for measurement. On the other hand, powdered lithium nickel manganese oxide (positive electrode active material) obtained by annealing (oxygen partial pressure of 0 to 0.8 atm, 300 ° C.) without forming a film is used for a laminate cell. The resistance ratios 2 and 3 shown in Table 3 and the elution amount of Mn were measured.

  75% by mass of the obtained lithium nickel manganese oxide (positive electrode active material), 10% by mass of the conductive auxiliary agent acetylene black (Denka black), and 15% by mass of the binder polyvinylidene fluoride (also referred to as PVDF), N-methyl-2-pyrrolidone (also referred to as NMP) is added as a solvent and stirred to prepare a slurry, which is applied onto an aluminum foil (thickness 20 μm) of a positive electrode current collector with an applicator, and vacuum After drying by heating at about 80 ° C. with a dryer, the electrode was punched to a diameter of 15 mm and dried at 90 ° C. in a high vacuum for 6 hours. The thickness of the punched positive electrode active material layer was 50 μm.

2. Production of negative electrode (all the same in each example and comparative example)
85% by mass of carbon-based material hard carbon (Super P; manufactured by Kureha Chemical Co., Ltd.), 8% by mass of conductive auxiliary agent acetylene black (DENKA BLACK), vapor grown carbon fiber (VGCF) 2% by mass, PVDF of the binder to 5% by mass, NMP as a solvent is added and stirred to adjust the slurry, and is applied onto the copper foil (thickness 20 μm) of the negative electrode current collector with an applicator. After heating and drying at about 80 ° C. with a vacuum dryer, the electrode was punched to a diameter of 16 mm and dried at 90 ° C. in a high vacuum for 6 hours. The thickness of the active material layer of the punched negative electrode was 80 μm.

3. Production of Battery Using the positive electrode produced above (for details, see Examples 1-22, Example 1 ′ and Comparative Examples 1-2, 4-8 described later) and negative electrode (all the same), A battery (laminate cell) was constructed. Specifically, a polypropylene microporous separator (average pore diameter of 800 nm, porosity of 35%, thickness of 30 μm) is used as the separator, and 1.0 M LiPF ₆ PC + EC + DEC solution (PC) is used as the non-aqueous electrolyte. : EC: DEC = 2: 2: 6 (volume ratio)), a laminate cell was assembled. The capacity balance between the positive and negative electrodes was controlled by the positive electrode.

4-1. Evaluation of battery: measurement of resistance ratio 1 (Examples 1-5, 11-22 and Comparative Examples 1-2, 4-8)
(Initial charge / discharge)
First, the number of samples is 5 cells. Immediately after the production of the laminate cell, as initial charging, constant current charging is performed up to an upper limit voltage of 4.2 V corresponding to 0.2 C in terms of positive electrode at room temperature, and further 12 by 4.2 V constant voltage charging. The battery was charged for an hour and stored (aging) at a room temperature of 4.2 V for 1 week. Thereafter, the depth of discharge (DOD) was adjusted to 50% at 25 ° C., constant current discharge was performed at 3C equivalent for 10 seconds, and the initial resistance was determined by direct current from the voltage drop. All were averaged.

(Preservation test)
Next, after storage (aging) at room temperature of 4.2 V for 1 week, the product was stored at 60 ° C. for 1 month. Thereafter, the DOD was adjusted to 50% at 25 ° C., a constant current discharge was performed at 3C for 10 seconds, and the resistance after storage for one month was determined from the voltage drop.

  The resistance ratio 1 was calculated from the resistance after one month storage of each sample and the resistance after one month storage of Comparative Example 1 by the calculation shown below. In all cases, the average number of samples was 5 cells.

4-2. Battery evaluation: measurement of resistance ratios 2 and 3 (Examples 6 to 10 and Example 1 ′)
(Initial charge / discharge)
First, immediately after production of the laminate cell, as an initial charge, constant current charge was performed up to an upper limit voltage of 4.2 V corresponding to 0.2 C in terms of positive electrode at room temperature, held at room temperature of 4.2 V for 2 hours, and rested for 2 hours. . Thereafter, the discharge depth (DOD) was adjusted to 50% at 25 ° C., constant current discharge was performed at 1 C for 10 seconds, and the initial resistance was calculated from the voltage drop. In all cases, the average number of samples was 5 cells.

(Cycle test)
Next, after evaluating the initial resistance, a cycle test was performed under the following conditions. After the cycle test, the DOD was adjusted to 50% at 25 ° C., a constant current discharge was performed at 1 C for 10 seconds, and the resistance after the cycle test was calculated from the voltage drop.

  Cycle test conditions: constant current charge at 1C at 25 ° C, upper limit voltage 4.2V, pause 10 minutes, 1C equivalent constant current discharge, lower limit voltage 2.5V, pause 10 minutes as one cycle, 150 cycles Carried out.

  From the resistance after the cycle test of each sample (Examples 6 to 10 and Example 1 ') and the resistance after the cycle test of Example 1', the resistance ratio 2 was calculated by the following calculation. In all cases, the average number of samples was 5 cells.

  Moreover, the resistance ratio 3 was calculated from the resistance after the cycle test and the initial resistance for each sample (Examples 6 to 10 and Example 1 ') by the following formula. In all cases, the average number of samples was 5 cells.

<Measurement of Mn elution>
The battery (laminated cell) was discharged to 2.5V at 1C equivalent, the battery was disassembled, the negative electrode and the separator were heated in a mixed acid of nitric acid and sulfuric acid, and the insoluble portion was then mixed in a mixed acid of perchloric acid and sulfuric acid. Heat to dissolve completely. The amount of Mn in this solution was measured by ICP (inductively coupled plasma atomic emission spectrometry), and the amount of Mn eluted per gram of the positive electrode active material was calculated.

<Confirmation of composition and crystal structure>
The composition of the entire lithium nickel manganese oxide obtained as the positive electrode active material and the region (surface vicinity region) having a depth five times the c-axis length of the crystal from the primary particle surface was confirmed by TOF-MASS. In each of the examples and comparative examples, a region having a depth of up to 14.3 mm corresponding to five times the c-axis length of the crystal (R3-m crystal structure) from the surface of the primary particle is used as the surface vicinity region. It was measured. The crystal structure of the obtained lithium nickel manganese oxide was confirmed by powder XRD. Furthermore, the average valence of Mn in the surface vicinity region in each Example and Comparative Example is the lithium nickel manganese oxide obtained as the positive electrode active material (both in the range of 0.5 <x ≦ 1.1). The composition in the vicinity of the surface was measured and calculated.

"surface treatment"
Since the surface treatment (annealing treatment) in each of the examples and the comparative examples can be performed in a powder state or a film formation state, an experiment was performed for each as follows.

  The powders of Examples 1 to 5, 11 to 22, and Comparative Examples 1 to 2, and 4 to 8 were subjected to an experiment after annealing after firing. The thin films of Examples 6 to 10 and Example 1 'were subjected to an experiment after annealing. This is because the oxygen termination rates of Examples 6 to 10 and Example 1 ′ are defined by the following formula, and therefore it is necessary to form a thin film by film formation or the like so that the area can be measured. It is.

<Measurement method of oxygen termination rate>
The termination rate of oxygen was measured for thin films before and after annealing (measured at 10 × 10 nm ² area) by the in situ STM and RHEED diffraction patterns, and the oxygen termination rate was calculated by the following formula.

Comparative Examples 1 to 2 and Examples 1 to 5 below are related to LiNi _0.4 Co _0.3 Mn _0.3 O _c (c-axis length of crystals (R3-m crystal structure) from the primary particle surface). Experiments were carried out by changing the value of the O content c of the composition up to 3%; the composition in the vicinity of the surface including the region having a depth of 5 times the c-axis length of the crystal from the primary particle surface. Specifically, the experiment was conducted by introducing excess oxygen into the region in the vicinity of the surface (a part or all of the primary particle surface was terminated with oxygen).

Comparative Example 1
Lithium hydroxide hydrate and nickel hydroxide containing 30% Co and 30% Mn were dissolved in pure water. The mixture was heated from room temperature to 300 ° C. with stirring and dehydrated in air for 24 hours. Then, thermal decomposition was performed in the air between 300 ° C. and 500 ° C. for 8 hours, and calcined in an oxygen atmosphere at 500 to 850 ° C. for 24 hours. Thereafter, annealing was performed at 500 ° C. in an atmosphere of 1 atmosphere of oxygen for 12 hours. The experimental results using the obtained lithium nickel manganese oxide are shown in Table 2.

Comparative Example 2
Lithium hydroxide hydrate and nickel hydroxide containing 30% Co and 30% Mn were dissolved in pure water. The mixture was heated from room temperature to 300 ° C. with stirring and dehydrated in air for 24 hours. Then, thermal decomposition was performed in the air between 300 ° C. and 500 ° C. for 8 hours, and calcined in an oxygen atmosphere at 500 to 850 ° C. for 24 hours. Thereafter, annealing was performed at 500 ° C. in an atmosphere of 2 atmospheres of oxygen for 12 hours. The experimental results using the obtained lithium nickel manganese oxide are shown in Table 2.

Example 1
Lithium hydroxide hydrate and nickel hydroxide containing 30% Co and 30% Mn were dissolved in pure water. The mixture was heated from room temperature to 300 ° C. with stirring and dehydrated in air for 24 hours. Then, thermal decomposition was performed in the air between 300 ° C. and 500 ° C. for 8 hours, and calcined in an oxygen atmosphere at 500 to 850 ° C. for 24 hours. Thereafter, annealing was performed at 500 ° C. in an atmosphere of 4 atmospheres of oxygen for 12 hours. The experimental results using the obtained lithium nickel manganese oxide are shown in Table 2.

Example 2
Lithium hydroxide hydrate and nickel hydroxide containing 30% Co and 30% Mn were dissolved in pure water. The mixture was heated from room temperature to 300 ° C. with stirring, and dehydrated in air for 24 hours. Then, thermal decomposition was performed between 300 ° C. and 500 ° C. in the air for 8 hours, and calcination was performed at 500 to 850 ° C. in an oxygen atmosphere for 24 hours. Thereafter, annealing was performed at 500 ° C. in an atmosphere of oxygen at 6 atmospheres for 12 hours. The experimental results using the obtained lithium nickel manganese oxide are shown in Table 2.

Example 3
Lithium hydroxide hydrate and nickel hydroxide containing 30% Co and 30% Mn were dissolved in pure water. The mixture was heated from room temperature to 300 ° C. with stirring, and dehydrated in air for 24 hours. Then, thermal decomposition was performed between 300 ° C. and 500 ° C. in the air for 8 hours, and calcination was performed at 500 to 850 ° C. in an oxygen atmosphere for 24 hours. Thereafter, annealing was performed at 500 ° C. in an atmosphere of oxygen at 10 atmospheres for 12 hours. The experimental results using the obtained lithium nickel manganese oxide are shown in Table 2.

Example 4
Lithium hydroxide hydrate and nickel hydroxide containing 30% Co and 30% Mn were dissolved in pure water. The mixture was heated from room temperature to 300 ° C. with stirring, and dehydrated in air for 24 hours. Then, thermal decomposition was performed between 300 ° C. and 500 ° C. in the air for 8 hours, and calcination was performed at 500 to 850 ° C. in an oxygen atmosphere for 24 hours. Thereafter, annealing was performed at 500 ° C. in an atmosphere of oxygen at 15 atmospheres for 12 hours. The experimental results using the obtained lithium nickel manganese oxide are shown in Table 2.

Example 5
Lithium hydroxide hydrate and nickel hydroxide containing 30% Co and 30% Mn were dissolved in pure water. The mixture was heated from room temperature to 300 ° C. with stirring, and dehydrated in air for 24 hours. Then, thermal decomposition was performed between 300 ° C. and 500 ° C. in the air for 8 hours, and calcination was performed at 500 to 850 ° C. in an oxygen atmosphere for 24 hours. Thereafter, annealing was performed at 500 ° C. in an atmosphere of oxygen at 20 atmospheres for 12 hours. The experimental results using the obtained lithium nickel manganese oxide are shown in Table 2.

(Note) Although the content of O was higher than LiNi _0.4 Co _0.3 Mn _0.3 O _{2.4 in} Example 5, synthesis was impossible.

<Discussion>
It can be seen that as the oxygen partial pressure during firing increases, the oxygen composition ratio in the active material increases, and as a result, elution of Mn is clearly suppressed with a composition in which the valence of Mn exceeds 3.2. Moreover, resistance is also low and it turns out that deterioration is suppressed.

  In the following Example 1 'and Examples 6 to 10, a film was formed after firing, and an experiment was performed by changing the annealing conditions (surface treatment conditions) after the film formation. Specifically, an experiment was conducted in which excess oxygen was introduced into the region near the surface, and part or all of the primary particle surface was terminated with oxygen.

Example 1 '
Lithium hydroxide hydrate and nickel hydroxide containing 30% Co and 30% Mn were dissolved in pure water. The mixture was heated from room temperature to 300 ° C. with stirring, and dehydrated in air for 24 hours. Then, thermal decomposition was performed between 300 ° C. and 500 ° C. in the air for 8 hours, and calcination was performed at 500 to 850 ° C. in an oxygen atmosphere for 24 hours. Thereafter, the powder annealed at 500 ° C. in an atmosphere of 1 atmosphere of oxygen for 12 hours was formed into a cylindrical pellet having a diameter of 20 mm and a thickness of 5 mm and sintered in an oxygen atmosphere at 850 ° C. for 12 hours. A film was formed on the SrTiO ₃ (100) surface using the PLD method with the pellet as a target. Table 3 shows the experimental results using the obtained lithium nickel manganese oxide (powder and thin film).

Example 6
Lithium hydroxide hydrate and nickel hydroxide containing 30% Co and 30% Mn were dissolved in pure water. The mixture was heated from room temperature to 300 ° C. with stirring, and dehydrated in air for 24 hours. Then, thermal decomposition was performed between 300 ° C. and 500 ° C. in the air for 8 hours, and calcination was performed at 500 to 850 ° C. in an oxygen atmosphere for 24 hours. Thereafter, the powder annealed at 500 ° C. in an atmosphere of 1 atmosphere of oxygen for 12 hours was formed into a cylindrical pellet having a diameter of 20 mm and a thickness of 5 mm and sintered in an oxygen atmosphere at 850 ° C. for 12 hours. A film was formed on the SrTiO ₃ (100) surface using the PLD method with the pellet as a target. After film formation, annealing was performed for 24 hours at a substrate temperature of 300 ° C. and an oxygen partial pressure of 0.1 atm. Also, annealing was performed under the same oxygen partial pressure without film formation. Table 3 shows the experimental results using the lithium nickel manganese oxide (powder and thin film) thus obtained.

Example 7
Lithium hydroxide hydrate and nickel hydroxide containing 30% Co and 30% Mn were dissolved in pure water. The mixture was heated from room temperature to 300 ° C. with stirring, and dehydrated in air for 24 hours. Then, thermal decomposition was performed between 300 ° C. and 500 ° C. in the air for 8 hours, and calcination was performed at 500 to 850 ° C. in an oxygen atmosphere for 24 hours. Thereafter, the powder annealed at 500 ° C. in an atmosphere of 1 atmosphere of oxygen for 12 hours was formed into a cylindrical pellet having a diameter of 20 mm and a thickness of 5 mm and sintered in an oxygen atmosphere at 850 ° C. for 12 hours. A film was formed on the SrTiO ₃ (100) surface using the PLD method with the pellet as a target. After the film formation, annealing was performed for 24 hours at a substrate temperature of 300 ° C. and an oxygen partial pressure of 0.2 atm. Also, annealing was performed under the same oxygen partial pressure without film formation. Table 3 shows the experimental results using the lithium nickel manganese oxide (powder and thin film) thus obtained.

Example 8
Lithium hydroxide hydrate and nickel hydroxide containing 30% Co and 30% Mn were dissolved in pure water. The mixture was heated from room temperature to 300 ° C. with stirring, and dehydrated in air for 24 hours. Then, thermal decomposition was performed between 300 ° C. and 500 ° C. in the air for 8 hours, and calcination was performed at 500 to 850 ° C. in an oxygen atmosphere for 24 hours. Thereafter, the powder annealed at 500 ° C. in an atmosphere of 1 atmosphere of oxygen for 12 hours was formed into a cylindrical pellet having a diameter of 20 mm and a thickness of 5 mm and sintered in an oxygen atmosphere at 850 ° C. for 12 hours. A film was formed on the SrTiO ₃ (100) surface using the PLD method with the pellet as a target. After the film formation, the substrate temperature was set to 300 ° C., and the oxygen partial pressure was set to 0.4 atm. Also, annealing was performed under the same oxygen partial pressure without film formation. Table 3 shows the experimental results using the lithium nickel manganese oxide (powder and thin film) thus obtained.

Example 9
Lithium hydroxide hydrate and nickel hydroxide containing 30% Co and 30% Mn were dissolved in pure water. The mixture was heated from room temperature to 300 ° C. with stirring, and dehydrated in air for 24 hours. Then, thermal decomposition was performed between 300 ° C. and 500 ° C. in the air for 8 hours, and calcination was performed at 500 to 850 ° C. in an oxygen atmosphere for 24 hours. Thereafter, the powder annealed at 500 ° C. in an atmosphere of 1 atmosphere of oxygen for 12 hours was formed into a cylindrical pellet having a diameter of 20 mm and a thickness of 5 mm and sintered in an oxygen atmosphere at 850 ° C. for 12 hours. A film was formed on the SrTiO ₃ (100) surface using the PLD method with the pellet as a target. After the film formation, the substrate temperature was set to 300 ° C., and the oxygen partial pressure was set to 0.6 atm. Also, annealing was performed under the same oxygen partial pressure without film formation. Table 3 shows the experimental results using the lithium nickel manganese oxide (powder and thin film) thus obtained.

Example 10
Lithium hydroxide hydrate and nickel hydroxide containing 30% Co and 30% Mn were dissolved in pure water. The mixture was heated from room temperature to 300 ° C. with stirring, and dehydrated in air for 24 hours. Then, thermal decomposition was performed between 300 ° C. and 500 ° C. in the air for 8 hours, and calcination was performed at 500 to 850 ° C. in an oxygen atmosphere for 24 hours. Thereafter, the powder annealed at 500 ° C. in an atmosphere of 1 atmosphere of oxygen for 12 hours was formed into a cylindrical pellet having a diameter of 20 mm and a thickness of 5 mm and sintered in an oxygen atmosphere at 850 ° C. for 12 hours. A film was formed on the SrTiO ₃ (100) surface using the PLD method with the pellet as a target. After the film formation, the substrate temperature was set to 300 ° C., and the oxygen partial pressure was set to 1 atm. Also, annealing was performed under the same oxygen partial pressure without film formation. Table 3 shows the experimental results using the lithium nickel manganese oxide (powder and thin film) thus obtained.

<Discussion>
In the present invention, the durability of the electrode is improved by increasing the valence of Mn from 3.2, but in addition, it can be seen that a further effect can be obtained by introducing an oxygen terminal on the surface.

In Comparative Example 4 and Examples 11 to 12 below, LiNi _0.4 Co _0.3 Mn _a M _b O ₂ (from the primary particle surface to the crystal (R3-m crystal structure) c-axis length up to 14.3 mm The composition b in the vicinity of the surface including the region having a depth of 5 times the c-axis length of the crystal from the surface of the primary particle) was changed for the M (= Mg) content b. Specifically, the experiment was performed by partially replacing Mn in the vicinity of the surface with Mg of +2 valent ions.

Comparative Example 4
Lithium hydroxide hydrate and nickel hydroxide containing Co 30%, Mn 27% and Mg 3% were dissolved in pure water. The mixture was heated from room temperature to 300 ° C. with stirring, and dehydrated in air for 24 hours. Then, thermal decomposition was performed between 300 ° C. and 500 ° C. in the air for 8 hours, and calcination was performed at 500 to 850 ° C. in an oxygen atmosphere for 24 hours. Thereafter, annealing was performed at 500 ° C. in an atmosphere of 1 atmosphere of oxygen for 12 hours. Table 4 shows the experimental results using the obtained lithium nickel manganese oxide.

Example 11
Lithium hydroxide hydrate and nickel hydroxide containing Co 30%, Mn 24% and Mg 6% were dissolved in pure water. The mixture was heated from room temperature to 300 ° C. with stirring, and dehydrated in air for 24 hours. Then, thermal decomposition was performed between 300 ° C. and 500 ° C. in the air for 8 hours, and calcination was performed at 500 to 850 ° C. in an oxygen atmosphere for 24 hours. Thereafter, annealing was performed at 500 ° C. in an atmosphere of 1 atmosphere of oxygen for 12 hours. Table 4 shows the experimental results using the obtained lithium nickel manganese oxide.

Example 12
Lithium hydroxide hydrate and nickel hydroxide containing Co 30%, Mn 20% and Mg 10% were dissolved in pure water. The mixture was heated from room temperature to 300 ° C. with stirring, and dehydrated in air for 24 hours. Then, thermal decomposition was performed between 300 ° C. and 500 ° C. in the air for 8 hours, and calcination was performed at 500 to 850 ° C. in an oxygen atmosphere for 24 hours. Thereafter, annealing was performed at 500 ° C. in an atmosphere of 1 atmosphere of oxygen for 12 hours. Table 4 shows the experimental results using the obtained lithium nickel manganese oxide.

(Note) Although the content b of M = Mg is higher than that of LiNi _0.4 Co _0.3 Mn _0.2 Mg _0.1 O _{2 in} Example 12, synthesis is impossible, and MgO phase is used as an impurity. confirmed.

<Discussion>
Furthermore, it can be seen that introduction of a typical metal element having a low valence increases the valence of Mn and increases the durability.

Comparative Example 5 and Examples 13 to 14 below are LiNi _0.4 Co _0.3 Mn _a M _b O ₂ (from the primary particle surface to the crystal (R3-m crystal structure) c-axis length up to 14.3 mm. The composition b in the vicinity of the surface including the region 5 times deeper than the c-axis length of the crystal from the surface of the primary particles) was changed for the value of M (= Zn) content b. Specifically, the experiment was performed by substituting Mn in the region near the surface with Zn of +2 valent ions.

Comparative Example 5
Lithium hydroxide hydrate and nickel hydroxide containing Co 30%, Mn 28% and Zn 2% were dissolved in pure water. The mixture was heated from room temperature to 300 ° C. with stirring, and dehydrated in air for 24 hours. Then, thermal decomposition was performed between 300 ° C. and 500 ° C. in the air for 8 hours, and calcination was performed at 500 to 850 ° C. in an oxygen atmosphere for 24 hours. Thereafter, annealing was performed at 500 ° C. in an atmosphere of 1 atmosphere of oxygen for 12 hours. Table 5 shows the experimental results using the obtained lithium nickel manganese oxide.

Example 13
Lithium hydroxide hydrate and nickel hydroxide containing Co 30%, Mn 24% and Zn 6% were dissolved in pure water. The mixture was heated from room temperature to 300 ° C. with stirring, and dehydrated in air for 24 hours. Then, thermal decomposition was performed between 300 ° C. and 500 ° C. in the air for 8 hours, and calcination was performed at 500 to 850 ° C. in an oxygen atmosphere for 24 hours. Thereafter, annealing was performed at 500 ° C. in an atmosphere of 1 atmosphere of oxygen for 12 hours. Table 5 shows the experimental results using the obtained lithium nickel manganese oxide.

Example 14
Lithium hydroxide hydrate and nickel hydroxide containing Co 30%, Mn 20% and Zn 10% were dissolved in pure water. The mixture was heated from room temperature to 300 ° C. with stirring, and dehydrated in air for 24 hours. Then, thermal decomposition was performed between 300 ° C. and 500 ° C. in the air for 8 hours, and calcination was performed at 500 to 850 ° C. in an oxygen atmosphere for 24 hours. Thereafter, annealing was performed at 500 ° C. in an atmosphere of 1 atmosphere of oxygen for 12 hours. Table 5 shows the experimental results using the obtained lithium nickel manganese oxide.

(Note) Although the M = Zn content b is higher than that of LiNi _0.4 Co _0.3 Mn _0.2 Zn _0.1 O _{2 in} Example 14, synthesis is impossible, and ZnO phase is used as an impurity. confirmed.

<Discussion>
Moreover, even if it is a transition metal, if there are few oxidation numbers, it will lead to the increase in the valence of Mn and durability will improve.

Comparative Example 6 and Examples 15 to 17 below are for LiNi _0.4 Co _0.3 Mn _0.3 O _2-d N _d (c-axis length of crystals (R3-m crystal structure) from the primary particle surface). Experiments were conducted by changing the value of the N content d of the composition up to 14.3%; the composition in the vicinity of the surface including the region having a depth of 5 times the c-axis length of the crystal from the primary particle surface. Specifically, the experiment was performed by partially replacing oxygen in the vicinity of the surface with N of -3valent ions.

Comparative Example 6
Lithium hydroxide hydrate, nickel hydroxide containing Co 30% and Mn 25%, and manganese nitrate 5% were dissolved in pure water. The mixture was heated from room temperature to 300 ° C. with stirring, and dehydrated in air for 24 hours. Then, thermal decomposition was performed between 300 ° C. and 500 ° C. in the air for 8 hours, and calcination was performed at 500 to 850 ° C. in an oxygen atmosphere for 24 hours. Thereafter, annealing was performed at 500 ° C. in an atmosphere of 1 atmosphere of oxygen for 12 hours. Table 6 shows the experimental results using the obtained lithium nickel manganese oxide.

Example 15
Lithium hydroxide hydrate, nickel hydroxide containing Co 30% and Mn 22%, and manganese nitrate 8% were dissolved in pure water. The mixture was heated from room temperature to 300 ° C. with stirring, and dehydrated in air for 24 hours. Then, thermal decomposition was performed between 300 ° C. and 500 ° C. in the air for 8 hours, and calcination was performed at 500 to 850 ° C. in an oxygen atmosphere for 24 hours. Thereafter, annealing was performed at 500 ° C. in an atmosphere of 1 atmosphere of oxygen for 12 hours. Table 6 shows the experimental results using the obtained lithium nickel manganese oxide.

Example 16
Lithium hydroxide hydrate, nickel hydroxide containing Co 30% and Mn 5%, and manganese nitrate 15% were dissolved in pure water. The mixture was heated from room temperature to 300 ° C. with stirring, and dehydrated in air for 24 hours. Then, thermal decomposition was performed between 300 ° C. and 500 ° C. in the air for 8 hours, and calcination was performed at 500 to 850 ° C. in an oxygen atmosphere for 24 hours. Thereafter, annealing was performed at 500 ° C. in an atmosphere of 1 atmosphere of oxygen for 12 hours. Table 6 shows the experimental results using the obtained lithium nickel manganese oxide.

Example 17
Lithium hydroxide hydrate, nickel hydroxide containing Co 30%, and manganese nitrate 20% were dissolved in pure water. The mixture was heated from room temperature to 300 ° C. with stirring, and dehydrated in air for 24 hours. Then, thermal decomposition was performed between 300 ° C. and 500 ° C. in the air for 8 hours, and calcination was performed at 500 to 850 ° C. in an oxygen atmosphere for 24 hours. Thereafter, annealing was performed at 500 ° C. in an atmosphere of 1 atmosphere of oxygen for 12 hours. Table 6 shows the experimental results using the obtained lithium nickel manganese oxide.

(Note) Although the N content d was higher than that of LiNi _0.4 Co _0.3 Mn _0.3 O _1.8 N _{0.2 in} Example 17, synthesis was impossible.

<Discussion>
Further, by introducing an element having a large negative valence instead of an oxygen atom, an effect of increasing the valence of Mn can be obtained, and an improvement in durability can be expected.

Comparative Example 7 and Examples 18 to 20 below are for LiNi _0.4 Co _0.3 Mn _0.3 O _2-d P _d (c-axis length of crystal (R3-m crystal structure) from the primary particle surface). Experiments were conducted by changing the value of the P content d of the composition up to 14.3%; the composition in the vicinity of the surface including the region having a depth of 5 times the c-axis length of the crystal from the primary particle surface. Specifically, the experiment was performed by partially replacing oxygen in the vicinity of the surface with P of -3valent ions.

Comparative Example 7
Lithium hydroxide hydrate, nickel hydroxide containing Co 30% and Mn 25%, and manganese phosphate 5% were dissolved in pure water. The mixture was heated from room temperature to 300 ° C. with stirring, and dehydrated in air for 24 hours. Then, thermal decomposition was performed between 300 ° C. and 500 ° C. in the air for 8 hours, and calcination was performed at 500 to 850 ° C. in an oxygen atmosphere for 24 hours. Thereafter, annealing was performed at 500 ° C. in an atmosphere of 1 atmosphere of oxygen for 12 hours. Table 7 shows the experimental results using the obtained lithium nickel manganese oxide.

Example 18
Lithium hydroxide hydrate, nickel hydroxide containing Co 30% and Mn 22%, and manganese phosphate 8% were dissolved in pure water. The mixture was heated from room temperature to 300 ° C. with stirring, and dehydrated in air for 24 hours. Then, thermal decomposition was performed between 300 ° C. and 500 ° C. in the air for 8 hours, and calcination was performed at 500 to 850 ° C. in an oxygen atmosphere for 24 hours. Thereafter, annealing was performed at 500 ° C. in an atmosphere of 1 atmosphere of oxygen for 12 hours. Table 7 shows the experimental results using the obtained lithium nickel manganese oxide.

Example 19
Lithium hydroxide hydrate, nickel hydroxide containing Co 30% and Mn 5%, and manganese phosphate 15% were dissolved in pure water. The mixture was heated from room temperature to 300 ° C. with stirring, and dehydrated in air for 24 hours. Then, thermal decomposition was performed between 300 ° C. and 500 ° C. in the air for 8 hours, and calcination was performed at 500 to 850 ° C. in an oxygen atmosphere for 24 hours. Thereafter, annealing was performed at 500 ° C. in an atmosphere of 1 atmosphere of oxygen for 12 hours. Table 7 shows the experimental results using the obtained lithium nickel manganese oxide.

Example 20
Lithium hydroxide hydrate, nickel hydroxide containing Co 30%, and manganese phosphate 20% were dissolved in pure water. The mixture was heated from room temperature to 300 ° C. with stirring, and dehydrated in air for 24 hours. Then, thermal decomposition was performed between 300 ° C. and 500 ° C. in the air for 8 hours, and calcination was performed at 500 to 850 ° C. in an oxygen atmosphere for 24 hours. Thereafter, annealing was performed at 500 ° C. in an atmosphere of 1 atmosphere of oxygen for 12 hours. Table 7 shows the experimental results using the obtained lithium nickel manganese oxide.

(Note) Although the content d of P was higher than that of LiNi _0.4 Co _0.3 Mn _0.3 O _1.8 P _{0.2 of} Example 20, synthesis was impossible. Specifically, the experiment was conducted by increasing the valence of Mn to +4 by deleting Mn in the region near the surface.

<Discussion>
The effect of increasing the valence of Mn can be obtained not only with nitrogen atoms but also with phosphorus atoms, and improvement in durability can be expected.

Comparative Example 8 and Examples 21 to 22 below are related to LiNi _0.4 Co _0.3 Mn _0.3-e O ₂ (about the c-axis length of the crystal (R3-m crystal structure) from the primary particle surface). Experiments were conducted by changing the value of the Mn content e of the composition up to 3%; the composition in the vicinity of the surface including the region having a depth of 5 times the c-axis length of the crystal from the primary particle surface.

Comparative Example 8
Lithium hydroxide hydrate and nickel hydroxide containing Co 30% and Mn 29% were dissolved in pure water. The mixture was heated from room temperature to 300 ° C. with stirring, and dehydrated in air for 24 hours. Then, thermal decomposition was performed between 300 ° C. and 500 ° C. in the air for 8 hours, and calcination was performed at 500 to 850 ° C. in an oxygen atmosphere for 24 hours. Thereafter, annealing was performed at 500 ° C. in an atmosphere of 2 atmospheres of oxygen for 12 hours. Table 8 shows the experimental results using the obtained lithium nickel manganese oxide.

Example 21
Lithium hydroxide hydrate and nickel hydroxide containing 30% Co and 28% Mn were dissolved in pure water. The mixture was heated from room temperature to 300 ° C. with stirring, and dehydrated in air for 24 hours. Then, thermal decomposition was performed between 300 ° C. and 500 ° C. in the air for 8 hours, and calcination was performed at 500 to 850 ° C. in an oxygen atmosphere for 24 hours. Thereafter, annealing was performed at 500 ° C. in an atmosphere of 2 atmospheres of oxygen for 12 hours. Table 8 shows the experimental results using the obtained lithium nickel manganese oxide.

Example 22
Lithium hydroxide hydrate and nickel hydroxide containing 30% Co and 27% Mn were dissolved in pure water. The mixture was heated from room temperature to 300 ° C. with stirring, and dehydrated in air for 24 hours. Then, thermal decomposition was performed between 300 ° C. and 500 ° C. in the air for 8 hours, and calcination was performed at 500 to 850 ° C. in an oxygen atmosphere for 24 hours. Thereafter, annealing was performed at 500 ° C. in an atmosphere of 2 atmospheres of oxygen for 12 hours. Table 8 shows the experimental results using the obtained lithium nickel manganese oxide.

(Note) It was impossible to synthesize a material having a Mn content e smaller than that of LiNi _0.4 Co _0.3 Mn _0.27 O _{2 in} Example 22 (a material in which Mn was lost).

<Discussion>
As another method of increasing the valence of Mn, it can be seen that the valence of the entire Mn can be increased by reducing the amount of Mn itself and creating defect sites, that is, zero-valent sites. As a result, durability is improved.

Claims (14)

  A lithium nickel manganese oxide having an average valence of Mn of 3.2 or more in a region having a depth of 5 times the c-axis length of the crystal from the primary particle surface is used as the positive electrode active material. Positive electrode material. A positive electrode material using a lithium nickel manganese oxide represented by the following general formula (I) as a positive electrode active material,
A positive electrode material characterized in that the average valence of Mn is 3.2 or more in a region having a depth five times the c-axis length of the crystal from the primary particle surface.

In the formula, M is at least one element selected from alkali metals (excluding lithium), alkaline earth metals (including beryllium and magnesium), transition metals (excluding nickel, manganese and cobalt), and aluminum. Indicates.
A represents at least one element selected from chalcogen elements (excluding oxygen), nitrogen, phosphorus, and halogen elements.
For x, y, z, a, b, c, d, in the initial state before charging and discharging,
0.5 <x ≦ 1.1,
0.3 ≦ y ≦ 0.7,
0.3 ≦ z ≦ 0.7,
0.0 ≦ a ≦ 0.4,
0.0 ≦ b ≦ 0.2,
1.8 ≦ c ≦ 2.4,
0.0 <= d <= 0.2 is shown.   The lithium nickel manganese oxide obtained by introducing excess oxygen into a region having a depth five times the c-axis length of the crystal from the primary particle surface is used as the positive electrode active material. The positive electrode material described in 1.   4. The positive electrode material according to claim 1, wherein the primary particle surface is oxygen-terminated at a ratio of 40% to 100%.   The range of 1.8 ≦ (cd) / (y + z + a + b) ≦ 2.4 in a region having a depth five times the c-axis length of the crystal from the primary particle surface The positive electrode material according to any one of the above.   The transition metal site is substituted with a +2 valent metal ion in a region having a depth of 5 times the c-axis length of the crystal from the primary particle surface. The positive electrode material described.   The positive electrode material according to claim 6, wherein the +2 valent metal ion is Mg and / or Zn.   8. The oxygen site in a region having a depth five times the c-axis length of the crystal from the primary particle surface is substituted with a trivalent nonmetallic ion. The positive electrode material described in 1.   The positive electrode material according to claim 8, wherein the nonvalent metal ion of −3 is N and / or P.   The site occupancy of the transition metal at the transition metal site is 90% or more and 98% or less in a region having a depth five times the c-axis length of the crystal from the primary particle surface. The positive electrode material according to any one of the above.   11. The positive electrode material according to claim 1, wherein the positive electrode material is the lithium nickel manganese oxide that is annealed in an atmosphere of oxygen at 1 atmosphere or more.   11. The positive electrode material according to claim 1, wherein the positive electrode material is the lithium nickel manganese oxide that is annealed in an atmosphere having an oxygen partial pressure of 0.1 atm or more.   13. The positive electrode material according to claim 1, wherein in the lithium nickel manganese oxide, a hydroxide containing nickel and manganese in primary particles is used as a raw material.   A non-aqueous electrolyte lithium ion battery comprising the positive electrode material according to claim 1.