JPH10247496A - Lithium battery and its active material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium secondary battery using a fresh active material capable of occluding lithium. SOLUTION: The structure of an active material is of a ramsdellite type shown by a formula Li1+ XTi2-2 XO4 (0<=X<=0.5). This active material includes TiO6 octahedral structures associated with each other by sharing edges to form an infinite double strand. These double strands are connected by adjacent strands and their apexes to form a three-dimensional skeleton, thereby constructing a vacant 2×1 tunnel capable of occluding lithium ions between adjacent double strands.

Description

DETAILED DESCRIPTION OF THE INVENTION

TECHNICAL FIELD The present invention relates to an active material for a lithium battery and a lithium battery.

2. Description of the Related Art So far, it has been found that only the spinel phase of titanium oxide is electrochemically active.
"J. Electrochem. Soc. 142, 143
1 (1995). " This material represented by the formula Li (Li _1/3 Ti _5/3 ) O ₄ exhibits a defective spinel type skeleton structure belonging to the space group Fd3m, and the unit cell parameter is a = 8.3.
5Å. This material was changed to _{Li 2 (Li 1/3 Ti 5/3)} 0 4 by insertion reaction without distortion, as a result, have found that exhibits a better repetition reversibility.

SUMMARY OF THE INVENTION An object of the present invention is to provide a novel active material capable of storing lithium and a lithium secondary battery using the same.

SUMMARY OF THE INVENTION The present invention relates to a compound of the formula Li _{1 + X} Ti _2-2X O ₄ (0 ≦ X ≦ 0.0) having a _ramsdellite structure.
5) An active material for a lithium secondary battery, characterized in that the lithium battery is used for one or both of the positive electrode and the negative electrode.

DETAILED DESCRIPTION OF THE INVENTION According to the present invention, Li _{1 + X} Ti
_{The substance represented by 2-2X} O ₄ (0 ≦ X ≦ 0.5) exhibits a _ramsdellite type structure, includes a TiO ₆ type octahedral structure, and the octahedral structures are bonded to each other by sharing edges. To form an infinite duplex. These duplexes form an empty (2 × 1) tunnel that can store lithium ions between adjacent duplexes by connecting adjacent chains with their vertices to form a three-dimensional skeleton. .

Next, the present invention will be described with reference to examples and drawings, but the present invention is not limited by these examples. Li _{1 + X} Ti _2-2X O ₄ (0 ≦ X ≦ 0.
5) was prepared by a two-step reaction involving Li ₄ Ti ₅ O ₁₂ , TiO ₂ , and metal Ti. In the first stage, Li ₂ CO ₃ and TiO ₂ are first mixed, and the mixture is mixed for 7 minutes.
By calcining at a temperature of 00 ° C. to remove CO ₂ , L
i ₄ Ti ₅ O ₁₂ was adjusted. Next, the resulting mixture was
The pellet was pelletized with 3 tons and fired again at 920 ° C. for 4 days to form a spinel type Li ₄ Ti ₅ O ₁₂ . Subsequently, spinel type LiTiO ₂ was prepared using Li ₄ Ti ₅ O _12, TiO ₂ and metal Ti. The mixture was pelletized and calcined at 840 ° C. under 5% hydrogen containing argon. Heating the resulting spinel phase LiTi ₂ O ₄ under vacuum and at a temperature in the range of 800 to 1000 ° C.,
A ramsdellite phase LiTi ₂ O ₄ was obtained. FIG. 1 shows the X-ray diffraction pattern of the material obtained according to the invention. The X-ray diffraction of LiTi ₂ O ₄ of the present invention shows that the unit cell parameters a = 5.03 ± 0.2 ° and b = 9.62 ± 0.2.
Å, and c = 2.95 ± 0.2Å, indicating that the crystal belongs to the orthorhombic ramsdellite structure of the space group. In this case, this structure can be considered as a tunnel type structure shown in FIG. 2 similar to the structure reported for γMnO ₂ . This structure includes a TiO ₆ -type octahedral structure, which bonds together by sharing edges to form an infinite duplex. These duplexes are
By connecting adjacent chains with their vertices to form a three-dimensional skeleton, an empty (2 × 1) tunnel is constructed between adjacent double chains that can reversibly occlude lithium ions. FIG. 3 shows the first cycle charge and discharge of the material of the present invention. In this test, LiClO ₄ was used as the electrolyte.
+ (2EC + 2DMC + DEC) at a current density of 0.25 mA / cm2 in a glass battery. The battery was composed of a negative electrode (87% of the active material of the present invention, 5%
(Carbon black, 8% PVDF), a lithium counter electrode, and a lithium reference electrode. First, the battery was charged to release lithium from the tunnel of the material of the present invention, and then discharged to occlude lithium ions in the tunnel. This battery exhibits a monotonic change in potential between 2 V and 1 V, suggesting that a uniform one-phase reaction occurs during charging and discharging. The intermediate potential is about 1.3 V and the capacity is over 180 mAh / g. This material had a 1.5 vol. As shown in the cyclic voltammogram curve of FIG.
It exhibits an oxidation-reduction peak even at a potential exceeding V.

The present invention provides a novel titanium oxide-based active material which can be used as a positive electrode or negative electrode active material of a lithium ion battery having a large capacity of up to 180 mAh / g. Since this substance has a ramsdellite type structure exhibiting a large 2 × 1 channel capable of reversibly storing lithium, it has good repetition reversibility and is useful as an active material of a lithium secondary battery having a high discharge rate. It is extremely expensive.

[Brief description of the drawings]

FIG. 1 is a view showing an X-ray diffraction pattern of an active material for a lithium battery of the present invention.

FIG. 2 is a diagram illustrating a tunnel type ramsdellite structure of an active material for a lithium battery according to the present invention.

FIG. 3 shows a first cycle charge / discharge curve of a battery comprising a lithium counter electrode, a lithium reference electrode, and an electrode made from the active material of the present invention. In this case, the active material was used as a negative electrode, first charged to occlude lithium ions, and then discharged to release lithium.

FIG. 4 is a view showing a cyclic voltammogram of the active material for a lithium battery of the present invention. (The scanning speed is 3mV
/ Min. )

Claims (7)

[Claims] _{1. The} compound of the formula Li _{1 + X} having a ramsdellite structure.
An active material for a lithium battery, represented by Ti _2-2X O ₄ (0 ≦ X ≦ 0.5). Wherein said ramsdellite structure with including Ti0 ₆ type octahedral structure, the Ti0 ₆ type octahedral structure forms an endless duplex bonded to each other by sharing the edges, further said Infinite The duplex is characterized by constructing a (2 × 1) tunnel through which lithium can enter between the adjacent infinite duplexes by connecting the adjacent chains at their vertices to form a three-dimensional skeleton. The active material for a lithium battery according to claim 1. 3. The ramsdellite phase has unit cell parameters of a = 5.03 ± 0.2 °, b = 9.62 ± 0.2 °,
2. The active material for a lithium battery according to claim 1, wherein c = 2.95 ± 0.2 °. 4. A positive electrode plate for a lithium secondary battery, comprising the active material for a lithium battery according to claim 1. 5. A negative electrode plate for a lithium secondary battery, comprising the active material for a lithium battery according to claim 1. 6. A lithium battery comprising: the positive electrode plate according to claim 4; an electrolyte; and a negative electrode active material of any one of Li, Li-alloy, Li _X SnO ₂ , and all kinds of carbon materials. . 7. The negative electrode plate according to claim 5, an electrolytic solution, and further comprising LiMn ₂ O ₄ , Li ₁ ± _X Mn _1.5 Ni _0.5 O ₄ , LiC
A lithium battery including any one of the positive electrode active materials of oO ₂ and LiNiO ₂ .