阅读说明：本技术 一种高容量锂离子电池负极活性材料、负极片及锂离子电池 (High-capacity lithium ion battery negative electrode active material, negative electrode plate and lithium ion battery ) 是由 王晕 赵东元 杨东 江文锋 郭佳 于 2021-08-24 设计创作，主要内容包括：本发明涉及一种高容量锂离子电池负极活性材料、负极片及锂离子电池,该负极活性材料含有硅单质或硅的化合物中的一种或多种的组合,且硅氧化物中含有镁元素,其中,镁含量占材料总重量的5％～40％。通过采用本发明的高比容量的负极材料,可以明显提高氧化亚硅的首次充放电效率,同时改善电池的循环性能。(The invention relates to a high-capacity lithium ion battery cathode active material, a cathode sheet and a lithium ion battery, wherein the cathode active material contains one or more of a silicon simple substance or a silicon compound, and silicon oxide contains magnesium, wherein the magnesium content accounts for 5-40% of the total weight of the material. By adopting the negative electrode material with high specific capacity, the first charge-discharge efficiency of the silicon monoxide can be obviously improved, and the cycle performance of the battery can be improved.)

1. The high-capacity lithium ion battery cathode active material is characterized by comprising one or more of a silicon simple substance or a silicon compound, wherein the silicon compound contains magnesium, and the total content of the magnesium accounts for 5-40% of the total weight.

2. The negative active material of claim 1, having a particle size of between 1 μm and 50 μm.

3. The negative active material of claim 1, wherein the weight ratio of oxygen in the silicon compound is less than 40%.

4. The negative active material of claim 1, wherein the silicon compound is a combination of silicon monoxide and magnesium silicide.

5. The negative active material of claim 1, further comprising a second active material selected from one or more of natural graphite, artificial graphite, mesocarbon microbeads, lithium titanate, silicon or silicon-carbon alloy, tin alloy, and active lithium metal.

6. A negative electrode sheet comprising the negative electrode active material according to any one of claims 1 to 5.

7. A negative electrode sheet according to claim 6, wherein the negative electrode active material is present in an amount of 5 to 100% by mass.

8. A negative electrode sheet according to claim 7, wherein the negative electrode active material is 93% by mass.

9. A lithium ion battery comprising the negative electrode sheet according to claim 6.

10. The lithium ion battery of claim 9, wherein the positive active material in the positive plate is any one or a combination of more of lithium cobaltate, lithium manganate, lithium iron phosphate, lithium iron manganese phosphate, lithium nickel cobalt manganese oxide, and nickel manganese spinel.

Technical Field

The invention belongs to the technical field of battery materials, and relates to a high-capacity lithium ion battery negative electrode material, a negative electrode plate and a lithium ion battery.

Background

Since lithium (Li) has the lowest reduction potential and the smallest ionic radius, in metal-ion batteries, lithiumThe primary rechargeable battery is considered to be the most promising battery system to achieve high mass/volume energy density and power density. Through research in the last two decades, lithium ion rechargeable batteries have been widely used in daily life, including electric tools, notebook computers, digital products, mobile phones, electric vehicles, unmanned aerial vehicles, and the like. In recent years, the dramatic growth in the market has required the development of commercial lithium ion batteries in the direction of lighter, thinner, and cheaper batteries. However, the LIBs commercially available today have reached their theoretical limits (250 wh/kg and 680 wh/L). Because the graphite-based negative electrode has lower theoretical specific capacity (372 mAh/g) and volume capacity (735 mAh/cm)³) Further increases in energy density of commercial LIBs are limited. Innovations in battery materials, including positive and negative electrodes, are then mainly aimed at increasing the energy density of the next generation lithium-based batteries and assembling lighter and thinner batteries to meet the needs of various applications.

In the high-capacity negative electrode, the silicon negative electrode is considered as the material with the largest development potential, the specific capacity of the silicon negative electrode is 4400mAh/g, and the specific capacity of the silicon negative electrode is almost 10 times of that of the graphite negative electrode commonly used in the current industry. However, the silicon negative electrode has a great problem in practical application that the capacity is too fast due to too much expansion. Therefore, researchers adopt the scheme of the silicon oxide, and the specific capacity is about 1500 mAh/g. The adoption of the silicon oxide can effectively reduce the expansion problem of the negative electrode and improve the cycle performance, however, the silicon oxide brings about another problem that the first charge-discharge efficiency is too low, only about 75 percent or even lower, which leads to that nearly 25 percent of lithium ions in the positive electrode active material are consumed, and the capacity loss of the battery is caused.

Therefore, it is necessary to provide a lithium ion battery cathode material and a lithium ion battery to solve the above problems in the prior art.

Disclosure of Invention

The invention aims to provide a high-capacity lithium ion battery negative electrode active material, a negative electrode sheet and a lithium ion battery.

The purpose of the invention can be realized by the following technical scheme:

one of the technical schemes of the invention provides a high-capacity lithium ion battery cathode active material, which contains one or more of simple substance silicon or compound silicon, and the compound silicon contains magnesium, wherein the content of the magnesium accounts for 5% -40% of the total weight of the cathode active material.

Further, the particle size of the negative active material is between 1 μm and 50 μm.

Further, the weight ratio of oxygen in the silicon compound is less than 40%.

Further, the silicon compound includes silicon monoxide and magnesium silicide.

Further, the negative active material can be doped with a second active material which is selected from one or more of natural graphite, artificial graphite, mesocarbon microbeads, lithium titanate, silicon or silicon-carbon alloy, tin alloy and active lithium metal.

The second technical scheme of the invention provides a negative electrode sheet, which comprises the negative electrode active material. In addition, the negative electrode sheet may further include necessary materials such as a solid electrolyte, a conductive agent, a negative electrode carrier, etc. for making the negative electrode sheet.

Further, the mass percentage of the negative electrode active material is 5% -100% (excluding the negative electrode carrier), and can be selected as 93%.

The third technical scheme of the invention provides a lithium ion battery, which comprises the negative plate.

Further, the positive active material in the positive plate of the lithium ion battery is any one or a combination of a plurality of lithium cobaltate, lithium manganate, lithium iron phosphate, lithium iron manganese phosphate, lithium nickel cobalt manganese oxide and nickel manganese spinel.

Compared with the prior art, the cathode material with high specific capacity can obviously improve the first charge-discharge efficiency of the silicon monoxide and improve the cycle performance of the battery.

Drawings

Fig. 1 is an SEM image and an EDS image of an anode active material according to the present invention;

fig. 2 is an XRD pattern of the negative active material of the present invention.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments. The present embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific operation process are given, but the scope of the present invention is not limited to the following embodiments.

In the following examples, unless otherwise specified, all the conventional commercially available raw materials or conventional processing techniques in the art are indicated.

Example 1:

MgSi is Mg₂Si and pure SiO are mixed (the mol ratio of the Si to the pure SiO is 1: 1), and the purity of the SiO is 99.99 percent.

After the materials are loaded into a melting crucible, starting vacuum pumping by using vacuum equipment, synchronously starting a power supply of an induction melting system and a heat preservation system to preheat, filling argon into a vacuum chamber of the equipment after the vacuum degree is pumped to be lower than 1Pa, then carrying out secondary vacuum pumping, stopping the vacuum system after the vacuum degree is also pumped to be lower than 1Pa, filling the argon to the atmospheric pressure, and then increasing the power to carry out melting.

The smelting temperature is 1300 ℃ and 1400 ℃, argon is used for atomization, and the atomization pressure is about 2.8 MPa. The temperature is kept for more than 30 minutes.

After the powder is atomized by argon gas and cooled in a wall-cooling vacuum cavity for more than two hours, a powder accumulation barrel is opened, the atomized powder is transferred to an atmosphere protection state for screening treatment, ultrasonic vacuum screening is used, strict atmosphere protection is carried out in the screening process, safety accidents are prevented, and finally the magnesium-silicon-containing negative electrode active material is obtained. Fig. 1 and 2 are SEM, EDS, XRD, and the like of the prepared magnesium-silicon-containing negative active material.

And (3) manufacturing a button cell, wherein the manufactured magnesium-silicon-containing negative electrode active material is subjected to button cell manufacturing:

the mixture ratio is as follows: the magnesium-silicon-containing negative active material accounts for 93 percent of the total material weight, 2 percent of PAALi and 5 percent of carbon black conductive agent SP.

The negative carrier is a porous copper foil.

The electrolytic liquid system is EC: EMC 3: 7, 1M LiPF₆，2％VC，2％FEC；

The counter electrode is a lithium metal sheet.

Comparative example 1

Silica is used as a negative active material.

The mixture ratio is as follows: the negative active material accounts for 93 percent of the total weight of the material, 2 percent of PAALi and 5 percent of carbon black conductive agent SP;

the negative carrier is a porous copper foil.

The electrolytic liquid system is EC: EMC 3: 7, 1M LiPF₆，2％VC，2％FEC。

The counter electrode is a lithium metal sheet.

The button cells prepared in example 1 and comparative example 1 were subjected to electrical property tests, as shown in table 1 below.

TABLE 1 comparison of the Electrical Properties of the examples and comparative examples

As can be seen from the table 1, the alloyed silicon oxide cathode after magnesium addition shows good electrical property, the specific capacity of the alloyed silicon oxide cathode is slightly reduced compared with that of pure silicon oxide, but the specific capacity of the alloyed silicon oxide cathode is far higher than that of a graphite cathode, the primary efficiency is greatly improved and reaches 82%; the cycle performance is also well improved, and the residual rate after 100 cycles is 75 percent.

The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.