Polymer-coated active material and lithium secondary battery using the same

Abstract

Provided is a lithium ion secondary battery including a cathode that is capable of occluding and emitting lithium ions, and an anode that is capable of occluding and emitting the lithium ions. A polymer compound containing a polyether portion and a carboxylic acid bonding portion is bonded to an active material as shown with a structure I, a structure II, a structure III, and a structure IV.

Description

technical field

[0001] The present invention relates to a coated active material and a lithium secondary battery using the coated active material. Background technique

[0002] Lithium-ion batteries typified by lithium-ion batteries have high energy density and are attracting attention as batteries for electric vehicles and power storage. In particular, electric vehicles include zero-emission electric vehicles without an engine, hybrid electric vehicles equipped with both an engine and a secondary battery, and plug-in hybrid electric vehicles charged directly from a system power supply. In addition, application as a stationary power storage system that stores power and supplies power in an emergency after a power system is disconnected is also expected.

[0003] Lithium-ion batteries are required to have a large output and excellent durability for such various applications. That is, power supplies for mobile vehicles require output performance at a rate of 0.1 hour or more...

Examples

Embodiment 1

[0157] 〈Making of positive electrode〉

[0158] Utilize the positive electrode active material LiNi with an average particle size of 10 μm 1 / 3 mn 1 / 3 co 1 / 3 o 2, The following test was carried out on a positive electrode made of carbon black as a conductive agent and polyvinylidene fluoride (PVDF) as a binder. The weight composition of the positive electrode active material, the conductive agent, and the binder is set to 88:7:5. The area of ​​the electrode coated with the positive electrode slurry was set at 400 cm×5 cm, and the thickness of the mixture was set at 50 μm. In addition, the polymer compound of the present invention was not used for the positive electrode.

[0159] 〈Making of Negative Electrode〉

[0160] As the negative electrode active material, natural graphite with an average particle size of 15 μm is used, and as the polymer compound, [CH 3 -(OCH 2 CH 2 )nCO] 2 O (in structure I, X is CH 3 -, Y is a single bond, R is H, and n is 200 to 300) of carbox...

Embodiment 2

[0169] 〈Making of Negative Electrode〉

[0170] In Example 1, the n of the polymer compound was increased to 600 to 700, and the negative electrode was manufactured with the other conditions being the same as in Example 1.

[0171]

[0172] The initial capacity after initial aging was 1.8±0.1 Ah. The reason why the initial capacity is lower than in Example 1 is that the initial DC resistance is also increased by 20 to 30%. The capacity retention after 500 cycles at 50°C was 93±2%. The capacity retention rate was almost the same as the result of Example 1, but the initial capacity was low, so the capacity after 500 cycles also decreased.

Embodiment 3

[0174] 〈Making of Negative Electrode〉

[0175] In Example 1, the binder (styrene-butadiene rubber) used in the negative electrode was omitted, and a negative electrode with an increased amount of negative active material was produced instead. That is, the weight composition of natural graphite, polymer compound, binder, and tackifier was set to 96.5:2:0:1.5.

[0176] Other conditions were the same as in Example 1, and were produced and evaluated.

[0177]

[0178] The capacity retention rate (the ratio of the discharge capacity to the initial capacity of 2 ± 0.1 Ah) after 500 cycles was 91 ± 2%. The DC resistance increased by 160±10% from the initial value.

technical field

[0001] The present invention relates to a coated active material and a lithium secondary battery using the coated active material. Background technique

[0002] Lithium-ion batteries typified by lithium-ion batteries have high energy density and are attracting attention as batteries for electric vehicles and power storage. In particular, electric vehicles include zero-emission electric vehicles without an engine, hybrid electric vehicles equipped with both an engine and a secondary battery, and plug-in hybrid electric vehicles charged directly from a system power supply. In addition, application as a stationary power storage system that stores power and supplies power in an emergency after a power system is disconnected is also expected.

[0003] Lithium-ion batteries are required to have a large output and excellent durability for such various applications. That is, power supplies for mobile vehicles require output performance at a rate of 0.1 hour or more...

Examples

Embodiment 1

[0157] 〈Making of positive electrode〉

[0158] Utilize the positive electrode active material LiNi with an average particle size of 10 μm 1 / 3 mn 1 / 3 co 1 / 3 o 2, The following test was carried out on a positive electrode made of carbon black as a conductive agent and polyvinylidene fluoride (PVDF) as a binder. The weight composition of the positive electrode active material, the conductive agent, and the binder is set to 88:7:5. The area of ​​the electrode coated with the positive electrode slurry was set at 400 cm×5 cm, and the thickness of the mixture was set at 50 μm. In addition, the polymer compound of the present invention was not used for the positive electrode.

[0159] 〈Making of Negative Electrode〉

[0160] As the negative electrode active material, natural graphite with an average particle size of 15 μm is used, and as the polymer compound, [CH 3 -(OCH 2 CH 2 )nCO] 2 O (in structure I, X is CH 3 -, Y is a single bond, R is H, and n is 200 to 300) of carbox...

Embodiment 2

[0169] 〈Making of Negative Electrode〉

[0170] In Example 1, the n of the polymer compound was increased to 600 to 700, and the negative electrode was manufactured with the other conditions being the same as in Example 1.

[0171]

[0172] The initial capacity after initial aging was 1.8±0.1 Ah. The reason why the initial capacity is lower than in Example 1 is that the initial DC resistance is also increased by 20 to 30%. The capacity retention after 500 cycles at 50°C was 93±2%. The capacity retention rate was almost the same as the result of Example 1, but the initial capacity was low, so the capacity after 500 cycles also decreased.

Embodiment 3

[0174] 〈Making of Negative Electrode〉

[0175] In Example 1, the binder (styrene-butadiene rubber) used in the negative electrode was omitted, and a negative electrode with an increased amount of negative active material was produced instead. That is, the weight composition of natural graphite, polymer compound, binder, and tackifier was set to 96.5:2:0:1.5.

[0176] Other conditions were the same as in Example 1, and were produced and evaluated.

[0177]

[0178] The capacity retention rate (the ratio of the discharge capacity to the initial capacity of 2 ± 0.1 Ah) after 500 cycles was 91 ± 2%. The DC resistance increased by 160±10% from the initial value.

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